JP3161847B2 - Optical detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

BACKGROUND ART Conventional Example A general, FIG. 7 as a device for detecting the presence or absence of an object optically
The following circuit configuration 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 via a resistor 2. The amount of received light is converted to a photocurrent I, taken out as a voltage output via a resistor 4, amplified by an amplifier, and A / D converted to detect the presence or absence of a light-blocking object between the light emitting diode 1 and the phototransistor 3. ing.

FIG. 8 shows the relationship between the amount of light P incident on the phototransistor 3 per unit time and the photocurrent I. In FIG. 8, the photocurrent I increases linearly in proportion to the increase in the amount of received light P, and after reaching a certain amount of received light Po, even if the amount of received light P further increases, the photocurrent I becomes a constant value Io. Is maintained. That is, the phototransistor 3 receives light P = P
o, an unsaturated operating region having a saturation point of the photocurrent I = Io and increasing linearly up to the saturation point is referred to as a linear region.

[0004] When disturbance light such as the sun and fluorescent light is strong,
Since the received light amount P received by the phototransistor 3 exceeds the saturated received light amount Po, the photocurrent 1 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 shielding object. Therefore, conventionally, a filter for preventing disturbance light is provided on the front surface of the phototransistor 3, and for example, only light in the near-infrared frequency band emitted from the light emitting diode 1 is selectively transmitted to prevent transmission of disturbance light. The configuration is known. According to this configuration, when there is no light shielding, only 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 amount of received light P is significantly reduced. , Only a small amount of the photocurrent I flows, and the presence or absence or position of the light-shielding object is detected based on the level difference of the photocurrent I.

Conventional example B FIG. 9 shows a schematic overall system configuration diagram of an optical detection apparatus. In FIG. 9, a light-receiving element array 6 in which a plurality of light-receiving elements are arranged is provided at a predetermined distance from a light-emitting element array 5 in which a plurality of light-emitting elements are arranged. 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 light emitting diode 1 and the phototransistor 3 forming a pair. A signal indicating the amount of received light obtained from the operable phototransistor 3 via the multiplexer 9 is input to a comparator 11 via an amplifier 10 and compared with a specific reference level. Is input to the microprocessor 7 as the presence or absence of light shielding.

FIG. 10 is a detailed circuit configuration diagram of the amplifier 10 shown in FIG. A photocurrent according to the amount of light received by 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 the configuration of a detection panel for detecting the position of a light-shielding object of an optical detection device in detail. In FIG. 11, m light emitting diodes 1 are arranged 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 forming a pair facing each light emitting diode 1 are arranged on a third side facing the first side and a fourth side facing the second side, respectively. For example, the positions of the light emitting diodes 1 are sequentially set as X ₀ , X ₁ ,.
Defined as _M-1, the position of each light emitting diode 1 and the second side as Y axis Y _0, Y _1, ..., constitute a position detecting plane defined as Y _N-1. When the object 15 comes into contact with the 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.

Conventionally, in order to detect the element coordinate position of a light-shielding object, for example, a microprocessor 7 shown in FIG. 9 operates a light-emitting element drive circuit 8 and a multiplexer 9 so that a predetermined light-emitting time t at a predetermined time interval T. The light emitting diode 1 and the phototransistor 3 forming a pair therewith are sequentially driven. That is, in FIG. 11, X ₀ ,.
_The light emitting diodes 1 at each position of _M-1 , Y ₀ ,..., Y _N- 1
Are sequentially scanned for a light emission time t at a time interval T. Further, there is provided a X ₀ to Y _N-1 of the scan pause time interval TS is not performed scan to scan of each light-emitting diode 1 to start the next scanned completed is in position. The time interval T, the light emission time t, and the scanning pause time interval TS are time resolution elements for determining the time accuracy of light-shielded object detection, that is, the time resolution. Since these elements are conventionally fixed, the time resolution is It is kept constant.

[0009]

Problem A As shown in the conventional example A, the phototransistor 3 has a light receiving amount-
Since it has photocurrent characteristics, of the amount of light P received by the phototransistor 3, if the amount of light A emitted from the light emitting diode 1 is P1 and the amount of disturbance light B is P2, P = P1 + P2> When Po is reached, the photocurrent is distorted, and P = P2 with light shielding and P = P1 + without light shielding.
There is a problem that P2 cannot be distinguished and a malfunction occurs.
On the other hand, when a filter that selects and transmits only light in a narrow frequency range to prevent disturbance light (ambient light) as in the related art is used, there is a disadvantage that the price of the filter is increased.

It is an object of the present invention to provide an inexpensive and novel optical detecting device by utilizing a linear region of a light receiving amount-photocurrent characteristic of a light receiving element. Problem B Normally, when an optical element of a light-emitting element and a light-receiving element is manufactured, a plurality of optical elements are manufactured in a manufacturing process for each group (lot). Therefore, a relatively small variation in the characteristics of the individual optical elements in the same lot and a relatively large variation in the characteristics of the optical elements between different lots occur. Since the amplification factor of the amplifier 10 is fixed as shown in the conventional example B, if the photocurrent output from the light receiving elements arranged in the light receiving element array 6 fluctuates greatly due to the variation of the light emitting elements and the light receiving elements, the amplifier 10 There is a problem that the reference value does not reach the bell and the comparator 11 erroneously detects that the light output is present even though the output of No. 10 is not light-shielded. Since the variation of 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 element. However, since the variation of optical elements is different between different lots, For example, although the optical detection device normally operates with an optical element of a certain lot, if the optical element of a different lot is used, there is a problem that the detection operation becomes impossible at the time of incorporating the optical element.

An object of the present invention is to provide an optical detection device capable of compensating for variations in the characteristics of optical elements between different lots. Problem C In the conventional example C, when the light-shielding object is detected irregularly, it is appropriate to keep the time resolution element constant in order to secure the time resolution corresponding 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 detections 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 detections occurs irregularly at relatively long intervals. Therefore, in the optical detection device, since a series of light-shielding detections occurs during a short time during the entire operation time of the device, it is necessary to set a high-precision time resolution in accordance with a series of light-shielding detection operation periods. , With a fixed time resolution element. For this reason, since the light-emitting diode 1 emits light by scanning the device in the same manner as in the case where there is no light-shielding detection, there is a disadvantage that power consumption is wasted and the life of the device and the element is shortened. there were.

[0012]

[Means for Solving the Problems]

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

[0014]

[Action]

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 judging the presence or absence of light shielding, it is possible to cope with the variation of the optical element between lots.

[0016]

Embodiment A FIG. 1 is a principle diagram of the present invention for solving a problem A for processing a photocurrent output from a light receiving element in a linear region in a light quantity-photocurrent characteristic of FIG. ing. In FIG. 1, elements corresponding to those in FIG. 7 are denoted by the same reference numerals. P = P1 + P2, where P1 is the amount of light A received from the light-emitting diode 1 and P2 is the amount of light received from the disturbance light B in the amount P of light received by the phototransistor 3. Received light amount P
Exceeds the saturated received light amount Po shown in FIG. 8, the photocurrent I is distorted, and the operation in the linear region becomes impossible.
Must be set so that P ≦ Po. Therefore, as shown in FIG. 1, a light amount reducing member 20 having a transmittance α is provided on the front surface of the phototransistor 3. The light amount reducing member 20 reduces the light transmitted substantially irrespective of the type of the disturbance light B and the light A, that is, the frequency.
(NewtraI Density) filter may be used. The light amount reducing member 20 may be any material that can reduce the amount of transmitted light irrespective 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 amount P
The maximum received light amount P can be suppressed below o. In other words, the maximum amount of light received P that can be properly operated in the phototransistor 3 is equal to the saturated amount of received light Po in the related art, but is substantially equal to Po by providing the light amount reducing member 20.
However, the apparent value increases to Po / α. That is, the intensity of light incident on the light amount reducing member 20 up to Po / α is allowed. As described above, by providing the light amount reducing member 20, the light reception amount P of the phototransistor 3 always falls within the linear region of FIG. 8, and the photocurrent I proportional to the light reception amount P is, for example, the amplifier 1 shown in FIG.
The output 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 specific mounting structure in which the light amount 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
An ND filter 22 having a generally U-shaped cross section is formed on the inner surface of the front end of the front panel 21.
Is screwed. The ND filter 22 corresponds to the light amount reducing member 20 in FIG. 1, and reduces the amount of light going to the phototransistor 3 at a constant transmittance and almost independently of the frequency. The phototransistor 3 is mounted on the base 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 with a double-sided adhesive tape. The substrate 23 is attached to the ND filter 22 by screws 25 passing through 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.
2, the dustproof structure is hermetically sealed, so that dust can be prevented 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 attaching the light amount reducing member 20 to the phototransistor 3 may be any structure that reduces the amount of light P received by the phototransistor 3, and is not particularly required to be dustproof.

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. FIG. 3 differs from FIG. 10 in that a variable resistor 26 is used instead of the resistor 12. Since the gain of the amplifier 10 is determined by the value of the variable resistor 26 and the value of the capacitor 13, the gain can be changed by changing the value of the variable resistor 26.
As shown in FIG. 9, the optical elements of the light emitting diode 1 and the phototransistor 3 arranged in the light emitting element array 5 and the light receiving element array 6 vary greatly from one production lot to another. 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 shading.
When the light exceeds the reference level and the light is shielded, the light level is equal to or lower than the reference level. As a result, it is easy to determine whether or not the light is shielded.

FIG. 4 shows another embodiment of the present invention for solving the problem B. In the embodiment of FIG. 4, a variable amplifier 27 is newly added to the output of the conventional amplifier 10 of FIG. The variable amplifier 27 includes an operational amplifier 28, a feedback resistor 29, and a bias resistor 30. The variable amplifier 27 is made variable by making the feedback resistor 29 variable.
Is changing the amplification factor. 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 for solving the problem C. In a system configured similarly to the optical detection apparatus in FIG. 9, the microprocessor 7 will be described in detail according to the present invention. FIG. In FIG. 5, a detection signal indicating the presence or absence of light shielding from the comparator 11 is given to the control circuit 31. The microprocessor 7 has a clock circuit 3 in addition to the control circuit 31.
2, a counter 33, a ROM 34, and the like. The clock circuit 32 measures the time and outputs a time signal to the control circuit 31 and the counter 33. The counter 33 includes a light emitting time counter 33A and a scanning interval counter 33B for defining a scanning interval between one light emitting diode 1 and the next light emitting diode 1. The ROM 34 stores a scanning program required for scanning. The control circuit 31 reads out a scanning program from 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 flowchart showing the scanning operation of FIG. In FIG. 6A, the next scanning operation is repeated during the power-on period. That is, in step S1, the control circuit 31 makes the emission time counter 33A and the scanning interval counter 3 according to the scanning program of the ROM 34.
A scanning signal for scanning the light emitting diode 1 and the phototransistor 3 is sequentially output at a light emitting time t and a time interval T output from the light emitting diode 3B. When 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 outputting the scanning signal for the scanning pause time interval TS. This time is measured based on a clock signal sent from the clock circuit 32. Next, the process proceeds to step S3, where 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 a state of high time resolution in the light-shielded state, and the process returns to step S1. After the scan pause time interval TS has elapsed, a 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 where there is no light shielding and the 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 lapse of the pause time. The next scan starts.

As described above, when there is light shielding, step S1, step S2, and step S3 are sequentially repeated. As a result, the scan is paused for the scan pause time interval TS,
The next scan will be started. On the other hand, if there is no light blocking, steps S1, S2, S3, and S4 are sequentially repeated. As a result, the scan is paused for a time (TS + TA) obtained by adding the scan pause time interval TS and the scan pause addition time TA.
The next scan will be started. Therefore, when there is no light blocking, one full scanning period including the pause period is lengthened by the scan pause addition time TA, and the operation is performed with low precision time resolution. On the other hand, when there is light shielding, the scanning pause addition time TA is excluded, so that the entire scanning period is shortened, and the operation is performed with high precision time resolution.

FIG. 6B is a flowchart showing the operation of the control circuit 31 for setting the pause time addition flag F which is reset in response to a light-shielded detection signal. In FIG. 6B, in step S11, the control circuit 31 measures the time after receiving the non-light-shielded signal, and determines whether or not the non-light-shielded time has reached a predetermined time. If the fixed time has not been reached, that is, if a light-shielded detection signal is received during the fixed time, the operation with a high precision time resolution is continued without setting the pause time addition flag F. If it is determined that the light shielding has been stopped after the predetermined time has elapsed, the process proceeds to step S12, and the control circuit 31 sets the pause time addition flag F so that the operation can be performed with a low precision time resolution from the next scan. In step S11, a certain period of time is measured. However, the number of scans receiving the signal without light shielding may be counted by a counter to determine whether the count has reached the certain number.

In the embodiment C, if the light-shielding object is not detected during the predetermined time or the predetermined number of scans, the scanning pause period from the end of the scanning to the start of the next scanning is increased by a certain time. And the consumption of light emission power can be suppressed. Further, since the scanning pause period increases, the scanning of the apparatus stops during the increase period, and the life of the apparatus can be extended. In addition, when a light-shielding object is present, the light-shielding object operates with a normal high-precision time resolution, so that the position detection accuracy of the light-shielding object is maintained as before.

[0026]

【The invention's effect】

Effect B In the present invention, since the amplification factor of the amplification means for amplifying the photocurrent output from the light receiving element is made variable, the large variation of the optical element between manufacturing lots is adjusted to adjust the amplification rate of the amplification means. Can be dealt with. Therefore, when the optical detection device is adjusted to the amplification factor according to the variation of the optical element of each production lot at the time of shipment, it is possible to prevent the device from malfunctioning. Further, if this variable amplifier is provided on the detection panel side and is configured separately from the controller for processing the detection signal, the controller can be made versatile by replacing the detection panel.

[Brief description of the 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 the means for reducing the amount of received light in FIG.

FIG. 3 is a diagram showing an embodiment of a variable amplification factor configuration according to 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 message.

FIG. 6 is a flowchart illustrating the operation of the circuit in FIG. 5;

FIG. 7 is a diagram illustrating a light emission and light reception unit of the optical detection device.

FIG. 8 is a graph showing the relationship between the amount of received light and the photocurrent of a phototransistor.

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

FIG. 10 is a detailed circuit configuration diagram of the amplifier in FIG. 9;

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light emitting diode 3 phototransistor 5 light emitting element array 6 light receiving element array 7 microprocessor 8 light emitting element drive circuit 9 multiplexer 10 amplifier 20 light quantity reducing member 21 front panel 22 ND filter 23 substrate 24 packing 25 bis 26 variable resistance 27 variable amplifier 29 feedback Resistance 31 Control circuit 32 Timing circuit 33 Power counter

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yuichi Ise 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (56) References JP-A-63-12986 (JP, A) JP-A-63 289 478 (JP, A) Japanese Utility Model 62-44205 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01V 8/12 G01V 8/20

Claims (1)

(57) [Claims] 1. An optical detector for arranging a plurality of light-emitting elements and a light-receiving element at a predetermined distance from each other, and detecting the position or presence or absence of an object that blocks light emitted from the light-emitting element toward the light-receiving element. Equipment that is manufactured from the same lot
An optical detection device comprising: a plurality of light-emitting elements and a plurality of light-receiving elements; and an amplification unit that amplifies a light detection analog signal output from the plurality of light-receiving elements.