JP2007036773A - Apparatus and method for detecting detection object by optical sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that much processing time is required for processing for sequentially detecting the output voltage level of a light receiving element during operation of detecting a detection object and determining reference voltage on the basis of the detected level. <P>SOLUTION: A detection object detecting apparatus which includes an optical sensor having a light emitting element and a light receiving element and has the optical sensor arranged so that light from the light emitting element up to the light receiving element passes through the position of a detection object so as to detect the existence of the detection object by an output state of the optical sensor, is provided with; a reference voltage generation part, a comparator for comparing an output from the optical sensor with reference voltage outputted from the reference voltage generation part and detecting the existence of the detection object in accordance with the compared result, and a control part for supplying a control signal for outputting the reference voltage from the reference voltage generation part; and constituted so that the control part acquires the output value of the optical sensor before detecting the detection object and determines the reference voltage for detecting the existence of the detection object on the basis of the acquired output value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for detecting the presence / absence of a detection object, and more particularly to an apparatus and a method for detecting a detection object by an optical sensor that combines a light emitting element and a light receiving element.

  Conventionally, the following techniques have been known as means for detecting an object detected by an optical sensor. First, an object to be detected is disposed at a position where light passes between a light emitting element such as a light emitting diode and a light receiving element such as a phototransistor constituting the photosensor. Then, the photocurrent output from the light receiving element is converted into a voltage output by a resistor, and the voltage level is binarized with a predetermined threshold voltage as a reference and output. Thus, based on the binarized output, it is determined whether or not the light emitted from the light emitting element such as the light emitting diode is in a light transmitting state or a light shielding state, thereby detecting the presence or absence of a detection object at that position.

  However, when the elements that are not classified and ranked according to the “radiant intensity of the light emitting element” and the “photocurrent of the light receiving element” are combined, the sensor output may vary by several tens of times depending on the combination of the elements. .

  Here, in the case of a combination of elements that increase the sensor output, the light emitted from the light emitting element passes through the detection object due to the transmittance of the detection object due to the “thickness / color / material” of the detection object. Think of a case. In this case, the voltage level of the sensor output exceeds the threshold voltage level for binarization, so that the light-shielding state cannot be detected normally and the sensor does not function normally.

  On the other hand, in the case of a combination of elements that reduce the sensor output, the sensor output voltage level may not reach the threshold voltage level for binarization even in a light-transmitting state where there is no detection object. In this case, there is a problem that the light transmission state cannot be normally detected and the sensor does not function normally.

  Further, there is a case where the high-level voltage level of the sensor output does not reach the threshold voltage level for binarization due to a decrease in sensor output due to deterioration of radiation intensity with time in the light-emitting element or a decrease in sensor output due to dust. In this case, the light transmission state cannot be normally detected, and there is a problem that the sensor does not function normally.

  As described above, the detection error caused by insufficient sensor output due to the variation of the light emitting element and the light receiving element in the optical sensor, or the false detection caused by permeation of the detected object due to the excessive sensor output, and the sensor output due to aging of the dust and the light emitting element. There was a problem of false detection caused by a drop in

  Japanese Laid-Open Patent Publication No. 7-30398 (hereinafter referred to as Patent Document 1) discloses that the presence or absence of a detection object is determined based on a comparison result between an output voltage level of a light receiving element and a reference voltage for detection by a comparison unit. . At the same time, a technique for solving the problem of false detection caused by a decrease in sensor output by changing the light emission amount of the light emitting element and adjusting the sensitivity based on the comparison result between the output level and the adjustment reference voltage is disclosed. ing.

  Japanese Patent Application Laid-Open No. 11-248854 (hereinafter referred to as Patent Document 2) obtains an average value of output voltage levels of a light receiving element over a certain period and subtracts a value that is variable according to the output voltage level from the average value. A technique used as a reference voltage for a comparator is disclosed.

Japanese Patent Application Laid-Open No. 7-30398 Japanese Patent Laid-Open No. 11-248854

  In Patent Document 1, there is a problem in that it takes time to stabilize the output voltage of the optical sensor due to a delay in the response of the optical sensor to the light emission control voltage during adjustment, resulting in a standby period. The reason is that the sensitivity is adjusted by changing the light emission amount of the light emitting element based on the comparison result between the optical sensor output level and the adjustment reference voltage during adjustment.

  In addition, in this document, when the sensor output level decreases due to deterioration over time and dirt, etc., the light emission amount of the light emitting element is increased in order to obtain an optimum sensor output voltage, but the increase in the light emission amount accelerates the deterioration of the light emitting element over time. In addition, there is a problem that it leads to an increase in power consumption.

  Further, in Patent Document 2, there is a problem such as an increase in load on a control circuit (LSI) due to a decrease in processing speed during operation and a need to perform sensor level AD conversion and digital processing. The reason is that it is necessary to sequentially detect the current output voltage level of the light receiving element when detecting an object to be detected (during operation) and to perform processing for determining a reference voltage based on the detected output voltage level.

  Accordingly, an object of the present invention is to provide a detection object detection device and a detection method using an optical sensor that solves the above-described conventional problem that it takes time until the output voltage of the optical sensor is stabilized during adjustment. Another object of the present invention is a detection object by an optical sensor that solves the problems such as sequential detection of the current output voltage level of a light receiving element during operation and speed reduction due to reference voltage determination processing, which is a conventional problem described above. It is to provide a detection device and a detection method.

  In order to solve such a problem, the detected object detection apparatus of the present invention includes an optical sensor having a light emitting element and a light receiving element, and arranges the optical sensor so that light from the light emitting element to the light receiving element passes through the position of the detected object. The detected object detection device detects the presence or absence of the detected object according to the output state of the optical sensor, and compares the reference voltage generator with the result of comparing the optical sensor output value with the reference voltage output from the reference voltage generator. A comparator for detecting the presence or absence of a detection object and a control unit for supplying a control signal for causing the reference voltage generation unit to output a reference voltage are provided. A sensor output value is acquired, and a reference voltage for detecting the presence or absence of a detection object is determined based on the optical sensor output value.

  The detection object detection device of the present invention is a device that detects the presence or absence of a detection object, preferably based on whether the optical sensor output is in a light-transmitting state or a light-shielding state, and the control unit detects the detection object as necessary. The optical sensor output value is obtained from the change in the output of the comparator when the reference voltage is changed before starting, and the reference voltage for detecting the presence or absence of the detection object is determined based on the optical sensor output value. It is characterized by.

The detected object detection apparatus of the present invention acquires the light sensor output value in the light passing state by the change in the output of the comparator when the optical sensor output is in the light passing state and the reference voltage is changed in the decreasing direction. A reference voltage for detecting the presence or absence of a detection object may be determined based on the output value.
Preferably, the detection object detection apparatus of the present invention obtains the light sensor output value in the light passing state by the change in the output of the comparator when the light output from the light sensor is in the light passing state and the reference voltage is changed in the increasing direction. You may determine the reference voltage when detecting the presence or absence of a detection object based on an optical sensor output value.

  The detection object detection apparatus of the present invention acquires the reference voltage as the light sensor output value in the lighted state when the output of the comparator is reversed or the output of the comparator is inverted by changing the reference voltage stepwise, and the light sensor output You may determine the reference voltage when detecting the presence or absence of a detection object based on a value.

  The detected object detection apparatus of the present invention changes the reference voltage stepwise by a plurality of steps and changes the output of the comparator one step at a time in the opposite direction and then reverses the output of the comparator again or The reference voltage immediately before that may be acquired as the light sensor output value in the lighted state, and the reference voltage for detecting the presence or absence of the detection object may be determined based on the light sensor output value.

  The detected object detection apparatus of the present invention may calculate a photosensor output value in a light-shielded state from a photosensor output value in a light-transmitting state and add a constant value to the output as a reference voltage.

  In the detected object detection device of the present invention, a value obtained by adding a constant value α to a value obtained by multiplying the optical sensor output value in the light-transmitting state by the transmittance of the detected object may be used as the reference voltage.

  The detected object detection apparatus of the present invention calculates a light sensor output value in a light-shielded state from a light sensor output value in a light-transmitting state, and outputs a predetermined value β (0 <β <1) as a difference between the two optical sensor outputs. A value obtained by adding the values multiplied by) may be used as the reference voltage.

  The detected object detection apparatus according to the present invention has a predetermined value β (0 <0) as a difference between a value obtained by multiplying the optical sensor output value in the light-transmitting state by the transmittance of the detected object and the light sensor output in the light-transmitting state. A value obtained by adding the values multiplied by β <1) may be used as the reference voltage.

  The detection object detection apparatus of the present invention may further include a switch for turning on and off the light emitting element, and the control unit may send a control signal for turning on and off the switching element to flow a pulsed current to the light emitting element.

  In the detection object detection apparatus of the present invention, the control unit may detect the output of the comparator in synchronization with the on / off of the light emitting element and detect the output of the comparator in synchronization with the on / off of the light emitting element.

  The control device of the present invention includes an optical sensor having a light emitting element and a light receiving element, a reference voltage generation unit, and a comparator that compares an output of the optical sensor with a reference voltage output from the reference voltage generation unit, and emits light. This is a control device that constitutes a detection object detection device that arranges an optical sensor so that light from the element to the light receiving element passes through the position of the detection object, and detects the presence or absence of the detection object according to the output state of the optical sensor, and a reference voltage Supply a control signal to output the reference voltage to the generator, acquire the optical sensor output value before detecting the detected object, if necessary, and detect the presence or absence of the detected object based on the optical sensor output value A reference voltage for determining is determined.

  The detection object detection method of the present invention is a detection object detection method for detecting the presence or absence of a detection object depending on whether a light sensor having a light-emitting element and a light-receiving element is in a light-transmitting state or a light-blocking state. A first step of acquiring an optical sensor output value before detecting the detected object, and a second step of determining a reference voltage of the optical sensor output value when detecting the presence or absence of the detected object based on the optical sensor output value; And a third step of comparing the output value of the optical sensor with a reference voltage and detecting the presence or absence of a detected object based on the comparison result.

  In the detection object detection method of the present invention, preferably, the first step acquires an optical sensor output value based on a change in the comparison result when the reference voltage is changed before detecting the detection object, if necessary. Features.

  In the detected object detection method of the present invention, the first step is to obtain the light sensor output value in the light passing state by the change in the comparison result when the light sensor output is in the light passing state and the reference voltage is changed in the decreasing direction. Also good.

  In the detected object detection method of the present invention, the first step is to obtain the light sensor output value in the light passing state by the change in the comparison result when the light sensor output is in the light passing state and the reference voltage is changed in the increasing direction. Also good.

  In the detected object detection method of the present invention, even if the first step changes the reference voltage stepwise and the comparison result is inverted or the reference voltage immediately before is obtained as the light sensor output value in the lighted state. Good.

  In the detected object detection method of the present invention, when the first step changes the reference voltage step by step in a plurality of steps and the comparison result is reversed, then the comparison result is changed step by step in the opposite direction and the comparison result is reversed again. Or you may acquire the reference voltage immediately before that as an optical sensor output value of a light state.

  In the detected object detection method of the present invention, the second step may use a value obtained by calculating a light sensor output value in a light shielding state from a light sensor output value in a light passing state and adding a constant value to the output as a reference voltage. .

  In the detected object detection method of the present invention, in the second step, a value obtained by adding a constant value α to a value obtained by multiplying the light sensor output value in the light-transmitting state by the transmittance of the detected object may be used as the reference voltage.

  In the detected object detection method of the present invention, in the second step, the light sensor output value in the light shielding state is calculated from the light sensor output value in the light passing state, and the difference between the two light sensor outputs is calculated as a predetermined value β ( A value obtained by adding a value obtained by multiplying 0 <β <1) may be used as the reference voltage.

  In the detection object detection method of the present invention, the second step is to set a difference between a value obtained by multiplying the light sensor output value in the light passing state by the transmittance of the detection object and the value and the light sensor output in the light passing state. A value obtained by adding a value obtained by multiplying the value β (0 <β <1) may be used as the reference voltage.

  In the detection object detection method of the present invention, a pulsed current may be passed through the light emitting element by turning on and off the light emitting element in the first and third steps.

  In the detection object detection method of the present invention, in the first and third steps, the comparison result between the optical sensor output value and the reference voltage may be taken in synchronization with the on / off of the light emitting element.

  The present invention has the effect of increasing the processing speed during operation because it is not necessary to sequentially detect the current sensor output level during operation to detect a detected object and to perform processing for determining a reference voltage. is doing. The reason is that the current sensor output level is acquired before the operation for detecting the detected object, and the reference voltage for detecting the presence or absence of the detected object is determined and operated based on the output value of the optical sensor. It is.

  Next, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention.

  The detected object detection apparatus using the optical sensor of the present invention includes an optical sensor 1 including a light emitting element 2 and a light receiving element 3, a sensor output voltage 11 output from the light receiving element 3, and an analog voltage level output from the DA converter 5. A threshold voltage 14 as a reference voltage is input and compared, a comparator 4 that binarizes and outputs the comparison result, and a binarized output 12 as an output of the comparator 4 is input and controlled to the DA converter 5 The LSI 6 that outputs the signal 13 and the DA converter 5 that DA-converts the control signal 13 from the LSI 6 and outputs the threshold voltage 14 to the comparator 4 are provided.

  The detected object detection apparatus using the optical sensor of the present invention includes a resistor 9 connected to the output terminal of the light receiving element 3 to convert the current output of the light receiving element 3 into a voltage output, and a resistor 8 connected to the light emitting element 2. Prepare.

  The light emitting element 2 is composed of a light emitting diode or the like, and the light receiving element 3 is composed of a phototransistor or the like.

  In the present embodiment, the optical sensor 1 is described as an example. However, the optical sensor 1 includes an infrared sensor using an infrared sensor other than visible light.

  The light emitting element 2 and the light receiving element 3 of the optical sensor 1 are arranged at a position where the light from the light emitting element 2 to the light receiving element 3 passes through the position of the detection object.

  Note that the comparator 4 including a comparator receives the threshold voltage 14 output from the DA converter 5 and uses it as a reference voltage. If the sensor output voltage 11 is larger than the threshold voltage 14, the binarized output 12 of the comparator 4 becomes 1 level, and it is determined that the light is in a light-transmitting state. The DA converter 5 that outputs a threshold voltage 14 as a reference voltage is a device that generates a reference voltage. In the case of the present embodiment in which the reference voltage is an analog signal and the output of the LSI 6 is a digital signal, the DA converter 5 is used, but this is an example.

  On the other hand, if the sensor output voltage 11 is smaller than the threshold voltage 14, the binarized output 12 of the comparator 4 becomes 0 level, and it is determined that the light is blocked. The result of the determination may be transmitted as a signal outside the detection device, or may be displayed in a form that can be perceived by humans.

  The LSI 6 serves as a control unit that controls the entire detected object detection apparatus. The LSI 6 has a function of calculating the optimum threshold voltage 14 and setting the DA converter 5 according to the current state of the optical sensor 1. Specifically, a value obtained by multiplying the sensor output voltage 11 at the time of current passage by the light transmittance of the detection object 21 (hereinafter simply referred to as transmittance) is assumed to be the sensor output voltage 11 at the time of light shielding, and this value is a constant value. A value obtained by adding α is determined and stored as the optimum threshold voltage 14.

  It can also be explained as follows. When the output voltage level of the optical sensor 1 is larger than the standard (typical value), the control signal 13 to the DA converter 5 is set so that the threshold voltage 14 is larger than the standard. When the output voltage level of the optical sensor 1 is lower than the standard, the control signal 13 to the DA converter 5 is set so that the threshold voltage 14 is lower than the standard.

  The LSI 6 includes an input unit 6a that inputs the binarized output 12 from the comparator 4, a main control unit 6b that performs overall control, and a calculation unit 6c that calculates a threshold voltage during operation in consideration of the transmittance of the detected object 21. A storage unit 6 d for storing the transmittance of the detected object and the calculated threshold voltage 14, and a DA converter control unit 6 e for generating the control signal 13 and controlling the DA converter 5.

  In the operation of acquiring the sensor output voltage 11 in the absence of the detection object 21, the main control unit 6b continues until the binarized output 12 of the comparator 4 from the input unit 6a changes from the light shielding state to the light passing state. The threshold voltage 14 output from the DA converter 5 is decreased step by step via the DA converter control unit 6e.

The DA converter control unit 6e has a function of generating a control signal to the DA converter 5, and generates a control signal 13 designated by the main control unit 6b.
Next, when the binarized output 12 of the comparator 4 changes from the light blocking state to the light passing state, the main control unit 6b operates in the arithmetic unit 6c based on the value of the threshold voltage 14 at the time of changing to the light passing state. The hourly threshold voltage 14 is calculated.

  The calculation of the threshold voltage 14 during operation is performed with reference to the transmittance value of the detected object 21 stored in the storage unit 6d in advance. The storage unit 6d stores the calculated threshold voltage 14 during operation as maintenance information. Next, the main control unit 6b reads out the operating threshold voltage 14 calculated by the calculation unit 6c from the storage unit 6d, and sends a control signal 13 to the DA converter 5 via the DA converter control unit 6e. 5 causes the threshold voltage 14 to be output and shifts to actual operation.

  The transmittance data of the detected object 21 may be created in the storage unit 6d at the time of manufacture. The main controller 6b is connected to an external host system (not shown) via a host interface unit (not shown) as necessary, and the main controller 6b receives transmittance data from the host system and writes it to the storage unit 6d. You may do it. In this way, even when it becomes necessary to change the transmittance due to a change in the detected object, the main control unit 6b receives the transmittance data from the host system and writes it into the storage unit 6d, thereby changing the transmittance. Is possible.

  The contents of the detected object 21 can be handled not only when there is one type but also when there are a plurality of types. When the device of the present invention recognizes what the detected object 21 is in advance, the threshold voltage 14 corresponding to the detected object 21 is set from the LSI 6 to the DA converter 5 in accordance with the detected object 21. The LSI 6 may be controlled. Alternatively, the threshold voltage 14 may be set by storing transmittance data in the storage unit 6d in accordance with the highest transmittance among the plurality of detection objects 21 to be detected. In this case, the reason why the light transmittance is the highest is to prevent erroneous detection of the light transmission state even though the light is blocked.

  Next, the operation of the first embodiment for carrying out the present invention will be described with reference to FIG.

  In the present invention, the light receiving side circuit is configured so that the threshold voltage 14 for binarization can be variably controlled. Then, the sensor output voltage 11 is recognized as the sensor output level at the time of current light transmission, and the optimum threshold voltage 14 is determined and operated based on the sensor output voltage 11.

  First, the output of the DA converter 5, that is, the threshold voltage 14 is set to the maximum with no detected object 21 in the light path in the optical sensor 1 (step S 1).

  Next, in order to recognize the sensor output voltage 11 in the light-transmitting state, an operation of lowering the threshold voltage 14 by one step is performed (step S2). Here, it is determined whether or not the sensor output voltage 11 is greater than or equal to the threshold voltage 14 (step S3). If smaller (step S3, NO), steps S2 and S3 are repeated.

  If it is determined that the sensor output voltage 11 is greater than or equal to the threshold voltage 14 (step S3, YES), the LSI 6 determines that the output state of the comparator 4 has changed from the light shielding state to the light passing state. The threshold voltage is detected and acquired as the sensor output voltage 11 (step S3).

  Next, based on the sensor output voltage 11 in the light-transmitting state recognized in step S3, the value of the threshold voltage 14 in actual operation taking into account the transmittance of the detected object 21 is calculated (step S4). As an example of the calculation, when the maximum transmittance of the detected object is 30%, the voltage value of “30% + α” of the sensor output voltage in the light passing state recognized in step S3 is set as the threshold voltage in actual operation. .

  4 is a diagram showing the relationship between the sensor output voltage 11 and the binarized output 12 of the comparator 4. FIGS. 4A, 4B, and 4C show that the sensor output voltage 11 is the standard, The state of small and large is shown including the threshold voltage 14.

Referring to FIG. 4A, the sensor output voltage 11 in the light passing state recognized in step S3 is V ₂ , and the sensor output voltage 11 when the light is blocked is V ₁ which is 30% of V _2. It becomes.

Therefore, the threshold voltage 14 is set to V ₁ + α = V _to . In this case, the value V _to the threshold voltage 14 will not be erroneously detected and when light shielding state and the light passing to take a value between the sensor output voltage values V ₁ and V ₂ at the time of shading.

  Next, as a final procedure, the LSI 6 sends a control signal 13 to the DA converter 5 so that the threshold voltage 14 in actual operation calculated in step S4 is obtained. In this way, the LSI 6 sets the threshold voltage 14 (step S5). Thereafter, the operation shifts to actual operation, and the presence or absence of the detected object 21 is detected by the optical sensor 1 (step S6).

Here, with reference to FIG. 4B, the value of the threshold voltage 14 when the sensor output voltage 11 is small will be examined. Sensor output voltage 11 in the light passing state recognized in step S3 is V _4, the sensor output voltage 11 when the light-shielding becomes V ₃ is 30% of the value of V _4. Therefore, the threshold voltage 14 is set to V ₃ + α = V _t1 . In this case, the value V _t1 of the threshold voltage 14 takes a value between the sensor output voltage values V ₃ and V _{4 at} the time of light shielding, so that it is not erroneously detected at the time of light shielding.

Further, with reference to FIG. 4C, the value of the threshold voltage 14 when the sensor output is excessive will be examined. Sensor output voltage 11 in the light passing state recognized in step S3 is V _6, the sensor output voltage 11 when the light-shielding becomes V ₅ 30% of the value of V _6. Therefore, the threshold voltage 14 is set to V ₅ + α = V _t2 . In this case, since the value V _t2 of the threshold voltage 14 takes a value between the sensor output voltage values V ₅ and V _{6 at} the time of light shielding, it is not erroneously detected at the time of light shielding.

  It should be noted that the process of obtaining the optical sensor output and determining the threshold voltage (S1 to S5) may be performed periodically or irregularly as necessary. Daily, monthly, every time the power is turned on, and cleaning of the optical sensor 1 during periodic inspections are conceivable, but this is not restrictive.

  In the above example, if the threshold voltage 14 is set to 30% of the sensor output level during light passage, a false detection will occur when the sensor output level fluctuates in the increasing direction. Therefore, the value of α is added as a margin for preventing such erroneous detection. Specifically, it is determined in consideration of fluctuations in the power supply / ambient temperature / sensor facing (optical axis) and the influence of electrical noise, disturbance light, and the like.

  If the value of α is too large, an erroneous detection is made when the sensor output level fluctuates in the direction of decreasing, and it is necessary to determine a value that can prevent this. Specifically, it is necessary to consider fluctuations in power supply / ambient temperature / sensor facing (optical axis), electrical noise, deterioration with time of the light-emitting element 2 that occurs in the period until the next adjustment, and dirt due to dust.

  The transmittance of the detected object 21 varies depending on the material, thickness, and color (pigment). Furthermore, since it depends on the wavelength of the light source at the time of measurement, it is actually necessary to evaluate and measure the detected object to obtain the transmittance. Since the method for measuring the transmittance of the detection object 21 is a method widely known to those skilled in the art, the description thereof is omitted here.

  As an example of the light transmittance of the detected object 21, FIG. 11 shows the relationship between the transmittance of the plastic (polycarbonate), the wavelength, and the thickness. FIG. 12 shows the relationship between the transmittance and wavelength of plastic and a transparent material other than plastic (injection molded PC (polycarbonate), compression molded PC, injection molded PMMA (Polymethl Methacrylate)). . When fillers or pigments are added to these, the transmittance becomes lower than these values. This data is data of a product manufactured by Mitsubishi Engineering Plastics Co., Ltd. and having the product name Iupilon (registered trademark) / Novalex (registered trademark). 11 and 12 are quoted from the technical data posted on the website of Mitsubishi Engineering Plastics Co., Ltd.

  Examples of detected objects include cash cards, receipts, passbooks, slips in ATMs (Automated Teller Machines), and recording media in medium-exchange storage devices, but these are examples and are not limited to these. is not.

  As described above, according to the present embodiment, the optimum “threshold voltage for determining whether light is transmitted or blocked” can be set and operated in accordance with the current sensor state. For this reason, there is an effect that it is possible to avoid the problem of “false detection caused by insufficient sensor output” or “false detection caused by permeation of detected object due to excessive sensor output” due to variations in light emitting elements and light receiving elements in the optical sensor.

  Further, the present invention eliminates the need to sequentially detect the current sensor output level and determine the reference voltage during operation for detecting the detected object, so that the processing speed during operation can be increased. Have. The reason is that the current sensor output level is acquired before the operation for detecting the detected object, and the reference voltage for detecting the presence or absence of the detected object is determined and operated based on the output value of the optical sensor. It is.

  In addition, the invention of the present embodiment has an effect that the adjustment performed before detecting the detected object can be performed in a short time. The reason is as follows. In Patent Document 1, since the light emission amount is adjusted at the time of adjustment, it takes time until the sensor output voltage is stabilized due to a delay in the response of the sensor to the light emission control voltage, and a standby time is required. However, in the present invention, since the amount of light emission is not adjusted and only the threshold voltage is varied, the standby time is unnecessary.

  Further, the invention of the present embodiment has an effect that the detected object can be detected accurately with few malfunctions even if the detected object is a transparent material having a high light transmittance or close to it. This is because the threshold voltage is set so as to ensure a margin for fluctuations in the sensor output voltage according to the transmittance of the detected object.

  Next, a first modification, which is a modification of the first embodiment, will be described with reference to FIGS. The components of the first modification are shown in FIGS. 1 and 8 of the first embodiment.

  Referring to FIG. 8, in the operation of acquiring the sensor output voltage 11 without the detected object 21, the main control unit 6 b is configured such that the binarized output 12 of the comparator 4 from the input unit 6 a changes from the light passing state to the light blocking state. The threshold voltage 14 output from the DA converter 5 is increased step by step through the DA converter control unit 6e until it changes to.

The DA converter control unit 6e has a function of generating a control signal 13 to the DA converter 5, and generates a control signal 13 designated by the main control unit 6b.
Next, when the binarized output 12 of the comparator 4 changes from the light-transmitting state to the light-blocking state, the main control unit 6b operates in the arithmetic unit 6c based on the value of the threshold voltage 14 when the light-transmitting state is changed. The hourly threshold voltage 14 is calculated.

  The calculation of the threshold voltage 14 during operation is performed with reference to the transmittance value of the detected object stored in the storage unit 6d in advance. The storage unit 6d stores the calculated threshold voltage 14 during operation as maintenance information. Next, the main control unit 6b reads the threshold voltage during operation calculated by the calculation unit 6c from the storage unit 6d, and sends the control signal 13 to the DA converter 5 via the DA converter control unit 6e, whereby the DA converter 5 Then, the threshold voltage 14 is output to shift to actual operation.

  Next, the operation of the first modification will be described with reference to FIG. First, the output of the DA converter 5, that is, the threshold voltage 14 is set to the minimum with no detected object 21 in the light path in the optical sensor 1 (step S 11).

  Next, in order to recognize the sensor output voltage 11 in the light-transmitting state, an operation of raising the threshold voltage 14 by one step is performed (step S12). Here, it is determined whether or not the sensor output voltage 11 is smaller than or equal to the threshold voltage 14 (step S13). If larger (step S13, NO), step S12 and step S13 are repeated.

  If it is determined that the sensor output voltage 11 is less than or equal to the threshold voltage 14 (step S13, YES), the LSI 6 determines that the output state of the comparator 4 has changed from the light-transmitting state to the light-blocking state. The previous threshold voltage 14 is detected and stored (step S13). Strictly speaking, the threshold voltage 14 at that time is already light-shielded. However, since the threshold voltage 14 for one step is also considered as an error range, the threshold voltage 14 at that time may be regarded as the sensor output voltage 11 in the lighted state, and the value may be detected and stored (step 13).

  Next, based on the sensor output voltage 11 in the light-transmitting state recognized in step S13, the value of the threshold voltage 14 in actual operation taking into account the transmittance of the detected object is calculated (step S14). As an example of calculation, when the maximum transmittance of the detected object is 30%, the voltage value of “30% + α” of the sensor output voltage 11 in the light passing state recognized in step S13 is the threshold voltage 14 in actual operation. And

  4 is a diagram showing the relationship between the sensor output voltage 11 and the binarized output 12 of the comparator 4. FIGS. 4A, 4B, and 4C show that the sensor output voltage 11 is the standard, The state of small and large is shown including the threshold voltage 14. The description of FIG. 4 regarding the operation of the first modification is the same as that of the first embodiment, and will be omitted.

  Next, as a final procedure, the LSI 6 sends a control signal 13 to the DA converter 5 so that the threshold voltage during actual operation calculated in step S14 is obtained. In this way, the LSI 6 sets the threshold voltage 14 (step S15). Thereafter, the operation is shifted to actual operation, and the presence or absence of the detected object 21 is detected by the optical sensor 1 (step S16).

  Since points other than the description regarding the above-described modification 1 are the same as those of the first embodiment including the effects, the description thereof will be omitted.

  Next, a second modification of the first embodiment will be described below. The difference from the first embodiment is step S4, which will be described with reference to FIGS.

  Based on the sensor output voltage 11 in the light-transmitting state recognized in step S3, the value of the threshold voltage 14 in actual operation taking into account the transmittance of the detected object 21 is calculated (step S4). As a method of calculating the optical sensor output in a state where the detection object 21 is present, a value obtained by multiplying the optical sensor output voltage 11 in the light passing state recognized in step S3 by the transmittance of the detection object 21 is used. A value obtained by adding a value obtained by multiplying the difference between the value and the optical sensor output in the light-transmitting state by a predetermined value β (0 <β <1) is the threshold voltage 14 value.

  Here, FIG. 10 shows, as an example, the relationship between the sensor output voltage 11 and the binarized output 12 of the comparator 4 when β = 0.5 in the case of a detected object having a transmittance of 30%. FIGS. 10A, 10B, and 10C show the state in which the sensor output voltage 11 is standard, small, and large, including the threshold voltage 14, respectively.

Referring to FIG. 10A, the sensor output voltage 11 in the light passing state recognized in step S3 is V ₂ , and the sensor output voltage 11 when light is blocked is V ₁ which is 30% of V _2. It becomes.

Therefore, the threshold voltage 14 is set to V ₁ + β (V ₂ −V ₁ ) = V _to . In this case, the value V _to of the threshold voltage 14 takes a value of (V ₁ + V ₂ ) / 2, which is a value between the sensor output voltage values V ₁ and V _{2 at} the time of light shielding. It will not be detected by mistake.

Here, with reference to FIG. 10B, it will be considered what the value of the threshold voltage 14 becomes when the sensor output voltage 11 is small. Sensor output voltage 11 in the light passing state recognized in step S3 is V _4, the sensor output voltage 11 when the light-shielding becomes V ₃ is 30% of the value of V _4. Therefore, the threshold voltage 14 is set to V ₃ + β (V ₄ −V ₃ ) = V _t1 . In this case, the value V _t1 threshold voltage 14 will not be erroneously detected and when light shielding state and the light passing to take a value that bisects between the sensor output voltage V ₃ and V ₄ at the time of shading. Compared with FIG. 4B, since the margin on the light transmission side is large, the possibility of erroneous detection is reduced even if there is a fluctuation such as a decrease in the sensor output voltage. effective.

Further, with reference to FIG. 10C, the value of the threshold voltage 14 when the sensor output is excessive will be examined. Sensor output voltage 11 in the light passing state recognized in step S3 is V _6, the sensor output voltage 11 when the light-shielding becomes V ₅ 30% of the value of V _6. Therefore, the threshold voltage 14 is set to V ₅ + β (V ₆ −V ₅ ) = V _t2 . In this case, since the value V _t2 of the threshold voltage 14 takes a value between the sensor output voltages V ₅ and V _{6 at} the time of light shielding, the light shielding time and the light passing time are not erroneously detected.

In the second modification, in addition to the effect of the first embodiment, the sensor output voltage when the light is blocked is proportional to the difference between the sensor output voltage 11 when the light is blocked and the sensor output voltage 11 when the light is transmitted. Since the threshold voltage 14 is determined by adding the values, it is possible to avoid a case where the margin is reduced and to reduce the possibility of erroneous detection.
Further, a modified example in which the features of the modified example 1 and the features of the modified example 2 are combined is also conceivable. However, since this configuration and effect can be clearly understood by those skilled in the art from the above description, a detailed description thereof will be omitted.

  Next, the operation of the second embodiment for carrying out the present invention will be described with reference to FIG. 1 and FIG. The block diagram of the second embodiment can be expressed in FIG.

  In the second embodiment of the present invention, similarly to the first embodiment, the light receiving side circuit is configured so that the threshold voltage 14 for binarization can be variably controlled. Then, the sensor output voltage 11 is recognized as the sensor output level at the time of current light transmission, and the optimum threshold voltage is determined and operated based on the sensor output voltage 11.

  First, the output of the DA converter 5, that is, the threshold voltage 14 is set to the maximum with no detected object 21 in the light path in the optical sensor 1 (step S 21).

  Next, in order to recognize the sensor output voltage 11 in the light passing state, an operation of lowering the threshold voltage 14 by X steps (X is an integer of 2 or more) is performed (step S22). Here, it is determined whether or not the sensor output voltage 11 is greater than or equal to the threshold voltage 14 (step S23). If smaller (step S23, NO), steps S22 and S23 are repeated.

  If it is determined that the sensor output voltage 11 is greater than or equal to the threshold voltage 14 (step S23, YES), the LSI 6 determines that the light has shifted from the light shielding state to the light passing state but the threshold voltage has been lowered too much. Is raised by one step (step S24). Here, it is determined whether or not the sensor output voltage 11 is smaller than or equal to the threshold voltage 14 (step S25). If larger, step S24 and step S25 are repeated.

  If it is determined that the sensor output voltage 11 is smaller than or equal to the threshold voltage 14 (step S25, YES), the LSI 6 determines that the output state of the comparator 4 has changed from the light-transmitting state to the light-blocking state. The previous threshold voltage 14 is detected and stored (step S25). This is because the threshold voltage 14 at that time is already light-shielded. However, since the threshold voltage 14 for one step is also considered as an error range, the threshold voltage 14 at that time may be considered as the sensor output voltage in the light state, and the value may be detected and stored (step 25).

  Subsequent steps S26, S27, and S28 are the same as steps S4, S5, and S6 of FIG.

  In this embodiment, the state of the binarized output 12 is varied with a constant width of two steps or more until the state of the binarized output 12 changes, and after the state is changed, it is varied one step at a time in the reverse direction until the state of the binarized output 12 changes. Take the step of detecting. For this reason, in addition to the effect of the first embodiment, there is an effect peculiar to the present embodiment that the detection speed of the sensor output level is further shortened.

  Next, a third modification, which is a modification of the second embodiment, will be described with reference to FIGS.

  The block diagram of Modification 3 can be expressed in FIG.

  As in the first embodiment, the third modification of the present invention configures the light receiving side circuit so that the threshold voltage 14 for binarization can be variably controlled. Then, the sensor output voltage 11 is recognized as the sensor output level at the time of current light transmission, and the optimum threshold voltage 14 is determined and operated based on the sensor output voltage 11.

  First, the output of the DA converter 5, that is, the threshold voltage 14 is set to the minimum with no detected object 21 in the light path in the optical sensor 1 (step S 31).

  Next, in order to recognize the sensor output voltage 11 in the light-transmitting state, an operation of raising the threshold voltage 14 by X steps (X is an integer of 2 or more) is performed (step S32). Here, it is determined whether or not the sensor output voltage 11 is smaller than or equal to the threshold voltage 14 (step S33). If larger (step S33, NO), step S32 and step S33 are repeated.

  If it is determined that the sensor output voltage 11 is smaller than or equal to the threshold voltage 14 (YES in step S33), the LSI 6 determines that the threshold voltage 14 has been raised too much although the light-transmission state has changed to the light-shielding state. The voltage 14 is lowered by one step (step S34). Here, it is determined whether or not the sensor output voltage 11 is greater than or equal to the threshold voltage 14 (step S35). If smaller, step S34 and step S35 are repeated.

  If it is determined that the sensor output voltage 11 is greater than or equal to the threshold voltage 14 (step S35, YES), the LSI 6 determines that the output state of the comparator 4 has changed from the light shielding state to the light passing state, and the threshold at that time is determined. The voltage 14 is considered to be the sensor output voltage 11 in a light-transmitting state, and its value is detected and stored (step 35).

  Subsequent steps S36, 37, and S38 are the same as steps S4, S5, and S6 of FIG.

  The operational effect of the third modification is the same as that of the second embodiment. In the third modification, the binarized output 12 is varied by a constant of two steps or more until the state of the binarized output 12 changes. Steps are taken to vary and detect until the state of the value output 12 changes. For this reason, in addition to the effect of Example 1, there exists an effect that the detection speed of a sensor output level further shortens.

  Next, Modification 4 which is a modification of Embodiment 2 will be described below. Step S26 is different from the second embodiment, and this point can be understood from FIGS. 6 and 10 and the description of step 4 of the second modification of the first embodiment.

  Based on the sensor output voltage 11 in the light-transmitting state recognized in step S25, the value of the threshold voltage 14 in actual operation taking into account the transmittance of the detected object is calculated (step S26). As an example of the calculation, when the maximum transmittance of the detected object is 30%, the value and the light transmission are obtained by multiplying the light sensor output voltage 11 in the light passing state recognized in step S3 by the transmittance of the detected object. A value obtained by multiplying the difference from the optical sensor output voltage 11 in the state by a predetermined value β (0 <β <1) is added. Thus, since it can be understood in the same manner as this by the description of the second modification of the first embodiment, the description is omitted.

  Next, a third embodiment of the present invention will be described with reference to FIGS.

  When the opposing distance (optical path length) between each element in the light emitting element 2 and the light receiving element 3 is long, the sensor output voltage 11 decreases in the configuration of the first embodiment. In order to solve this problem, when the facing distance is long, a pulse forward current having a larger amplitude than the DC forward current is supplied to the light emitting element 2 such as a light emitting diode, thereby increasing the radiation intensity and increasing the sensor output voltage 11. be able to.

  However, when a pulse forward current is applied, it is necessary to blink the light emission of the light emitting element 2. For this reason, the third embodiment includes a switching element 7 such as a transistor on the light emitting circuit side in addition to the configuration of the first embodiment shown in FIG. Since the other components of the third embodiment are the same as those of the first embodiment except for the LSI 61 described later, the description thereof is omitted.

  The LSI 61 needs to have a function of detecting the sensor output 11 when the light emitting element 2 is turned on in synchronization with the blinking of the light emitting element 2. In order to realize this function, a synchronization timing generation unit 6f and an ON / OFF control signal generation unit 6g are provided in addition to the configuration of the LSI 6 in the first embodiment.

  The synchronization timing generator 6 f and the ON / OFF control signal generator 6 g control the switching element 7 with the ON / OFF control signal 15, and pass a pulse forward current larger than the DC forward current to the light emitting element 2.

  Since the light emitting element 2 is turned off when the switching element 7 is OFF, the binary output from the comparator 4 based on the sensor output voltage 11 and the threshold voltage 14 when the light emitting element 2 is turned on. The control output 12 is latched by the main control unit 6b and used as valid data. This is true both when detecting a detected object during operation and when acquiring the optical sensor output voltage 11 during adjustment.

  The synchronization timing generation unit 6f generates an ON / OFF timing signal 17 for generating the ON / OFF control signal 15 and a latch timing signal 16 to be supplied to the main control unit 6b in synchronization with this signal. The main control unit 6b can latch valid data when is turned on.

  The ON / OFF control signal generator 6g is a circuit for generating an ON / OFF control signal 15 suitable for the switching element 7, and specifically performs signal level conversion and the like.

  In this manner, the binarized output 12 output from the comparator 4 such as a comparator in the light receiving side circuit is latched by the LSI 61 in synchronization with the ON / OFF control signal 15 when the switching element 7 is ON (lighted). The latched data is used as valid data as the state of the optical sensor 1.

  As in this embodiment, when a pulse forward current larger than a DC forward current is passed through the light emitting element 2 such as a light emitting diode to increase the radiation intensity, erroneous detection caused by transmission of the detected object is likely to occur. However, this problem can be avoided by appropriately setting the threshold voltage by the same procedure (steps S1 to S6 in FIG. 2) as the operation described in the first embodiment. In this case, the operation of the present embodiment is the same as the operation described in the first embodiment.

  Further, the procedure for setting the threshold voltage at the time of adjustment before detection of the detection object when the configuration of the present embodiment is similarly applied to the first modification, the second modification, the second embodiment, the third modification, and the fourth modification is as follows. Since it is the same as the content described as operation | movement in an Example and a modification, description is abbreviate | omitted.

  In this embodiment, the switch element 7 and the LSI 6 that controls the switch element 7 cause the pulse forward current larger than the DC forward current to flow through the light emitting element 2 such as a light emitting diode, thereby increasing the radiation intensity and increasing the sensor output voltage 11. I am letting. For this reason, even when the facing distance is long, it is possible to operate with the optimum threshold voltage according to the current sensor state, and there is an effect that erroneous detection can be prevented.

  The present invention can be applied to an apparatus having a structure for detecting a detected object using a mechatronic product or other optical sensor.

It is a block diagram which shows the structure of the detected object detection apparatus by Example 1 and 2 of this invention. It is a flowchart for demonstrating schematic operation | movement of the detected object detection apparatus by Example 1 of this invention. It is a block diagram which shows the structure of the detected object detection apparatus by Example 3 of this invention. It is a figure which shows the relationship with the sensor output voltage in the comparator of the Example of this invention, a threshold voltage, and a binarization output. It is a flowchart for demonstrating schematic operation | movement of the detected object detection apparatus by the modification 1 of this invention. It is a flowchart for demonstrating schematic operation | movement of the detected object detection apparatus by Example 2 of this invention. It is a flowchart for demonstrating schematic operation | movement of the detected object detection apparatus by the modification 3 of this invention. It is a block diagram which shows the structure of LSI6 of Example 1 and 2 of this invention. It is a block diagram which shows the structure of LSI6 of Example 3 of this invention. It is a figure which shows the relationship between the sensor output voltage in the comparator of the modification 2 and the modification 4 of this invention, a threshold voltage, and a binarization output. It is a graph which shows an example of the relationship between the light transmittance of a polycarbonate, and a wavelength. It is a graph which shows an example of the relationship between the light transmittance of a transparent material other than polycarbonate, and a wavelength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical sensor 2 Light emitting element 3 Light receiving element 4 Comparator 5 DA converter 6 LSI
61 LSI
6a input unit 6b main control unit 6c arithmetic unit 6d storage unit 6e DA converter control unit 6f synchronization timing generation unit 6g ON / OFF control signal generation unit 7 switching element 8 resistance 9 resistance 11 sensor output voltage 12 binarized output 13 control signal 14 Threshold voltage 15 ON / OFF control signal 21 Detected object

Claims (25)

An optical sensor including a light emitting element and a light receiving element is disposed so that light from the light emitting element to the light receiving element passes through a position of the detected object, and the presence or absence of the detected object is determined according to an output state of the optical sensor. Is a detection object detection device for detecting
A reference voltage generator;
A comparator that compares the optical sensor output value with a reference voltage output from the reference voltage generator and detects the presence or absence of the detection object according to the result;
A control unit that supplies a control signal for causing the reference voltage generation unit to output the reference voltage;
If necessary, the control unit acquires the optical sensor output value before detecting the detected object, and determines the reference voltage when detecting the presence or absence of the detected object based on the optical sensor output value. A detection object detection device characterized by: The detection object detection apparatus according to claim 1,
An apparatus for detecting the presence or absence of the detection object depending on whether the optical sensor output is in a light-transmitting state or a light-shielding state;
If necessary, the control unit obtains an optical sensor output value based on a change in the output of the comparator when the reference voltage is changed before detecting the detected object, and based on the optical sensor output value. The detection object detecting device, wherein the reference voltage for detecting the presence or absence of the detection object is determined. The detection object detection apparatus according to claim 2,
The light sensor output is obtained as a light sensor output value in a light-transmitting state by changing the output of the comparator when the reference voltage is changed in a decreasing direction with the light sensor output in a light-transmitting state. A detection object detection apparatus for determining the reference voltage when detecting the presence or absence of a detection object. The detection object detection apparatus according to claim 2,
The light sensor output is obtained as a light sensor output value by changing the output of the comparator when the reference voltage is changed in the increasing direction with the light sensor output in a light-transmitting state. A detection object detection apparatus for determining the reference voltage when detecting the presence or absence of a detection object. The detection object detection device according to claim 3,
When the output of the comparator is reversed by changing the reference voltage stepwise, the reference voltage immediately before is obtained as the light sensor output value of the light state, and the detection is performed based on the light sensor output value. A detected object detection apparatus for determining the reference voltage when detecting the presence or absence of an object. The detection object detection apparatus according to claim 2,
The reference voltage is changed stepwise by multiple steps and the output of the comparator is inverted and then changed one step at a time in the opposite direction, and the reference voltage immediately before or after the output of the comparator is inverted again. A detected object detection apparatus that obtains an optical sensor output value in a light state and determines the reference voltage when detecting the presence or absence of the detected object based on the optical sensor output value. The detection object detection device according to claim 2,
A detected object detection apparatus characterized in that a light sensor output value in a light shielding state is calculated from a light sensor output value in a light passing state and a value obtained by adding a constant value to the output is used as the reference voltage. The detection object detection device according to claim 2,
A detected object detection apparatus characterized in that a value obtained by adding a constant value α to a value obtained by multiplying an output value of an optical sensor in a light-transmitting state by a transmittance of the detected object is used as the reference voltage. The detection object detection device according to claim 2,
A value obtained by calculating a light sensor output value in a light-shielded state from a light sensor output value in a light-transmitting state and adding a value obtained by multiplying the difference between both light sensor outputs by a predetermined value β (0 <β <1). Is the reference voltage. The detection object detection device according to claim 2,
A value obtained by multiplying the value obtained by multiplying the light sensor output value in the light passing state by the transmittance of the detected object and the difference between the value and the light sensor output in the light passing state by a predetermined value β (0 <β <1). A detected object detection apparatus characterized in that a value obtained by adding the values is used as the reference voltage. The detection object detection apparatus according to claim 1,
A detection object detection apparatus, further comprising a switch for turning on and off the light emitting element, wherein the control unit sends a control signal for turning on and off the switching element to the switch element to flow a pulsed current to the light emitting element. The detection object detection apparatus according to claim 11,
The controller detects the output of the comparator in synchronization with on / off of the light emitting element and detects the output of the comparator in synchronization with on / off of the light emitting element. An optical sensor having a light emitting element and a light receiving element; a reference voltage generating unit; and a comparator for comparing an output of the optical sensor with a reference voltage output from the reference voltage generating unit. A control device that constitutes a detection object detection device that arranges the optical sensor so that light reaching the element passes through the position of the detection object, and detects the presence or absence of the detection object according to an output state of the optical sensor,
A control signal for outputting the reference voltage to the reference voltage generator is supplied, and if necessary, the optical sensor output value is acquired before detecting the detected object, and the optical sensor output value is And determining a reference voltage for detecting the presence or absence of the detected object. A detection object detection method for detecting the presence or absence of the detection object depending on whether a light sensor having a light emitting element and a light receiving element is in a light transmission state or a light shielding state,
A first step of acquiring an optical sensor output value before detecting the detected object, if necessary;
A second step of determining a reference voltage of the optical sensor output value when detecting the presence or absence of the detection object based on the optical sensor output value;
And a third step of comparing the output value of the optical sensor with the reference voltage and detecting the presence or absence of the detected object based on the comparison result. The detection object detection method according to claim 14,
The first step is to detect an optical sensor output value based on a change in a comparison result when the reference voltage is changed before detecting the detection object, if necessary. The detection object detection method according to claim 15,
The detected object is obtained as a light sensor output value in a light-transmitting state based on a change in a comparison result when the light output from the light sensor is in a light-transmitting state and the reference voltage is changed in a decreasing direction. Detection method. The detection object detection method according to claim 15,
The detected object is obtained as a light sensor output value in a light-transmitting state by a change in a comparison result when the light output from the light sensor is in a light-transmitting state and the reference voltage is changed in an increasing direction. Detection method. The detection object detection method according to claim 16 or 17,
In the first step, the reference voltage is changed stepwise, and the reference voltage immediately before or after the comparison result is inverted is acquired as an optical sensor output value in a light state. Method. The detection object detection method according to claim 14 or 15,
In the first step, the reference voltage is changed stepwise by a plurality of steps and the comparison result is inverted and then changed step by step in the opposite direction. When the comparison result is inverted again or immediately before the reference voltage, A detection object detection method, comprising: acquiring an output value of an optical sensor in a light-transmitting state. The detection object detection method according to claim 14 to 19,
In the second step, the detection value detection is characterized in that a value obtained by calculating a light sensor output value in a light shielding state from a light sensor output value in a light passing state and adding a constant value to the output is used as the reference voltage. Method. It is a detection object detection method of Claims 14 thru / or 20,
In the second step, the reference voltage is a value obtained by adding a constant value α to a value obtained by multiplying the light sensor output value in a light-transmitting state by the transmittance of the detection object. The detection object detection method according to claim 14 to 19,
In the second step, the light sensor output value in the light blocking state is calculated from the light sensor output value in the light passing state, and the difference between the light sensor outputs is multiplied by a predetermined value β (0 <β <1). A detected object detection method characterized in that a value obtained by adding the obtained values is used as the reference voltage. The detection object detection method according to claim 14 to 19,
In the second step, a value obtained by multiplying the optical sensor output value in the light-transmitting state by the transmittance of the detection object and a difference between the value and the optical sensor output in the light-transmitting state is a predetermined value β (0 <β < A detected object detection method characterized in that a value obtained by adding a value obtained by multiplying 1) is used as the reference voltage. The detection object detection method according to claim 14 to 23,
A detection object detection method, wherein a pulsed current is caused to flow through a light emitting element by turning on and off the light emitting element in the first and third steps. The detection object detection method according to claim 24,
In the first and third steps, a detected object detection method that captures a comparison result between the photosensor output value and the reference voltage in synchronization with on / off of the light emitting element.

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