CA1326276C - Optical motion sensor - Google Patents
Optical motion sensorInfo
- Publication number
- CA1326276C CA1326276C CA000557750A CA557750A CA1326276C CA 1326276 C CA1326276 C CA 1326276C CA 000557750 A CA000557750 A CA 000557750A CA 557750 A CA557750 A CA 557750A CA 1326276 C CA1326276 C CA 1326276C
- Authority
- CA
- Canada
- Prior art keywords
- energy
- sensing
- signal
- detection
- region
- 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.)
- Expired - Fee Related
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V8/00—Prospecting or detecting by optical means
- G01V8/10—Detecting, e.g. by using light barriers
- G01V8/20—Detecting, e.g. by using light barriers using multiple transmitters or receivers
Abstract
ABSTRACT OF THE DISCLOSURE
A novel apparatus is provided herein for sensing either motion or the presence of an object, or both, within a detection region. That apparatus includes a first emitting means for generating and emitting a first beam of energy towards the detection region and also towards a sensing region. A second emitting means is provided for generating and emitting a second beam of energy complementary to the first beam of energy. Sensing means at a sensing region receive and sum the energies of the first and second beams of energy to produce a corresponding sensing signal having a constant signal portion and a time varying signal portion. Filter means coupled to the sensing means block the constant signal portion of the sum and pass the time varying signal portion. Detection means convert the time varying signal portion to a proportional detection signal indicative of either the motion or the object. Modulating means are responsive to the detection signal for modulating one of the beams of energy to null the time varying signal portion.
A novel apparatus is provided herein for sensing either motion or the presence of an object, or both, within a detection region. That apparatus includes a first emitting means for generating and emitting a first beam of energy towards the detection region and also towards a sensing region. A second emitting means is provided for generating and emitting a second beam of energy complementary to the first beam of energy. Sensing means at a sensing region receive and sum the energies of the first and second beams of energy to produce a corresponding sensing signal having a constant signal portion and a time varying signal portion. Filter means coupled to the sensing means block the constant signal portion of the sum and pass the time varying signal portion. Detection means convert the time varying signal portion to a proportional detection signal indicative of either the motion or the object. Modulating means are responsive to the detection signal for modulating one of the beams of energy to null the time varying signal portion.
Description
1 326~76 This invention generally relates to motion sensing apparatus ; and more particularly to an optical motion sensor for sensing at least one of motion or presence of an object within a sensing region.
Motion sensors find widespread use in many industrial, commercial, and consumer markets. For industry and commerce, a primary use is for security by detecting human motion in a factory, office, or home. For commercial establishments, e.g.
department of grocery stoxes, motion sensors are used to open doors automatically upon sensing the approach of a person or ..
other moving object. Other uses are varied, including the counting of objects on a conveyor belt.
Motion sensors presently available include mechanical switches, magnetic sensors, photoelectric sensors, acoustic sensors, microwave sensors, and active and passive infrared sensors. Each of these technologies has strength and weaknesses.
Mechanical switches that are commonly found in doormats of grocery store doors are subject to wear from heavy and continual traffic thereon. Moreover, the doormats are often in an entry location and exposed to extreme weather such as heat, rain, and ~' snow which affects their reliability and lifetime. A further drawback of mechanical switches is that they require physical ;~ contact with the object to be sensed.
The other types of sensors mentioned above do not require physical contact with the moving object but have their own ~L
, - ~ , drawbacks. Magnetic sensors, for example, have a very short range and can detect only ferrous or magnetic materials. Acoustic sensors cannot be narrowly focused - 5 on a selected region of space and furthermore are ~- relatively expensive, quite large, and unable to adjust adequately to changes in background noise. Microwave sensors suffer from cross interference with the adjacent sensors and from wide beam dispersion. Photoelectric sensors, on the other hand, have too narrow a beam dispersion and require that the moving object break the beam. Although this may be an adequate technique for : opening doors, it can easily be circumvented by one engaged in unauthorized entry.
Recently much interest has been shown in infrared motion sensors. Such sensors take two forms: active sensors that include on or more emitting and one or more receiving elements, and passive sensors that comprise only receiving elements that sense a change in ambient infrared energy. Passive infrared sensors are inexpen-sive but are easily fooled by changes in ambient condi-tions. Furthermore, since they detect such energy from the body heat of a person, they may not detect persons wearing heavy clothing that trap body heat.
A drawback of active sensors is their reliance on a plurality of spaced-apart detectors and emitters. The additional emitters are necessary to provide sufficient B
.
.
- 2a -intensity for the detector to discrlminate against ^ ambient light. The higher density, however limits the sensitivity of the detector and thus :`
. ~ .
:', '.J
.s~j ',-', ; ' ~ ' '.
j .
'~ ' ., .
B
. , , ~ .:
.
.,... -the dynamic range of the sensor. A more serious drawback is the lack of automatic adjustment in response to changes in ambient conditions. For example, if a surface within the sensing region, e.g. the sidewalk, changes its reflective characteristics because of snowfall or rain, the amount of reflected infrared energy will change, causing the detector falsely to indicate the presence of an object. The same problem occurs if an object, e.g. a product display in a store is moved into the sensing region. The active -~ 10 sensor must be manually adjusted to compensate for the presence of the new object. Otherwise, the sensors are overly sensitive ~ to changes in energy and can easily saturate unless the energy ; received is decreased. This adjustment of the emitters, however, limits the range in which the sensor is effective.
lS An object, then, of one aspect of the present invention is to provide an improved optical motion sensor.
An object of a further aspect of the present invention is to provide such a sensor that can automatically adjust to sense movement near and far across a wide sensing region.
An object of yet another aspect of the present invention is to provide such a system that ignores changes in ambient light while sensing motion.
An object of still another aspect of the present invention is to provide such a system that can selectively sense motion or presence of an object within a sensing region of space.
.
: An object of a further aspect of the present invention -is to provide such a sensor that requires minimal energy, . is of minimal size, and can be produced for a low cost.
-~ 5 By one aspect of the present invention, an apparatus :~ is provided for sensing at least one of motion or the presence of an ohject within a detection region, . comprising: a first emitting means for generating and . emitting a first beam of energy towards the detection l~ 10 region and also towards a sensing region; a second emitting ~l means for generating and emitting a second beam of energy complementary to the first beam of energy towards the . sensing region; sensing means within the sensing region for . receiving and summing the energies of the first and second beams of energy to produce a corresponding sensing signal ~`- having a constant signal portion and a time varying signal portion; filter means coupled to the sensing means for blocking the constant signal portion of the sum and for . passing the time varying signal portion; detection means -- 20 for converting the time varying signal portion to a il,, :~ proportional detection signal indicative either of the ~ motion or of the presence of the object; and modulating .~ means responsive to the detection signal for modulating one ~, ` of the beams to null the time varying signal portion.
By another aspect of the present invention an apparatus is provided for sensing motion of an object within a detection region comprising: a first emitting . means for generating and emitting a first beam of energy ,, , .
, - ~ , . .
, ~ ' .
towards the detection region and also towards a sensing region; a second emitting means for generating and emitting a second beam of energy complementary to the first beam towards the sensing region; sensing means within the sensing region for receiving and summing the energies of the first and second beams of energy to produce a - corresponding sensing signal, the intensities of the first and second beams of energy being chosen to produce a sensing signal whose amplitude is constant when no motion is being sensed, and whose amplitude includes a time ;~ varying portion when motion is being sensed; filter means ; coupled to the sensing means for blocking the constant portion of the sensing signal, and for passing the time . . .
varying portion of the sensing signal; detection means for converting the time varying portion to a detection signal , indicative of motion; and modulating means responsive to ., the detection signal for modulating one of the beams to .~ null the time varying portion; the detection signal ~: 20 continuing until the modulating means causes the sensing 'A, means to produce a sensing signal with constant amplitude.
By yet another aspect of the present invention an apparatus is provided for sensing motion of an object ~: within a detection region, comprising: a first emitting means for emitting a first beam of energy towards the detection region and also towards a sensing region; a second emitting means for generating and emitting a second beam of energy complementary to the first beam of energy towards the sensing region; sensing means within the - -,`: :
. -~ 3~62I6 sensing region for receiving and summing the energies of the first and second beams of energy to produce a corresponding sensing signal having a constant signal portion and, while motion is being sensed, a time varyinq signal portion; filter means coupled to the sensing means for blocking the constant signal portion of the sum, and for passing the time varying signal portion; detection means for converting the time varying signal portion to a detection signal indicative of motion; and modulating means responsive to the detection signal for modulating one of the beams of energy to null the time varying signal portion of the sensing signal; the detection signal continuing until the modulating means causes the sensing means to produce a constant sensing signal.
Such apparatus may include means for pulsing the first and second beams of energy to complement each other.
Preferably, the duty cycle of the first beam is 1%.
The apparatus may be one in which the pulse of the first beam of energy is of shorter duration than the - complementary pulse of the second beam of energy. In such apparatus, the first pulsed beam of energy is projected to reflect off objects within a detection region before being sensed by the sensing means, and the second pulsed beam of ; 25 energy is directly transmitted to the sensing means. Inone aspect of such modified apparatus, the intensity of the first pulsed beam of energy is continuously modulated and the intensity of the second pulsed beam of energy is -~ .
maintained constant. In a second aspect of such apparatus, ~ the intensity of the second pulsed beam is continuously ; modulated and the intensity of the first pulsed beam is maintained constant.
The apparatus may include comparator means for comparing the detection signal against a reference signal as the value of the detection signal changes in response to changes in the response to the modulation of the sensor beam of energy, or in response to object motion or to object presence within the detection region, the comparator means confirming the detection signal if the value of the detection signal crosses the value of the reference signal.
The modulating means preferably is adapted to modulate the . .
second beam of energy at a rate proportional to the value of the detection signal. Still further preferably, the i modulating means comprises an integrator and a switch, the ~- integrator having faster and slower time constants to change the rate at which the beam is modulated, the switch being opened to utilize the slower time constant as long as the value of the detection signal is less than the value of the reference signal and the switch being closed to utilize .
the faster time constant if the value of the detection - signal crosses the value of the reference signal. The detection means preferably comprises a sampler for sampling output of the filter means synchronous with the emission of :~, the first pulsed beam of energy.
' ~' - ,, , .
':
- 7a _ 1 326276 .
The apparatus described above may further be one in which the first and second generating and emitting means each comprise light emitting diodes, and in which the sensing means comprises a photodiode. The photodiode is : preferably one that produces a sensing signal current. The apparatus still further preferably may be one in which the filter means includes an amplifier for converting the time varying signal current to a proportional signal voltage.
lo Such apparatus may further include delay means for delaying further transmission of the detection signal for a prede-termined time to filter out transient generated detection signals.
By still another aspect of this invention, an apparatus is provided for optically sensing at least one of presence and of motion of an object within a detection region, the apparatus comprising: a first light emitting diode for emitting a first pulsed beam of energy towards : the detection region and also towards a sensing region; a ' 20 second light emitting diode for emitting a second pulsed beam of energy towards the sensing region; a pulse generator for pulsing the first and second light emitting diodes to produce complementary pulsed beams of energy; a photodetector within the sensing region for receiving and summing the energies of the complementary pulsed beams of energy and for producing a sensing signal proportional to - the sum of the beam energies, the sensing signal having a constant signal portion and a time varying signal portion;
; sampling means for sampling the time varying signal portion ;' ' 1 ~
. ,,~ 5~
:..
.
'' ' ' ' ' ' ., .
, . ' .
- 7b 1 326276 synchronous with the first pulsed beam, and for converting the amplitude of the signal to a proportional detection signal; and modulating means coupled to the sampling means and responsive to the detection signal for modulating the second pulsed beam of energy at a rate which is proportional to the value of the detection signal to produce a constant sensing signal in the photodetector by : nulling the time varying signal portion, the detection lo signal continuing until the modulating means causes the ~: photodetector to produce a constant sensing signal.
By a still further aspect of this invention, an optical motion sensor is provided for sensing motion of an object within a detection region, comprising: a first light . .
`~ 15 emitting diode for emitting a first pulsed beam of energy towards the detection region and also towards a sensing region; a second light emitting diode for emitting a second pulsed beam of energy towards the sensing region; a pulse generator for pulsing the first and second light emitting diodes to produce complementary pulsed beams of energy; a photodetector within the sensing region for receiving and ;.~ summing the energies of the complementary pulsed beams and for producing a sensing signal proportional to the sum of the beam energies, the sensing signal having a constant signal portion and a time varying signal portion; an amplifier AC coupled to the photodiode for blocking the constant signal portion of the signal current, and for passing the time varying signal portion of the signal current; sampling means for sampling the time varying ~ . ~
.
, ' : , .
.. . . .. .
- 7c -signal portion synchronous with the first pulsed beam, and for converting the amplitude of the signal to a propor-tional DC detection signal; and modulating means coupled to the sampling means and responsive to the detection signal for modulating the second pulsed beam of energy at a rate .. which is proportional to the value of the detection signal to produce a constant sensing signal in the photodetector ; by nulling the time varying signal portion thereof, the . 10 detection signal continuing until the modulating means causes the photodetector to produce a constant sensing signal.
By yet a further aspect of this invention, a method is provided for sensing at least one of motion or the presence of an object within a detection region, comprising:
generating a first pulsed beam of energy to reflect off an ; object within the detection region; generating a second beam of energy complementary to the first pulsed beam of energy towards a sensing region; sensing the sum of the beam energies at a detection point within the sensing region; and generating a detection signal proportional to the difference between the beam energies.
By a still further aspect of this invention, a method :- is provided for sensing motion of an object within a detection region, comprising: generating a first pulsed beam of energy to reflect off objects with the detection region; generating a second beam complementary to the first pulsed beam of energy towards a sensing region; sensing the sum of the beam energies at the sensing region; generating .- ' .
", : .
, .
- 7d -a detection signal which are proportional to the change in the energy sum if the sum varies over time; and modulating, in response to a detection signal, the intensity of one of the pulsed beams of energy to null the time variance in the sum, the modulating thereby preventing further generation of the detection signal after motion within the region has - ceased.
In such method, the first and second beams are preferably pulsed to complement each other. Further in such method, the first pulsed beam of energy is trans-mitted to reflect off objects within the detection region - before being sensed, and the second pulsed beam of energy is sensed directly. Preferably the second pulsed beam of energy is modulated.
Still further, the method may include the step of ~ ceasing the modulating so that the detection signal - continues to indicate presence within the detection region.
In the accompanying drawings, FIG. 1 is a block diagram showing an optical motion sensor according to one embodiment of the invention in an operative setting;
- FIG. 2 is a block diagram of the optical motion sensor of FIG. 1;
, ,~
FIG. 3 is a schematic diagram showing one embodiment of the optical motion sensor;
FIG. 4 is a schematic diagram showing a second embodiment of the optical motion sensor configured as a presence sensor; and .
, , - 7e -FIGS 5A through 5G (which appear on the same sheet of -; drawings as FIGS. 1 and 2) are timing diagrams illustrating the operation of the optical motion sensor.
5FIG. 1 shows an optical motion sensor 10 according to the invention in an operative setting. The sensor lo 'f,~ includes a first emitting means, e.g., an infrared light ; emitting diode (LED) 12. LED 12 emits rays of a first beam of energy represented by dashed lines 13 into a detecting loregion of space. The beam reflects off objects in the detection region, e.g., stationary background object 14 and a moving object 16. The light energy reflected from these objects is sensed by a photodetector which is sensitive to the energy emitted by the emitting means, e.g., PIN diode 1518 in a sensing region. The diode 18 generates current in response to a signal which is proportional to the intensity of the light received. AS indicated in FIG. 1, the infrared rays from LED 12 generate several signal currents within photodiode 18. The quiescent signal current Iq is 20proportional to the quiescent reflected energy received when no motion is occurring within the region. That energy is represented by solid line 19. The target signal current It is proportional to the change in the reflected energy received by dashed line 21. The leakage signal current Il 25is proportional to the beam energy which inevitably is -directly incident on the photodiode 18. This energy is represented by dashed line 23.
- 1 32627~
- 7f -The first beam 13, 23 is not present continuously but is pulsed on and off. Complementary to the first pulsed beam 13, 23 emitted by LED 12 is a second pulsed beam 25 emitted by a generating and emitting means, e.g., an infrared LED 22. Although pulsing is utilized in this embodiment of the sensor 10, other well recognized techniques may also be used to generate complementary beams. For example, the two beams could be sinusoids that are 180 out of phase. By their complementary nature whatever the technique, the second beam 25 is present at the photodiode 18 when the first beam 13, 23 is absent and the first beam 13, 23 is present at the photodiode 18 when the second beam 25 is absent. The energy from the second beam 25 is provided to balance the infrared energy received by photodiode 18 from the LED 12. The second beam 25 is provided to balance the infrared energy received by photodiode 18 from the LED 12. The second beam 25 is of less intensity and is pulsed for a longer duration than the first beam 13,23 but is transmitted directly to the photodiode 18 as indicated by dashed line 25 to produce a proportional signal current Ib.
As well be described in detail hereafter, the intensity of the second beam 25 is modulated in response to the intensity of the first beam 13, 23 sensed by photodiode 18 to produce a substantially constant sensing signal as the two beams are pulsed on and off. This signal remains a constant or DC signal so long as an object 16 does not move within the sensing region to change the amount of - 7g -reflected energy at the photodiode 18. The photodiode 18 therefore sees a substantially DC energy signal when no motion is present. Filter means within the sensor 10 prevent the DC signal from generating a detection signal indicative of motion. If an object moves within the sensing region, the energy of the first pulsed beam reflected to the photodiode 18 changes, thereby introducing a time varying or AC signal portion into the sensing and producing the signal current It.
This change in current causes means within the sensor 10 to generate a detection signal indicative of motion.
Modulating means within the sensor 10 which are responsive to a detection signal then modulates the intensity of the second beam to null the time varying portion and establish a new constant sensing signal.
The optical motion sensor 10 may also be configured to -; be a presence detector by changing the rate at which the intensity of the second beam is modulated. The detection signal will be generated once an object enters the region until the object is removed sr until enough time elapses to produce a new sensing constant signal.
The sensor 10 as shown in FIG. 1 is configured in an autoreflective mode, with the first beam 13, 23 reflecting off objects within the detection region. The system, however, can be configured in other modes without departing from the principles of the invention. In a retroreflective ~ mode, a reflective surface, e.g., a mirror is spaced apart :
, ~f " ~
~ 1 326276 . - 7h from the LED 12 across a boundary. The angle of the first beam is narrowed and the beam is directed toward the mirror. The mirror increases the intensity of the energy reflected to the photodiode 18 and thereby considerably . extends the range of the sensor lo. The range may be . extended further in a transmissive mode, whereby the photodiode 18 and LED 22 are spaced apart from the LED 12.
The first beam 13, 23 is then directed across the boundary to the photodiode 18 but does not have to travel back the : distance to its origin. The transmissive mode thereby ; effectively doubles the range of the sensor 10.
Block Diagram ~:. FIG. 2 shows a block diagram of the elements , `~ 15 comprising sensor 10. A power supply 24 receives an ~ unregulated DC voltage V~g and provides a supply voltage V~
'''J'' for the sensor and a number of reference ~;
, .
.
. .
., :
' . ' ' ~ ';.
, , ~, ' .
"
voltages. The power supply 12 is of conventional design, an example of which will be described with reference to FIG. 3.
The LEDs 12 and 15 are pulsed in complementary fashion by a pulse generator 26 that provides a rectangular pulse waveform. The duty cycle illustrated is 1%, with the LED
12 pulsed during the presence of the pulse and the LED 22 pulsed during the absence of the pulse. It should be understood that the duty cycle may be varied within a range as will be described. The pulse portion of the waveform enables an LED driver 28 to drive LED 12. The LED driver 28 regulates the intensity of the first pulsed infrared beam emitted by LED 12 by reference to Vre~ a reference voltage that sets the current flowing through the LED.
:
The nonpulse portion of the waveform closes a switch 32 that enables the LED 22 to generate the second pulsed beam.
The photodiode 18 that senses and sums the energies of . .
- the complementary beams generates a proportional signal current Inot as the beams pulse on and off:
. .~
` 20Inet = I9 + I, + Il + Ib - The current Ine, is routed to detection means, e.g., a transresistance amplifier 34 for producing a high gain '~ signal voltage proportional to the sensing signal current.
- The amplifier 34 includes filtering means, e.g., blocking capacitors to filter out the DC signal portion and low frequency infrared signal fluctuations with the sensing signal. For example, changes in ambient infrared energy produced by switching on and off incandescent or .'' ,X
. ~ , .
.
fluorescent lights are filtered out before generation of the signal voltage at the output of amplifier 34. A high frequencv AC signal portion caused by reflections of the first beam from objects with the sensing region, however, will pass through the AC coupled amplifier 34.
The output of amplifier 34 is sampled by a sampler 36 that includes a low-pass filter. The sampler 36 samples the amplifier output during the presence of the first pulsed beam. The sampling converts the amplitude of a ~; 10 synchronous time varying or AC signal passed through the amplifier 34 to a proportional constant or DC detection signal. This proportional detection signal is routed via a feedback path 37 to an integrator 38. Integrator 38 modulates the second pulsed beam at a predetermined rate to , .
provide a voltage V~ proportional to the integral of the ~- detection signal voltage. The voltage V~ controls the current through LED 22 and thereby the energy of the second pulsed beam that is received by the photodiode 18. This feedback loop adjusts the output signal voltage of sampler 36 by changing V~ to produce a constant sensing signal at the photodiode 18. The rate of change of V~ is determined by the time constant of the integrator 38. V~ continues to change after a disturbance in the sensing region until the energy received at photodiode 18 is again constant and the time varying portion of the sensing signal is nulled. This nulling removes the proportional detection signal and the sampler output voltage becomes equal to the reference .
. ~
~ .
:
' 10 voltage vrcn under quiescent conditions. The net change therefore is in the level of V~.
The output voltage of sampler 36 is also compared against another reference voltage vreQ at comparator 42 to determine if movement has taken place. In a quiescent ; state, the sampler output voltage is equal to Vrcn which is in a predetermined relation to V,c~. If a relatively small change in reflected energy is sensed at photodiode 18, a proportional detection signal may be generated at the output of sampler 36, but the value of that signal may not be sufficient to trip comparator 42. However, integrator 38 will adjust V~ to change the intensity of the second .
- pulsed beam in response to generation of a detection signal. Within the time set by integrator 38, the change in reflected energy is compensated for and the sampler output voltage returns to the level of V,en, nulling the time varying signal and removing the detection signal. If the , change in reflected energy is such as to produce a ,., `- sufficiently strong detection signal at the output of amplifier 34, the signal will trip comparator 42 and be transmitted through the comparator to a time delay circuit -~ 44. Time delay circuit 44 is a delay circuit that delays the detection signal momentarily to filter out transient signals that may be caused by noise. A detection signal that survives the time delay circuit 44 is routed to output driver circuitry 46 for performing the desired sensor function, e.g., sounding an alarm or opening a door. The detection signal at the output of time delay circuit 44 is X
..
routed via feedback path 48 to the integrator 38 to change the integrator time constant. Alternatively, the feedback path could be from the output of comparator 42 to integrator 38. This shorter time constant accelerates the changing of Vin once the time delay circuit 44 confirms a detection signal. The energy in the second pulsed beam is thereby more rapidly modulated until the output voltage of sampler 36 is again at its quiescent level of V,cn.
FIGS. 3 and 4 are schematic diagrams of the sensor 10 for sensing motion and presence, respectively. It should be understood that the schematics shown herein are merely enabling illustrations of circuits that can be used to accomplish the functions of the block elements in FIG. 2 and are not meant as limitations on the scope of the ` 15 invention.
Referring to FIG. 3, each of the blocks referred to is outlined thereon. The power supply 24 includes a conventional voltage regulator 52 that receives the unregulated DC voltage Vunrcg on its input and generates a supply voltage Vcc as well as four reference voltages at its output. ~he amplitudes of the reference voltages decrease in the order shown across the series of resistors, with Vref4 ~r, at the highest voltage and Vr~f3 at the lowest voltage.
The pulse generator 26 receives Vcc and Vr~n from the power supply 24 and in turn generates a rectangular pulse waveform labelled as the signal CK in the figure. The generator 26 includes a comparator 54 to whose noninverting terminal Vren voltage is applied. Connected in feedback to ; ~X
:.
, : ~
:. . : . , '.
~ 12 l 32627~
the inverting terminal is the output of the comparator 54, which also charges a compacitor 56 via the supply voltage Vcc. Connected in parallel between the comparator output and capacitor 56 are resistor 58 and a transistor 62.
~ 5 Transistor 62 provides a fast charging path for charging - capacitor 56 while the output of the comparator is at Vcc.
The resistor 58 provides a slower discharge path for the capacitor while the comparator output is at ground. This fast charging and slow discharging produces a pulse waveform with a 1% duty cycle. In this embodiment, element ; values are such that the pulse duration during charging of ` capacitor 56 is 5 microseconds and the total period is .5 - milliseconds. The signal CK therefore is produced by the ,j toggling of comparator 54 as capacitor 56 charges and ~ 15 discharges according to two time constants.
. ., ,! The signal CK is routed to the LED driver 28 for producing the pulsing of LED 12. Driver 28 also receives the unregulated voltage Vunr~g and the reference voltage Vre~.
The current through LED 12 is regulated by a feedback loop ~^20 - that includes an integrator 64. The integrator 64 senses ~-the current via an analog switch 68 that is pulsed by the slgnal CK to sample the voltage across the resistor 66.
--The integrator 64 adjusts the voltage across the resistor 66 to the level of V,c~ to set the LED current to an exact - 25 amount. The integrator 64 acts by controlling the amount of base current in a PNP Darlington pair 70 that receives Vur~reg The voltage at the output of the integrator 64 contr ls the emitter current of a transistor 72. The ~, collector current of transistor 72 in turn controls the base current of the Darlington pair 70, which sources the current to LED 12. The signal CK simultaneously renders transistor 72 conductive and closes switch 68 to enable vunr~g to drive the LED 12 through the Darlington pair 70 as the integrator 64 samples the voltage across current limiting resistor 66. In this manner, the current through the LED 12 sets each pulse so that the LED emits a constant light intensity.
The LED 22 that emits the second pulsed beam is enabled on the complementary nonpulse portion of the pulse waveform by the switch 32, which in this embodiment comprises PNP transistor 74 in FIG. 3. The signal CK is applied to the base of transistor 74 to block current through the LED 22 during the presence of the pulse portion of the waveform. During the nonpulse portion, transistor 74 is conductive to enable the LED 22 to emit its beam.
The current through the LED 22, and therefore the . intensity of the second pulsed beam, is modulated in ~, response to the output of amplifier 34. The amplifier 34 is coupled to the photodiode 18 and includes a series of NPN transistors 76 for providing high gain to the photodiode signal current and for transforming the current to a signal voltage. The amplifier 34 is AC coupled to the photodiode by capacitors 78, 80, and 82. These capacitors are chosen for blocking the DC or constant signal portion of the signal current produced at the photodiode 18 and for filtering out low frequency signal fluctuation produced by X
14 l 32627~
changes in the ambient light. The amplifier also includes a fourth transistor 84 for providing additional gain to the output signal voltage. The DC operating points of the transistors 76 are set via a feedback path that includes the resistor 86. The output signal voltage of the amplifier therefore changes only with the change in the reflected energy sensed by the photodiode 18 and converted to a time varying signal current. Because of the operation of photodiode 18, an increase in photodiode current brought about by an increase in reflected energy causes a decrease ; in the output voltage of transistor 84. A decrease in photodiode current causes a corresponding voltage increase.
The sampler 36 includes a capacitor 87 and an analog switch 88 that has, at its input, Vrefl across a pull-up resistor. If the current in the photodiode 18 changes, an output signal voltage appears across capacitor 82 and the voltage sampled by switch 88 changes from V,~f,. This new output signal voltage is clocked by the signal CK through ~;
; switch 88 which converts the amplitude of the voltage to a proportional DC detection signal. The detection signal is routed through a low-pass filter comprising a resistor 89 , and capacitor 87 for filtering out unwanted high frequency signals and to a voltage follower 92 for buffering.
The output voltage of follower 92 will contain a detection signal if an AC signal has occurred in response to a change in energy received from LED 12 by the photodiode 18. To compensate for the change, the output is routed via path 37 to the noninverting input of an ., ,, .
., ., ~.
l 326276 operational amplifier 93 within integrator 38 for comparison against vr~fl. If the voltage at the output of follower 92 differs from V,efl, then Vin at the output of amplifier 93 changes to modulate the current through LED
22. This negative feedback loop will continue to adjust V~
until the sensing signal produced at photodiode 18 in ;` response to the received energy is again constant and no net AC signal appears at the output of the amplifier 34.
Integrator 38 includes, in addition to operational ~ 10 amplifier 93, a capacitor 98 connected in series with - parallel resistors 102 and 104 to provide two time ; constants over which to integrate the follower 92 output voltage. With the analog switch 106 open, the time constant is set by the larger resistor 102 which slows the rate at which V~ changes to adjust the LED 22 to its new level of intensity. With switch 106 closed, the time ., constant is set by resistor 104 in parallel with resistor 102, which increases the rate at which V~ changes. The . i second time constant is chosen once the time delay circuit 44 has confirmed the genuineness of the detection signal.
The output of follower 92 is routed as well to ;: comparator 42 which comprises, in this embodiment, a window comparator of separate comparators 108 and 112. These two comparators compare the output voltage of amplifier 92 against limiting reference voltages V,ef2 and VrCf4. If the output voltage contains a detection signal and becomes greater than reference voltage V~ef~ or less than reference ~, X
, .
1 326~76 15 a voltage V,c~2, the detection signal is assumed to indicate movement toward oraway from the LED 12 within the sensing region. The detection signal drops below V,c~2 if object 16 moves toward LED 12 and increases to exceed Vre~4 if object 16 moves away from the LED 12.
The outputs of comparators 108 and 112 are wire-ANDed and routed to the time delay 44 which comprises an inverting comparator 113 that delays, by way of capacitor 114, the transition of a detection signal for a predetermined time to filter out transient-generated detection signals. The hysteresis points are established by resistors 116 and 118 and V,ofl. If the detection signal generated by the comparators 108 and 112 is of sufficient duration to drop the voltage at the inverting input of comparator 113 below the lower hysteresis lever, then the . detection signal is confirmed to be genuine. The comparator 113 then generates sufficient voltage to drive the base of an NPN Darlington pair that comprises the output driver 46. As briefly discussed, the output voltage of the time delay 44 is also routed back to the analog switch 106 via a path 48 to switch the integrator 38 to the faster time constant.
FIG. 4 shows a second embodiment of the sensor 10 configured as a presence sensor. The differences between - the two are focused on the design of the integrator 38.
- For a presence sensor, the integrator utilizes a much ~ longer time constant when the amount of energy received by .''' X
:'.
:
., .
15 b 1 326276 the photodiode is increasing, indicating movement toward the LED 12, than when the amount of energy received by the photodiode is decreasing, indicating movement away from LED
12.
Referring to sampler 36, an object moving into the sensing region causes the output voltage of the voltage . .
follower 92 to drop proportionally as a detection signal.
This output is routed to the noninverting input of a comparator 120 for comparison against Vref,. With a sufficient decrease in the output voltage from follower 92, . ..
,~ the comparator 120 will change its state and back bias a r~ diode 122. The cutoff of current through the diode 122 : causes a capacitor 124 connected across amplifier 93 to discharge slowly through a high valued resistor 126, e.g., 100 megohms ..
, /
. ~, , .
.~
. - . ., ,:"
'-^, .
.
,. .
:,.
, ., ~`'' , .
''`
~ .
. X
.
' , .' ' ' .~ ~, ~ .
- 16 _ l 32 6 27 6 . .
and slowly raise the voltage V~ applied across LED 22.
In turn, the LED 22 increases the intensity of its beam until photodiode 18 again is producing a constant sensing ; 5 signal as it sums the energies of the two complementary beams. If the output voltage on the follower 92 increases because an object is moving away from the LED
12, the comparator 120 changes state to forward bias the ~ diode 122 with the supply voltage V through a much lower -~, 10 valued resistor 127 such as 100 kilohms. The output the ;
amplifier 93 decreases, decreasing V~ and lowering the .~
intensity of the beam being emitted by LED 22. The integrator 38 therefore compensates for changes in reflected energy much more quickly when an object moves . , , 15 away from the sensing region than when an object moves - into the sensing region. The purpose of this arrangement ` is to extend quickly the sensing range of the photodiode 18 once an object has moved further from the LED 12.
In contrast to the motion sensor FIG. 3, the presence sensor FIG. 4 has a single comparator 108 within ` the comparator element 42. Only one comparator is utilized because only movement toward the LED 12 is of concern. A power-on reset 128 is also provided to stabilize quickly the sensor 10 on power-up.
The following is a list of typical components that may be used in constructing the embodiments just described.
`:
., ,.
, ~: ` ' , 1 326~76 - 16a -Photodiode 18 SFH205 SIEMENsTM
LED 12 SFH404 SIEMENsTM
NPN transistors 2N5089 MOTOROLATM
PNP transistors MPS2907A MOTOROLATM
Operational amplifiers LM324 National Semi Comparators LM339 National Semi Analog switches CD4066 RCATM
Voltage regulator 7805 National Semi , .
~ B
~;
;, . . .
.. FIGS. 5A through 5G illustrate the generation of signal currents proportional to the summing of energies at the photodiode 18 as the sensor 10 adjusts to objects moving within its sensing region. In the quiescent state ,i 5 shown in FIGS. 5A and 5B, reflected energy from the first ; pulsed beam and energy that is leaked directly to the photodiode produce currents Iq and Il. The second LED 22 is modulated by integrator 38 to generate a complementary beam that produces the same current, labelled as Ib. The net lo current Inet shown in FIG. 5C therefore is constant as a DC
offset which is ignored by the amplifier 34 and no detection signal is produced.
When a moving object 16 enters the path of LED 12, the energy reflected to the photodiode 18 increases and produces a current I,shown in FIG. 5D. This signal current is summed with the currents Iq and Il during the presence of the first pulse to produce I'nC, as shown in FIG. 5E, a net time varying or AC signal over the period of the pulse waveform. A detection signal is then generated by ~, 20 amplifier 34. The detection signal is sampled by sampler ", 36 and if the signal survives the low-pass filter within the sampler 36, the signal is routed to integrator 38. The integrator 38 responds to this detection signal by modulating the second pulsed beam to produce a current I /b as shown in FIG. 5F. Assume now that object 16 has stopped moving and the amount of reflected energy is no longer changing over the time set by the slower time constant of ' ;' integrator 38, the LED 22 is acljusted until the intensity of its beam is such that:
IrDe~ b + I~ + Il + I, As shown in FIG. 5G, a new constant sensing signal I'ne, results. The AC portion of the signal I', is nulled as I'b is added to Ib. The detection signal thereby is nulled.
- In use of the sensor 10, a number of different sensors .
may be provided to cover a larger region. The sensing regions of each sensor may overlap without interfering with each other's signals because of the low duty cycle of the ;; `
first pulsed beam. With the 1~ duty cycle, there is but a . remote chance of the first pulsed beams being present simultaneously. The length of the duty cycle may be varied, but it must be sufficient in duration for the sampler 36 to sample the output of the amplifier 34 accurately.
Having illustrated and described the principles of the ; invention in preferred embodiments, it should be apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. For example, many of the analog elements in these embodiments may be replaced by digital elements.
Other types of amplifiers with high gain and filters can be substituted for amplifier 34. The integrator 38 could be replaced with a digital-to-analog converter. Additionally, the integrator may be designed such that, after the sensor circuit settles down after power-up, the feedback loop is broken to hold the state of the integrator constant as a '''. X
.
' " 1 326276 ; 18 a presence detector. Moreover, a manual feedback such as a potentiometer could be used to set the feedback in place of the automatic adjustment described.
,.
' , " ~
J
, , .,i .~ .i. .
. "
, ~ .
:, .
~.
', X
.
, . : .
, . ~' ' ' ' '
Motion sensors find widespread use in many industrial, commercial, and consumer markets. For industry and commerce, a primary use is for security by detecting human motion in a factory, office, or home. For commercial establishments, e.g.
department of grocery stoxes, motion sensors are used to open doors automatically upon sensing the approach of a person or ..
other moving object. Other uses are varied, including the counting of objects on a conveyor belt.
Motion sensors presently available include mechanical switches, magnetic sensors, photoelectric sensors, acoustic sensors, microwave sensors, and active and passive infrared sensors. Each of these technologies has strength and weaknesses.
Mechanical switches that are commonly found in doormats of grocery store doors are subject to wear from heavy and continual traffic thereon. Moreover, the doormats are often in an entry location and exposed to extreme weather such as heat, rain, and ~' snow which affects their reliability and lifetime. A further drawback of mechanical switches is that they require physical ;~ contact with the object to be sensed.
The other types of sensors mentioned above do not require physical contact with the moving object but have their own ~L
, - ~ , drawbacks. Magnetic sensors, for example, have a very short range and can detect only ferrous or magnetic materials. Acoustic sensors cannot be narrowly focused - 5 on a selected region of space and furthermore are ~- relatively expensive, quite large, and unable to adjust adequately to changes in background noise. Microwave sensors suffer from cross interference with the adjacent sensors and from wide beam dispersion. Photoelectric sensors, on the other hand, have too narrow a beam dispersion and require that the moving object break the beam. Although this may be an adequate technique for : opening doors, it can easily be circumvented by one engaged in unauthorized entry.
Recently much interest has been shown in infrared motion sensors. Such sensors take two forms: active sensors that include on or more emitting and one or more receiving elements, and passive sensors that comprise only receiving elements that sense a change in ambient infrared energy. Passive infrared sensors are inexpen-sive but are easily fooled by changes in ambient condi-tions. Furthermore, since they detect such energy from the body heat of a person, they may not detect persons wearing heavy clothing that trap body heat.
A drawback of active sensors is their reliance on a plurality of spaced-apart detectors and emitters. The additional emitters are necessary to provide sufficient B
.
.
- 2a -intensity for the detector to discrlminate against ^ ambient light. The higher density, however limits the sensitivity of the detector and thus :`
. ~ .
:', '.J
.s~j ',-', ; ' ~ ' '.
j .
'~ ' ., .
B
. , , ~ .:
.
.,... -the dynamic range of the sensor. A more serious drawback is the lack of automatic adjustment in response to changes in ambient conditions. For example, if a surface within the sensing region, e.g. the sidewalk, changes its reflective characteristics because of snowfall or rain, the amount of reflected infrared energy will change, causing the detector falsely to indicate the presence of an object. The same problem occurs if an object, e.g. a product display in a store is moved into the sensing region. The active -~ 10 sensor must be manually adjusted to compensate for the presence of the new object. Otherwise, the sensors are overly sensitive ~ to changes in energy and can easily saturate unless the energy ; received is decreased. This adjustment of the emitters, however, limits the range in which the sensor is effective.
lS An object, then, of one aspect of the present invention is to provide an improved optical motion sensor.
An object of a further aspect of the present invention is to provide such a sensor that can automatically adjust to sense movement near and far across a wide sensing region.
An object of yet another aspect of the present invention is to provide such a system that ignores changes in ambient light while sensing motion.
An object of still another aspect of the present invention is to provide such a system that can selectively sense motion or presence of an object within a sensing region of space.
.
: An object of a further aspect of the present invention -is to provide such a sensor that requires minimal energy, . is of minimal size, and can be produced for a low cost.
-~ 5 By one aspect of the present invention, an apparatus :~ is provided for sensing at least one of motion or the presence of an ohject within a detection region, . comprising: a first emitting means for generating and . emitting a first beam of energy towards the detection l~ 10 region and also towards a sensing region; a second emitting ~l means for generating and emitting a second beam of energy complementary to the first beam of energy towards the . sensing region; sensing means within the sensing region for . receiving and summing the energies of the first and second beams of energy to produce a corresponding sensing signal ~`- having a constant signal portion and a time varying signal portion; filter means coupled to the sensing means for blocking the constant signal portion of the sum and for . passing the time varying signal portion; detection means -- 20 for converting the time varying signal portion to a il,, :~ proportional detection signal indicative either of the ~ motion or of the presence of the object; and modulating .~ means responsive to the detection signal for modulating one ~, ` of the beams to null the time varying signal portion.
By another aspect of the present invention an apparatus is provided for sensing motion of an object within a detection region comprising: a first emitting . means for generating and emitting a first beam of energy ,, , .
, - ~ , . .
, ~ ' .
towards the detection region and also towards a sensing region; a second emitting means for generating and emitting a second beam of energy complementary to the first beam towards the sensing region; sensing means within the sensing region for receiving and summing the energies of the first and second beams of energy to produce a - corresponding sensing signal, the intensities of the first and second beams of energy being chosen to produce a sensing signal whose amplitude is constant when no motion is being sensed, and whose amplitude includes a time ;~ varying portion when motion is being sensed; filter means ; coupled to the sensing means for blocking the constant portion of the sensing signal, and for passing the time . . .
varying portion of the sensing signal; detection means for converting the time varying portion to a detection signal , indicative of motion; and modulating means responsive to ., the detection signal for modulating one of the beams to .~ null the time varying portion; the detection signal ~: 20 continuing until the modulating means causes the sensing 'A, means to produce a sensing signal with constant amplitude.
By yet another aspect of the present invention an apparatus is provided for sensing motion of an object ~: within a detection region, comprising: a first emitting means for emitting a first beam of energy towards the detection region and also towards a sensing region; a second emitting means for generating and emitting a second beam of energy complementary to the first beam of energy towards the sensing region; sensing means within the - -,`: :
. -~ 3~62I6 sensing region for receiving and summing the energies of the first and second beams of energy to produce a corresponding sensing signal having a constant signal portion and, while motion is being sensed, a time varyinq signal portion; filter means coupled to the sensing means for blocking the constant signal portion of the sum, and for passing the time varying signal portion; detection means for converting the time varying signal portion to a detection signal indicative of motion; and modulating means responsive to the detection signal for modulating one of the beams of energy to null the time varying signal portion of the sensing signal; the detection signal continuing until the modulating means causes the sensing means to produce a constant sensing signal.
Such apparatus may include means for pulsing the first and second beams of energy to complement each other.
Preferably, the duty cycle of the first beam is 1%.
The apparatus may be one in which the pulse of the first beam of energy is of shorter duration than the - complementary pulse of the second beam of energy. In such apparatus, the first pulsed beam of energy is projected to reflect off objects within a detection region before being sensed by the sensing means, and the second pulsed beam of ; 25 energy is directly transmitted to the sensing means. Inone aspect of such modified apparatus, the intensity of the first pulsed beam of energy is continuously modulated and the intensity of the second pulsed beam of energy is -~ .
maintained constant. In a second aspect of such apparatus, ~ the intensity of the second pulsed beam is continuously ; modulated and the intensity of the first pulsed beam is maintained constant.
The apparatus may include comparator means for comparing the detection signal against a reference signal as the value of the detection signal changes in response to changes in the response to the modulation of the sensor beam of energy, or in response to object motion or to object presence within the detection region, the comparator means confirming the detection signal if the value of the detection signal crosses the value of the reference signal.
The modulating means preferably is adapted to modulate the . .
second beam of energy at a rate proportional to the value of the detection signal. Still further preferably, the i modulating means comprises an integrator and a switch, the ~- integrator having faster and slower time constants to change the rate at which the beam is modulated, the switch being opened to utilize the slower time constant as long as the value of the detection signal is less than the value of the reference signal and the switch being closed to utilize .
the faster time constant if the value of the detection - signal crosses the value of the reference signal. The detection means preferably comprises a sampler for sampling output of the filter means synchronous with the emission of :~, the first pulsed beam of energy.
' ~' - ,, , .
':
- 7a _ 1 326276 .
The apparatus described above may further be one in which the first and second generating and emitting means each comprise light emitting diodes, and in which the sensing means comprises a photodiode. The photodiode is : preferably one that produces a sensing signal current. The apparatus still further preferably may be one in which the filter means includes an amplifier for converting the time varying signal current to a proportional signal voltage.
lo Such apparatus may further include delay means for delaying further transmission of the detection signal for a prede-termined time to filter out transient generated detection signals.
By still another aspect of this invention, an apparatus is provided for optically sensing at least one of presence and of motion of an object within a detection region, the apparatus comprising: a first light emitting diode for emitting a first pulsed beam of energy towards : the detection region and also towards a sensing region; a ' 20 second light emitting diode for emitting a second pulsed beam of energy towards the sensing region; a pulse generator for pulsing the first and second light emitting diodes to produce complementary pulsed beams of energy; a photodetector within the sensing region for receiving and summing the energies of the complementary pulsed beams of energy and for producing a sensing signal proportional to - the sum of the beam energies, the sensing signal having a constant signal portion and a time varying signal portion;
; sampling means for sampling the time varying signal portion ;' ' 1 ~
. ,,~ 5~
:..
.
'' ' ' ' ' ' ., .
, . ' .
- 7b 1 326276 synchronous with the first pulsed beam, and for converting the amplitude of the signal to a proportional detection signal; and modulating means coupled to the sampling means and responsive to the detection signal for modulating the second pulsed beam of energy at a rate which is proportional to the value of the detection signal to produce a constant sensing signal in the photodetector by : nulling the time varying signal portion, the detection lo signal continuing until the modulating means causes the ~: photodetector to produce a constant sensing signal.
By a still further aspect of this invention, an optical motion sensor is provided for sensing motion of an object within a detection region, comprising: a first light . .
`~ 15 emitting diode for emitting a first pulsed beam of energy towards the detection region and also towards a sensing region; a second light emitting diode for emitting a second pulsed beam of energy towards the sensing region; a pulse generator for pulsing the first and second light emitting diodes to produce complementary pulsed beams of energy; a photodetector within the sensing region for receiving and ;.~ summing the energies of the complementary pulsed beams and for producing a sensing signal proportional to the sum of the beam energies, the sensing signal having a constant signal portion and a time varying signal portion; an amplifier AC coupled to the photodiode for blocking the constant signal portion of the signal current, and for passing the time varying signal portion of the signal current; sampling means for sampling the time varying ~ . ~
.
, ' : , .
.. . . .. .
- 7c -signal portion synchronous with the first pulsed beam, and for converting the amplitude of the signal to a propor-tional DC detection signal; and modulating means coupled to the sampling means and responsive to the detection signal for modulating the second pulsed beam of energy at a rate .. which is proportional to the value of the detection signal to produce a constant sensing signal in the photodetector ; by nulling the time varying signal portion thereof, the . 10 detection signal continuing until the modulating means causes the photodetector to produce a constant sensing signal.
By yet a further aspect of this invention, a method is provided for sensing at least one of motion or the presence of an object within a detection region, comprising:
generating a first pulsed beam of energy to reflect off an ; object within the detection region; generating a second beam of energy complementary to the first pulsed beam of energy towards a sensing region; sensing the sum of the beam energies at a detection point within the sensing region; and generating a detection signal proportional to the difference between the beam energies.
By a still further aspect of this invention, a method :- is provided for sensing motion of an object within a detection region, comprising: generating a first pulsed beam of energy to reflect off objects with the detection region; generating a second beam complementary to the first pulsed beam of energy towards a sensing region; sensing the sum of the beam energies at the sensing region; generating .- ' .
", : .
, .
- 7d -a detection signal which are proportional to the change in the energy sum if the sum varies over time; and modulating, in response to a detection signal, the intensity of one of the pulsed beams of energy to null the time variance in the sum, the modulating thereby preventing further generation of the detection signal after motion within the region has - ceased.
In such method, the first and second beams are preferably pulsed to complement each other. Further in such method, the first pulsed beam of energy is trans-mitted to reflect off objects within the detection region - before being sensed, and the second pulsed beam of energy is sensed directly. Preferably the second pulsed beam of energy is modulated.
Still further, the method may include the step of ~ ceasing the modulating so that the detection signal - continues to indicate presence within the detection region.
In the accompanying drawings, FIG. 1 is a block diagram showing an optical motion sensor according to one embodiment of the invention in an operative setting;
- FIG. 2 is a block diagram of the optical motion sensor of FIG. 1;
, ,~
FIG. 3 is a schematic diagram showing one embodiment of the optical motion sensor;
FIG. 4 is a schematic diagram showing a second embodiment of the optical motion sensor configured as a presence sensor; and .
, , - 7e -FIGS 5A through 5G (which appear on the same sheet of -; drawings as FIGS. 1 and 2) are timing diagrams illustrating the operation of the optical motion sensor.
5FIG. 1 shows an optical motion sensor 10 according to the invention in an operative setting. The sensor lo 'f,~ includes a first emitting means, e.g., an infrared light ; emitting diode (LED) 12. LED 12 emits rays of a first beam of energy represented by dashed lines 13 into a detecting loregion of space. The beam reflects off objects in the detection region, e.g., stationary background object 14 and a moving object 16. The light energy reflected from these objects is sensed by a photodetector which is sensitive to the energy emitted by the emitting means, e.g., PIN diode 1518 in a sensing region. The diode 18 generates current in response to a signal which is proportional to the intensity of the light received. AS indicated in FIG. 1, the infrared rays from LED 12 generate several signal currents within photodiode 18. The quiescent signal current Iq is 20proportional to the quiescent reflected energy received when no motion is occurring within the region. That energy is represented by solid line 19. The target signal current It is proportional to the change in the reflected energy received by dashed line 21. The leakage signal current Il 25is proportional to the beam energy which inevitably is -directly incident on the photodiode 18. This energy is represented by dashed line 23.
- 1 32627~
- 7f -The first beam 13, 23 is not present continuously but is pulsed on and off. Complementary to the first pulsed beam 13, 23 emitted by LED 12 is a second pulsed beam 25 emitted by a generating and emitting means, e.g., an infrared LED 22. Although pulsing is utilized in this embodiment of the sensor 10, other well recognized techniques may also be used to generate complementary beams. For example, the two beams could be sinusoids that are 180 out of phase. By their complementary nature whatever the technique, the second beam 25 is present at the photodiode 18 when the first beam 13, 23 is absent and the first beam 13, 23 is present at the photodiode 18 when the second beam 25 is absent. The energy from the second beam 25 is provided to balance the infrared energy received by photodiode 18 from the LED 12. The second beam 25 is provided to balance the infrared energy received by photodiode 18 from the LED 12. The second beam 25 is of less intensity and is pulsed for a longer duration than the first beam 13,23 but is transmitted directly to the photodiode 18 as indicated by dashed line 25 to produce a proportional signal current Ib.
As well be described in detail hereafter, the intensity of the second beam 25 is modulated in response to the intensity of the first beam 13, 23 sensed by photodiode 18 to produce a substantially constant sensing signal as the two beams are pulsed on and off. This signal remains a constant or DC signal so long as an object 16 does not move within the sensing region to change the amount of - 7g -reflected energy at the photodiode 18. The photodiode 18 therefore sees a substantially DC energy signal when no motion is present. Filter means within the sensor 10 prevent the DC signal from generating a detection signal indicative of motion. If an object moves within the sensing region, the energy of the first pulsed beam reflected to the photodiode 18 changes, thereby introducing a time varying or AC signal portion into the sensing and producing the signal current It.
This change in current causes means within the sensor 10 to generate a detection signal indicative of motion.
Modulating means within the sensor 10 which are responsive to a detection signal then modulates the intensity of the second beam to null the time varying portion and establish a new constant sensing signal.
The optical motion sensor 10 may also be configured to -; be a presence detector by changing the rate at which the intensity of the second beam is modulated. The detection signal will be generated once an object enters the region until the object is removed sr until enough time elapses to produce a new sensing constant signal.
The sensor 10 as shown in FIG. 1 is configured in an autoreflective mode, with the first beam 13, 23 reflecting off objects within the detection region. The system, however, can be configured in other modes without departing from the principles of the invention. In a retroreflective ~ mode, a reflective surface, e.g., a mirror is spaced apart :
, ~f " ~
~ 1 326276 . - 7h from the LED 12 across a boundary. The angle of the first beam is narrowed and the beam is directed toward the mirror. The mirror increases the intensity of the energy reflected to the photodiode 18 and thereby considerably . extends the range of the sensor lo. The range may be . extended further in a transmissive mode, whereby the photodiode 18 and LED 22 are spaced apart from the LED 12.
The first beam 13, 23 is then directed across the boundary to the photodiode 18 but does not have to travel back the : distance to its origin. The transmissive mode thereby ; effectively doubles the range of the sensor 10.
Block Diagram ~:. FIG. 2 shows a block diagram of the elements , `~ 15 comprising sensor 10. A power supply 24 receives an ~ unregulated DC voltage V~g and provides a supply voltage V~
'''J'' for the sensor and a number of reference ~;
, .
.
. .
., :
' . ' ' ~ ';.
, , ~, ' .
"
voltages. The power supply 12 is of conventional design, an example of which will be described with reference to FIG. 3.
The LEDs 12 and 15 are pulsed in complementary fashion by a pulse generator 26 that provides a rectangular pulse waveform. The duty cycle illustrated is 1%, with the LED
12 pulsed during the presence of the pulse and the LED 22 pulsed during the absence of the pulse. It should be understood that the duty cycle may be varied within a range as will be described. The pulse portion of the waveform enables an LED driver 28 to drive LED 12. The LED driver 28 regulates the intensity of the first pulsed infrared beam emitted by LED 12 by reference to Vre~ a reference voltage that sets the current flowing through the LED.
:
The nonpulse portion of the waveform closes a switch 32 that enables the LED 22 to generate the second pulsed beam.
The photodiode 18 that senses and sums the energies of . .
- the complementary beams generates a proportional signal current Inot as the beams pulse on and off:
. .~
` 20Inet = I9 + I, + Il + Ib - The current Ine, is routed to detection means, e.g., a transresistance amplifier 34 for producing a high gain '~ signal voltage proportional to the sensing signal current.
- The amplifier 34 includes filtering means, e.g., blocking capacitors to filter out the DC signal portion and low frequency infrared signal fluctuations with the sensing signal. For example, changes in ambient infrared energy produced by switching on and off incandescent or .'' ,X
. ~ , .
.
fluorescent lights are filtered out before generation of the signal voltage at the output of amplifier 34. A high frequencv AC signal portion caused by reflections of the first beam from objects with the sensing region, however, will pass through the AC coupled amplifier 34.
The output of amplifier 34 is sampled by a sampler 36 that includes a low-pass filter. The sampler 36 samples the amplifier output during the presence of the first pulsed beam. The sampling converts the amplitude of a ~; 10 synchronous time varying or AC signal passed through the amplifier 34 to a proportional constant or DC detection signal. This proportional detection signal is routed via a feedback path 37 to an integrator 38. Integrator 38 modulates the second pulsed beam at a predetermined rate to , .
provide a voltage V~ proportional to the integral of the ~- detection signal voltage. The voltage V~ controls the current through LED 22 and thereby the energy of the second pulsed beam that is received by the photodiode 18. This feedback loop adjusts the output signal voltage of sampler 36 by changing V~ to produce a constant sensing signal at the photodiode 18. The rate of change of V~ is determined by the time constant of the integrator 38. V~ continues to change after a disturbance in the sensing region until the energy received at photodiode 18 is again constant and the time varying portion of the sensing signal is nulled. This nulling removes the proportional detection signal and the sampler output voltage becomes equal to the reference .
. ~
~ .
:
' 10 voltage vrcn under quiescent conditions. The net change therefore is in the level of V~.
The output voltage of sampler 36 is also compared against another reference voltage vreQ at comparator 42 to determine if movement has taken place. In a quiescent ; state, the sampler output voltage is equal to Vrcn which is in a predetermined relation to V,c~. If a relatively small change in reflected energy is sensed at photodiode 18, a proportional detection signal may be generated at the output of sampler 36, but the value of that signal may not be sufficient to trip comparator 42. However, integrator 38 will adjust V~ to change the intensity of the second .
- pulsed beam in response to generation of a detection signal. Within the time set by integrator 38, the change in reflected energy is compensated for and the sampler output voltage returns to the level of V,en, nulling the time varying signal and removing the detection signal. If the , change in reflected energy is such as to produce a ,., `- sufficiently strong detection signal at the output of amplifier 34, the signal will trip comparator 42 and be transmitted through the comparator to a time delay circuit -~ 44. Time delay circuit 44 is a delay circuit that delays the detection signal momentarily to filter out transient signals that may be caused by noise. A detection signal that survives the time delay circuit 44 is routed to output driver circuitry 46 for performing the desired sensor function, e.g., sounding an alarm or opening a door. The detection signal at the output of time delay circuit 44 is X
..
routed via feedback path 48 to the integrator 38 to change the integrator time constant. Alternatively, the feedback path could be from the output of comparator 42 to integrator 38. This shorter time constant accelerates the changing of Vin once the time delay circuit 44 confirms a detection signal. The energy in the second pulsed beam is thereby more rapidly modulated until the output voltage of sampler 36 is again at its quiescent level of V,cn.
FIGS. 3 and 4 are schematic diagrams of the sensor 10 for sensing motion and presence, respectively. It should be understood that the schematics shown herein are merely enabling illustrations of circuits that can be used to accomplish the functions of the block elements in FIG. 2 and are not meant as limitations on the scope of the ` 15 invention.
Referring to FIG. 3, each of the blocks referred to is outlined thereon. The power supply 24 includes a conventional voltage regulator 52 that receives the unregulated DC voltage Vunrcg on its input and generates a supply voltage Vcc as well as four reference voltages at its output. ~he amplitudes of the reference voltages decrease in the order shown across the series of resistors, with Vref4 ~r, at the highest voltage and Vr~f3 at the lowest voltage.
The pulse generator 26 receives Vcc and Vr~n from the power supply 24 and in turn generates a rectangular pulse waveform labelled as the signal CK in the figure. The generator 26 includes a comparator 54 to whose noninverting terminal Vren voltage is applied. Connected in feedback to ; ~X
:.
, : ~
:. . : . , '.
~ 12 l 32627~
the inverting terminal is the output of the comparator 54, which also charges a compacitor 56 via the supply voltage Vcc. Connected in parallel between the comparator output and capacitor 56 are resistor 58 and a transistor 62.
~ 5 Transistor 62 provides a fast charging path for charging - capacitor 56 while the output of the comparator is at Vcc.
The resistor 58 provides a slower discharge path for the capacitor while the comparator output is at ground. This fast charging and slow discharging produces a pulse waveform with a 1% duty cycle. In this embodiment, element ; values are such that the pulse duration during charging of ` capacitor 56 is 5 microseconds and the total period is .5 - milliseconds. The signal CK therefore is produced by the ,j toggling of comparator 54 as capacitor 56 charges and ~ 15 discharges according to two time constants.
. ., ,! The signal CK is routed to the LED driver 28 for producing the pulsing of LED 12. Driver 28 also receives the unregulated voltage Vunr~g and the reference voltage Vre~.
The current through LED 12 is regulated by a feedback loop ~^20 - that includes an integrator 64. The integrator 64 senses ~-the current via an analog switch 68 that is pulsed by the slgnal CK to sample the voltage across the resistor 66.
--The integrator 64 adjusts the voltage across the resistor 66 to the level of V,c~ to set the LED current to an exact - 25 amount. The integrator 64 acts by controlling the amount of base current in a PNP Darlington pair 70 that receives Vur~reg The voltage at the output of the integrator 64 contr ls the emitter current of a transistor 72. The ~, collector current of transistor 72 in turn controls the base current of the Darlington pair 70, which sources the current to LED 12. The signal CK simultaneously renders transistor 72 conductive and closes switch 68 to enable vunr~g to drive the LED 12 through the Darlington pair 70 as the integrator 64 samples the voltage across current limiting resistor 66. In this manner, the current through the LED 12 sets each pulse so that the LED emits a constant light intensity.
The LED 22 that emits the second pulsed beam is enabled on the complementary nonpulse portion of the pulse waveform by the switch 32, which in this embodiment comprises PNP transistor 74 in FIG. 3. The signal CK is applied to the base of transistor 74 to block current through the LED 22 during the presence of the pulse portion of the waveform. During the nonpulse portion, transistor 74 is conductive to enable the LED 22 to emit its beam.
The current through the LED 22, and therefore the . intensity of the second pulsed beam, is modulated in ~, response to the output of amplifier 34. The amplifier 34 is coupled to the photodiode 18 and includes a series of NPN transistors 76 for providing high gain to the photodiode signal current and for transforming the current to a signal voltage. The amplifier 34 is AC coupled to the photodiode by capacitors 78, 80, and 82. These capacitors are chosen for blocking the DC or constant signal portion of the signal current produced at the photodiode 18 and for filtering out low frequency signal fluctuation produced by X
14 l 32627~
changes in the ambient light. The amplifier also includes a fourth transistor 84 for providing additional gain to the output signal voltage. The DC operating points of the transistors 76 are set via a feedback path that includes the resistor 86. The output signal voltage of the amplifier therefore changes only with the change in the reflected energy sensed by the photodiode 18 and converted to a time varying signal current. Because of the operation of photodiode 18, an increase in photodiode current brought about by an increase in reflected energy causes a decrease ; in the output voltage of transistor 84. A decrease in photodiode current causes a corresponding voltage increase.
The sampler 36 includes a capacitor 87 and an analog switch 88 that has, at its input, Vrefl across a pull-up resistor. If the current in the photodiode 18 changes, an output signal voltage appears across capacitor 82 and the voltage sampled by switch 88 changes from V,~f,. This new output signal voltage is clocked by the signal CK through ~;
; switch 88 which converts the amplitude of the voltage to a proportional DC detection signal. The detection signal is routed through a low-pass filter comprising a resistor 89 , and capacitor 87 for filtering out unwanted high frequency signals and to a voltage follower 92 for buffering.
The output voltage of follower 92 will contain a detection signal if an AC signal has occurred in response to a change in energy received from LED 12 by the photodiode 18. To compensate for the change, the output is routed via path 37 to the noninverting input of an ., ,, .
., ., ~.
l 326276 operational amplifier 93 within integrator 38 for comparison against vr~fl. If the voltage at the output of follower 92 differs from V,efl, then Vin at the output of amplifier 93 changes to modulate the current through LED
22. This negative feedback loop will continue to adjust V~
until the sensing signal produced at photodiode 18 in ;` response to the received energy is again constant and no net AC signal appears at the output of the amplifier 34.
Integrator 38 includes, in addition to operational ~ 10 amplifier 93, a capacitor 98 connected in series with - parallel resistors 102 and 104 to provide two time ; constants over which to integrate the follower 92 output voltage. With the analog switch 106 open, the time constant is set by the larger resistor 102 which slows the rate at which V~ changes to adjust the LED 22 to its new level of intensity. With switch 106 closed, the time ., constant is set by resistor 104 in parallel with resistor 102, which increases the rate at which V~ changes. The . i second time constant is chosen once the time delay circuit 44 has confirmed the genuineness of the detection signal.
The output of follower 92 is routed as well to ;: comparator 42 which comprises, in this embodiment, a window comparator of separate comparators 108 and 112. These two comparators compare the output voltage of amplifier 92 against limiting reference voltages V,ef2 and VrCf4. If the output voltage contains a detection signal and becomes greater than reference voltage V~ef~ or less than reference ~, X
, .
1 326~76 15 a voltage V,c~2, the detection signal is assumed to indicate movement toward oraway from the LED 12 within the sensing region. The detection signal drops below V,c~2 if object 16 moves toward LED 12 and increases to exceed Vre~4 if object 16 moves away from the LED 12.
The outputs of comparators 108 and 112 are wire-ANDed and routed to the time delay 44 which comprises an inverting comparator 113 that delays, by way of capacitor 114, the transition of a detection signal for a predetermined time to filter out transient-generated detection signals. The hysteresis points are established by resistors 116 and 118 and V,ofl. If the detection signal generated by the comparators 108 and 112 is of sufficient duration to drop the voltage at the inverting input of comparator 113 below the lower hysteresis lever, then the . detection signal is confirmed to be genuine. The comparator 113 then generates sufficient voltage to drive the base of an NPN Darlington pair that comprises the output driver 46. As briefly discussed, the output voltage of the time delay 44 is also routed back to the analog switch 106 via a path 48 to switch the integrator 38 to the faster time constant.
FIG. 4 shows a second embodiment of the sensor 10 configured as a presence sensor. The differences between - the two are focused on the design of the integrator 38.
- For a presence sensor, the integrator utilizes a much ~ longer time constant when the amount of energy received by .''' X
:'.
:
., .
15 b 1 326276 the photodiode is increasing, indicating movement toward the LED 12, than when the amount of energy received by the photodiode is decreasing, indicating movement away from LED
12.
Referring to sampler 36, an object moving into the sensing region causes the output voltage of the voltage . .
follower 92 to drop proportionally as a detection signal.
This output is routed to the noninverting input of a comparator 120 for comparison against Vref,. With a sufficient decrease in the output voltage from follower 92, . ..
,~ the comparator 120 will change its state and back bias a r~ diode 122. The cutoff of current through the diode 122 : causes a capacitor 124 connected across amplifier 93 to discharge slowly through a high valued resistor 126, e.g., 100 megohms ..
, /
. ~, , .
.~
. - . ., ,:"
'-^, .
.
,. .
:,.
, ., ~`'' , .
''`
~ .
. X
.
' , .' ' ' .~ ~, ~ .
- 16 _ l 32 6 27 6 . .
and slowly raise the voltage V~ applied across LED 22.
In turn, the LED 22 increases the intensity of its beam until photodiode 18 again is producing a constant sensing ; 5 signal as it sums the energies of the two complementary beams. If the output voltage on the follower 92 increases because an object is moving away from the LED
12, the comparator 120 changes state to forward bias the ~ diode 122 with the supply voltage V through a much lower -~, 10 valued resistor 127 such as 100 kilohms. The output the ;
amplifier 93 decreases, decreasing V~ and lowering the .~
intensity of the beam being emitted by LED 22. The integrator 38 therefore compensates for changes in reflected energy much more quickly when an object moves . , , 15 away from the sensing region than when an object moves - into the sensing region. The purpose of this arrangement ` is to extend quickly the sensing range of the photodiode 18 once an object has moved further from the LED 12.
In contrast to the motion sensor FIG. 3, the presence sensor FIG. 4 has a single comparator 108 within ` the comparator element 42. Only one comparator is utilized because only movement toward the LED 12 is of concern. A power-on reset 128 is also provided to stabilize quickly the sensor 10 on power-up.
The following is a list of typical components that may be used in constructing the embodiments just described.
`:
., ,.
, ~: ` ' , 1 326~76 - 16a -Photodiode 18 SFH205 SIEMENsTM
LED 12 SFH404 SIEMENsTM
NPN transistors 2N5089 MOTOROLATM
PNP transistors MPS2907A MOTOROLATM
Operational amplifiers LM324 National Semi Comparators LM339 National Semi Analog switches CD4066 RCATM
Voltage regulator 7805 National Semi , .
~ B
~;
;, . . .
.. FIGS. 5A through 5G illustrate the generation of signal currents proportional to the summing of energies at the photodiode 18 as the sensor 10 adjusts to objects moving within its sensing region. In the quiescent state ,i 5 shown in FIGS. 5A and 5B, reflected energy from the first ; pulsed beam and energy that is leaked directly to the photodiode produce currents Iq and Il. The second LED 22 is modulated by integrator 38 to generate a complementary beam that produces the same current, labelled as Ib. The net lo current Inet shown in FIG. 5C therefore is constant as a DC
offset which is ignored by the amplifier 34 and no detection signal is produced.
When a moving object 16 enters the path of LED 12, the energy reflected to the photodiode 18 increases and produces a current I,shown in FIG. 5D. This signal current is summed with the currents Iq and Il during the presence of the first pulse to produce I'nC, as shown in FIG. 5E, a net time varying or AC signal over the period of the pulse waveform. A detection signal is then generated by ~, 20 amplifier 34. The detection signal is sampled by sampler ", 36 and if the signal survives the low-pass filter within the sampler 36, the signal is routed to integrator 38. The integrator 38 responds to this detection signal by modulating the second pulsed beam to produce a current I /b as shown in FIG. 5F. Assume now that object 16 has stopped moving and the amount of reflected energy is no longer changing over the time set by the slower time constant of ' ;' integrator 38, the LED 22 is acljusted until the intensity of its beam is such that:
IrDe~ b + I~ + Il + I, As shown in FIG. 5G, a new constant sensing signal I'ne, results. The AC portion of the signal I', is nulled as I'b is added to Ib. The detection signal thereby is nulled.
- In use of the sensor 10, a number of different sensors .
may be provided to cover a larger region. The sensing regions of each sensor may overlap without interfering with each other's signals because of the low duty cycle of the ;; `
first pulsed beam. With the 1~ duty cycle, there is but a . remote chance of the first pulsed beams being present simultaneously. The length of the duty cycle may be varied, but it must be sufficient in duration for the sampler 36 to sample the output of the amplifier 34 accurately.
Having illustrated and described the principles of the ; invention in preferred embodiments, it should be apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. For example, many of the analog elements in these embodiments may be replaced by digital elements.
Other types of amplifiers with high gain and filters can be substituted for amplifier 34. The integrator 38 could be replaced with a digital-to-analog converter. Additionally, the integrator may be designed such that, after the sensor circuit settles down after power-up, the feedback loop is broken to hold the state of the integrator constant as a '''. X
.
' " 1 326276 ; 18 a presence detector. Moreover, a manual feedback such as a potentiometer could be used to set the feedback in place of the automatic adjustment described.
,.
' , " ~
J
, , .,i .~ .i. .
. "
, ~ .
:, .
~.
', X
.
, . : .
, . ~' ' ' ' '
Claims (23)
1. An apparatus for sensing at least one of motion or the presence of an object within a detection region, comprising:
a first emitting means for generating and emitting a first beam of energy towards said detection region and also towards a sensing region;
a second emitting means for generating and emitting a second beam of energy complementary to said first beam of energy towards said sensing region;
sensing means within said sensing region for receiving and summing the energies of said first and second beams of energy to produce a corresponding sensing signal having a constant signal portion and a time varying signal portion;
filter means coupled to said sensing means for blocking said constant signal portion of said sum and for passing said time varying signal portion;
detection means for converting said time varying signal portion to a proportional detection signal indicative either of said motion or of the presence of said object; and modulating means responsive to said detection signal for modulating one of said beams to null the time varying signal portion.
a first emitting means for generating and emitting a first beam of energy towards said detection region and also towards a sensing region;
a second emitting means for generating and emitting a second beam of energy complementary to said first beam of energy towards said sensing region;
sensing means within said sensing region for receiving and summing the energies of said first and second beams of energy to produce a corresponding sensing signal having a constant signal portion and a time varying signal portion;
filter means coupled to said sensing means for blocking said constant signal portion of said sum and for passing said time varying signal portion;
detection means for converting said time varying signal portion to a proportional detection signal indicative either of said motion or of the presence of said object; and modulating means responsive to said detection signal for modulating one of said beams to null the time varying signal portion.
2. An apparatus for sensing motion of an object within a detection region comprising:
a first emitting means for generating and emitting a first beam of energy towards said detection region and also towards a sensing region;
a second emitting means for generating and emitting a second beam of energy complementary to said first beam towards said sensing region;
sensing means within said sensing region for receiving and summing the energies of said first and second beams of energy to produce a corresponding sensing signal, the intensities of said first and second beams of energy being chosen to produce a sensing signal whose amplitude is constant when no motion is being sensed, and whose amplitude includes a time varying portion when motion is being sensed;
filter means coupled to said sensing means for blocking said constant portion of said sensing signal, and for passing said time varying portion of said sensing signal;
detection means for converting said time varying portion to a detection signal indicative of motion; and modulating means responsive to said detection signal for modulating one of said beams to null said time varying portion;
said detection signal continuing until said modulating means causes said sensing means to produce a sensing signal with constant amplitude.
a first emitting means for generating and emitting a first beam of energy towards said detection region and also towards a sensing region;
a second emitting means for generating and emitting a second beam of energy complementary to said first beam towards said sensing region;
sensing means within said sensing region for receiving and summing the energies of said first and second beams of energy to produce a corresponding sensing signal, the intensities of said first and second beams of energy being chosen to produce a sensing signal whose amplitude is constant when no motion is being sensed, and whose amplitude includes a time varying portion when motion is being sensed;
filter means coupled to said sensing means for blocking said constant portion of said sensing signal, and for passing said time varying portion of said sensing signal;
detection means for converting said time varying portion to a detection signal indicative of motion; and modulating means responsive to said detection signal for modulating one of said beams to null said time varying portion;
said detection signal continuing until said modulating means causes said sensing means to produce a sensing signal with constant amplitude.
3. An apparatus for sensing motion of an object within a detection region, comprising:
a first emitting means for emitting a first beam of energy towards said detection region and also towards a sensing region;
a second emitting means for generating and emitting a second beam of energy complementary to the first beam of energy towards said sensing region;
sensing means within said sensing region for receiving and summing the energies of said first and second beams of energy to produce a corresponding sensing signal having a constant signal portion and, while motion is being sensed, a time varying signal portion;
filter means coupled to said sensing means for blocking said constant signal portion of said sum, and for passing said time varying signal portion;
detection means for converting said time varying signal portion to a detection signal indicative of motion;
and modulating means responsive to said detection signal for modulating one of said beams of energy to null said time varying signal portion of said sensing signal;
said detection signal continuing until said modulating means causes said sensing means to produce a constant sensing signal.
a first emitting means for emitting a first beam of energy towards said detection region and also towards a sensing region;
a second emitting means for generating and emitting a second beam of energy complementary to the first beam of energy towards said sensing region;
sensing means within said sensing region for receiving and summing the energies of said first and second beams of energy to produce a corresponding sensing signal having a constant signal portion and, while motion is being sensed, a time varying signal portion;
filter means coupled to said sensing means for blocking said constant signal portion of said sum, and for passing said time varying signal portion;
detection means for converting said time varying signal portion to a detection signal indicative of motion;
and modulating means responsive to said detection signal for modulating one of said beams of energy to null said time varying signal portion of said sensing signal;
said detection signal continuing until said modulating means causes said sensing means to produce a constant sensing signal.
4. The apparatus of claims 1, 2 or 3 including means for pulsing said first and second beams of energy to complement each other.
5. The apparatus of claims 1, 2 or 3 including: means for pulsing said first and second beams of energy to complement each other; and further in which a duty cycle of said first beam is 1%.
6. The apparatus of claims 1, 2 or 3 including: means for pulsing said first and second beams of energy to complement each other; and further in which said pulse of said first beam of energy is of shorter duration than the complementary pulse of the second beam of energy, said first pulsed beam of energy being projected to reflect off objects within said sensing region before sensing by said sensing means, and said second pulsed beam of energy being directly transmitted to said sensing means.
7. The apparatus of claims 1, 2 or 3 including: means for pulsing said first and second beams of energy to complement each other; further in which said pulse of said first beam of energy is of shorter duration than the complementary pulse of said second beam of energy, said first pulsed beam of energy being projected to reflect off objects within said sensing region before sensing by said sensing means, and said second pulsed beam of energy being directly transmitted to said sensing means; and still further in which the intensity of said second pulsed beam is modulated, and in which the intensity of said first pulsed beam of energy is maintained constant.
8. The apparatus of claims 1, 2 or 3 including: means for pulsing said first and second beams of energy to complement each other; further in which said pulse of said first beam of energy is of shorter duration than the complementary pulse of said second beam of energy, said first pulsed beam of energy being projected to reflect off objects within a detection region before sensing by said sensing means, and said second pulsed beam of energy being directly transmitted to said sensing means; still further in which the intensity of said second pulsed beam is modulated, and in which the intensity of said first pulsed beam of energy is maintained constant; and still further including comparator means for comparing said detection signal against a reference signal as the value of said detection signal changes in response to changes in the response to the modulation of said second pulsed beam of energy or in response to object motion or object presence within said detection region, said comparator means confirming said detection signal if the value of said detection signal crosses the value of said reference signal.
9. The apparatus of claims 1, 2 or 3 including: means for pulsing said first and second beams of energy to complement each other; further in which said pulse of said first beam of energy is of shorter duration than the complementary pulse of said second beam of energy, said first pulsed beam of energy being projected to reflect off objects within said detection region before sensing by said sensing means, said second pulsed beam of energy being directly transmitted to said sensing means; still further in which the intensity of said second pulsed beam is modulated, and in which the intensity of said first pulsed beam of energy is maintained constant; and still further in which said modulating means is adapted to modulate said second beam of energy at a rate proportional to the value of said detection signal.
10. The apparatus of claims 1, 2 or 3 including means for pulsing said first and second beams of energy to complement each other; further in which said pulse of said first beam of energy is of shorter duration than the complementary pulse of said second beam of energy, said first pulsed beam of energy being projected to reflect off objects within said detection region before sensing by said sensing means, and said second pulsed beam of energy being directly transmitted to said sensing means; further in which the intensity of said second pulsed beam of energy is modulated and the intensity of said first pulsed beam of energy is maintained constant; and still further in which said modulating means comprises an integrator and a switch, said integrator having faster and slower time constants to change the rate at which said second beam of energy is modulated, said switch being opened to utilize said slower time constant as long as the value of said detection signal is less than the value of said reference signal, and said switch being closed to utilize said faster time constant if the value of said detection signal crosses the value of said reference signal.
11. The apparatus of claims 1, 2 or 3 including:
means for pulsing said first and second beams of energy to complement each other; further in which said pulse of said first beam of energy is of shorter duration than the complementary pulse of said second beam of energy, said first pulsed beam of energy being projected to reflect off objects within said detection region before sensing by said sensing means, and said second pulsed beam of energy being directly transmitted to said sensing means; still further in which the intensity of said second pulsed beam is modulated, and in which the intensity of said first pulsed beam of energy is maintained constant; and still further in which said detection means comprises a sampler for sampling output of said filter means synchronous with the emission of said first pulsed beam of energy.
means for pulsing said first and second beams of energy to complement each other; further in which said pulse of said first beam of energy is of shorter duration than the complementary pulse of said second beam of energy, said first pulsed beam of energy being projected to reflect off objects within said detection region before sensing by said sensing means, and said second pulsed beam of energy being directly transmitted to said sensing means; still further in which the intensity of said second pulsed beam is modulated, and in which the intensity of said first pulsed beam of energy is maintained constant; and still further in which said detection means comprises a sampler for sampling output of said filter means synchronous with the emission of said first pulsed beam of energy.
12. The apparatus of claims 1, 2 or 3 including:
means for pulsing said first and second beams of energy to complement each other; further in which said pulse of said first beam of energy is of shorter duration than the complementary pulse of said second beam of energy, said first pulsed beam being projected to reflect off said objects within said detection region before sensing by said sensing means, and said second pulsed beam being directly transmitted to said sensing means; and still further in which the intensity of said second pulsed beam of energy is continually modulated and in which the intensity of said first pulsed beam of energy is maintained constant.
means for pulsing said first and second beams of energy to complement each other; further in which said pulse of said first beam of energy is of shorter duration than the complementary pulse of said second beam of energy, said first pulsed beam being projected to reflect off said objects within said detection region before sensing by said sensing means, and said second pulsed beam being directly transmitted to said sensing means; and still further in which the intensity of said second pulsed beam of energy is continually modulated and in which the intensity of said first pulsed beam of energy is maintained constant.
13. The apparatus of claims 1, 2 or 3 in which said first and second generating and emitting means comprise light emitting diodes; and in which said sensing means comprises a photodiode.
14. The apparatus of claims 1, 2 or 3 in which said first and second generating and emitting means comprise light emitting diodes; further in which said sensing means comprises a photodiode that produces a sensing signal current; and still further in which said filter means includes an amplifier for converting said time varying signal current to a proportional signal voltage.
15. The apparatus of claims 1, 2 or 3 including delay means for delaying further transmission of the detection signal for a predetermined time to filter out transient generated detection signals.
16. An apparatus for optically sensing at least one of presence and of motion of an object within a detection region, said apparatus comprising:
a first light emitting diode for emitting a first pulsed beam of energy towards said detection region and also towards a sensing region;
a second light emitting diode for emitting a second pulsed beam of energy towards said sensing region;
a pulse generator for pulsing said first and second light emitting diodes to produce complementary pulsed beams of energy;
a photodetector within said sensing region for receiving and summing the energies of said complementary pulsed beams of energy and for producing a sensing signal proportional to the sum of said beam energies, said sensing signal having a constant signal portion and a time varying signal portion;
sampling means for sampling said time varying signal portion synchronous with said first pulsed beam, and for converting the amplitude of said signal to a proportional detection signal; and modulating means coupled to said sampling means and responsive to said detection signal for modulating said second pulsed beam of energy at a rate proportional to the value of said detection signal to produce a constant sensing signal in said photodetector by nulling said time varying signal portion, said detection signal continuing until said modulating means causes said photodetector to produce a constant sensing signal.
a first light emitting diode for emitting a first pulsed beam of energy towards said detection region and also towards a sensing region;
a second light emitting diode for emitting a second pulsed beam of energy towards said sensing region;
a pulse generator for pulsing said first and second light emitting diodes to produce complementary pulsed beams of energy;
a photodetector within said sensing region for receiving and summing the energies of said complementary pulsed beams of energy and for producing a sensing signal proportional to the sum of said beam energies, said sensing signal having a constant signal portion and a time varying signal portion;
sampling means for sampling said time varying signal portion synchronous with said first pulsed beam, and for converting the amplitude of said signal to a proportional detection signal; and modulating means coupled to said sampling means and responsive to said detection signal for modulating said second pulsed beam of energy at a rate proportional to the value of said detection signal to produce a constant sensing signal in said photodetector by nulling said time varying signal portion, said detection signal continuing until said modulating means causes said photodetector to produce a constant sensing signal.
17. An optical motion sensor for sensing motion of an object within a detection region, comprising:
a first light emitting diode for emitting a first pulsed beam of energy towards said detection region and also towards a sensing region;
a second light emitting diode for emitting a second pulsed beam of energy towards said sensing region;
a pulse generator for pulsing said first and second light emitting diodes to produce complementary pulsed beams of energy;
a photodetector within said sensing region for receiving and summing the energies of said complementary pulsed beams and for producing a sensing signal propor-tional to the sum of said beam energies, said sensing signal having a constant signal portion and a time varying signal portion;
an amplifier AC coupled to said photodiode for blocking said constant signal portion of said signal current, and for passing said time varying signal portion of said signal current;
sampling means for sampling said time varying signal portion synchronous with said first pulsed beam, and for converting the amplitude of said signal to a proportional DC detection signal; and modulating means coupled to said sampling means and responsive to said detection signal for modulating said second pulsed beam of energy at a rate proportional to the value of said detection signal to produce a constant sensing signal in said photodetector by nulling said time varying signal portion thereof, said detection signal continuing until said modulating means causes said photodetector to produce a constant sensing signal.
a first light emitting diode for emitting a first pulsed beam of energy towards said detection region and also towards a sensing region;
a second light emitting diode for emitting a second pulsed beam of energy towards said sensing region;
a pulse generator for pulsing said first and second light emitting diodes to produce complementary pulsed beams of energy;
a photodetector within said sensing region for receiving and summing the energies of said complementary pulsed beams and for producing a sensing signal propor-tional to the sum of said beam energies, said sensing signal having a constant signal portion and a time varying signal portion;
an amplifier AC coupled to said photodiode for blocking said constant signal portion of said signal current, and for passing said time varying signal portion of said signal current;
sampling means for sampling said time varying signal portion synchronous with said first pulsed beam, and for converting the amplitude of said signal to a proportional DC detection signal; and modulating means coupled to said sampling means and responsive to said detection signal for modulating said second pulsed beam of energy at a rate proportional to the value of said detection signal to produce a constant sensing signal in said photodetector by nulling said time varying signal portion thereof, said detection signal continuing until said modulating means causes said photodetector to produce a constant sensing signal.
18. A method for sensing at least one of motion or presence of an object within a detection region, comprising:
generating a first pulsed beam of energy to reflect off an object within said detection region;
generating a second beam of energy complementary to said first pulsed beam of energy towards said sensing region;
sensing the sum of said beam energies at a detection point within a sensing region; and generating a detection signal proportional to the difference between said beam energies.
generating a first pulsed beam of energy to reflect off an object within said detection region;
generating a second beam of energy complementary to said first pulsed beam of energy towards said sensing region;
sensing the sum of said beam energies at a detection point within a sensing region; and generating a detection signal proportional to the difference between said beam energies.
19. A method for sensing motion of an object within a detection region, comprising:
generating a first pulsed beam of energy to reflect off objects within said detection region;
generating a second beam complementary to said first pulsed beam of energy towards said sensing region;
sensing the sum of said beam energies at a sensing point;
generating a detection signal proportional to the change in the energy sum if said sum varies over time; and modulating, in response to a detection signal, the intensity of one of said pulsed beams of energy to null the time variance in said sum, said modulating thereby preventing further generation of said detection signal after motion within said region has ceased.
generating a first pulsed beam of energy to reflect off objects within said detection region;
generating a second beam complementary to said first pulsed beam of energy towards said sensing region;
sensing the sum of said beam energies at a sensing point;
generating a detection signal proportional to the change in the energy sum if said sum varies over time; and modulating, in response to a detection signal, the intensity of one of said pulsed beams of energy to null the time variance in said sum, said modulating thereby preventing further generation of said detection signal after motion within said region has ceased.
20. The method of claims 18 or 19 in which said first and second beams of energy are pulsed to complement each other.
21. The method of claims 18 or 19 in which said first pulsed beam of energy is transmitted to reflect off objects within said detection region before being sensed; and in which said second pulsed beam of energy is sensed directly.
22. The method of claims 18 or 19 in which said first pulsed beam of energy is transmitted to reflect off objects within said detection region before being sensed; further in which said second pulsed beam is sensed directly; and further in which said second pulsed beam of energy is modulated.
23. The method of claims 18 or 19, additionally comprising the steps of: first continuing said modulating so that subsequent time variance in said sum is nulled to prevent further generation of said detection signal after motion within said detection region has ceased; and then ceasing said modulating so that said detection signal continues to indicate presence within the detection region.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/009,777 US4736097A (en) | 1987-02-02 | 1987-02-02 | Optical motion sensor |
| US009,777 | 1987-02-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1326276C true CA1326276C (en) | 1994-01-18 |
Family
ID=21739651
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000557750A Expired - Fee Related CA1326276C (en) | 1987-02-02 | 1988-01-29 | Optical motion sensor |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4736097A (en) |
| CA (1) | CA1326276C (en) |
Families Citing this family (118)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0616087B2 (en) * | 1987-09-22 | 1994-03-02 | スタンレー電気株式会社 | Photoelectric detector |
| US4879461A (en) * | 1988-04-25 | 1989-11-07 | Harald Philipp | Energy field sensor using summing means |
| JP2860571B2 (en) * | 1989-12-20 | 1999-02-24 | 株式会社トプコン | Photodetection method and device therefor |
| US5442168A (en) * | 1991-10-15 | 1995-08-15 | Interactive Light, Inc. | Dynamically-activated optical instrument for producing control signals having a self-calibration means |
| FR2685497B1 (en) * | 1991-12-20 | 1996-05-31 | Inrets | METHOD FOR DETERMINING THE OCCUPANCY OF A PORTION OF TRACK SUITABLE FOR TRAVELING BY BODIES OF ANY KIND. |
| US5955854A (en) * | 1992-09-29 | 1999-09-21 | Prospects Corporation | Power driven venting of a vehicle |
| US5286967A (en) * | 1992-12-04 | 1994-02-15 | Stanley Home Automation | Method and apparatus for self-biasing a light beam obstacle detector with a bias light |
| US5559496A (en) * | 1993-05-19 | 1996-09-24 | Dubats; William C. | Remote patrol system |
| US5378893A (en) * | 1993-10-26 | 1995-01-03 | General Electric Company | Radiation event qualifier for positron emission tomography |
| US5508511A (en) * | 1994-05-24 | 1996-04-16 | Interactive Light, Inc. | Arrangement for and method of detecting an object in an area subject to environmental variations |
| GB9420315D0 (en) * | 1994-10-08 | 1995-03-08 | Pilkington Perkin Elmer Ltd | Head-up displays |
| US5621205A (en) * | 1994-11-10 | 1997-04-15 | Tri-Tronics Company, Inc. | Photoelectric sensor having an enhanced dynamic range control circuit |
| US5481266A (en) * | 1994-11-17 | 1996-01-02 | Davis; Warren F. | Autodyne motion sensor |
| US5594238A (en) * | 1995-02-17 | 1997-01-14 | Albert J. Endruschat | Touchless switch which discriminates between motion intended to toggle the switch and other forms of motion |
| US5913727A (en) * | 1995-06-02 | 1999-06-22 | Ahdoot; Ned | Interactive movement and contact simulation game |
| US5825413A (en) * | 1995-11-01 | 1998-10-20 | Thomson Consumer Electronics, Inc. | Infrared surveillance system with controlled video recording |
| US5684458A (en) * | 1996-02-26 | 1997-11-04 | Napco Security Systems, Inc. | Microwave sensor with adjustable sampling frequency based on environmental conditions |
| US6384402B1 (en) * | 1998-04-29 | 2002-05-07 | Automated Merchandising Systems | Optical vend-sensing system for control of vending machine |
| KR100319548B1 (en) * | 1999-03-22 | 2002-01-05 | 김재한 | Apparatus for Detecting and Anouncing Direction of an Object Passing Through a Gate |
| US6157024A (en) * | 1999-06-03 | 2000-12-05 | Prospects, Corp. | Method and apparatus for improving the performance of an aperture monitoring system |
| US6225904B1 (en) | 1999-09-29 | 2001-05-01 | Refrigerator Manufacturers, Inc. | Automatic sliding door system for refrigerator unit |
| US6279687B1 (en) * | 1999-10-01 | 2001-08-28 | Otis Elevator Company | Method and system for detecting objects in a detection zone using modulated means |
| US6386326B2 (en) * | 1999-10-01 | 2002-05-14 | Otis Elevator Company | Method and system for detecting objects in a detection zone using modulated means |
| US6693273B1 (en) | 2000-05-02 | 2004-02-17 | Prospects, Corp. | Method and apparatus for monitoring a powered vent opening with a multifaceted sensor system |
| US8149048B1 (en) | 2000-10-26 | 2012-04-03 | Cypress Semiconductor Corporation | Apparatus and method for programmable power management in a programmable analog circuit block |
| US8176296B2 (en) | 2000-10-26 | 2012-05-08 | Cypress Semiconductor Corporation | Programmable microcontroller architecture |
| US7765095B1 (en) | 2000-10-26 | 2010-07-27 | Cypress Semiconductor Corporation | Conditional branching in an in-circuit emulation system |
| US6724220B1 (en) | 2000-10-26 | 2004-04-20 | Cyress Semiconductor Corporation | Programmable microcontroller architecture (mixed analog/digital) |
| US8160864B1 (en) | 2000-10-26 | 2012-04-17 | Cypress Semiconductor Corporation | In-circuit emulator and pod synchronized boot |
| US8103496B1 (en) | 2000-10-26 | 2012-01-24 | Cypress Semicondutor Corporation | Breakpoint control in an in-circuit emulation system |
| US6661410B2 (en) | 2001-09-07 | 2003-12-09 | Microsoft Corporation | Capacitive sensing and data input device power management |
| US7406674B1 (en) | 2001-10-24 | 2008-07-29 | Cypress Semiconductor Corporation | Method and apparatus for generating microcontroller configuration information |
| US8078970B1 (en) | 2001-11-09 | 2011-12-13 | Cypress Semiconductor Corporation | Graphical user interface with user-selectable list-box |
| US8042093B1 (en) | 2001-11-15 | 2011-10-18 | Cypress Semiconductor Corporation | System providing automatic source code generation for personalization and parameterization of user modules |
| US7774190B1 (en) | 2001-11-19 | 2010-08-10 | Cypress Semiconductor Corporation | Sleep and stall in an in-circuit emulation system |
| US6971004B1 (en) | 2001-11-19 | 2005-11-29 | Cypress Semiconductor Corp. | System and method of dynamically reconfiguring a programmable integrated circuit |
| US8069405B1 (en) | 2001-11-19 | 2011-11-29 | Cypress Semiconductor Corporation | User interface for efficiently browsing an electronic document using data-driven tabs |
| US7770113B1 (en) | 2001-11-19 | 2010-08-03 | Cypress Semiconductor Corporation | System and method for dynamically generating a configuration datasheet |
| US7844437B1 (en) | 2001-11-19 | 2010-11-30 | Cypress Semiconductor Corporation | System and method for performing next placements and pruning of disallowed placements for programming an integrated circuit |
| US6703599B1 (en) * | 2002-01-30 | 2004-03-09 | Microsoft Corporation | Proximity sensor with adaptive threshold |
| US8103497B1 (en) | 2002-03-28 | 2012-01-24 | Cypress Semiconductor Corporation | External interface for event architecture |
| US7308608B1 (en) | 2002-05-01 | 2007-12-11 | Cypress Semiconductor Corporation | Reconfigurable testing system and method |
| US6954867B2 (en) | 2002-07-26 | 2005-10-11 | Microsoft Corporation | Capacitive sensing employing a repeatable offset charge |
| US7761845B1 (en) | 2002-09-09 | 2010-07-20 | Cypress Semiconductor Corporation | Method for parameterizing a user module |
| US7253890B2 (en) * | 2003-12-19 | 2007-08-07 | Reza Miremadi | Door obstacle sensor |
| US7295049B1 (en) | 2004-03-25 | 2007-11-13 | Cypress Semiconductor Corporation | Method and circuit for rapid alignment of signals |
| US20050253694A1 (en) * | 2004-05-17 | 2005-11-17 | Kuznarowis Mark E | Vehicle mounted pedestrian sensor system |
| US7095312B2 (en) * | 2004-05-19 | 2006-08-22 | Accurate Technologies, Inc. | System and method for tracking identity movement and location of sports objects |
| US8286125B2 (en) | 2004-08-13 | 2012-10-09 | Cypress Semiconductor Corporation | Model for a hardware device-independent method of defining embedded firmware for programmable systems |
| US8069436B2 (en) | 2004-08-13 | 2011-11-29 | Cypress Semiconductor Corporation | Providing hardware independence to automate code generation of processing device firmware |
| JP2006146417A (en) * | 2004-11-17 | 2006-06-08 | Optex Co Ltd | Active device for detecting infrared ray |
| US7332976B1 (en) | 2005-02-04 | 2008-02-19 | Cypress Semiconductor Corporation | Poly-phase frequency synthesis oscillator |
| US7400183B1 (en) | 2005-05-05 | 2008-07-15 | Cypress Semiconductor Corporation | Voltage controlled oscillator delay cell and method |
| US8089461B2 (en) | 2005-06-23 | 2012-01-03 | Cypress Semiconductor Corporation | Touch wake for electronic devices |
| US20070021207A1 (en) * | 2005-07-25 | 2007-01-25 | Ned Ahdoot | Interactive combat game between a real player and a projected image of a computer generated player or a real player with a predictive method |
| US20070021199A1 (en) * | 2005-07-25 | 2007-01-25 | Ned Ahdoot | Interactive games with prediction method |
| US8552979B2 (en) * | 2005-08-30 | 2013-10-08 | Avago Technologies General Ip (Singapore) Pte. Ltd. | Proximity sensor for a graphical user interface navigation button |
| US7307485B1 (en) | 2005-11-14 | 2007-12-11 | Cypress Semiconductor Corporation | Capacitance sensor using relaxation oscillators |
| US20070114413A1 (en) * | 2005-11-18 | 2007-05-24 | James Parker | Integrated detecting processor |
| US20070114414A1 (en) * | 2005-11-18 | 2007-05-24 | James Parker | Energy signal detection device containing integrated detecting processor |
| US8085067B1 (en) | 2005-12-21 | 2011-12-27 | Cypress Semiconductor Corporation | Differential-to-single ended signal converter circuit and method |
| US7312616B2 (en) | 2006-01-20 | 2007-12-25 | Cypress Semiconductor Corporation | Successive approximate capacitance measurement circuit |
| US20070176903A1 (en) * | 2006-01-31 | 2007-08-02 | Dahlin Jeffrey J | Capacitive touch sensor button activation |
| US8067948B2 (en) * | 2006-03-27 | 2011-11-29 | Cypress Semiconductor Corporation | Input/output multiplexer bus |
| US8144125B2 (en) | 2006-03-30 | 2012-03-27 | Cypress Semiconductor Corporation | Apparatus and method for reducing average scan rate to detect a conductive object on a sensing device |
| US8040142B1 (en) | 2006-03-31 | 2011-10-18 | Cypress Semiconductor Corporation | Touch detection techniques for capacitive touch sense systems |
| US7721609B2 (en) | 2006-03-31 | 2010-05-25 | Cypress Semiconductor Corporation | Method and apparatus for sensing the force with which a button is pressed |
| US8537121B2 (en) * | 2006-05-26 | 2013-09-17 | Cypress Semiconductor Corporation | Multi-function slider in touchpad |
| US8089472B2 (en) | 2006-05-26 | 2012-01-03 | Cypress Semiconductor Corporation | Bidirectional slider with delete function |
| US20080218361A1 (en) * | 2006-06-07 | 2008-09-11 | Ee Systems Group Inc. | Process and system of energy signal detection |
| US8040321B2 (en) * | 2006-07-10 | 2011-10-18 | Cypress Semiconductor Corporation | Touch-sensor with shared capacitive sensors |
| US7253643B1 (en) | 2006-07-19 | 2007-08-07 | Cypress Semiconductor Corporation | Uninterrupted radial capacitive sense interface |
| US9507465B2 (en) | 2006-07-25 | 2016-11-29 | Cypress Semiconductor Corporation | Technique for increasing the sensitivity of capacitive sensor arrays |
| US9766738B1 (en) | 2006-08-23 | 2017-09-19 | Cypress Semiconductor Corporation | Position and usage based prioritization for capacitance sense interface |
| US8547114B2 (en) | 2006-11-14 | 2013-10-01 | Cypress Semiconductor Corporation | Capacitance to code converter with sigma-delta modulator |
| US8089288B1 (en) | 2006-11-16 | 2012-01-03 | Cypress Semiconductor Corporation | Charge accumulation capacitance sensor with linear transfer characteristic |
| AU2007328233B2 (en) | 2006-12-04 | 2012-09-13 | Deka Products Limited Partnership | Medical device including a slider assembly |
| US8058937B2 (en) * | 2007-01-30 | 2011-11-15 | Cypress Semiconductor Corporation | Setting a discharge rate and a charge rate of a relaxation oscillator circuit |
| US7737724B2 (en) | 2007-04-17 | 2010-06-15 | Cypress Semiconductor Corporation | Universal digital block interconnection and channel routing |
| US8516025B2 (en) * | 2007-04-17 | 2013-08-20 | Cypress Semiconductor Corporation | Clock driven dynamic datapath chaining |
| US8092083B2 (en) | 2007-04-17 | 2012-01-10 | Cypress Semiconductor Corporation | Temperature sensor with digital bandgap |
| US8130025B2 (en) | 2007-04-17 | 2012-03-06 | Cypress Semiconductor Corporation | Numerical band gap |
| US8026739B2 (en) | 2007-04-17 | 2011-09-27 | Cypress Semiconductor Corporation | System level interconnect with programmable switching |
| US8040266B2 (en) | 2007-04-17 | 2011-10-18 | Cypress Semiconductor Corporation | Programmable sigma-delta analog-to-digital converter |
| US9564902B2 (en) | 2007-04-17 | 2017-02-07 | Cypress Semiconductor Corporation | Dynamically configurable and re-configurable data path |
| US9720805B1 (en) | 2007-04-25 | 2017-08-01 | Cypress Semiconductor Corporation | System and method for controlling a target device |
| US8266575B1 (en) | 2007-04-25 | 2012-09-11 | Cypress Semiconductor Corporation | Systems and methods for dynamically reconfiguring a programmable system on a chip |
| US8065653B1 (en) | 2007-04-25 | 2011-11-22 | Cypress Semiconductor Corporation | Configuration of programmable IC design elements |
| US8144126B2 (en) | 2007-05-07 | 2012-03-27 | Cypress Semiconductor Corporation | Reducing sleep current in a capacitance sensing system |
| US9500686B1 (en) | 2007-06-29 | 2016-11-22 | Cypress Semiconductor Corporation | Capacitance measurement system and methods |
| WO2009006556A1 (en) | 2007-07-03 | 2009-01-08 | Cypress Semiconductor Corporation | Normalizing capacitive sensor array signals |
| US8089289B1 (en) | 2007-07-03 | 2012-01-03 | Cypress Semiconductor Corporation | Capacitive field sensor with sigma-delta modulator |
| US8169238B1 (en) | 2007-07-03 | 2012-05-01 | Cypress Semiconductor Corporation | Capacitance to frequency converter |
| US8570053B1 (en) | 2007-07-03 | 2013-10-29 | Cypress Semiconductor Corporation | Capacitive field sensor with sigma-delta modulator |
| US8049569B1 (en) | 2007-09-05 | 2011-11-01 | Cypress Semiconductor Corporation | Circuit and method for improving the accuracy of a crystal-less oscillator having dual-frequency modes |
| US8525798B2 (en) | 2008-01-28 | 2013-09-03 | Cypress Semiconductor Corporation | Touch sensing |
| US8487912B1 (en) | 2008-02-01 | 2013-07-16 | Cypress Semiconductor Corporation | Capacitive sense touch device with hysteresis threshold |
| US8358142B2 (en) | 2008-02-27 | 2013-01-22 | Cypress Semiconductor Corporation | Methods and circuits for measuring mutual and self capacitance |
| US8319505B1 (en) | 2008-10-24 | 2012-11-27 | Cypress Semiconductor Corporation | Methods and circuits for measuring mutual and self capacitance |
| US9104273B1 (en) | 2008-02-29 | 2015-08-11 | Cypress Semiconductor Corporation | Multi-touch sensing method |
| US8508366B2 (en) * | 2008-05-12 | 2013-08-13 | Robert Bosch Gmbh | Scanning security detector |
| US8102285B2 (en) * | 2008-06-05 | 2012-01-24 | Kalow Technologies, Inc. | Modular debouncing device |
| US7893829B2 (en) * | 2008-06-12 | 2011-02-22 | S.C. Johnson & Son, Inc. | Device that includes a motion sensing circuit |
| US8321174B1 (en) | 2008-09-26 | 2012-11-27 | Cypress Semiconductor Corporation | System and method to measure capacitance of capacitive sensor array |
| US8487639B1 (en) | 2008-11-21 | 2013-07-16 | Cypress Semiconductor Corporation | Receive demodulator for capacitive sensing |
| JP5304328B2 (en) * | 2009-03-03 | 2013-10-02 | オムロン株式会社 | Light detection circuit |
| US8866500B2 (en) | 2009-03-26 | 2014-10-21 | Cypress Semiconductor Corporation | Multi-functional capacitance sensing circuit with a current conveyor |
| US9448964B2 (en) | 2009-05-04 | 2016-09-20 | Cypress Semiconductor Corporation | Autonomous control in a programmable system |
| JP5006474B2 (en) * | 2009-08-28 | 2012-08-22 | オリンパスメディカルシステムズ株式会社 | Receiving system |
| WO2011032055A2 (en) * | 2009-09-12 | 2011-03-17 | Titan Pet Products, Inc. | Systems and methods for pet containment, training, and tracking |
| US9077365B2 (en) | 2010-10-15 | 2015-07-07 | S.C. Johnson & Son, Inc. | Application specific integrated circuit including a motion detection system |
| US9268441B2 (en) | 2011-04-05 | 2016-02-23 | Parade Technologies, Ltd. | Active integrator for a capacitive sense array |
| CN102445322A (en) * | 2011-09-21 | 2012-05-09 | 广东省特种设备检测院 | Device for detecting comprehensive performance of light curtain and safety grating |
| US9051127B2 (en) * | 2012-04-03 | 2015-06-09 | Scott Conroy | Grain auger protection system |
| JP6109943B2 (en) * | 2012-09-13 | 2017-04-05 | エムビーディーエー・ユーケー・リミテッド | Apparatus and method for sensing room occupancy |
| US9242150B2 (en) | 2013-03-08 | 2016-01-26 | Just Rule, Llc | System and method for determining ball movement |
| CN108459723B (en) * | 2018-06-12 | 2024-03-15 | 上海永亚智能科技有限公司 | Infrared gesture recognition device and recognition method |
| CA3132557C (en) * | 2019-03-08 | 2023-05-23 | The Chamberlain Group Llc | Object detection system and method |
Family Cites Families (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1806199A (en) * | 1928-05-03 | 1931-05-19 | Gen Electric | Method and apparatus for comparing radiant energy |
| US2227147A (en) * | 1938-03-24 | 1940-12-31 | American District Telegraph Co | Photoelectric burglar alarm system |
| US3278923A (en) * | 1964-06-30 | 1966-10-11 | Specialties Dev Corp | System for detecting intruders |
| US3278924A (en) * | 1964-07-01 | 1966-10-11 | Specialties Dev Corp | Detection of intruders |
| US3281817A (en) * | 1964-07-02 | 1966-10-25 | Specialties Dev Corp | Intruder detection |
| US3428815A (en) * | 1965-10-22 | 1969-02-18 | Electronic Ind Eng Inc | Distance measuring system using infrared ring-around oscillator with a reference loop having a light conducting rod |
| US3597755A (en) * | 1968-05-28 | 1971-08-03 | Sanders Associates Inc | Active electro-optical intrusion alarm system having automatic balancing means |
| US3644917A (en) * | 1969-09-18 | 1972-02-22 | Detection Systems Inc | Single terminal electro-optical intruder detection device |
| US3704374A (en) * | 1970-12-23 | 1972-11-28 | Control Tech | Ambient light variation detector |
| DE2247053C3 (en) * | 1972-09-26 | 1979-08-09 | Erwin Sick Gmbh Optik-Elektronik, 7808 Waldkirch | Light barrier |
| US3859648A (en) * | 1973-02-26 | 1975-01-07 | Patrick L Corbin | Intruder detection system utilizing artificial ambient light |
| US4032777A (en) * | 1976-03-29 | 1977-06-28 | Mccaleb Robert Earl | Photomeric monitoring device |
| FR2436996A1 (en) * | 1978-09-19 | 1980-04-18 | Tech Cales Automation Et | DEVICE FOR PROVIDING AN ELECTRICAL SIGNAL PROPORTIONAL TO A QUANTITY OF MOVEMENT, AND THE SAME, CAPABLE OF DETECTING ANY MOTION OR ACCELERATION |
| DE2851444C2 (en) * | 1978-11-28 | 1983-05-26 | Erwin Sick Gmbh Optik-Elektronik, 7808 Waldkirch | Light curtain |
| US4247765A (en) * | 1979-01-03 | 1981-01-27 | Bergstroem Arne | Pulsed feedback circuit for an optoelectronic detector |
| SE428250B (en) * | 1979-05-31 | 1983-06-13 | Bert Jonsson | PHOTOELECTRIC DEVICE FOR SENSING FORM |
| SE431594B (en) * | 1982-06-15 | 1984-02-13 | Besam Ab | DEVICE FOR PHOTOELECTRIC DETECTION OF FORMAL |
-
1987
- 1987-02-02 US US07/009,777 patent/US4736097A/en not_active Expired - Fee Related
-
1988
- 1988-01-29 CA CA000557750A patent/CA1326276C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| US4736097A (en) | 1988-04-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1326276C (en) | Optical motion sensor | |
| US4879461A (en) | Energy field sensor using summing means | |
| US5491330A (en) | Ambient light detector, laser lighting control device using the same suitable for bar code reader, and bar code reader | |
| US6455839B1 (en) | Obstacle detection sensor using synchronous detection | |
| US5103085A (en) | Photoelectric proximity detector and switch | |
| CA1137589A (en) | Smoke detector | |
| AU695919B2 (en) | Variable beam detection | |
| US5923427A (en) | Optical triangulation distance sensing system and method using a position sensitive detector and an automatic power controlled light source | |
| DE69710019T2 (en) | Presence sensor with multiple functions | |
| CN1088225C (en) | Active IR intrusion detector | |
| CA2135929C (en) | Motion detector with improved signal discrimination | |
| EP0353259B1 (en) | Motion sensor | |
| US4864278A (en) | Optical intrusion detection system and method | |
| AU696276B2 (en) | Weak beam detection | |
| US5404008A (en) | Control system for detecting intrusion of a light curtain | |
| US5245196A (en) | Infrared flame sensor responsive to infrared radiation | |
| US5144286A (en) | Photosensitive switch with circuit for indicating malfunction | |
| US4319133A (en) | Photoelectric detection system | |
| KR100493982B1 (en) | Detection system with improved noise tolerance | |
| US4288791A (en) | Smoke detector and method | |
| JP3265663B2 (en) | Photoelectric switch | |
| US6396060B1 (en) | System for detecting radiation in the presence of more intense background radiation | |
| EP0068019B1 (en) | Control device responsive to infrared radiation | |
| CA2220804C (en) | Passive infrared motion detection circuit having four comparators | |
| JPH098744A (en) | Bias system for avalanche photodiode |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |