JPH06186350A - Optical detector - Google Patents

Abstract

PURPOSE:To prevent erroneous function due to the effect of ambient light in an optical detector wherein at least a pair of light emitting element and a light receiving element are disposed while being spaced apart by a predetermined distance and the position or the presence of an object, which blocks the light emitted from the light emitting element toward the light receiving element, is detected. CONSTITUTION:The optical detector comprises means 20 for decreasing the quantity of light emitted A from a light emitting means 1 and the ambient light B incident on a light receiving element 3 and the quantity of light transmitted through the means 20 is limited, at all times, within the linear operating region of quantity of received light-photocurrent characteristics. This constitution amplifies the photocurrent outputted from the light emitting element 3 with no distortion and prevents erroneous detection of the presence of blockage of optical path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical detecting device for optically detecting the presence or the position of an object.

[0002]

2. Description of the Related Art Conventional Example A Generally, FIG. 7 shows a device for optically detecting the presence or absence of an object.
The circuit configuration shown in is known. In this circuit, a phototransistor 3 receives light A emitted when a predetermined voltage is applied to the anode of a light emitting diode 1 whose cathode is grounded through a resistor 2. The amount of received light is converted into a photocurrent I, extracted as a voltage output via the resistor 4, amplified by an amplifier, and A / D converted to detect the presence or absence of a light shielding object between the light emitting diode 1 and the phototransistor 3. ing.

The relationship between the amount of light received P incident on the phototransistor 3 per unit time and the photocurrent I is shown in FIG. In FIG. 8, the photocurrent I linearly increases in proportion to the increase in the received light amount P, and after reaching the constant received light amount Po, the photocurrent I remains the constant value Io even if the received light amount P further increases. Maintained at. That is, the phototransistor 3 receives the amount of light received P = P
o, a saturation point of the photocurrent I = Io, and an operating region of the unsaturated that linearly increases until reaching the saturation point is called a linear region.

When the ambient light such as the sun or fluorescent light is strong,
Since the received light amount P received by the phototransistor 3 exceeds the saturated received light amount Po, the photocurrent I becomes a constant value Io regardless of the blinking of the light emitting diode 1, and it becomes impossible to detect the presence or absence of a light shield. Therefore, conventionally, a filter for preventing disturbance light is provided on the front surface of the phototransistor 3, and for example, only the light in the near-infrared frequency band emitted from the light emitting diode 1 is selectively transmitted to prevent the transmission of disturbance light. It has been known. According to this configuration, when there is no light shielding, only the light from the light emitting diode 1 is received by the phototransistor 3 and a sufficient photocurrent I is obtained. On the other hand, when there is light shielding, the received light amount P is significantly reduced. Since only a small photocurrent I flows from, the presence or the position of the light-shielding object is detected by the level difference of the photocurrent I.

Conventional Example B FIG. 9 shows a schematic overall system configuration of an optical detection device. In FIG. 9, a light receiving element array 6 in which a plurality of light receiving elements are arranged at a predetermined distance from a light emitting element array 5 in which a plurality of light emitting elements are arranged is provided, and the light emitting diode 1 as a light emitting element and a light emitting diode 1 are respectively provided therein. Phototransistors 3 as a pair of light receiving elements are arranged.
The microprocessor 7 sequentially scans the light emitting element drive circuit 8 and the multiplexer 9 to enable the pair of the light emitting diode 1 and the phototransistor 3. A signal representing the amount of received light, which is obtained from the phototransistor 3 in the operable state via the multiplexer 9, is input to the comparator 11 via the amplifier 10 and compared with a specific reference level, and the comparison output is the object. The presence / absence of light shielding is input to the microprocessor 7.

FIG. 10 is a detailed circuit diagram of the amplifier 10 shown in FIG. A photocurrent corresponding to the amount of received light that has entered the phototransistor 3 flows through the resistor 4, and the voltage generated by the resistor 4 is applied to the amplifier 10. The amplifier 10 operates as an integrating amplifier by the input resistor 12, the capacitor 13 and the operational amplifier 14. The voltage applied to the amplifier 10 is integrated to produce a voltage at the output of the amplifier 10 proportional to the integrated voltage determined by the product of the value of the resistor 12 and the value of the capacitor 13. Since the values of the resistor 12 and the capacitor 13 are fixed, the amplification factor of the amplifier 10 is also fixed.

Conventional Example C FIG. 11 shows in detail the construction of a detection panel for detecting the position of a light-shielding object of an optical detection device. In FIG. 11, m light emitting diodes 1 are provided on the first side of the detection panel.
Are arranged at equal intervals, and n light emitting diodes 1 are arranged at equal intervals on the second side adjacent to the first side. Phototransistors 3 are arranged on the third side facing the first side and the fourth side facing the second side so as to face each light emitting diode 1 and form a pair. For example, the position of each light emitting diode 1 is sequentially set to X ₀ , X ₁ , ..., X with the first side as the X axis.
The position of each light emitting diode ₁ is defined as Y ₀ , Y ₁ , ..., Y _N-1 with the second side as the Y-axis to form a position detection surface. When the object 15 comes into contact with this position detection surface, the light from the corresponding light emitting diode 1 is blocked by the object 15 and the element coordinate position (X _I , Y _J ) of the object 15 is detected.

In order to detect the element coordinate position of a light-shielded object, conventionally, for example, a microprocessor 7 shown in FIG. 9 operates a light emitting element drive circuit 8 and a multiplexer 9 to set a predetermined light emission time t at regular time intervals T. The light emitting diode 1 and the phototransistor 3 paired with the light emitting diode 1 are sequentially driven. That is, in FIG. 11, X ₀ , ..., X _M
The light emitting diodes 1 located at positions _-1 , Y ₀ , ..., Y _N- 1 are sequentially scanned at a time interval T for a light emission time t.
To be done. Further, there is provided a scan pause time interval TS in which scanning is not performed until the scanning of each light emitting diode 1 at the positions of X _{0 to} Y _N-1 is completed and the next scanning is started. The time interval T, the light emission time t, and the scanning rest time interval T
S is a time resolution element that determines the time accuracy of the light-shielded object detection, that is, the time resolution. Since these elements are conventionally fixed, the time resolution is kept constant.

[0009]

Problem A : As shown in the conventional example A, the phototransistor 3 has a received light amount −
Since the phototransistor 3 has a photocurrent characteristic, P = P1 + P2> where P1 is the received light amount of the light A emitted from the light emitting diode 1 and P2 is the received light amount of the ambient light B among the received light amount P received by the phototransistor 3. At Po, the photocurrent will be distorted, and there will be P = P2 with light shielding and P = P1 + without light shielding.
In the case of P2, there is a problem that the malfunction cannot be made because the distinction cannot be made.
On the other hand, when a filter that selects and transmits only light in a narrow frequency range for preventing ambient light (ambient light) as in the related art is used, the cost of the filter increases.

An object of the present invention is to provide an inexpensive and novel optical detection device by utilizing the linear region of the amount of received light-photocurrent characteristic of the light receiving element.

Problem B Normally, when manufacturing optical elements such as a light emitting element and a light receiving element, a plurality of optical elements are put together in a manufacturing process for each group (lot). Therefore, there are relatively small variations in the characteristics of the individual optical elements in the same lot, and relatively large variations in the characteristics of the optical elements between different lots. As shown in the conventional example B, since the amplification factor of the amplifier 10 is fixed, if the photocurrent output from the light receiving elements arranged in the light receiving element array 6 fluctuates greatly due to variations in the light emitting elements and the light receiving elements, the amplifier There is a problem that the comparator 11 does not reach the reference value level and is erroneously detected by the comparator 11 that there is light shielding although the output of 10 does not have light shielding. Since the variation of the optical elements in the same lot is relatively small, it can be dealt with by performing compensation processing such as changing the individual drive amount of the light emitting elements. However, there is a problem in that the optical detection device normally operates with an optical element of a certain lot, but when the optical element of a different lot is used, the detection operation cannot be performed when the optical element is incorporated.

An object of the present invention is to provide an optical detection device capable of compensating for variations in characteristics of optical elements between different lots.

Problem C In the conventional example C, when the light-shielding object is irregularly detected, it is appropriate to make the time resolution element constant in order to secure the time resolution matched to the required detection accuracy. . However, when the optical detection device is used as a man-machine interface, there is a certain pattern for detecting a light-shielding object. That is, when a light-shielding object is first detected, there is a series of light-shielding detection in which detection is performed again in a relatively short time and the detection is repeated a plurality of times. This series of light-shielding detection occurs irregularly at relatively long intervals. Therefore, in the optical detection device, a series of light-shielding detection occurs for a short time during the entire operation time of the device, and therefore, when a highly accurate time resolution is set in accordance with the series of light-shielding detection operation periods. , Scanning is performed with a fixed time resolution element. For this reason, even though there is no light-shielding detection, the device is scanned to cause the light emitting diode 1 to emit light in the same manner as when there is light-shielding detection. there were.

An object of the present invention is to provide an optical detection device with low power consumption and long life.

[0015]

The invention for solving the problem A is provided with a light quantity reducing means for decreasing the quantity of light received by the light receiving element irrespective of the frequency of the incident light, and the quantity of light received is received by the light receiving element. This is achieved by keeping the operating range in the linear region of the quantity-photocurrent characteristic.

The invention for solving the problem B is achieved by making the amplification factor of the amplifying means for amplifying the photodetection analog signal outputted from the light receiving element variable.

The invention for solving the problem C is to measure the scanning time or the number of times of scanning of the light emitting element and the light receiving element, a detecting means for detecting the presence or absence of an object that blocks the light, and a predetermined time by the detecting means. Alternatively, when a light-shielding object is not detected within a predetermined number of scans, a means for increasing the scan pause period from the end of scanning to the start of the next scan for a fixed time, and the increased scan pause period when the light-shielding object is detected. And a means for returning to the original scan idle period.

[0018]

With the provision of the light amount reducing means, the total amount of the ambient light incident on the light receiving element and the light output of the light emitting element is
Since the linear region of the light receiving-photocurrent characteristics of the light receiving element is reduced irrespective of the frequency, the linear operation of the light receiving amount-photocurrent is always performed, and erroneous detection does not occur.

Since the amplification factor of the amplifying means can be set so that the optical signal output from the light receiving element can be amplified to a level suitable for determining the presence or absence of light shielding, it is possible to cope with variations in the optical element between lots.

By increasing the scanning pause period from the end of a scan in which the presence or absence of a light-shielded object is not detected to the start of the next scan for a certain period of time, the time resolution when no object is detected is reduced,
Thus, the life of the device can be extended and the power consumption can be reduced.

[0021]

EXAMPLE A FIG. 1 shows a principle diagram of the present invention for solving the problem A for processing the photocurrent output from the light receiving element in the linear region in the light amount-photocurrent characteristic of FIG. There is. In FIG. 1, elements corresponding to those in FIG. 7 are designated by the same reference numerals. Of the amount P of light received by the phototransistor 3, if the amount of light A received from the light emitting diode 1 is P1 and the amount of light received by the ambient light B is P2, then P = P1 + P2. Received light amount P
Exceeds the saturated received light amount Po shown in FIG. 8, the photocurrent I is distorted and operation in the linear region becomes impossible.
Must be set so that P ≦ Po. Therefore, as shown in FIG. 1, the light amount reducing member 20 having the transmittance α is provided on the front surface of the phototransistor 3. The light amount reducing member 20 reduces the transmitted light regardless of the types of the ambient light B and the light A, that is, the frequency, and is, for example, ND.
You may use a (Newr Density) filter. The light amount reducing member 20 may be any material that can reduce the amount of transmitted light regardless of the frequency, and is not limited to a specific material.

Since the amount of light transmitted through the light amount reducing member 20 and received by the phototransistor 3 is reduced to αP, if the transmittance α of the light amount reducing member 20 is properly selected, the saturated light receiving amount P is obtained.
The maximum received light amount P can be suppressed to be equal to or less than o. In other words, the maximum amount of received light P that can be properly operated in the phototransistor 3 has been the same as the saturated amount of received light Po in the related art, but since the light amount reducing member 20 is provided, it is substantially the same.
However, apparently it will increase to Po / α. That is, the intensity of light incident on the light amount reducing member 20 is allowed up to Po / α. As described above, by including the light amount reducing member 20, the light receiving amount P of the phototransistor 3 always falls within the linear region of FIG. 8, and the photocurrent I proportional to the light receiving amount P is the amplifier 1 as shown in FIG. 9, for example.
The signal is amplified by 0, and its output is compared with a reference level in a comparator 11 to be used for detecting the presence or absence or the position of a light-shielding object.

FIG. 2 shows an embodiment of a concrete mounting structure in which the light quantity reducing member 20 is mounted on the phototransistor 3. In FIG. 2, a front panel 21 is provided around the detection surface for fixing the light emitting diode 1 and the phototransistor 3. This front panel 2
1 is usually made of a non-translucent material, and an ND filter 22 having a U-shaped cross section is formed on the inner surface of the front end of the front panel 21.
Is screwed on. This ND filter 22 corresponds to the light amount reducing member 20 of FIG. 1, and reduces the light amount toward the phototransistor 3 with a constant transmittance and substantially regardless of the frequency. The phototransistor 3 is attached to the substrate 23, and the substrate 23 is provided with required wiring. Further, a packing 24 is interposed between the substrate 23 and the ND filter 22 and temporarily fixed by a double-sided adhesive tape, and the substrate 23 is attached to the ND filter 22 by a screw 25 penetrating the substrate 23 and the packing 24. . In the embodiment of FIG. 2, in addition to performing the function of reducing the amount of light, the phototransistor 3 includes a substrate 23 and an ND filter 2.
Since it is formed in an airtight and dustproof structure by 2, it is possible to prevent dust from adhering to the back surface of the ND filter 22 and the light receiving surface of the phototransistor 3. When replacing the phototransistor 3, the phototransistor 3 can be removed together with the substrate 23 by removing the screw 25. The structure for mounting the light amount reducing member 20 on the phototransistor 3 may be any structure as long as it reduces the light receiving amount P of the phototransistor 3, and a dustproof structure is not particularly required.

Embodiment B FIG. 3 shows an embodiment of the present invention for solving the problem B. FIG. 3 corresponds to FIG. 10, and the same components as those in FIG. 10 are denoted by the same reference numerals. 3 is different from FIG. 10 in that a variable resistor 26 is used instead of the resistor 12. Since the amplification factor of the amplifier 10 is determined by the product of the value of the variable resistor 26 and the value of the capacitor 13, the amplification factor can be changed by changing the value of the variable resistor 26. As shown in FIG. 9, since the optical elements of the light emitting diodes 1 and the phototransistors 3 arranged in the light emitting element array 5 and the light receiving element array 6 largely vary depending on the manufacturing lot, the characteristics of the manufacturing lot to which the arranged optical elements belong. The variable resistor 26 is adjusted according to. Then, the photocurrent from the phototransistor 3 is amplified to an appropriate level by the amplifier 10, and the amplified output is output from the comparator 11 when there is no light shielding.
If the light level exceeds the reference level and the light level is lower than the reference level, the presence or absence of light blocking can be easily determined.

FIG. 4 shows another embodiment of the present invention for solving the problem B. In the embodiment shown in FIG. 4, a variable amplifier 27 is newly added to the output of the conventional amplifier 10 shown in FIG. The variable amplifier 27 is composed of an operational amplifier 28, a feedback resistor 29, and a bias resistor 30. By making the feedback resistor 29 variable, the variable amplifier 27 is provided.
Is changing the amplification factor of. The operation of the embodiment of FIG. 4 is exactly the same as that of the embodiment of FIG.

Embodiment C FIG. 5 shows an embodiment of the present invention for solving the problem C,
FIG. 10 is a diagram illustrating in detail the microprocessor 7 in a system configured similarly to the optical detection device in FIG. 9 according to the present invention. In FIG. 5, the detection signal indicating the presence or absence of light shielding from the comparator 11 is given to the control circuit 31. In addition to the control circuit 31, the microprocessor 7 is provided with a clock circuit 32, a counter 33, a ROM 34, and the like. The clock circuit 32 clocks time and outputs a time signal to the control circuit 31 and the counter 33. The counter 33 includes a light emission time counter 33A and a scanning interval counter 33B that defines a scanning interval from one light emitting diode 1 to the next light emitting diode 1. Also, ROM3
In 4, a scanning program necessary for scanning is stored.
The control circuit 31 reads the scanning program of the ROM 34 and outputs a scanning signal to the light emitting element drive circuit 8 and the multiplexer 9 (FIG. 9) according to the program. The control circuit 31 is provided with a storage area for storing the scan pause time interval TS and the scan pause addition time TA, and a flag area for storing the pause time addition flag F. The control circuit 31 resets the pause time addition flag F each time a detection signal indicating that light is shielded is input.

FIG. 6 is a flow chart showing the scanning operation of FIG.
It is In FIG. 6A, the next scanning operation is repeated during the power-on period. That is, in step S1, the control circuit 31 follows the scanning program of the ROM 34 and emits the light emission time counter 33A and the scanning interval counter 3.
A scanning signal for scanning the light emitting diode 1 and the phototransistor 3 is sequentially output at the light emission time t and the time interval T output from 3B. When the scanning is performed once, that is, when all the optical elements are scanned once, the process proceeds to step S2. In step S2, the control circuit 31 stops the output of the scanning signal for the scanning pause time interval TS. This time is timed based on the time signal sent from the time counting circuit 32. Next, in step S3, the control circuit 31 determines whether or not the pause time addition flag F is set.
If the pause time addition flag F is not set, it is determined that scanning is performed in the light-shielded state and the time resolution is high, and the process returns to step S1. After the scan pause time interval TS has elapsed, the scan signal is output. Then, the next scan is started.
If it is determined in step S3 that the pause time addition flag F is set, it is determined that scanning is performed in a state in which light is not shielded and time resolution is low, and the process proceeds to step S4. In step S4, the control circuit 31 reads the scan pause addition time TA, pauses the scan for the scan pause addition time TA in addition to the scan pause time interval TS, and returns to step S1 after the passage of the pause time. The next scan is started.

As described above, when light is shielded, step S1, step S2, and step S3 are sequentially repeated, and as a result, scanning is paused for the scan pause time interval TS,
The next scan will be started. On the other hand, when there is no light blocking, steps S1, S2, S3, and S4 are sequentially repeated, and as a result, scanning is paused for a time (TS + TA) that is the sum of the scan pause time interval TS and the scan pause addition time TA, and then
The next scan will be started. Therefore, when there is no light blocking, one scanning period including the pause period becomes longer by the scan pause addition time TA, and the operation is performed with low accuracy time resolution. On the other hand, when the light is shielded, the scanning pause addition time TA is removed, so that the entire scanning period is shortened and the operation is performed with a highly accurate time resolution.

FIG. 6B is a flow chart showing the operation of setting the pause time addition flag F which is reset in response to the detection signal indicating the presence of light shielding in the control circuit 31. In FIG. 6B, in step S11, the control circuit 31 measures the time from the reception of the non-light-shielding signal, and determines whether the non-light-shielding time has reached a certain time. When the fixed time has not been reached, that is, when the detection signal with light shielding is received during the fixed time, the operation with high precision time resolution is continued without setting the pause time addition flag F. If it is determined that the light has been shielded for a certain period of time, the process proceeds to step S12, and the control circuit 31 sets the pause time addition flag F so that it can operate with low time resolution from the next scan. In addition, in step S11, although the configuration is such that a certain period of time is clocked, the number of times of scanning receiving a signal without light shielding may be counted by a counter to determine whether or not the certain number has been reached.

[0030]

[Effect] Effect A According to the present invention, the light receiving element receives light regardless of the frequencies of light emitted from the light emitting element and ambient light (ambient light) so that the light receiving quantity of the light receiving element falls within the operating range of the linear region. Since the light quantity reducing means for reducing the quantity is provided, the operating range of the linear region of the light receiving element can be freely selected by selecting the transmittance of the light quantity reducing means, and even when used in a place where the ambient light is strong. It can be adjusted so that the amount of received light does not reach the saturation region. Therefore, like a conventional device,
It is possible to prevent the inconvenience that the device malfunctions even when used in a place where the ambient light is strong. Further, the light quantity reducing means is cheaper than the case of using a conventional filter for preventing disturbance light that selects only a specific frequency, and malfunctions can be avoided by a new method of reducing the light quantity regardless of the frequency. is there.

Effect B According to the present invention, the amplification factor of the amplifying means for amplifying the photocurrent output from the light receiving element is made variable, so that the large variation of the optical element occurring between manufacturing lots is adjusted. Can be dealt with. Therefore, if the amplification factor is adjusted at the time of shipment of the optical detection device in accordance with the variation of the optical elements of each manufacturing lot, it is possible to prevent the inconvenience that the device malfunctions. Further, if this variable amplifier is provided on the detection panel side and is configured separately from the controller that processes the detection signal, the controller can be made versatile by exchanging the detection panel.

Effect C According to the present invention, when a light-shielding object is not detected within a predetermined time or a predetermined number of scans, the scanning pause period from the end of scanning to the start of the next scanning is increased by a fixed time. It is possible to reduce the power consumption by reducing the resolution. Further, since the scanning pause period increases, the scanning of the device is stopped during the increased period, so that the life of the device can be extended. Moreover, when there is a light-shielding object, the operation is performed with the usual high-precision time resolution, so that the position detection accuracy of the light-shielding object is maintained as usual.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of reducing the amount of received light according to the present invention.

FIG. 2 is a diagram showing a specific mounting structure of means for reducing the amount of received light in FIG.

FIG. 3 is a diagram showing an embodiment of a variable amplification factor configuration of the present invention.

FIG. 4 is a diagram showing another embodiment of the variable amplification factor configuration of the present invention.

FIG. 5 is a diagram showing a schematic main circuit configuration for outputting a scanning signal according to the present invention.

6 is a flowchart illustrating the operation of the circuit of FIG.

FIG. 7 is a diagram illustrating a light emitting and light receiving section of the optical detection device.

FIG. 8 is a diagram showing the amount of received light versus photocurrent of a phototransistor.

FIG. 9 is a schematic overall system configuration diagram of an optical detection device.

10 is a detailed circuit configuration diagram of the amplifier of FIG.

FIG. 11 is a diagram illustrating a configuration of a detection panel of the optical detection device.

[Explanation of symbols]

 1 light emitting diode 3 phototransistor 5 light emitting element array 6 light receiving element array 7 microprocessor 8 light emitting element driving circuit 9 multiplexer 10 amplifier 20 light quantity reducing member 21 front panel 22 ND filter 23 substrate 24 packing 25 screw 26 variable resistance 27 variable amplifier 29 feedback Resistance 31 Control circuit 32 Clock circuit 33 Counter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuichi Ise 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd.

Claims (3)

[Claims] 1. An optical device for arranging at least a pair of a light emitting element and a light receiving element with a predetermined distance therebetween, and detecting the position or presence or absence of an object that shields the light emitted from the light emitting element toward the light receiving element. In the detection device, a light amount reducing means for reducing the amount of light received incident on the light receiving element regardless of the frequency of the incident light is provided, and the amount of light received is an operating range of a linear region of the amount of light received by the light receiving element-photocurrent characteristic. Optical detection device characterized by being suppressed to. 2. An optical system in which at least a pair of a light emitting element and a light receiving element are arranged at a predetermined distance from each other and which detects the position or presence or absence of an object that shields the light emitted from the light emitting element toward the light receiving element. In the detection device, the amplification factor of the amplification means for amplifying the photodetection analog signal output from the light receiving element is made variable, and the optical detection device. 3. An optical system for arranging at least a pair of a light emitting element and a light receiving element at a predetermined distance from each other, and detecting the position or presence or absence of an object that shields the light emitted from the light emitting element toward the light receiving element. In the detection device, a time measuring means for measuring the scanning time or the number of times of scanning of the light emitting element and the light receiving element, a detecting means for detecting the presence or absence of an object that blocks the light, and a predetermined time or a predetermined number of scanning times by the detecting means. When a light-shielded object is not detected, means for increasing the scanning pause period from the end of scanning to the start of the next scanning by a certain period,
An optical detection device comprising means for returning the increased scanning pause period to the original scanning pause period when the light shield is detected.