PHOTO DETECTION DEVICE, ELECTRONICS DEVICE AND PHOTO DETECTION METHOD

Abstract

Photo detection device (1), comprising: a photodetection element (7), wherein the photodetection element (7) is an avalanche photodiode; a first reset circuit (3) which is configured to select whether to set a one-way resistance between a first voltage node and a terminal of the photodetection element (7) to a first value; a second reset circuit (4) configured to select whether the input resistance is to be set to a second, smaller value than the first value; and a control circuit (5) that is configured: to set the input resistor to the first value by the first reset circuit (3) after the photodetection element (7) detects light; and to set the input resistance to the second value by the second reset circuit (4), based on a voltage at the terminal of the photodetection element (7), after the first reset circuit (3) selects to set the input resistance to the first value.

Description

AREA

[0001] Embodiments of the present disclosure relate to a photodetection device, an electronic device and a photodetection method. BACKGROUND

[0002] An avalanche photodiode (APD) is a type of photodetection device that converts received light into an electronic signal. Specifically, when operating in Geiger mode, the APD is capable of detecting a single photon. However, although the APD exhibits higher sensitivity in Geiger mode, its operating state changes after detecting the photon, meaning it may fail to detect light at high sensitivity. Therefore, a quench circuit is required to reset the APD. Quench circuits are classified as either passive or active. A passive quench circuit performs the reset by applying a current to the APD through a resistor connected in series. While passive quench circuits have a simple circuit configuration, they are prone to slow operation.In contrast, the active quench circuit forcibly introduces current to the APD by using a transistor or similar device that can perform a reset operation at high speeds.

[0003] However, the conventional active quench circuit has a problem: if the APD detects light while current is being supplied to reset it, the current flowing to the APD cannot be controlled, potentially causing the APD to generate excessive heat and fail. Furthermore, if a large amount of current flows to the APD, it emits light, which can lead to crosstalk and subsequent current flow to other APDs in the vicinity.

[0004] Document EP 3 419 168 A1 describes an avalanche diode arrangement comprising an avalanche diode coupled to a first voltage terminal and a first node, a latch comparator with a first input coupled to the first node, a second input for receiving a reference voltage (VREF) and an enable input for receiving a comparator enable signal (CLK), and an erase circuit coupled to the first node.

[0005] Document JP 2015-117 970 A describes a radar system comprising a light source, a pixel, and a light detection control section. The light source is installed within the radar system and emits light. The pixel includes a SPAD (Single Photon Avalanche Diode) installed within the radar system, which detects the light reflected from the object. The light detection control section initiates the operation of the SPAD according to a timer when internal stray light, generated by the reflection of light emitted by the light source within the radar system, strikes the SPAD.

[0006] Document JP 2018-179 732 A describes a detection element that allows, when a photon is input while a terminal voltage Vacross is equal to or higher than a breakdown voltage, a detection current to flow and the terminal voltage Vd to drop to the breakdown voltage.

[0007] An output circuit outputs a digital pulse corresponding to the detection element's response to the photon input. A recharge circuit, upon receiving the digital pulse, performs a recharge to restore the detection element's terminal voltage Vacross to its breakdown voltage or higher. The recharge circuit varies the rate of change of the detection element's terminal voltage Vacross during recharging, and optionally the recharge time, according to a sensitivity setting value Cas and an external control signal. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a circuit diagram of a photodetection device according to a first embodiment; Fig. Figure 2 is a circuit diagram showing a first modification example of the photodetection device 1. Fig. 1 shows; Fig. Figure 3 is a voltage waveform diagram of the photodetection device 1 of Fig. 1; Fig. 4A is an equivalent circuit in the case where a first reset circuit switches on a first switch; Fig. 4B is an equivalent circuit in the case where a second reset circuit turns on a second switch; Fig. Figure 5 is a voltage waveform diagram in the case where an APD detects light while a current flows from the first reset circuit to a cathode of the APD; Fig. Figure 6 is a voltage waveform diagram in the case where the APD detects light while a current flows from the second reset circuit to the cathode of the APD; Fig. Figure 7 is a circuit diagram in which a first level converter and a second level converter are connected to the photodetection device 1 of Fig. 2 have been added; Fig. Figure 8 is a schematic layout diagram of a photodetection device equipped with four APDs and four active quench circuits; Fig. Figure 9 is a layout diagram of a multitude of SiPMs and active quench circuits arranged on a semiconductor substrate; Fig. Figure 10A is a block diagram which schematically shows the configuration of an electronic device which is equipped with a light receiving unit which is implemented with the photodetection device according to the present embodiment; Fig. 10B is a block diagram which schematically shows the configuration of a modification example of the electronic device of Fig. 10A indicates; Fig. Figure 11 is a schematic sectional view showing an example in which a light receiving unit and a signal processing unit are integrated into the electronic device 21. Fig. 10A or Fig. 10B are arranged on a semiconductor substrate; and Fig. Figure 12 is a circuit diagram of a photodetection device according to a second embodiment. DETAILED DESCRIPTION

[0008] The problem addressed by the invention is solved by the subject matter of the independent claims. Examples and technical descriptions of devices, products, and / or methods in the description and / or drawings that are not covered by the claims are not presented as embodiments of the invention, but rather as background information or examples useful for understanding the invention.A photodetection device according to an example has a photodetection element, a first reset circuit configured to select whether to set an on-resistance between a first voltage node and a terminal of the photodetection element to a first value, a second reset circuit configured to select whether to set the on-resistance to a second, smaller value than the first value, and a control circuit configured to set the on-resistance to the first value by the first reset circuit after the photodetection element detects light, and to set the on-resistance to the second value by the second reset circuit after the first reset circuit selects to set the on-resistance to the first value.

[0009] The following sections describe embodiments of a photodetection device and an electronic device, as well as a distance measurement method, with reference to the accompanying drawings. The following descriptions primarily focus on one main configuration of the photodetection device and the electronic device. However, the photodetection device and the electronic device may have other configurations and functions that are not shown or explained. First embodiment

[0010] Fig. Figure 1 is a circuit diagram of a photodetection device 1 according to a first embodiment. The photodetection device 1 of Fig. 1 is connected to a photodetection element 2, a first reset circuit 3, a second reset circuit 4, and a control circuit 5. The first reset circuit 3, the second reset circuit 4, and the control circuit 5 configure an active quench circuit 6. The active quench circuit 6 performs a forced reset operation on the photodetection element 2 after the photodetection element 2 detects light.

[0011] The photodetection element 2, for example, is an APD 7. A reverse bias voltage, higher than the breakdown voltage of the APD 7, is applied to the APD 7 and driven in a region known as the Geiger mode. The gain of the APD 7 in Geiger mode is on an extremely high order of 10⁻⁶. 5 up to 10 6This makes it possible to measure extremely weak light from a single photon. The following mainly explains an example in which the APD 7 is used as the photodetection element 2.

[0012] In photo detection unit 1 of Fig. 1. A first reset circuit 3 and a second reset circuit 4 are connected in parallel between a first voltage node Vhi and a cathode of APD 7. A second voltage node Vlow is connected to an anode of APD 7. The second voltage node Vlow is one voltage node lower than the first voltage node Vhi.

[0013] The first reset circuit 3 selects whether the on-resistance between the first voltage node Vhi and an end (a terminal, such as the cathode of the APD 7) of the photodetection element 2 is to be set to a first value. The first reset circuit 3 can be configured by connecting a current source 3a and a first switch 3b in series. The current source 3a outputs a predetermined current. The current source 3a is designed to restrict the current from flowing to the cathode of the APD 7. The first switch 3b selects whether the current output from the current source 3a is to be supplied to the cathode of the APD 7. When the first switch 3b is on, the current output from the current source 3a passes through the first switch 3b to flow to the cathode of the APD 7. The on-resistance of the first reset circuit 3 is the impedance of the first reset circuit 3 when the first switch 3b is on.

[0014] The second reset circuit 4 selects whether the on-resistance between the first voltage node Vhi and one end (cathode of APD 7) of the photodetection element 2 is to be set to a second value, smaller than the first value. The second reset circuit has a second switch 4. When the second switch 4a is on, a current from the first voltage node Vhi passes through the second switch 4a to flow to the cathode of APD 7. The on-resistance of the second reset circuit 4 is the impedance of the second reset circuit 4 when the second switch 4a is on. The second value, which is the on-resistance of the second reset circuit 4, is smaller than the first value, which is the on-resistance of the first reset circuit 3.Therefore, the current flowing to the cathode of APD 7 from the second reset circuit 4 when the second switch 4a is on is greater than the current flowing to the cathode of APD 7 from the first reset circuit 3 when the first switch 3b is on. In the present embodiment, the duration during which the on-resistance of the second reset circuit 4 becomes the second value is set longer than the duration during which the on-resistance of the first reset circuit 3 becomes the first value.

[0015] After the APD 7 detects light, the control circuit 5 sets the on-resistance between the first voltage node Vhi and the cathode of the APD 7 to the first value using the first reset circuit 3, and then sets the on-resistance to the second value using the second reset circuit 4. More specifically, after the APD 7 detects light, the control circuit 5 holds one end (the cathode) of the APD 7 at a first value, then sets the on-resistance to the first value using the first reset switch 3, and then sets the on-resistance to the second value using the second reset circuit 4. Since the on-resistance is lower, the current flows more easily; by switching the on-resistance between the first voltage node Vhi and the cathode of the APD 7, the current flowing to the cathode of the APD 7 can be varied.As described above, the control circuit 5 directs the limited current from the first reset circuit 3 to the cathode of the APD 7 in a reset operation after the APD 7 detects light, and then directs a large current from the second reset circuit 4 to the cathode of the APD 7.

[0016] Fig. Figure 2 is a circuit diagram showing a first modification example of the photodetection device 1. Fig. Figure 1 shows the photodetection device 1 of Fig. 2 shows a specific configuration of each component of the photodetection device 1 of Fig. 1 on. In the photodetection device 1 of Fig. 2 are the first switch 3b in the first reset circuit 3 and the second switch 4a in the second reset circuit 4, configured with transistors Q1 and Q2 respectively. The gate voltages of transistors Q1 and Q2 are controlled by the control circuit 5. Furthermore, the control circuit 5 has Fig. 2 a quench control unit (voltage holding circuit) 5a. Furthermore, the photodetection device 1 of Fig. 2 a third switch 8, which is switched on and off by the quench control circuit 5a. In Fig. Figure 2 shows an example in which the third switch 8 is configured with a MOS transistor Q3.

[0017] When the APD 7 detects light, the quench control circuit 5a maintains a cathode voltage of the APD 7 at a predetermined voltage VAQ for a predetermined duration. More specifically, after the APD 7 detects light, the quench control circuit 5a maintains one end (cathode) of the APD 7 at the first voltage for a predetermined duration in response to one end of the APD 7 being set to the second voltage, which differs from the first voltage. The third switch 8 is connected between the cathode of the APD 7 and the third voltage node VAQ. The third voltage node VAQ can be, for example, a ground voltage or any voltage other than ground. The quench control circuit 5a turns on the third switch 8 when the cathode voltage of the APD 7 drops to a predetermined first threshold voltage Vth1.When the third switch 8 is turned on, the cathode voltage of the APD 7 is kept at the voltage of the third voltage node VAQ.

[0018] Fig. Figure 3 is a voltage waveform diagram of the photodetection device 1 of Fig. 1. In Fig. 3 is the abscissa, time, and the ordinate, the voltage value. Fig. Figure 3 shows a state prior to time t1 in which the APD 7 does not detect any light, while the cathode voltage of the APD 7 is approximately equal to the voltage Vhi of the first voltage node Vhi.

[0019] When APD 7 detects light at time t1, electron-hole pairs are generated within APD 7 to cause a current to flow into APD 7. Consequently, the cathode voltage of APD 7 begins to decrease. When the cathode voltage of APD 7 drops to a predetermined first threshold voltage Vth1 (time t2), the third switch 8 is activated, causing the cathode voltage of APD 7 to drop to the voltage VAQ of the third voltage node (time t3).

[0020] The quench control circuit 5a keeps the third switch 8 in the on state until time t4, so that the cathode voltage of the APD 7 is kept at the voltage VAQ.

[0021] At time t4, the quench control circuit 5a switches off the third switch 8 and the control circuit 5 switches on the third switch 3b in the first reset circuit 3. This is analogous to an equivalent circuit of Fig. As shown in Figure 4A, the current from the current source 3a in the first reset circuit 3 flows to the cathode of the APD 7 via the first switch 3b, so that the cathode voltage of the APD 7 begins to rise gradually. Since the current output from the current source 3a is limited, the current flowing from the cathode of the APD 7 via the first reset circuit 3 is also limited, so that the cathode voltage of the APD 7 rises smoothly.

[0022] When the cathode voltage of the APD 7 reaches a predetermined second threshold voltage Vth2 (≥ Vth1) (time t5), the control circuit 5 switches off the first switch 3b in the first reset circuit 3 and switches on the second switch 4a. This is analogous to the equivalent circuit of Fig. As shown in Figure 4B, a large current flows through the cathode of APD 7 via the second switch 4a in the second reset circuit 4. Therefore, the cathode voltage of APD 7 rises rapidly, reaching the saturation voltage at time t6. As shown in Figure 4B, a large current flows through the cathode of APD 7 via the second switch 4a in the second reset circuit 4. Therefore, the cathode voltage of APD 7 rises rapidly, reaching the saturation voltage at time t6. Fig. As shown in Figure 3, the control circuit 5 outputs a pulse signal with a pulse width from time t2 to time t5.

[0023] In the present embodiment, the duration during which the first reset circuit 3 switches on the first switch 3b is referred to as the first reset, and the duration during which the second reset circuit 4 switches on the second switch 4a is referred to as the second reset.

[0024] There may be a case in which the APD 7 detects light during an initial reset period, during which a current flows from the first reset circuit 3 to the cathode of the APD 7. In this case, the voltage waveform diagram is as shown in Fig. 5 shown. The period from time t4 to time t5 in Fig. Time 5 is the first reset period, during which a current flows from the first reset circuit 3 to the cathode of APD 7. If APD 7 detects light during this period, electron-hole pairs are generated in APD 7 to cause a current to flow, thus decreasing the cathode voltage of APD 7 (time t4a). However, since the current flowing through the first reset circuit 3 is limited by the current source 3, there is no possibility of a rapid increase in the current flowing through APD 7. If APD 7 does not detect light, the current from the first reset circuit 3 flows to the cathode of APD 7, so that the cathode voltage of APD 7 begins to rise again. When the cathode voltage of the APD 7 reaches the predetermined second threshold voltage Vth2, the control circuit 5 switches off the first switch 3b in the first reset circuit 3 and switches on the second switch 4a in the second reset circuit 4.Accordingly, a large current flows from the second reset circuit 4 to the cathode of the APD 7, so that the cathode voltage of the APD 7 rises rapidly.

[0025] Furthermore, there may be a case where the APD 7 detects light during a second reset period, during which a large current flows from the second reset circuit to the cathode of the APD 7. The voltage waveform diagram in this case is as shown in Fig. Shown in 6. Currently t5 in Fig. 6. The second switch 4a in the second reset circuit 4 is activated, causing a large current to flow from the second reset circuit 4 to the anode of the APD 7. If the APD 7 detects light at time t5 in this state, electrode hole pairs are generated in the APD 7 to cause a current to flow in the APD 7, so that the cathode voltage of the APD 7 begins to decrease. However, when the cathode voltage of the APD 7 drops to the predetermined first threshold voltage Vth1 (time t5b), the quench control circuit 5a activates the third switch 8, so that the cathode voltage of the APD 7 is held at the predetermined voltage VAQ for a predetermined duration (time t5b to t5c). Then, at time t5c, the first switch 3b in the first reset circuit 3 switches on, and then at time t5d, the second switch 5a in the second reset circuit 4 switches on.

[0026] As described above, if the APD 7 detects light during the period in which a large current flows from the second reset circuit 4 to the cathode of the APD 7, the quench control circuit 5a switches on at the moment when the cathode voltage of the APD 7 drops to a predetermined threshold voltage. Therefore, there is no possibility of an uncontrollably large current flowing to the APD 7, thus protecting the APD 7 from damage due to heat generation and reducing crosstalk due to light emission from the APD 7.

[0027] The cathode voltage of APD 7 in the state where APD 7 does not detect light is considerably higher than the gate voltage of the MOS transistor that configures the first switch 3b and the second switch 4a. Therefore, voltage level conversion may be necessary if the control circuit 5 controls the gate voltage of the MOS transistor for the first switch 3b and the second switch 4a based on the cathode voltage of APD 7.

[0028] Fig. Figure 7 is a circuit diagram in which a first level converter 11 and a second level converter 12 are connected to the photodetection device 1 of Fig. Two additional components are added. A control signal for the first switch 3b, output from control circuit 5, is input to the gate of MOS transistor Q1 via the first level shifter 11. Similarly, a control signal for the second switch 4a, output from control circuit 5, is input to the gate of MOS transistor Q2 via the second level shifter 12. The first level shifter 11 and the second level shifter 12 perform voltage control to reduce the voltage from the cathode voltage level of APD 7 to the gate voltage level of MOS transistors Q1 and Q2.

[0029] The photodetection equipment 1 of Fig. 1, Fig. 2 and Fig. Figure 7 specifies the minimum configuration for light detection. In fact, the photodetection devices are 1 of Fig. 1, Fig. 2 and Fig. 7 is often used in a state where a plurality of the photodetection devices 1 are arranged in a one-dimensional direction or a two-dimensional direction. Furthermore, a semiconductor IC in which a plurality of the photodetection devices 1 are arranged in a one-dimensional direction can be used in a one-dimensional or two-dimensional direction. Fig. 1, Fig. 2 and Fig. 7 are integrated, are manufactured.

[0030] Fig. Figure 8 is a schematic layout diagram of a photodetection device 1 equipped with four APDs 7 and four active quench circuits (labeled AQ in the diagram) 6. The active quench circuit 6 is a circuit that controls the first reset switch 3, the second reset switch 4, and the control circuit 5 in the photodetection devices 1 of Fig. 1, Fig. 2 and Fig. 7 is included.

[0031] In Fig. 8 configure four APDs, 7 a SiPM (silicon photomultiplier), 13 and configure four active quench circuits, 6 an active quench circuit group, 14. In Fig. 8 Two active quench circuits 6 are arranged in an X-direction and also in a Y-direction, adjacent to the SiPM 13, which has two APDs 7 arranged in the X-direction and also in the Y-direction. However, any number of APDs 7 in the SiPM 13 can be arranged in any way, and the SiPM 13 and the active quench circuits 6 can also be arranged in any positional relationship.

[0032] In fact, a majority of SiPMs are 13 and active quench circuits are 6, such as those of Fig. 8, arranged on a semiconductor substrate that can be manufactured in one step. Fig. Figure 9 is a layout diagram of a plurality of SiPMs 13 and active quench circuit groups (APDs) 14 arranged on a semiconductor substrate. As shown, a plurality of groups, each comprising a SiPM 13 and an active quench circuit group 14, are arranged in the X and Y directions.

[0033] The photodetection device 1 according to the present embodiment can be implemented in an electronic device for performing ToF (time of flight) type distance measurement. Fig. Figure 10A is a block diagram schematically showing the configuration of an electronic device 21, which is equipped with a light receiving unit (light detector) 24, which is implemented with the photodetection device 1 according to the present embodiment. The electronic device 21 of Fig. 10A is equipped with a floodlight unit 22, a light control unit 23, a light receiving unit 24, a signal processing unit 25, and an image processing unit 26. Of these, the floodlight unit 22, the light control unit 23, the light receiving unit 24, and the signal processing unit 25 configure a distance measuring device 27. At least part of the electronic device 21 of Fig. 10A can be configured with one or more semiconductor ICs (integrated circuits). For example, the signal processing unit 25 and the image processing unit 26 can be integrated into a single semiconductor chip, or the light receiving unit 24 can also be integrated into this semiconductor chip. Furthermore, the floodlight unit 22 can also be integrated into this semiconductor chip.

[0034] The floodlight unit 22 emits first light as floodlight. The first light is, for example, a laser beam in a predetermined frequency band. The laser beam is coherent light with constant fiber and frequency. The floodlight unit 22 emits pulsed first light intermittently in a predetermined cycle. The cycle in which the floodlight unit 22 emits the first light as floodlight is a time period equal to or longer than the time required for the distance measuring device 27 to measure a distance based on a pulse of the first light.

[0035] The floodlight unit 22 comprises an oscillator 31, a floodlight controller 32, a light source 33, a first driver 34, and a second driver 35. The oscillator 31 generates an oscillation signal corresponding to the cycle of emitting the first light as floodlight. The first driver 34 intermittently supplies current to the light source 33 synchronously with the oscillation signal. The light source 33 intermittently emits the first light based on the current from the first driver 34. The light source 33 can be a laser element emitting a single laser beam or a laser unit emitting multiple laser beams. The floodlight controller 32 controls the second driver 35 synchronously with the oscillation signal. The second driver 35 provides a drive signal to the light control unit 23 synchronously with the oscillation signal in response to a command from the floodlight controller 32.

[0036] The light control unit 23 controls the direction of movement of the first light emitted from the light source 33. In addition, the light control unit 23 controls the direction of movement of the received second light.

[0037] The light control 23 has a first lens 41, a beam splitter 42, a second lens 43, a half-mirror 44 and a scan mirror 45.

[0038] The first lens 41 collects the first light emitted from the floodlight unit 22 and directs it to the beam splitter 42. The beam splitter 42 divides the first light from the first lens 41 into two directions and directs them separately to the second lens 43 and the half-mirror 44. The second lens 43 directs the light separated by the beam splitter 42 to the light receiver 24. The reason for directing the first light to the light receiver 24 is that the light receiver 24 detects the floodlight time.

[0039] The half-mirror 44 directs the split light from the beam splitter 42 to the scanning mirror 45. Furthermore, the half-mirror 44 reflects secondary light, including reflected light incident on the electronic device 21, towards the light receiving unit 24.

[0040] The scan mirror 45 rotates its surface synchronously with a drive signal from the second driver 35 in the floodlight unit 22. In this way, the scan mirror 45 controls the reflection direction of the split light (first light) incident on the surface of the scan mirror 45 after passing through the half-mirror 44. By controlling the rotation of the surface of the half-mirror 24 at a constant cycle, it is possible to scan the first light emitted from the light control unit 23 at least in one dimension. By providing two waves in two directions to rotate the surface of the mirror, it is also possible to scan the first light emitted from the light control unit 23 in a two-dimensional direction. Fig. Figure 10A shows an example of scanning the first light emitted from the electronic device 21 as a floodlight in an X direction and a Y direction using the scanning mirror 45.

[0041] In the case where an object 10, such as a person or a body, is present in a scan area illuminated by the first light emitted from the electronic device 21, the first light is reflected by the object 10. At least a portion of the reflected light propagates in the reverse direction through the passage, almost identically to that of the first light, and strikes the scan mirror 45 in the light control unit 23. Although the mirror surface of the scan mirror 45 rotates at a predetermined cycle, since a laser beam propagates at the speed of light, the reflected light from the object 10 strikes the mirror surface while there is almost no change in the angle of the mirror surface of the scan mirror 45. The reflected light from the object 10 striking the mirror surface is reflected by the half-mirror 44 and received by the light receiving unit 24.

[0042] The light receiving unit 24 comprises a light detector 51, an amplifier 52, a third lens 53, a photosensor 54, and an A / D converter 55. The light detector 51 receives light split by the beam splitter 42 and converts it into an electronic signal. The light detector 51 can detect the moment the first light reaches the floodlight. The amplifier 51 amplifies the electronic signal output by the light detector 51.

[0043] The third lens 53 forms an image of the light reflected by the semi-mirror 44 onto the photosensor 54. The photosensor 54 receives the second light and converts it into an electronic signal. The photosensor 54 has the SiPM (silicon photomultiplier) 13 described above.

[0044] The A / D converter 55 samples the electronic signal output from the photosensor 54 at a predetermined sampling rate for A / D conversion in order to generate a digital signal.

[0045] The signal processing unit 25 measures the distance to the object 10, which reflected the first light, and stores a digital signal according to the second light in a storage unit (memory) 61. The signal processing unit 25 comprises the storage unit 61, a distance measuring unit 62, and a storage control unit 63.

[0046] The distance measuring unit 62 measures a distance to object 10 based on the initial light and reflected light. More specifically, the distance measuring unit 62 measures a distance to object 10 based on the time difference between the illumination time of the initial light and the reception time of the reflected light contained in the second light received by the photosensor 54. In other words, the distance measuring unit 62 measures the distance based on the following expression (1). The processing operation of the distance measuring unit can be performed by a processor, a processing circuit, etc. Distance = speed of light × (time of reception of reflected light − time of floodlighting of first light)

[0047] The “reception time of reflected light” in expression (1) is more precisely a reception time of reflected light at a peak position. The distance measuring unit 62 detects the peak position of the reflected light contained in the second light based on a digital signal generated by the A / D converter 55.

[0048] The electronic equipment 21 of Fig. Figure 10A shows an example in which light reflected from object 10 is reflected by the scan mirror 45 and the half-mirror 44 to be directed to the light receiving unit 24. When the photosensor 54, which has a plurality of SiPMs 13 arranged in a two-dimensional direction, as in Fig. As shown in 9, it can be used on an electronic device 21 as in Fig. 10B is shown and applied. In the electronics unit 21 of Fig. In 10B, the light reflected from the object 10 is not directed to the light receiving unit 24 after being reflected through the scan mirror 45 and the half-mirror 44, but is directed directly to the photosensor 54 via the third lens 53.

[0049] At least part of the electronic equipment 21 of Fig. 10A or Fig. 10B can be configured with one or a variety of semiconductor ICs. Fig. Figure 11 is a schematic sectional view showing an example in which the light receiving unit 24 and the signal processing unit 25 are located in the electronic device 21 of Fig. 10A and Fig. 10B are arranged on a semiconductor substrate 71. On the semiconductor substrate 71 of Fig. 11 are provided for a first die 72 and a second die 73. On the first die 72, the photosensor 54 is located in the light receiving unit 24. Fig. 10A or Fig. 10B arranged. The photosensor 54 is, as in Fig. Figure 8 shows a multiplicity of SiPMs 13 and active quench circuit groups arranged in the X and Y directions. On the second figure 73, the A / D converter (ADC) 55 is located in the light receiving unit 24 and the signal processing unit 25 is located in the light receiving unit 24. Fig. 10A or Fig. 10B arranged. Pads 74 on the first die 72 and pads 75 on the second die 73 are connected with bonding wires 76.

[0050] The floodlight unit 22, the light control unit 23, etc. can be mounted on a semiconductor substrate 71 of Fig. 11 can be built. Or the floodlight unit 22, the light control unit 23, etc. can be built on a different substrate, separate from the semiconductor substrate 71. Fig. 11 will be built.

[0051] As described above, in the first embodiment, after the APD 7 detects light, the first reset circuit 3 limits the current supplied to the cathode of the APD 7 to gently increase its cathode voltage. Subsequently, the second reset circuit 4 supplies a large current to the cathode of the APD 7 to rapidly increase its cathode voltage. Accordingly, even if the APD 7 detects light while the first reset circuit 3 or the second reset circuit 4 is supplying current to the cathode of the APD 7, it is possible to prevent the flow of an uncontrollably large current to the APD 7. Therefore, according to the present embodiment, the APD 7 can be protected from heat generation and damage during a reset operation, and crosstalk due to light emission from the APD 7 can be reduced. Second embodiment

[0052] The photodetection device 1 according to the first embodiment shows an example in which the first reset circuit 3 and the second reset circuit 4 are connected in parallel between the first voltage node Vhi and the cathode of the APD 7. However, the connection relationship between the APD 7, the first reset circuit 3 and the second reset circuit 4 can be reversed.

[0053] Fig. Figure 12 is a circuit diagram of a photodetection device 1 according to a second embodiment. In the photodetection device 1 of Fig. In the first voltage node Vhi, the cathode of APD 7 is connected to the first voltage node Vhi, and the first reset circuit 3 and the second reset circuit 4 are connected in parallel between the anode of APD 7 and the second voltage node Vlow. The control circuit 5 controls the switching of the first switch 3b in the first reset circuit 3 and the second switch 4a in the second reset circuit 4, based on the anode voltage of APD 7.

[0054] The change in the anode voltage waveform of the APD 7 is the opposite of that in Fig. As shown in Figure 3, when APD 7 detects light, its anode voltage gradually increases. When the anode voltage reaches a predetermined threshold voltage, the control circuit 5 opens the first switch 3b in the first reset circuit 3, allowing current from the anode to flow to APD 7 through the current source 3a in the first reset circuit 3 and supplying the current to the second voltage node Vlow. Consequently, the anode voltage of APD 7 gradually decreases. The control circuit 5 then opens the second switch 4a in the second reset circuit 4. The current flowing to the anode of APD 7 then increases rapidly, causing the anode voltage of APD 7 to decrease rapidly.

[0055] In photo detection unit 1 of Fig. 12. There is no possibility of unlimited current flow to the APD 7, even when the APD 7 detects light, while current flows from the anode of the APD 7 to the power source 3a in the first reset circuit 3, or while current flows from the anode of the APD 7 to the second switch 4a in the second reset circuit 4. Therefore, as in the first embodiment, the generation of heat and crosstalk of the APD 7 can be reduced.

[0056] In the photodetection device 1 according to the second embodiment, a quench control unit 5a, as in Fig. 2 shown, provided in the control circuit 5. In addition, a first level converter 11 and a second level converter 12, as shown in the second embodiment, can also be provided in the photodetection device 1. Fig. 7 shown, is intended.

[0057] The photo detection device 1 of Fig. 12 can be used to configure the SiPMs 13 described above and quench circuit groups, as in Fig. 9 is shown, to configure. In addition, the photo detection device 1 of Fig. 12 can be used to operate the electronic device 21, as shown in Fig. 10A or Fig. 10B and Fig. 11 shown, to configure.

[0058] As described above, in the photodetection device 1 according to the second embodiment, the connection between APD 7, first reset circuit 3, and second reset circuit 4 is the reverse of that in the photodetection device 1 according to the first embodiment. However, in the second embodiment, as in the first embodiment, even if the APD 7 detects light while the first reset circuit 3 or the second reset circuit 4 is supplying current to the cathode of the APD 7, an uncontrollably large current flow to the APD 7 can be prevented. Therefore, according to the present embodiment, the APD 7 can be protected from heat generation and damage during a reset operation, and crosstalk due to light emission from the APD 7 can be reduced.

Claims

[1] Photo detection device (1), comprising: a photodetection element (7), wherein the photodetection element (7) is an avalanche photodiode; a first reset circuit (3) which is configured to select whether to set a one-way resistance between a first voltage node and a terminal of the photodetection element (7) to a first value; a second reset circuit (4) configured to select whether the input resistance is to be set to a second, smaller value than the first value; and a control circuit (5) that is configured: to set the input resistor to the first value by the first reset circuit (3) after the photodetection element (7) detects light; and to set the input resistance to the second value by the second reset circuit (4), based on a voltage at the terminal of the photodetection element (7), after the first reset circuit (3) selects to set the input resistance to the first value. [2] Photodetection device (1) according to claim 1, wherein the control circuit (5) is configured: to set the input resistor to the first value by the first reset circuit (3) after the photodetection element (7) detects light; and The input resistor is set to the second value by the second reset circuit (4) when a voltage at the terminal of the photodetection element (7) reaches a predetermined threshold value. [3] Photodetection device (1) according to claim 1 or 2, wherein the control circuit (5) holds the connection of the photodetection element (7) at a first voltage after the photodetection element (7) detects light, and sets the on-resistance to the first value by the first reset circuit (3) after holding the connection of the photodetection element (7) at the first voltage, and sets the on-resistance to the second value by the second reset circuit (4) after the first reset circuit (3) sets the on-resistance to the first value. [4] Photodetection device (1) according to claim 3, wherein the control circuit (5) comprises a voltage holding circuit to keep the connection of the photodetection element (7) at the first voltage for a predetermined duration in response to the connection of the photodetection element (7) being set to a second voltage which differs from the first voltage after the photodetection element (7) detects light. [5] Photodetection device (1) according to any one of claims 1 to 4, wherein the first reset circuit (3) comprises: a power source for outputting a predetermined current; and a first switch to select whether the predetermined current from the power source is to be supplied to the connection of the photodetection element (7), and the second reset circuit (4) comprises: a second switch to select whether a conductive connection is to be established between the first voltage node and the connection of the photodetection element (7). [6] Photodetection device (1) according to claim 5, wherein the control circuit (5) switches the first switch to supply the predetermined current from the power source to the terminal of the photodetection element (7) when the photodetection element (7) detects light, so that a voltage at the terminal of the photodetection element (7) varies by a predetermined voltage, and switches the second switch to establish a conductive connection between the first voltage node and the terminal of the photodetection element (7) after supplying the predetermined current from the power source to the terminal of the photodetection element (7). [7] Photodetection device (1) according to claim 5 or 6, wherein: the first switch is a first transistor for selecting whether the predetermined current from the power source is to be supplied to the connection of the photodetection element (7); the second switch is a second transistor to select whether a conductive connection is to be made between the first voltage node and the connection of the photodetection element (7); the control circuit (5) outputs a first control signal to control a gate voltage of the first transistor and a second control signal to control a gate voltage of the second transistor, and the photo detection device (1) further comprises: a first level converter for converting a voltage level of the first control signal and inputting the converted first control signal to a gate of the first transistor; and a second level converter to convert a voltage level of the second control signal and input the converted second control signal to a gate of the second transistor. [8] Photodetection device (1) according to any one of claims 5 to 7, wherein the control circuit (5) continuously switches the first switch to supply the predetermined current from the power source to the terminal of the photodetection element (7) when the photodetection element (7) detects light, while the first reset circuit (3) sets the on-resistance to the first value. [9] Photodetection device (1) according to one of claims 3 or 4, wherein the control circuit (5) sets the connection of the photodetection element (7) to the first voltage at a moment when the voltage of the connection of the photodetection element (7) reaches a predetermined voltage or lower when the photodetection element (7) detects light, while the second reset circuit (4) sets the on-resistance to the second value, and the on-resistance is set to the first value by the first reset circuit (3) after setting the connection of the photodetection element (7) to the first voltage, and the on-resistance is set to the second value by the second reset circuit (4) after setting the on-resistance to the first value. [10] Photodetection device (1) according to any one of claims 1 to 9, wherein the first reset circuit (3) and the second reset circuit (4) are connected in parallel between the first voltage node and a cathode of the avalanche photodiode. [11] Photodetection device (1) according to any one of claims 1 to 9, wherein the first reset circuit (3) and the second reset circuit (4) are connected in parallel between an anode of the avalanche photodiode and a voltage node of a lower voltage level than the first voltage node. [12] Photodetection device (1) according to claim 10 or 11, comprising: a multitude of avalanche photodiodes arranged in a one-dimensional or a two-dimensional direction; and active quench circuits (6) each belonging to the avalanche photodiodes, wherein the active quench circuit (6) comprises the first reset circuit (3), the second reset circuit (4) and the control circuit (5). [13] Electronic equipment (21), comprising: a light detector (24) comprising a photodetection device (1) according to any one of claims 1 to 12, wherein the light detector (24) is configured to receive second light containing reflected light obtained by reflecting first light off an object; an A / D converter (55) for generating a digital signal corresponding to the second light; a memory (61) for storing the digital signal; and a processor for measuring a distance to the object, based on a floodlight time of the first light and a light reception time of the reflected light at the light detector (24), wherein a floodlight unit (22) emits the first light as a floodlight at the floodlight time. [14] Electronic device (21) according to claim 13, further comprising a floodlight circuit for emitting the first light as a floodlight, wherein the processor detects the floodlight time of the first light. [15] Photodetection methods, including: Detection of light by a photodetection element (7), wherein the photodetection element (7) is an avalanche photodiode; Setting an on-resistance between a first voltage node and a terminal of the photodetection device (1) to a first value by means of a first reset circuit (3) to select whether the on-resistance is to be set to the first value after the photodetection element (7) detects light; and Setting the on-resistance to a second value by means of a second reset circuit (4) to select whether the on-resistance is to be set to the second value, which is smaller than the first value, based on a voltage at the terminal of the photodetection element (7) after the on-resistance has been set to the first value.

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