FR2593303A1 - Touch screen emulating a light pen - Google Patents

Abstract

The touch screen comprises a set of infra-red light-emitting diodes PL, PC and a set of photo receivers RL, RC. The control unit MC makes it possible to excite the light-emitting diodes sequentially at the rate of the scanning of the spot of the video screen. At 1, the video signal which comprises signals such as start-of-frame or start-of-line is brought in. Unit 2 detects the start-of-frame. The assemblies 31 and 41 (respectively 32 and 42) sequentially excite the diodes PL (respectively PC) by means of decoders 61 (respectively 62). On the reception side, the processing electronics EP comprise a memory latch 81 whose output is connected to a (AND) gate 100 which delivers a signal at 110. The time shift between the start-of-frame and the signal delivered at 110 is characteristic of the position of the designated point on the screen. The output 110 may be connected directly to a processing circuit for a light pen.

Description

Touch screen emulating a photostyle.

The invention relates to devices for communicating with computer hardware, usually called touch screens "
These screens allow data to be entered into a computer by approaching or touching a display screen with a finger, a pencil, or another passive body. They are capable of very numerous applications in fields as different as education, terminals usable by the public, or air navigation control. They are particularly suitable whenever the messages which are communicated to the computer are determined in advance according to a certain logical diagram or when the persons who communicate with the computer system have no particular preparation.

 There are many methods for making touch screens. It is still necessary to distinguish between the physical phenomenon which is used, and the electronic processing means which make it possible to determine the position of the place where one touches the screen.

The physical phenomena used in the production of touch screens are varied. Perhaps the best known is the use of infrared light waves. We have also thought of using acoustic waves or phenomena of variation in electrical conductivity or variation in capacity. Some of the known embodiments will be described below.

Usually, systems using infrared radiation are constructed as follows: photo-emissive diodes are arranged horizontally and vertically opposite opto-electronic receiving elements. In general, there is a double vertical row of light emitting diodes and receiving elements, and similarly a double horizontal row. The infrared radiation from the photo-emitting diodes propagates parallel to the screen. If an opaque body is placed near the screen, there is an interruption in the signal received by the opto-electronic elements, which makes it easy to locate the abscissa and the ordinate of the point of contact on the In a variant of this system, a screen scan is used parallel to that, thanks to a mechanically actuated mirror device which returns the ray produced by a photoluminescent diode placed in a corner of the screen. In this variant, instead of having an abscissa and an ordinate for locating the designated point of the screen, there are two angles.

Systems using ultrasonic acoustic waves are built on analogous principles. There are two rows of ultrasonic emitters vertically and horizontally so that the propagation of the waves takes place parallel to the screen and in vertical and horizontal directions. Facing the transmitter lines are arranged vertically and horizontally two rows of acoustic receivers. The interposition of a body placed in the vicinity of the touch screen makes it possible, as in the case of infrared light waves, to determine, by virtue of the weakening of the acoustic signal received, the abscissa and the ordinate of the designated point on the screen.

We also know other systems. For example, it is known to make a transparent film, consisting of two sheets separated by a layer of semi-permeable insulation. On each of the sheets are arranged face to face horizontally and vertically narrow metallized strips, very thin and therefore also transparent, which come into contact if pressure is applied to the film.

The entire device is placed in front of the display screen. We can thus identify the point of contact by the existence of a current on line t on the column corresponding to the point which was touched. This technique makes it possible to obtain a resolution higher than that of photoluminescent diodes, with the disadvantage however that the transparency, and therefore the brightness of the screen, are less good.

In all touch screens as described, electronic processing means exist. These means essentially consist of decoding circuits making it possible to know the abscissa and the ordinate of the contact point. One can also find, either to reduce consumption, or to improve the accuracy of tracking, a multiplexing of the broadcast. In all cases, the touch screen provides two spatial indications as an output, generally the abscissa X and the ordinate Y of the contact point.

This requires downstream, on the side of the processing computer, specific logic adapted to the processing of this type of information.

However, it is known that many computers, and in particular microcomputers, are provided with circuits for using photostyle apparatuses, also called optical pencils.

These devices, like touch screens, allow you to designate a point on a display screen. But they are active (photoreceptor) and require a connection cord between the instrument which is used to designate the point of the screen (the photostyle itself) and the screen.

This makes them fragile, and therefore difficult to use for terminals accessible to the public.

The main object of the present invention is to allow the direct connection of a touch screen, whatever its physical embodiment, to a circuit for using a photostyle.

The invention relates to an electronic device of the touch screen type, which comprises a display screen, operating in raster scanning mode, electronic means capable of locating a body located in the immediate vicinity or in contact with the screen, comprising transmitting organs and cooperating receiving organs, located near the screen, so that the localization of the body is obtained through the variation of a physical phenomenon such as electromagnetic waves, acoustic waves, conductivity, between the emitting and receiving organs , and means for electronic processing of the signals thus obtained.

According to a first aspect of the invention, the device comprises control means for exciting the transmitting organs according to a predetermined time sequence as a function of the spatial exploration of the screen, so that the variation or interruption of the signals of reception determines a temporal information defining an indication of position of the body on the screen.

Usually, there are two groups of electronic localization means, for example one corresponding to the lines of the screen and the other to the columns so that the signals received on each of the groups of the receiving organs together define a temporal information linked to the position of the body on the screen.

Very advantageously, the control means for producing the predetermined time sequence used to excite transmitting members are initialized at each frame scan by the start of frame signal from the display screen.

According to another aspect of the invention, the control means comprise at least one counter associated with decoding circuits, which selectively excite the transmitting members.

The counter may use pulses from circuits for logic shaping of the synchronization signals of the display screen.

 It is also possible that the counter uses the pulses coming from a quartz clock.

According to another aspect of the invention, the means comprise two counters, each associated with decoding circuits, each of the counters and these decoding circuits cooperating with a group of transmitting members.

In another embodiment of the invention, the control means comprise a single counter, associated with decoding circuits, so that the lower part of the counter contains the column address and the upper part the address of line of excited transmitters.

Very advantageously, the detection of the signals on a group of receivers corresponding to the lines uses a memory circuit of the flip-flop type and the detection of the signals on the other group of receivers, corresponding to the columns, is connected, as well as the output of the circuit memory, to a logical AND circuit.

 It is also possible that the processing means of the device comprise two comparators making it possible to compare the signals transmitted and received for a given row and column and a logic AND circuit connected to these two comparators.

According to the invention, the processing means of the electronic device are directly connectable to circuits for using a photostyle device.

Other characteristics and advantages of the invention will appear on examining the detailed description below, as well as the appended drawings, in which - FIG. 1 represents a first embodiment of the invention, with two counters, and circuits for the logical shaping of the synchronization signals of the display screen; - Figure 2 shows another embodiment of the invention, with a single counter, and a quartz clock; FIG. 3 is a diagram describing the time operation of a device as described in FIG. 1.

- Figure 4 is a block diagram showing the application of the device according to the invention.

The drawings must be considered as an integral part of the description and may, if necessary, be used to complete it as well as to define the invention.

 I1 is now referred to in Figure 1.

In 1 is brought the composite video signal applied to the display screen. This composite signal includes synchronization signals such as start of frame, start of line.

Block 2 is a useful frame start detection block.

By start of useful frame, we mean the start of the image visible on the screen. The start of the useful frame can be deduced from the start of the scan frame by a suitable delay.

Block 31 performs logical formatting of line synchronization signals. Block 32 performs logical shaping of the column signals. I1 can be for example an oscillator triggered at the start of each line and having a frequency depending on the definition (number of columns) desired. This oscillator does not need great stability. This can also be done by using the time interval between two start of line signals by dividing it by a suitable time base. The row and column counters 41 and 42 change at the rate of the pulses delivered by the outputs of blocks 31 and 32 respectively. The contents of these counters 41 and 42 are applied to decoders for controlling lines or columns 61 and 62, respectively.

When block 2 detects a useful start of frame signal, the counters 41 and 42 are reset to zero by their inputs 51 and 52.

At each line scanned, the circuit 31 advances the counting of the counter 41 by one notch. When this counting reaches a chosen value, corresponding for example to the first useful line of the scanning, the decoder 61 excites the photoemitter PL1 which transmits in the direction of this useful first line.

Meanwhile, circuit 32 advances counter 42 at the rate of the columns. As a function of this count, the photoemitters PC1, PC2 and PC3, which emit in the direction of the successive columns defined on the screen are excited sequentially, by means of the decoder 62.

This process is repeated for the following lines, with the photoemitters PL2 to PL4.

The blocks 2, 31, 32 as well as the counters 41 and 42 define the set of control means MC.

 It is important that this excitation of the PL line and column PC photoemitters follows the effective displacement of the scanning spot on the screen VI, with an accuracy which depends on the desired resolution so that the location of the object which is approach the screen. This is obtained here by adjusting accordingly any delays of circuits 2, 31, 32, and / or the interconnection provided by the decoders between the counters 31 and 32 on the one hand, the line and column photoemitters PL d 'somewhere else. Thus, the touch screen is broken down into analysis zones: in a given row (or a given group of rows) the columns are queried one after the other; and the lines (or groups of lines) are interrogated successively one after the other. This analysis is synchronous with the scanning of the screen for viewing.

On the reception side, the line receivers RL1 to
RL4 have their outputs combined in a junction 71 which defines an OR function: the junction 71 is excited if any of the RL receivers perceive the light emitted. I1 is the same for the column receivers RC1 to RC3, with the OR junction 72. The junction 71 is connected to a memory flip-flop 81, reset to zero at each end of line thanks to the input 91 connected to an output line counter suitable for transmission 41, output which can be that applied to decoder 61. Junction 71 and output of flip-flop 81 are applied to a door
AND 100, whose output 110 delivers a signal whose temporal position is linked to the spatial position of an object on the screen. This set defines the means of treatment
EP.

Figure 3 illustrates the operation of the device according to Figure 1. In this figure, are carried, as a function of time, the signals obtained at different points of the device. Curve 200 corresponds to the composite signal applied to the display screen. In 201, a frame start signal is shown. Similarly, in 202, the signal corresponding to the start of the next frame appears, that is to say at the start of the next frame. At 211, 212, 213, there are three column pulses defined in the first scan line; similarly in 221, 222, 223, three column pulses corresponding to the second scanning line; And so on. In 210 is the line return signal of the first line, in 220 the line return signal of the second line, in 230 the line return signal of the third line. Line 200 therefore corresponds to an analysis of the touch screen in three columns and four lines. In practice, the number of rows and columns of the touch screen will be much higher, depending on the desired resolution.

In 300, the signal as received on junction 72 is shown; it is normally of high level (excited photoreceptor), and does not go to low level only when a body is interposed on the light beam of the corresponding column, as illustrated in 312, 322, 332, 342. Here, the contact body is located on the second column.

In 400 is shown the signal received on junction 71 corresponding to the line receivers of the screen. We see that we obtain a signal at 420 corresponding to a body located on the second line of the screen. The curve 400 'corresponds to the signal 420' as available at the output of the memory 81, namely the signal 420 memorized until the start of the next line. The curve 500 corresponds to the signal 522 available at the output of the logic AND 100, at 110. This signal 522 clearly defines time information which is in correspondence with the point which is designated by the body on the screen. This information is defined by the time difference between point O and the signal designated by 522 on line 500.

 I1 is now referred to in Figure 2, which shows another embodiment of the invention.

The scan signal from the display screen VI arrives at the device according to the invention at 1-1. The block 21, the counter 40-1 and the clock 41-1 constitute the control means MC. Block 2-1 is a useful frame start detection block, as above. The output of this block is applied to the reset input 50-1 of the counter 40-1. The counter 40-1 is pulsed by pulses coming from a quartz clock 41-1. The lower part (low weight) of the counter 40-1 addresses the decoding device 62-1, which makes it possible to excite that of the transmitting organs PC whose column number is contained in the lower part of the counter. the upper part (high weight) of the counter 40-1 addresses the decoding device 61-1, which allows the excitation of that of the transmitting members PL corresponding to the line whose number is contained in the upper part of the counter.

The outputs of the line receivers RL and column RC are connected to address coding circuits 71-1 and 72-1 respectively, which supply the addresses of the reception elements on which a signal is received. In an infrared radiation system, this will be an absence of excitation. In this case, for example, if the n-th line receiver is not energized, the circuit 71-1 transmits the address n. Like address decoding, address coding can be done using AND / OR logic gates, as one skilled in the art knows.

In the processing means EP, the line addresses applied to the photoemitters PL are compared with those received from the photoreceptors RL, in a digital comparator 101-1. A second digital comparator 102-1 does the same for the addresses of columns.

The outputs of the two comparators are applied to an AND gate 100-1, which, as before, provides in 110-1 an output signal whose temporal position, relative to the start of the frame, is directly linked to the location of the screen where you approach a body.

A variant would consist in applying to the comparators 101-1 and 102-1 on one side the outputs of the decoders 61-1 and 62-1, on the other the direct outputs of the photodetectors
RL and RC. This process requires having comparators with more entries, respectively equal to the number of rows and columns of the screen.

We can also consider another variant for an embodiment of the invention according to FIG. 2.

This variant consists in that the infrared light-emitting diodes PL and PC emit permanently.

In this case, it obviously does not have to select the diodes on transmission, and the decoding circuits 61-1 and 62-1 no longer have their raison d'être. Those skilled in the art know that one can realize, by a very simple combinational logic, the circuits which statically give the position which is pointed on the screen. These circuits 71-1 and 72-1 therefore provide a binary value corresponding to the pointed position, which value is compared with that of the counter 40-1. When there is equality, an impulse is delivered in 110-1 as in the previous variant.

This solution has the advantage of lightening the logic by removing the decoders 61-1 and 62-1. The detection logic is purely static, which can cause some framing problems. In addition, consumption can be higher because the infrared light emitting diodes are permanently on.

In FIG. 4, we find in VI the display screen, which includes an integrated circuit (such as the Signetics 2672 model sold by the Company R? C) suitable for directly managing the information coming from a photostyle, to give position indications corresponding to a microcomputer or other MO processor.

In a known manner, the CV controller controls the screen VI to make it produce the image defined by the processor.
MO. This image includes zones, at least part of which corresponds to the analysis of the screen in rows and columns by the photoemitters PL, PC, and the photoreceptors RL, RC.

The device according to the invention is the MCT block. I1 receives the composite signal from the CV controller (line 1 or 1-1).

I1 controls photoemitters and receivers PL, PC, RL,
RC, incorporated in screen VI. Finally, it returns the time signal available in 110 or 110-1 to the CV controller, which uses it as if it were a photostyle.

The signal available in 110 or 110-1 is indeed identical to that which a photostyle would provide, subject to the maintenance of synchronism between the scanning of the spot which constitutes the image, and the analysis of the latter by the photoemitters and photoreceptors. .

The time tolerance on this synchronism corresponds to the time taken by the spot to traverse the line or, in fact, the group of lines which correspond to a pair.
PL-RL (PLl-RLl for example).

Furthermore, in the described embodiments, a re-synchronization is performed at each start of frame.

In the case of FIG. 1, the control signals of the row and column 1 photoreceptors are obtained directly from the image synchronization signal, taking into account its stability, and the possibilities of the resynchronization dynamics of the monitor (cathode ray tube) of visualization.

In the case of FIG. 2, the stability of the quartz clock 41-1 mainly intervenes.

A variant of the invention would consist in carrying out physical synchronization on the spot of the cathode ray tube itself, at a predetermined point, such as the upper left and / or lower right corners of the screen. The signal thus obtained would be used to reset counters 41 and 42 (fig. 1) or counter 40-1 (fig. 2).

Claims (12)

Claims. 1. Electrical device of the touch screen type, of the type comprising a display screen (VI), operating in frame scanning mode, electronic means capable of locating a body located in the immediate vicinity or in contact with the screen, comprising transmitting organs (PL, PC) and cooperating receiving organs (RL, RC), located near the screen, so that the localization of the body is obtained thanks to the variation of a physical phenomenon such as electromagnetic waves, waves acoustic, conductivity between the transmitting and receiving organs, and electronic processing means (EP) of the signals thus obtained, characterized in that the processing of the signals received by the receiving organs (RL, RC) is carried out according to a predetermined time sequence in function of the spatial exploration of the screen so that the variation or interruption of the reception signals determines temporal information defining an indication of the position of the horn ps on the screen. 2. Electronic device according to claim 1, characterized in that it comprises control means (MC) for exciting the transmitting members (PL, PC) according to the same predetermined time sequence according to the spatial exploration of the screen . 3. Electronic device according to claim 1 or  claim 2, characterized in that there are two groups of electronic localization means (PL, PC, RL, RC), for example one corresponding to the lines of the screen, and the other to the columns, so that the signals received on each of the groups of the receiving organs together define temporal information related to the position of the body on the screen. 4. Electronic device according to one of claims 1, 2 or 3, characterized in that the control means for producing the predetermined time sequence used to excite the transmitting organs are initialized at each frame scan by the frame start signal useful of the display screen (2; 2-1). 5. Electronic device according to claim 4, characterized in that the control means comprise at least one counter (41,42; 40-1), associated with decoding circuits (61,62; 61-1,62-1 ), which selectively excite the emitting organs (PL, PC). 6. Electronic device according to claim 5, characterized in that the counter uses pulses coming from circuits for logical shaping of the synchronization signals of the display screen (2,31,32; 2-1). 7. Electronic device according to claim 5, characterized in that the counter uses pulses coming from a quartz clock (41-1). 8. Electronic device according to claim 3 and according to one of claims 5 to 7, characterized in that the control means comprise two counters (41,42) each associated with decoding circuits (61,62), each of meters and its decoding circuits cooperating with a group of transmitting units (PE, PC). 9. Electronic device according to claim 2 and according to one of claims 5 to 7, characterized in that the control means comprise a single counter (40-1), associated with decoding circuits (61-1,62- 1), so that the lower part of the counter contains the column address (PC), and the upper part the line address of the excited transmitters (PL). 10. Electronic device according to claim 6 taken in dependence on claim l or claim 2, characterized in that the detection of the signals on a group of receivers corresponding to the lines uses a memory circuit (81) of flip-flop type, and in that the signals on the other group of receivers, corresponding to the columns, are applied, as is the output of the memory circuit, to a logic AND circuit (100). 11. Electronic device according to claim 9, characterized in that the processing means of said device comprise two comparators (101-1,101-2) making it possible to compare the signals transmitted and received for a given line and column and a logic AND circuit ( 100-1) connected to the outputs of these two comparators. 12. Electronic device according to one of the preceding claims, characterized in that the processing means of said device are directly connectable to circuits for using a photostyle device.