JPH09231888A - Optical touch switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent light receiving elements from breakdown and facilitate the restitution of the circuit operation by furnishing an external light sensing element which is installed near the group of light receiving elements and senses the external light, and installing a comparing means and a current feed stop means. SOLUTION: Light emitting elements for touch sensing 3 are installed at two adjoining edges of an operating panel 1, and at the remaining two edges, a plurality of light receiving elements for touch sensing 4 are installed, and another light receiving element 11 for sensing external light is installed in the neighborhood of these elements 4. The light reception sensitivity of the element 11 is set lower than that of the elements 4, or the absolute rated current of the element 11 is set greater than the elements 4. In case an external light having a too large intensity has happened to intrude, the light is sensed by the element 11 before a current exceeding the absolute rating flows to the elements 4, and upon judgement by a comparing means, current feed to them is stopped by a current feed stop means. Thus the elements 4 can be precluded from breakdown by an excessive current exceeding the absolute rating, and even after this stop of current feed, the external light can be sensed by the element 11, and current feed to the elements 4 is restituted when the external turbulent light weakens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical touch switch having a light emitting element on two sides of a quadrangle adjacent to each other and a plurality of light receiving elements on the remaining two sides.

[0002]

2. Description of the Related Art Conventionally, there are optical touch switches described in Japanese Utility Model Laid-Open No. 63-31439 and Japanese Utility Model Laid-Open No. 3-103536, which have a schematic structure as shown in FIGS. 5 and 6, for example. ing.

That is, in a general optical touch switch, a plurality of light emitting elements 3 are arranged on each of the vertical and horizontal sides of the coordinate input surface 2 of the operation panel 1, and a plurality of phototransistors and photodiodes are provided on the remaining vertical and horizontal sides. Etc. are arranged. The light emitting elements 3 and the light receiving elements 4 are in a one-to-one correspondence in a matrix, and when the operator touches the coordinate input surface 2 with the finger 5, each light emitting element 3 moves to the light receiving element 4 at the opposite position. The path of the light is blocked, the position of the blocked set of the light-emitting and light-receiving elements 3 and 4 is introduced, and the coordinates of the position touched by the finger 5 on the coordinate input surface 2 are calculated.

FIG. 7 shows an example of a circuit showing an outline of a conventional so-called optical touch panel.
However, the light emitting element 3 and its drive circuit are omitted for simplicity. Reference numeral 8 in FIG. 7 indicates a light receiving signal processing circuit including the light receiving element 4. Here, the phototransistors PTr1, PTr2, ..., PTrn are used as the light receiving elements 4, and the emitters thereof are connected to the selectors (transistors) Q1, Q2, ..., Qn arranged on the ground side. The collector of the light receiving element 4 is connected to the negative input terminal of the comparison circuit 7, and the power source Vc is supplied via the resistor Ra.
It is commonly connected to the switch element Q0 for supplying c and is installed via a pull-down resistor Rb (Ra << R
b). The positively fed back positive input terminal of the comparison circuit 7 is held at a constant potential by the power source voltage dividing resistors R1 and R2, and this constant potential is compared with the state of the light receiving element 4 connected to the negative input terminal. The result of the calculation is input to the input terminal (I
N). The selectors Q1, Q2 and
The base of Qn is the selection signal output terminal OUT of the control unit 6.
1, OUT2, ..., OUTn, and the base of the switch element Q0 is the switch signal output terminal OUT of the control unit 6.
Connected to 0.

In the above-mentioned configuration, the control section 6 gives a pulse wave having a constant width at regular time intervals from the first selection signal output terminal OUT1 to the nth selection signal output terminal OUTn as shown in FIG. As shown in FIG. 9, each light emitting element 3 (LED
1, LED2, ..., LEDn) and each light receiving element 4 (PT
r1, PTr2, ..., PTrn) are sequentially designated.

In the optical touch switch having the above structure, the control section 6 sequentially applies a pulse wave having a constant width from OUT1 to OUTn at regular time intervals. And for example O
When a high level signal is output to UT1, LED1
Emits light. Here, when the operator does not operate the panel (Tα in FIG. 8), PTr1 is in the light receiving state, and I
N becomes High level. Hereafter, OUT2 to OUT
LED2 to LEDn sequentially emit light as the output of the control unit 6 sequentially goes to High level until n, and PTr2 to PTr2
PTrn enters the light receiving state, and IN becomes High level each time. In this way, the light from each light emitting element 3 is given to all the light receiving elements 4, and as a result, the output (IN) from the comparison circuit 7 is H of OUT0 to OUTn.
The control unit 6 recognizes that the panel operation is not performed by detecting the fact that the control unit 6 is in the High state in synchronization with the high signal.

On the other hand, when the operator operates the panel, the light directed from any one of the light emitting elements 3 to the corresponding light receiving element 4 is blocked. For example, assume that the X portion in FIG. 9 is pressed with a finger. Then, the control unit 6 causes the first light receiving element (P
Tr1) and the nth light receiving element (PTrn) are designated, that is, pulse waves are output from the first selection signal output terminal OUT1 and the nth selection signal output terminal OUTn as Tβ in FIG. Also the light receiving element (PTr1, PTr
Since the light to n) is blocked by the finger before receiving it,
The output (IN) from the comparison circuit 7 is in the Low state, and the control unit 6 detects that fact and recognizes that the panel operation has been performed for the portion X in FIG.

[0008]

In the case of the above optical touch switch, when it is used in a place where the intensity of sunlight is strong, ambient light may be incident on the light receiving element 4. When ambient light enters the light receiving element 4 in this way,
The disturbance light and the light from the light emitting element 3 may be combined to receive light having a large intensity unexpectedly. As described above, when an unexpectedly large current exceeding the absolute rating flows in the light receiving element 4, the light receiving element 4 may be destroyed before the current supply to the light receiving element 4 is stopped.

As a measure against the above problems, Japanese Patent Laid-Open No. 5-300
As described in Japanese Patent Publication No. 097, there is a device that protects the circuit by cutting off the power supply of the circuit when an excessive input is applied, but when the excessive input disappears because the function of the circuit itself is stopped. There was a problem that it could not detect that the excessive input had disappeared and could not automatically recover from the circuit protection state.

In view of the above problems, it is an object of the present invention to provide an optical touch switch which can prevent damage to a light receiving element and can easily restore the circuit operation.

[0011]

According to the present invention, a light emitting element group is arranged on two adjacent sides of four vertical and horizontal sides of a coordinate input surface, and a light receiving element group is provided on two sides facing the light emitting element group. In an optical touch switch that is arranged and detects the input coordinates based on the output of the light receiving element of the light receiving element group in which the light path on the coordinate input surface is blocked, the optical touch switch is arranged in the vicinity of the light receiving element group. A disturbance light detection element for detecting disturbance light, a comparison means for comparing and judging whether or not the intensity of the disturbance light detected by the disturbance light detection element is equal to or more than a predetermined reference value, and the comparison means Current supply stop means for stopping the current supply to the light receiving elements of the light receiving element group when the intensity of the ambient light detected by the ambient light detecting element based on the signal is equal to or higher than a predetermined reference value.

In this case, the light receiving sensitivity of the ambient light detecting element is set smaller than that of the light receiving element of the light receiving element group, or the absolute rated current of the ambient light detecting element is set to be larger than that of the light receiving element of the light receiving element group. .

Preferably, at least one disturbance light detecting element is arranged on each of two sides facing the light emitting element group.

[0014]

1 is a schematic view showing an optical touch switch according to an embodiment of the present invention. In addition, in this embodiment, elements having the same functions as those described as the related art are denoted by the same reference numerals. In this optical touch switch, as shown in FIG. 1, of the four sides of the rectangular operation panel 1, the touch detection light emitting elements 3 are arranged on two adjacent sides, and the touch detection light receiving elements 4 are arranged on the remaining two sides. In addition to the above, at least one or more ambient light detecting light receiving elements 11 (ambient light detecting elements) are provided in the vicinity of the touch detecting light receiving element 4. Specifically, of the four sides of the operation panel 1, the accommodating recesses 12 of the light receiving element accommodating member 12 on the two sides where the light receiving elements 4 for touch detection are arranged.
One near each central part of a (2 in total)
2) and are attached in the same direction as the touch detection light receiving element 4 so as to be sandwiched between the touch detection light receiving elements 4 located on both sides as shown in FIG. This is because the current flowing through the light receiving element for the touch panel varies depending on the incident direction of the ambient light, and thus the ambient light is detected in all the mounting directions of the plurality of touch detection light receiving elements 4. The touch detection light receiving element 4 and the ambient light detection light receiving element 11 in the housing recess 12a are protected from ambient light by the ambient light blocking cover 13 as much as possible.

Here, a phototransistor similar to a conventional one is used as the light receiving element 4 for touch detection, and further, a light receiving sensitivity lower than that of the light receiving element 4 for touch detection is used as the light receiving element 11 for detecting ambient light. Uses a transistor.

FIG. 3 shows an example of a circuit of the optical touch switch of this embodiment. However, for the sake of simplicity, the light emitting element 3
And its drive circuit are omitted. Further, in FIG. 3, the ambient light detection light-receiving element 11 and the element (1
4, R3 to R7) are shown only one by one, but in reality, as described above, a plurality (two) of the ambient light detection light-receiving elements 11 are provided, and a plurality of corresponding elements ( 2)
It is provided. The received light signal processing circuit 8 in FIG. 3 is the same as that described in the related art, and the control unit 6
A pulse wave having a constant width is given from the first selection signal output terminal OUT1 to the nth selection signal output terminal OUTn at constant time intervals, and each light receiving element 4 (PTr1, PTr2, ...,
PTrn) are sequentially designated, and the presence or absence of light reception is detected for each light receiving element 4.

The emitter of the ambient light detecting light receiving element 11 is grounded, and the collector thereof is a second circuit provided separately from the comparison circuit 7 (first comparison circuit) for detecting the current value of the light receiving element 4. Is connected to the negative input terminal of the comparison circuit 14 (comparison means) and is connected to the power source V via the current limiting resistor R3.
connected to cc. The output terminal of the second comparison circuit 14 is connected to the power supply Vcc via the pull-up resistor R6, is connected to the disturbance light detection input terminal (CHECK) of the control unit 6, and is also positive via the feedback resistor R7. Positive feedback is applied to the input terminal. The positive input terminal of the second comparison circuit 14 is held at a constant potential by the power source voltage dividing resistors R4 and R5, and the constant potential and the ambient light detection light-receiving element 11 connected to the negative input terminal. The result of comparison with the state is transmitted to the disturbance light detection input terminal (CHECK) of the control unit 6. The control unit 6 and the switch element Q0 for supplying the power source Vcc constitute the "current supply stopping means" described in the claims of this specification.

In the above structure, when there is no ambient light or the ambient light is smaller than a predetermined intensity, it is second compared that the current value flowing through the ambient light detecting light-receiving element 11 has not reached a predetermined reference value level. The circuit 14 makes a determination, and according to the result of the determination, a Low signal is transmitted to the disturbance light detection input terminal (CHECK) of the control unit 6. Based on this signal, the control unit 6 turns on the switch element Q0. As a result, the same operation as that described in the related art is performed, as indicated by the portion indicated by reference numeral T1 in FIG.

That is, the control unit 6 controls the output from OUT1 to OU.
A pulse wave with a constant width is sequentially applied at regular time intervals up to Tn. For example, when a high level signal is output to OUT1, LED1 (not shown) emits light and PTr1 enters the light receiving state. Here, when the operator does not perform the panel operation (Tα in FIG. 4), at this time, LE is set to PTr1.
If the light of D1 is transmitted, the output (IN) of the comparison circuit 7 is Hi.
gh level. In this way, each light emitting element 3
The light from is given to all the light receiving elements 4, and as a result,
The output (IN) from the comparison circuit 7 enters the High state in synchronization with the High signals OUT0 to OUTn, and the control unit 6
Detects that fact and recognizes that no panel operation is performed.

Also, when the operator operates the panel (Tβ in FIG. 4), the light from each light emitting element 3 is given to all the light receiving elements 4 as in the case of the prior art. Since it is cut off before being turned on, the output (IN) from the comparison circuit 7 is maintained in the low state.

On the other hand, when the ambient light enters above the specified intensity, the second comparison circuit 14 indicates that the current value flowing through the ambient light detecting light-receiving element 11 is above a predetermined reference value level. Judgment is made and a High signal is transmitted to the disturbance light detection input terminal (CHECK) of the control unit 6 according to the judgment result. Based on this signal, the control unit 6 turns off the switch element Q0. As a result, the code T2 in FIG.
All the light receiving elements 4 (PTr
, PTr2, ..., PTrn) is stopped. Therefore, even if the unexpected strong disturbing light is applied to the light-receiving element 4 for touch detection, each light-receiving element 4 (PTr1, PTr1
It is possible to prevent an overcurrent from flowing through Tr2, ..., PTrn), and thus to prevent element destruction of each touch detection light receiving element 4.

Here, while the current supply to the light-receiving element 4 for touch detection is stopped, the operation display of the touch panel is turned off and a touch panel such as "The touch panel does not work because the ambient light is strong right now" is used on the screen. A message indicating that you cannot do it and the cause of it is displayed. This informs the operator that the panel operation has been interrupted,
Avoid any discomfort during use.

Next, when the intensity of the ambient light decreases and becomes less than the prescribed value, the second comparison circuit 14 which has received the signal from the ambient light detecting light receiving element 11 promptly judges that,
The control unit 6 turns on the switch element Q0 again like the portion indicated by the reference numeral T3 in FIG. Then, the control unit 6 sequentially transmits selection signals from the selection signal output terminals (OUT2 in the example of FIG. 4) corresponding to the light receiving elements 4 that have stopped the current supply, and the succeeding light receiving elements 4 (the example of FIG. 4). Then PT
The light receiving process for r2, ..., PTrn) is continued as in the conventional case, and it is detected whether or not the panel operation is performed.

As described above, the ambient light detecting light receiving element 11 is separately provided around the touch detecting light receiving element 4 and the current supply to the touch detecting light receiving element 4 is stopped when the intensity of the ambient light is high. It is possible to prevent the touch detection light receiving element 4 from being broken. Further, since the phototransistor having lower light receiving sensitivity than the light receiving element 4 for touch detection is used as the light receiving element 11 for detecting ambient light, even if the ambient light having an unexpectedly large intensity is received, It is possible to prevent an overcurrent exceeding the absolute rating from flowing in the light receiving element 11 for detection, and to prevent element destruction of the light receiving element 11 for detecting ambient light.

In addition, when the intensity of the ambient light becomes weak again, the second comparison circuit 14 which receives the signal from the light receiving element 11 for detecting the ambient light promptly judges that fact.
The normal operating state can be immediately returned to.

In the above embodiment, the light receiving element 11 for detecting ambient light has a light receiving sensitivity lower than that of the light receiving element 4 for touch detection, but the light receiving element 4 for touch detection has a light receiving sensitivity. Even if it is more than the above, one having a large absolute rated current may be used, or a filter having a low light transmittance is installed in the same light receiving element 4 for touch detection to finally set the light receiving sensitivity low. You may use the thing.

Further, the number of light-receiving elements 4 for touch detection is not limited to two, and more light-receiving elements 4 may be provided.

[0028]

According to the first aspect of the present invention, when the disturbance light enters with an unexpectedly large intensity, the disturbance light detection element detects the disturbance light before the current exceeding the absolute rating flows through the light receiving element. After the disturbance light is detected and the comparison means determines that, the current supply stopping means stops the current supply to the light receiving elements of the light receiving element group, thereby destroying each light receiving element due to overcurrent exceeding the absolute rated current. Such a situation can be prevented in advance. In addition, since the ambient light detection element is provided separately from the light receiving element for touch detection, the ambient light detection element detects the intensity of the ambient light even after the current supply to the light receiving element is stopped. When the voltage becomes weak, the current supply of the light receiving element can be quickly restored and the subsequent operation can be immediately continued.

According to the second or third aspect of the present invention, it is possible to prevent an overcurrent exceeding the absolute rating from flowing in the disturbance light detection element, and prevent the element from being destroyed.

Since the current flowing through the light receiving element differs depending on the incident direction of the ambient light, the ambient light detecting element has at least 1 on each of the two sides facing the light emitting element group as in the invention of claim 4. By arranging the light sources one by one, it is possible to detect the ambient light under the same arrangement condition of the ambient light detection elements for all the light receiving elements, and it is possible to improve the detection accuracy.

[Brief description of drawings]

FIG. 1 is a plan view showing an optical touch switch according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a part of the optical touch switch according to the embodiment of the present invention.

FIG. 3 is a circuit diagram showing a part of an optical touch switch according to an embodiment of the present invention.

FIG. 4 is a timing chart showing a potential state of each part of the optical touch switch according to the embodiment of the present invention.

FIG. 5 is a plan view showing a conventional optical touch switch.

FIG. 6 is a perspective view showing a conventional optical touch switch.

FIG. 7 is a circuit diagram showing a part of a conventional optical touch switch.

FIG. 8 is a timing chart showing a potential state of each part of the conventional optical touch switch.

FIG. 9 is a schematic diagram showing an operation of a conventional optical touch switch.

[Explanation of symbols]

 1 Operation Panel 2 Coordinate Input Surface 3 Touch Detection Light-Emitting Element 4 Touch Detection Light-Emitting Element 6 Control Unit 7 Comparison Circuit 8 Light-Reception Signal Processing Circuit 11 Ambient Light Detection Light-Reception Element 14 Second Comparison Circuit Q0 Switch Element

Claims (4)

[Claims] 1. A light emitting element group is arranged on two adjacent sides of the four vertical and horizontal sides of a coordinate input surface, and a light receiving element group is arranged on two sides facing the light emitting element group. An optical touch switch that detects an input coordinate based on an output of a light receiving element in which a light passage on the coordinate input surface is blocked, a disturbance for detecting ambient light, which is arranged in the vicinity of the light receiving element group. A light detecting element, a comparing means for comparing and judging whether or not the intensity of the ambient light detected by the ambient light detecting element is equal to or more than a predetermined reference value, and the ambient light detection based on a signal from the comparing means. An optical touch switch, comprising: current supply stopping means for stopping the current supply to the light receiving elements of the light receiving element group when the intensity of the ambient light detected by the element is equal to or greater than a predetermined reference value. . 2. The optical touch switch according to claim 1, wherein the ambient light detection element has a light receiving sensitivity set lower than that of the light receiving elements of the light receiving element group. switch. 3. The optical touch switch according to claim 1, wherein an absolute rated current of the ambient light detecting element is set to be larger than that of the light receiving elements of the light receiving element group. Touch switch. 4. The optical touch switch according to claim 1, wherein at least one disturbance light detecting element is arranged on each of two sides facing the light emitting element group. Optical touch switch.