JP3790659B2 - Optical detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is an apparatus for detecting whether or not a user is within a set distance range in an automatic faucet, an automatic washing toilet, a washbasin, an automatic opening / closing toilet seat, a toilet flushing device, automatic lighting, automatic heating, etc. The present invention relates to an optical detection device suitable for application.
[0002]
[Prior art and problems to be solved by the invention]
  In this type of instrument, as a device for detecting whether there is a measurement object within a set distance range, that is, whether there is a user within the set distance range, an infrared diffuse reflection type detection device has been widely used conventionally. Yes.
[0003]
  FIG. 4 shows the principle diagram.
  This optical detection device applies light emitted from an infrared light emitting diode (light emitting element) 200 to a measurement object (user) 204 and causes the reflected light (diffused light) to enter a photodiode (light receiving element) 208. In this case, however, the amount of light incident on the photodiode 208 increases if the measurement object 204 is close, and conversely, the amount of light incident on the photodiode 208 decreases if the measurement object 204 is far away.
  By using this, that is, according to the amount of reflected light incident on the photodiode 208, the distance of the measurement object 204 can be determined.
[0004]
  However, in the case of this infrared diffuse reflection type optical detection device, the amount of light incident on the photodiode 208 varies greatly depending on the color of the measurement object 204, specifically the color of the clothes worn by the user. There is a problem such as.
[0005]
  For example, when the color of the measurement object 204 is white, the amount of reflected light incident on the photodiode 208 increases. Conversely, when the color is black, the amount of reflected light incident on the photodiode 208 decreases.
  Therefore, if the distance is adjusted in the case of white, when the measurement object 204 is black, the amount of reflected light incident on the photodiode 208 is too small, so that the measurement object 204 is at the same distance. It becomes impossible to detect.
[0006]
  On the other hand, as an optical detection device, an infrared ranging optical detection device using a semiconductor position detection element (PSD: Position Scnsitivc Photo Dctcctor) that outputs a photocurrent corresponding to an incident position from both ends is known.
  FIG. 5 shows the principle diagram.
  This optical detection device is of the “logarithmic conversion + difference extraction” method utilizing the logarithmic characteristics of a semiconductor, and the pulsed light emitted from the light emitting diode 200 passes through a light projection lens (condensing lens) 202 to the measurement object 204. Projected. The reflected light enters the surface of the semiconductor position detecting element (light receiving element) 210 through the light receiving lens (condensing lens) 206 and forms an image.
[0007]
  Here, the semiconductor position detection element 210 is a PIN photodiode having continuous resolution, and is a photoelectric conversion element that generates two photocurrents whose ratio is determined by the spot image formation position on the light receiving surface. The light incident on 210 is photoelectrically converted and divided and output from electrodes attached to both ends as a photocurrent.
  That is, when the spot light is incident on the semiconductor position detecting element 210, a charge proportional to the light energy is generated at the incident position, and the generated charge passes through the surface layer as a photocurrent and is output from each of the electrodes at each end. .
  Since the resistance layer on the surface is made to have a uniform resistance value over the entire length and the entire surface, the photocurrent is divided in inverse proportion to the distance to the electrode at each end, that is, the distance to each end. It is taken out.
[0008]
  For example, when spot light is incident on the center position of the light receiving surface as shown in FIG. 6A, the ratio of two photocurrents from each end of the semiconductor position detecting element 210 is
        I_L1: I_L2= 1: 1
  It becomes.
  When spot light is incident at a ratio of 1: 2 from both ends as shown in FIG.
        I_L1: I_L2= 1: 2
  Furthermore, as shown in FIG. 5C, when spot light is incident at a position of 1: 3 from both ends.
        I_L1: I_L2= 1: 3
  It becomes.
[0009]
  Accordingly, when the distance to be determined is the distance X in FIG. 5, the threshold of the photocurrent of the semiconductor position detecting element 210 is I_L1/ I_L2= A / b, I_L1/ I_L2Is larger than a / b, the measurement object 204 is farther than X and I_L1/ I_L2Is smaller than a / b, it can be determined that the measurement object 204 is closer to X.
[0010]
  In the optical detection device shown in FIG. 5, two photocurrents of the semiconductor position detecting element 210 are used as circuits for determining the threshold of the photocurrent ratio, and the currents are converted into currents in the semiconductors 212 and 214 having logarithmic characteristics such as diodes. The voltage is converted and the difference between the two voltages logarithmically converted by the subtractor 216 is calculated as I_L1/ I_L2The value log (I corresponding to_L1) -Log (I_L2), And the voltage threshold value V is compared with a comparator (microcomputer) 218.₀For example, if the distance to be determined in FIG.₀The
        V₀= Log (a / b)
  Then, it can be determined whether or not the measurement object 204 is farther than X.
[0011]
  In the case of the optical detection device shown in FIG. 5, since the light receiving spot position of the semiconductor position detection element 210 is read, there is an advantage that the detected value of the distance does not depend on the color of the measurement object 204, that is, the reflectance.
  However, in the case of the optical detection device shown in FIG. 5, since the power consumption is large, it is difficult to expand the application to battery-driven portable devices.
[0012]
  In the case of the optical detection device shown in FIG. 5, the photocurrent value flowing out of the semiconductor position detection element 210 is about several hundred nA in the case of the measurement object 204 having a low reflectance such as black, and the reflectance such as white. In the case of the measurement object 204 having a high value, a current of several hundred μA may flow, and the current range varies greatly depending on the reflectance and distance of the measurement object 204.
[0013]
  In the method based on “logarithmic conversion + difference extraction” in FIG. 5, when the photocurrent is small, there is a phenomenon that the time from when the photocurrent starts to flow until the logarithmically converted voltage is generated becomes longer.
  This will be explained with reference to FIG._L1, I_L2Observes the voltages of the semiconductors 212 and 214 in order to charge the stray capacitance of the capacitor component parasitic in the circuit to which the semiconductors 212 and 214 that perform logarithmic conversion are connected before flowing through the semiconductors 212 and 214 that perform logarithmic conversion. The time when the logarithmically converted voltage value cannot be obtained (unstable time) t₁Exists.
[0014]
  When the stray capacitance is C, the photocurrent is I, and the logarithmically converted voltage is V, the time t required to charge the stray capacitance C₁Is
        t₁= V × C ÷ I (1)
  And the charge time t of the stray capacitance C₁Since the voltage rises inside, the logarithmically converted value cannot be read.
[0015]
  For example, in the actual measurement example of the present inventor, the photocurrent I in the case of the black measurement object 204 in FIG._L2= Forward voltage V of diode at 155 nA, 155 nA₂≒ 0.36V, circuit stray capacitance ≒ 60pF, time t for charging stray capacitance to 0.36V₁From equation (1)
        t₁= 140μSEC
  Thus, the logarithmically converted value cannot be read unless there is a “light emission time” of at least 140 μSEC or more.
[0016]
  The current required for light emission is several tens to several hundreds mA, which is larger than the several mA of the received light signal processing circuit. Therefore, the current consumption of the entire apparatus cannot be reduced.
  That is, in order to obtain a stable detection value, it is necessary to continuously irradiate pulsed light from the light emitting diode 200 for a long time, which consumes a large amount of power.
  For this reason, an optical detection apparatus using this kind of semiconductor position detection element has not been applied to a conventional battery powered device.
[0017]
  Therefore, the present applicant has proposed an optical detection device that performs signal processing on the photocurrent from the semiconductor position detection element by another method (Japanese Patent Laid-Open No. 7-209435).
  FIG. 8 shows the principle diagram.
  In this optical detection device, as shown in the figure, two photocurrents from both ends of the semiconductor position detection element 210 are amplified by the amplifiers 220 and 222, and at that time, the amplification factor is set only by the amplifier 222 on one side. As possible, each photocurrent is amplified at a ratio inversely proportional to the ratio of the distance from the set incident position to each end in the semiconductor position detecting element 210, and whether or not the voltage level becomes the same level after the amplification is compared by the comparator 218. Thus, it is determined whether the ratio of the two photocurrents flowing from the semiconductor position detecting element 210 is larger or smaller than a set constant current ratio.
[0018]
  However, in the case of the optical detection device shown in FIG. 8, it is necessary to avoid saturation of the amplifiers 220 and 222 in order to accurately compare the amplified signals.
  Therefore, the maximum output amplitude of the amplifier 222 is set to the photocurrent value I flowing out of the semiconductor position detecting element 210._L2Is set to several hundred μA, which is a photocurrent corresponding to an object 204 with high reflectivity such as white, in the case of the object 204 with low reflectivity such as black, the photocurrent I_L2Is 1/1000, the output of the amplifier 222 is also 1/1000 of the largest amplitude.
[0019]
  For example, when the power supply voltage is 5V, even if the output of the white object is set to 5V, the output of the black object is 5 mV, which is so small that it cannot be distinguished from the signal noise. Can not.
  Therefore, in the optical detection apparatus disclosed in Japanese Patent Application Laid-Open No. 7-209435, the “amplification level reduction” is performed to increase the amplification factor so that amplification can be performed even when the photocurrent is small. Ingenuity has been made to incorporate the “circuit” into the circuit.
  FIG. 9 shows a specific circuit configuration. As shown in FIG. 9, a light emission level reduction circuit 224 is incorporated in the circuit.
[0020]
  However, even in this case, the time required for lowering the light emission level, that is, the so-called negative feedback reaction time is required, and the output may be saturated during the negative feedback reaction time. It is necessary to integrate by increasing the light emission time of the light source, or by integrating the light emission repeatedly several times so that the influence is reduced even if the output is saturated during the negative feedback reaction time.
[0021]
  Since the reaction time of the negative feedback circuit is a maximum of 30 μSEC, the negative feedback reaction time requires about 125 μSEC or more in the entire negative feedback circuit, and the integrated light emission time for obtaining one measurement result cannot be shorter than 125 μSEC. As a result, the power consumption of the entire apparatus increases.
[0022]
[Means for Solving the Problems]
  The optical detection device of the present invention has been devised to solve such problems.
  Thus, according to the first aspect of the present invention, (a) a light emitting element that emits pulsed light toward an object to be measured; (b) receiving a reflected light from the object and outputting a photocurrent from both ends; and A light receiving element comprising a semiconductor position detecting element that proportionally decreases or increases the photocurrent from each end in accordance with the distance from the incident position of the reflected light to each end; and (c) each of the light receiving elements in the light receiving element. First and second current-voltage conversion capacitors for converting the photocurrent from the end, and (d) detecting and comparing the respective voltage ratios of the first and second current-voltage conversion capacitors, and within the set distance range Voltage ratio detection means for determining the presence or absence of an object and outputting a detection signalAnd theThe voltage ratio detection means compares the length of the discharge time when the electric charges of the first and second current-voltage conversion capacitors are discharged at a constant current by the first and second dischargers, and the object within the set distance range It is characterized by determining the presence or absence of an object.
[0023]
  Claim 2 claims claim1The first and second current / voltage conversion capacitors have the same capacity, and the first and second dischargers respectively correspond to the first and second current / voltage conversion capacitors. The discharge amount ratio is a ratio corresponding to the threshold value of the ratio of the distance from the set incident position to each end of the light receiving element, and discharge occurs when the reflected light is incident on the set incident position. It is characterized in that it ends at the same time.
[0024]
  The third aspect is the first aspect., 2In any one of the above, the voltage ratio detection means charges the first and second comparison capacitors corresponding to the first and second current-voltage conversion capacitors, respectively, through the buffers with the corresponding voltages, The charge of the first and second comparison capacitors is discharged by the first and second dischargers.
[0025]
  The fourth aspect is the first aspect.3In any of the above, the optical detection device is an automatic faucet, an automatic flush toilet, a washbasin, an automatic open / close toilet seat, a toilet flushing device, automatic lighting, and a user detection device in automatic heating.The
[0026]
[Operation and effect of the invention]
  Less thanAs described above, the optical detection device of the present invention uses the first and second current-voltage conversion capacitors as means for converting the photocurrent from each end of the semiconductor position detecting element into voltage, and the first and second current and voltage conversion capacitors. The voltage ratios of the current-voltage conversion capacitors are compared by the voltage ratio detection means, the presence / absence of an object within the set distance range is determined and a detection signal is output. According to the present invention, the optical ratio shown in FIG. The time until the stray capacitance of the capacitor component parasitic to the circuit connected to the semiconductor is charged becomes unstable, as in the case where the photocurrent from the detection device, that is, the semiconductor position detection element is converted into voltage by logarithmic conversion by the semiconductor. After that, there is no problem that correct voltage ratio detection, that is, actual measurement can be performed for the first time, and the detection operation can be completed in a short time.
[0027]
  Accordingly, the pulse emission time per one time from the light emitting element can be shortened, and the power consumption can be reduced.
  Therefore, according to the present invention, there is a great effect that it can be applied to a detection device of a portable device using a dry battery as a power source.
[0028]
  Here, the voltage ratio detection means compares the discharge time when the charge of the current-voltage conversion capacitor is discharged with a constant current by a discharger, and determines the presence or absence of an object within the set distance range.Have.
[0029]
  ThisIn this case, the first and second current-voltage conversion capacitors have the same capacity, and the discharge amounts of the first and second dischargers corresponding to the first current-voltage conversion capacitor and the second current-voltage conversion capacitor The ratio is a ratio corresponding to the threshold value of the ratio of the distance from the set incident position to each end of the light receiving element, and discharge is terminated simultaneously when reflected light enters the set incident position. (Claims)2).
  In this way, whether or not there is an object within the set distance range can be detected easily and accurately by checking whether or not the discharge has been completed at the same time.
[0030]
  In the present invention, the voltage ratio detection means is charged to the first and second comparison capacitors via a buffer at a voltage corresponding to the voltages of the first and second current-voltage conversion capacitors, and the charge of the comparison capacitors is charged. Can be discharged by the first and second dischargers.3).
  In this case, there is an advantage that the measurement accuracy of the discharge time can be freely determined by changing the capacitances of the first and second current-voltage conversion capacitors and the first and second comparison capacitors.
[0031]
  Furthermore, the present invention can be suitably applied as a detection device in an automatic faucet, an automatic washing toilet, a washbasin, an automatic opening / closing toilet seat, a toilet flushing device, automatic lighting, and automatic heating (claims).4).
  Here, the toilet bowl local cleaning device refers to an apparatus for cleaning the toilet user's local area by spraying cleaning water from the cleaning nozzle.
[0032]
【Example】
  Next, embodiments of the present invention will be described in detail with reference to the drawings.
  In FIG. 1, reference numeral 10 denotes an optical detection apparatus of the present example, and reference numeral 12 denotes a light emitting element composed of an infrared light emitting diode that projects pulsed light toward a measurement object 14.
  The light from the light emitting element 12 is projected onto the measurement object 14 through the light projecting lens (condensing lens) 16.
[0033]
  Reference numeral 18 denotes a light receiving element composed of a semiconductor position detecting element (hereinafter abbreviated as PSD). Reflected light from the object 14 enters the light receiving element 18 through a light receiving lens (condensing lens) 22.
  The light receiving element 18 outputs a photocurrent corresponding to the incident position, more specifically, a photocurrent inversely proportional to the distance from the incident position to both ends.
[0034]
  FIG. 2 specifically shows the circuit configuration of the optical detection device 10.
  In the figure, Q1 is a transistor for driving the light emitting element 12, and R2 is a resistor for driving the transistor Q1. Further, R1 is a resistor for setting the light emission current, and C7 is a capacitor for charging the light emission current.
[0035]
  Reference numeral 20 denotes a measurement timing setting circuit for setting the measurement timing by controlling the operation timing of the transistor Q1, to which capacitors C50 and C51 are connected.
  The capacitor C50 is for setting the light emission timing (waiting time from power-on to light emission), and the capacitor C51 is for setting the light emission time (length of light emission) of the pulsed light.
[0036]
  The light emitting element 12 emits pulses at the timing (cycle) set in this way and at the set emission time.
  The light pulse-emitted from the light emitting element 12 is reflected by the measurement object 14 as shown in FIG. 1, and the reflected light enters the light receiving element 18 made of PSD.
[0037]
  As is clear from FIG. 1, the incident position enters the position near the lower end in the figure if the distance to the measurement object 14 is short, and enters the position near the upper end in the figure if the distance is long.
  A photocurrent having a magnitude corresponding to the incident position, that is, inversely proportional to the distance from the incident position to each end, is output from each end.
[0038]
  Photocurrents extracted from the respective ends of the light receiving element 18 are amplified by the photocurrent amplifier circuits 23 and 24, respectively, and charged to the first and second first stage capacitors (current / voltage conversion capacitors) C1 and C2, respectively. The photocurrents are converted into voltages in the first stage capacitors C1 and C2.
  Here, the first stage capacitors C1 and C2 have the same capacity.
[0039]
  C3 and C4 are ambient light storage capacitors, and 26 and 28 are ambient light cancellers. Ambient light components of the photocurrent from the light receiving element 18 are ambient light cancellers 26 and 28 based on the storage of the ambient light storage capacitors C3 and C4. As shown in FIG. 3A, the voltages of the first and second first stage capacitors C1 and C2 are held at the reference voltage.
[0040]
  In the apparatus of this example, after the photocurrent is voltage-converted by these first stage capacitors C1 and C2, the voltage ratio thereof is detected by voltage ratio detection means described later, and whether or not the measurement object 14 is within the set distance range. Is determined.
[0041]
  C5 and C6 are first and second comparison capacitors, respectively, constituting elements of the voltage ratio detection means. These comparison capacitors are connected via the constant current charge amplifiers 30 and 32 simultaneously with the start of charging of the first stage capacitors C1 and C2. C5 and C6 are charged.
  Here, the constant current charge amplifiers 30 and 32 are amplifiers having an amplification factor of 1 and have a function as a buffer. When it is not emitting light, it is stopped.
[0042]
  The first stage capacitors C1 and C2 and the comparison capacitors C5 and C6 increase in proportion to the voltage while the pulsed light continues to be emitted from the light emitting element 12, that is, while the photocurrent flows into the first stage capacitors C1 and C2. When the light emission ends, the charges of the comparison capacitors C5 and C6 are discharged with constant current by the constant current discharge circuits 34 and 36.
  The comparison capacitors C5 and C6 have the same capacity. Specifically, in this example, the comparison capacitors C5 and C6 are each 1000 pF.
[0043]
  On the other hand, the constant current discharge circuits 34 and 36 are set to discharge amounts different from each other.
  Specifically, in FIG. 1, the set distance range when determining that the object 14 is present is X, and when the object 14 is in the position of the set distance range X, the incident position on the light receiving element 18 is a / b = Assuming 3/1, the discharge amount of the constant current discharge circuit 34 is set to be three times that of the constant current discharge circuit 36.
  That is, when the charging voltage of the comparison capacitor C5 is three times as high as the charging voltage of the comparison capacitor C6, the discharge capacities of the constant current discharge circuits 34 and 36 are set so that the discharge ends simultaneously.
[0044]
  Therefore, the photocurrent I on the far side_L1The comparison capacitor C6 on the long-distance side that is charged by the_L2If the discharge is completed earlier than the short-distance comparison capacitor C5 to be charged, it can be determined that the object 14 is within the set distance range X, that is, the object 14 is within the set detection distance range X.
[0045]
  Reference numeral 38 denotes a voltage comparison circuit for monitoring and comparing the voltages of the comparison capacitors C5 and C6. The voltage comparison circuit 38 is configured such that the voltage of the comparison capacitor C6 on the long distance side is compared with the comparison capacitor C5 on the short distance side as described above. When the voltage is quickly returned to the original voltage, that is, when the discharge is completed earlier, a signal is output to turn on the switching transistor 40. Here, a detection signal indicating that the object 14 exists within the set distance range X is output.
[0046]
  As described above, in this example, the constant current charging amplifiers 30 and 32, the comparison capacitors C5 and C6, the constant current discharge circuits 34 and 36, the voltage comparison circuit 38, the switching transistor 40, and the like constitute voltage ratio detection means.
  In the figure, reference numeral 42 denotes a detection distance setting circuit having resistors R3 to R6 for setting the detection distance.
  44 is a distance setting input terminal, and C100 is a bypass capacitor for absorbing line noise.
[0047]
  Next, the operation of the apparatus of this example will be described in detail based on the time chart of FIG.
  FIG. 3A shows a state where the measurement object 14 does not exist. In this case, even if the light emitting element 12 emits pulsed light, no reflected light is incident on the light receiving element 18. Capacitors C1 and C2 only hold a reference voltage and do not cause a voltage increase due to a photocurrent generated by incident reflected light.
  The comparison capacitors C5 and C6 charge the reference voltage of the first stage capacitors C1 and C2, respectively, but do not increase the voltage due to the photocurrent generated by the incidence of the reflected light.
[0048]
  On the other hand, FIG. 3B shows a state when the measurement object 14 is present within the set distance range X. In this case, the reflected light from the object 14 is incident on the light receiving element 18. A photocurrent corresponding to the position is output from both ends of the light receiving element 18. In response, the first stage capacitors C1 and C2 rise in voltage based on their respective photocurrents.
  This voltage increase is continuously performed for the time during which the pulsed light is emitted.
[0049]
  At this time, the voltages of the comparison capacitors C5 and C6 are also increased at the same time, and the constant current charge amplifiers 30 and 32 are stopped from the time when the emission of the pulsed light is stopped, and the comparison capacitors C5 and C6 are discharged by the constant current discharge circuits 34 and 36. Is done.
  At this time, when the discharge of the comparison capacitor C5 and the discharge of the comparison capacitor C6 are completed at the same time, more specifically, when the voltages of the capacitors C5 and C6 simultaneously drop to the original voltage indicated by the broken line in FIG. It can be determined that the object 14 is just within the set distance range X, that is, that a / b is incident on the light receiving element 18 in FIG. If the discharge on the comparison capacitor C6 side ends earlier than this, it can be determined that the measurement object 14 is located within the set distance range X, that is, the measurement object 14 is within the set distance range X. it can.
[0050]
  According to the optical detection device of the present example as described above, the conventional optical detection device shown in FIG. 5, that is, a semiconductor in which the photocurrent from the semiconductor position detection element is converted into a voltage by logarithmic conversion by a semiconductor. The time to charge the stray capacitance of the capacitor component that is parasitic to the circuit connected to the circuit becomes unstable time, and after that, the original voltage ratio detection can be performed for the first time, and the target object can be detected quickly in a short time. Can finish. Thereby, the pulse emission time per one time from the light emitting element can be shortened, and the power consumption can be reduced.
  Therefore, according to this apparatus, a detection apparatus using a dry battery as a power source can be easily configured.
[0051]
  Conventionally, it is difficult to use a 100 V power source for equipment or equipment around water, and therefore it has been desired to configure a detection device using a dry battery as a power source, but detection using a semiconductor position detection element Although it was difficult to configure the device because of the high power consumption, according to the optical detection device of this example, an optical detection device using a dry cell as a power source and using a semiconductor position detection element can be easily configured. Therefore, a great effect is brought about such that the object can be determined and detected accurately and with less power consumption without being affected by the color of the object.
[0052]
  In this example, the voltages of the first and second first stage capacitors (current-voltage conversion capacitors) C1 and C2 are once transferred to the comparison capacitors C5 and C6, and then the comparison capacitors C5 and C6 are discharged. Since the voltage ratio detection is performed by observing the necessary time, the presence or absence of an object within the set distance range can be detected very easily and accurately.
[0053]
  Although the embodiment of the present invention has been described in detail above, this is merely an example.
  For example, in the above example, the voltages of the first stage capacitors C1 and C2 are transferred to the comparison capacitors C5 and C6 and then discharged. However, in some cases, the first stage capacitors C1 and C2 are charged and then switched by the switch means. It is possible to detect whether there is an object within the set distance range by connecting to a constant current discharge circuit and discharging with them, and watching the time until the end of the discharge.The
  SoIn addition, the present invention can be configured in various modifications without departing from the spirit of the present invention.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an optical detection apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a circuit configuration of the optical detection device in FIG. 1;
FIG. 3 is a time chart showing the operation of the detection device of the same embodiment.
FIG. 4 is a diagram illustrating an example of a conventional optical detection device.
FIG. 5 is a view showing an example of a conventional optical detection device different from FIG.
6 is an operation explanatory diagram of a semiconductor position detection element in the optical detection device of FIG. 5;
FIG. 7 is an explanatory diagram of a problem of the optical detection device of FIG.
8 is a diagram showing an example of a conventional optical detection device different from those shown in FIGS. 4 and 5. FIG.
9 is a diagram showing a specific circuit configuration of the optical detection device of FIG. 8. FIG.
[Explanation of symbols]
        10 Optical detector
        12 Light emitting element
        14 Measurement object
        18 Light receiving element
        30, 32 Constant current charge amplifier (buffer)
        34, 36 Constant current discharge circuit
        38 Voltage comparison circuit
        40 switching transistors
        C1, C2 First stage capacitor (current-voltage conversion capacitor)
        C5 and C6 comparison capacitors
        I_L1, I_L2  Photocurrent
        X Set distance range

Claims (4)

(A) a light emitting element that emits pulsed light toward the measurement object;
(B) receiving reflected light from the object and outputting a photocurrent from both ends, and proportionally changing the photocurrent from each end according to the distance from the incident position of the reflected light to each end. A light receiving element comprising a semiconductor position detecting element that decreases or increases;
(C) first and second current-voltage conversion capacitors that convert the photocurrent from each end of the light receiving element into a voltage;
(D) voltage ratio detection means for detecting and comparing the voltage ratios of the first and second current-voltage conversion capacitors, determining the presence or absence of an object within a set distance range, and outputting a detection signal;
The has, and with the voltage ratio detecting means compares the length of discharge time when the constant current discharge by the first and second discharger charges of said first and second current-voltage conversion capacitor An optical detection device for determining the presence or absence of an object within the set distance range. 2. The first and second current-voltage conversion capacitors according to claim 1 , wherein the first and second current-voltage conversion capacitors have the same capacity, and the first and second current-voltage conversion capacitors respectively correspond to the first current-voltage conversion capacitor and the second current-voltage conversion capacitor. The discharge amount ratio of the discharger is a ratio corresponding to a threshold value of the ratio of the distance from the set incident position to each end of the light receiving element, and the reflected light is incident on the set incident position The optical detection device is characterized in that the discharge ends at the same time. 3. The voltage ratio detection means according to claim 1 , wherein the voltage ratio detection means is connected to the first and second comparison capacitors respectively corresponding to the first and second current-voltage conversion capacitors via a buffer at each corresponding voltage. The optical detection device is characterized in that the first and second comparison capacitors are discharged by the first and second dischargers. The optical detection device according to any one of claims 1 to 3 , wherein the optical detection device is an automatic faucet, an automatic washing toilet, a washbasin, an automatic opening / closing toilet seat, a toilet flushing device, automatic lighting, and a user detection device in automatic heating. An optical detection device.

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