JP2012044527A - Pulse modulated photodetector and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse modulated photodetector that prevents a malfunction due to disturbance light.SOLUTION: A pulse modulated photodetector 50 includes a determination level adjustment unit 200 that determines whether an amplification pulse signal S5 synchronizes with a synchronous timing pulse signal S2 or not, and sets a determination level Sth to a value corresponding to the amplification pulse signal S5 if the amplification pulse signal S5 does not synchronize with the synchronous timing pulse signal S2. This can assume the determination level Sth as a determination level with consideration of an impact of the disturbance light during the duration sect_1 when a pulse light L2 is emitting, thus the pulse modulated photodetector 50 that prevents a malfunction due to disturbance light can be provided.

Description

  The present invention relates to a pulse modulation type detection apparatus and an electronic device that emit light pulse-modulated from a light emitting element to detect the presence or absence of an object.

  In electronic devices such as copying machines and printers such as FA and OA devices, and amusement devices such as game machines, it may be necessary to detect the presence or absence of objects such as recording paper, coins and balls in a predetermined path. For the detection of the presence / absence of such an object, a light detection device that detects the presence / absence of an object using light is preferably used because it is a non-contact type with respect to the object.

  FIG. 13 is a block diagram of a conventional 100. The pulse modulation type photodetector 100 includes a constant voltage circuit 101, a power supply terminal 102, a GND terminal 103, an oscillation circuit 104, a synchronization timing circuit 105, a light emitting element driving circuit 106, a light emitting element 107, a light receiving element 108, an amplifier 109, and a comparator 110. A signal processing circuit 111, an output circuit 112, an output terminal 113, and a power source 115. The load 114 has one end connected to the power supply terminal 102 and the other end connected to the output terminal 113. The operation of the pulse modulation type photo detector 100 will be described below.

  The positive terminal of the power supply 115 is connected to the input terminal of the constant voltage circuit 101 via the power supply terminal 102. The negative terminal of the power supply 115 is connected to the GND terminal of the constant voltage circuit 101 via the GND terminal 103. As a result, the constant voltage circuit 101 generates the constant voltage V using the power source 115 and supplies the constant voltage V to each circuit included in the pulse modulation type photodetection device 100.

  In the pulse modulation type photodetection device 100, the basic clock (CLK) signal S101 generated by the oscillation circuit 104 is modulated by the synchronization timing circuit 105 into the synchronization timing pulse signal S102. The light emitting element driving circuit 106 outputs the light emitting pulse signal S103 to the light emitting element 107 when the synchronization timing pulse signal S102 transmitted from the synchronization timing circuit 105 to the light emitting element driving circuit 106 is Hi. The light emitting element 107 projects pulse-modulated pulsed light L2 toward a predetermined position based on the light emission pulse signal S103 input from the light emitting element driving circuit 106.

  Consider a case where the pulse modulation type photodetecting device 100 detects the presence or absence of an object B passing in the + Y direction at the predetermined position a distance a from the light emitting element 107 and the light receiving element 108 in the + X direction. The pulsed light L2 is projected from the light emitting element 107 to the predetermined position.

  First, since the pulsed light L2 is not reflected by the object B before the object B passes the predetermined position, the reflected light of the pulsed light L2 is not incident on the light receiving element 108.

  Next, when the object B passes through the predetermined position and crosses the pulsed light L2, the pulsed light L2 is reflected by the object B, and the reflected light L3 enters the light receiving element 108.

  As described above, the pulse modulation type photodetection device 100 that detects the presence or absence of the object B passing through the predetermined position depending on whether or not the reflected light L3 from the object B is received is provided by the reflection type pulse modulation type photodetection. Referred to as a device.

  Therefore, if there is no disturbance light or the like in the surroundings, the presence or absence of the reflected light L3 incident on the light receiving element 108 is switched depending on the presence or absence of the object B crossing the pulsed light L2. The reflected light L3 incident on the light receiving element 108 is photoelectrically converted by the light receiving element 108 to obtain a light receiving pulse signal S104.

  The received light pulse signal S104 undergoes current-voltage conversion and amplification by the amplifier 109 to become an amplified pulse signal S105. The amplified pulse signal S105 input to one input terminal (for example, a positive terminal) of the comparator 110 is compared with the determination level Sth input to the other input terminal (for example, the negative terminal) of the comparator 110, and the waveform is shaped. It is output as a comparator output pulse signal S106.

  That is, the comparator 110 outputs the comparator output pulse signal S106 at a timing when the amplified pulse signal S105 generated by amplifying the received light pulse signal S104 exceeds a preset determination level Sth.

  The comparator output pulse signal S106 is compared with the synchronization timing pulse signal S102 in the signal processing circuit 111. Thus, after confirming that the reflected light L3 incident on the light receiving element 108 is synchronized with the pulsed light L2 projected from the light emitting element 107 to the predetermined position, a signal is output to the comparator output pulse signal S106. Processing is performed. The comparator output pulse signal S106 after the signal processing is output to the output circuit 112 as a signal processing circuit output signal S107. The level of the signal processing circuit output signal S107 becomes Hi or Low depending on the presence / absence of the object B passing through the predetermined position. For example, the signal processing circuit output signal S107 becomes Hi when the object B passes the predetermined position, and becomes Low when the object B does not pass the predetermined position.

  On the other hand, disturbance light that is not synchronized with the synchronization timing pulse is also photoelectrically converted by the light receiving element 108 and output as a light reception pulse signal S104 '. The received light pulse signal S104 'undergoes current-voltage conversion and amplification by the amplifier 109 to become an amplified pulse signal S105'.

  When the amplified pulse signal S105 ′ input to one input terminal of the comparator 110 exceeds the determination level Sth, the comparator output pulse signal S106 ′ is output from the comparator 110 to the signal processing circuit 111.

  The signal processing circuit 111 compares the comparator output pulse signal S106 'with the synchronization timing pulse signal S102. As a result, the signal processing circuit 111 determines that the comparator output pulse signal S106 ′ is not synchronized (asynchronous) with the synchronization timing pulse signal S102, and then cancels the processing for detecting the presence or absence of an object. Prevents malfunction. The process of detecting the presence or absence of an object is stopped by stopping the signal processing of the comparator output pulse signal S106 ', fixing the signal processing circuit output signal S107, or the like.

As in the conventional pulse modulation type photodetecting device 100 of FIG. 13, as a sensor for preventing malfunction, Patent Document 1 discloses a situation in which noise pulses appear periodically and the generation timing thereof overlaps with the sampling timing. Even if it exists, the radiation pulse interposition type sensor incorporating the malfunction prevention measure which functions effectively is indicated.

  Similarly to the conventional pulse modulation type photodetecting device 100 of FIG. 13, Patent Document 2 discloses that a noise component included in a signal is suppressed as a countermeasure against a noise component that is not a desired signal component. A photoelectric sensor is disclosed.

  Further, as a pulse modulation type photo detection device similar to the conventional pulse modulation type photo detection device 100 of FIG. 13, Patent Document 3 discloses a pulse modulation type photo detection device with reduced current consumption.

JP 2002-368595 A (published on December 20, 2002) JP 2007-40720 A (published February 15, 2007) JP 2007-129364 A (published May 24, 2007)

  As described above, the conventional pulse modulation type photodetection device 100 processes only the light synchronized with the synchronization timing pulse signal S102 and does not process the light not synchronized with the synchronization timing pulse signal S102. It prevents malfunction.

  However, in the pulse modulation type photodetecting device 100 of FIG. 13, when both minute reflected light and disturbance light from an object not to be detected exist and these lights are mixedly input to the light receiving element 108. There is a possibility of malfunction.

  The concept of the malfunction is shown in FIGS. FIG. 14 is a block diagram showing a part of an electronic device 121 in which the conventional pulse modulation type photodetecting device 100 of FIG. FIG. 15 is a waveform diagram showing respective waveforms at the time of normal operation and malfunction in the electronic apparatus 121 including the conventional pulse modulation type photodetection device 100.

  Normally, when there is no object to be detected, no light is incident on the light receiving element 108. Therefore, the amplifier 109 does not output the amplified pulse signal S105, and the comparator 110 does not output the comparator output pulse signal S106.

  Here, a minute reflected light L3 ′ from other than the object B to be detected, for example, reflected light (including stray light components) in the pulse modulation type photo detection device 100, or the pulse modulation type photo detection device 100 is installed. Consider a case where there is reflected light from the housing 120 of the electronic device 121 to be used. In this case, the reflected light L3 'that does not reach the determination level Sth is incident on the light receiving element 108 at the timing when the synchronization timing pulse signal S102 becomes Hi.

  Further, consider a case where disturbance light L <b> 3 ″, for example, light from the inverter fluorescent lamp 122 is input to the light receiving element 108. In this case, the superimposed light L3 ′ + L3 ″ in which the disturbance light L3 ″ is superimposed on the reflected light L3 ′ from the housing 120 or the like exceeds the determination level Sth at the timing when the synchronization timing pulse signal S102 becomes Hi. For this reason, the comparator 110 generates the comparator output pulse signal S106 ′ at the timing when the synchronization timing pulse signal S102 becomes Hi, and causes a malfunction that is erroneously determined as the presence of an object even though there is no target to be detected. It becomes.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a pulse modulation type photodetector that prevents malfunction due to disturbance light.

  In order to solve the above-described problems, the pulse modulation type photodetecting device of the present invention includes a light emitting element that emits, in a predetermined space, pulse light synchronized with a pulse signal obtained by modulating a reference clock signal, and the predetermined space. A light-receiving element that receives the external light including the pulsed light reflected by the detection target passing through and generates a current signal according to the received external light, a voltage signal obtained by converting the current signal into a current voltage, and a predetermined signal When the voltage signal is higher than the first reference value, it is detected that there is the detection target passing through the predetermined space, and the voltage signal is detected by the first reference value. A pulse modulation type photo-detecting device comprising: a detecting means for detecting that there is no detection target passing through the predetermined space when the voltage signal is equal to or less than a value; Or And, when the voltage signal and the pulse signal is determined not to be synchronized, the first reference value, characterized in that it comprises a reference value setting means for setting a value corresponding to the voltage signal.

  According to the invention, the reference value setting means determines whether or not the voltage signal and the pulse signal are synchronized, and when determining that the voltage signal and the pulse signal are not synchronized, The first reference value is set to a value corresponding to the voltage signal.

  Thereby, in the period when the pulsed light is emitted, the first reference value can be a reference value that takes into account the influence of light (disturbance light) that is not synchronized with the pulse signal. The detecting means can detect the presence / absence of the detection target passing through the predetermined space using the adjusted reference value in consideration of the influence of disturbance light.

  Therefore, it is possible to provide a pulse modulation type photodetector that prevents malfunction due to disturbance light.

  In the pulse modulation type photodetection device, the reference value setting means further receives the voltage signal, and when the voltage signal is higher than a predetermined second reference value, the voltage signal is higher than a predetermined second reference value. A first comparison that outputs a first signal indicating high and outputs a second signal indicating that the voltage signal is less than or equal to a predetermined second reference value when the voltage signal is less than or equal to the second reference value. Only when the pulsed light is emitted, the signal switching means for conducting the signal output from the first comparison means, and the signal conducted by the signal switching means is the first signal. Reference value increasing means for increasing one reference value by a first predetermined value and not increasing the first reference value when the signal conducted by the signal switching means is the second signal may be provided.

  Since the first reference value can be increased by the first predetermined value by the reference value increasing means, the first reference value can be set to a determination level in which the influence of disturbance light is considered.

  Therefore, it is possible to provide a pulse modulation type photodetector that prevents malfunction due to disturbance light.

In the pulse modulation type photodetection device, the reference value setting means further includes maximum value holding means for holding the maximum value of the voltage signal, and when the pulsed light is emitted, the first reference value is You may make it increase only the 2nd predetermined value according to the maximum value which the said maximum value holding means hold | maintains.
Since the second predetermined value linearly changes in accordance with the maximum value, the first reference value can be adjusted with high accuracy.

  In the pulse modulation type photodetecting device, the reference value setting means may further comprise an integrating means for integrating the voltage signal and outputting the integrated voltage signal to the first comparing means.

  As a result, when the voltage signal is a signal generated by amplifying periodic noise, the level of the output signal of the integrating means increases as time elapses. Only periodic disturbance light such as inverter light can be detected without reacting to light.

  In the pulse modulation type photodetection device, the integrating means further has a capacitor whose one end is connected to the output of the integrating means and whose other end is electrically grounded, the voltage signal, and arbitrarily set. A comparator that is a second comparison unit that outputs a digital signal corresponding to a comparison result between the voltage signal and the reference voltage, and the capacitance when the voltage signal is greater than the reference voltage. And a second current source having a current value smaller than that of the first current source for discharging the capacitor when the voltage signal is equal to or lower than the reference voltage. .

  By performing digital output using a comparator as the second comparison means, the amplitude of the output signal of the integration circuit is approximately the same as the reference voltage, and is larger than the amplitude of the disturbance light amplification signal.

  The capacitance value of the capacitor depends on the amplitude of the output signal of the integration circuit, and can be reduced as the amplitude of the output signal of the integration circuit is increased. The capacitance value can be made smaller by inputting the reference voltage to the inverting input terminal of the second comparing means and setting the amplitude of the output signal of the integrating circuit to the same amplitude as the reference voltage. As the capacitance value is smaller, the area of the capacitance can be reduced, so that the cost of the pulse modulation type photodetection device can be reduced.

  In any one of the pulse modulation type photodetection devices, the detection means further generates a comparison result signal indicating a result of comparing the voltage signal and the first reference value, and the comparison result signal Is a value that is switched according to the magnitude relationship between the voltage signal and the first reference value, and when a plurality of pulses are generated in the comparison result signal during the period in which the pulse light is emitted. , It may be determined that it is erroneously detected.

  In any one of the pulse modulation type photo detectors, when the presence or absence of disturbance light does not exist when detecting the presence or absence of the detection target passing through the predetermined space, the pulse light is emitted during the period. A single pulse is generated. For this reason, if the signal generated by comparing the voltage signal with the first reference value includes a plurality of pulses, it is erroneously detected by disturbance light during the period in which the pulsed light is emitted. The detection means determines that the operation of detecting the presence / absence of the detection target passing through the predetermined space is stopped, thereby preventing a malfunction due to ambient light.

  In any one of the pulse modulation type photodetection devices, the detection means further generates a comparison result signal indicating a result of comparing the voltage signal and the first reference value, and the comparison result signal The value is switched according to the magnitude relationship between the voltage signal and the first reference value. When the value of the comparison result signal is switched during the period when the pulsed light is emitted, a false detection is performed. It may be determined that

  In any one of the pulse modulation type photodetection devices, in a state where no disturbance light exists, when a predetermined delay time elapses after the period in which the pulsed light is emitted, the amplified signal and the determination level are set. The level of the signal generated by comparison is switched.

  Therefore, if the value of the comparison result signal is switched during the period in which the pulsed light is emitted, the detection means determines that the pulsed light is erroneously detected during the period in which the pulsed light is emitted, By stopping the operation of detecting the presence / absence of the detection target passing through a predetermined space, it is possible to prevent malfunction due to ambient light.

  Since the electronic apparatus of the present invention includes any one of the above-described pulse modulation type photodetection devices, it is possible to prevent malfunction due to disturbance light.

  As described above, the pulse modulation type photo detection device of the present invention determines whether or not the voltage signal and the pulse signal are synchronized, and when it is determined that the voltage signal and the pulse signal are not synchronized, Reference value setting means for setting the first reference value to a value corresponding to the voltage signal is provided.

  Therefore, there is an effect of providing a pulse modulation type photo detection device that prevents malfunction due to disturbance light.

1 is a block diagram of a pulse modulation type photodetector according to an embodiment of the present invention. 1 is a block diagram of a pulse modulation type photodetector according to an embodiment of the present invention. It is a wave form diagram for demonstrating operation | movement of the pulse modulation type photon detection apparatus which concerns on the Example of this invention. It is a block diagram of a pulse modulation type photodetection device according to another embodiment of the present invention. It is a wave form diagram for demonstrating operation | movement of the pulse modulation type | mold photodetector which concerns on the other Example of this invention. It is a block diagram of a pulse modulation type photodetection device concerning another example of the present invention. It is a wave form diagram for demonstrating operation | movement of the pulse modulation type photon detection apparatus which concerns on another Example of this invention. It is a block diagram of a pulse modulation type photodetection device concerning a modification of the present invention. It is a wave form diagram for demonstrating operation | movement of the pulse modulation type photon detection apparatus which concerns on the modification of this invention. It is a block diagram of a pulse modulation type photodetection device concerning another example of the present invention. It is a wave form diagram for demonstrating operation | movement of the pulse modulation type photon detection apparatus which concerns on another Example of this invention. It is a wave form diagram explaining the concept of the countermeasure against malfunctioning in the pulse modulation type photon detector which concerns on embodiment of this invention. It is a block diagram of a conventional pulse modulation type photodetection device. It is a block diagram which shows a part of electronic device which accommodated the conventional pulse modulation type | mold photodetector in FIG. 13 in the housing | casing. It is a wave form chart which shows each waveform at the time of a normal operation and a malfunctioning in electronic equipment provided with a pulse modulation type photodetection device.

  An embodiment of the present invention will be described below with reference to FIGS. First, the concept of countermeasures against malfunctions in the pulse modulation type photodetector according to the present embodiment will be described with reference to the waveform diagram of FIG.

[Countermeasures for malfunction]
FIG. 12 is a waveform diagram for explaining the concept of countermeasures against malfunctions in the pulse modulation type photodetector according to the present embodiment. In FIG. 12, the reference numerals in this embodiment are appropriately used. Each of the reflected light L3 ′ and the disturbance light L3 ″ is the light described in [Problems to be Solved by the Invention]. The disturbance light is light that is not synchronized with a synchronization timing pulse signal S2 described later.

  First, in the first countermeasure, a new disturbance light determination is performed in a period sect_2 (period in which pulse light is not emitted) other than a period sect_1 (period in which pulse light is emitted) in which the synchronization timing pulse signal S2 is Hi. The level SthN is used to determine the presence or absence of ambient light. If it is determined that ambient light is present, the determination level Sth is shifted by a certain value during the period sect_1 to obtain the determination level Sth ′. As a result, the determination level Sth can be set to the determination level Sth ′ in which the influence of disturbance light is taken into account. Therefore, the comparator 10 uses the adjusted determination level Sth ′ in which the influence of disturbance light is taken into account, The presence or absence of the object B can be detected.

  Therefore, it is possible to provide a pulse modulation type photodetector that prevents malfunction due to disturbance light.

  Next, as a second countermeasure, the level of disturbance light is measured in a period sect_2 other than the period sct_1 in which the synchronization timing pulse signal S2 is Hi. Then, the determination level Sth is shifted to the determination level Sth ′ in the period sect_1 according to the measured level of ambient light. As a result, similarly to the first countermeasure, it is possible to provide a pulse modulation type photodetector that prevents malfunction due to disturbance light.

  Next, as a third countermeasure, the signal processing circuit 11 counts the number of pulses of the comparator output pulse signal S6 (comparison result signal) in the period sect_1. When a plurality of pulses of the comparator output pulse signal S6, which should be a single pulse in the period sect_1, are generated, it is determined that a malfunction due to disturbance light has occurred.

  Here, the basic configuration of the pulse modulation type photodetecting device according to the present embodiment will be described with reference to FIG.

[Basic configuration of pulse modulation type photodetection device]
FIG. 1 is a block diagram of a pulse modulation type photodetector 50 according to the present embodiment. The pulse modulation type photodetector 50 includes a constant voltage circuit 1, a power supply terminal 2, a GND terminal 3, an oscillation circuit 4, a synchronization timing circuit 5, a light emitting element driving circuit 6, a light emitting element 7, a light receiving element 8, an amplifier 9, and a comparator 10. (Detection means), a signal processing circuit 11 (detection means), an output circuit 12, an output terminal 13, a power supply 15, and a determination level adjustment unit 200 (reference value setting means). The load 14 has one end connected to the power supply terminal 2 and the other end connected to the output terminal 13. First, the operation of the part other than the determination level adjustment unit 200 of the pulse modulation type photodetecting device 50 will be described below.

  The positive terminal of the power supply 15 is connected to the input terminal of the constant voltage circuit 1 via the power supply terminal 2. The negative terminal of the power supply 15 is connected to the GND terminal of the constant voltage circuit 1 through the GND terminal 3. Thereby, the constant voltage circuit 1 generates the constant voltage V using the power supply 15 and supplies the constant voltage V to each circuit provided in the pulse modulation type photodetecting device 50.

  In the pulse modulation type photo detector 50, the basic clock (CLK) signal S 1 (reference clock signal) generated by the oscillation circuit 4 is modulated by the synchronization timing circuit 5 into a synchronization timing pulse signal S 2 (pulse signal). The The light emitting element driving circuit 6 outputs the light emitting pulse signal S3 to the light emitting element 7 when the synchronization timing pulse signal S2 transmitted from the synchronization timing circuit 5 to the light emitting element driving circuit 6 is Hi (referred to as a period stt_1). To do. The light emitting element 7 projects pulse-modulated pulsed light L2 toward a predetermined position based on the light emission pulse signal S3 input from the light emitting element driving circuit 6.

  Presence / absence of an object B (a target to be detected that passes through a predetermined space) passing in the + Y direction through the predetermined position a distance a in the + X direction from the light emitting element 7 and the light receiving element 8 Consider the case of detecting. The pulsed light L2 is projected from the light emitting element 7 to the predetermined position.

  First, since the pulsed light L2 is not reflected by the object B before the object B passes the predetermined position, the reflected light of the pulsed light L2 is not incident on the light receiving element 8.

  Next, when the object B passes through the predetermined position and crosses the pulsed light L2, the pulsed light L2 is reflected by the object B, and the reflected light L3 enters the light receiving element 8.

  As described above, the pulse modulation type photodetection device 50 that detects the presence or absence of the object B passing through the predetermined position depending on whether or not the reflected light L3 from the object B is received is a reflection type pulse modulation type photodetection. Referred to as a device.

  Accordingly, if there is no disturbance light or the like in the surroundings, the presence or absence of the reflected light L3 incident on the light receiving element 8 is switched depending on the presence or absence of the object B crossing the pulsed light L2. The reflected light L3 incident on the light receiving element 8 is photoelectrically converted by the light receiving element 8 to obtain a light reception pulse signal S4 (current signal) which is a current signal.

  The received light pulse signal S4 undergoes current-voltage conversion and amplification by the amplifier 9, and becomes an amplified pulse signal S5 (voltage signal) which is a voltage signal. The amplified pulse signal S5 input to one input terminal (for example, a positive terminal) of the comparator 10 and the determination level Sth (predetermined first reference value) input to the other input terminal (for example, the negative terminal) of the comparator 10 The waveform is compared, the waveform is shaped, and output as a comparator output pulse signal S6.

  That is, the comparator 10 outputs the comparator output pulse signal S6 at a timing when the amplified pulse signal S5 generated by amplifying the light reception pulse signal S4 exceeds a preset determination level Sth.

  The comparator output pulse signal S6 is compared with the synchronization timing pulse signal S2 in the signal processing circuit 11. Thereby, after confirming that the reflected light L3 incident on the light receiving element 8 is synchronized with the pulsed light L2 projected from the light emitting element 7 to the predetermined position, a signal is output to the comparator output pulse signal S6. Processing is performed. The comparator output pulse signal S6 after the signal processing is output to the output circuit 12 as a signal processing circuit output signal S7. The level of the signal processing circuit output signal S7 becomes Hi or Low depending on the presence / absence of the object B passing through the predetermined position. For example, the signal processing circuit output signal S7 becomes Hi when the object B passes the predetermined position, and becomes Low when the object B does not pass the predetermined position.

  On the other hand, disturbance light that is not synchronized with the synchronization timing pulse is also photoelectrically converted by the light receiving element 8 and output as a light reception pulse signal S4 '. The received light pulse signal S4 'undergoes current-voltage conversion and amplification by the amplifier 9 to become an amplified pulse signal S5'.

  When the amplified pulse signal S5 'input to one input terminal of the comparator 10 exceeds the determination level Sth, the comparator output pulse signal S6' is output from the comparator 10 to the signal processing circuit 111.

  The signal processing circuit 11 compares the comparator output pulse signal S6 'with the synchronization timing pulse signal S2. As a result, the signal processing circuit 11 determines that the comparator output pulse signal S6 ′ is not synchronized (asynchronous) with the synchronization timing pulse signal S2, and then cancels the processing for detecting the presence or absence of an object, and the disturbance light Prevents malfunction. The process of detecting the presence or absence of an object is stopped by stopping the signal processing of the comparator output pulse signal S6 ', fixing the signal processing circuit output signal S7, or the like.

(Determination level adjustment unit 200)
As described above, the pulse modulation type photodetector 50 of the first embodiment is added with the determination level adjustment unit 200 that is not provided in the conventional pulse modulation type photodetector 100 of FIG.

  The determination level adjustment unit 200 determines whether or not the amplified pulse signal S5 and the synchronization timing pulse signal S2 are synchronized, and determines that the amplified pulse signal S5 and the synchronization timing pulse signal S2 are not synchronized. The level Sth is set to a determination level Sth ′ corresponding to the amplified pulse signal S5.

  Thereby, in the period sect_1 in which the pulsed light L2 is emitted, the determination level Sth can be set to the determination level Sth ′ in which the influence of disturbance light is taken into account. Therefore, the detection unit takes into consideration the influence of disturbance light. The presence or absence of the object B passing through the predetermined space can be detected using the adjusted determination level Sth ′.

  Therefore, it is possible to provide a pulse modulation type photodetector that prevents malfunction due to disturbance light.

  The determination level adjustment unit 200 receives the amplified pulse signal S5 and the synchronization timing pulse signal S2. Next, the determination level Sth is adjusted by the determination level adjustment signal S200 in accordance with the measurement result of the amplified pulse signal S5 in the period sect_2 other than the period sect_1 in which the synchronization timing pulse signal S2 is Hi.

  If the period sect_2 can be specified by another signal different from the synchronization timing pulse signal S2, the other signal can be used instead of the synchronization timing pulse signal S2. Further, if the level of disturbance light can be measured by a signal other than the amplified pulse signal S5, for example, a signal such as the received light pulse signal S4 or the comparator output pulse signal S6, the received light pulse signal S4 instead of the amplified pulse signal S5. It is also possible to use a signal such as a comparator output pulse signal S6.

  As described above, the pulse modulation type photodetector 50 according to the present embodiment includes the light emitting element 7 that emits the pulsed light L2 synchronized with the synchronization timing pulse signal S2 obtained by modulating the basic clock signal S1 to a predetermined space, and A light receiving element 8 that receives external light including the pulsed light L3 reflected by the object B passing through the predetermined space and generates a light receiving pulse signal S4 corresponding to the received external light, and a light receiving pulse signal S4 as a current The voltage-converted amplified pulse signal S5 is compared with the determination level Sth. When the amplified pulse signal S5 is higher than the determination level Sth, it is detected that there is an object B passing through the predetermined space, and the amplified pulse signal S5 is A pulse including a comparator 10 and a signal processing circuit 11 that detects that there is no object B passing through the predetermined space when the determination level is Sth or less. When the modulated light detection device determines whether the amplified pulse signal S5 and the synchronization timing pulse signal S2 are synchronized, and determines that the amplified pulse signal S5 and the synchronization timing pulse signal S2 are not synchronized The determination level adjustment unit 200 sets the determination level Sth to a value corresponding to the amplified pulse signal S5.

[Embodiment 1 of Pulse Modulation Photodetector]
Example 1 of the pulse modulation type photodetecting device according to the present embodiment will be described with reference to FIGS. The configuration other than that described in the first embodiment is the same as the above [Basic Configuration of Pulse Modulation Photodetector]. Further, for convenience of explanation, members having the same functions as those shown in the drawing of [Basic structure of pulse modulation type photodetection device] are given the same reference numerals, and explanation thereof is omitted.

  FIG. 2 is a block diagram of the pulse modulation type photodetector 51 according to the first embodiment. FIG. 3 is a waveform diagram for explaining the operation of the pulse modulation type photodetecting device 51 according to the first embodiment.

  The pulse modulation type photo detector 51 is a pulse modulation type photo detector described in more detail with respect to the determination level adjustment unit 200 of the pulse modulation type photo detector 50 of FIG.

  2 includes a comparator 201 (first comparison unit), a storage unit 202 (storage unit), a switch SW203 (signal switching unit), a switch SW116 (reference value increasing unit), and a determination. And a power supply that outputs a level shift voltage Sth2 (first predetermined value).

  The comparator 201 compares the amplified pulse signal S5 with the disturbance light determination level SthN (predetermined second reference value), and outputs a noise detection signal S201 (Hi in FIG. 3) when the condition of S5> SthN is satisfied.

  If the noise detection signal S201 is output even once, the storage unit 202 stores the noise detection signal S201 and outputs and holds the noise determination signal S202 (corresponding to the determination level adjustment signal S200) (Hi in FIG. 3). The switch SW203 is controlled to be turned ON / OFF by the synchronization timing pulse signal S2, and is turned ON during a period sto_1 in which the synchronization timing pulse signal S2 is Hi. As a result, the switch SW116 is controlled to be turned ON / OFF by the noise determination signal S202.

  If the noise determination signal S202 is output in the period sect_1 (if it is Hi as shown in FIG. 3), the switch SW116 is turned off. As a result, the determination level is changed (shifted) from Sth to Sth ′ = Sth + Sth2.

  Note that if the noise detection signal S201 is not output in the period sect_1 (if Low), and the switch SW116 is ON in the period sect_2. Therefore, the determination level at the other input terminal of the comparator 10 is Sth.

  When the period sect_1 ends, the storage unit 202 is reset by the synchronization timing pulse signal S2, and the storage unit 202 stops outputting the noise determination signal S202 (in FIG. 3, the noise determination signal S202 becomes Low by resetting). ) Further, since the period sect_1 has ended, the switch SW203 is turned off and the switch SW116 is turned on.

  If the amplified pulse signal S5 and the ambient light determination level SthN can be compared and the determination level Sth can be adjusted in the period stt_1, the determination level adjustment unit 200, the switch SW116, and the power supply that outputs the determination level shift voltage Sth2 The configuration is not limited to the configuration of the first embodiment.

  As described above, in the pulse modulation type photodetecting device 51 according to the first embodiment, the determination level adjusting unit 200 further receives the amplified pulse signal S5, and the amplified pulse signal S5 is higher than the disturbance light determination level SthN. The first signal indicating that the amplified pulse signal S5 is higher than the disturbance light determination level SthN is output, and when the amplified pulse signal S5 is equal to or less than the disturbance light determination level SthN, the amplified pulse signal S5 is equal to or less than the disturbance light determination level SthN The comparator 201 that outputs a second signal indicating that it is present, the switch SW203 that conducts the signal output from the comparator 201 only when the pulsed light L2 is emitted, and the signal that is conducted by the switch SW203 is the first signal. At some time, the determination level Sth is increased by the determination level shift voltage Sth2, and the switch SW When 03 were passed signal is the second signal, and a reference value increasing unit that does not increase the determination level Sth.

  Since the determination level Sth can be increased by the determination level shift voltage Sth2 by the reference value increasing means, the determination level Sth can be set to the determination level Sth ′ that takes into account the influence of ambient light.

  Therefore, it is possible to provide a pulse modulation type photodetector that prevents malfunction due to disturbance light.

[Embodiment 2 of Pulse Modulation Type Photodetector]
Example 2 of the pulse modulation type photodetecting device according to this embodiment will be described with reference to FIGS. Configurations other than those described in the second embodiment are the same as those in [Basic configuration of pulse modulation type photodetection device] and the first embodiment. Further, for convenience of explanation, members having the same functions as those shown in the above [Basic structure of pulse modulation type photodetection device] and the drawings of the first embodiment are denoted by the same reference numerals and description thereof is omitted. To do.

  FIG. 4 is a block diagram of the pulse modulation type photodetector 52 according to the second embodiment. FIG. 5 is a waveform diagram for explaining the operation of the pulse modulation type photodetecting device 52 according to the second embodiment.

  The determination level adjustment unit 200 in FIG. 4 is a peak hold circuit 203 (maximum value holding means). The peak hold circuit 203 includes an amplifier 204, a diode 205, a capacitor 206, a power source 207 that outputs a reference voltage Vref, switches SW206, SW207, and SW208, and a power source that outputs a variable determination level shift voltage Sth2 ′ (second predetermined value). It has.

  The switch SW206 is turned on except for a certain time T described later in the period sect_2. ON / OFF of the switch SW206 is controlled by a peak hold control signal S250 output from the synchronization timing circuit 5. The peak hold circuit 203 holds the peak voltage of the amplified pulse signal S5 in the period sect_2.

  The peak-held voltage is output as a peak hold voltage signal S203 (corresponding to the determination level adjustment signal S200), and the switch SW208 is turned on in the period sect_1. Thus, the power source that outputs the variable determination level shift voltage Sth2 'is controlled by the peak hold voltage signal S203, and the determination level is changed (shifted) from Sth to Sth' = Sth + Sth2 '.

  At this time, the variable determination level shift voltage Sth2 'changes linearly with respect to the peak hold voltage signal S203, that is, the peak value of the disturbance light. As a result, the determination level Sth ′ can be adjusted with higher accuracy than the pulse modulation type photodetection device 51 of the first embodiment.

  When the period sect_1 ends, the switch SW208 is turned OFF, the variable determination level shift voltage Sth2 'becomes 0, and the determination level changes from Sth' to Sth.

  At the same time, after the period sect_1 ends, the switch SW207 is turned on for a predetermined time T by the capacitive discharge signal S251 output from the synchronous timing circuit 5. As a result, the capacitor 206 is discharged and the peak hold voltage signal S203 is set to Low.

  The fixed time T is included in the period sect_2, but the switch SW206 maintains OFF in the fixed time T, similarly to the period sect_1. As soon as the switch SW207 is turned off and the switch SW206 is turned on after the discharge of the capacitor 206, the peak hold circuit 203 resumes holding the peak voltage of the amplified pulse signal S5.

  Note that the configuration of the power supply that outputs the determination level adjustment unit 200 and the variable determination level shift voltage Sth2 ′ if the peak value of disturbance light can be acquired and the variable determination level shift voltage Sth2 ′ can be controlled is described in this embodiment. The configuration is not limited to Example 2.

  As described above, in the pulse modulation type photodetecting device 52 according to the second embodiment, the determination level adjusting unit 200 further includes the peak hold circuit 203 that holds the maximum value of the amplified pulse signal S5, and the pulsed light L2 is When light is emitted, the determination level Sth may be increased by the variable determination level shift voltage Sth2 ′ corresponding to the maximum value held by the peak hold circuit 203. Since the variable determination level shift voltage Sth2 'varies linearly according to the peak value, the determination level can be adjusted with high accuracy.

[Embodiment 3 of Pulse Modulation Photodetector]
Example 3 of the pulse modulation type photodetecting device according to this embodiment will be described with reference to FIGS. The configurations other than those described in the third embodiment are the same as those in the above [Basic configuration of pulse modulation type photodetection device] and the first and second embodiments. For convenience of explanation, members having the same functions as the members shown in the drawings of the above [Basic structure of pulse modulation type photodetection device] and the first and second embodiments are given the same reference numerals, and the explanation thereof is omitted. Is omitted.

  FIG. 6 is a block diagram of the pulse modulation type photodetecting device 53 according to the third embodiment. FIG. 7 is a waveform diagram for explaining the operation of the pulse modulation type photodetecting device 53 according to the third embodiment.

  6 includes an integration circuit 208 (integration means), a comparator 201, a storage unit 210, a power source that outputs a disturbance light determination level SthN, a switch SW209, a switch SW116, and a determination level shift voltage. And a power supply for outputting Sth2.

  The integrating circuit 208 further includes an amplifier 211, current sources 212 and 213 (first current source and second current source), a capacitor 214, and a switch SW210.

  The integrating circuit 208 integrates and outputs the amplified pulse signal S5. At this time, the amplified pulse signal S5 is input to the non-inverting input terminal (+) of the amplifier 211, and the integration circuit output signal S204 is input to the inverting input terminal (−) of the amplifier 211. Thus, when S5> S204, the current source 212 charges the capacitor 214, and when S5 <S204, the current source 213 discharges the capacitor 214.

  Here, when the current value of the current source 212 is set to be larger than the current value of the current source 213, and the amplified pulse signal S5 is a signal generated by amplifying periodic noise, the integration circuit The level of the output signal S204 increases as time passes.

  The comparator 201 compares the integration circuit output signal S204 with the disturbance light determination level SthN and outputs a noise detection signal S205 (in FIG. 7, it is Hi).

  If the noise detection signal S205 is output even once, the storage unit 210 stores it and outputs and holds the noise determination signal S206 (corresponding to the determination level adjustment signal S200) (Hi in FIG. 7). The switch SW209 is controlled to be turned on and off by the synchronization timing pulse signal S2, and is turned on during a period stt_1 in which the synchronization timing pulse signal S2 is Hi. As a result, the switch SW116 is controlled to be turned ON / OFF by the noise determination signal S206.

  If the noise detection signal S205 is output in the period sect_1 (if it is Hi as shown in FIG. 7), the switch SW116 is turned off. As a result, the determination level is changed (shifted) from Sth to Sth ′ = Sth + Sth2.

  If the noise detection signal S205 is not output in the period sect_1 (if it is Low), and the switch SW116 is ON in the period sect_2. Therefore, the determination level at the other input terminal of the comparator 10 is Sth.

  When the period sect_1 ends, the storage unit 210 is reset by the synchronization timing pulse signal S2, and the storage unit 210 stops outputting the noise determination signal S206 (in FIG. 7, the noise determination signal S206 becomes Low due to the reset). ) Further, since the period sect_1 has ended, the switch SW209 is turned off and the switch SW116 is turned on.

  In addition, after the end of the period sect_1, the switch SW210 is turned on for a predetermined time T ′ by the capacitive discharge signal S252 output from the synchronous timing circuit 5. As a result, the capacitor 214 is discharged and the integration circuit output signal S204 is lowered. After the discharge of the capacitor 214, as soon as the switch SW210 is turned off, the integration circuit 208 resumes the integration operation.

  Since the pulse modulation type photodetector 53 according to the third embodiment uses the integration circuit 208, the following advantages are obtained with respect to the pulse modulation type photodetector 51 according to the first embodiment. That is, there is an advantage that only periodic disturbance light such as inverter light can be detected without reacting to sudden single disturbance light.

  Note that if the determination level Sth can be adjusted in the period sect_1 by integrating the amplified pulse signal S5 and comparing with the disturbance light determination level SthN, the determination level adjustment unit 200, the switch SW116, and the determination level shift voltage The configuration of the power supply that outputs Sth2 is not limited to the configuration of the third embodiment.

  As described above, in the pulse modulation type photodetector 53 according to the third embodiment, the determination level adjustment unit 200 integrates the amplified pulse signal S5 and integrates the integrated amplified pulse signal S5 to the comparator 201. A circuit 208 may be further provided.

(Modification of Example 3)
A modification of Example 3 of the pulse modulation type photodetecting device according to the present embodiment will be described with reference to FIGS.

  FIG. 8 is a block diagram of a pulse modulation type photodetection device 54 according to this modification. FIG. 9 is a waveform diagram for explaining the operation of the pulse modulation type photodetection device 54 according to this modification.

  The determination level adjustment unit 200 of FIG. 8 includes an integration circuit 208 and a power source that outputs a variable determination level shift voltage Sth2 '.

  The integration circuit 208 further includes an amplifier 211, current sources 212 and 213, a capacitor 214, and switches SW210 and SW211.

  The integrating circuit 208 integrates and outputs the amplified pulse signal S5. At this time, the amplified pulse signal S5 is input to the non-inverting input terminal (+) of the amplifier 211, and the integration circuit output signal S204 is input to the inverting input terminal (−) of the amplifier 211. Thus, when S5> S204, the current source 212 charges the capacitor 214, and when S5 <S204, the current source 213 discharges the capacitor 214.

  Here, when the current value of the current source 212 is set higher than the current value of the current source 213, and the amplified pulse signal S5 is a signal generated by amplifying periodic noise, an integration circuit is used. The level of the output signal S204 increases as time passes.

  Further, the switch SW211 is turned on in the period sect_1. Accordingly, the power source that outputs the determination level shift voltage Sth2 is controlled by the integration circuit output signal S204 (corresponding to the determination level adjustment signal S200), and the determination level is changed (shifted) from Sth to Sth ′ = Sth + Sth2 ′. Is done.

  At this time, the variable determination level shift voltage Sth2 'changes linearly with respect to the integration circuit output signal S204. This makes it possible to adjust the determination level with higher accuracy than the pulse modulation type photodetection device 53 of the third embodiment.

  When the period sect_1 ends, the switch SW211 is turned OFF, the variable determination level shift voltage Sth2 'becomes 0, and the determination level changes from Sth' to Sth.

  In addition, after the end of the period sect_1, the switch SW210 is turned on for a predetermined time T ′ by the capacitive discharge signal S252 output from the synchronous timing circuit 5. As a result, the capacitor 214 is discharged and the integration circuit output signal S204 is lowered. After the discharge of the capacitor 214, as soon as the switch SW210 is turned off, the integration circuit 208 resumes the integration operation.

  Since the pulse modulation type photodetector 54 according to the present modification uses the integration circuit 208, the pulse modulation type photodetector 54 has the following advantages over the pulse modulation type photodetector 52 according to the second embodiment. That is, there is an advantage that only periodic disturbance light such as inverter light can be detected without reacting to sudden single disturbance light.

  Note that if the amplified pulse signal S5 is integrated and the determination level Sth can be adjusted in the period sect_1 according to the integration value, the determination level adjustment unit 200 and the configuration of the power source that outputs the variable determination level shift voltage Sth2 ′ Is not limited to the configuration of the present modification.

[Capacity 214]
Here, the capacitor 214 in FIGS. 8 and 10 is considered. The frequency of noise of the inverter fluorescent lamp, which is typical disturbance light, is about 50 kHz. In general, since the received light pulse signal S4 when the disturbance light is received by the light receiving element 8 is very small, the amplified pulse signal S5 obtained by amplifying the received light pulse signal S4 is also a very small signal.

For example, consider a case where the amplified pulse signal S5 is a signal having an amplitude of 10 mVpp and a frequency of 50 kHz. In this case, in order to obtain the integration circuit output signal S204 having a peak value of 10 mV by integrating the amplified pulse signal S5 a plurality of times, for example, three times, assuming that the current value of the current source 212 is 1 uA, the following capacitance value C214 is required. Become.
C214 = 1 uA × (1/50 kHz / 2 × 3) / 10 mV = 3 nF (1)
If the capacitor 214 having a capacitance value of 3 nF is formed in an IC chip or the like, the IC chip becomes very large in area and disadvantageous in terms of cost.

[Embodiment 4 of Pulse Modulation Photodetector]
Example 4 of the pulse modulation type photodetecting device according to this embodiment, which is an example for solving the problem in [Capacity 214], will be described with reference to FIGS. Configurations other than those described in the fourth embodiment are the same as those described in [Basic configuration of pulse modulation type photodetection device], the first to third embodiments, and the modification. Further, for convenience of explanation, members having the same functions as those shown in the above [Basic structure of pulse modulation type photodetection device], Examples 1 to 3 and the modified example are denoted by the same reference numerals. A description thereof will be omitted.

  FIG. 10 is a block diagram of the pulse modulation type photodetecting device 55 according to the fourth embodiment. FIG. 11 is a waveform diagram for explaining the operation of the pulse modulation type photo detector 55 according to the fourth embodiment.

  10 includes an integrating circuit 208, a comparator 201, a power source that outputs an ambient light determination level SthN, a switch SW212, a switch SW116, and a power source that outputs a determination level shift voltage Sth2. ing.

  The integrating circuit 208 further includes a comparator 215 (second comparing means), current sources 212 and 213, a capacitor 214, a switch SW210, and a power source 216 that outputs a reference voltage Vref.

  The comparator 215 compares the amplified pulse signal S5 input to one input terminal (for example, a positive terminal) with the reference voltage Vref of the power source 216 input to the other input terminal (for example, the negative terminal). When the amplified pulse signal S5 is higher than the reference voltage Vref, the current source 212 charges the capacitor 214, and when the amplified pulse signal S5 is lower than the reference voltage Vref, the current source 213 discharges the capacitor 214.

  Here, when the current value of the current source 212 is set higher than the current value of the current source 213, and the amplified pulse signal S5 is a signal generated by amplifying periodic noise, an integration circuit is used. The level of the output signal S204 increases as time passes.

  The pulse modulation photodetector 53 according to the third embodiment operates as an analog amplifier in which the amplified pulse signal S5 is input to one input terminal and the integration circuit output signal S204 is input to the other input terminal. For this reason, the amplitude of the integration circuit output signal S204 in the third embodiment is approximately the same as that of the amplified pulse signal S5.

  On the other hand, in the pulse modulation type photodetecting device 54 according to the fourth embodiment, as a comparator in which the amplified pulse signal S5 is input to one input terminal and the reference voltage Vref of the power source 216 is input to the other input terminal. Operate. By performing digital output using the comparator 215, the amplitude of the integration circuit output signal S204 in the fourth embodiment has the same amplitude as the power supply voltage supplied to the comparator 215.

When the power supply voltage supplied to the comparator 215 is set to 3V, for example, the capacitance value C214 of the capacitor 214 is obtained by replacing 10 mV in the above equation (1) with 3V by C214 = 1uA × (1/50 kHz / 2 × 3) / 3V = 10pF (2)
It becomes.

  Therefore, since the capacitance value C214 can be made very small, the problem concerning the area of the IC chip described in [Capacity 214] can be solved.

  The integration circuit output signal S204 is compared with the disturbance light determination level SthN by the comparator 201, and outputs a noise determination signal S207 (corresponding to the determination level adjustment signal S200) from the comparator 201 when the condition of S204> SthN is satisfied (FIG. 11 is Hi).

  The switch SW212 is controlled to be turned on and off by the synchronization timing pulse signal S2, and is turned on during a period stt_1 in which the synchronization timing pulse signal S2 is Hi. Accordingly, the switch SW116 is controlled to be turned on / off by the noise determination signal S207.

  If the noise determination signal S207 is output in the period sect_1 (if it is Hi as shown in FIG. 11), the switch SW116 is turned off. As a result, the determination level is changed (shifted) from Sth to Sth ′ = Sth + Sth2.

  In addition, after the end of the period sect_1, the switch SW210 is turned on for a predetermined time T ′ by the capacitive discharge signal S252 output from the synchronous timing circuit 5. As a result, the capacitor 214 is discharged and the integration circuit output signal S204 is lowered. After the discharge of the capacitor 214, as soon as the switch SW210 is turned off, the integration circuit 208 resumes the integration operation.

  Since the pulse modulation type photo detection device 55 according to the fourth embodiment uses the integration circuit 208, the following advantages are obtained with respect to the pulse modulation type photo detection device 52 according to the second embodiment. That is, there is an advantage that only periodic disturbance light such as inverter light can be detected without reacting to sudden single disturbance light.

  The determination level Sth can be adjusted by integrating a digital signal obtained by comparing the amplified pulse signal S5 with the reference voltage Vref of the power source 216 and comparing the integrated value with the disturbance light determination level SthN. For example, the configuration of the power source that outputs the determination level adjustment unit 200, the comparator 201, the switches SW212 and SW116, and the determination level shift voltage Sth2 is not limited to the configuration of this modification.

  As described above, in the pulse modulation type photodetecting device 55 according to the fourth embodiment, the integrating circuit 208 further has one end connected to the output of the integrating circuit 208 and the other end electrically connected to the ground. 214, the amplified pulse signal S5, and an arbitrarily set reference voltage Vref, and a comparator 215 for outputting a digital signal corresponding to the comparison result between the amplified pulse signal S5 and the reference voltage Vref, and the amplified pulse signal S5 Is a current source 212 that charges the capacitor 214 when the voltage is higher than the reference voltage Vref, and a current source that discharges the capacitor 214 when the amplified pulse signal S5 is equal to or lower than the reference voltage Vref. 213 may be provided.

  In the modified examples of the first to fourth embodiments and the third embodiment, if the period sect_2 can be specified by a signal other than the synchronization timing pulse signal S2, the above-mentioned other than the synchronization timing pulse signal S2 can be specified. These signals can be used. Further, if the level of disturbance light can be measured by a signal other than the amplified pulse signal S5, for example, a signal such as the received light pulse signal S4 or the comparator output pulse signal S6, the received light pulse signal S4 instead of the amplified pulse signal S5. It is also possible to use a signal such as a comparator output pulse signal S6.

[Specification of disturbance light]
As can be seen from the waveform diagram of FIG. 15, the period during which the synchronization timing pulse signal S102 is Hi (corresponding to the period sect_1 in the present embodiment) is longer than the period of the amplified pulse signal due to the disturbance light L3 ″. When it is very long, a plurality of pulses are generated in the amplified pulse signal by L3 ′ + L3 ″.

  Here, if all of the plurality of pulses exceed the determination level Sth, a plurality of pulses are also generated in the comparator output pulse signal S106 '.

  FIG. 15 is a diagram related to a conventional pulse modulation type photodetection device. In the pulse modulation type photodetection devices 50 to 55 according to this embodiment, a comparator output pulse signal similar to the comparator output pulse signal S106 ′ of FIG. When S6 ′ is generated, malfunction is prevented by the processing of the detection means described below.

  In the pulse modulation type photo detectors 50 to 55 according to the present embodiment, the detection means further generates a comparison result signal indicating a result of comparing the amplified pulse signal S5 and the determination level Sth, The comparison result signal is a value that is switched according to the magnitude relationship between the amplified pulse signal S5 and the determination level Sth, and a plurality of pulses are generated in the comparison result signal during the period sect_1 during which the pulsed light L2 is emitted. May be determined to have been erroneously detected. When detecting the presence or absence of the object B passing through the predetermined space, if no disturbance light is present, a single pulse is generated in the period sect_1 during which the pulsed light L2 is emitted. For this reason, the signal processing circuit 11 counts the number of pulses of the comparator output pulse signal S6 in the period sect_1 to determine whether it is single or plural. As a result, the detection means determines that the pulse light L2 is emitted during the period sect_1, which is erroneously detected by disturbance light, and stops the operation of detecting the presence or absence of the detection target passing through the predetermined space. Thus, it is possible to prevent malfunction due to disturbance light.

  Furthermore, the signal processing circuit 11 can prevent the malfunction due to the disturbance light by stopping the operation of detecting the object B when the disturbance light exists.

  Further, in the state where no disturbance light exists, the pulse of the comparator output pulse signal S6 disappears (the value of the comparison result signal) when the delay time α elapses after the period sect_1 ends (after the pulse light L2 disappears). Is switched). Here, the delay time α is a time required from when the synchronization timing pulse signal S2 is input to the light emitting element driving circuit 6 to when the comparator output pulse signal S6 is output. For this reason, the disappearance of the pulse of the comparator output pulse signal S6 does not occur in the period sect_1.

  On the other hand, in the comparator output pulse signal S106 'of FIG. 15, it can be seen that the pulse disappears during the period when the synchronization timing pulse signal S102 is Hi (there is a place where the pulse switches from Hi to Low).

  Here, in the pulse modulation type photo detectors 50 to 55 according to the present embodiment, the detection means further generates a comparison result signal indicating a result of comparing the amplified pulse signal S5 and the determination level Sth. Thus, the value of the comparison result signal is switched according to the magnitude relationship between the amplified pulse signal S5 and the determination level Sth, and the value of the comparison result signal is changed during the period sect_1 during which the pulsed light L2 is emitted. When switching, it may be determined that it is erroneously detected. When the value of the comparison result signal is switched in the period sect_1 (that is, when the pulse of the comparator output pulse signal S6 has disappeared in the period sect_1), the detection unit emits the pulsed light L2. The detection means determines that an error has been detected due to ambient light in the period sect_1, and the operation of detecting the object B passing through the predetermined space is stopped. By doing so, it is possible to prevent malfunction due to ambient light.

〔Electronics〕
Since the electronic apparatus according to the present invention includes any one of the pulse modulation type photo detectors 50 to 55, it is possible to prevent malfunction due to disturbance light.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  Since the pulse modulation type photodetection device of the present invention can prevent malfunction due to disturbance light, the pulse modulation type photodetection device can be suitably used for electronic devices such as FA and OA devices such as copying machines and printers, and amusement devices such as game machines. I can do it.

50 to 55 Pulse modulation type photodetection device 1 Constant voltage circuit 2 Power supply terminal 3 GND terminal 4 Oscillation circuit 5 Synchronization timing circuit 6 Light emitting element driving circuit 7 Light emitting element 8 Light receiving element 9 Amplifier 10 Comparator (detection means)
11 Signal processing circuit (detection means)
12 output circuit 13 output terminal 14 load 15 power source 200 determination level adjustment unit (reference value setting means)
201 Comparator 202 Storage Unit 203 Peak Hold Circuit (Maximum Value Holding Unit)
204 Amplifier 205 Diode 206 Capacitance 207 Power supply 208 Integration circuit (integration means)
210 Storage Unit 211 Amplifier 212 Current Source (First Current Source)
213 Current source (second current source)
214 capacity 215 comparator (second comparison means)
216 Power supply B Object (Detection target)
S1 Basic clock signal S2 Synchronization timing pulse signal S3 Light emission pulse signal S4 Light reception pulse signal (current signal)
S5 Amplified pulse signal (voltage signal)
S5 'Amplified pulse signal S6 Comparator output pulse signal S7 Signal processing circuit output signal S250 Peak hold control signal S251, S252 Capacitance discharge signal SW116 switch (reference value increasing means)
SW206 to SW212 switch SW203 switch (signal switching means)
Sth judgment level (predetermined first reference value)
Sth 'determination level Sth2 determination level shift voltage (first predetermined value)
Sth2 ′ variable determination level shift voltage (second predetermined value)
SthN disturbance light determination level (predetermined second reference value)
sect_1 period sect_2 period (period in which the pulsed light L2 is emitted)

Claims (8)

A light emitting element that emits, in a predetermined space, pulsed light synchronized with a pulse signal obtained by modulating a reference clock signal;
A light receiving element that receives external light including the pulsed light reflected by the detection target passing through the predetermined space, and generates a current signal according to the received external light;
A voltage signal obtained by current-voltage conversion of the current signal is compared with a predetermined first reference value, and when the voltage signal is higher than the first reference value, there is the detection target passing through the predetermined space. A pulse modulation type photo-detecting device comprising: detecting means for detecting that there is no detection target passing through the predetermined space when the voltage signal is equal to or lower than the first reference value,
It is determined whether or not the voltage signal and the pulse signal are synchronized, and when it is determined that the voltage signal and the pulse signal are not synchronized, the first reference value is a value corresponding to the voltage signal. A pulse modulation type photodetecting device comprising reference value setting means for setting to. The reference value setting means further includes:
When the voltage signal is input, and the voltage signal is higher than a predetermined second reference value, the first signal indicating that the voltage signal is higher than a predetermined second reference value is output, and the voltage signal is First comparison means for outputting a second signal indicating that the voltage signal is equal to or less than a predetermined second reference value when the voltage is equal to or less than two reference values;
Only when the pulsed light is emitted, signal switching means for conducting the signal output from the first comparison means; and
When the signal conducted by the signal switching means is the first signal, the first reference value is increased by a first predetermined value, and the signal conducted by the signal switching means is the second signal, The pulse modulation type photo detection device according to claim 1, further comprising a reference value increasing unit that does not increase the first reference value. The reference value setting means further includes:
A maximum value holding means for holding the maximum value of the voltage signal;
2. The pulse modulation type according to claim 1, wherein when the pulsed light is emitted, the first reference value is increased by a second predetermined value corresponding to the maximum value held by the maximum value holding means. Photodetector.   3. The pulse modulation type photodetection according to claim 2, wherein the reference value setting means further includes integration means for integrating the voltage signal and outputting the integrated voltage signal to the first comparison means. apparatus. The integration means further includes:
A capacitor having one end connected to the output of the integrating means and the other end electrically grounded;
A comparator which is a second comparison unit that receives the voltage signal and an arbitrarily set reference voltage as input and outputs a digital signal corresponding to a comparison result between the voltage signal and the reference voltage;
A first current source that charges the capacitor when the voltage signal is greater than the reference voltage;
5. The pulse modulation according to claim 4, further comprising: a second current source having a current value smaller than that of the first current source that discharges the capacitor when the voltage signal is equal to or lower than the reference voltage. Type photodetection device. The detection means further generates a comparison result signal indicating a result of comparing the voltage signal with the first reference value,
The comparison result signal is a value that is switched according to the magnitude relationship between the voltage signal and the first reference value.
6. The method according to claim 1, wherein when a plurality of pulses are generated in the comparison result signal during a period in which the pulsed light is emitted, it is determined that an erroneous detection has occurred. Pulse modulation type photo detector. The detection means further generates a comparison result signal indicating a result of comparing the voltage signal with the first reference value,
The comparison result signal is a value that is switched according to the magnitude relationship between the voltage signal and the first reference value.
The pulse modulation type according to any one of claims 1 to 5, wherein when the value of the comparison result signal is switched during a period in which the pulsed light is emitted, it is determined that the pulse is erroneously detected. Photodetector.   An electronic apparatus comprising the pulse modulation type photodetecting device according to claim 1.

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