JPH02242417A - Method for adjusting sensitivity of light receiving element of optical type touch panel - Google Patents

Abstract

PURPOSE:To surely detect a light shielding object by adjusting light receiving sensitivity so that the level difference of light receiving output signals in the light non-emitting time and light emitting time of a light emitting element can approach a prescribed value by switching a load on a light receiving element. CONSTITUTION:The levels of the light receiving output signals of the light receiving element 12a in the light non-emitting time and light emitting time of the light emitting element 11a are compared by sweeping and driving all the unit optical systems according to a check program assembled in a CPU 23. And the load resistance value of the light receiving element 12a is increased and the light receiving sensitivity is increased for the unit optical system in which no level difference between the above levels arrives at the prescribed value by switching the load resistance block 20 of the unit optical system 10 including an element whose performance is lowered to a resistor having a high resistance value. Also, when excessive disturbance light exists, the light receiving sensitivity is lowered by reducing the load resistance value of the light receiving element 12a. Thereby it is possible to omit complicated work and time required for a checking operation, and also, to use a device even at a place where the excessive disturbance light exists, and to always and accurately perform the detection of the light shielding object.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for adjusting the sensitivity of a light receiving element used in an optical system of an optical touch panel to an appropriate value.

[Conventional technology]

FIG. 3 is an explanatory diagram of the optical touch panel.

In FIG. 3, 11 is a light emitting element row, 11a is a light emitting element,
12 is a light receiving element array, 12a is a light receiving element, 13 is a display,
14 is a light shielding object.

The optical touch panel has a light emitting element array 11 in which a large number of light receiving elements 11a that emit infrared rays are arranged at regular intervals in the vertical and horizontal directions around the front surface of a display 13 such as a CRT, and the same number of light emitting elements 11a as the light emitting elements 11a. Light receiving element 12 that receives infrared light
A unit optical system is formed in such a way that a pair of light emitting elements 11a and a light receiving element 12a facing each other operate in conjunction with each other, and the unit optical system is arranged vertically and horizontally. A matrix of infrared rays is formed on the display surface of the display device by sequentially sweeping in the direction of This is output as position information of the object.

The operation of the conventional optical touch panel will be explained with reference to FIGS. 4 and 5. FIG. 4 is an explanatory diagram of the configuration of a conventional unit optical system of an optical touch panel, and FIG. 5 is an explanatory diagram of the operation of the unit optical system shown in FIG. 4.

In FIG. 4, 11a is a light emitting element, 12a is a light receiving element,
15a, 15b are analog switches, 16 is an amplifier, 1
7 is a load resistance, 18 is a light receiving output signal, and VCC is a power supply. In addition, in FIG. 5, (a) is the light receiving element drive signal;
(b) is the light emitting element drive signal, [→ is the waveform of the light reception output signal 18, (b) is the low level signal reading pulse, and (e) is the high level signal reading pulse.

As described above, a plurality of unit optical systems are provided, and the output of each light receiving element 12a is connected to the input of the amplifier 16 in parallel.

These unit optical systems are sequentially swept according to the program of the CPU (not shown), but when one unit optical system is swept, the analog switch 15a is connected by the light receiving element drive signal (A) output from the CPU. Thus, the light receiving element 12a becomes operational. Subsequently, after a certain period of time, the analog switch 15b is activated by the light emitting element drive signal (b).
are in contact for a certain period of time, and the light emitting element 11a emits light.

In this process, when the analog switch 15a is connected and the power supply Vcc is applied to the light receiving element 12a, the light receiving element 12
A transient current flows through a, and noculus noise is generated in the load resistor 17. This noise rapidly attenuates, and the light receiving element 12a is affected by the load resistance 1 due to the dark current and the current caused by the disturbance light.
7 generates a low level signal. Next, light emitting element 11
When a emits light, the light-receiving element 12a receives this light and generates a high-level signal. Both signals are amplified by the amplifier 16, and a signal with a waveform as shown in FIG. Output. The operation described above is CP
Since the other unit optical systems are sequentially sweep-driven according to the program in U, the e9
Since a signal having a waveform as shown in FIG. This light reception output signal 18 is converted into a digital signal by an A/D converter (not shown), and is read into a low level signal having a constant timing with the drive signals of CI) and (B). The level signal is sequentially read into a storage device (not shown) by the level signal reading unit 9 (e), and the CPU compares the low level signal and high level signal for each unit optical system to determine the level difference. The presence or absence of a light-blocking object on the display surface is determined based on the presence or size of the light-blocking object, the light-blocking intersection of the infrared ray matrix is detected, and the orthogonal coordinates of the intersection are output as position information of the object. It is.

Therefore, in order to output accurate position information, it is necessary to minimize the influence of ambient light such as indoor illumination light, so an infrared filter is provided in front of the light-receiving element row, and when the light-emitting element does not emit light, the light-receiving element The level of the received light output signal is lowered.

[Problem to be solved by the invention]

However, since optical touch panels use a large number of light-emitting elements and light-receiving elements, if they are operated for a long period of time, dust may accumulate on the infrared filter provided in front of the light-receiving element array, or the unit optical system may become damaged. The performance of some of the large number of pixel elements to be formed gradually deteriorates, and the level of the light receiving output signal of the light receiving element at the time of light emission decreases. For this reason, when a low level signal when no light is emitted and a high level signal when light is emitted are compared, and the level difference between the two signals no longer reaches a predetermined value, it may become impossible to detect the presence or absence of a light blocking object.

In such a case, if the infrared filter is cleaned and normal detection is still not possible, there is a problem in that it requires complicated work and a lot of time to find and replace the defective element.

However, depending on the location where the optical touch panel is installed, it may be affected by indoor lighting or other external light, and if the external light is strong, the received light output signal will become saturated, and the level difference between the two signals will almost disappear. Second, there was a problem in that it was impossible to detect the presence or absence of a light-blocking object.

The present invention automatically corrects malfunctions caused by the accumulation of dust and deterioration in the performance of the light-emitting element and light-receiving element when the optical touch/F panel is used for a long period of time, as well as malfunctions caused by the influence of external light. However, it is an object of the present invention to provide a method for adjusting the sensitivity of a light-receiving element so that a light-blocking object can always be accurately detected.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention incorporates a check program into the CPU in advance, and sequentially sweeps and drives the plurality of unit optical systems in a state where no light shielding object is touched on the display surface of the display device. For each unit optical system of
Compare the level difference between the received light output signal when the light emitting element does not emit light and when the light emitting element emits light, and for the unit optical system in which the level difference does not reach a predetermined value, the level difference approaches the predetermined value.
Means for increasing or decreasing the load resistance of the light receiving element of the unit optical system is provided to adjust the sensitivity of the light receiving element.

[Effect]

In an optical touch panel, the present invention sequentially sweeps and drives all the unit optical systems according to a check program built into the CPU before starting to use the panel, so that the light-emitting element for each unit optical system detects when no light is emitted. For unit optical systems in which the level difference of the light receiving output signal of the light receiving element at the time of light emission does not reach a predetermined value, the difference between the two levels is increased or decreased by increasing or decreasing the load resistance of the light receiving element of the unit optical system. Since the sensitivity of the light-receiving element is adjusted so as to approach a predetermined value, it is possible to always accurately detect a light-blocking object when using the four channels.

〔Example〕

In order to check the operating state of an optical touch panel before starting use, the present invention operates the panel without touching any light-shielding object on the display surface of the panel according to a check program built into the CPU in advance. Sweep drive the unit optical system, compare the level of the received light output signal when no light is emitted and when the light is emitted, check whether the level difference is within a predetermined value, and if the predetermined value is not obtained. If there is a unit optical system that has not been installed, the load resistance of the light receiving element of the unit optical system is switched by a command from the CPU,
This method adjusts the light-receiving sensitivity so that the level difference approaches a predetermined value, thereby reliably detecting a light-blocking object. Examples will be described below with reference to FIG. 1, FIG. 2, and FIG. 5.

FIG. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, showing the configuration of one of the many unit optical systems constituting an optical touch panel and the connection with an auxiliary circuit shared with other unit optical systems. Show relationships. In Fig. 1, 10 is a unit optical system, ll
a is a light emitting element, 12a is a light receiving element, 15a-1, 15
a-2, 15b-1, 15b-2 are analog switches,
16 is an amplifier, 16a is a cutting terminal, 18 is a light reception output signal, 19 is an analog switch block, 20 is a load resistance block, 21 is an A/D converter, 22 is an I10 port, 2
2a is a storage device, 23 is a CPU, 24 is an infrared filter, 25 is a light-receiving element drive signal, 25b is a light-emitting element drive signal, 26 is a load resistance switching signal, 27 is the output of the light-receiving element of another unit optical system, Vcc is the power supply.

Figure 2 is an explanatory diagram of the effect of adjusting the sensitivity of the light-receiving element by increasing and decreasing the load resistance value in the embodiment shown in Figure 1. (a) is a waveform diagram of the light-receiving output signal when the light-receiving sensitivity decreases, and (b) is the load resistance value. (c) is a waveform diagram of the light reception output signal after the increase, (c) is a waveform diagram of the light reception output signal when the disturbance light is excessive, and (d) is a waveform diagram of the light reception output signal after the load resistance value is decreased.

As shown in FIG. 1, both the light emitting element 11a and the light receiving element 12a of the unit optical system 10 are connected to analog switches 15
b-1, 15b-2 and one end of 15a-1, 15a-2, and analog switch 15b-1゜1
The other end of 5a-1 is connected to power supply Vcc.

The other end of 15b-2 is grounded, and the other end of 15a-2 is connected to the common connection end of the analog switch block 19, and the other ends of the individual analog switches a, b, and c of the analog switch block 19 are Individual load resistance a of each load resistance block 20.

b and c, and the other ends of the load resistors a, b, and c are grounded. The connection point A between the light receiving element 12a and the analog switch 15a-2 is still connected to the input terminal 16a of the amplifier 16.
It is connected to the. Note that the output 27 of the light receiving element of another unit optical system is also connected to the input terminal 16a. amplifier 1
6 is connected to the A/D converter 21, and the output of the A/D converter 21 is connected to the storage device 2 in Ilo, IP-) 22.
2a, and the I10 port is connected to the CPU.

According to the present invention, the unit optical system is sequentially swept without touching a light-shielding object on the display surface of the display according to a check program pre-installed in the CPU 23 before using the touch channel. When the unit optical system 10 is swept, the CPU 5
A light receiving element drive signal 25a is sent out for a certain period of time via the I10 port 22, and the analog switch 15a-1, 15
a-2 is connected, and the light receiving element 12a is connected to the power supply Vcc and is also grounded via the analog switch block 19 and the load resistance block 20. (In this embodiment, both blocks consist of three elements a, b, and c, and are connected to analog switch b and grounded through a load resistor.) A power supply Vcc and a load resistor 20b are connected to the light receiving element 12a. Then, a transient current flows through the light-receiving element 12a, and a pulse voltage is generated across the load resistor 20b, but this voltage rapidly attenuates and becomes a steady state, where a low-level signal is generated by the dark current of the light-receiving element and the current caused by the external light. occurs. Next, the light emitting element drive signal 25b is sent from the I10 port for a certain period of time, the analog switches 15b-1 and 15b-2 are connected, the light emitting element 11a emits light, and upon receiving this light, the light receiving current of the light receiving element 12a is changed to the load resistor 20b. generates a high level signal.

The light receiving element drive signal 25a is cut off, and the light receiving element 12a stops operating. If the unit optical system is normal during this series of operations, the received light output signal 18 as shown in FIG. The analog signal is converted to a digital signal, and the reading/reading shown in Fig. 5) and (e) is performed.
The low-level signal and the high-level signal are sequentially read into the storage device 22a by the lens, and the CPU 23 compares the levels of both signals for each unit optical system. If the difference in level is all within a predetermined value, it is normal. It is determined that the system is operating properly.

However, when used for a long period of time, the optical touch sensor will generate a large number of lights that make up a large number of unit optical systems.

The performance of some of the light-receiving elements may deteriorate, or dust may adhere to the surface of the infrared filter 24 provided in front of the light-receiving element array, resulting in poor light transmission partially or completely.
As shown in (,) in the figure, the light receiving output when emitting light begins to decrease. The light receiving output signal of such a unit optical system is sent to the CPU.
When the low level signal and the high level signal are compared in step 23, the level difference between the two signals does not reach a predetermined value, so the CPU 23 sends a , one load resistance switching signal 26 is sent to the analog signal switch block 19 of the unit optical system, and the analog switch corresponding to the switching signal is driven to switch to the resistor with the higher resistance value in the load resistance block 20 to increase the light receiving sensitivity. Adjust so that a waveform as shown in FIG. 2(b) is obtained. On the other hand, when the incidence of disturbance light on the light receiving element array is excessive, the light receiving output during non-emission increases as shown in FIG. 2(c). Therefore, when emitting light, the light receiving output is saturated, and the light receiving output signal 18
When the CPU 23 compares the low level signal and high level signal of The CPU 23 lowers the light receiving output of the unit optical system, and the CPU 23 sends Ilo! so that the level difference reaches a predetermined value.
-T,? ,? The load resistance switching signal 26 is sent to the analog switch block 19 of the unit optical system through the switch, the analog switch corresponding to the switching signal is driven, and the resistance of the load resistance block 20 is switched to a resistor with a lower resistance value to adjust the light receiving sensitivity. Then, a waveform as shown in FIG. 2(d) is obtained.

In the embodiment described above, the number of analog switches and load resistors that are switched by the load resistance switching signal 26 is three each, but the number is not limited to this, and the fineness of the sensitivity adjustment of the light receiving element or the sensitivity The size of the adjustment range can be changed as necessary.

〔Effect of the invention〕

As described in detail above, according to the present invention, a means for switching the load resistance of the light receiving elements of all the unit optical systems constituting the optical touch panel is provided, and a check program is installed in the CPU that processes the light reception output signal. Before starting to use the touch channel, the operation of all unit optical systems is automatically checked according to the program, and the load resistance of the light receiving element is increased for unit optical systems including elements whose performance has deteriorated.
Conventionally, we increased the light-receiving sensitivity, and when the ambient light was excessive, we lowered the load resistance value of the light-receiving element to lower the light-receiving sensitivity.
It has the effect of eliminating the complicated work and time required to check the operation, and it also automatically lowers the light receiving sensitivity so that it can be used without problems even in places with strong ambient light, so it is always stable and accurate. This is expected to have the effect of providing an optical touch panel that operates automatically.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, and FIG.
This is an explanatory diagram of the effect of adjusting the sensitivity of the light-receiving element by increasing and decreasing the load resistance value in the example shown in the figure. (a) is a waveform diagram of the light-receiving output signal when the light-receiving sensitivity decreases, and (b) is a waveform diagram of the light-receiving output signal after increasing the load resistance value. Waveform diagram, (c) is a waveform diagram of the light reception output signal when the disturbance light is excessive, (d) is a waveform diagram of the light reception output signal after the load resistance value decreases,
Figure 3 shows the optical touch screen <? FIG. 4 is an explanatory diagram of the configuration of a conventional unit optical system of an optical touch panel, and FIG. 5 is an explanatory diagram of the operation of the unit optical system of FIG. 4. 10... Unit optical system, 11... Light emitting element array, 11a
...Light emitting element, 12...Light receiving element row, 12a...
Light receiving element, 13... Display device, 14... Light blocking object, 1
5a. 15a-1, 15a-2, 15b, 15b-1, 15b
-2・°・Analog switch, 16...Amplifier, 17
...Load resistance, 18...Light reception output signal, 19...
Analog switch block, 20... Load resistance block, 21... A//D converter, 22... I10 port, 22a... Storage device, 23... CPU, 24...
... Infrared filter, 25a... Light-receiving element drive signal,
25b... Light emitting element drive signal, 26... Load resistance switching signal, 27... Output of light receiving element of other unit optical system,
Vcc is a power supply.

Claims (1)

[Claims] (1) Horizontally and vertically facing the periphery of the display surface of the display unit,
A plurality of unit optical systems in which a light-emitting element row and a light-receiving element row are disposed to form both the element rows, and a single light-emitting element and a light-receiving element facing each other are operated in conjunction with each other are horizontally arranged. is sequentially swept in the vertical direction to form an optical matrix, and for each unit optical system, the light reception output signals during non-emission and light emission are A/D converted, and the respective levels of the light reception output signals are stored in a storage device. A light-receiving element of an optical touch panel that detects a light-blocking object touched on the display surface based on the level difference obtained by comparing the levels of both signals by the CPU, and outputs orthogonal coordinates of the position of the object as position information. In the sensitivity adjustment method, a check program is installed in the CPU in advance, and the plurality of unit optical systems are sequentially sweep-driven in a state where no light blocking object is touched on the display surface, so that the light-receiving element of each unit optical system is Comparing the level of the received light output signal when not emitting light and when emitting light, for the unit optical system in which the level difference does not reach a predetermined value, the light receiving output signal of the unit optical system is adjusted so that the level difference approaches the predetermined value. A method for adjusting the sensitivity of a light receiving element of an optical touch panel, characterized in that the sensitivity of the light receiving element is adjusted by providing means for increasing or decreasing the load resistance of the element.