JPH0521153Y2 - - Google Patents

Description

[Detailed description of the invention] "Field of industrial application" This invention relates to a position detection device for an optical touch screen in which input operations are performed by directly touching a CRT screen with a finger. This is an improvement so that it is not affected by ambient light.

``Prior Art'' An optical touch screen is a device in which input operations are performed by touching a CRT screen directly with a finger. Usually, a window frame with an optical detection function is placed around the display screen of the CRT screen. composed of surroundings.

An example of such an optical touch screen is shown in FIG.

That is, 1 is a CRT display screen, which is surrounded by a window frame 2.

The window frame 2 has a light emitting diode on one of two sets of opposite sides of the CRT display screen 1.
A light emitting element 21 such as an LED and a light receiving element 22 such as a photo transistor are installed on the other side. Then, the light emitting elements 21 are sequentially driven by the pulse signals to create an infrared ray grid on the CRT display screen 1.

In this state, when the operator touches the desired position on the CRT display screen 1 with his/her finger,
Light from the light emitting element 21 at a specific position is blocked, and the position touched by the operator can be determined from the position of the light receiving element 22 at this time.

In such an optical touch screen, the conventional position detection method will be described in detail.

First, perform a self-test when the power is turned on. At this time, as shown in FIG. 5, the disturbance value Vn corresponding to light other than the light emitting element 21, that is, disturbance light such as sunlight or illumination, is measured by the light receiving element 22 at timing t1, and then the light is emitted at timing t2. The element 21 is driven and the peak value Vp is measured. and,
Find the difference D between the peak value Vp and the disturbance value Vn, and use this value D
The value of 1/2 of is determined as the threshold value Vt.

Similarly, during operation, the disturbance value Vn and the peak value
The difference D from Vp is measured, this difference D is compared with the threshold value Vt, and if the difference D is smaller, it is determined that there is a touch input.

``The problem that the invention attempts to solve''
Let us now consider the case of devices such as those shown in Figures a and b.

Figure 6a shows two touch screens 30, 4.
FIG. 6b is a view from above (bottom) of the device in which touch screens 30 and 40 are placed adjacent to each other on the left and right, and FIG. be.

Each touch screen 3 on these devices
0 and 40 allow touch input operations independently.

However, since these touch screens 30 and 40 have the same configuration adjacent to each other, the light from the light emitting element 21 of the other touch screen may cause disturbance.

That is, as shown in FIGS. 6a, b and 7,
This is a case where the light from the light emitting element 21 on the touch screen 40 side is measured on the touch screen 30 side at the disturbance value measurement timing t1. At this time, the light receiving element 22 on the touch screen 30 side measures a value Vm as a disturbance value by adding the normal disturbance value Vn and the measured value of the light emitting element 21 on the touch screen 40 side.

Next, when the peak value Vp is measured at timing t2,
The difference D between the disturbance value Vm and the peak value Vp becomes smaller,
If this difference D is smaller than a preset threshold value Vt, it may be determined that a touch has been made at that position even though no touch input operation is performed on the touch screen 30 side, which may cause malfunctions. .

In FIG. 7, the solid line is the waveform of the measured value actually detected, the dotted line is the disturbance waveform from the touch screen of the other party, and the dash-dotted line is the waveform representing correct measurement.

This invention solves the above problems,
The purpose is to eliminate malfunctions due to mutual interference between adjacent touch screens.

``Means for solving the problem'' This invention measures the disturbance value twice and uses the smaller value of the disturbance value and the peak value to obtain the correct measurement value.The detailed structure is as follows. It is.

That is, a group of light emitting elements is provided on one side of two pairs of opposing sides, and a group of light receiving elements is provided on the other side, and the touched position is detected by sequentially emitting light from the light emitting elements and blocking the light reaching the light receiving elements. Tatsuchi to do
In an optical touch screen position detection device installed in a device in which two screens are placed adjacent to each other horizontally or vertically, disturbance light is detected by the first timing clock φ1 between one light-emitting element emitting light and the next light-emitting element emitting light. and a second timing clock φ2 after the holding operation of the first hold means during this interval.
a second holding means for holding the measured value of the disturbance light; and a first comparator for comparing the value of the first holding means and the value of the second holding means and selecting the smaller value. Then, at the timing when the next light emitting element emits light, the difference between the measured value of the light receiving element at this time and the value selected by the first comparator is calculated and compared with a preset threshold value to detect the position. and a second comparator.

"Operation" The device of the present invention measures the disturbance value twice at different timings, considers the smaller disturbance value as the correct disturbance value, calculates the difference from the peak value measured at the next timing, and compares it with the threshold value. to determine whether there is a touch input.

``Embodiment'' FIG. 1 is a block diagram of an optical touch screen position detection device embodying the present invention.

In this figure, 21 is a light emitting diode LED
22 is a light receiving element such as a phototransistor, which is the same as the conventional one.

23 is a first sample-and-hold circuit, and 24 is a second sample-and-hold circuit, which control the light receiving element 2 by timing clocks φ1 and φ2, respectively.
Two measurements are retained.

A first comparator 25 compares the value V1 held by the sample and hold circuit 23 with the value V2 held by the sample and hold circuit 24, and selects the smaller value.

26 is a setting device in which the threshold value Vt is set in advance.

27 is a second comparison which compares the peak value Vp of the light receiving element 22 with the value Va which is the sum of the set value Vt of the setter 26 and the value from the comparator 25 at the timing clock φ3 and outputs the magnitude relationship. It is a vessel.

The timing clocks φ1, φ2, and φ3 are as shown in FIG.
Each element operates in sequence in a level.

For details, refer to “H” of timing clock φ3.
The level defines the timing for sequentially driving each light emitting element in the light emitting element group, and the timing from the "H" level of this timing clock φ3 to the next "H"
During the period up to this level, that is, the time between emitting light from one light emitting element and emitting light from the next, timing clocks φ1 and φ2 go to the "H" level in this order, dividing this period into roughly three equal parts. Generate timing. Timing clock φ1 is the sample timing of the first sample and hold circuit 23, timing clock φ2 is the sample timing of the second sample and hold circuit 24, and timing clock φ3 is the timing for driving the light emitting element. At the same time, the timing for detecting the light from the light emitting element at this time and determining the presence or absence of a touch input is defined.

The device of the present invention having such a configuration operates as follows.

When the power is turned on, the threshold value Vt is calculated as shown in FIG. 5 in the same way as the conventional device. This threshold value Vt is set in the setter 26 for each element, taking into consideration variations in the characteristics of each light emitting element 21 and light receiving element 22.

Next, when the operation starts, the light emitting elements 21 facing each other in the window frame 2 of the CRT display screen 1
and the light receiving element 22 are sequentially scanned and measured. To explain step by step, as shown in FIG. 3a, at timing φ1, the disturbance light is measured without driving the light emitting element 21. The measured value at this time is set as V1 and held in the sample-and-hold circuit 23. Next, the disturbance light is similarly measured at timing φ2, and the measured value V2 is held in the sample/hold circuit 24.

At this point, the comparator 25 outputs the hold value V1 or
Select the smaller of V2. In this diagram, V1
<V2, and the comparator 25 selects the measured value V1,
Furthermore, the threshold value Vt is output from the setting device 26 and the measured value
Added to V1. Let the added value be Va.

Then, the light emitting element 21 is driven at timing φ3, and the measured value Vp of the light receiving element 22 at this time is detected.

Next, the comparator 27 compares the added value Va and the measured value Vp, and if the measured value Vp is smaller, it is determined that there is a touch input. That is, the measured value Vp and the disturbance value
This is equivalent to comparing the difference with V1 and the threshold value Vt.

Here, with conventional devices, the disturbance light is detected only once, so the light reception value is measured when the light from the adjacent touch screen is incident at the timing of measuring the disturbance light. However, the device of the present invention changes the timing of the disturbance light and detects it as a touch.
This eliminates the possibility of erroneous judgments as in the conventional method, since the difference is measured and the smaller one is selected.

Moreover, as shown in FIG. 3b, the timing φ1
Even if disturbance light is incident on the device, normal operation is possible because the disturbance value V2 measured at timing φ2 is used.

As shown in FIG. 3c, even if disturbance light is incident at the timing φ3 at which the peak value Vp is measured, the peak value Vp is naturally larger than the threshold value Vt, and the presence or absence of a touch input can be normally detected.

In this way, it is possible to perform touch detection on the touch screen without being affected by the timing of incident disturbance light, so it is possible to detect touch screens 30 and 40 by placing two touch screens 30 and 40 adjacent to each other as shown in FIG. There is no mutual interference even when installed.

In the embodiment described above, the configuration is shown in which the disturbance light is measured twice between the times when the light emitting element emits light, but the number of times the disturbance light is measured may be two or more times. However, since the device configuration may become complicated, it is appropriate to repeat the process twice.

"Effect of ideas" According to the device of the present invention, the following effects can be obtained.

By detecting the disturbance light twice and considering the smaller value as the correct disturbance value, normal operation can be achieved regardless of the timing of the disturbance light, and even devices with two touch screens can communicate with each other. The presence or absence of a touch can be detected without any influence, improving the reliability of the device.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an optical touch screen position detection device embodying the present invention, and Fig. 2 a, b, and c show timing clocks φ1, φ2, and φ3 provided to the device of the present invention. Waveform diagrams, Figures 3a, b, and c are waveform diagrams representing the operation of the device of the present invention, Figure 4 is a diagram representing a normal touch screen, and Figure 5 is a waveform diagram for determining the touch screen threshold. , Figures 6a and b are diagrams showing a device using two touch screens, and Figure 7 is a waveform diagram when a disturbance from the other side is incident on the device shown in Figures 6a and b. be. 1...CRT display screen, 2...Wind frame, 21...Light emitting element, 22...Light receiving element, 3
0, 40...Touch screen, 23...1st
sample and hold circuit, 24... second sample and hold circuit, 25... first comparator, 2
6...Setter, 27...Second comparator.

Claims (1)

[Scope of utility model registration request] A touch device in which a group of light-emitting elements is provided on one side of two pairs of opposing sides and a group of light-receiving elements is provided on the other side, and the light-emitting elements are made to sequentially emit light to block the light reaching the light-receiving element, thereby detecting the touched position.・In an optical touch screen position detection device installed in a device in which two screens are placed adjacent to each other on the left and right or top and bottom, a disturbance is detected at the first timing clock φ1 between one light-emitting element emitting light and the next light-emitting element emitting light. a first hold means for holding the measured value of the light; and a second hold means for holding the measured value of the disturbance light at a second timing clock φ2 after the holding operation of the first hold means during this interval; ,
a first comparator that compares the value of the first holding means and the value of the second holding means and selects the smaller value; Position detection of an optical touch screen having a second comparator that calculates the difference between the measured value of the light receiving element and the value selected by the first comparator and compares it with a preset threshold value to detect the position. Device.