CA2096977A1 - Scanning system for touch screen keyboards - Google Patents
Scanning system for touch screen keyboardsInfo
- Publication number
- CA2096977A1 CA2096977A1 CA002096977A CA2096977A CA2096977A1 CA 2096977 A1 CA2096977 A1 CA 2096977A1 CA 002096977 A CA002096977 A CA 002096977A CA 2096977 A CA2096977 A CA 2096977A CA 2096977 A1 CA2096977 A1 CA 2096977A1
- Authority
- CA
- Canada
- Prior art keywords
- light
- touch screen
- detector
- emitter
- emitters
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/042—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means
- G06F3/0421—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means by interrupting or reflecting a light beam, e.g. optical touch-screen
Abstract
SCANNING SYSTEM FOR TOUCH SCREEN KEYBOARDS
Abstract of the Disclosure A touch screen control system having a plurality of light emitter and detector pairs positioned on opposite sides of a touch screen display. The emitters and detectors are controlled by a microprocessor-based control system that energizes each of the light emitters in a pseudo-random manner. Before each light emitter is energized, the intensity of ambient light is measured by its associated light detector, and the ambient temperature is also measured by a temperature sensor. The intensity at which the light emitter is then energized is controlled as a function of ambient light and temperature. The control system generates a bitmap identifying beams from each light emitter to its associated detector that are obscured during each of several scans of the light emitter/detector pairs. In order to reject false receptions of light from an obscured light emitter beam, the control system processes the bitmap through a predetermined voting procedure. The control system is thus able to minimize the effect of interfering light sources on the performance of the touch screen.
Abstract of the Disclosure A touch screen control system having a plurality of light emitter and detector pairs positioned on opposite sides of a touch screen display. The emitters and detectors are controlled by a microprocessor-based control system that energizes each of the light emitters in a pseudo-random manner. Before each light emitter is energized, the intensity of ambient light is measured by its associated light detector, and the ambient temperature is also measured by a temperature sensor. The intensity at which the light emitter is then energized is controlled as a function of ambient light and temperature. The control system generates a bitmap identifying beams from each light emitter to its associated detector that are obscured during each of several scans of the light emitter/detector pairs. In order to reject false receptions of light from an obscured light emitter beam, the control system processes the bitmap through a predetermined voting procedure. The control system is thus able to minimize the effect of interfering light sources on the performance of the touch screen.
Description
2~9~977 Description SCANNING SYSTEM FOR TOUCH SCREEN KEYBOARDS
5 Field of the Invention This invention relates to touch screen keyboards, and more particular to a system for accurately scanning touch screen keyboards in the presence of a ambient light interference.
10 Backeround Art Touch screen keyboards are commonly used in a wide variety of fields. Touch screen keyboards are generally used with a cathode-ray tube (CRT) display in which rows of light emitters are positioned along two edges of the CRT display and rows of light detectors are positioned along 15 the remaining two edges of the CRT display opposite respective light ernitters. Designations corresponding to keyboard functions are then displayed on the CRT while each light emitter is selectively energized. As each light emitter is energized, the associated light detector is sampled to determine if light from the emitter is being blocked from reaching the 20 detector. A keyboard function is selected by touching the corresponding designation thereby blocking light from being coupled from a light emitter to the associated light detector. The position of a finger, pointer or the like is detected in the x and y axis by scanning the light ernitter/detector pairs along both the x and y axis.
Conventional touch screen keyboard systems must address several problems in order to perform satisfactorily. Typically, touch screen systems rely upon common emitter and detector amplifier electronics, requiring each emitter/detector pair to be matched to within a narrow margin so as to present urliforrn operating characteristics and thus reliable 30 beam break detection. Further, a light detector may mistake an ambient light source as emanating from its associated light emitter. Under these circumstances, the touch screen keyboard system will be unable to detect the selection of a key. The effects of arnbient light can be reduced by modulating the signal applied to the light emitters and then either filtering 35 or synchronously demodulating the signal from the associated light detector While these conventional techniques are usually adequate to reject most types of ambient light interference, they are often unable to reject 2~96977 - ;
interfering light generated by other touch screen keyboards or other frequency modulated devices operating in the vicinity since the interfering light will have the same or similar spectral content as the light generated by the light emitters. Also, the use of a filter to reject ambient light S interference can adversely effect the response time of the touch screen keyboard. A narrow band filter needed to adequately reject ambient light require a long excitation period (ring up time) before the ~lltered signal from the detector can respond to the modulated light generated by the associated light emitter. As a result, the use of narrow band filters 10 necessitates a relatively slow scanning speed.
Another problem associated with conventional touch screen displays is the varying sensitivity of the light detectors depending upon the intensity of ambient light. Most detectors used in touch screen keyboards are phototransistors. Phototransistors have the characteristic of variable 15 gain depending upon the level of ambient light. In order to compensate for these variations in detector gain, touch screen keyboard systerns generally overdrive the light emitters so that sufficient light will reach the phototransistors under worse case conditions. Also, the gain of conventional light detectors, as well as ligbt emitters, may also be affected 20 by temperature. Overdriving the emitters can produce serious problems when the detector gain is not in its worse case condition. Under these circumstances, sufficient light from the emitters may be reflected &om adjacent surfaces, such as the screen or detector/emitter mounting structure, that the light detector will be incapable of detecting a break in 25 the direct light path from the emitter to the associated detector. Under these circumstances, the touch screen will be unable to detect the selection of a keyboard function. In addition, variations in the electrical properties of the emitters or detectors, dust on the emitter and/or detector surfaces, and mounting misalignments may also effect the coupling of light from the light 30 emitter to the associated light detector.
There is therefore a need for a touch screen display scanning system that is capable of rejecting ambient light interference without overdriving the light emitters.
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~IQsure of the Invçntion It is an object of the invention to provide a scanning system for a touch screen keyboard that is insensitive to ambient light interference even from touch screen displays having identical scan patterns.
S It is another object of the invention to provide a touch screen display that does not require close matching of the electrical characteristics of components, such as light emitters and detectors, in order to provide uniform perfonnance.
It is another object of the invention to provide a touch screen display that compensates for the effect of changes in ambient light, temperature, component aging and environmental variations without overdriving the light emitters.
It is still another object of the invention to provide a touch screen keyboard that is less sensitive to reflections of emitted beams from 15 touch screen components.
It is a further object of the invention to provide a touch screen keyboard capable of being rapidly scanned.
It is a still further object of the invention to provide a touch screen keyboard having relatively high resolution.
These and other objects of the present invention are provided a touch screen keyboard system having a plurality of spaced apart light emitters positioned along at least one edge of a display panel and a plurality of spaced apart light detectors positioned along an edge of the display panel opposite the light emitters. The light ernitters are selectively energized and, 25 while each light emitter is energized, a corresponding light detector is sampled to determine whether light from the energized light emitter is being received by the enabled light detector. The light emitters are preferably energized in a pseudo-random manner to reduce the probability that a plurality of touch screen systems operating in close proximi~r will 30 operate in synchronism with each other and thus cause interference. In order to rninimize the effects of variations in ambient light and temperature, ambient light and temperature are measured and used to control the power applied to each light emitter so that the intensity of the light generated by the light emitters is a function of the intensity of arnbient35 light and temperature. In order to further reduce the sensitivity of the touch screen keyboard to interference, the touch screen keyboard is scanned a plurali~y of times before a touch screen key is considered to be ! ? ;
2~96977 selected. More specifically, during each scan, the locations of obscured light beams are detected and recorded in a ta~le. After a plurality of scans, the table is exarnined and the presence of a key selection is indicated by a light beam being obscured during a predetermined number or S predeterrnined percentage of scans. As a result, the touch screen keyboard is relatively insensitive to random noise sources.
Brief ~ ~tion of the I:)rawin~s Figure 1 is a mechanical schematic showing one embodiment 10 sf a touch screen keyboard.
Figure 2 is a system block diagram of the inventive touch screen keyboard system.
Figure 3 is a schematic of a high pass filter and amplifier circuit receiving signals generated by the light detectors and an ambient 15 bias circuit for providing a signal indicative of ambient light, both of which are used in the system of Figure 2.
Figure 4 is a schematic of a circuit used in the system of Figure 2 for energizing light emitters.
Figure 5 is a schematic of a digital one-shot used in the 20 system of Figure 2 to control the duration during which the light emitters are energized.
~ igure 6 is a flow chart of the main loop soft vare used in the system of Figure 2.
Figure 7 is a schematic of the software used in the system of 25 Figure 2 to scan the X-axis of the touch screen display.
Figure 8 is a flow chart of the software used to select each light emitter/detector pair during scanning.
Figure 9 is a flow chart of a subroutine used to sample the intensity of ambient light.
Figure 10 is a flow chart of the software used to calculate the desired intensity of light generated by the light emitters.
Figure 11 is a ~ow chart of the software for adjusting the intensity of light generated by the light emitters as a function of ambient temperature.
Figure 12 is a flow chart of the software used in the system of Figure 2 to illurninate a selected light en~itter and sample the corresponding light detector.
, ... . . . . . . .. ...
2~977 Figure 13 is a flow chart of the software used in the system of Figure 2 to scan the Y-axis of the touch screen display.
Figure 14 is a flow chart of the software used to determine the X-axis position of a selected key.
Figure 15 is a flow chart of the software used to determine the Y-a~as position of a selected key.
Best Mode for Canying Out the I~ventio~
A preferred embodiment of the inventive touch screen 10 keyboard is illustrated in schematic fonn in Figure 1. As with conventional touch screen displays, the preferred embodiment of the touch screen board 10 uses a rectangular CRT display screen 12 surrounded by a bezel 14. A
plurality of equally spaced light emitters 16 are mounted along the left edge bezel 14a. Similarly, a plurality of spaced apart light ernitters 16 are 15 mounted in the lower bezel 14b. Although the number of light em~tters 16 used will depend upon the desired resolution of the touch screen keyboard, in the preferred embodiment thirty-two light ernitters 16 are mounted in each bezel 14a,b. ;
Regardless of the number of light emitters 16 used~ a plurality 20 of light detectors 18 corresponding in number and position to the light emitters 16 on the opposite bezel are mounted in the bezels 14c,d along the remaining edges of the screen 12. As is well known in the art, the light emitters 16 are selectively energized during which time the light detectors 18 mounted in the corresponding positions i~ the opposite bezel are 25 individually sampled. If the light path from each light emitter 16 to the corresponding light detector 18 is not obscured, the light generated by the light emitter 16 generates a signal at the light detector 18. If, however, a finger, pointer or other object is placed on the screen 12 over a displayed key positioned along the light path, the emitted light is obscured and thus 30 does not reach the detector 18. By scanning along the x-axis using the light emitters 16 in the bezcl 14b and along the y-axis using the light emitters 16 in the bezel 14a, the exact position of the seleeted key can be determined.
In the preferred embodiment illustrated in Figure 1, the light detectors 18 are phototransistors. These phototransistors 18 used in the 35 preferred embodiment and in conventional touch screen keyboards have gain characteristics that are affected by ambient light and temperature. In order to minimize the effects of variations in ambient light and :- "
''' ' ' 2~977 temperature, the emitters 16 are typically driven at a level that is high enough to be sensed by the light detectors 18 under worst case, low gain conditions. However, when the light detectors 1~ are not operating under their worst case, low gain conditions, sufEicient light from the light emitters 5 16 can be reflected from adjacent surfaces to the associated light detector 18. Under these circumstances, the touch screen keyboard will fail to detect the selection of a key on the screen 12.
A preferred embodiment of a system for scanning the light emitters 16 and detectors 18 in the embodiment of Figure 1 is illustrated in 10 Figure 2. The system 30 includes a control subsystem 32 and an emitter/detector subsystem 34. The control subsystem 32 includes a microprocessor 36 of conventional design which, as is well known in the art, includes an internal timer circuit, read-only memory (ROM) for storing program instructions, digital input/output ports, analog input ports 15 connected to an internal analog-to-digital convertor, random access memory (RAM) and a serial input/output port. The microprocessor 36 receives a clock signal generated in a conventional manner to control the operation and timing of the rnicroprocessor 36. The microprocessor 36 operates in accordance with a program of instructions which are explained 20 in detail below.
The emitter/detector electronics 34 include an emitter column selector 40 implemented by a conventional multiplexer and discrete power transistors, as well as an emitter row selector 62 implemented by a conventional multiplexer. The emitter column selector 40 applies power to 25 the anode of a light emitting diode 16 designated by three bits of a six bit "Select" word when enabled by the "Emitter On-n signal. The six bit "Select"
word is received &om a digital I/O port of the microprocessor 36. The "Emitter On-N signal is generated by the digital one-shot 46.
An analog "Emitter Current Set" signal is generated by a 30 digital-to-analog converter 42 i~ the control subsystem 32. The digital-to-analog converter 42 is, in turn, controlled by 8 bits of data from digital I/O
ports of the microprocessor 36. The "Emitter Current Set" signal is directed by the ernitter row selector 62 to a voltage to current converter consisting of resistors 52 and 54 and transistors 50 and 56. As with the emitter column 35 selector 40 above, the emitter row selector 62 designates the voltage-to-current converter via the remaining three bits of the six bit "Select" word .
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2~6~77 when enabled by the "Emitter On-" signal. The six bit "Select" word is received from a digital I/O port of the rnicroprocessor 36.
When directed by the emitter row selector 62, the "Emitter Current Set" signal is applied to the base of a transistor 50 which is normally 5 biased at ground through resistor 52. The energized transistor 50 conducts current from the base of PNP transistor 56, causing a larger current to flow from the cathode of light emitting diode 16 to resistor 54. Subsequent current flow through resistor 54 generates a voltage which is substantially limited to the "Emitter Current Set" voltage.
Luminous intensity generated by light emitter 16 is directly proportional to the amount of current flow through the device. The '~rnitter Current Set" signal thus acts as a light emitter intensity control signal. The period of time that the light ernitter 16 is illuminated is controlled by the duration of the "Emitter On-" signal generated by the 15 digital one-shot 46.
Figure 2 shows a single light emitter 16 in control system 30.
However, in the preferred embodiment illustrated in Figure 1, 64 light emitters 16 are used. The 64 light emitters are organized as an eight-by-eight cross bar switch. Emitter column selector 40 relies upon the three low 20 order bits of the six bit "Select" word to designate one of eight possible columns of eight light emitter 16 anodes. Emitter row selector 62 relies ~- -upon the three high order bits of the six bit "Select" word to designate one of eight possible rows of eight light emitter 16 cathodes. Emitter row selector 62 and emitter column selector 40 are energized simultaneously via 25 "Emitter On-N signal. For any value of the six bit "Select" word, emitter rowselector 62 and emitter column selector 40 may intersect at only one light emitter 16.
Thus the six bit "Select" word indi~lidually selects one of sixty-four possible light emitters 16. "Emitter Current Set" controls light intensity 30 radiated from that individual light emitter 16 which is energized for a fixed short period of ~ne by the "Emitter On-" signal. Current applied to the light emitter 16 and its resulting light intensity are fully adjustable over a `
range which far exceeds the steady state current rating for the light emitter 16. The extremely short "Emitter On'n signal generated by the digital one-35 shot 46 and low device activation duty cycle allow such excess currents and their resulting increased light intensity without degradation to the light ~ -: ,-....
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~ ~. ' . ' , ' , ,' , ' 20~6977 emitter 16. This increased li~ht intensi~ provides a higher signal level than would be available using conventional touch techniques.
The collector of a correspond;ngly positioned phototransistor 18 is connected by a detector selector 60 to a low pass filter 62 and to a high 5 pass filter and amplifier 64. The same "Select" which designated light emitter 16 also designated its corresponding phototransistor 18.
Phototransistor 18, however, is enabled only by the "Select" word, and so is active before and after the light pulse of light emitter 16 occurs.
The collector of the phototransistor light detector 18 is 10 connected to one of several inputs to conventional multiplexer 70. The "Select" word and associated decoding cause the phototransistor light detector 18 to be applied to the output of multiplexer 70. Although a single multiplexer 70 connected to eight light detectors 18 is shown in Figure 3, it will be understood that a total of 64 light detectors 18 are used in the 15 preferred embodiment of Figure 1. For any value of the six bit "Select"
word, only one light detector 18 associated with its physical counterpart light emitter 16 is applied to the high pass filter and arnplifier 64 and low pass filter 62. Additional multiplexers 70 are selectively enabled via decoding of the three high order bits of the six bit "Select" word. The ~hree 20 low order bits are decoded directly by each multiplexer 70 via the A, B, C
input to the multiplexers 70.
The output of the multiplexer 70 is biased through resistor 72 by a supply voltage VCCA generated by a conventional voltage regulator 74. Voltage regulator 74 is, in turn, powered by the system power supply 25 which is filtered by capacitor 76. Voltage regulator 74 provides isolation and suppb stability for the high fixed gain amplifier and high pass filter 64 detailed in Figure 3. Clamping diode 78 is provided to protect voltage regulator 74 from damage caused by a polarity reversal due to a loss of the system power supply voltage.
Ambient light striking phototransistor light detector 18 causes a current to flow from "VCCA" through resistor 72 and multiplexer 70 into its collector. Voltage drop across resistor 72 provides a signal at the output of multiplexer 70. Berause of the low pass characteristics of the low pass filter 62, it does not respond to the pulse of light from the light emitter 16.
35 Instead, it provides a signal indicative of the level of ambient light as measured by the phototransistor 18. In this manner, the output of the low pass filter 62 will be a function of not only the level of ambient light, but also the gain of the phototransistor 18. The ambient light signal output by the low pass filter 62 is applied to an analog input port of the microprocessor 36.
The high frequency characteristics of the high pass filter and S amplifier 64 allow it to respond to the pulse of light from the light emitter 16. Accordingly, if the light path from the light emitter 16 to the light detector 18 is not obscured, a signal pulse will be generated at the output of the high pass filter and amplifier 64 each time the light emitter 16 is energized. The signal pulse is applied to an analog input port of the 10 rnicroprocessor 36 to allow the microprocessor 36 to determine that none of the keys positioned along the path f~om the light emitter 16 to the light detector 1~ is being selected.
Finally, the emitter/detector subsystem 34 includes a conventional temperature sensor 68 which outputs a signal indicative of 15 arnbient temperature. This ambient temperature signal is also applied to an analog input of the microprocessor 36 so that the microprocessor 36 can adjust the intensity control signal as a function of both temperature and ambient light. Once the microprocessor 36 detelmines the location of a selected key, it outputs this information to a host computer through a serial 20 I/O port so that the computer can identify and implement the selected key function.
The high pass filter and amplifier 64 forming part of the emitter/detector subsystem 34, is illustrated in greater detail in Figure 3.
The collector of the phototransistor light detector 18 is applied to one of 25 several inputs to conventional multiplexer 70. When the multiplexer 70 is enabled by the six bit "Select" word, it applies one of the inputs to its output.
The output of the multiplexer 70 is generally a signal consisting of a direct current (DC) offset indicative of ambient light striking the phototransistor.
A pulse, corresponding to an energized light emitter, is present only when 30 light detector 18 is not blocked by an object from receiving its associated light emitter output. Although a single multiplexer 70 cormected to eight light detectors 18 is shown in Figure 3, it will be understood that a total of eight multiplexers 70 are provided for the 64 light detectors 18 used in the preferred embodiment of Figure 1. These additional multiplexers 70 are 35 selectively enabled by higher order bits of the eight bit "Select" word from the multiplexer which are applied to the A,B,C inpu~ of the multiplexers 70.
2~6377 The output of the multiplexer 70 is biased through resistor 72 by a supply voltage VCCA generated by a conventional voltage regulator 74. The voltage regulator 74 is, in turn, powered by the system power supply which is filtered by capacitor 76. Clarnping diode 78 is provided to 5 prevent the power supply voltage VCCA from being driven by transients significantly above the system power supply voltage. When the multiplexer 70 connects the output to one of the inputs, the associated phototransistor 18 is driven by the voltage regulator 74 through resistor 72.
The signal at the output of the multiplexer 70 is applied to 10 two distinct circuits. The first of these circuits is an ambient light bias circuit 80, which consists of an operational amplifier 82 having a surnming resistor 84, and a low pass filter formed by resistor 86 and capacitor 88 connected in parallel to provide negative feedback. Capacitor 90 also limits the high frequency response of the amplifier 82. The amplifier 82 is 15 powered through resistor 92, and this power supply voltage is low pass filtered by capacitor 94. The noninverting input of the operation amplifier 82 is biased to a predetermined value by voltage divider resistors 96, 98.
The bias level set by the voltage divider resistors 96, 98, in combination with the gain of the amplifier 82 set by the ratio of feedback resistor 86 to 20 summing resistor 84, scales the voltage indicative of ambient light to within a predetermined operating range. Also, as explained above, the low pass characteristics of the amplifier 82 provided by capacitors 88, 90 prevents the arnplifier 82 from responding to light pulses from the associated light emitter 16 so that the output of the amplifier 82 is indicative of ambient 25 light.
The output of the multiplexer 70 is also applied to the high pass filter and arnplifier 64 illustrated in Figure 2. As illustrated in Figure 3, the high pass filter and asnplifier 64 includes three amplifjring transistors100, 102, 104 having respective load resistors 106, 108, 110. The bases of 30 the transistors 100, 102, 104 are each biased by respective voltage divider resistors, 112, 114. Finally, the signal pulses are coupled to the base of each transistor 100 104 by a respective coupling capacitor 118. Power is supplied to the transistors 100 lQ4 through resistor 120 which, in combination with capacitor 122 low pass filters the power supply voltage. A signal pulse 35 corresponding to the pulse of light received by the phototransistor 18 is thus output from the collector of transistor 104 through resistor 126. This pulse 2 ~ 7 7 is applied to an analog input of the microprocessor 36 as illustrated in Figure 2.
One of the advantages of the circuitry used irl the high pass filter and amplifier 64 is that requires only a single polarity of power supply.S It also provides low noise and high gain with little cost and good insensitivity to temperature variations. In contrast, high pass filter arnplifiers using operational amplifiers or operating open loop have poor pulse mode responses due to their limited slew rate at high gains.
Additionally, judiclous selection of passive component values allow 18 dB
10 per octave low pass rejection of the principal contarnination sources below 300 Hz. Although high gain, the amplifier is desi~ed with an order of magnitude less sensitivity than are found in common touch screen keyboards. This takes advantage of the much higher luminous signal strength provided by high energy light emitter 16 pulse, and thus ambient 15 light noise is further reduced in the system. High luminous signal strength and low noise contarnination are fundamental improvements provided by the invention. Further, the amplifier provides a stable, fixed high gain with low group delay which allows the light emitter 16 pulse period to remain short.
Tbis technique provides a significant advantage over techniques which use a variable gain amplifier and ~xed output emitter. In the latter technique, when an emitter/detector pair require additional signal strength to compensate for component rariation, both signal and noise are increased via variable gain amplifier. Thus the signal to noise 25 ratio is not improved. Using the invention technique described herein, signal is increased without an accompanying increase in ambient noise, improving signal to noise in the system.
The digital-to-analog converter 42 (Figure 2), emitter column selector 40, emitter row selector 62, and the remaining emitter drive 30 components 5~56 are shown in combination with light emitter 16 in Figure 4. The digital-to-analog converter 42 is a conventional integrated circuit digital-to-analog converter having an 8-bit input for receiving a digital word indicative of the analog voltage as weil as chip enable and chip select inputs. All of the inputs of the digital-to-analog converter 140 are 35 generated by the microprocessor 36 (Figure 2). The output of the digital-to-analog converter 140 is an analog voltage corresponding to the value designated by the digital word. This analog voltage is low pass filtered by 2 ~ 7 ~
capacitor 144 and applied to the common terrninal of the multiplexer 44, as explained above. As also mentioned above, the "Emitter On" output from the digital one-shot 46 (Figure 2) controls the duration that the "Ernitter Current Set" analog voltage from the D/A converter 140 causes current to 5 flow through the selected light emitter 16.
The emitter column selector 40 includes a conventional multiplexer 150 to which 3 bits of the six bit "Select" word are applied. The multiplexer 150 provides a path to ground through resistor lS2 to one of eight I/O outputs selected by the 3-bit word. An inhibit input is enabled by 10 the "Ernitter On-" signal. Darlington transistors 162, 164 are normally biased off by resistor 168. When "Emitter On-" is asserted, current flows out of the base of transistor 162, through the multiplexer 150 and resistor to ground. The transistor Darlington pair 162, 164 becomes a saturated switch, applying essentially "VCC' to the anode of light emitter 16.
15 Simultaneously, when the inhibit input of conventional multiplexer 44 is enabled via "Emitter On-" signal, current is conducted from the cathode of light emitter 16 via the voltage-to-current converter consisting of transistors 50, 56 and resistors 52, 54. l~e voltage-to-current converter is energized via the conventional multiplexer 44 which forms the emittér row selector 62 20 as previously described.
The supply voltage outputs from the multiplexer 150 are applied to a respective Darlington pair of transistors 162, 164 to switch the power supply voltage to the anode of light ernitter 16. The transistors 162, 164 are biased off through resistor 168.
The remaining circuitry shown in Figure 2 is the digital one-shot 46 which generates the "Emitter On-" signal for the emitter column selector 40, en~itter row detector 61, and detector selector 60. The digital one-shot 46, which is illustrated in Figure 5, uses a conventional integrated circuit counter 160 having a reset input receiving a pulse enable signal from the microprocessor 36 and a clock signal output by a NOR-gate 162. The NOR-gate 162 in turn receives a two mH~ clock from the microprocessor 36 and the Q7 output of the counter 160. When the terminal count of the counter 16Q is reached, the logic "1" signal at the Q7 output disables the NOR-gate 162 to prevent the clock signal from reaching the clock input of 35 the counter 160. Under these circumstances, the Q7 output of the counter 160 remains at logic l-1" thereby causing NOR-gate 164 to output a logic "0".
The output of NOR-gate 164 is applied to a third NOR-gate 166 acting as - . . . . . . ~ . . . ; , ~ ; - . . : . . .. --2~9 ~7 an inverter through capacitor 168. The input to NORgate 166 is biased low through resistor 170, and it is clamped from being driven substantially below zero volts by diode 172. The digital one-shot circuit is designed to require a pair of actions at the "Pulse Enable" input from the 5 microprocessor 36 in order to activate an emitter light pulse. Fist, "Pulse Enable" goes high, causing a reset of counter 160 and thereby causing the output of Q7 to go low. The output of NOR-gate 164 remains low, however, because the "Pulse Enable" input is now high. Further, counter 160 is held in reset and will not count until "Pulse Enable" is set low. NOR-10 gate 162, however, is now enabled, allo~,ving the 2 MHz clock to passthrough to the clock input of counter 160. The high to low transition of "Pulse Enable" releases the counter 160 and causes a high output from NOR-gate 164 to couple through capacitor 168 to produce a negative going pulse at the NOR-gate 166. When the counter 160 once again reaches the 15 terminal count, the NORgate 162 is disabled as explained above, and the output of the NOR-gate 166 is driven high through NOR-gate 164 and capacitor 168. The negative going pulse at the output of the NORgate 166 controls the duration that the light emitters 16 are illuminated as explained above. Capacitor 168 is provided to insure that the light emitters 16 are not 20 energized indefinitely if, for some reason, the counter 160 or its associated circuitry malfunctions so that the terminal count is not reached. Under these circumstances, capacitor 168 will discharge through resistor 170 thereby once again causing the output of NORgate 166 to go high.
As mentioned above, the microprocessor 36 (Figure 2) 25 operates in accordance with a program of ins~ructions. Flow charts showing this prograrn are illustrated in Figures 6-15. With reference to Figure 6, the main loop program is entered at 200 and standard initialization functions, such as setting up I/O ports as either inputs or outputs, clearing registers, etc., are performed at 202. The operation of the emitter and detector 30 electronics are then verified at 204 by sequentially illuminating each emitter and detecting receipt of the emitted light at the associated detector. AD
internal counter in the microprocessor 36 that records the number of keyboard scans is then reset at 206. The main loop program calls a "SCAN
X-AXIS" subroutine at 208 to scan the light ernitters and detectors 35 positioned along the lower and upper edges, respectively, of the screen 12 (Figure 1). After all of the x-axis emitters/detectors have been scanned, the program checks at 210 to determine if a predetermined number, e.g., 3, 2 ~ 9 7 7 scans of the x-axis have been completed. If not, the scan counter is incremented by one at 212 and the "SCAN X-AXIS" subroutine is once again called at 208.
After a predetermined number of x-axis scans have been 5 completed the main loop branches to 214 where a "CHK X" subroutine is called. As explained in greater deta~l below, the "CHK X" subroutine examines a record of interrupted light bearns from the emitters to associated detectors along the x-ax~s to determine if the size of the interrupting object is consistent with a finger or other pointer. The purpose 10 of the "CHK X" subroutine is to reject interrupting targets that are either too big (such as interruptions caused by cleaning the screen 12 with a cloth) or too small (such as i~terruptions produced by a fly). If the subroutine determines at 214 that the interrupting object is the proper size, it sets a "VAI~D X TARGET FLAG" to 1.
lS The main loop program then progresses to 216 where the VAIID TARGET Fl.AG is checked. With the VALID TARGET FLAG is found at 216 to be set to 1, tbe program branches through path 218 to scan the y-axis emitters/detectors as explained below. However, if the VALID
TARGET FIAG is not set to 1, the program branches to æo to detennine 20 if the VALID TARGET FLAG had previously been set to 1 thus indicating that a finger or pointer had been removed from the screen 12. If not, the prograrn waits for a timeout at 222 before returning through 224 to reset the scan counter at 206 and follow the steps described above.
If the main loop program has determined at 216 that the 25 VALID TARGET Fl AG is not set to 1 but it determines at 220 that the flag was previously set to 1, the prograrn branches to 230 where a REPEAT
MODE FL~G is checked. The REPEAT MO~E FLAG is set to 1 by a host computer if it is desired to allow a keyboard function to be continuously designated such as, for example, a constantly depressed 30 spacebar key. If the REPEAT MODE FLAG is not set to 1, thus indicating that the repeat mode is not active, the program branches to 222 to wait for a timeout before returning through 224. If the repeat mode is active, a "REPORT KEY GONE" subroutine is called at 234 to prov~de an indication that the selected key is no longer being selec~ed.
After a valid target has been detected at 216, the main loop program proceeds via 218 to scan the y-axis emitter/detectors as explained above. A y-axis scan counter internal to the n~icroprocessor 36 is reset at 20~9~7 240 in the same manner that the x~ is scan counter is reset at 208.
Thereafter, the y-axis emitter/detectors are scanned at steps 242, 244, 246 in the same manner that the x-axis emitter/detectors are scarmed in steps 208, 21Q 212, respectively. Similarly, after the y-axis has been scanned a S predeterrnined number of times as the term the 244, a "CHK Y" subroutine is called at 250 which deterrnines if the obscuring target is the proper size inthe same mar~ner that the "CHK X" subroutine called at 214 performs that function. The main loop program then determines at 252 if a valid y-axis target is present. If so, the program branches to 254 to check the REPEAT
10 MODE FLAG. If the repeat mode is active, the selected key is reported at 256. Otherwise, the program branches to 258 to determine if the selected key has already been reported. If not, the key is first reported at 256. After the selected key is reported at 256, the PREVIOUS TARGET FLAG is set to 1 at 260 before waiting for a timeout at 262 and eventual return through 15 224 as explained above. If the ma~n program determines at 258 that the selected key has already been reported, the PREVIOUS TARGET FI AG
is set to 1 at 260 without once again reporting the presence of the selected key.
Returning to step 252, if the program determines that a valid 20 "y" target has not been selected, the program branches to 270 to deterrnine if the target was previously selected. If not, the program waits at 262 for a timeout before returning. Otherwise, the prograrn checks at 272 to determine if the repeat mode is active. If the repeat mode is active, the program reports the fact that the selected key is no longer being selected at 274 before waiting for a timeout at 262. If the repeat mode is not found to be active at 272, there is no need to report the absence of the selected key since only the initial actuation of the selected key need be reported.
Therefore, the program branches directly from 272 to 262 to await a timeout.
As mentioned above, the first subroutine that is called by the main loop program of Figure 6 is the "SCAN X-AXIS" subroutine which is called at 208. The SCAN X-AXIS subroutine is illustrated in detail on Figure 7. The SCAN X-A~S subroutine is entered at 300 and a "GET IR
PAIR" subroutine is called at 302 to energize a specific light emitter and 35 enable a specific light detector. With reference to Figure 8, the "GET IR
PAIR" subroutine 302 is entered at 310 and a system clock counter internal to the microprocessor 36 is sampled at 312. The low order bits of the 2~6977 counter are then masked off at 314 so that only the low order bits are exa~uned. This acts as a pseudo-random number generator for selecting IR
pair to be activated. The low order bits are used to identify specific emitter/detector pair. The subroutine deterrnines at 316 whether the 5 emitter/detector pair corresponding to the low order bits have previously been sampled during a given scan. If not, the low order bits are stored in a bitmap at 318 to designate that the corresponding emitter/detector is being sampled. Appropriate outputs from the rnicroprocessor 36 are then enabled at 320 as described during the explanation of the hardware thereby 10 energizing the selected emitter and enabling the selected light detector.
The program then returns to the "SCAN X-A~S" subroutine 208 shown in Figure 7 via 322. If the "GET IR PAIR" subroutine determines at 316 that a emitter/detector pair corresponding to low order address bits have previously been sampled, the low order address is incremented at 324 and 15 the bitmap is then examined at 326 to determ~ne if all of the emitter/detector pairs have been sampled. If not, the prograrn returns to 316 to repeat the above-described procedure. After all of the ernitter/detectors have been sampled, the subroutine returns to the calling subroutine through 322. ~ -Returning, now, to Figure 7, after the "GET IR PAIR"
subroutine has been executed at 302, the subroutine waits a predeterrnined period for the electronic circuitry to stabilize at 330. The subroutine then calls a "GET BL~S" subroutine at 332. The "GET BL4S" subroutine is illustrated in detail in Figure 9. The "GET BL~S" subroutine 332 is entered 25 at 340 and the analog-to-digital converter internal to the rnicroprocessor 36is enabled at 342. The program then waits for a predetennined period at 344 to allow the analog-to-digital converter to perform its acquisition process, and the output of the analog-t~digital converter is saved at 346 before returning through 348. The value saved at 346 is indicative of the 30 intensity of arnbient light as measured by the selected light detector.
Returning once again to Figure 7, the "SCAN X-A~S"
subroutine 208 then calls a "CALC POWER" subroutine at 3S0. The "CALC POWER" subroutine 350 is shown in detail in Figure 10. The "CALC POWER" subroutine is entered at 360 and a minimum value of 35 emitter intensity is designated at 362 depending upon the measured value of ambient light. The subroutine then determines at 364 whether the ambient light is below a minimum threshold. If so, a minimum intensity default .. : : . . . . .. - ....... ....... .. . . .. .
2 ~
value is selected and the program branches to 366 where it returns to the "GET X-AXIS" subroutine 208 illustrated in Figure 7. If the ambient light is below a predetermined minimum value, the subroutine checks if it is above a predetermined maximum value at 368. If so~ a maximum power 5 level is set at 370 before returning through 366. If the intensity of the ambient light is somewhere between a predetermined minimum and ma~amum value, the subroutine branches to 370 where an intensity value corresponding to ambient light is selected in a lookup table. As is well known in the art, a lookup table contains a record of the optimum light 10 ernitter intensity for each value of ambient light and it will generally following a non-linear relationship. Once the light intensity is selected at -37Q the program branches to 372 to multiple the normalized power value by the value of arnbient light as a function of its relationship between the minimum and maximum values. This value is then added to the minimum 15 intensity value at 374 and the result is saved as the desired value at 376.
After the desired ernitter intensity is calculated, the subroutine once again returns to the "SCAN X-AXIS" subroutine 208 in Figure 7. An "ADJ-TEMP" subroutine is then called at 38Q The "ADJ-TEMP ' subroutine 380, which is illustrated in Figure 11, is entered at 390 -20 and the output of the temperature transducer 68 (Figure 2) is sampled at 392. The difference between the current ambient temperature and the ambient temperature during calibration is then determined at 394. If the current temperature at 396 to be the same at the ambient temperature during calibration, the subroutine returns to the "SCAN X-A~S"
25 subroutine 208 via 398. Othen~ise, the difference in temperature is multiplied by an appropriate scale factor at 400 and the emitter intensity--value calculated at 350 is multiplied by the scale factor at 402. In this manner, the "ADJTEMPN subroutine 380 adjusts the desired emitter ;j -intensity as a function of ambient temperature.
Retuming, once again, to Figure 7, the "SCAN X-AXIS"
subroutine then sets the power level corresponding to the ernitter intensity at 410 by applying a byte to digital-to-analog converter 42 (Figure 2) indicating the desired power level. A "GET IR" subroutine is then called at 420 to trigger the one-shot 46 (Figure 2) and apply appropriate bits to the 35 emitter selector 40 and detector selector 60.
The "GET IR" subroutine 410 is illustrated in detail in Figure 12. The "get IR" subroutine is entered at 450 and the digital one-shot 46 ' ," ";, ~ " , - ,~ "
(Figure 2) is then triggered by a pulse at the output of the microprocessor 36 at 452. The program delays an appropriate period at 454, such as 16 microseconds, to allow the detector circuitry to stabilize before sampling the output of the high pass filter 64 at 456 to determine whether the emitted S ligbt is being received at the associated detector. . The program then returns to the "SCAN X-A~S" subroutine through 458.
After the "GET IR" subroutine has been completed, the results of the test are then saved in a bitmap at 4æ, as illustrated in Figure 7. The bitrnap is a table having a location for each emitter/detector pair 10 for each scan of the keyboard. Thus, a touch screen keyboard having 64 emitter/detector pairs along the x-axis will have 192 memory locations if the keyboard is to be scanned three times. The subroutine determines at 324 if all of the emitter/detector pairs have been scanned. If not, the subroutine returns to 302 to once again perform the "GET IR PAIR"
15 subroutine. After all of the emitter/detector pairs have been scanned, the subroutine returns through 426 to the main loop prograrn at 210 (Figure 6).
As explained above with respect to the main loop program, after the "SCAN X-AXIS" subroutine is performed to identify the "x"
location of an obscured emitter/detector pair, the main loop prograrn calls 20 at 242 a "SCAN Y-AXIS" subroutiDe. The "SCAN Y-A~S" subroutine, which is illustrated in Figure 13, calls the same subroutines and performs essentially the same function as the "check y" subroutine. Therefore, in the interest of brevity, it will not be separately explained but instead the flow chart has been assigned the sarne reference numerals as the corresponding 2S functions of the "SCAN X-AXIS" subroutine of Figure 7.
The final subroutine executed by the main loop program of Figure 6 is the "CHK X" subroutine 214 which is illustrated in Figure 14.
The "CHK X" subroutine 214 is entered at 480. It will be recalled that the "SCAN X" subroutine saves a bitmap of obscured light beams for several 30 scans at 422. This bitmap is examined at 482 to identi~y light emitters/lightdetector pairs that are to be considered as obscured using an appropriate voting format. For exarnple, if the x-axis light emitters/detectors are scanned three times, the bitmap created during the "SCAN X" subroutine will contain three bits for each light emitter/detector pair. The subroutine 35 identifies a light emitter/detector pair as being selected if the light beam from the emitter to the detector has been obscured in any two of the three scans. Consequently, if during one of the scans light from an emitter has 2 ~ ~ 6 9 l' 7 reflected on to the associated detector, that reflection will be ignored and a valid key selection will be recorded.
After the obscured beams have been identified at 482, the subroutine detennines the right-most and left-most obscured beams at 488 5 and then calculates the target size at 490 based upon the number of beams obscured and the spacing between the beams. The calculated target size is then compared to a predeterm~ned mirumum target size at 492. If the target size is too small, such as a single beam is obscured, then an identifying flag is set at 494 and the subroutine returns to the main loop 10 program through 496. If the target is not too small, the subroutine branches to 498 where the calculated target size is compared to a predetermined large value. If the target is too large, such as would occur if the screen 12 (Figure 1) was being cleaned by a cloth, an appropriate flag is set at 500 before returning through 496.
With reference to the main loop program of Figure 6, after the "CHK X" subroutine in 214 is executed, the progra n eventually progresses to a "CHKY" subroutine which is executed at 252. The "CHK Y" subroutine 250 is illustrated in Figure 15. The "CHK Y"
subroutine is identical to the "CHK X" subroutine, except that it performs 20 its function for the y-axis light emitter/detectors rather than the x-axis light emitter/detectors. Therefore, in the interest of brevity, it has been given the same reference numerals for the corresponding functions.
The inventive touch screen keyboard is thus insensitive to ambient light interference, even from touch screen displays having identical 2S scan patterns, and it is insensitive to reflections of emitted beams from touch screen components. It also compensates for the effect of changes in ambient light, temperature, component aging and environrnental variations without overdriving the light emitters. Furthermore, the im~entive touch screen keyboard does not require close matching of the electrical 30 characteristics of electrical components in order to provide uniform performance.
5 Field of the Invention This invention relates to touch screen keyboards, and more particular to a system for accurately scanning touch screen keyboards in the presence of a ambient light interference.
10 Backeround Art Touch screen keyboards are commonly used in a wide variety of fields. Touch screen keyboards are generally used with a cathode-ray tube (CRT) display in which rows of light emitters are positioned along two edges of the CRT display and rows of light detectors are positioned along 15 the remaining two edges of the CRT display opposite respective light ernitters. Designations corresponding to keyboard functions are then displayed on the CRT while each light emitter is selectively energized. As each light emitter is energized, the associated light detector is sampled to determine if light from the emitter is being blocked from reaching the 20 detector. A keyboard function is selected by touching the corresponding designation thereby blocking light from being coupled from a light emitter to the associated light detector. The position of a finger, pointer or the like is detected in the x and y axis by scanning the light ernitter/detector pairs along both the x and y axis.
Conventional touch screen keyboard systems must address several problems in order to perform satisfactorily. Typically, touch screen systems rely upon common emitter and detector amplifier electronics, requiring each emitter/detector pair to be matched to within a narrow margin so as to present urliforrn operating characteristics and thus reliable 30 beam break detection. Further, a light detector may mistake an ambient light source as emanating from its associated light emitter. Under these circumstances, the touch screen keyboard system will be unable to detect the selection of a key. The effects of arnbient light can be reduced by modulating the signal applied to the light emitters and then either filtering 35 or synchronously demodulating the signal from the associated light detector While these conventional techniques are usually adequate to reject most types of ambient light interference, they are often unable to reject 2~96977 - ;
interfering light generated by other touch screen keyboards or other frequency modulated devices operating in the vicinity since the interfering light will have the same or similar spectral content as the light generated by the light emitters. Also, the use of a filter to reject ambient light S interference can adversely effect the response time of the touch screen keyboard. A narrow band filter needed to adequately reject ambient light require a long excitation period (ring up time) before the ~lltered signal from the detector can respond to the modulated light generated by the associated light emitter. As a result, the use of narrow band filters 10 necessitates a relatively slow scanning speed.
Another problem associated with conventional touch screen displays is the varying sensitivity of the light detectors depending upon the intensity of ambient light. Most detectors used in touch screen keyboards are phototransistors. Phototransistors have the characteristic of variable 15 gain depending upon the level of ambient light. In order to compensate for these variations in detector gain, touch screen keyboard systerns generally overdrive the light emitters so that sufficient light will reach the phototransistors under worse case conditions. Also, the gain of conventional light detectors, as well as ligbt emitters, may also be affected 20 by temperature. Overdriving the emitters can produce serious problems when the detector gain is not in its worse case condition. Under these circumstances, sufficient light from the emitters may be reflected &om adjacent surfaces, such as the screen or detector/emitter mounting structure, that the light detector will be incapable of detecting a break in 25 the direct light path from the emitter to the associated detector. Under these circumstances, the touch screen will be unable to detect the selection of a keyboard function. In addition, variations in the electrical properties of the emitters or detectors, dust on the emitter and/or detector surfaces, and mounting misalignments may also effect the coupling of light from the light 30 emitter to the associated light detector.
There is therefore a need for a touch screen display scanning system that is capable of rejecting ambient light interference without overdriving the light emitters.
,,; . , . ., ; i; , . : , , . . . -~, ,- . . ~ . , .. " : , : , . . .
2 ~ 7 ~
~IQsure of the Invçntion It is an object of the invention to provide a scanning system for a touch screen keyboard that is insensitive to ambient light interference even from touch screen displays having identical scan patterns.
S It is another object of the invention to provide a touch screen display that does not require close matching of the electrical characteristics of components, such as light emitters and detectors, in order to provide uniform perfonnance.
It is another object of the invention to provide a touch screen display that compensates for the effect of changes in ambient light, temperature, component aging and environmental variations without overdriving the light emitters.
It is still another object of the invention to provide a touch screen keyboard that is less sensitive to reflections of emitted beams from 15 touch screen components.
It is a further object of the invention to provide a touch screen keyboard capable of being rapidly scanned.
It is a still further object of the invention to provide a touch screen keyboard having relatively high resolution.
These and other objects of the present invention are provided a touch screen keyboard system having a plurality of spaced apart light emitters positioned along at least one edge of a display panel and a plurality of spaced apart light detectors positioned along an edge of the display panel opposite the light emitters. The light ernitters are selectively energized and, 25 while each light emitter is energized, a corresponding light detector is sampled to determine whether light from the energized light emitter is being received by the enabled light detector. The light emitters are preferably energized in a pseudo-random manner to reduce the probability that a plurality of touch screen systems operating in close proximi~r will 30 operate in synchronism with each other and thus cause interference. In order to rninimize the effects of variations in ambient light and temperature, ambient light and temperature are measured and used to control the power applied to each light emitter so that the intensity of the light generated by the light emitters is a function of the intensity of arnbient35 light and temperature. In order to further reduce the sensitivity of the touch screen keyboard to interference, the touch screen keyboard is scanned a plurali~y of times before a touch screen key is considered to be ! ? ;
2~96977 selected. More specifically, during each scan, the locations of obscured light beams are detected and recorded in a ta~le. After a plurality of scans, the table is exarnined and the presence of a key selection is indicated by a light beam being obscured during a predetermined number or S predeterrnined percentage of scans. As a result, the touch screen keyboard is relatively insensitive to random noise sources.
Brief ~ ~tion of the I:)rawin~s Figure 1 is a mechanical schematic showing one embodiment 10 sf a touch screen keyboard.
Figure 2 is a system block diagram of the inventive touch screen keyboard system.
Figure 3 is a schematic of a high pass filter and amplifier circuit receiving signals generated by the light detectors and an ambient 15 bias circuit for providing a signal indicative of ambient light, both of which are used in the system of Figure 2.
Figure 4 is a schematic of a circuit used in the system of Figure 2 for energizing light emitters.
Figure 5 is a schematic of a digital one-shot used in the 20 system of Figure 2 to control the duration during which the light emitters are energized.
~ igure 6 is a flow chart of the main loop soft vare used in the system of Figure 2.
Figure 7 is a schematic of the software used in the system of 25 Figure 2 to scan the X-axis of the touch screen display.
Figure 8 is a flow chart of the software used to select each light emitter/detector pair during scanning.
Figure 9 is a flow chart of a subroutine used to sample the intensity of ambient light.
Figure 10 is a flow chart of the software used to calculate the desired intensity of light generated by the light emitters.
Figure 11 is a ~ow chart of the software for adjusting the intensity of light generated by the light emitters as a function of ambient temperature.
Figure 12 is a flow chart of the software used in the system of Figure 2 to illurninate a selected light en~itter and sample the corresponding light detector.
, ... . . . . . . .. ...
2~977 Figure 13 is a flow chart of the software used in the system of Figure 2 to scan the Y-axis of the touch screen display.
Figure 14 is a flow chart of the software used to determine the X-axis position of a selected key.
Figure 15 is a flow chart of the software used to determine the Y-a~as position of a selected key.
Best Mode for Canying Out the I~ventio~
A preferred embodiment of the inventive touch screen 10 keyboard is illustrated in schematic fonn in Figure 1. As with conventional touch screen displays, the preferred embodiment of the touch screen board 10 uses a rectangular CRT display screen 12 surrounded by a bezel 14. A
plurality of equally spaced light emitters 16 are mounted along the left edge bezel 14a. Similarly, a plurality of spaced apart light ernitters 16 are 15 mounted in the lower bezel 14b. Although the number of light em~tters 16 used will depend upon the desired resolution of the touch screen keyboard, in the preferred embodiment thirty-two light ernitters 16 are mounted in each bezel 14a,b. ;
Regardless of the number of light emitters 16 used~ a plurality 20 of light detectors 18 corresponding in number and position to the light emitters 16 on the opposite bezel are mounted in the bezels 14c,d along the remaining edges of the screen 12. As is well known in the art, the light emitters 16 are selectively energized during which time the light detectors 18 mounted in the corresponding positions i~ the opposite bezel are 25 individually sampled. If the light path from each light emitter 16 to the corresponding light detector 18 is not obscured, the light generated by the light emitter 16 generates a signal at the light detector 18. If, however, a finger, pointer or other object is placed on the screen 12 over a displayed key positioned along the light path, the emitted light is obscured and thus 30 does not reach the detector 18. By scanning along the x-axis using the light emitters 16 in the bezcl 14b and along the y-axis using the light emitters 16 in the bezel 14a, the exact position of the seleeted key can be determined.
In the preferred embodiment illustrated in Figure 1, the light detectors 18 are phototransistors. These phototransistors 18 used in the 35 preferred embodiment and in conventional touch screen keyboards have gain characteristics that are affected by ambient light and temperature. In order to minimize the effects of variations in ambient light and :- "
''' ' ' 2~977 temperature, the emitters 16 are typically driven at a level that is high enough to be sensed by the light detectors 18 under worst case, low gain conditions. However, when the light detectors 1~ are not operating under their worst case, low gain conditions, sufEicient light from the light emitters 5 16 can be reflected from adjacent surfaces to the associated light detector 18. Under these circumstances, the touch screen keyboard will fail to detect the selection of a key on the screen 12.
A preferred embodiment of a system for scanning the light emitters 16 and detectors 18 in the embodiment of Figure 1 is illustrated in 10 Figure 2. The system 30 includes a control subsystem 32 and an emitter/detector subsystem 34. The control subsystem 32 includes a microprocessor 36 of conventional design which, as is well known in the art, includes an internal timer circuit, read-only memory (ROM) for storing program instructions, digital input/output ports, analog input ports 15 connected to an internal analog-to-digital convertor, random access memory (RAM) and a serial input/output port. The microprocessor 36 receives a clock signal generated in a conventional manner to control the operation and timing of the rnicroprocessor 36. The microprocessor 36 operates in accordance with a program of instructions which are explained 20 in detail below.
The emitter/detector electronics 34 include an emitter column selector 40 implemented by a conventional multiplexer and discrete power transistors, as well as an emitter row selector 62 implemented by a conventional multiplexer. The emitter column selector 40 applies power to 25 the anode of a light emitting diode 16 designated by three bits of a six bit "Select" word when enabled by the "Emitter On-n signal. The six bit "Select"
word is received &om a digital I/O port of the microprocessor 36. The "Emitter On-N signal is generated by the digital one-shot 46.
An analog "Emitter Current Set" signal is generated by a 30 digital-to-analog converter 42 i~ the control subsystem 32. The digital-to-analog converter 42 is, in turn, controlled by 8 bits of data from digital I/O
ports of the microprocessor 36. The "Emitter Current Set" signal is directed by the ernitter row selector 62 to a voltage to current converter consisting of resistors 52 and 54 and transistors 50 and 56. As with the emitter column 35 selector 40 above, the emitter row selector 62 designates the voltage-to-current converter via the remaining three bits of the six bit "Select" word .
. . .. . . .
2~6~77 when enabled by the "Emitter On-" signal. The six bit "Select" word is received from a digital I/O port of the rnicroprocessor 36.
When directed by the emitter row selector 62, the "Emitter Current Set" signal is applied to the base of a transistor 50 which is normally 5 biased at ground through resistor 52. The energized transistor 50 conducts current from the base of PNP transistor 56, causing a larger current to flow from the cathode of light emitting diode 16 to resistor 54. Subsequent current flow through resistor 54 generates a voltage which is substantially limited to the "Emitter Current Set" voltage.
Luminous intensity generated by light emitter 16 is directly proportional to the amount of current flow through the device. The '~rnitter Current Set" signal thus acts as a light emitter intensity control signal. The period of time that the light ernitter 16 is illuminated is controlled by the duration of the "Emitter On-" signal generated by the 15 digital one-shot 46.
Figure 2 shows a single light emitter 16 in control system 30.
However, in the preferred embodiment illustrated in Figure 1, 64 light emitters 16 are used. The 64 light emitters are organized as an eight-by-eight cross bar switch. Emitter column selector 40 relies upon the three low 20 order bits of the six bit "Select" word to designate one of eight possible columns of eight light emitter 16 anodes. Emitter row selector 62 relies ~- -upon the three high order bits of the six bit "Select" word to designate one of eight possible rows of eight light emitter 16 cathodes. Emitter row selector 62 and emitter column selector 40 are energized simultaneously via 25 "Emitter On-N signal. For any value of the six bit "Select" word, emitter rowselector 62 and emitter column selector 40 may intersect at only one light emitter 16.
Thus the six bit "Select" word indi~lidually selects one of sixty-four possible light emitters 16. "Emitter Current Set" controls light intensity 30 radiated from that individual light emitter 16 which is energized for a fixed short period of ~ne by the "Emitter On-" signal. Current applied to the light emitter 16 and its resulting light intensity are fully adjustable over a `
range which far exceeds the steady state current rating for the light emitter 16. The extremely short "Emitter On'n signal generated by the digital one-35 shot 46 and low device activation duty cycle allow such excess currents and their resulting increased light intensity without degradation to the light ~ -: ,-....
', . '':
~ ~. ' . ' , ' , ,' , ' 20~6977 emitter 16. This increased li~ht intensi~ provides a higher signal level than would be available using conventional touch techniques.
The collector of a correspond;ngly positioned phototransistor 18 is connected by a detector selector 60 to a low pass filter 62 and to a high 5 pass filter and amplifier 64. The same "Select" which designated light emitter 16 also designated its corresponding phototransistor 18.
Phototransistor 18, however, is enabled only by the "Select" word, and so is active before and after the light pulse of light emitter 16 occurs.
The collector of the phototransistor light detector 18 is 10 connected to one of several inputs to conventional multiplexer 70. The "Select" word and associated decoding cause the phototransistor light detector 18 to be applied to the output of multiplexer 70. Although a single multiplexer 70 connected to eight light detectors 18 is shown in Figure 3, it will be understood that a total of 64 light detectors 18 are used in the 15 preferred embodiment of Figure 1. For any value of the six bit "Select"
word, only one light detector 18 associated with its physical counterpart light emitter 16 is applied to the high pass filter and arnplifier 64 and low pass filter 62. Additional multiplexers 70 are selectively enabled via decoding of the three high order bits of the six bit "Select" word. The ~hree 20 low order bits are decoded directly by each multiplexer 70 via the A, B, C
input to the multiplexers 70.
The output of the multiplexer 70 is biased through resistor 72 by a supply voltage VCCA generated by a conventional voltage regulator 74. Voltage regulator 74 is, in turn, powered by the system power supply 25 which is filtered by capacitor 76. Voltage regulator 74 provides isolation and suppb stability for the high fixed gain amplifier and high pass filter 64 detailed in Figure 3. Clamping diode 78 is provided to protect voltage regulator 74 from damage caused by a polarity reversal due to a loss of the system power supply voltage.
Ambient light striking phototransistor light detector 18 causes a current to flow from "VCCA" through resistor 72 and multiplexer 70 into its collector. Voltage drop across resistor 72 provides a signal at the output of multiplexer 70. Berause of the low pass characteristics of the low pass filter 62, it does not respond to the pulse of light from the light emitter 16.
35 Instead, it provides a signal indicative of the level of ambient light as measured by the phototransistor 18. In this manner, the output of the low pass filter 62 will be a function of not only the level of ambient light, but also the gain of the phototransistor 18. The ambient light signal output by the low pass filter 62 is applied to an analog input port of the microprocessor 36.
The high frequency characteristics of the high pass filter and S amplifier 64 allow it to respond to the pulse of light from the light emitter 16. Accordingly, if the light path from the light emitter 16 to the light detector 18 is not obscured, a signal pulse will be generated at the output of the high pass filter and amplifier 64 each time the light emitter 16 is energized. The signal pulse is applied to an analog input port of the 10 rnicroprocessor 36 to allow the microprocessor 36 to determine that none of the keys positioned along the path f~om the light emitter 16 to the light detector 1~ is being selected.
Finally, the emitter/detector subsystem 34 includes a conventional temperature sensor 68 which outputs a signal indicative of 15 arnbient temperature. This ambient temperature signal is also applied to an analog input of the microprocessor 36 so that the microprocessor 36 can adjust the intensity control signal as a function of both temperature and ambient light. Once the microprocessor 36 detelmines the location of a selected key, it outputs this information to a host computer through a serial 20 I/O port so that the computer can identify and implement the selected key function.
The high pass filter and amplifier 64 forming part of the emitter/detector subsystem 34, is illustrated in greater detail in Figure 3.
The collector of the phototransistor light detector 18 is applied to one of 25 several inputs to conventional multiplexer 70. When the multiplexer 70 is enabled by the six bit "Select" word, it applies one of the inputs to its output.
The output of the multiplexer 70 is generally a signal consisting of a direct current (DC) offset indicative of ambient light striking the phototransistor.
A pulse, corresponding to an energized light emitter, is present only when 30 light detector 18 is not blocked by an object from receiving its associated light emitter output. Although a single multiplexer 70 cormected to eight light detectors 18 is shown in Figure 3, it will be understood that a total of eight multiplexers 70 are provided for the 64 light detectors 18 used in the preferred embodiment of Figure 1. These additional multiplexers 70 are 35 selectively enabled by higher order bits of the eight bit "Select" word from the multiplexer which are applied to the A,B,C inpu~ of the multiplexers 70.
2~6377 The output of the multiplexer 70 is biased through resistor 72 by a supply voltage VCCA generated by a conventional voltage regulator 74. The voltage regulator 74 is, in turn, powered by the system power supply which is filtered by capacitor 76. Clarnping diode 78 is provided to 5 prevent the power supply voltage VCCA from being driven by transients significantly above the system power supply voltage. When the multiplexer 70 connects the output to one of the inputs, the associated phototransistor 18 is driven by the voltage regulator 74 through resistor 72.
The signal at the output of the multiplexer 70 is applied to 10 two distinct circuits. The first of these circuits is an ambient light bias circuit 80, which consists of an operational amplifier 82 having a surnming resistor 84, and a low pass filter formed by resistor 86 and capacitor 88 connected in parallel to provide negative feedback. Capacitor 90 also limits the high frequency response of the amplifier 82. The amplifier 82 is 15 powered through resistor 92, and this power supply voltage is low pass filtered by capacitor 94. The noninverting input of the operation amplifier 82 is biased to a predetermined value by voltage divider resistors 96, 98.
The bias level set by the voltage divider resistors 96, 98, in combination with the gain of the amplifier 82 set by the ratio of feedback resistor 86 to 20 summing resistor 84, scales the voltage indicative of ambient light to within a predetermined operating range. Also, as explained above, the low pass characteristics of the amplifier 82 provided by capacitors 88, 90 prevents the arnplifier 82 from responding to light pulses from the associated light emitter 16 so that the output of the amplifier 82 is indicative of ambient 25 light.
The output of the multiplexer 70 is also applied to the high pass filter and arnplifier 64 illustrated in Figure 2. As illustrated in Figure 3, the high pass filter and asnplifier 64 includes three amplifjring transistors100, 102, 104 having respective load resistors 106, 108, 110. The bases of 30 the transistors 100, 102, 104 are each biased by respective voltage divider resistors, 112, 114. Finally, the signal pulses are coupled to the base of each transistor 100 104 by a respective coupling capacitor 118. Power is supplied to the transistors 100 lQ4 through resistor 120 which, in combination with capacitor 122 low pass filters the power supply voltage. A signal pulse 35 corresponding to the pulse of light received by the phototransistor 18 is thus output from the collector of transistor 104 through resistor 126. This pulse 2 ~ 7 7 is applied to an analog input of the microprocessor 36 as illustrated in Figure 2.
One of the advantages of the circuitry used irl the high pass filter and amplifier 64 is that requires only a single polarity of power supply.S It also provides low noise and high gain with little cost and good insensitivity to temperature variations. In contrast, high pass filter arnplifiers using operational amplifiers or operating open loop have poor pulse mode responses due to their limited slew rate at high gains.
Additionally, judiclous selection of passive component values allow 18 dB
10 per octave low pass rejection of the principal contarnination sources below 300 Hz. Although high gain, the amplifier is desi~ed with an order of magnitude less sensitivity than are found in common touch screen keyboards. This takes advantage of the much higher luminous signal strength provided by high energy light emitter 16 pulse, and thus ambient 15 light noise is further reduced in the system. High luminous signal strength and low noise contarnination are fundamental improvements provided by the invention. Further, the amplifier provides a stable, fixed high gain with low group delay which allows the light emitter 16 pulse period to remain short.
Tbis technique provides a significant advantage over techniques which use a variable gain amplifier and ~xed output emitter. In the latter technique, when an emitter/detector pair require additional signal strength to compensate for component rariation, both signal and noise are increased via variable gain amplifier. Thus the signal to noise 25 ratio is not improved. Using the invention technique described herein, signal is increased without an accompanying increase in ambient noise, improving signal to noise in the system.
The digital-to-analog converter 42 (Figure 2), emitter column selector 40, emitter row selector 62, and the remaining emitter drive 30 components 5~56 are shown in combination with light emitter 16 in Figure 4. The digital-to-analog converter 42 is a conventional integrated circuit digital-to-analog converter having an 8-bit input for receiving a digital word indicative of the analog voltage as weil as chip enable and chip select inputs. All of the inputs of the digital-to-analog converter 140 are 35 generated by the microprocessor 36 (Figure 2). The output of the digital-to-analog converter 140 is an analog voltage corresponding to the value designated by the digital word. This analog voltage is low pass filtered by 2 ~ 7 ~
capacitor 144 and applied to the common terrninal of the multiplexer 44, as explained above. As also mentioned above, the "Emitter On" output from the digital one-shot 46 (Figure 2) controls the duration that the "Ernitter Current Set" analog voltage from the D/A converter 140 causes current to 5 flow through the selected light emitter 16.
The emitter column selector 40 includes a conventional multiplexer 150 to which 3 bits of the six bit "Select" word are applied. The multiplexer 150 provides a path to ground through resistor lS2 to one of eight I/O outputs selected by the 3-bit word. An inhibit input is enabled by 10 the "Ernitter On-" signal. Darlington transistors 162, 164 are normally biased off by resistor 168. When "Emitter On-" is asserted, current flows out of the base of transistor 162, through the multiplexer 150 and resistor to ground. The transistor Darlington pair 162, 164 becomes a saturated switch, applying essentially "VCC' to the anode of light emitter 16.
15 Simultaneously, when the inhibit input of conventional multiplexer 44 is enabled via "Emitter On-" signal, current is conducted from the cathode of light emitter 16 via the voltage-to-current converter consisting of transistors 50, 56 and resistors 52, 54. l~e voltage-to-current converter is energized via the conventional multiplexer 44 which forms the emittér row selector 62 20 as previously described.
The supply voltage outputs from the multiplexer 150 are applied to a respective Darlington pair of transistors 162, 164 to switch the power supply voltage to the anode of light ernitter 16. The transistors 162, 164 are biased off through resistor 168.
The remaining circuitry shown in Figure 2 is the digital one-shot 46 which generates the "Emitter On-" signal for the emitter column selector 40, en~itter row detector 61, and detector selector 60. The digital one-shot 46, which is illustrated in Figure 5, uses a conventional integrated circuit counter 160 having a reset input receiving a pulse enable signal from the microprocessor 36 and a clock signal output by a NOR-gate 162. The NOR-gate 162 in turn receives a two mH~ clock from the microprocessor 36 and the Q7 output of the counter 160. When the terminal count of the counter 16Q is reached, the logic "1" signal at the Q7 output disables the NOR-gate 162 to prevent the clock signal from reaching the clock input of 35 the counter 160. Under these circumstances, the Q7 output of the counter 160 remains at logic l-1" thereby causing NOR-gate 164 to output a logic "0".
The output of NOR-gate 164 is applied to a third NOR-gate 166 acting as - . . . . . . ~ . . . ; , ~ ; - . . : . . .. --2~9 ~7 an inverter through capacitor 168. The input to NORgate 166 is biased low through resistor 170, and it is clamped from being driven substantially below zero volts by diode 172. The digital one-shot circuit is designed to require a pair of actions at the "Pulse Enable" input from the 5 microprocessor 36 in order to activate an emitter light pulse. Fist, "Pulse Enable" goes high, causing a reset of counter 160 and thereby causing the output of Q7 to go low. The output of NOR-gate 164 remains low, however, because the "Pulse Enable" input is now high. Further, counter 160 is held in reset and will not count until "Pulse Enable" is set low. NOR-10 gate 162, however, is now enabled, allo~,ving the 2 MHz clock to passthrough to the clock input of counter 160. The high to low transition of "Pulse Enable" releases the counter 160 and causes a high output from NOR-gate 164 to couple through capacitor 168 to produce a negative going pulse at the NOR-gate 166. When the counter 160 once again reaches the 15 terminal count, the NORgate 162 is disabled as explained above, and the output of the NOR-gate 166 is driven high through NOR-gate 164 and capacitor 168. The negative going pulse at the output of the NORgate 166 controls the duration that the light emitters 16 are illuminated as explained above. Capacitor 168 is provided to insure that the light emitters 16 are not 20 energized indefinitely if, for some reason, the counter 160 or its associated circuitry malfunctions so that the terminal count is not reached. Under these circumstances, capacitor 168 will discharge through resistor 170 thereby once again causing the output of NORgate 166 to go high.
As mentioned above, the microprocessor 36 (Figure 2) 25 operates in accordance with a program of ins~ructions. Flow charts showing this prograrn are illustrated in Figures 6-15. With reference to Figure 6, the main loop program is entered at 200 and standard initialization functions, such as setting up I/O ports as either inputs or outputs, clearing registers, etc., are performed at 202. The operation of the emitter and detector 30 electronics are then verified at 204 by sequentially illuminating each emitter and detecting receipt of the emitted light at the associated detector. AD
internal counter in the microprocessor 36 that records the number of keyboard scans is then reset at 206. The main loop program calls a "SCAN
X-AXIS" subroutine at 208 to scan the light ernitters and detectors 35 positioned along the lower and upper edges, respectively, of the screen 12 (Figure 1). After all of the x-axis emitters/detectors have been scanned, the program checks at 210 to determine if a predetermined number, e.g., 3, 2 ~ 9 7 7 scans of the x-axis have been completed. If not, the scan counter is incremented by one at 212 and the "SCAN X-AXIS" subroutine is once again called at 208.
After a predetermined number of x-axis scans have been 5 completed the main loop branches to 214 where a "CHK X" subroutine is called. As explained in greater deta~l below, the "CHK X" subroutine examines a record of interrupted light bearns from the emitters to associated detectors along the x-ax~s to determine if the size of the interrupting object is consistent with a finger or other pointer. The purpose 10 of the "CHK X" subroutine is to reject interrupting targets that are either too big (such as interruptions caused by cleaning the screen 12 with a cloth) or too small (such as i~terruptions produced by a fly). If the subroutine determines at 214 that the interrupting object is the proper size, it sets a "VAI~D X TARGET FLAG" to 1.
lS The main loop program then progresses to 216 where the VAIID TARGET Fl.AG is checked. With the VALID TARGET FLAG is found at 216 to be set to 1, tbe program branches through path 218 to scan the y-axis emitters/detectors as explained below. However, if the VALID
TARGET FIAG is not set to 1, the program branches to æo to detennine 20 if the VALID TARGET FLAG had previously been set to 1 thus indicating that a finger or pointer had been removed from the screen 12. If not, the prograrn waits for a timeout at 222 before returning through 224 to reset the scan counter at 206 and follow the steps described above.
If the main loop program has determined at 216 that the 25 VALID TARGET Fl AG is not set to 1 but it determines at 220 that the flag was previously set to 1, the prograrn branches to 230 where a REPEAT
MODE FL~G is checked. The REPEAT MO~E FLAG is set to 1 by a host computer if it is desired to allow a keyboard function to be continuously designated such as, for example, a constantly depressed 30 spacebar key. If the REPEAT MODE FLAG is not set to 1, thus indicating that the repeat mode is not active, the program branches to 222 to wait for a timeout before returning through 224. If the repeat mode is active, a "REPORT KEY GONE" subroutine is called at 234 to prov~de an indication that the selected key is no longer being selec~ed.
After a valid target has been detected at 216, the main loop program proceeds via 218 to scan the y-axis emitter/detectors as explained above. A y-axis scan counter internal to the n~icroprocessor 36 is reset at 20~9~7 240 in the same manner that the x~ is scan counter is reset at 208.
Thereafter, the y-axis emitter/detectors are scanned at steps 242, 244, 246 in the same manner that the x-axis emitter/detectors are scarmed in steps 208, 21Q 212, respectively. Similarly, after the y-axis has been scanned a S predeterrnined number of times as the term the 244, a "CHK Y" subroutine is called at 250 which deterrnines if the obscuring target is the proper size inthe same mar~ner that the "CHK X" subroutine called at 214 performs that function. The main loop program then determines at 252 if a valid y-axis target is present. If so, the program branches to 254 to check the REPEAT
10 MODE FLAG. If the repeat mode is active, the selected key is reported at 256. Otherwise, the program branches to 258 to determine if the selected key has already been reported. If not, the key is first reported at 256. After the selected key is reported at 256, the PREVIOUS TARGET FLAG is set to 1 at 260 before waiting for a timeout at 262 and eventual return through 15 224 as explained above. If the ma~n program determines at 258 that the selected key has already been reported, the PREVIOUS TARGET FI AG
is set to 1 at 260 without once again reporting the presence of the selected key.
Returning to step 252, if the program determines that a valid 20 "y" target has not been selected, the program branches to 270 to deterrnine if the target was previously selected. If not, the program waits at 262 for a timeout before returning. Otherwise, the prograrn checks at 272 to determine if the repeat mode is active. If the repeat mode is active, the program reports the fact that the selected key is no longer being selected at 274 before waiting for a timeout at 262. If the repeat mode is not found to be active at 272, there is no need to report the absence of the selected key since only the initial actuation of the selected key need be reported.
Therefore, the program branches directly from 272 to 262 to await a timeout.
As mentioned above, the first subroutine that is called by the main loop program of Figure 6 is the "SCAN X-AXIS" subroutine which is called at 208. The SCAN X-AXIS subroutine is illustrated in detail on Figure 7. The SCAN X-A~S subroutine is entered at 300 and a "GET IR
PAIR" subroutine is called at 302 to energize a specific light emitter and 35 enable a specific light detector. With reference to Figure 8, the "GET IR
PAIR" subroutine 302 is entered at 310 and a system clock counter internal to the microprocessor 36 is sampled at 312. The low order bits of the 2~6977 counter are then masked off at 314 so that only the low order bits are exa~uned. This acts as a pseudo-random number generator for selecting IR
pair to be activated. The low order bits are used to identify specific emitter/detector pair. The subroutine deterrnines at 316 whether the 5 emitter/detector pair corresponding to the low order bits have previously been sampled during a given scan. If not, the low order bits are stored in a bitmap at 318 to designate that the corresponding emitter/detector is being sampled. Appropriate outputs from the rnicroprocessor 36 are then enabled at 320 as described during the explanation of the hardware thereby 10 energizing the selected emitter and enabling the selected light detector.
The program then returns to the "SCAN X-A~S" subroutine 208 shown in Figure 7 via 322. If the "GET IR PAIR" subroutine determines at 316 that a emitter/detector pair corresponding to low order address bits have previously been sampled, the low order address is incremented at 324 and 15 the bitmap is then examined at 326 to determ~ne if all of the emitter/detector pairs have been sampled. If not, the prograrn returns to 316 to repeat the above-described procedure. After all of the ernitter/detectors have been sampled, the subroutine returns to the calling subroutine through 322. ~ -Returning, now, to Figure 7, after the "GET IR PAIR"
subroutine has been executed at 302, the subroutine waits a predeterrnined period for the electronic circuitry to stabilize at 330. The subroutine then calls a "GET BL~S" subroutine at 332. The "GET BL4S" subroutine is illustrated in detail in Figure 9. The "GET BL~S" subroutine 332 is entered 25 at 340 and the analog-to-digital converter internal to the rnicroprocessor 36is enabled at 342. The program then waits for a predetennined period at 344 to allow the analog-to-digital converter to perform its acquisition process, and the output of the analog-t~digital converter is saved at 346 before returning through 348. The value saved at 346 is indicative of the 30 intensity of arnbient light as measured by the selected light detector.
Returning once again to Figure 7, the "SCAN X-A~S"
subroutine 208 then calls a "CALC POWER" subroutine at 3S0. The "CALC POWER" subroutine 350 is shown in detail in Figure 10. The "CALC POWER" subroutine is entered at 360 and a minimum value of 35 emitter intensity is designated at 362 depending upon the measured value of ambient light. The subroutine then determines at 364 whether the ambient light is below a minimum threshold. If so, a minimum intensity default .. : : . . . . .. - ....... ....... .. . . .. .
2 ~
value is selected and the program branches to 366 where it returns to the "GET X-AXIS" subroutine 208 illustrated in Figure 7. If the ambient light is below a predetermined minimum value, the subroutine checks if it is above a predetermined maximum value at 368. If so~ a maximum power 5 level is set at 370 before returning through 366. If the intensity of the ambient light is somewhere between a predetermined minimum and ma~amum value, the subroutine branches to 370 where an intensity value corresponding to ambient light is selected in a lookup table. As is well known in the art, a lookup table contains a record of the optimum light 10 ernitter intensity for each value of ambient light and it will generally following a non-linear relationship. Once the light intensity is selected at -37Q the program branches to 372 to multiple the normalized power value by the value of arnbient light as a function of its relationship between the minimum and maximum values. This value is then added to the minimum 15 intensity value at 374 and the result is saved as the desired value at 376.
After the desired ernitter intensity is calculated, the subroutine once again returns to the "SCAN X-AXIS" subroutine 208 in Figure 7. An "ADJ-TEMP" subroutine is then called at 38Q The "ADJ-TEMP ' subroutine 380, which is illustrated in Figure 11, is entered at 390 -20 and the output of the temperature transducer 68 (Figure 2) is sampled at 392. The difference between the current ambient temperature and the ambient temperature during calibration is then determined at 394. If the current temperature at 396 to be the same at the ambient temperature during calibration, the subroutine returns to the "SCAN X-A~S"
25 subroutine 208 via 398. Othen~ise, the difference in temperature is multiplied by an appropriate scale factor at 400 and the emitter intensity--value calculated at 350 is multiplied by the scale factor at 402. In this manner, the "ADJTEMPN subroutine 380 adjusts the desired emitter ;j -intensity as a function of ambient temperature.
Retuming, once again, to Figure 7, the "SCAN X-AXIS"
subroutine then sets the power level corresponding to the ernitter intensity at 410 by applying a byte to digital-to-analog converter 42 (Figure 2) indicating the desired power level. A "GET IR" subroutine is then called at 420 to trigger the one-shot 46 (Figure 2) and apply appropriate bits to the 35 emitter selector 40 and detector selector 60.
The "GET IR" subroutine 410 is illustrated in detail in Figure 12. The "get IR" subroutine is entered at 450 and the digital one-shot 46 ' ," ";, ~ " , - ,~ "
(Figure 2) is then triggered by a pulse at the output of the microprocessor 36 at 452. The program delays an appropriate period at 454, such as 16 microseconds, to allow the detector circuitry to stabilize before sampling the output of the high pass filter 64 at 456 to determine whether the emitted S ligbt is being received at the associated detector. . The program then returns to the "SCAN X-A~S" subroutine through 458.
After the "GET IR" subroutine has been completed, the results of the test are then saved in a bitmap at 4æ, as illustrated in Figure 7. The bitrnap is a table having a location for each emitter/detector pair 10 for each scan of the keyboard. Thus, a touch screen keyboard having 64 emitter/detector pairs along the x-axis will have 192 memory locations if the keyboard is to be scanned three times. The subroutine determines at 324 if all of the emitter/detector pairs have been scanned. If not, the subroutine returns to 302 to once again perform the "GET IR PAIR"
15 subroutine. After all of the emitter/detector pairs have been scanned, the subroutine returns through 426 to the main loop prograrn at 210 (Figure 6).
As explained above with respect to the main loop program, after the "SCAN X-AXIS" subroutine is performed to identify the "x"
location of an obscured emitter/detector pair, the main loop prograrn calls 20 at 242 a "SCAN Y-AXIS" subroutiDe. The "SCAN Y-A~S" subroutine, which is illustrated in Figure 13, calls the same subroutines and performs essentially the same function as the "check y" subroutine. Therefore, in the interest of brevity, it will not be separately explained but instead the flow chart has been assigned the sarne reference numerals as the corresponding 2S functions of the "SCAN X-AXIS" subroutine of Figure 7.
The final subroutine executed by the main loop program of Figure 6 is the "CHK X" subroutine 214 which is illustrated in Figure 14.
The "CHK X" subroutine 214 is entered at 480. It will be recalled that the "SCAN X" subroutine saves a bitmap of obscured light beams for several 30 scans at 422. This bitmap is examined at 482 to identi~y light emitters/lightdetector pairs that are to be considered as obscured using an appropriate voting format. For exarnple, if the x-axis light emitters/detectors are scanned three times, the bitmap created during the "SCAN X" subroutine will contain three bits for each light emitter/detector pair. The subroutine 35 identifies a light emitter/detector pair as being selected if the light beam from the emitter to the detector has been obscured in any two of the three scans. Consequently, if during one of the scans light from an emitter has 2 ~ ~ 6 9 l' 7 reflected on to the associated detector, that reflection will be ignored and a valid key selection will be recorded.
After the obscured beams have been identified at 482, the subroutine detennines the right-most and left-most obscured beams at 488 5 and then calculates the target size at 490 based upon the number of beams obscured and the spacing between the beams. The calculated target size is then compared to a predeterm~ned mirumum target size at 492. If the target size is too small, such as a single beam is obscured, then an identifying flag is set at 494 and the subroutine returns to the main loop 10 program through 496. If the target is not too small, the subroutine branches to 498 where the calculated target size is compared to a predetermined large value. If the target is too large, such as would occur if the screen 12 (Figure 1) was being cleaned by a cloth, an appropriate flag is set at 500 before returning through 496.
With reference to the main loop program of Figure 6, after the "CHK X" subroutine in 214 is executed, the progra n eventually progresses to a "CHKY" subroutine which is executed at 252. The "CHK Y" subroutine 250 is illustrated in Figure 15. The "CHK Y"
subroutine is identical to the "CHK X" subroutine, except that it performs 20 its function for the y-axis light emitter/detectors rather than the x-axis light emitter/detectors. Therefore, in the interest of brevity, it has been given the same reference numerals for the corresponding functions.
The inventive touch screen keyboard is thus insensitive to ambient light interference, even from touch screen displays having identical 2S scan patterns, and it is insensitive to reflections of emitted beams from touch screen components. It also compensates for the effect of changes in ambient light, temperature, component aging and environrnental variations without overdriving the light emitters. Furthermore, the im~entive touch screen keyboard does not require close matching of the electrical 30 characteristics of electrical components in order to provide uniform performance.
Claims (24)
1. A touch screen keyboard system for a display panel, comprising:
a plurality of spaced-apart light emitters positioned along at least one edge of said display panel;
a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters;
power means for selectively energizing each of said light emitters in response to an activation signal applied to each of said light emitters;
detector means for enabling an output from at least one predetermined light detector while a respective light emitter is being energized, and for determining whether light from the energized light emitter is being received by said enabled light detector; and control means for generating an activation signal for each of said light emitters in a pseudo random manner, thereby energizing said light emitters in a pseudo random manner to reduce the probability that a plurality of touch screen keyboard systems operating in close proximity will operate in synchronism and thus interfere with each other.
a plurality of spaced-apart light emitters positioned along at least one edge of said display panel;
a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters;
power means for selectively energizing each of said light emitters in response to an activation signal applied to each of said light emitters;
detector means for enabling an output from at least one predetermined light detector while a respective light emitter is being energized, and for determining whether light from the energized light emitter is being received by said enabled light detector; and control means for generating an activation signal for each of said light emitters in a pseudo random manner, thereby energizing said light emitters in a pseudo random manner to reduce the probability that a plurality of touch screen keyboard systems operating in close proximity will operate in synchronism and thus interfere with each other.
2. The touch screen keyboard system of claim 1 wherein said display panel is rectangular, and wherein said light emitters are positioned along two adjacent edges of said panel, and said light detectors are positioned along the two remaining edges of said panel.
3. The touch screen keyboard system of claim 1 wherein only one of said light detectors is enabled while a respective light emitter is being energized.
4. The touch screen keyboard system of claim 3 wherein each of said light emitters is positioned opposite a corresponding one of said light detectors, and wherein the light detector corresponding to a respective light emitter is enabled while said light emitter is energized.
5. A touch screen keyboard system for a display panel, comprising:
a plurality of spaced-apart light emitters positioned along at least one edge of said display panel;
a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters;
power control means for selectively energizing each of said light emitters in response to an activation signal applied to each of said lightemitters, said power control means energizing each of said light emitters at an intensity corresponding to a respective intensity control signal;
detector means for enabling an output from at least one predetermined light detector while a respective light emitter is being energized, and for determining whether light from the energized light emitter is being received by said light detector; and compensation means for generating each of said intensity control signals as a function of the intensity of ambient light so that the intensity of light emitted by said light emitters is a function of the intensityof ambient light.
a plurality of spaced-apart light emitters positioned along at least one edge of said display panel;
a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters;
power control means for selectively energizing each of said light emitters in response to an activation signal applied to each of said lightemitters, said power control means energizing each of said light emitters at an intensity corresponding to a respective intensity control signal;
detector means for enabling an output from at least one predetermined light detector while a respective light emitter is being energized, and for determining whether light from the energized light emitter is being received by said light detector; and compensation means for generating each of said intensity control signals as a function of the intensity of ambient light so that the intensity of light emitted by said light emitters is a function of the intensityof ambient light.
6. The touch screen keyboard system of claim 5 wherein said system further includes a temperature sensor for generating a temperature signal indicative of the temperature of ambient temperature, and wherein said compensation means receives said temperature signal and adjusts said intensity control signals as a function of the ambient temperature indicated by said temperature signal.
7. The touch screen keyboard system of claim 5 wherein said ambient light is measured by at least one of said light detectors, and wherein each of said light detectors is enabled before and after a respective light emitter is being energized.
8. The touch screen keyboard system of claim 5 wherein said power control means comprise voltage to current converting means connected in series with each of said light emitters, said voltage to current converting means receiving said intensity control signals and causing current to flow through said light emitters as a function of the magnitude of said intensity control signals upon receipt of said activation signal.
9. The touch screen keyboard system of claim 8 wherein said compensation means comprise:
a processor having a first I/O port receiving data indicative of the intensity of ambient light, and a second I/O port outputting data indicative of the magnitude of said intensity control signal;
a digital-to-analog converter connected to the second I/O
port of said processor, said digital-to-analog converter generating at an output said intensity control signal having a magnitude corresponding to the data output from the second I/O port of said processor; and a multiplexer connected between said digital-to-analog converter and said power control means, said multiplexer being controlled by said processor to selectively apply the output of said digital-to-analog converter to the power control means for each of said light emitters.
a processor having a first I/O port receiving data indicative of the intensity of ambient light, and a second I/O port outputting data indicative of the magnitude of said intensity control signal;
a digital-to-analog converter connected to the second I/O
port of said processor, said digital-to-analog converter generating at an output said intensity control signal having a magnitude corresponding to the data output from the second I/O port of said processor; and a multiplexer connected between said digital-to-analog converter and said power control means, said multiplexer being controlled by said processor to selectively apply the output of said digital-to-analog converter to the power control means for each of said light emitters.
10. The touch screen keyboard system of claim 5 wherein said compensation means for generating each of said intensity control signals comprises:
a processor receiving data indicative of the intensity of ambient light and generating a first digital word indicative of the desired intensity of light to be emitted by said light emitters; and a digital-to-analog converter connected to said processor, said digital-to-analog converter receiving said first digital word and generating at an output an analog signal corresponding thereto from which said intensity control signals are generated.
a processor receiving data indicative of the intensity of ambient light and generating a first digital word indicative of the desired intensity of light to be emitted by said light emitters; and a digital-to-analog converter connected to said processor, said digital-to-analog converter receiving said first digital word and generating at an output an analog signal corresponding thereto from which said intensity control signals are generated.
11. The touch screen keyboard system of claim 10 further including a multiplexer having an input and a plurality of outputs that are selectively connected to said input responsive to a second digital word, the input of said multiplexer being connected to the output of said digital-to-analog converter to receive said analog signal therefrom, the outputs of said multiplexer being connected to said power control means, and said second digital word being received from said processor so that said multiplexer outputs said intensity control signals to control the intensity of light emittedby respective of said light emitters.
12. The touch screen keyboard system of claim 10 wherein said compensation means further includes a one-shot for gating said intensity control signals to said power control means for a predetermined duration.
13. The touch screen keyboard system of claim 12 wherein said one-shot comprises:
a counter having a reset input receiving an enable input from said processor, a clock input, and a multibit output generated on respective output terminals for providing a digital word indicative of the count of said counter; and a first gate having an output coupled to the clock input of said counter, said first gate having a first input receiving a clock signal, and a second input receiving a disable signal from a first output of said counter so that said first gate is disabled when the logic level of said first output changes thereby preventing said clock signal from reaching the clock input of said counter whereby said counter is incremented by said clock signal upon receipt of said enable signal until the logic level of the signal on said first output changes state thereby preventing said clock signal from continuing to increment said counter, whereby said first output of said counter is used to gate said intensity control signals to said power control means for a predetermined duration.
a counter having a reset input receiving an enable input from said processor, a clock input, and a multibit output generated on respective output terminals for providing a digital word indicative of the count of said counter; and a first gate having an output coupled to the clock input of said counter, said first gate having a first input receiving a clock signal, and a second input receiving a disable signal from a first output of said counter so that said first gate is disabled when the logic level of said first output changes thereby preventing said clock signal from reaching the clock input of said counter whereby said counter is incremented by said clock signal upon receipt of said enable signal until the logic level of the signal on said first output changes state thereby preventing said clock signal from continuing to increment said counter, whereby said first output of said counter is used to gate said intensity control signals to said power control means for a predetermined duration.
14. A touch screen keyboard system for a display panel, comprising:
a plurality of spaced-apart light emitters positioned along at least one edge of said display panel;
a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters;
power means for selectively energizing each of said light emitters in response to an activation signal applied to each of said light emitters;
detector means for enabling at least one predetermined light detector while a respective light emitter is being energized, and for determining whether light from the energized light emitter is being received by said enabled light detector;
control means for scanning said light emitter/light detector pairs by generating an activation signal for each of said light emitters;
memory means connected to said detector means to record whether light from each of said light emitters is being received by a respective light detector during a predetermined number of scans of said light emitter/light detector pairs; and processing means operatively connected to said memory means for providing an indication that a key corresponding to a predetermined light emitter/light detector pair has been activated if light from the light emitter in said pair has not been received by the respective light detector in said pair during a predetermined number of scans of said light emitter/light detector pairs.
a plurality of spaced-apart light emitters positioned along at least one edge of said display panel;
a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters;
power means for selectively energizing each of said light emitters in response to an activation signal applied to each of said light emitters;
detector means for enabling at least one predetermined light detector while a respective light emitter is being energized, and for determining whether light from the energized light emitter is being received by said enabled light detector;
control means for scanning said light emitter/light detector pairs by generating an activation signal for each of said light emitters;
memory means connected to said detector means to record whether light from each of said light emitters is being received by a respective light detector during a predetermined number of scans of said light emitter/light detector pairs; and processing means operatively connected to said memory means for providing an indication that a key corresponding to a predetermined light emitter/light detector pair has been activated if light from the light emitter in said pair has not been received by the respective light detector in said pair during a predetermined number of scans of said light emitter/light detector pairs.
15. A touch screen keyboard system for a display panel, comprising:
a plurality of spaced-apart light emitters positioned along at least one edge of said display panel, each of said light emitters generating a pulse of light in response to a respective activation pulse;
a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters;
power means coupled to said light emitters, said power means selectively energizing each of said light emitters by applying a single activation pulse to said light emitter; and detector means coupled to said light detectors and to said power means for gating a respective output from at least one predetermined light detector at substantially the same time that a corresponding light emitter is being energized by a respective activation pulse, said detector means determining whether light from the energized light emitter is being received by said enabled light detector whereby said a location on said touch screen is interrogated by a single light pulse.
a plurality of spaced-apart light emitters positioned along at least one edge of said display panel, each of said light emitters generating a pulse of light in response to a respective activation pulse;
a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters;
power means coupled to said light emitters, said power means selectively energizing each of said light emitters by applying a single activation pulse to said light emitter; and detector means coupled to said light detectors and to said power means for gating a respective output from at least one predetermined light detector at substantially the same time that a corresponding light emitter is being energized by a respective activation pulse, said detector means determining whether light from the energized light emitter is being received by said enabled light detector whereby said a location on said touch screen is interrogated by a single light pulse.
16. The touch screen keyboard system of claim 15 wherein only one of said light detectors is enabled while a respective light emitter is being energized.
17. The touch screen keyboard system of claim 15 wherein said power control means includes a one-shot for generating said activation pulses for a predetermined duration.
18. The touch screen keyboard system of claim 12 wherein said one-shot comprises:
a counter having a reset input receiving a trigger signal from said processor, a clock input, and a multibit output generated on respective output terminals for providing a digital word indicative of the count of said counter; and a first gate having an output coupled to the clock input of said counter, said first gate having a first input receiving a clock signal, and a second input receiving a disable signal from a first output of said counter so that said first gate is disabled when the logic level of said first output changes thereby preventing said clock signal from reaching the clock input of said counter whereby said counter is incremented by said clock signal upon receipt of said enable signal until the logic level of the signal on said first output changes state thereby preventing said clock signal from continuing to increment said counter, whereby said first output of said counter is used to gate said intensity control signals to said power control means for a predetermined duration.
a counter having a reset input receiving a trigger signal from said processor, a clock input, and a multibit output generated on respective output terminals for providing a digital word indicative of the count of said counter; and a first gate having an output coupled to the clock input of said counter, said first gate having a first input receiving a clock signal, and a second input receiving a disable signal from a first output of said counter so that said first gate is disabled when the logic level of said first output changes thereby preventing said clock signal from reaching the clock input of said counter whereby said counter is incremented by said clock signal upon receipt of said enable signal until the logic level of the signal on said first output changes state thereby preventing said clock signal from continuing to increment said counter, whereby said first output of said counter is used to gate said intensity control signals to said power control means for a predetermined duration.
19. A method of scanning a touch screen keyboard system having a plurality of spaced-apart light emitters positioned along at least one edge of a display panel and a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters, said method comprising:
selectively energizing each of said light emitters in a pseudo random manner; and determining if light from each energized light emitters is being received by a predetermined light detector so that the probability that a plurality of touch screen keyboard systems operating in dose proximity will operate in synchronism and thus interfere with each other is reduced.
selectively energizing each of said light emitters in a pseudo random manner; and determining if light from each energized light emitters is being received by a predetermined light detector so that the probability that a plurality of touch screen keyboard systems operating in dose proximity will operate in synchronism and thus interfere with each other is reduced.
20. The method of claim 19 wherein each of said light emitters is positioned opposite a corresponding one of said light detectors, and wherein the light detector corresponding to a respective light emitter is enabled when said light emitter is energized.
21. A method of scanning a touch screen keyboard system having a plurality of spaced-apart light emitters positioned along at least one edge of a display panel and a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters, said method comprising:
selectively energizing each of said light emitters at an intensity that is a function of the intensity of ambient light;
enabling an output from at least one predetermined light detector while a respective light emitter is being energized; and determining whether light from the energized light emitter is being received by said enabled light detector.
selectively energizing each of said light emitters at an intensity that is a function of the intensity of ambient light;
enabling an output from at least one predetermined light detector while a respective light emitter is being energized; and determining whether light from the energized light emitter is being received by said enabled light detector.
22. The method of claim 21 further including the steps of:
determining the ambient temperature of said touch screen;
and further adjusting the intensity at which said light emitters are energized as a function of the ambient temperature.
determining the ambient temperature of said touch screen;
and further adjusting the intensity at which said light emitters are energized as a function of the ambient temperature.
23. A method of scanning a touch screen keyboard system having a plurality of spaced-apart light emitters positioned along at least one edge of a display panel and a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters, said method comprising:
selectively energizing each of said light emitters;
enabling an output from at least one predetermined light detector while a respective light emitter is being energized;
determining whether light from the energized light emitter is being received by said enabled light detector;
recording whether light from each of said light emitters is being received by a respective light detector during a predetermined number of scans of said light emitter/light detector pairs; and providing an indication that a key corresponding to a predetermined light emitter/light detector pair has been activated if light from the light emitter in said pair has not been received by the respective light detector in said pair during a predetermined number of scans of said light emitter/light detector pairs.
selectively energizing each of said light emitters;
enabling an output from at least one predetermined light detector while a respective light emitter is being energized;
determining whether light from the energized light emitter is being received by said enabled light detector;
recording whether light from each of said light emitters is being received by a respective light detector during a predetermined number of scans of said light emitter/light detector pairs; and providing an indication that a key corresponding to a predetermined light emitter/light detector pair has been activated if light from the light emitter in said pair has not been received by the respective light detector in said pair during a predetermined number of scans of said light emitter/light detector pairs.
24. A method of scanning a touch screen keyboard system having a plurality of spaced-apart light emitters positioned along at least one edge of a display panel and a plurality of spaced-apart light detectors positioned along an edge of said display panel opposite said light emitters, said method comprising:
selectively energizing each of said light emitters for a single pulse each time a corresponding location on said touch screen is to be interrogated; and determining if light from each energized light emitters is being received by a predetermined light detector.
selectively energizing each of said light emitters for a single pulse each time a corresponding location on said touch screen is to be interrogated; and determining if light from each energized light emitters is being received by a predetermined light detector.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/889,780 US5355149A (en) | 1992-05-27 | 1992-05-27 | Scanning system for touch screen keyboards |
| US07/889,780 | 1992-05-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2096977A1 true CA2096977A1 (en) | 1993-11-28 |
Family
ID=25395779
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002096977A Abandoned CA2096977A1 (en) | 1992-05-27 | 1993-05-27 | Scanning system for touch screen keyboards |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US5355149A (en) |
| EP (1) | EP0572009A1 (en) |
| CA (1) | CA2096977A1 (en) |
Families Citing this family (71)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3889046B2 (en) * | 1995-06-12 | 2007-03-07 | サムスン エレクトロニクス カンパニー リミテッド | Digitizer controller |
| US6950094B2 (en) | 1998-03-30 | 2005-09-27 | Agilent Technologies, Inc | Seeing eye mouse for a computer system |
| US5913034A (en) * | 1996-08-27 | 1999-06-15 | Compaq Computer Corp. | Administrator station for a computer system |
| US5684294A (en) * | 1996-10-17 | 1997-11-04 | Northern Telecom Ltd | Proximity and ambient light monitor |
| JPH113169A (en) | 1997-06-13 | 1999-01-06 | Tokai Rika Co Ltd | Touch operation information output device |
| US6172354B1 (en) | 1998-01-28 | 2001-01-09 | Microsoft Corporation | Operator input device |
| EP1075706A4 (en) * | 1998-04-27 | 2001-07-18 | Peter A Hochstein | Maintaining led luminous intensity |
| US6246394B1 (en) | 1998-06-04 | 2001-06-12 | Burr-Brown Corporation | Touch screen measurement circuit and method |
| US6373057B1 (en) * | 1998-09-23 | 2002-04-16 | Dickey-John Corporation | Infrared reflective article counting/detecting device |
| US6303924B1 (en) | 1998-12-21 | 2001-10-16 | Microsoft Corporation | Image sensing operator input device |
| JP2000348560A (en) * | 1999-06-07 | 2000-12-15 | Tokai Rika Co Ltd | Determining method for touch operation position |
| US6677934B1 (en) * | 1999-07-30 | 2004-01-13 | L-3 Communications | Infrared touch panel with improved sunlight rejection |
| JP2001134256A (en) * | 1999-11-05 | 2001-05-18 | Sony Corp | User detecting circuit for display device |
| US6781077B2 (en) | 2000-12-14 | 2004-08-24 | Think Outside, Inc. | Keyswitch and actuator structure |
| AU2002307121A1 (en) * | 2001-04-04 | 2002-10-21 | Elo Touchsystems, Inc. | A touch input system |
| SE0103835L (en) * | 2001-11-02 | 2003-05-03 | Neonode Ab | Touch screen realized by display unit with light transmitting and light receiving units |
| US7053967B2 (en) | 2002-05-23 | 2006-05-30 | Planar Systems, Inc. | Light sensitive display |
| US7009663B2 (en) | 2003-12-17 | 2006-03-07 | Planar Systems, Inc. | Integrated optical light sensitive active matrix liquid crystal display |
| AU2002336341A1 (en) | 2002-02-20 | 2003-09-09 | Planar Systems, Inc. | Light sensitive display |
| US7855716B2 (en) * | 2002-03-27 | 2010-12-21 | Nellcor Puritan Bennett Llc | Infrared touchframe system |
| US20040186357A1 (en) * | 2002-08-20 | 2004-09-23 | Welch Allyn, Inc. | Diagnostic instrument workstation |
| US20050288571A1 (en) | 2002-08-20 | 2005-12-29 | Welch Allyn, Inc. | Mobile medical workstation |
| JP2004127073A (en) * | 2002-10-04 | 2004-04-22 | Smk Corp | Instruction input device |
| US20080084374A1 (en) | 2003-02-20 | 2008-04-10 | Planar Systems, Inc. | Light sensitive display |
| GB2410004A (en) * | 2004-01-19 | 2005-07-20 | Time & Data Syst Int | Keypad |
| US7773139B2 (en) | 2004-04-16 | 2010-08-10 | Apple Inc. | Image sensor with photosensitive thin film transistors |
| JP2008523424A (en) * | 2004-12-09 | 2008-07-03 | アールピーオー プロプライエタリー リミテッド | Optical power distribution device |
| KR100640063B1 (en) * | 2005-02-18 | 2006-10-31 | 삼성전자주식회사 | Method for enhancing image considering to exterior illuminance and apparatus thereof |
| KR100800998B1 (en) | 2005-12-24 | 2008-02-11 | 삼성전자주식회사 | Apparatus and method for home network device controlling |
| KR100619584B1 (en) * | 2006-01-19 | 2006-09-01 | 주식회사 넥시오 | Detail position detecing method and error correcting method in touch panel system |
| WO2007122549A2 (en) * | 2006-04-21 | 2007-11-01 | Koninklijke Philips Electronics N.V. | Detection circuit for detecting movements of a movable object |
| CN101427205A (en) * | 2006-04-21 | 2009-05-06 | 皇家飞利浦电子股份有限公司 | Detection circuit for detecting movements of a movable object |
| US8022941B2 (en) | 2006-10-12 | 2011-09-20 | Disney Enterprises, Inc. | Multi-user touch screen |
| US7812827B2 (en) | 2007-01-03 | 2010-10-12 | Apple Inc. | Simultaneous sensing arrangement |
| US8493331B2 (en) | 2007-06-13 | 2013-07-23 | Apple Inc. | Touch detection using multiple simultaneous frequencies |
| US7973779B2 (en) * | 2007-10-26 | 2011-07-05 | Microsoft Corporation | Detecting ambient light levels in a vision system |
| JP5301240B2 (en) * | 2007-12-05 | 2013-09-25 | 株式会社ジャパンディスプレイウェスト | Display device |
| JP5378519B2 (en) * | 2008-08-07 | 2013-12-25 | ドラム，オウエン | Method and apparatus for detecting multi-touch events in optical touch sensitive devices |
| KR101548696B1 (en) * | 2008-08-07 | 2015-09-01 | 랩트 아이피 리미티드 | Optical control systems with feedback control |
| US9092092B2 (en) | 2008-08-07 | 2015-07-28 | Rapt Ip Limited | Detecting multitouch events in an optical touch-sensitive device using touch event templates |
| EP2338105B1 (en) | 2008-08-07 | 2012-12-19 | Owen Drumm | Optical control systems with modulated emitters |
| US8592697B2 (en) | 2008-09-10 | 2013-11-26 | Apple Inc. | Single-chip multi-stimulus sensor controller |
| US9606663B2 (en) | 2008-09-10 | 2017-03-28 | Apple Inc. | Multiple stimulation phase determination |
| US9348451B2 (en) * | 2008-09-10 | 2016-05-24 | Apple Inc. | Channel scan architecture for multiple stimulus multi-touch sensor panels |
| US9927924B2 (en) * | 2008-09-26 | 2018-03-27 | Apple Inc. | Differential sensing for a touch panel |
| CN101751184B (en) * | 2008-12-19 | 2013-02-20 | 深圳富泰宏精密工业有限公司 | Electronic device and input method thereof |
| TWI448926B (en) * | 2009-01-16 | 2014-08-11 | Chi Mei Comm Systems Inc | Electronic device and inputting method of the electronic device |
| KR101113516B1 (en) * | 2009-10-07 | 2012-02-29 | 삼성전기주식회사 | Electrode pattern for touch screen, driver for touch screen and touch screen |
| FR2955689B1 (en) * | 2010-01-28 | 2012-02-10 | Eurobraille | CONTROL DEVICE FOR A BRAILLE DISPLAY, BRAILLE DISPLAY AND CONTROL METHOD THEREFOR |
| US9103732B2 (en) * | 2010-05-25 | 2015-08-11 | Google Technology Holdings LLC | User computer device with temperature sensing capabilities and method of operating same |
| US9164620B2 (en) * | 2010-06-07 | 2015-10-20 | Apple Inc. | Touch sensing error compensation |
| JP2012053684A (en) * | 2010-09-01 | 2012-03-15 | Toshiba Tec Corp | Display input device and display input method |
| US20120105379A1 (en) * | 2010-11-03 | 2012-05-03 | Toshiba Tec Kabushiki Kaisha | Coordinate recognition apparatus and coordinate recognition method |
| US9310923B2 (en) | 2010-12-03 | 2016-04-12 | Apple Inc. | Input device for touch sensitive devices |
| US8638320B2 (en) | 2011-06-22 | 2014-01-28 | Apple Inc. | Stylus orientation detection |
| US9329703B2 (en) | 2011-06-22 | 2016-05-03 | Apple Inc. | Intelligent stylus |
| US8928635B2 (en) | 2011-06-22 | 2015-01-06 | Apple Inc. | Active stylus |
| US9024915B1 (en) * | 2011-07-15 | 2015-05-05 | Chelsea Trent | Keyboard with reflected light beam finger detection |
| TWI497376B (en) | 2011-07-22 | 2015-08-21 | Rapt Ip Ltd | Optical coupler assembly for use in an optical touch sensitive device |
| US9524060B2 (en) | 2012-07-13 | 2016-12-20 | Rapt Ip Limited | Low power operation of an optical touch-sensitive device for detecting multitouch events |
| US9557845B2 (en) | 2012-07-27 | 2017-01-31 | Apple Inc. | Input device for and method of communication with capacitive devices through frequency variation |
| US9176604B2 (en) | 2012-07-27 | 2015-11-03 | Apple Inc. | Stylus device |
| US9652090B2 (en) | 2012-07-27 | 2017-05-16 | Apple Inc. | Device for digital communication through capacitive coupling |
| US10048775B2 (en) | 2013-03-14 | 2018-08-14 | Apple Inc. | Stylus detection and demodulation |
| US9939935B2 (en) | 2013-07-31 | 2018-04-10 | Apple Inc. | Scan engine for touch controller architecture |
| JP5943021B2 (en) * | 2014-03-10 | 2016-06-29 | コニカミノルタ株式会社 | Touch panel input device |
| US10061450B2 (en) | 2014-12-04 | 2018-08-28 | Apple Inc. | Coarse scan and targeted active mode scan for touch |
| DK3032386T3 (en) * | 2014-12-10 | 2020-05-25 | Pr Electronics As | OPTICAL KEYBOARD FOR EXPLOSIVE PLACES |
| US10474277B2 (en) | 2016-05-31 | 2019-11-12 | Apple Inc. | Position-based stylus communication |
| JP2018010439A (en) * | 2016-07-13 | 2018-01-18 | 株式会社リコー | Coordinate detection device |
| CN111813274A (en) * | 2020-06-23 | 2020-10-23 | 中国电子科技集团公司第五十五研究所 | Wide-temperature infrared touch device and temperature compensation method thereof |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS51128296A (en) * | 1975-05-01 | 1976-11-09 | Seiko Instr & Electronics Ltd | Indicator |
| US5003505A (en) * | 1984-05-07 | 1991-03-26 | Hewlett-Packard Company | Touchscreen/keyboard scanner |
| US4943806A (en) * | 1984-06-18 | 1990-07-24 | Carroll Touch Inc. | Touch input device having digital ambient light sampling |
| KR900000089B1 (en) * | 1984-08-23 | 1990-01-19 | 알프스덴기 가부시기가이샤 | Touch pannel input devices |
| US4707689A (en) * | 1985-03-25 | 1987-11-17 | AT&T Information Systems Inc. American Telephone & Telegraph Company | Adaptive thresholding scheme for optically-based touch screens |
| JPS62163138A (en) * | 1986-01-13 | 1987-07-18 | Nippon Denso Co Ltd | Display switch signal generator for picture display system |
| US4893120A (en) * | 1986-11-26 | 1990-01-09 | Digital Electronics Corporation | Touch panel using modulated light |
| US5053757A (en) * | 1987-06-04 | 1991-10-01 | Tektronix, Inc. | Touch panel with adaptive noise reduction |
| US4855590A (en) * | 1987-06-25 | 1989-08-08 | Amp Incorporated | Infrared touch input device having ambient compensation |
| US5164714A (en) * | 1988-06-20 | 1992-11-17 | Amp Incorporated | Modulated touch entry system and method with synchronous detection |
| US4988983A (en) * | 1988-09-02 | 1991-01-29 | Carroll Touch, Incorporated | Touch entry system with ambient compensation and programmable amplification |
| US5179369A (en) * | 1989-12-06 | 1993-01-12 | Dale Electronics, Inc. | Touch panel and method for controlling same |
| FR2659462A1 (en) * | 1990-03-06 | 1991-09-13 | Cegelec | Control arrangement for process management system |
| US5105186A (en) * | 1990-05-25 | 1992-04-14 | Hewlett-Packard Company | Lcd touch screen |
-
1992
- 1992-05-27 US US07/889,780 patent/US5355149A/en not_active Expired - Fee Related
-
1993
- 1993-05-27 CA CA002096977A patent/CA2096977A1/en not_active Abandoned
- 1993-05-27 EP EP93108594A patent/EP0572009A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| US5355149A (en) | 1994-10-11 |
| EP0572009A1 (en) | 1993-12-01 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Discontinued |