Distance measurement system and light detection device

Abstract

[Problem] To provide a ranging system which can adjust the bias voltage supplied to an avalanche photodiode. [Solution] This ranging system is provided with a light emission device which irradiates a ranging beam, and a light detection device which receives reflected light of the ranging beam. The light detection device comprises: a pixel array which comprises an arrangement of pixels, each of which includes multiple avalanche photodiodes that detect reflected light; a current measurement circuit which measures the total pixel current of the pixel array; and a bias voltage control unit which uses the detection results of the current measurement circuit to control the bias voltage supplied to the multiple avalanche photodiodes. The light emission device has a light emission control unit which uses the detection results of the current measurement circuit to control the intensity of the ranging beam.

Description

Technical Field

[0001] The present disclosure relates to a distance measurement system and a light detection device.

Background Art

[0002] A distance measurement system using a plurality of avalanche photodiodes typified by an APD (Avalanche Photo Diode) or an SPAD (Single Photon Avalanche Diode) is known. This distance measurement system includes a pixel array composed of a plurality of pixels including avalanche photodiodes. In the pixel array, there are active pixels set to react to incident light and non-active pixels set not to react to incident light.

[0003] In the pixel array, the number of non-active pixels is dominant. Therefore, a technique has been proposed to adjust the bias voltage supplied to each avalanche photodiode based on the result of measuring the leakage current flowing through the non-active pixels.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, in an environment with a short distance or strong background light, the photodiode may react to light. In this case, although the proportion of active pixels is small, it is assumed that the total current of the entire pixel array greatly deviates from the total current of the leakage current. Therefore, with the bias voltage set based only on the measurement result of the leakage current, situations such as a decrease in distance measurement performance and an increase in power consumption may occur.

[0006] The present disclosure provides a distance measurement system and a photodetection device capable of optimizing a bias voltage supplied to an avalanche photodiode.

Means for Solving the Problems

[0007] A distance measurement system according to an embodiment of the present disclosure includes a light emitting device that irradiates distance measurement light, and a photodetection device that receives reflected light of the distance measurement light. The photodetection device includes a pixel array in which a plurality of pixels each including a plurality of avalanche photodiodes for detecting reflected light are arranged, a current measurement circuit that measures the total pixel current of the pixel array, and a bias voltage control unit that controls a bias voltage supplied to the plurality of avalanche photodiodes using a detection result of the current measurement circuit. The light emitting device has a light emission control unit that controls the amount of the distance measurement light using the detection result of the current measurement circuit.

[0008] The current measurement circuit a resistance element connected in series to the plurality of avalanche photodiodes, a first operational amplifier that outputs a voltage of the resistance element, and a low-pass filter that smoothes an output value of the first operational amplifier. The bias voltage control unit has a second operational amplifier that adjusts the bias voltage according to a difference between an average pixel current value obtained by smoothing by the low-pass filter and a preset first target value. The light emission control unit may have a third operational amplifier that adjusts the amount of light according to a difference between the average pixel current value and a preset second target value.

[0009] The current measurement circuit a resistance element connected in series to the plurality of avalanche photodiodes, a first operational amplifier that outputs a voltage of the resistance element, an integration circuit that integrates an output value of the first operational amplifier, and a holding circuit that temporarily holds an integration value of the integration circuit. The bias voltage control unit has a second operational amplifier that adjusts the bias voltage according to the difference between the holding value of the holding circuit and a preset first target voltage. The light emission control unit may have a third operational amplifier that adjusts the light quantity according to the difference between the holding value and a preset second target value.

[0010] The light detection device further has a constant voltage source connected to the plurality of avalanche photodiodes. The current measurement circuit has a resistance element connected to the plurality of avalanche photodiodes via the constant voltage source, and a first operational amplifier that outputs the voltage of the resistance element. The bias voltage control unit has an integration circuit that integrates the output value of the first operational amplifier, a holding circuit that temporarily holds the integration value of the integration circuit, and a second operational amplifier that adjusts the bias voltage and the constant voltage source according to the difference between the holding value of the holding circuit and a preset first target voltage. The light emission control unit may have a third operational amplifier that adjusts the light quantity according to the difference between the holding value and a preset second target value.

[0011] The constant voltage source has a current mirror circuit having a first transistor connected in series to the plurality of avalanche photodiodes and a second transistor connected in series to the resistance element, and may have a fourth operational amplifier that controls the first transistor and the second transistor according to the difference between the total pixel current and the output value of the second operational amplifier.

[0012] The light detection device has a plurality of switch elements that respectively switch the plurality of pixels to active pixels or non-active pixels, and a non-active pixel current measurement circuit that measures a non-active pixel current indicating the sum of the pixel currents of the non-active pixels. An active pixel current measurement circuit that subtracts the detection value of the non-active pixel current measurement circuit from the detection value of the current measurement circuit to measure the active pixel current indicating the total pixel current of the active pixels may be further provided.

[0013] The active pixel current measurement circuit A first sampling hold circuit that temporarily holds a first detection value detected by the active pixel current measurement circuit before irradiation of the ranging light; A second sampling hold circuit that temporarily holds a second detection value detected by the active pixel current measurement circuit after irradiation of the ranging light; The light emission control unit may include a first operational amplifier that outputs a difference between the first detection value and the second detection value; A second operational amplifier that adjusts the light amount according to a difference between an output value of the first operational amplifier and a preset target value.

[0014] The plurality of avalanche photodiodes are provided on a first semiconductor substrate; A part of the light detection device excluding the plurality of avalanche photodiodes may be provided on a second semiconductor substrate bonded to the first semiconductor substrate.

[0015] The plurality of avalanche photodiodes are provided on a first semiconductor substrate; All of the light detection device excluding the plurality of avalanche photodiodes may be provided on a second semiconductor substrate bonded to the first semiconductor substrate.

[0016] The current measurement circuit may be connected to an anode of each of the plurality of avalanche photodiodes.

[0017] The current measurement circuit may be connected to a cathode of each of the plurality of avalanche photodiodes.

[0018] The light detection device according to an embodiment of the present disclosure includes a pixel array in which a plurality of pixels each including a plurality of avalanche photodiodes for detecting reflected light of ranging light are arranged, a current measurement circuit for measuring the total pixel current of the pixel array, and a bias voltage control unit for controlling a bias voltage supplied to the plurality of avalanche photodiodes using the detection result of the current measurement circuit.

[0019] The current measurement circuit a resistance element connected in series to the plurality of avalanche photodiodes, a first operational amplifier that outputs a voltage of the resistance element, and a low-pass filter that smoothes an output value of the first operational amplifier. The bias voltage control unit may include a second operational amplifier that adjusts the bias voltage according to a difference between an average pixel current value obtained by smoothing by the low-pass filter and a preset first target value.

[0020] The current measurement circuit a resistance element connected in series to the plurality of avalanche photodiodes, a first operational amplifier that outputs a voltage of the resistance element, an integration circuit that integrates an output value of the first operational amplifier, and a holding circuit that temporarily holds an integrated value of the integration circuit. The bias voltage control unit may include a second operational amplifier that adjusts the bias voltage according to a difference between a held value of the holding circuit and a preset first target voltage.

[0021] The light detection device further includes a constant voltage source connected to the plurality of avalanche photodiodes, The current measurement circuit a resistance element connected to the plurality of avalanche photodiodes via the constant voltage source, and a first operational amplifier that outputs a voltage of the resistance element. The bias voltage control unit an integration circuit that integrates an output value of the first operational amplifier, A holding circuit that temporarily holds the integration value of the integration circuit; It may further include a second operational amplifier that adjusts the bias voltage and the constant voltage source according to the difference between the holding value of the holding circuit and a preset first target voltage.

[0022] The constant voltage source A current mirror circuit having a first transistor connected in series to the plurality of avalanche photodiodes and a second transistor connected in series to the resistance element; It may further include a third operational amplifier that controls the first transistor and the second transistor according to the difference between the total pixel current and the output value of the second operational amplifier.

[0023] A plurality of switch elements that respectively switch the plurality of pixels to active pixels or non-active pixels; A non-active pixel current measurement circuit that measures a non-active pixel current indicating the sum of the pixel currents of the non-active pixels; It may further include an active pixel current measurement circuit that subtracts the detection value of the non-active pixel current measurement circuit from the detection value of the current measurement circuit to measure an active pixel current indicating the sum of the pixel currents of the active pixels.

[0024] The active pixel current measurement circuit May include a first sampling and holding circuit that temporarily holds a first detection value detected by the active pixel current measurement circuit before irradiation of the ranging light; And a second sampling and holding circuit that temporarily holds a second detection value detected by the active pixel current measurement circuit after irradiation of the ranging light.

[0025] The plurality of avalanche photodiodes are provided on a first semiconductor substrate, A part of the light detection device excluding the plurality of avalanche photodiodes may be provided on a second semiconductor substrate bonded to the first semiconductor substrate.

[0026] The plurality of avalanche photodiodes are provided on a first semiconductor substrate, All of the light detection device except for the plurality of avalanche photodiodes may be provided on a second semiconductor substrate bonded to the first semiconductor substrate.

Brief Description of the Drawings

[0027]

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Mode for Carrying Out the Invention

[0028] (First Embodiment) FIG. 1 is a block diagram showing a configuration example of the distance measurement system according to the first embodiment. The distance measurement system 1 shown in FIG. 1 is a system that captures a distance image using the ToF (Time of Flight) method, and includes a light emitting device 10 and an imaging device 20.

[0029] The light emitting device 10 includes a light emission control unit 11 and a light emitting element 12. The light emission control unit 11 controls the pattern in which the light emitting element 12 irradiates the distance measurement light based on the control of the control unit 22. Specifically, the light emission control unit 11 controls the pattern in which the light emitting element 12 irradiates the distance measurement light according to the irradiation code included in the irradiation signal supplied from the control unit 22. For example, the irradiation code consists of two values, "1" (High) and "0" (Low). The light emission control unit 11 turns on the light emitting element 12 when the value of the irradiation code is "1", and turns off the light emitting element 12 when the value of the irradiation code is "0".

[0030] The light emitting element 12 emits distance measurement light in a predetermined wavelength range based on the control of the light emission control unit 11. The light emitting element 12 is, for example, an infrared laser diode. The type of the light emitting element 12 and the wavelength range of the distance measurement light can be arbitrarily set according to the use of the distance measurement system 1 and the like.

[0031] The imaging device 20 receives reflected light in which the distance measurement light is reflected by the subject 102 and the subject 103. The imaging device 20 includes an imaging unit 21, a control unit 22, a display unit 23, and a storage unit 24.

[0032] The imaging unit 21 has a lens 30, a light detection device 40, and a signal processing circuit 50. The lens 30 forms an image of incident light on the light detection device 40. Note that the configuration of the lens 30 is arbitrary, and for example, the lens 30 can be configured by a plurality of lens groups.

[0033] The light detection device 40 performs imaging of the subject 102, the subject 103, etc. based on the control of the control unit 22. Further, the light detection device 40 outputs a signal obtained by imaging to the signal processing circuit 50.

[0034] The signal processing circuit 50 processes the output signal of the light detection device 40 based on the control of the control unit 22. For example, the signal processing circuit 50 detects the distance to the subject based on the output signal of the light detection device 40 and generates a distance image indicating the distance to the subject.

[0035] The control unit 22 is composed of, for example, a control circuit such as an FPGA (Field Programmable Gate Array) or a DSP (Digital Signal Processor), or a processor, etc. The control unit 22 controls the light emission control unit 11, the light detection device 40, and the signal processing circuit 50.

[0036] The display unit 23 is composed of, for example, a panel type display device such as a liquid crystal display device or an organic EL (Electro Luminescence) display device.

[0037] The storage unit 24 can be configured by an arbitrary storage device, storage medium, etc., and stores a distance image, etc.

[0038] FIG. 2 is a diagram showing the circuit configuration of the light emission device 10 and the light detection device 40 in the first embodiment.

[0039] First, the circuit configuration of the light-emitting device 10 will be described. In the light-emitting device 10, a light-emitting control unit 11 is connected in series to a light-emitting element 12. The light-emitting element 12 irradiates the subject 102 with the distance-measuring light L1. At this time, the light amount of the distance-measuring light L1 is controlled by the light-emitting control unit 11.

[0040] The light-emitting control unit 11 includes a variable current source 111 and an operational amplifier 112. The variable current source 111 supplies a direct-current light-emitting current to the light-emitting element 12. The light-emitting current corresponds to the light amount of the distance-measuring light L1 and is adjusted by the operational amplifier 112. A signal indicating the average pixel current value obtained from an LPF (low-pass filter) 423, which will be described later, is input to the non-inverting input terminal (+) of the operational amplifier 112. The potential of the inverting input terminal (-) is set to the target value V 10 which is set.

[0041] The operational amplifier 112 adjusts the light-emitting current of the variable current source 111 according to the difference between the signal value (average pixel current value) and the target value V 10 For example, when the signal value (average pixel current value) is larger than the target value V 10 the light-emitting current supplied from the variable current source 111 increases. Conversely, when the signal value (average pixel current value) is smaller than the target value V 10 the light-emitting current decreases.

[0042] Next, the circuit configuration of the light-detecting device 40 will be described. The light-detecting device 40 includes a pixel array 401, a current measurement circuit 402, a bias voltage control unit 403, and a bias power source 404.

[0043] The pixel array 401 includes a plurality of pixels 401a and a plurality of pixels 401b arranged two-dimensionally. Each pixel 401a and each pixel 401b include a light-detecting element 411, a switch element 412, a current source 413, and an inverter 414.

[0044] The light detection element 411 is an avalanche photodiode typified by an APD or an SPAD. The cathode of the light detection element 411 is connected to a current source 413 and an inverter 414. The anode of the light detection element 411 is connected to a current measurement circuit 402.

[0045] The switch element 412 is composed of an N-type MOS transistor that switches each pixel between an active pixel and a non-active pixel. A control signal is input from the control unit 22 to the gate of the switch element 412. When the switch element 412 turns off based on the control signal, the light detection element 411 switches to an active pixel that responds to the reflected light L2. Conversely, when the switch element 412 turns on based on the control signal, the light detection element 411 switches to a non-active pixel that does not respond to the reflected light L2. In the present embodiment, the pixel 401a is set as an active pixel, and the pixel 401b is set as a non-active pixel.

[0046] In the present embodiment, when the distance measurement system 1 operates normally, the number of active pixels is less than the number of non-active pixels.

[0047] The current source 413 is composed of a P-type MOS transistor that supplies a variable voltage to the cathode of the light detection element 411. When a reverse voltage equal to or higher than the breakdown voltage is applied between the anode and cathode of the light detection element 411 by the current source 413, the light detection element 411 is set to the Geiger mode. When photons enter the light detection element 411 set to the Geiger mode, avalanche multiplication occurs, and a current flows through the light detection element 411. This current is input to the inverter 414.

[0048] The inverter 414 compares the voltage at the input terminal, in other words, the cathode voltage of the light detection element 411, with a reference voltage. Further, the inverter 414 outputs, from the output terminal to the signal processing circuit 50, a signal indicating whether the cathode voltage is higher or lower than the reference voltage. The signal processing circuit 50 can detect the voltage change of the cathode voltage based on this signal.

[0049] The current measurement circuit 402 includes a resistor element 421, an operational amplifier 422, and an LPF 423. The resistor element 421 is connected in series to all the photodetector elements 411 provided in the pixels 401a and 401b. The non-inverting input terminal (+) of the operational amplifier 422 is connected to one end of the resistor element 421, and the inverting input terminal (-) is connected to the other end of the resistor element 421. The operational amplifier 422 outputs the voltage across both ends of the resistor element 421 from the output terminal to the bias voltage control unit 403. The output value of the operational amplifier 422 corresponds to the total pixel current of the pixel array 401. The LPF 423 smoothes the output value of the operational amplifier 422. As a result, a pixel current average value corresponding to the average of the total pixel currents of the pixel array 401 is obtained.

[0050] Note that in this embodiment, the current measurement circuit 402 is composed of an analog circuit, but a part of it may be composed of a digital circuit. Specifically, the current measurement circuit 402 includes an ADC (analog-to-digital converter), a digital LPF, and a DAC (digital-to-analog converter). The ADC converts the analog signal output from the operational amplifier 422 into a digital signal. The digital LPF performs a smoothing process on this digital signal. The DAC converts the smoothed digital signal into an analog signal.

[0051] In this embodiment, the pixel current average value obtained by smoothing with the LPF 423 is also input to the non-inverting input terminal (+) of the operational amplifier 112 of the light emission control unit 11. The operational amplifier 112 adjusts the light emission current supplied from the variable current source 111 to the light emitting element 12 so that the pixel current average value matches the target value V10.

[0052] The bias voltage control unit 403 includes an operational amplifier 431. The above pixel current average value is input to the non-inverting input terminal (+) of the operational amplifier 431. The potential of the inverting input terminal (-) of the operational amplifier 431 is set to the target value V 20 is set. The operational amplifier 431 controls the bias power supply 404 so that the pixel current average value matches the target value V 20 That is, the operational amplifier 431 compares the pixel current average value with the target value V20 The bias voltage supplied from the bias power supply 404 to the anode of each photodetector 411 is adjusted according to the difference therewith.

[0053] FIG. 3 is a circuit diagram showing the configuration of the bias power supply 404. The bias power supply 404 includes an operational amplifier 441 and a current source 442. The non-inverting input terminal (+) of the operational amplifier 441 is connected to the anode of each photodetector 411 via a resistive element 421. On the other hand, the inverting input terminal (-) is connected to the output terminal of the above-described operational amplifier 431. The current source 442 is composed of an N-type MOS transistor. The gate of the N-type MOS transistor is connected to the output terminal of the operational amplifier 441. The drain is connected to the non-inverting input terminal (+) of the operational amplifier 441. The source is grounded. In the bias power supply 404, the bias voltage supplied to the anode of each photodetector 411 is adjusted by the operational amplifier 441 controlling the gate potential of the N-type MOS transistor.

[0054] FIG. 4 is a timing chart showing the operation timing of the distance measurement system 1 according to the present embodiment. Hereinafter, with reference to FIG. 4, the operation of the distance measurement system 1 configured as described above will be described.

[0055] Every time the light emitting element 12 emits light at a period T, the distance measurement light L1 is irradiated onto the subject 102. Further, the reflected light L2 is detected by the photodetector 411 of each pixel 401a. This photodetector 411 also detects the background light L3 (see FIG. 2) of the installation environment of the subject 102. The amount of the background light L3 is smaller than the amount of the reflected light L2.

[0056] The total pixel current obtained by summing the currents of all the pixels of the pixel array 401 measured by the current measurement circuit 402 includes a current component indicating the amount of the background light L3 and a current component obtained by adding the amount of the reflected light L2 to the amount of the background light L3. The total pixel current includes the leakage current I of each pixel 401b (non-active pixel). LIt also includes the components. The breakdown voltage of the photodetector 411 has variations due to temperature changes and individual differences. Therefore, in the non-active pixel (pixel 401b), the anode-cathode voltage of the photodetector 411 does not drop to the breakdown voltage, and a leakage current may be generated in response to photons.

[0057] The total pixel current is smoothed by the LPF 423. Thereby, the average pixel current value is obtained. Thereafter, the bias voltage is adjusted by the operational amplifier 431 of the bias voltage control unit 403 so that the total pixel current becomes constant. For example, in an environment where the amount of the background light L3 is large, the total pixel current also becomes large. In this case, in the bias power supply 404, the operational amplifier 441 lowers the gate potential of the current source 442 (N-type MOS transistor). As a result, the bias voltage rises.

[0058] On the other hand, in an environment where the amount of the background light L3 is small, the total pixel current also becomes small. In this case, in the bias power supply 404, the operational amplifier 441 raises the gate potential of the current source 442 (N-type MOS transistor). As a result, the bias voltage drops.

[0059] Therefore, according to the present embodiment, the pixel currents of both the active pixel (pixel 401a) and the non-active pixel (pixel 401b) are measured and the bias voltage is adjusted. Therefore, it is possible to optimize the bias voltage according to the amount of the background light L3.

[0060] Also, in the present embodiment, the light emission control unit 11 adjusts the light emission current based on the average pixel current value obtained by the smoothing of the LPF 423. For example, in an environment where the amount of the background light L3 is large, the average pixel current value also becomes large. In this case, the operational amplifier 112 adjusts the variable current source 111 so as to increase the light emission current. As a result, it is possible to maintain the ranging performance even in an environment where the amount of the background light L3 is large.

[0061] On the other hand, in an environment where the amount of the background light L3 is small, the average value of the pixel current also becomes small. In this case, the operational amplifier 112 adjusts the variable current source 111 that reduces the emission current. Thereby, in an environment where the amount of the background light L3 is small, it becomes possible to reduce the power consumption of the light-emitting device 10.

[0062] (Second Embodiment) FIG. 5 is a diagram showing the circuit configurations of the light-emitting device 10 and the light detection device 40 in the second embodiment. The same components as those in the first embodiment described above are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0063] In the present embodiment, the configuration of the current measurement circuit 402 is different from that in the first embodiment. An integration circuit 424 and a holding circuit 425 are provided in the current measurement circuit 402 according to the present embodiment instead of the LPF 423.

[0064] The integration circuit 424 is connected to the output terminal of the operational amplifier 422 of the current measurement circuit 402. The integration circuit 424 integrates the output value of the operational amplifier 422, that is, the total pixel current, and outputs it to the holding circuit 425. The holding circuit 425 temporarily holds the integrated value of the integration circuit 424, that is, the integrated value of the total pixel current.

[0065] FIG. 6 is a timing chart showing the operation timing of the distance measurement system according to the present embodiment. Hereinafter, with reference to FIG. 6, the operation of the distance measurement system according to the present embodiment will be described.

[0066] Also in the present embodiment, as in the first embodiment, each time the light-emitting element 12 irradiates the subject 102 with the distance measurement light L1 at the period T, the light detection element 411 of each pixel 401a detects the reflected light L2 and the background light L3. Further, the total pixel current detected by the current measurement circuit 402 also includes a current component indicating the amount of the background light L3, a current component indicating the amount of the reflected light L2, and the leakage current I L of each pixel 401b (non-active pixel).

[0067] The above-described total pixel current is integrated by the integrating circuit 424. The integrating circuit 424 integrates the total pixel current based on a control signal input at the same period T as the light emission period of the light emitting element 12 from the control unit 22. That is, the integration period of the integrating circuit 424 is set to the period T.

[0068] Subsequently, the integration value of the integrating circuit 424 is held by the holding circuit 425. The holding circuit 425 also holds the integration value based on the above-described control signal. That is, the holding period of the holding circuit 425 is set to the period T.

[0069] Thereafter, the operational amplifier 431 adjusts the bias voltage according to the difference between the above integration value and the target value V 21 Note that this target value V 21 is a value different from the target value V 20 described in the first embodiment. In this way, the bias voltage is adjusted so that the total pixel current becomes constant.

[0070] Also, in this embodiment, the light emission control unit 11 adjusts the light emission current according to the difference between the integration value of the pixel current temporarily held by the holding circuit 425 and the target value V 11 Note that this target value V 11 is a value different from the target value V 10 described in the first embodiment. In this way, since the light emission current is adjusted, the light amount of the distance measurement light L1 is optimized according to the light amount of the background light L3.

[0071] According to the present embodiment described above, since the bias voltage is adjusted using the total pixel current of the pixel array 401, it is possible to optimize the light detection performance according to the light amount of the background light L3. In addition, since the light emission current is also adjusted using the above total pixel current, it is possible to optimize the light emission performance according to the light amount of the background light L3.

[0072] (Third Embodiment) FIG. 7 is a diagram showing a part of the circuit configuration of the light emitting device 10 and the light detection device 40 in the third embodiment. The same components as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

[0073] The photodetection device 40 according to this embodiment further includes a constant voltage source 405. The constant voltage source 405 according to this embodiment is a bias power supply having a current detection function, and includes a first transistor 451, a second transistor 452, an operational amplifier 453, and a constant voltage negative power supply 454. The first transistor 451 and the second transistor 452 are N-type MOS transistors and constitute a current mirror circuit.

[0074] The drain of the first transistor 451 is connected to the anode of each photodetection element 411, and the source is connected to the constant voltage negative power supply 454. On the other hand, the drain of the second transistor 452 is connected in series to the resistance element 421 of the current measurement circuit 402, and the source is connected to the constant voltage negative power supply 454. The gate of each transistor is connected to the output terminal of the operational amplifier 453.

[0075] The non-inverting input terminal (+) of the operational amplifier 453 is connected to the anode of each photodetection element 411, and the inverting input terminal (-) is connected to the output terminal of the operational amplifier 431 of the bias voltage control unit 403.

[0076] In this embodiment, the total pixel current flows through the first transistor 451. At this time, since the second transistor 452 constitutes a current mirror circuit with the first transistor 451, the same current as the total pixel current flows through the second transistor 452 and is detected by the resistance element 421. Also, the operational amplifier 422 outputs the detected current of the resistance element 421.

[0077] Subsequently, similar to the second embodiment, the total pixel current is integrated by the integration circuit 424, and the integrated value is temporarily held by the holding circuit 425. Then, the operational amplifier 431 compares the integrated value temporarily held by the holding circuit 425 with the target value V 20The bias voltage is adjusted according to the difference therewith. Also, in the operational amplifier 453 of the constant voltage source 405, the gate potentials of each of the first transistor 451 and the second transistor 452 are adjusted according to the difference between the current flowing through the first transistor 451 and the output value of the operational amplifier 431. Note that in this embodiment, an LPF 423 described in the first embodiment may be provided instead of the integrating circuit 424 and the holding circuit 425. In this case, the total pixel current is smoothed.

[0078] According to the present embodiment described above, similarly to the second embodiment, it is possible to optimize the light detection performance and the light emission performance according to the amount of the background light L3. In addition, in this embodiment, by using a bias power source 405 having a current detection function as the bias power source, the total pixel current can be measured with a circuit configuration in which the resistance element 421 is not arranged in the current path between the light detection element 411 and the bias power source.

[0079] (Fourth Embodiment) FIG. 8 is a diagram showing the circuit configurations of the light emitting device 10 and the light detection device 40 in the fourth embodiment. The same components as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted. The light detection device 40 according to this embodiment further includes a non-active pixel current measurement circuit 406 and an active pixel current measurement circuit 407.

[0080] The non-active pixel current measurement circuit 406 is a circuit for measuring a non-active pixel current indicating the sum of the pixel currents of the pixels 401b set as non-active pixels. Specifically, the non-active pixel current measurement circuit 406 includes a resistance element 461, an operational amplifier 462, and an LPF 463. One end of the resistance element 461 is connected to a current path (for example, the source of the switch element 412), and the other end is grounded.

[0081] One end of a resistor element 461 is connected to the non-inverting input terminal (+) of an operational amplifier 462, and the potential of the inverting input terminal (-) is grounded. The operational amplifier 462 outputs the voltage of the resistor element 461 to an LPF 463 as an inactive pixel current. The LPF 463 smoothes the inactive pixel current. Thereby, the average value of the inactive pixel current is obtained.

[0082] On the other hand, an active pixel current measurement circuit 407 is a circuit for measuring an active pixel current indicating the sum of the pixel currents of pixels 401a set as active pixels. Specifically, the active pixel current measurement circuit 407 includes an operational amplifier 471, a first sampling hold (S / H) circuit 472, and a second sampling hold (S / H) circuit 473.

[0083] The average value of the total pixel currents measured by the LPF 423 is input to the non-inverting input terminal (+) of the operational amplifier 471, and the average value of the inactive pixel currents measured by the inactive pixel current measurement circuit 406 is input to the inverting input terminal (-). The operational amplifier 471 measures the active pixel current by subtracting the average value of the inactive pixel currents from the average value of the total pixel currents.

[0084] The first sampling hold circuit 472 temporarily holds the first detection value of the operational amplifier 471 before the light emitting element 12 irradiates the distance measuring light L1. On the other hand, the second sampling hold circuit 473 temporarily holds the second detection value of the operational amplifier 471 after the light emitting element 12 irradiates the distance measuring light L1. The first detection value and the second detection value are simultaneously output to the light emission control unit 11.

[0085] The light emission control unit 11 according to this embodiment further includes an operational amplifier 113. The second detection value is input to the non-inverting input terminal (+) of the operational amplifier 113, and the first detection value is input to the inverting input terminal (-). The operational amplifier 113 outputs the difference between the second detection value and the first detection value. This difference corresponds to the reaction current of the light detection element 411 of the pixel 401a with respect to the ranging light L1. This reaction current is input to the non-inverting input terminal (+) of the operational amplifier 112. The operational amplifier 112 adjusts the light emission current according to the difference between the reaction current and the target value V 12 and the difference.

[0086] FIG. 9 is a timing chart showing the operation timing of the ranging system according to this embodiment. FIG. 10 is a flowchart showing the operation procedure of the ranging system according to this embodiment. Hereinafter, with reference to FIGS. 9 and 10, the operation of the ranging system according to this embodiment will be described.

[0087] First, the light emitting element 12 turns off based on the control of the light emission control unit 11 (step S1). In this case, the background light L3 is incident on the light detection elements 411 of each of the pixel 401a (active pixel) and the pixel 401b (non-active pixel).

[0088] Next, the current measurement circuit 402 measures the total pixel current I 10 (step S2). In parallel with step S2, the non-active pixel current measurement circuit 406 measures the non-active pixel current I 20 (step S3). The total pixel current I 10 and the non-active pixel current I 20 include only the current component of the background light L3.

[0089] Next, the active pixel current measurement circuit 407 subtracts the non-active pixel current I 10 from the total pixel current I 20 to measure the active pixel current I 30 (step S4). The active pixel current I 30 is held by the first sample and hold circuit 472 (step S5).

[0090] Next, the light-emitting element 12 lights up based on the control of the light emission control unit 11 (step S6). In this case, the distance measurement light L1 is irradiated from the light-emitting element 12 toward the subject 102, and the reflected light L2 and the background light L3 enter each light detection element 411 of the pixel 401a (active pixel) and the pixel 401b (non-active pixel).

[0091] Next, the current measurement circuit 402 measures the total pixel current I 11 (step S7). In parallel with step S7, the non-active pixel current measurement circuit 406 measures the non-active pixel current I 22 (step S8). The total pixel current I 11 and the non-active pixel current I 22 include not only the current component of the background light L3 but also the current component of the reflected light L2.

[0092] Next, the active pixel current measurement circuit 407 subtracts the non-active pixel current I 11 from the total pixel current I 21 to measure the active pixel current I 31 (step S9). The active pixel current I 31 is held in the second sampling hold circuit 472 (step S10).

[0093] Subsequently, the active pixel current I 30 and the active pixel current I 31 are simultaneously input to the light emission control unit 11. The light emission control unit 11 subtracts the active pixel current I 31 from the active pixel current I 30 to measure the active pixel current I 32 (step S11). Since the active pixel current I 32 includes only the current component of the reflected light L2, it corresponds to the reaction current of the light detection element 411 of the active pixel with respect to the distance measurement light L1.

[0094] Finally, the light emission control unit 11 adjusts the light emission current based on the active pixel current I 32 (step S12). Also, the bias voltage control unit 403 controls the total pixel current I11 Adjust the bias voltage based on this. As a result, the total pixel current and the active pixel current each become the target current I tgt1 and the target current I tgt1 and are controlled accordingly.

[0095] According to this embodiment, as described above, the bias voltage is controlled so that the current consumption of the entire pixel array 401 becomes a predetermined current target value, and the emission current is controlled so that the active pixel current due to the reflected light L2 becomes a predetermined current target value. As a result, the current component of the reflected light L3 increases by suppressing the current component of the background light L3 and the leakage current I L , and the light amount of the ranging light L1 increases.

[0096] Also, in this embodiment, the photon reaction of the photodetector 411 that cannot be detected by the inverter 414 of each pixel can be detected. Hereinafter, this effect will be described with reference to FIG. 11.

[0097] FIG. 11 is a timing chart showing the operation timings of the photodetector 411 and the inverter 414. FIG. 11 shows the voltage V D between the anode and the cathode of the photodetector 411 of the active pixel and the change in the current I D .

[0098] First, due to the photon reaction of the photodetector 411 with respect to the incident light L11 at time t1, a current due to avalanche multiplication flows. Therefore, the anode-cathode voltage V D drops to the voltage obtained by adding the breakdown voltage ■bd and the voltage obtained by integrating the series parasitic resistance Rs and the current Iq. As a result, the avalanche multiplication stops (exits the Geiger mode).

[0099] Subsequently, a so-called recharge operation is performed in which current flows from the current source 413 and the anode-cathode voltage V D recovers. At this time, since the light amount of the background light L31 is sufficiently small, no photon reaction occurs during the recharge operation.

[0100] Thereafter, due to the photon reaction of the photodetector 411 with respect to the incident light L12 at time t2, a current Iq due to avalanche multiplication flows. Due to the photon reaction, the voltage V between the anode and the cathode D drops again, and subsequently the recharge operation is started. At this time, since the amount of the background light L32 is larger than that of the background light 31, the photon reaction occurs multiple times. Therefore, a current flows for each photon reaction.

[0101] However, if this photon reaction occurs before the voltage V between the anode and the cathode D exceeds the reference voltage of the inverter 414, the level of the output pulse of the inverter 414 does not change, so the photon reaction cannot be detected.

[0102] On the other hand, in the present embodiment, the active pixel current including only the current component of the background light L3 can be measured. Therefore, the photon reaction of the photodetector 411 that cannot be detected by the inverter 414 can be detected.

[0103] (Fifth Embodiment) FIG. 12 is a diagram showing the circuit configurations of the light-emitting device 10 and the light-detecting device 40 in the fifth embodiment. The same components as those in the first embodiment described above are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0104] In the pixel array 401 of the light-detecting device 40 according to the present embodiment, the anode of the photodetector 411 is connected to the inverter 414, and the cathode is connected to the current measurement circuit 402. The inverter 414 outputs a digital signal indicating whether or not the anode voltage has changed to the signal processing circuit 50. Further, a current source 413a composed of an N-type MOS transistor and a switch element 412a composed of a P-type MOS transistor are connected to the anode of the photodetector 411.

[0105] The current measurement circuit 402 measures the average value of the total pixel current on the cathode side of the photodetection element 411. Note that in the current measurement circuit 402, an integration circuit 424 and a holding circuit 425 described in the second embodiment may be provided instead of the LPF 423.

[0106] The bias voltage control unit 403 adjusts the bias voltage supplied from the bias power supply 404 to the cathode of each photodetection element 411 according to the difference between the pixel current average value obtained by smoothing with the LPF 423 and the target value V 22 . Also, the operational amplifier 112 of the light emission control unit 11 adjusts the light emission current of the light emitting element 12 according to the difference between the pixel current average value and the target value V 13 .

[0107] Also in the present embodiment described above, similar to the first embodiment, the pixel currents of both the active pixels (401a) and the non-active pixels (pixels 401b) are measured to adjust the bias voltage. Therefore, it is possible to optimize the bias voltage according to the amount of the background light L3. Also, since the light emission control unit 11 adjusts the light emission current based on the pixel current average value, it is possible to maintain the ranging performance and reduce the power consumption.

[0108] (Sixth Embodiment) FIG. 13 is a diagram showing the circuit configurations of the light emitting device 10 and the light detection device 40 in the sixth embodiment. The same components as those in the fifth embodiment described above are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0109] The light detection device 40 according to the present embodiment further includes a non-active pixel current measurement circuit 406 and an active pixel current measurement circuit 407. The non-active pixel current measurement circuit 406 measures the non-active pixel current of the pixel 401b (non-active pixel) in the same manner as in the fourth embodiment. Also, the active pixel current measurement circuit 407 measures the active pixel current before and after the irradiation of the ranging light L1 in the same manner as in the fourth embodiment.

[0110] Furthermore, similar to the fourth embodiment, the light emission control unit 11 measures the reaction current of the light detection element 411 with respect to the distance measurement light L1, and adjusts the light emission current according to the difference between the reaction current and the target value V 14 and the light emission current is adjusted according to the difference therebetween.

[0111] Therefore, also in this embodiment, it is possible to optimize the bias voltage, maintain the distance measurement performance, and reduce the power consumption. In addition, the photon reaction of the light detection element 411 that cannot be detected by the inverter 414 of each pixel can also be detected.

[0112] (First Modification Example) FIG. 14 is a layout diagram showing an example of the arrangement configuration of the distance measurement system according to each of the above-described embodiments.

[0113] In the modification example shown in FIG. 14, a plurality of light detection elements 411 arranged two-dimensionally are provided on the first semiconductor substrate 501. The second semiconductor substrate 502 is bonded to the first semiconductor substrate 501 with copper pads. Thereby, the first semiconductor substrate 501 and the second semiconductor substrate 502 are formed as one semiconductor chip laminated on each other.

[0114] On the second semiconductor substrate 502, a readout circuit 512 for each light detection element 411 and a control unit 22 are provided. The readout circuit 512 includes, for example, a signal processing circuit 50 and the like in addition to a part of the light detection device 40 such as components other than the light detection element 411 of the pixel array 401 and the current measurement circuit 402.

[0115] In addition, a variable power supply circuit 513 is provided on a third semiconductor substrate 503 formed as a separate chip from the first semiconductor substrate 501 and the second semiconductor substrate 502. The variable power supply circuit 513 is provided with, for example, the remaining part of the light detection device 40 such as a bias voltage control unit 403 and a bias power supply 404.

[0116] Furthermore, in this modified example, a fourth semiconductor substrate 504 and a fifth semiconductor substrate 505, which are formed as separate chips from the first semiconductor substrate 501 and the second semiconductor substrate 502, are also provided. A drive circuit 514 is provided on the fourth semiconductor substrate 504. The drive circuit 514 is provided with components related to driving the light-emitting element 12 such as the above-described light-emitting control unit 11. On the other hand, a plurality of light-emitting elements 12 arranged two-dimensionally are provided on the fifth semiconductor substrate 505.

[0117] According to the present modified example described above, by arranging the light detection element 411 on an independent single semiconductor substrate, the ratio (Fill Factor) of the light-receiving area in the semiconductor substrate is improved. As a result, it becomes possible to detect photons incident on the light detection element 411 with a high probability. Further, since the light-emitting element 12 is also arranged on an independent single semiconductor substrate, the ratio of the light-emitting area in the semiconductor substrate is improved.

[0118] (Second Modified Example) FIG. 15 is a layout diagram showing another example of the arrangement configuration of the distance measurement system according to each of the above-described embodiments. The same components as those in the first modified example described above are denoted by the same reference numerals, and detailed description thereof is omitted.

[0119] In this modified example, a variable power supply circuit 513 is provided on the second semiconductor substrate 502. That is, all of the light detection device 40 is integrated on the second semiconductor substrate 502.

[0120] Therefore, according to the present embodiment, since the third semiconductor substrate 503 becomes unnecessary, the system can be miniaturized.

[0121] <Application Example to a Moving Body> The technology according to the present disclosure (this technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of moving body such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, a drone, a ship, or a robot.

[0122] FIG. 16 is a block diagram showing a schematic configuration example of a vehicle control system which is an example of a movement control system to which the technology according to the present disclosure can be applied.

[0123] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in FIG. 16, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside vehicle information detection unit 12030, an inside vehicle information detection unit 12040, and an integrated control unit 12050. Further, as a functional configuration of the integrated control unit 12050, a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (Interface) 12053 are illustrated.

[0124] The drive system control unit 12010 controls the operation of devices related to the drive system of the vehicle according to various programs. For example, the drive system control unit 12010 functions as a control device such as a driving force generation device for generating a driving force of the vehicle such as an internal combustion engine or a driving motor, a driving force transmission mechanism for transmitting the driving force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0125] The body system control unit 12020 controls the operation of various devices installed in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as a headlamp, a backlamp, a brake lamp, a turn signal, or a fog lamp. In this case, radio waves transmitted from a portable device substituting for a key or signals of various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these inputs of radio waves or signals and controls a door lock device, a power window device, lamps, etc. of the vehicle.

[0126] The vehicle exterior information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the vehicle exterior information detection unit 12030. The vehicle exterior information detection unit 12030 causes the imaging unit 12031 to capture an image outside the vehicle and receives the captured image. The vehicle exterior information detection unit 12030 may perform object detection processing or distance detection processing on objects such as people, vehicles, obstacles, signs, or characters on the road surface based on the received image.

[0127] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of received light. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. Also, the light received by the imaging unit 12031 may be visible light or non-visible light such as infrared light.

[0128] The vehicle interior information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the vehicle interior information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that images the driver, and the vehicle interior information detection unit 12040 may calculate the degree of driver fatigue or concentration based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0129] The microcomputer 12051 calculates control target values for the driving force generation device, the steering mechanism, or the braking device based on the vehicle interior and exterior information acquired by the vehicle exterior information detection unit 12030 or the vehicle interior information detection unit 12040, and can output a control command to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control for realizing functions of an ADAS (Advanced Driver Assistance System) including collision avoidance or shock mitigation of the vehicle, following driving based on the inter-vehicle distance, vehicle speed maintenance driving, collision warning of the vehicle, or lane departure warning of the vehicle.

[0130] Further, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving or the like in which it travels autonomously without relying on the driver's operation by controlling a driving force generator, a steering mechanism, a braking device, etc. based on information around the vehicle acquired by the vehicle exterior information detection unit 12030 or the vehicle interior information detection unit 12040.

[0131] Also, the microcomputer 12051 can output a control command to the body system control unit 12030 based on the vehicle exterior information acquired by the vehicle exterior information detection unit 12030. For example, the microcomputer 12051 can perform cooperative control for the purpose of anti-glare, such as controlling the headlamp according to the position of the preceding vehicle or oncoming vehicle detected by the vehicle exterior information detection unit 12030 and switching the high beam to the low beam.

[0132] The audio-visual output unit 12052 transmits at least one of an audio output signal and an image output signal to an output device capable of notifying information visually or auditorily to the vehicle occupants or to the outside of the vehicle. In the example of FIG. 16, the audio speaker 12061, the display unit 12062, and the instrument panel 12063 are illustrated as the output devices. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0133] FIG. 17 is a diagram showing an example of the installation position of the imaging unit 12031.

[0134] In FIG. 17, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0135] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided at positions such as the front nose, side mirrors, rear bumper, back door of the vehicle 12100, and the upper part of the front windshield inside the vehicle compartment. The imaging unit 12101 provided at the front nose and the imaging unit 12105 provided at the upper part of the front windshield inside the vehicle compartment mainly acquire images in front of the vehicle 12100. The imaging units 12102 and 12103 provided at the side mirrors mainly acquire images on the sides of the vehicle 12100. The imaging unit 12104 provided at the rear bumper or the back door mainly acquires images behind the vehicle 12100. The imaging unit 12105 provided at the upper part of the front windshield inside the vehicle compartment is mainly used for detecting a preceding vehicle or detecting pedestrians, obstacles, traffic lights, traffic signs, or lanes.

[0136] Note that FIG. 17 shows an example of the imaging ranges of the imaging units 12101 to 12104. The imaging range 12111 indicates the imaging range of the imaging unit 12101 provided at the front nose, the imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided at the side mirrors, respectively, and the imaging range 12114 indicates the imaging range of the imaging unit 12104 provided at the rear bumper or the back door. For example, by superimposing the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0137] At least one of the imaging units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the imaging units 12101 to 12104 may be a stereo camera composed of a plurality of imaging elements, or may be an imaging element having pixels for phase difference detection.

[0138] For example, based on the distance information obtained from imaging units 12101 to 12104, the microcomputer 12051 calculates the distance to each solid object within the imaging ranges 12111 to 12114 and the temporal change of this distance (relative speed with respect to the vehicle 12100). In particular, it can extract, as the leading vehicle, the closest solid object on the traveling path of the vehicle 12100 that is traveling in substantially the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or more). Further, the microcomputer 12051 can set the inter-vehicle distance to be secured in advance in front of the leading vehicle and perform automatic brake control (including follow-up stop control) and automatic acceleration control (including follow-up start control), etc. Thus, cooperative control for the purpose of automatic driving, etc., which autonomously travels without relying on the driver's operation, can be performed.

[0139] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 classifies and extracts solid object data regarding solid objects into motorcycles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other solid objects, and can use it for automatic avoidance of obstacles. For example, the microcomputer 12051 discriminates obstacles around the vehicle 12100 into obstacles visible to the driver of the vehicle 12100 and obstacles difficult to visually recognize. Then, the microcomputer 12051 determines the collision risk indicating the degree of risk of collision with each obstacle, and when the collision risk is equal to or higher than a set value and there is a possibility of collision, it can output an alarm to the driver via the audio speaker 12061 or the display unit 12062, or perform forced deceleration or avoidance steering via the drive system control unit 12010 to provide driving support for collision avoidance.

[0140] At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian exists in the captured images of the imaging units 12101 to 12104. Such recognition of a pedestrian is performed, for example, by a procedure of extracting feature points in the captured images of the imaging units 12101 to 12104 as infrared cameras, and a procedure of performing pattern matching processing on a series of feature points indicating the outline of an object to determine whether it is a pedestrian. When the microcomputer 12051 determines that a pedestrian exists in the captured images of the imaging units 12101 to 12104 and recognizes the pedestrian, the audio-video output unit 12052 controls the display unit 12062 to superimpose and display a rectangular outline for emphasizing the recognized pedestrian. Further, the audio-video output unit 12052 may control the display unit 12062 to display an icon or the like indicating a pedestrian at a desired position.

[0141] As described above, an example of a vehicle control system to which the technology according to the present disclosure can be applied has been described. The technology according to the present disclosure can be applied to, for example, the imaging unit 12031 among the configurations described above. Specifically, the imaging unit 21 can be applied to the imaging unit 12031. By applying the technology according to the present disclosure, a captured image with higher ranging accuracy can be obtained, so that safety can be improved.

[0142] Note that the present technology can adopt the following configuration. (1) A light emitting device that irradiates ranging light, and a light detection device that receives the reflected light of the ranging light, The light detection device, includes a pixel array in which a plurality of pixels each including a plurality of avalanche photodiodes that detect the reflected light are arranged, a current measurement circuit that measures the total pixel current of the pixel array, and a bias voltage control unit that controls a bias voltage supplied to the plurality of avalanche photodiodes using the detection result of the current measurement circuit. The distance measuring system, wherein the light emitting device includes a light emission control unit that controls the light quantity of the distance measuring light using the detection result of the current measurement circuit. (2) The current measurement circuit includes a resistance element connected in series to the plurality of avalanche photodiodes, a first operational amplifier that outputs the voltage of the resistance element, and a low-pass filter that smoothes the output value of the first operational amplifier. The bias voltage control unit includes a second operational amplifier that adjusts the bias voltage according to the difference between the pixel current average value obtained by smoothing by the low-pass filter and a preset first target value. The light emission control unit includes a third operational amplifier that adjusts the light quantity according to the difference between the pixel current average value and a preset second target value, in the distance measuring system according to (1). (3) The current measurement circuit includes a resistance element connected in series to the plurality of avalanche photodiodes, a first operational amplifier that outputs the voltage of the resistance element, an integration circuit that integrates the output value of the first operational amplifier, and a holding circuit that temporarily holds the integration value of the integration circuit. The bias voltage control unit includes a second operational amplifier that adjusts the bias voltage according to the difference between the held value of the holding circuit and a preset first target voltage. The light emission control unit includes a third operational amplifier that adjusts the light quantity according to the difference between the held value and a preset second target value, in the distance measuring system according to (1). (4) The light detection device further includes a constant voltage source connected to the plurality of avalanche photodiodes, and the current measurement circuit includes a resistance element connected to the plurality of avalanche photodiodes via the constant voltage source, and a first operational amplifier that outputs the voltage of the resistance element. The bias voltage control unit includes an integration circuit that integrates the output value of the first operational amplifier A holding circuit that temporarily holds the integration value of the integration circuit; A second operational amplifier that adjusts the bias voltage and the constant voltage source according to the difference between the holding value of the holding circuit and a preset first target voltage; The light emission control unit has a third operational amplifier that adjusts the light amount according to the difference between the holding value and a preset second target value, in the distance measurement system according to (1). (5) The constant voltage source A current mirror circuit having a first transistor connected in series to the plurality of avalanche photodiodes and a second transistor connected in series to the resistance element; A fourth operational amplifier that controls the first transistor and the second transistor according to the difference between the total pixel current and the output value of the second operational amplifier, in the distance measurement system according to (4). (6) The light detection device A plurality of switch elements that respectively switch the plurality of pixels to active pixels or non-active pixels; A non-active pixel current measurement circuit that measures a non-active pixel current indicating the sum of the pixel currents of the non-active pixels; An active pixel current measurement circuit that subtracts the detection value of the non-active pixel current measurement circuit from the detection value of the current measurement circuit to measure an active pixel current indicating the sum of the pixel currents of the active pixels, in the distance measurement system according to (1). (7) The active pixel current measurement circuit A first sampling and holding circuit that temporarily holds a first detection value detected by the active pixel current measurement circuit before irradiation of the distance measurement light; A second sampling and holding circuit that temporarily holds a second detection value detected by the active pixel current measurement circuit after irradiation of the distance measurement light; The light emission control unit has a first operational amplifier that outputs the difference between the first detection value and the second detection value; The ranging system according to (6), comprising: a second operational amplifier that adjusts the amount of light according to the difference between the output value of the first operational amplifier and a preset target value. (8) The plurality of avalanche photodiodes are provided on a first semiconductor substrate, A part of the light detection device excluding the plurality of avalanche photodiodes is provided on a second semiconductor substrate bonded to the first semiconductor substrate. The ranging system according to (1). (9) The plurality of avalanche photodiodes are provided on a first semiconductor substrate, All of the light detection device excluding the plurality of avalanche photodiodes is provided on a second semiconductor substrate bonded to the first semiconductor substrate. The ranging system according to (1). (10) The current measurement circuit is connected to the anode of each of the plurality of avalanche photodiodes. The ranging system according to (1). (11) The current measurement circuit is connected to the cathode of each of the plurality of avalanche photodiodes. The ranging system according to (1). (12) A pixel array in which a plurality of pixels each including a plurality of avalanche photodiodes for detecting reflected light of ranging light are arranged, A current measurement circuit that measures the total pixel current of the pixel array, A light detection device comprising: a bias voltage control unit that controls a bias voltage supplied to the plurality of avalanche photodiodes using a detection result of the current measurement circuit. (13) The current measurement circuit, A resistance element connected in series to the plurality of avalanche photodiodes, A first operational amplifier that outputs a voltage of the resistance element, A low-pass filter that smoothes the output value of the first operational amplifier, and has, The bias voltage control unit has a second operational amplifier that adjusts the bias voltage according to the difference between the pixel current average value obtained by smoothing by the low-pass filter and a preset first target value. The light detection device according to (12). (14) The current measurement circuit a resistance element connected in series to the plurality of avalanche photodiodes, a first operational amplifier that outputs the voltage of the resistance element, an integration circuit that integrates the output value of the first operational amplifier, and a holding circuit that temporarily holds the integration value of the integration circuit, The bias voltage control unit has a second operational amplifier that adjusts the bias voltage according to the difference between the holding value of the holding circuit and a preset first target voltage. The photodetection device according to (12). (15) The photodetection device further includes a constant voltage source connected to the plurality of avalanche photodiodes, The current measurement circuit a resistance element connected to the plurality of avalanche photodiodes via the constant voltage source, and a first operational amplifier that outputs the voltage of the resistance element, The bias voltage control unit an integration circuit that integrates the output value of the first operational amplifier, a holding circuit that temporarily holds the integration value of the integration circuit, and a second operational amplifier that adjusts the bias voltage and the constant voltage source according to the difference between the holding value of the holding circuit and a preset first target voltage. The photodetection device according to (12). (16) The constant voltage source has a current mirror circuit having a first transistor connected in series to the plurality of avalanche photodiodes and a second transistor connected in series to the resistance element, and a third operational amplifier that controls the first transistor and the second transistor according to the difference between the total pixel current and the output value of the second operational amplifier. The photodetection device according to (15). (17) a plurality of switch elements that respectively switch the plurality of pixels to active pixels or non-active pixels, a non-active pixel current measurement circuit that measures a non-active pixel current indicating the sum of the pixel currents of the non-active pixels, An active pixel current measurement circuit that measures an active pixel current indicating the total pixel current of the active pixels by subtracting the detection value of the non-active pixel current measurement circuit from the detection value of the current measurement circuit, and the light detection device according to (12). (18) The active pixel current measurement circuit A first sampling hold circuit that temporarily holds a first detection value detected by the active pixel current measurement circuit before irradiation of the ranging light, A second sampling hold circuit that temporarily holds a second detection value detected by the active pixel current measurement circuit after irradiation of the ranging light, and the light detection device according to (17). (19) The plurality of avalanche photodiodes are provided on a first semiconductor substrate, A part of the light detection device excluding the plurality of avalanche photodiodes is provided on a second semiconductor substrate bonded to the first semiconductor substrate, and the light detection device according to (12). (20) The plurality of avalanche photodiodes are provided on a first semiconductor substrate, All of the light detection device excluding the plurality of avalanche photodiodes are provided on a second semiconductor substrate bonded to the first semiconductor substrate, and the light detection device according to (12).

Description of reference numerals

[0143] 10: Light emitting device 11: Light emission control unit 40: Light detection device 112: Operational amplifier 113: Operational amplifier 401: Pixel array 402: Current measurement circuit 403: Bias voltage control unit 405: Bias power supply having a current detection function 406: Non-active pixel current measurement circuit 407: Active pixel current measurement circuit 412, 412a: Switching elements 421: Resistance element 422: Operational amplifier 423: LPF 424: Integrating circuit 425: Holding circuit 431: Operational amplifier 451: First transistor 452: Second transistor 453: Operational amplifier 472: First sampling hold circuit 473: Second sampling hold circuit

Claims

1. A light emitting device that irradiates ranging light, A light detection device that receives the reflected light of the ranging light, and is provided with, The light detection device, A pixel array in which a plurality of pixels each including a plurality of avalanche photodiodes for detecting the reflected light are arranged, A current measurement circuit that measures the total pixel current of the pixel array, A bias voltage control unit that controls a bias voltage supplied to the plurality of avalanche photodiodes using the detection result of the current measurement circuit, and has, The light emitting device has a light emission control unit that controls the light amount of the ranging light using the detection result of the current measurement circuit, a ranging system.

2. The current measurement circuit, A resistance element connected in series to the plurality of avalanche photodiodes, A first operational amplifier that outputs the voltage of the resistance element, A low-pass filter that smoothes the output value of the first operational amplifier, and has, The bias voltage control unit has a second operational amplifier that adjusts the bias voltage according to the difference between the pixel current average value obtained by smoothing by the low-pass filter and a preset first target value, The light emission control unit has a third operational amplifier that adjusts the light amount according to the difference between the pixel current average value and a preset second target value, the ranging system according to claim 1.

3. The current measurement circuit, A resistance element connected in series to the plurality of avalanche photodiodes, A first operational amplifier that outputs the voltage of the resistance element, An integration circuit that integrates the output value of the first operational amplifier, A holding circuit that temporarily holds the integration value of the integration circuit, and has, The bias voltage control unit has a second operational amplifier that adjusts the bias voltage according to the difference between the holding value of the holding circuit and a preset first target voltage. The light emission control unit has a third operational amplifier that adjusts the light quantity according to the difference between the holding value and a preset second target value. The distance measurement system according to claim 1.

4. The light detection device further has a constant voltage source connected to the plurality of avalanche photodiodes. The current measurement circuit A resistance element connected to the plurality of avalanche photodiodes via the constant voltage source, A first operational amplifier that outputs the voltage of the resistance element, and has. The bias voltage control unit An integration circuit that integrates the output value of the first operational amplifier, A holding circuit that temporarily holds the integration value of the integration circuit, A second operational amplifier that adjusts the bias voltage and the constant voltage source according to the difference between the holding value of the holding circuit and a preset first target voltage, and has. The light emission control unit has a third operational amplifier that adjusts the light quantity according to the difference between the holding value and a preset second target value. The distance measurement system according to claim 1.

5. The constant voltage source A current mirror circuit having a first transistor connected in series to the plurality of avalanche photodiodes and a second transistor connected in series to the resistance element, A fourth operational amplifier that controls the first transistor and the second transistor according to the difference between the total pixel current and the output value of the second operational amplifier. The distance measurement system according to claim 4.

6. The light detection device A plurality of switch elements that respectively switch the plurality of pixels to active pixels or non-active pixels, A non-active pixel current measurement circuit for measuring a non-active pixel current indicating the sum of the pixel currents of the non-active pixels, An active pixel current measurement circuit for measuring an active pixel current indicating the sum of the pixel currents of the active pixels by subtracting the detection value of the non-active pixel current measurement circuit from the detection value of the current measurement circuit, The ranging system according to claim 1, further comprising: **Claim 7** The active pixel current measurement circuit, A first sampling and holding circuit for temporarily holding a first detection value detected by the active pixel current measurement circuit before irradiation of the ranging light, A second sampling and holding circuit for temporarily holding a second detection value detected by the active pixel current measurement circuit after irradiation of the ranging light, The ranging system according to claim 6, comprising: The light emission control unit includes a first operational amplifier that outputs a difference between the first detection value and the second detection value, A second operational amplifier that adjusts the light amount according to a difference between an output value of the first operational amplifier and a preset target value, The ranging system according to claim 6. **Claim 8** The plurality of avalanche photodiodes are provided on a first semiconductor substrate, A part of the light detection device excluding the plurality of avalanche photodiodes is provided on a second semiconductor substrate bonded to the first semiconductor substrate, The ranging system according to claim 1. **Claim 9** The plurality of avalanche photodiodes are provided on a first semiconductor substrate, All of the light detection device excluding the plurality of avalanche photodiodes are provided on a second semiconductor substrate bonded to the first semiconductor substrate, The ranging system according to claim 1. **Claim 10** The current measurement circuit is connected to an anode of each of the plurality of avalanche photodiodes, The ranging system according to claim 1. **Claim 11** The distance measurement system according to claim 1, wherein the current measurement circuit is connected to the cathode of each of the plurality of avalanche photodiodes.

12. A pixel array in which a plurality of pixels each including a plurality of avalanche photodiodes for detecting reflected light of distance measurement light are arranged, A current measurement circuit that measures the total pixel current of the pixel array, A bias voltage control unit that controls a bias voltage supplied to the plurality of avalanche photodiodes using a detection result of the current measurement circuit, The current measurement circuit includes A resistance element connected in series to the plurality of avalanche photodiodes, A first operational amplifier that outputs a voltage of the resistance element, A low-pass filter that smoothes an output value of the first operational amplifier, The bias voltage control unit includes a second operational amplifier that adjusts the bias voltage according to a difference between an average pixel current value obtained by smoothing by the low-pass filter and a preset first target value, an optical detection device.

13. A pixel array in which a plurality of pixels each including a plurality of avalanche photodiodes for detecting reflected light of distance measurement light are arranged, A current measurement circuit that measures the total pixel current of the pixel array, A bias voltage control unit that controls a bias voltage supplied to the plurality of avalanche photodiodes using a detection result of the current measurement circuit, The current measurement circuit includes A resistance element connected in series to the plurality of avalanche photodiodes, A first operational amplifier that outputs a voltage of the resistance element, An integration circuit that integrates an output value of the first operational amplifier, A holding circuit that temporarily holds an integration value of the integration circuit, The bias voltage control unit has a second operational amplifier that adjusts the bias voltage according to the difference between the holding value of the holding circuit and a preset first target voltage. A photodetection device.

14. A pixel array in which a plurality of pixels each including a plurality of avalanche photodiodes for detecting reflected light of ranging light are arranged, A current measurement circuit that measures the total pixel current of the pixel array, A bias voltage control unit that controls a bias voltage supplied to the plurality of avalanche photodiodes using the detection result of the current measurement circuit, A constant voltage source connected to the plurality of avalanche photodiodes, The current measurement circuit, A resistance element connected to the plurality of avalanche photodiodes via the constant voltage source, A first operational amplifier that outputs the voltage of the resistance element, The bias voltage control unit, An integration circuit that integrates the output value of the first operational amplifier, A holding circuit that temporarily holds the integration value of the integration circuit, A second operational amplifier that adjusts the bias voltage and the constant voltage source according to the difference between the holding value of the holding circuit and a preset first target voltage. A photodetection device.

15. The constant voltage source, A current mirror circuit having a first transistor connected in series to the plurality of avalanche photodiodes and a second transistor connected in series to the resistance element, A third operational amplifier that controls the first transistor and the second transistor according to the difference between the total pixel current and the output value of the second operational amplifier. The photodetection device according to claim 14.

16. A plurality of switch elements that respectively switch the plurality of pixels to active pixels or non-active pixels, A non-active pixel current measurement circuit that measures a non-active pixel current indicating the sum of the pixel currents of the non-active pixels, and an active pixel current measurement circuit that measures an active pixel current indicating the sum of the pixel currents of the active pixels by subtracting the detection value of the non-active pixel current measurement circuit from the detection value of the current measurement circuit. The optical detection device according to claim 12 further comprises the same.

17. The active pixel current measurement circuit, a first sampling hold circuit that temporarily holds a first detection value detected by the active pixel current measurement circuit before irradiation of the ranging light, and a second sampling hold circuit that temporarily holds a second detection value detected by the active pixel current measurement circuit after irradiation of the ranging light. The optical detection device according to claim 16 has the same.

18. The plurality of avalanche photodiodes are provided on a first semiconductor substrate, and a part of the optical detection device excluding the plurality of avalanche photodiodes is provided on a second semiconductor substrate joined to the first semiconductor substrate. The optical detection device according to claim 12 has the same.

19. The plurality of avalanche photodiodes are provided on a first semiconductor substrate, and all of the optical detection device excluding the plurality of avalanche photodiodes are provided on a second semiconductor substrate joined to the first semiconductor substrate. The optical detection device according to claim 12 has the same.

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