JPS62127928A - Optical touch panel - Google Patents

Abstract

PURPOSE:To prevent the occurrence of erroneous detection of touch input position due to external light and the occurrence of malfunction of overlooking touch input by modulating a light receiving signal by a clock signal and discriminating height of voltage of low frequency component contained in the modulated signal. CONSTITUTION:A light receiving signal is modulated by a clock signal and height of voltage of low frequency component contained in the modulated signal is discriminated. Thereby, presence or absence of touch input is detected, and by setting frequency of the clock signal sufficiently higher than frequency of a power source for illumination, it becomes possible to eliminate influences of the modulated signal on the average voltage even if voltage drop of the light receiving signal is caused by incidence of illuminating light. Accordingly, malfunction is not caused even when external light from an illuminating lamp that emits light by a power source unrelated to a light emission signal comes in.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical touch panel, and particularly to an optical touch panel for optically detecting the position of a touch input on a screen of a display device.

[Conventional technology]

Conventionally, as a touch panel for detecting the position of a touch input on the screen of a display device, a light source array is arranged on one of two opposing sides of the screen, and an array of light receiving elements paired with each light source is arranged on the other side. An optical touch panel is used that detects a touch input location by detecting a location where light emitted from a light source array is blocked during touch input.

[Problem that the invention seeks to solve]

In conventional optical touch panels, each light-receiving element receives light emitted from the original light source that is paired with it, as well as display light emitted from the screen, external illumination light, or placed close to the original paired light source. There is a problem in that light emitted from other light sources is incident, which tends to cause erroneous detection of touch input locations or malfunctions in which touch inputs are missed.

An object of the present invention is to provide an optical system that eliminates the above-mentioned problems and prevents malfunctions caused by external light by eliminating the influence of extraneous light that enters the light-receiving section from sources other than the original light-emitting section that is paired with the light-receiving section. The purpose is to provide touch panels.

[Means for solving problems]

The touch panel of the present invention is an optical touch panel provided with a plurality of light transmitting/receiving parts each having an array of light emitting elements arranged along one side of a display screen and an array of light receiving elements arranged along one side opposite thereto. In the above, the light transmitting/receiving section receives a clock signal having a predetermined first period and m times the first period (m is a predetermined natural number).
scan control data that alternately specifies one of the two light-emitting elements adjacent to each other every second period of , and after performing the designation n times (n is a predetermined natural number), steps to the next one; and a scan control circuit that generates a light emission signal in which one of a signal in phase with the clock signal and a signal in opposite phase is alternately switched every second period, and the light emission specified by the scan control data. a light-emitting set circuit that blinks an element at a timing indicated by the light-emitting signal; and switching the light-receiving element facing the light-emitting element specified by the scanning control data to an operating state to indicate whether or not the light-receiving element is receiving light. a light reception scanning circuit that generates a light reception signal; a transformer A that modulates the light reception signal with the clock signal and sends it out; a low-pass filter that suppresses high frequency components in the signal sent out from the modulator and sends out the signal; a detection circuit having a level discrimination circuit that generates a pulse when the output signal of the low-pass filter exceeds a predetermined positive or negative threshold voltage; and a detection circuit that blinks when the pulse given from the detection circuit arrives. and a gate circuit that sends scanning position data indicating the position of the light emitting element.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

1 and 2 are a block diagram and a timing diagram respectively showing a first embodiment of the present invention. In FIG. 1, a light emitting diode array 4 and a phototransistor array 6 are arranged in pairs and facing each other across the screen of the display device. Each of N light emitting diodes D or DNl (N is a predetermined natural number)
This is an array in which N phototransistors Qt to QN are arranged in a linear manner, facing each other so that the light emitted from the jth light emitting diode Dj is mainly received by the jth phototransistor Qj. The scan control circuit 1 is
A clock signal having a predetermined period is sent to the modulator 70 of the detection circuit 7, and from this clock signal, the light emitting diode D! DN% and the operation timing of the phototransistors Q1 to QN, and a light emission signal indicating the light emission timing of the light emitting diode whose operation is instructed are generated, and the scan control data is transmitted to the light emission scanning circuit 3 and the light receiving circuit 3. The light emitting signal is sent to the scanning circuit 5, and the light emission signal is sent to the light emission scanning circuit 3. Light emission scanning time lol! As will be described later, r3 sequentially specifies two adjacent pairs of light emitting diodes in the light emitting diodes D or DN according to the scan control data and the light emitting signal, and selects the two light emitting diodes of the specified pair. flash alternately. In response to the scan control data, the light reception scanning circuit 5 applies a bias voltage to the phototransistor Qj facing the light emitting diode Dj whose light emission timing is specified, switches it to an operating state, and indicates whether or not light is received by the phototransistor Qj. A voltage signal is generated and sent to the sensor 70 of the detection circuit 7 as a light reception signal. The modulator 70 is an amplitude modulator, and amplitude modulates the received light signal using the clock signal as a carrier wave. A low-pass filter (LPF) 71 suppresses high frequency components of the modulated signal sent from the modulator 70 and sends low frequency components to the level discrimination circuit 72. The level identification circuit 72 generates a pulse when the signal voltage sent from the LPF 71 rises or falls above a predetermined threshold voltage, and sends the pulse to the gate circuit 2. The gate circuit 2 receives from the scan control circuit 1 the numbers j and (jet
) is being sent.

The gate circuit 2 sends out scanning position data at the time of arrival of the pulse from the level identification circuit 72 as light shielding position data.

FIG. 2 shows the light emitting diode D J+1 in this embodiment.
An example of the operation when the light emitted from Dk or Dk is blocked by a touch input will be shown. First, every m periods of the clock signal (m
is a predetermined natural number, and Figure 2 shows the case where m=2.
1 and DJ. While the scan control data specifies light emitting diodes Dj-t and Dj, the scan position data indicates the number of one of them (light emitting diode Dj-x in FIG. 2). After both are alternately designated n times each, the scan control data advances to alternately designate light emitting diodes Dj and Dj+1. Along with this, the scanning position data also increments by one. During each designated period of the light emitting diodes Dj-1 and Dj, the light emitting diode DI-, emits light at the pulse rise time of the light emitting signal that is in phase with the clock signal (phase 0), and the light emitting diode Dj emits light at the pulse rise time of the light emitting signal that is in phase with the clock signal (phase 0), and the light emitting diode Dj is in the opposite phase with the clock signal. Light is emitted at the pulse rise time of the phase (phase π) light emission signal. On the other hand, the light reception signal is generated by the light emitting diode specified by the travel control data (for example, Dj).
It shows whether or not the phototransistor (for example, Qj) facing the phototransistor (for example, Qj) is receiving light. When not receiving light, the voltage is at a high level V, and when receiving light, it drops to a low level voltage VL. The output signal from the modulator 70 has a voltage waveform of the same polarity as the light reception signal during the pulse rise time of the clock signal, and has a voltage waveform of the opposite polarity to the light reception signal during the short pulse fall time of the clock signal.

In the case illustrated in FIG. 2, the light emitting diode 1)j-1
During the period in which DJ and DJ are blinking alternately, the light emitted from both is not blocked and is received by phototransistors Qj- and Qj. During this period, the average voltage of the output signal from the modulator 70 is zero as shown in FIG.
71 and the DC component obtained also becomes zero. Immediately after this, during the period in which the light emitting diodes DJ and Dj are blinking alternately, the light emitted from the light emitting diode DJ+1 is blocked, and as a result, the average value of the output signal of the modulator 70 is a non-zero negative value. If there is no value, the DC component obtained by passing this through the LPF 71 also becomes a negative value. The level identification circuit 72 in FIG. 1 generates a pulse when the voltage of the output No. 41 of the LPF 71 falls beyond the negative threshold voltage -vs, and receives the scanning position signal (j) from the gate circuit 2. Send it as light shielding position data. After this, light emitting diode D
Between the alternate blinking period of j+1 and Djet and the alternate blinking period of light emitting diodes Dk-1 and Dk, all light emitted from the light emitting diodes is blocked, and the LP
The sending number I100 of F71 becomes zero. Then, when the light emitting diodes Dk and Dk+□ alternately blink, only the light emitted from the light emitting diode Dk is blocked, and as a result, the output signal of the LPF 71 becomes a positive value. The level identification circuit 72 in FIG. 1 generates a pulse when the voltage of the output signal from the LPF 71 rises above the positive threshold voltage +Vs, and outputs a pulse from the gate circuit 2 to the position signal (k). is sent as light-shielding position data. According to the above-mentioned two light-shielding position data (j) and (k), the light-shielding point due to manual touch is determined by the light path emitted from the light-emitting diode Dj+1 and received by the phototransistor Qj+1, and the light beam path emitted from the light-emitting diode Dk and received by the phototransistor Qlc. It can be detected that there is a path between the received light beam and the received light beam path. Therefore, the light emitting diode array 4 and the phototransistor array 6
By arranging two sets of orthogonal to each other, it is possible to detect a touch input point on the display screen.

FIGS. 3(a) and 3(b) are a block diagram showing one adjacent arrangement of the scan control circuits 1 in this embodiment and a timing chart for explaining its operation, respectively.

After the clock signal is frequency-divided by m in m-frequency divider 10, it is sent to 2-frequency divider 11, inhibit gate 20, and inverter 15 as signal a. The 2-frequency divider 11 divides the m-divided signal by 2 and divides the signal obtained by dividing the frequency by 2 into a clip 70 tube (F
F) 12 and 18 to exclusive OR gate 16. On the other hand, the signal a whose level has been inverted after passing through the inverter 15 is sent to the FF 12 and the 2n frequency divider 17. The 2n frequency divider 17 further divides the signal a by 2n (Φ in the same figure).
exemplifies the case where n==3)) and sends it to the FF 13 and the exclusive OR gate 19. FF
12 and 18 are D-type 7-lip 70-tug), and at every pulse rising edge sent to the input terminal C,
The level of the signal sent to the input end is read and the level is maintained until the next pulse rise, and the signals are sent out from the output ends Q and Q as signals g and d, respectively. Exclusive OR gate 19 fed with signals C and d generates signal e indicating the exclusive OR of both signals.
C inhibit gate 20 and gate circuit 14 - send. The prohibition gate 20 prohibits the pulse transmission of the signal a only during the pulse rising period of the signal e, and outputs the pulse to the counter 13 as the signal f.
sent to. The counter 13 is an up-down counter fi, which uses the signal 9 given from the FF 12 as an up-down control signal, and counts up or down the pulse rising edge of the signal f depending on whether the signal g is at a high level or a low level. Then, scan control data indicating the count result is generated and sent, and is also sent to the gate circuit 14.

The gate circuit 14 reads the scanning control data at the rising edge of the pulse of the signal e, and transmits it as scanning position data while holding the value until the rising edge of the next pulse of the signal e.

Scanning 1t obtained by the circuit of FIG. 3 (jL)! As shown in the same figure, for example, from time tj to time tj, 1st shift (j-1) and j are alternately changed every m times the period of the clock signal. (b) of the same figure shows the case where n = 3), and then advances to alternating repetition of values j and (j+1). On the other hand, in synchronization with this alternating repetition, the rising and falling pulses of the signal S appear alternately, and by applying the signal S and the clock signal to the exclusive OR gate 16, it is possible Luminescence signals can be generated alternately.

Figure 4 shows the light emitting unit and light receiving unit in this embodiment (see Figure 1), that is, the light emitting scanning circuit 3 and the light emitting diode array 4.
, a light receiving scanning circuit 5, and a phototransistor array 6. FIG. In the light emitting part,
The light emitting diode array 4 is divided into a plurality of light emitting diode subarrays 40, and the light emitting scanning circuit 3 sequentially scans the diodes in each light emitting diode subarray 40 in response to the lower bits of the scan control data. The light emitting diode subarray 40 is divided into two parts: a scanning switch 31 for applying a light emitting signal, and a scanning switch 32 for sequentially scanning the light emitting diode subarray 40 and connecting it to ground in response to the upper bits of the scanning control data. In the light receiving section as well, the phototransistor array 6 is divided into a large number of phototransistor subarrays 60 corresponding to the division in the light emitting section, and the light receiving scanning circuit 5 is divided into two scanning switches 51 and 52.

The scan switch 51 sequentially scans the phototransistors in each phototransistor subarray 60 in response to the lower bits of the scan control data, and applies a voltage +vD via the resistor R.
Apply. Further, the scan switch 52 sequentially scans the phototransistors 60 in response to the upper bits of the scan control data and connects them to ground. A voltage signal at the other end of the resistor R to which a voltage +vD is applied to one end is a light reception signal, and a voltage drop occurs due to the photocurrent flowing through the resistor R when light is received. By configuring the light-emitting section and the light-receiving section to be divided into n parts, it is possible to avoid congestion of connection wiring.

In the first embodiment described above, when external light such as illumination light is incident on the phototransistor of the light receiving section, the voltage of the light receiving signal in FIG. 2 decreases accordingly. A conventional touch panel that detects the presence or absence of a touch input based on the presence or absence of a voltage drop in a light reception signal will malfunction if the intensity of external light exceeds a certain limit. However, in this embodiment, the presence or absence of touch input is detected by modulating the light reception signal with a clock signal and identifying the voltage height of the low frequency component included in this modulation signal. By setting the frequency of the power source sufficiently higher than the frequency of the lighting power supply, even if the voltage of the received light signal decreases due to the incidence of illumination light, it will not affect the average voltage of the modulation signal. It is possible to prevent malfunctions even when external light from a lighting lamp or the like that emits a lot of light is generated by a power source that has no correlation with the light emission signal.

FIG. 5 is a block diagram showing a second embodiment of the present invention. The figure shows the effect of mutual exchange of light between the two systems when two systems of the circuit shown in Figure 1 are installed in one touch panel, and the optical path cannot be blocked between the light emitting part and the light receiving part of both systems. An example of a configuration for operating both systems simultaneously while removing the is shown below. - The two systems are referred to as A system and B system, respectively, and each block of both systems is given the same reference number as in FIG. 1 followed by A or B indicating the system. A clock signal serving as a reference for operation timing is sent to the A system as is, and is sent to the B system after passing through a phase shifter 8. The phase shifter 8 is a phase shift circuit for shifting the clock signal by a phase angle of 90°. In system A, the phototransistor array 6A receives incident light from the light emitting diode array 4A as shown by the solid line arrow, incident light from the light emitting diode array 4B as shown by the broken line arrow, and external light such as illumination light. Receive light. The light emission signal in the B system is a signal obtained by shifting the phase angle of the light emission signal in the A system by 90°, since the clock signals of both systems have a phase difference of 90° as described above. Therefore, when the light emitted from the light emitting diode array 4B enters the phototransistor 6A and changes the voltage waveform of the light reception signal, after being modulated by the clock signal of the A system in the detection circuit 7A, the light emitted from the diode array 4B is Regardless of whether the touch input is shaded or not, the modulation waveform of the component corresponding to the change in the voltage waveform described above has the same amplitude and opposite polarity immediately before and after each pulse rise and fall of the clock signal. Therefore, it has no effect on the average voltage. Furthermore, it is possible to avoid the influence of any external light, such as illumination light, as in the case of the first embodiment. Similarly, in the B system, the influence of both the incident light from the A system and external light such as illumination light can be removed.

This second embodiment can be used, for example, when two systems are used to mutually transmit and receive light to detect the abscissa and ordinate, or when two light transmitting and receiving arrays are used to detect a position in one direction. If applied when there is mutual exchange of light between the two systems when speeding up scanning by dividing the system into systems and scanning both systems simultaneously, the influence of mutual exchange of light can be easily removed.

〔Effect of the invention〕

As explained above, the present invention eliminates the influence of extraneous light that enters the light receiving section from a source other than the original light emitting section that is paired with the light receiving section, thereby overlooking erroneous detection of touch points and touch input caused by extraneous light. This has the effect of realizing an optical touch panel that prevents malfunctions.

[Brief explanation of drawings]

FIGS. 1, 3(a), 4, and 5 are block diagrams each showing an embodiment of the present invention, and FIGS. 2 and 3(b) each illustrate the operation of the embodiment of the present invention. FIG. 1. IA, IB...Scan control circuit, 2, 2A,
2B...Gate circuit, 3, 3A, 3B...
...Emission scanning circuit, 4゜4A, 4B...Light emitting diode array, 5,5A, 5B...Light reception scanning circuit, 6,6A, 6B...Phototransistor array , 7, 7A, 7B...detection circuit, 70...
...Modulator, 71 ...Low pass filter (LP
F), 72...level identification circuit, 8...
...Phase shifter, 10...m Frequency divider, 11...
...2 frequency divider, 12, 18...Flip-flop (FF), 13...Counter, 14...
...Gate circuit, 15...Inverter, 16.
19...Exclusive OR gate, 17...
・2B frequency divider, 20...Prohibition gate, 31,3
2,51.52...Scanning switch, 40...
...Light emitting diode subarray, 60...Phototransistor subarray, D, ~DN ......
Light emitting diode, Qj~QN ・・・・・・Phototransistor No. 2 / Concave No. 2 Fig. 3 Concave

Claims (2)

[Claims] (1) In an optical touch panel provided with a plurality of light transmitting/receiving sections each having an array of light emitting elements arranged along one side of the display screen and an array of light receiving elements arranged along one side opposite thereto, the above-mentioned The light transmitting/receiving unit receives a clock signal having a predetermined first period and m times the first period (m is a predetermined natural number).
scan control data that alternately specifies one of the two light-emitting elements adjacent to each other every second period of , and after performing the designation n times (n is a predetermined natural number), steps to the next one; and a scan control circuit that generates a light emission signal in which one of a signal in phase with the clock signal and a signal in opposite phase is alternately switched every second period, and the light emission specified by the scan control data. a light-emitting scanning circuit that causes the element to blink at a timing indicated by the light-emitting signal; and a light-emitting scanning circuit that switches the light-receiving element facing the light-emitting element specified by the scanning control data into an operating state to indicate whether or not the light-receiving element is receiving light. a light reception scanning circuit that generates a light reception signal; a modulator that modulates the light reception signal with the clock signal and sends it out; a low pass filter that suppresses high frequency components in the signal sent out from the modulator and sends out the signal; a detection circuit having a level identification circuit that generates a pulse when the output signal of the band pass filter exceeds a predetermined positive or negative threshold voltage; and the light emission that blinks when the pulse given from the detection circuit arrives. An optical touch panel comprising: a gate circuit that sends scanning position data indicating the position of an element. (2) A phase shifter is provided to shift the phase of the clock signal of some of the plurality of light transmitting/receiving units by 90 degrees and transmitting the signal, and the sending signal of the phase shifter is sent to the other light transmitting/receiving units. Claim (1) wherein the clock signal is provided as the clock signal.
Optical touch panel described in section.