WO2003038594A1

WO2003038594A1 - Printing method and device

Info

Publication number: WO2003038594A1
Application number: PCT/FI2002/000849
Authority: WO
Inventors: Eero KYTÖ; Ville Laine; Timo Nyberg
Original assignee: Kytoe Eero; Ville Laine; Timo Nyberg
Priority date: 2001-11-02
Filing date: 2002-11-01
Publication date: 2003-05-08
Also published as: FI20012123A0; FI20012123A

Abstract

The present invention is directed to a method for printing digital data on a printing material and a printing device for doing this. The method comprises the steps of receiving the data to be printed, defining the location of a printing head of the printing device on a printing material, and printing said digital data thereon.

Description

PRINTING METHOD AND DEVICE

FIELD OF THE INVENTION

The present invention relates to a method of printing digital data on a printing material where the position or location of a printing head on the printing material is determined and the information corresponding thereto is transmitted to a printing controller, which processes the said information. The data to be printed is received through a transceiver, then transmitted to the printing controller, which controls a current feed to printing electrodes in the printing head, to provide the correct printing result.

BACKGROUND OF THE INVENTION

The portable printers on the market today are usually thermal printers. In heat- printing, the printing material, paper or plastic film, is coated with a thermochromic substance, ie. a material that changes its colour under the influence of heat. The printing head is formed by small thermoresistances that heat a heat-sensitive surface of the printing material. The printing heads are small and light which is an advantage in a portable printer. The fact that the colouring agent is in the printing material and not in the printing device also decreases the size of the printing device. The disavantages are that much power is needed to warm the printing material to achieve the change of colour. This requires a high current through the thermoresistances. Due to the high power consumption and the need of strong currents, large batteries are needed for portable models to ensure a sufficient time of use.

Instead of coating with a thermochromic substance, the printing material can be coated with a electrochromic coating, ie. a substance that changes its colour as a result of a change of electrical potential. The most common type of substances for changing colour due to a difference in potential, are metal compounds, for example tungsten compounds. Tungsten tri oxide, WO₃, is initially colourless but becomes deep blue when 0.5 to 1.5 volts DC is applied to it reducing the tungsten trioxide. Other types of electrochromatic coatings can be found for example in the following publications, US.Pat 3,952,314, which discloses pH- indicator colours and US.Pat. 4,561,001 and US.Pat. 5,141,622, which disclose leuco colours.

On the market there is also an electronic pen manufactured by Anoto AB, Sweden. This concept is based on using a substrate with a special pattern which uniquely defines a position on itself. The pattern covers an area of 4.6million km . The pattern consists of tiny dots that are slightly displaced from a grid structure to encode position coordinates, which uniquely defines any position as described in WO 0126032. These coordinates are interpreted by a digital camera that records the position on the substrate when the pen is used for writing. The data so accumulated is stored and can be transmitted by Bluetooth technology to a PC or mobile phone.

SUMMARY OF THE INVENTION

The present invention presents a method for printing digital data on a printing material and a printing device for doing this. Printing is carried out by moving a printing head of a printing device over the printing material. The method comprises the steps of receiving, in a printing controller of the printing device, the data to be printed, defining the location of the printing head on the printing material and generating and transfering information corresponding thereto to the printing controller, and using the information so received by the printing controller to control the current feed to at least one electrode pair in the printing head to create an image on the printing material corresponding to the data to be printed. The printing head according to the invention comprises a printing head carrying at least one electrode pair, a printing controller for controlling the electrode pairs, means to receive the printable data and to transfer it to the printing controller. DETAILED DESCRIPTION OF THE INVENTION According to the invention, the digital data can take any form, and be for example in the form of electronic mail or a telefax transmission. The tracking of the position or location of the printing head on the printing material can be done in many different ways, for example optically or magnetically. The position obtained can be either the absolute position of the printing head on the printing material or the position of the printing head relative to its previous location. To track the absolute position of a moving object requires an external system and a predefined working area. The external system and the predefined working area can be for example position coordinates encoded on the printing material or a separate support beneath the printing material. In the Anoto concept, position information is encoded on the printing material or substrate by using a pattern, as described above. A very small portion of the pattern uniquely defines the position on the full pattern.

According to one embodiment the pattern can be printed with black carbon- based ink on any paper or other substrate allowing at least 1000 dpi resolution. For the eye the pattern appears as a nearly invisible light-gray dusting of dots. The carbon-based ink absorbs infrared light and can therefore be seen by an image sensor, which is made most sensitive to infrared wavelengths of light.

Noncarbon-based colours can be used to print or write whatever is required on top of the pattern without disturbing the sensor.

The pattern can be interpreted by a camera using a CMOS or CCD as picture means and an image processor to interpret and process the information so generated.

The dots of the pattern are illuminated by infrared light, making them visible to the camera. The camera containing, for example, a CMOS image-sensing chip acquires digital images of the pattern for example at a rate of 100 images per second. The image processor then calculates the exact position in the entire pattern by comparing the images and by gathering and storing information relating to the position or angle of the printer. The data stemming from the image processor is loaded into the printer memory and further to the printer controller, or a transceiver transmits the information in the memory either directly to a computer or to a relay device, such as a mobile phone. Instead of a carbon-based ink, an ink containing small amounts of marking substances which fluoresce in infrared or UV-ranges can be used, which inks are almost invisible to the human eye. Some such substances are disclosed in the publications US.Pat. 5,614,008 and US.Pat. 5,093,147. The fluorescense is excited with a LED or laser diode of suitable wavelength, which makes the marking substance fluoresce at a longer wavelength than the excitation wavelength. A filter placed in front of the camera will let through wavelengths longer than the excitation wavelength, the remaining wavelengths being filtered. Such a method is known from US.Pat. 5,773,808.

Instead of a dot pattern, some other position-coding pattern can be used. Some such position-coding patterns are given in US.Pat. 5,852,434 and WO 9950736.

Instead of optical position encoding, magnetical encoding can be used. Position information can also be added magnetically onto a substrate containing a magnetic material. Optionally the the magnetic particles can be situated in the coating of the printing material. Both options are described in US.Pat. 5,426,011 and US.Pat. 5,143,583. The position of the printing head moving over the printing material is then determined by sensing the magnetic field intensity at any specific point. The magnetic field intensity can be measured for example with magnetoresistive (MR) sensors. The magnetical encoding of the printing material is made by magnetising the printing material in specific places.

A third option of determining the location of the printing head is by radiofrequency-based (RF) tracking. There are two major approaches in determining the trajectory of a moving object with radio frequency (or microwave frequency) electromagnetic radiation. One approach is the field method, where the moving object emits electromagnetic pulses and its position is determined by recording the amplitudes of the received signals in two or more receivers at known positions. The other one is the time of flight approach, where the times of flight of electromagnetic pulses transmitted by the moving object to two or more stationary receivers in known locations are measured.

The field method approach is based on the measurement of the pulse amplitude reduction along the distance between the transmitter and the receivers. A burst of self-damped oscillations, excited by a sharp pulse, is used to modulate a radio frequency (RF) carrier. In order to provide constant resolution of the pulse amplitude measurement, the overall operating area is divided into several thin radial zones. Within each zone, the amplitude of the predefined pulse in the burst is measured. When the transmitter crosses zones, the system moves to measure the adjacent pulse amplitude.

In the time of flight approach, the system measures the propagation time of a very short RF burst traveling between a moving transmitter and three stationary receivers. A micro-controller triangulates the position of the receiver from known time of flight between the transmitter and the receivers and the base distance between the receivers. The burst emission and detection times are randomized in order to avoid interference with other sources of RF radiation, such as radio and TV transmitters or microwave ovens, and to allow multiple users at the same location.

Using this method the printing material can be placed at a support or pad that has stationary receivers, two or more. A transmitter at the printing head sends out radio or microwave frequency signals to the receivers in known positions on the support and the exact position of the printer head on the support is recognized. The distance between the transmitter and the receivers can be determined either by a field or a transmission time method. In the field method, a carrier wave signal is modulated with pulses and the damping of the pulses between the transmitter and the receiver is measured. The damping of the signal is proportional to the distance between the same. In the transmission time method the transmitter transmits very short radio or microwave frequency bursts and the transmission time for them between the transmitter and receivers is meassured. The transmission time is proportional to the distance between the same. When the distance between the transmitter and the receivers is known the position of the transmitter on the printing head can be calculated geometrically. A support can also be magnetized, and the location of the printing head on the printing material placed on the support can then be determined with the help of magnetic encoding described above.

The digital data to be printed by the method according to the invention can be received from, for example, a computer or a mobile phone by any suitable transmission method. One option is the use of Bluetooth technology. Information can then be received from another device also using Bluetooth technology. Other methods that can be used are data transmission techniques operating at microwaveor radio frequences or optical transmission methods working at infrared wavelengths. These techniques are for example used in cordless head phones.

The printing head of the printer comprises at least one electrode pair which are controlled by a printing controller which receives both the data to be printed and the information about the position of the printing head on the printing material. With the help of this information the printing controller controls the electrodes on the printing head and the current feed to them in order to effect a colour change for forming an image on the printing material according to the data to be printed. Thus for this purpose, any system that changes colour under the influence of an electrical potential applied to the system, can be used, and such systems are known in the art. The printing material can be coated for example with a electrochromic coating. The printing material or especially a coating thereof can suitably comprise microcapsules containing e.g. an electrochromic compound. Such compounds which are mentioned earlier and are well known in the art, can be for example certain metal compounds, such as tungsten compounds, or pH-indicator colours or leuco colours, that change colour according to a change of the electrical potential. Also encapsulation techniques are well known in the art, there being numerous processes and materials, such as polymers which are useful for the purpose. Numerous suitable procedures for microencapsulation are detailed in text books, such as in Microencapsulation, Processes and Applications (ed. by I.E. Vandegaer) Plenum Press, New York, NY (1994). Such microencapsulation techniques include for example interfacial polymerization, in situ polymerization, physical processes, such as coextrusion and other phase separation processes and in-liquid curing.

Printing on microcapsules can be done in two different ways. If the printing head is pressed to the printing material while printing, the pressure applied to the material will break the microcapsules and the trace will be permanent. If instead the printing head is moved lightly over the printing material, the microcapsules remain intact and the trace will be erasable by switching the electrical potential. Use of microcapsules in thin displays is described in US.Pat. 6,120,588.

According to one embodiment, the angle between the printing head and an edge of the printing material is also determined. The said edge can be the top edge of the printing material, and the angle can be determined in different ways, according to the method used for tracking the position. If the position is tracked using a single image sensor, the angle is obtained from the images using applicable image processing algorithms. In the case of tracking the position using multiple position detectors, the angle is geometrically obtained using the position coordinates given by the detectors. When using magnetical encoding, properties of the magnetic field, such as the direction and intensity of the field, can also be used when determining the angle between the printing head and the top edge of the printing material. In printing knowledge of the angle helps compensating for variations in the angle between the edge of the printing material and the printing head of the printing device.

If a separate support is used in conjunction with the printing device, the device can be mechanically coupled to the support so that the angle between the edge of the printing material and the printing head remains constant while printing. In this case, the angle does not need to be determined.

Knowledge of the absolute position of the electrode pairs of the printing head on the printing material enables the printing of data in specified places on the printing material. This can be used for example in printing on pre-printed materials or substrates. For example when printing on an envelope the name and address may be chosen from a electronic address list, and the correct position for printing on the envelope is recognized by the printing device. The same applies for filling in forms etc.

If knowledge of the absolute position is not desired, it is sufficient to just determine the position of the printing head relative to its previous location, for example the initial location of the printing head. In this case, an external system or a predefined working area are not necessary. The relative position can be tracked if the speed and direction of motion of the printing head are known. The speed and direction of motion of the printing head can be measured using for example optical or optomechanical motion sensors.

One applicable optical motion sensor using non-coherent illumination is based on the same Optical Navigation Technology as used for example in optical computer mice. In this technology, a CMOS image sensor acquires microscopic images of surface via a lens and illumination system. These images are further processed by a digital signal processor to mathematically determine direction and distance of motion. One applicable optical motion sensor using coherent illumination is based on the Optical Translation Measurement (OTM) technology described in WO9946603. OTM is a technology for coherent encoders measuring one-, two- or three-dimensional motion. The OTM encoder measures the relative motion of a surface placed adjacent to its aperture, using diffusive light reflected by the surface.

A basic OTM device contains a laser light source, collimation lens, grating, focusing lens, one or more detectors, and signal processing electronics. The laser light is collimated by a lens and directed toward the surface being measured. The optical grating is placed between the laser and the surface, reflecting part of the light as back-diffracted orders that serve as local oscillator

(LO) beams. The diffuse light reflected from the surface and the LO light are both focused onto the detectors by the focusing lens, so that each detector detects a single LO beam. The detector measures the interference signal between the LO beam and the light reflected from the surface. The resulting detector signal varies with changes to the relative phase between the LO beam and the surface reflection, corresponding to the relative translation of the device and the surface. A single encoder using a 2-D grating can measure full 3-D motion. The encoder resolution is set by the grating period, and the accuracy depends on the illuminated grating size.

Optomechanical encoders translate motion into electronic signals to track the speed and direction. In these encoders, motion of a mechanical unit, such as a slotted wheel, interrupts the optical path between a light-emitting diode (LED) and a detector. The speed the wheels turn tells the unit how fast it is moving . If the wheels move in opposite direction or at different speeds, it can be calculated in which direction the printer is moving.

Knowledge of the absolute position of the electrode pairs of the printing head on the printing material enables the printing of data in specified places on the printing material. This can be used for example in printing on pre-printed materials or substrates. For example when printing on an envelope the name and address may be chosen from a electronic address list, and the correct position for printing on the envelope is recognized by the printing device, the same applies for filling in forms etc.

According to a further embodiment the printing device can also comprise means 5 to make it useable as a pencil. In this case the picture angle of the camera can be turned to take images of the position coordinates in the pattern on the printing material. The turning of the picture angle of the camera can for example be made electrically using two CMOS-chips, one for writing and one for printing, or mechanically using one CMOS-chip which can be turned to a different angle, 0 or by turning the mirror optics. In this way images can be obtained of the position coordinates, the images can be processed in the printing controller, the information relating thereto stored and can be subsequently transmitted e.g. to a datareceiving device, such as a computer, mobile phone or the like, a text written by the pen does not disturb the decoding of the coordinates on the 5 printing material. The tracking of the position on the printing material can also be carried out according to other tracking methods described earlier, for example magnetically. The device can include a container or similar for ink, in order to produce a discernible trace or mark on the printing material. However the inclusion of an ink container is not necessary when a visible trace is not o needed.

An embodiment of the invention is shown in the appended drawing.

In the Fig.lA, the data to be printed is received to the printing device 1 through 5 a transceiver 2. The printing controller 3 processes the data received as well as the information relating to the position of the printing head 4. The position coordinates 5 on the printing material 6 are illuminated by infrared light by the LED 7 to be made visible to the digital camera 8. The camera 8 contains a CMOS image-sensing chip 9 and acquires digital images of the coordinates 5 o through lense 10a. The coordinates 5 are decoded in a processor 11 and also the angle between the printing head 4 and top of the printing material 6 is determined from the coordinates 5 in the processor 11. This information is transmitted to the printing controller 3 which combines this information with the data to be printed and uses the combined data to thereafter control the current feed to the electrode pairs 12 on the printing head 4. To make a permanent trace, the printing head 4 is pressed against the printing material 6 to break the microcapsules 13. In order to provide an erasable trace, less pressure is applied in order to keep the microcapsules intact. The movement of the printer can come from the hand of the user to minimize the size of the printer.

In Fig. IB the use of the device as a pencil is shown. In this embodiment the device is turned as to use the writing end or pen 14 thereof. Such a pencil can be used for writing and transmitting the written data to an external device. In this case ink can be provided from a container, such as a cartidge included in the pen (not shown). A lense 10b is used to take digital images with the camera 8. The images of the position coordinates are processed by the processor 11 and stored in a memory (not shown). The written text so digitated can then be transmitted e.g. to an outside receiving and processing device, for example a computer or a mobile phone or the like using the transceiver 2.

Claims

1. A method for printing digital data on a printing material, by moving a printing head of a printing device over the printing material, the method comprising the steps of receiving, in a printing controller of the printing device, the data to be printed, defining the location of the printing head on the printing material and generating and transfering information corresponding thereto to the printing controller, and using the information so received by the printing controller to control the current feed to at least one electrode pair in the printing head to create an image on the printing material corresponding to the data to be printed.

2. The method according to claim 1 , wherein the data to be printed is transmitted to the printing device by means of Bluetooth technology.

3. The method according to claim 1, wherein the data to be printed is transmitted to the printing device using data transmission techniques operating at microwave or radio frequences or optical transmission methods working at infrared wavelengths.

4. The method according to claim 1, wherein the location of the printing head on the printing material is determined optically from point coordinates on the printing material.

5. The method according to claim 4, wherein a camera using a CMOS or CCD as picture means is used for determining the location from the point coordinates.

6. The method according to claim 1 , wherein the position of the printing head on the printing material is determined magnetically from the printing material.

7. The method according to claim 6, wherein the printing material comprises magnetical particles within the printing material, or in a coating thereon.

5 8. The method according to claim 6, wherein the printing material is magnetized by a magnetic support located under the printing material.

9. The method according to claim 4, wherein the angle between the printing head and an edge of the printing material is determined by image processing 0 from the point coordinates.

10. The method according to claim 6, wherein the angle between the printing head and an edge of the printing material is determined from the magnetic field with a position detector. 5

11. The method according to claim 1, wherein the angle between the printing head and an edge of the printing material is calculated geometrically by generating and using information corresponding to the positions on the printing material of at least two position detectors placed at a mutual o distance on the printing head.

12. The method according to claim 1, wherein the location of the printing head is defined in relation to a previous poisition thereof obtained by measuring the motion speed and direction of the printing device optically or 5 optomecanically.

13. The method according to claim 1, wherein the printing material is coated with an electrochromic coating.

0 14. The method according to claim 1 , wherein the printing material or a coating thereof is formed by or comprises microcapsules.

15. The method according to claim 14, wherein the microcapsules contain an electrochromic compound.

16. The method according to claim 14, wherein the microcapsules are broken during printing to provide a permanent image on the printing material.

17. The method according to claim 14, wherein the microcapsules are unruptured during printing and the trace of the printing head is erased by changing the polarity of the voltage.

18. A printing device for performing the method according to claim 1, the printing device comprising a printing head carrying at least one electrode pair, a printing controller controlling the electrode pairs, means to determine the position of the printing head on the printing material, and means to receive the printable data and transfer it to the printing controller.

19. The printing device according to claim 18, comprising means for receiving the printable data transmitted by Bluetooth technology.

20. The printing device according to claim 18, comprising means for receiving the printable data transmitted at microwave or radio frequences or at infrared wavelengths optically.

21. The printing device according to claim 18, comprising a camera using a

CMOS or CCD as picture means for determining the location from the point coordinates.

22. The printing device according to claim 21, comprising means to determine the angle between the printing head and an edge of the printing material from the point cooordinates.

23. The printing device according to claim 18, comprising means to determine the position of the printing head on the printing material magnetically.

24. The printing device according to claim 23, comprising a position detector to determine the angle between the printing head and an edge of the printing material magnetically.

25. The printing device according to claim 18, comprising at least two detectors placed at a mutual distance on the printing head for determining their positions on the printing material and using the information determining the angle between the printing head and an edge of the printing material.

26. The printing device according to claim 18, comprising means to define the location of the printing head in relation to a previous position thereof optically or optomecanically.

27. The printing device according to claim 18, comprising means to locate the position and movement of the device when moving the device over the printing material, such as when writing, means to process and store the information correspdnding thereto and to transmit the same to a data receiving means e.g. a computer to enable the use of the printing device also as an electronic pencil.

28. The printing device according to claim 27, comprising an ink container for leaving a mark on the printing material.