Light detection device and ranging system

Abstract

To provide a light detection device which has a simple circuit configuration, and yet features less fluctuation in light reception signal timing and is capable of preventing destruction of circuit elements even when exposed to light with large intensity.SOLUTION: A light detection device is provided, comprising a light reception element, a transistor for switching between whether to allow a current to flow to the light reception element or not, a photoconductive element for turning on or off the transistor according to the amount of received light, and a first resistor element for allowing the current to flow through the light reception element when the transistor is off.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a light detection device and a ranging system. [Background technology]

[0002] Autonomous driving technology requires that the distance to an obstacle be measured quickly and accurately. A ToF (Time of Flight) sensor is generally used for distance measurement. A ToF sensor receives the reflected light signal from an object using a SPAD (Single-Photon Avalanche Diode), which can detect even weak light.

[0003] Because the electrical characteristics of a SPAD change depending on the temperature, a technology has been proposed in which a variable resistance element is connected to the cathode side of the SPAD and the resistance value of the variable resistance element is controlled so that the ratio of avalanche current to recharge current remains constant regardless of temperature (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 116158 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technique of Patent Document 1 requires the provision of a dedicated control circuit for controlling the resistance value of the variable resistance element, which complicates the configuration of the light receiving device having a SPAD.

[0006] Furthermore, if the resistance value of the variable resistance element increases, the variation in timing of the light receiving signal increases, which may deteriorate the distance measurement accuracy.

[0007] Furthermore, various types of light, including ambient light, are incident on the ToF sensor, and in some cases, a large amount of light may be incident. If a large amount of light is incident on the ToF sensor, a large current may flow in the drive circuit of the SPAD, which may destroy the circuit elements in the drive circuit. However, Patent Document 1 does not take any measures against the incidence of a large amount of light.

[0008] Therefore, the present disclosure provides a light detection device and a distance measurement system that have a simple circuit configuration, are less likely to cause timing variations in the light receiving signal, and can prevent damage to circuit elements even when a large amount of light is incident. [Means for solving the problem]

[0009] In order to solve the above problems, according to the present disclosure, there is provided a light receiving element, a transistor for switching whether or not a current flows through the light receiving element; a photoconductive element that turns the transistor on or off in response to an amount of received light; a first resistor element that causes a current to flow through the light receiving element when the transistor is off; A light detection device is provided.

[0010] When the transistor is on, a current flows between the drain and source of the transistor to the light receiving element, When the transistor is off, a current flowing through the first resistor element may flow to the light receiving element.

[0011] The photoconductive element may turn the transistor off when the amount of received light is equal to or greater than a predetermined reference amount, and may turn the transistor on when the amount of received light is less than the reference amount.

[0012] When the amount of light received by the photoconductive element is less than the reference amount, no current may flow through the first resistive element, and when the amount of light received by the photoconductive element is equal to or greater than the reference amount, a current may flow through the first resistive element.

[0013] A plurality of pixels arranged in one or two dimensions, At least some of the pixels may include the light receiving element, the transistor, the photoconductive element, and the first resistor element.

[0014] The photoconductive element corresponding to one of the light receiving elements may be disposed along a boundary region between two adjacent pixels.

[0015] a silicon layer having a photoelectric conversion region partitioned by the boundary region; a contact member disposed along the boundary region and penetrating the silicon layer; the photoconductive element is disposed along the boundary region on the light incident surface side of the silicon layer and is connected to the contact member; The light receiving element may be formed using the photoelectric conversion region.

[0016] The photoconductive element corresponding to one of the light receiving elements is Two photoconductive portions disposed separately along two adjacent boundary regions of the corresponding pixel; A wiring portion that electrically connects the two photoconductive portions, Each of the two photoconductive portions may be connected to a corresponding one of the contact members.

[0017] The photoconductive element corresponding to one of the light receiving elements may be arranged in an L-shape along two adjacent boundary regions of the corresponding pixel.

[0018] a silicon layer having a photoelectric conversion region separated by the boundary region; the photoconductive element is disposed on a side of the silicon layer farther from the light incident surface than the photoelectric conversion region; The light receiving element may be formed using the photoelectric conversion region.

[0019] A plurality of pixels arranged in one or two dimensions, The plurality of pixels include First pixels each having the light receiving element; a plurality of second pixels provided corresponding to the first pixels, each having the photoconductive element; The plurality of second pixels may be arranged around the first pixel.

[0020] the photoconductive element is a laminate of a plurality of photoconductive layers each having at least one of a material and a film thickness different from each other; The plurality of photoconductive layers may each change their resistance value in response to incidence of light of a different wavelength.

[0021] The transistor switches between allowing and not allowing a current to flow between a first node and a second node; one end of the light receiving element is connected to the second node; the photoconductive element switches between conducting and blocking electrical conduction between the second node and the gate of the transistor in response to an amount of received light; The first resistive element may be connected between the first node and a gate of the transistor.

[0022] The photoconductive element may provide electrical continuity between the second node and the gate of the transistor when the amount of received light is equal to or greater than a predetermined reference amount, and may cut off electrical continuity between the second node and the gate of the transistor when the amount of received light is less than the reference amount.

[0023] when the amount of light received by the photoconductive element is less than the reference amount, a first current path is generated through which a current flows from the first node through the transistor and the second node to the light receiving element; When the amount of light received by the photoconductive element is equal to or greater than the reference amount, the first current path may be blocked, and a second current path may be generated through which current flows from the first node to the light receiving element via the first resistive element and the photoconductive element.

[0024] The transistor switches between allowing and not allowing a current to flow between a first node and a second node; one end of the light receiving element is connected to the second node; the photoconductive element switches the voltage applied to the gate of the transistor in response to the amount of received light to switch the transistor on or off; The first resistive element may be connected between the first node and the second node.

[0025] the photoconductive element turns off the transistor when the amount of received light is equal to or greater than a predetermined reference amount, and turns on the transistor when the amount of received light is less than the reference amount; when the amount of light received by the photoconductive element is less than the reference amount, a first current path is generated through which a current flows from the first node through the transistor and the second node to the light receiving element; When the amount of light received by the photoconductive element is equal to or greater than the reference amount, the first current path may be blocked, and a second current path may be generated through which current flows from the first node via the first resistive element and the second node to the light receiving element.

[0026] The light-receiving element may further include a second resistive element connected to at least one of a current path through which the current that has passed through the transistor flows to the light-receiving element and a current path through which the current that has passed through the first resistive element flows to the light-receiving element.

[0027] A first substrate disposed on the light incident surface side; a second substrate laminated on the first substrate on the side opposite to the light incident surface, the light receiving element, the photoconductive element, and the first resistor element are disposed on the first substrate; the transistor is disposed on the second substrate; The first substrate and the second substrate may transmit signals by bonding vias, bumps, or metal members together.

[0028] According to the present disclosure, a light emitting device that projects an optical signal; a light receiving device that receives a reflected light signal of the light signal irradiated onto an object; a distance measuring device that measures a distance to the object based on the optical signal and the reflected optical signal, The light receiving device is A light receiving element; a transistor for switching whether or not a current flows through the light receiving element; a photoconductive element that turns the transistor on or off in response to an amount of received light; a first resistor element that causes a current to flow through the light receiving element when the transistor is off; A ranging system is provided. [Brief description of the drawings]

[0029] [Figure 1] 1 is a circuit diagram of a photodetector according to a first embodiment of the present disclosure. [Diagram 2] 2A is a cross-sectional view and a plan view of the photodetection device according to the first embodiment, FIG. 2B is a plan view of the dashed line region ar1 in FIG. 2A, and FIG. 2C is a plan view of the dashed line region ar2 in FIG. 2A. [Diagram 3] 1 is a graph showing the relationship between the resistance value of a quench resistor and the variation in the output signal of a SPAD. [Figure 4] FIG. 4 is a circuit diagram of a photodetector according to a modified example of the first embodiment. [Diagram 5] 5A is a cross-sectional view and a plan view of a photodetector according to a modified example of the first embodiment, FIG. 5A is a cross-sectional view of the photodetector according to the modified example, FIG. 5B is a plan view of the dashed line region ar1 in FIG. 5A, and FIG. 5C is a plan view of the dashed line region ar2 in FIG. 5A. [Figure 6] 6A is a plan view showing three representative forms of a photoconductive element according to the first embodiment, FIG. 6A is a plan view of a photoconductive element according to a first example, FIG. 6B is a plan view of a photoconductive element according to a second example, and FIG. 6C is a plan view of a photoconductive element according to a third example. [Figure 7A] FIG. 3 is a circuit diagram of a first example in which a protective resistor is added to the photodetector according to the first embodiment. [Figure 7B] FIG. 4 is a circuit diagram of a second example in which a protective resistor is added to the photodetector according to the first embodiment. [Figure 7C] FIG. 4 is a circuit diagram of a third example in which a protective resistor is added to the photodetector according to the first embodiment. [Figure 7D]FIG. 11 is a circuit diagram of a fourth example in which a protective resistor is added to the photodetector according to the first embodiment. [Figure 7E] FIG. 11 is a circuit diagram of a fifth example in which a protective resistor is added to the photodetector according to the first embodiment. [Figure 7F] FIG. 13 is a circuit diagram of a sixth example in which a protective resistor is added to the photodetector according to the first embodiment. [Figure 7G] FIG. 13 is a circuit diagram of a seventh example in which a protective resistor is added to the photodetector according to the first embodiment. [Figure 7H] FIG. 13 is a circuit diagram of an eighth example in which a protective resistor is added to the photodetector according to the first embodiment. [Figure 8] 8A and 8B are a cross-sectional view and a plan view of a photodetector according to a second embodiment of the present disclosure, FIG. 8A being a cross-sectional view of the photodetector according to the second embodiment, and FIG. 8B being a plan view of a dashed line region ar1 in FIG. 8A. [Figure 9] FIG. 11 is a cross-sectional view of a light detection device according to a modified example of the second embodiment. [Figure 10] FIG. 2 is a cross-sectional view of a photoconductive element having a laminated structure. [Figure 11A] FIG. 13 is a plan view showing a pixel structure of a photodetector according to a fourth embodiment. [Figure 11B] FIG. 13 is a plan view showing a pixel structure of a photodetector according to a modified example of the fourth embodiment. [Figure 12] FIG. 1 is a cross-sectional view of a ToF sensor in which a light emitting device and a light detecting device are arranged on the same support member. [Figure 13A] An explanatory diagram of the STL method. [Figure 13B] An explanatory diagram of the distance measurement principle of the STL method. [Figure 14] FIG. 1 is a block diagram showing an example of a schematic configuration of a vehicle control system. [Figure 15] FIG. 4 is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an embodiment of a light detection device and a distance measurement system will be described with reference to the drawings. The following description will focus on the main components of the light detection device and the distance measurement system, but the light detection device and the distance measurement system may include components and functions that are not shown or described. The following description does not exclude components and functions that are not shown or described.

[0031] (First embodiment) Fig. 1 is a circuit diagram of a photodetector 1 according to a first embodiment of the present disclosure. As shown in Fig. 1, the photodetector 1 according to the first embodiment includes a light receiving section 2, a waveform shaping circuit 3, and a TDC (Time to Digital Converter) 4.

[0032] The light receiving section 2 includes a light receiving element 5, a first transistor 6, a photoconductive element 7, a quench resistor (first resistive element) 8, and a second transistor 9.

[0033] The light receiving element 5 is, for example, a SPAD that can operate in Geiger mode. The Geiger mode is a mode in which photons are detected in a state in which a reverse bias with a voltage difference exceeding the breakdown voltage is applied between the anode and cathode of the SPAD. In the following, an example in which the light receiving element 5 is a SPAD 5 will be described.

[0034] SPAD5 can detect even weak light of about one photon. When SPAD5 detects light, it is called firing. When SPAD5 fires, the voltage difference between the anode and cathode of SPAD5 decreases rapidly, and the cathode voltage drops to the bottom voltage. The voltage difference between the anode voltage and the bottom voltage is the breakdown voltage. The cathode of SPAD5 is connected to the source of the first transistor 6 (second node n2), and a negative reference voltage (-VAN) is applied to the anode.

[0035] The first transistor 6 switches whether or not a current flows through the SPAD 5. In Fig. 1, the first transistor 6 is an NMOS transistor by way of example, but it may be a PMOS transistor as described later. In this specification, the first transistor 6 may be simply referred to as a transistor.

[0036] The drain of the first transistor 6 is connected to a first node n1, and the source is connected to a second node n2. The second node n2 is connected to the cathode of the SPAD 5. The first node n1 is an input node of the waveform shaping circuit 3.

[0037] The photoconductive element 7 turns the first transistor 6 on or off depending on the amount of received light. The photoconductive element 7 is connected between the gate and source (second node n2) of the first transistor 6. The photoconductive element 7 functions as a switch that switches between conducting and blocking the gate and source (second node n2) of the first transistor 6 depending on the amount of received light. The photoconductive element 7 turns the first transistor 6 off when the amount of received light is equal to or greater than a predetermined reference amount, and turns the first transistor 6 on when the amount of received light is less than the reference amount. In this way, the photoconductive element 7 makes the gate and source (second node n2) of the first transistor 6 conducting when the amount of received light is equal to or greater than the predetermined reference amount, and blocks the gate and source (second node n2) of the first transistor 6 when the amount of received light is less than the reference amount.

[0038] The reference amount of light received by the photoconductive element 7 to switch the conduction / cutoff between the gate and source of the first transistor 6 depends on at least one of the material and film thickness of the photoconductive element 7. Representative materials of the photoconductive element 7 include germanium, a mixed crystal of silicon and germanium, amorphous silicon, graphene, a perovskite compound, and various compound semiconductor materials (e.g., InGaAs, HgCdTe, InSb, InP, CdS, CdSe, CdS-Se, PbS, etc.). By changing the material of the photoconductive element 7, it is possible to change the wavelength of light at which the photoconductive element 7 can switch the conduction / cutoff between the gate and source of the first transistor 6. In addition, by changing the film thickness of the photoconductive element 7, it is possible to change the resistance value of the photoconductive element 7.

[0039] A current flows through the quench resistor 8 when the first transistor 6 is off, and no current flows when the first transistor 6 is on. The current flowing through the quench resistor 8 flows to the SPAD 5 via the photoconductive element 7. While the amount of light received by the photoconductive element 7 is less than a reference amount, no current flows through the quench resistor 8, and when the amount of light received by the photoconductive element 7 becomes equal to or greater than the reference amount, a current flows through the quench resistor 8. In this specification, the quench resistor 8 may be referred to as a first resistor.

[0040] In FIG. 1, the quench resistor 8 is connected between the first node n1 and the gate of the transistor. When the amount of light received by the photoconductive element 7 is equal to or greater than a predetermined reference amount, a current flows from the first node n1 through the quench resistor 8, the photoconductive element 7, and the second node n2 to the SPAD 5. When the amount of light received by the photoconductive element 7 is less than the reference amount, no current flows through the quench resistor 8, but a current flows through the first node n1, between the drain and source of the first transistor 6, and the second node n2 to the SPAD 5. In this way, a current flows through the quench resistor 8 only when the amount of light received by the photoconductive element 7 is equal to or greater than the reference amount.

[0041] The arrows y1 and y2 in FIG. 1 indicate the movement direction of electrons generated by photoelectric conversion in the SPAD 5. The arrow y1 indicates the movement direction of electrons when the amount of light received by the photoconductive element 7 is less than a predetermined reference amount. In this case, the electrons output from the cathode (second node n2) of the SPAD 5 flow through the source-drain of the first transistor 6 to the first node n1. The arrow y2 indicates the movement direction of electrons when the amount of light received by the photoconductive element 7 is equal to or greater than the reference amount. In this case, some of the electrons output from the cathode of the SPAD 5 flow through the photoconductive element 7 to the gate of the first transistor 6, and the rest flow through the quench resistor 8 to the first node n1.

[0042] Thus, in the photodetector 1 of FIG. 1, when the amount of light received by the photoconductive element 7 is less than the reference amount, a first current path is generated in which a current flows from the first node n1 via the first transistor 6 and the second node n2 to the SPAD 5, and when the amount of light received by the photoconductive element 7 is equal to or greater than the reference amount, the first current path is cut off and a second current path is generated in which a current flows from the first node n1 via the quench resistor 8 and the photoconductive element 7 to the SPAD 5.

[0043] The second transistor 9 is provided to control the cathode voltage of the SPAD 5. In the normal state, a reverse bias voltage larger than the breakdown voltage is applied to the SPAD 5. The voltage obtained by subtracting the breakdown voltage from the reverse bias voltage is called an excess voltage. The second transistor 9 controls the magnitude of the excess voltage. Although FIG. 1 shows an example in which the second transistor 9 is configured as a PMOS transistor, it is also possible to configure it as an NMOS transistor.

[0044] When the SPAD5 fires, the voltage of the first node n1 drops. The waveform shaping circuit 3 is connected to the first node n1. The waveform shaping circuit 3 has an inverter IV made up of, for example, a PMOS transistor and an NMOS transistor. The inverter IV inverts and outputs the voltage of the first node n1. When the SPAD5 fires, the waveform shaping circuit 3 outputs, for example, a high-level pulse signal.

[0045] The TDC 4 generates a digital signal according to the time when the SPAD 5 fires, based on the pulse signal output from the waveform shaping circuit 3.

[0046] Fig. 2 is a cross-sectional view and a plan view of the photodetector 1 according to the first embodiment. More specifically, Fig. 2A is a cross-sectional view of the photodetector 1 according to the first embodiment, Fig. 2B is a plan view of a dashed line region ar1 in Fig. 2A, and Fig. 2C is a plan view of a dashed line region ar2 in Fig. 2A.

[0047] 2A, the photodetector 1 according to the first embodiment has a laminate structure in which a first substrate 11 and a second substrate 12 are laminated. The first substrate 11 is disposed on the light incident surface side, and the second substrate 12 is disposed on the surface side opposite the light incident surface.

[0048] The first substrate 11 has a laminated silicon layer 13 and an insulating layer 14. The silicon layer 13 is disposed on the light incident surface side, and the insulating layer 14 is disposed on the surface side opposite to the light incident surface. The silicon layer 13 is divided by pixel isolation regions 15, and an area surrounded by the pixel isolation regions 15 is the area of ​​one pixel 16. The cross-sectional view and plan view of FIG. 2 show the structure of one pixel 16. A plurality of pixels 16 are arranged on the first substrate 11 in one or two dimensions. At least some of the plurality of pixels have a light receiving element (SPAD) 5, a first transistor 6, a photoconductive element 7, and a quench resistor 8.

[0049] The region of the silicon layer 13 partitioned by the pixel isolation region 15 is a photoelectric conversion region 17. The photoelectric conversion region 17 is used to form the SPAD 5.

[0050] The pixel isolation region 15 has a contact member 18 disposed along the boundary of the pixel 16 so as to penetrate the silicon layer 13, an oxide layer 19 disposed so as to surround the sidewall surface of the contact member 18, and a P+ diffusion layer 20 disposed so as to surround the oxide layer 19. An anode terminal 21 is disposed at the contact point of the P+ diffusion layer 20 with the insulating layer 14.

[0051] A photoconductive element 7 is disposed on the light incident surface side of the silicon layer 13. The photoconductive element 7 is disposed along the boundary region of the pixel 16 as shown in FIG. 2B. The photoconductive element 7 is connected to a contact member 18 of the pixel isolation region 15. A photoelectric conversion region 17 is provided in the region of the pixel 16, but since the photoconductive element 7 is disposed in the pixel isolation region 15, providing the photoconductive element 7 has almost no effect on the aperture area of ​​the photoelectric conversion region 17. Therefore, the photodetector 1 according to the first embodiment can dispose the photoconductive element 7 without reducing the sensitivity of the SPAD 5. Furthermore, since the photoconductive element 7 is disposed on the light incident surface side, the sensitivity of the photoconductive element 7 can be improved.

[0052] 2B shows an example in which L-shaped photoconductive elements 7 are provided on two adjacent sides of the four sides of the pixel isolation region 15 surrounding the rectangular pixel 16, but the shape of the photoconductive elements 7 is arbitrary. Representative variations in the shape of the photoconductive elements 7 will be described later.

[0053] A multiplication region 22 is disposed on the side of the silicon layer 13 closer to the insulating layer 14. The multiplication region 22 has an anode region 23 and a cathode region 24 disposed opposite each other. The anode region 23 is disposed on the light incident surface side, and the cathode region 24 is disposed on the insulating layer 14 side. The anode region 23 is a P+ diffusion region, and the anode region 23 is an N+ diffusion region. The interface between the anode region 23 and the cathode region 24 is a PN junction surface. A cathode terminal 25 is connected to the cathode region 24.

[0054] In this manner, the anode terminal 21 and the cathode terminal 25 are disposed near the interface between the silicon layer 13 and the insulating layer 14. The anode terminal 21 and the cathode terminal 25 are connected to vias 26v, respectively, and the other end of each via 26v is connected to the wiring layer 27 in the insulating layer 14.

[0055] A quench resistor 8, a wiring layer 27, and a contact member 26c are disposed on the insulating layer 14. Although Fig. 1 shows an example in which a plurality of wiring layers 27 are disposed on one layer, a plurality of wiring layers 27 may be disposed on a plurality of layers.

[0056] 2C, the quench resistor 8 is disposed so as to surround the cathode terminal 25 in plan view. The shapes and locations of the quench resistor 8 and the cathode terminal 25 are arbitrary.

[0057] The anode terminal 21, the cathode terminal 25, and the contact member 18 arranged on the silicon layer 13 are connected to a plurality of wiring layers 27 through a plurality of vias 26v that are separately arranged in the insulating layer 14. These plurality of wiring layers 27 are connected to the Cu layer 28c through the contact member 26c.

[0058] The first substrate 11 and the second substrate 12 are joined together, for example, by a CCC (Cupper to Cupper Connection) 28. Note that instead of the CCC 28, the first substrate 11 and the second substrate 12 may be joined together by vias, bumps, or the like.

[0059] A logic circuit 12L including a first transistor 6, a second transistor 9, a waveform shaping circuit 3, and a TDC 4 is formed on the second substrate 12. The second substrate 12 has a silicon layer 13 and an insulating layer 14 which are stacked on top of each other. The logic circuit 12L including a plurality of transistors is disposed on the silicon layer 13. A plurality of wiring layers 29 consisting of a plurality of layers are disposed on the insulating layer 14.

[0060] 2A indicates the flow of electrons when the amount of light received by the photoconductive element 7 is less than a predetermined reference amount. When the amount of light received by the photoconductive element 7 is less than a predetermined reference amount, electrons generated by photoelectric conversion inside the SPAD 5 flow between the source and drain of the first transistor Q1 arranged on the second substrate 12. In this case, electrons do not flow through the photoconductive element 7 and the quench resistor 8.

[0061] 2A indicates the flow of electrons when the amount of light received by the photoconductive element 7 is equal to or greater than the reference amount. When the amount of light received by the photoconductive element 7 is equal to or greater than the reference amount, electrons output from the cathode of the SPAD 5 flow through the wiring layer 27, the contact member 18, the photoconductive element 7, the photoelectric conversion region 17, and the quench resistor.

[0062] As described above, in the photodetector 1 according to the first embodiment, a current flows through the quench resistor 8 only when a large amount of light is incident on the photodetector 1. Therefore, in a situation where a large amount of light is not incident on the photodetector 1, a delay in the output signal of the SPAD 5 caused by the quench resistor 8 does not occur.

[0063] FIG. 3 is a graph showing the relationship between the resistance value of the quench resistor 8 and the variation (skew) of the output signal of the SPAD 5. The horizontal axis of FIG. 3 is the resistance value of the quench resistor 8, and the vertical axis is the variation of the output signal of the SPAD 5. As shown in FIG. 3, the larger the quench resistor 8, the larger the variation of the output signal of the SPAD 5. For example, when the quench resistor 8 is a variable resistor, if there is a risk of an overcurrent flowing through the SPAD 5, control is performed to increase the resistance value of the quench resistor 8. However, as shown in FIG. 3, there is a problem that the larger the quench resistor 8, the greater the variation of the output signal of the SPAD 5. In a ToF sensor using the SPAD 5, the greater the variation of the output signal of the SPAD 5, the lower the ranging accuracy.

[0064] In the photodetection device 1 of the first embodiment, when a large amount of light is not incident, no current flows through the quench resistor 8. Therefore, unless a large amount of light is incident, the variation in the output signal of the SPAD 5 does not increase, thereby improving the distance measurement accuracy.

[0065] Although an example in which the first transistor 6 is an NMOS transistor has been described in FIG. 1, the first transistor 6 may be a PMOS transistor.

[0066] Fig. 4 is a circuit diagram of a photodetector 1 according to a modified example of the first embodiment. Fig. 4 shows the configuration of a light receiving section 2 in a photodetector 1 according to the modified example.

[0067] The light receiving section 2 in the light detecting device 1 according to the one modification includes a SPAD 5 constituting a light receiving element 5, a first transistor 6, a photoconductive element 7, and a quench resistor 8, as shown in FIG.

[0068] The first transistor 6 is connected between the first node n1 and the second node n2. The first transistor 6 is a PMOS transistor. The source of the first transistor 6 is connected to the first node n1, and the drain is connected to the second node n2.

[0069] The cathode of SPAD5 is connected to the second node n2, and a negative reference voltage (-VAN) is applied to the anode.

[0070] The photoconductive element 7 is connected between a positive reference voltage VDD and the gate of the first transistor 6. Like the light-receiving element 5 according to the first embodiment, the photoconductive element 7 according to the second embodiment turns off the first transistor 6 when the amount of received light is equal to or greater than a predetermined reference amount, and turns on the first transistor 6 when the amount of received light is less than the reference amount.

[0071] Also, similar to the first embodiment, when the amount of light received by the photoconductive element 7 is less than the reference amount, no current flows through the quench resistor 8, and when the amount of light received by the photoconductive element 7 becomes equal to or greater than the reference amount, current flows through the quench resistor 8.

[0072] Thus, in the photodetector 1 according to one modified example shown in FIG. 4, the photoconductive element 7 turns off the first transistor 6 when the amount of received light is equal to or greater than a predetermined reference amount, and turns on the first transistor 6 when the amount of received light is less than the reference amount; when the amount of received light by the photoconductive element 7 is less than the reference amount, a first current path is generated in which a current flows from the first node n1 to the SPAD 5 via the first transistor 6 and the second node n2; and when the amount of received light by the photoconductive element 7 is equal to or greater than the reference amount, the first current path is interrupted, and a second current path is generated in which a current flows from the first node n1 to the SPAD 5 via the quench resistor 8 and the second node n2.

[0073] Fig. 5 is a cross-sectional view and a plan view of a photodetector 1 according to a modified example of the first embodiment. More specifically, Fig. 5A is a cross-sectional view of the photodetector 1 according to the modified example, Fig. 5B is a plan view of a dashed line region ar1 in Fig. 5A, and Fig. 5C is a plan view of a dashed line region ar2 in Fig. 5A.

[0074] The cross-sectional structure and plan view of the photodetector 1 according to one modified example shown in FIG. 5 are substantially the same as the cross-sectional structure and plan view of the photodetector 1 according to the first embodiment shown in FIG. 2, but the path along which electrons flow when the amount of light received by the photoconductive element 7 is less than a predetermined reference amount is different (arrow line y1 in FIG. 5).

[0075] In the photodetector 1 according to the one modified example, electrons that pass from the power supply voltage node through the contact member 18 of the pixel isolation region 15 and the photoconductive element 7 pass through the photoelectric conversion region 17 and flow to the second substrate 12.

[0076] In the photodetector 1 according to the modified example shown in Figures 4 and 5, the photoconductive element 7 is also arranged along the pixel isolation region 15 on the light incident surface side, so that the first transistor 6 can be turned on or off according to the amount of incident light received without reducing the sensitivity of the SPAD 5, and a current can be passed through the quench resistor 8 only when a large amount of light is incident.

[0077] The photoconductive element 7 according to the first embodiment is disposed along the pixel isolation region 15 on the light incident surface side of the first substrate 11, but various configurations are applicable to the shape and size of the photoconductive element 7. Fig. 6 is a plan view showing three representative configurations of the photoconductive element 7 according to the first embodiment. Fig. 6A is a plan view of the photoconductive element 7 according to a first example, Fig. 6B is a plan view of the photoconductive element 7 according to a second example, and Fig. 6C is a plan view of the photoconductive element 7 according to a third example.

[0078] 6A, the photoconductive element 7 according to the first example has two photoconductive portions 7a arranged along two pixel boundary sides of the corresponding pixel 16, and a wiring 7b connecting these photoconductive portions 7a. A contact member 18 penetrating the silicon layer 13 is connected to each photoconductive portion 7a.

[0079] As shown in Fig. 6B, the photoconductive element 7 according to the second example has two photoconductive portions 7a arranged along two pixel boundary sides of the corresponding pixel 16. One of the two photoconductive portions 7a is L-shaped and arranged along the two pixel boundary sides. The other of the two photoconductive portions 7a is linear and arranged along one pixel boundary side. A contact member 18 penetrating the silicon layer 13 is connected to each photoconductive portion 7a.

[0080] As shown in FIG. 6C, the photoconductive element 7 according to the third example has an L-shape that is disposed along two pixel boundary sides, and contact members 18 that penetrate the silicon layer 13 are connected to the corners.

[0081] 6A to 6C, photoconductive elements 7 for adjacent pixels 16 are also arranged on two pixel boundary sides facing the photoconductive elements 7 shown in Fig. 6A to 6C. Since photoconductive elements 7 are arranged using two pixel boundary sides for each pixel 16, photoconductive elements 7 can be arranged by effectively utilizing all pixel boundary sides.

[0082] As shown in FIG. 3, when the current flowing through the SPAD 5 is passed through the quench resistor 8, if the resistance value of the quench resistor 8 varies due to manufacturing variations, the signal level of the output signal of the SPAD 5 also varies greatly, and the distance accuracy decreases. However, since the current flowing through the SPAD 5 varies depending on the amount of light incident on the photodetector 1, in order to prevent the circuit elements of the photodetector 1 from being destroyed, it may be better to provide a protective resistor separately from the quench resistor 8 in FIG. 1 or FIG. 4. The protective resistor is provided on at least one of the current path through which the SPAD 5 flows when the amount of light received by the photoconductive element 7 is less than a predetermined reference amount, and the current path through which the SPAD 5 flows when the amount of light received is equal to or greater than the reference amount. There are multiple possible locations for connecting the protective resistor. The protective resistor is connected to at least one of the current path through which the current passing through the first transistor 6 flows through the SPAD 5 and the current path through which the current passing through the quench resistor 8 flows through the SPAD 5.

[0083] 7A is a circuit diagram of a first example in which a protective resistor (second resistor) 10 is added to the photodetector 1 according to the first embodiment. The protective resistor 10 in FIG. 7A is connected between the source (second node n2) of the first transistor 6 and the cathode of the SPAD 5. One end of the protective resistor 10 is connected to the source of the first transistor 6 and one end of the photoconductive element 7. In the photodetector 1 in FIG. 7A, a current flows through the protective resistor 10 regardless of the amount of light received by the photoconductive element 7. By providing the protective resistor 10, the voltage between the anode and cathode of the SPAD 5 can be suppressed and the current flowing through the SPAD 5 can be limited, thereby preventing damage to circuit elements in the photodetector 1.

[0084] 7B is a circuit diagram of a second example in which a protective resistor 10 is added to the photodetector 1 according to the first embodiment. The protective resistor 10 in FIG. 7B is connected between the source of the first transistor 6 and the cathode (second node n2) of the SPAD 5. The protective resistor 10 is not connected between the photoconductive element 7 and the cathode of the SPAD 5. Therefore, when the amount of light received by the photoconductive element 7 is less than a predetermined reference amount, a current flows from the first node n1 through the drain-source of the first transistor 6 and the protective resistor 10 to the SPAD 5. On the other hand, when the amount of light received by the photoconductive element 7 is equal to or greater than the reference amount, no current flows through the protective resistor 10, and a current flows from the first node n1 through the quench resistor 8 and the photoconductive element 7 to the SPAD 5.

[0085] Fig. 7C is a circuit diagram of a third example in which a protective resistor 10 is added to the photodetector 1 according to the first embodiment. The protective resistor 10 in Fig. 7C is connected between the first node n1 and the drain of the first transistor 6. Therefore, when the amount of light received by the photoconductive element 7 is less than a predetermined reference amount, a current flows through the protective resistor 10, but when the amount of light received by the photoconductive element 7 is equal to or greater than the reference amount, no current flows through the protective resistor 10.

[0086] Fig. 7D is a circuit diagram of a fourth example in which a protective resistor 10 is added to the photodetector 1 according to the first embodiment. The protective resistor 10 in Fig. 7D is connected between the second transistor 9 and the first node n1. Therefore, a current flows through the protective resistor 10 regardless of the amount of light received by the photoconductive element 7.

[0087] 7A to 7D show variations of the protective resistor 10 when the first transistor 6 is an NMOS transistor, whereas FIGS. 7E to 7H show variations of the protective resistor 10 when the first transistor 6 is a PMOS transistor.

[0088] Fig. 7E is a circuit diagram of a fifth example in which a protective resistor 10 is added to the photodetector 1 according to the first embodiment. Since the protective resistor 10 in Fig. 7E is connected between the second node n2 and the cathode of the SPAD 5, a current can flow through the protective resistor 10 regardless of the amount of light received by the photoconductive element 7, similar to Fig. 7A.

[0089] Fig. 7F is a circuit diagram of a sixth example in which a protective resistor 10 is added to the photodetector 1 according to the first embodiment. Since the protective resistor 10 in Fig. 7F is connected between the drain of the first transistor 6 and the second node n2, it is possible to pass a current through the protective resistor 10 when the amount of light received by the photoconductive element 7 is less than the reference amount, similar to Fig. 7B.

[0090] Fig. 7G is a circuit diagram of a seventh example in which a protective resistor 10 is added to the photodetector 1 according to the first embodiment. The protective resistor 10 in Fig. 7G is connected between the first node n1 and the source of the first transistor 6, so that, similarly to Fig. 7C, when the amount of light received by the photoconductive element 7 is less than the reference amount, a current can flow through the protective resistor 10.

[0091] Fig. 7H is a circuit diagram of an eighth example in which a protective resistor 10 is added to the photodetector 1 according to the first embodiment. Since the protective resistor 10 in Fig. 7H is connected between the second transistor 9 and the first node n1, a current can flow through the protective resistor 10 regardless of the amount of light received by the photoconductive element 7, similar to Fig. 7D.

[0092] In this way, in the first embodiment, the photoconductive element 7 is provided to turn on or off the first transistor 6, which switches whether or not a current flows to the light receiving element 5, depending on the amount of received light, so that when a large amount of light is incident on the SPAD 5, the photoconductive element 7 can turn off the first transistor 6, and a large current does not flow from the first transistor 6 to the SPAD 5, thereby preventing damage to the circuit elements in the photodetector 1. The photoconductive element 7 according to the first embodiment is disposed along the pixel isolation region 15 on the light incident surface side of the first substrate 11, so that it can receive incident light with good sensitivity and can quickly switch the first transistor 6 on or off depending on the amount of received incident light.

[0093] Second embodiment In the photodetector 1 of the first embodiment, the photoconductive element 7 is arranged on the light incident surface side of the first substrate 11, but the location of the photoconductive element 7 is arbitrary and does not necessarily have to be on the light incident surface side of the first substrate 11.

[0094] Fig. 8 is a cross-sectional view and a plan view of a photodetector 1 according to a second embodiment of the present disclosure. More specifically, Fig. 8A is a cross-sectional view of the photodetector 1 according to the second embodiment, and Fig. 8B is a plan view of a dashed line region ar1 in Fig. 8A.

[0095] The photodetector 1 according to the second embodiment is configured with a circuit similar to that shown in FIG. 1 or FIG. 4, but the location of the photoconductive element 7 is different from that of the first embodiment. The photoconductive element 7 according to the second embodiment is disposed on the insulating layer 14 of the first substrate 11. The silicon layer 13 is disposed on the light incident surface side of the insulating layer 14, but since the silicon layer 13 transmits light, even if the photoconductive element 7 is disposed on the insulating layer 14, the resistance value of the photoconductive element 7 can be changed by the light that is incident on the light incident surface and transmitted through the silicon layer 13. As a result, when the amount of light received by the photoconductive element 7 is equal to or greater than the reference amount, the resistance value of the photoconductive element 7 can be lowered to allow a current to flow through the quench resistor 8.

[0096] FIG. 8A shows an example in which the photoconductive element 7 and the quench resistor 8 are disposed on the same layer of the insulating layer 14, but they may be disposed on separate layers.

[0097] 8B shows an example in which the planar shapes of the photoconductive element 7 and the quench resistor 8 are both rectangular, but they do not necessarily have to be rectangular. The sizes of the photoconductive element 7 and the quench resistor 8 are also arbitrary. However, since the photoconductive element 7 needs to efficiently receive incident light, it is desirable to make the area as large as possible.

[0098] As shown in Fig. 8A, the silicon layer 13 of the first substrate 11 is divided by pixel isolation regions 15, but contact members 18 are not arranged in the pixel isolation regions 15. This is because the photoconductive elements 7 are not arranged on the light incident surface side. However, in the second embodiment, contact members 18 similar to those in Fig. 2 may be arranged in the pixel isolation regions 15. By arranging the contact members 18, the contact members 18 can be used as a transfer path for charges generated by photoelectric conversion, and the photoelectric conversion efficiency can be improved.

[0099] In addition, the photodetector 1 according to the second embodiment may also be provided with a protective resistor 10 similar to that shown in FIGS. 7A to 7H.

[0100] Various modifications can be applied to the location of the photoconductive element 7 according to the second embodiment. FIG. 9 is a cross-sectional view of a photodetector 1 according to a modification of the second embodiment. In the photodetector 1 according to the modification, the photoconductive element 7 is disposed along the surface opposite to the light incident surface of the silicon layer 13 of the second substrate 12. This allows the area of ​​the photoconductive element 7 to be wider, and even if the photoconductive element 7 is not disposed on the light incident surface side, the resistance value of the photoconductive element 7 can be quickly controlled in response to incident light. This allows the resistance value of the photoconductive element 7 to be lowered and a current to flow through the quench resistor 8 only when the amount of light received by the photoconductive element 7 is equal to or greater than a reference amount.

[0101] As described above, in the second embodiment, the photoconductive element 7 is disposed inside the insulating layer 14 on the second substrate 12 side of the silicon layer 13 on which the photoelectric conversion region 17 is disposed, rather than on the light incident surface side of the first substrate 11, so restrictions on the placement location and size of the photoconductive element 7 are alleviated compared to the first embodiment, allowing a large-area photoconductive element 7 to be disposed. Since the silicon layer 13 transmits incident light, the resistance value of the photoconductive element 7 can be quickly controlled in response to the incident light, even if the photoconductive element 7 is disposed on the insulating layer 14.

[0102] (Third embodiment) By changing at least one of the material or film thickness of the photoconductive element 7 in the photodetector 1 according to the first and second embodiments, it is possible to switch the wavelength of incident light that varies the resistance value of the photoconductive element 7, and to switch the control range of the resistance value relative to the amount of incident light. Furthermore, the photoconductive element 7 may be a laminated structure, and photoconductive layers differing in at least one of the material or film thickness may be disposed in each layer of the laminated structure.

[0103] 10 is a cross-sectional view of a photoconductive element 7 made of a laminated structure. The number of layers in the laminated structure constituting the photoconductive element 7 is arbitrary.

[0104] In this way, by forming the photoconductive element 7 into a laminated structure and arranging photoconductive layers 31 having at least one different material or film thickness in each layer of the laminated structure, it is possible to widen the wavelength band of incident light in which the resistance value of the photoconductive element 7 can be varied. Therefore, for example, it is possible to realize a photodetector 1 having a photoconductive element 7 sensitive to visible light and infrared light.

[0105] (Fourth embodiment) In the first to third embodiments, examples in which a SPAD 5 and a photoconductive element 7 are arranged for each pixel 16 have been mainly described, but when the photodetection device 1 is used in a distance measurement system, it is desirable to increase the sensitivity as much as possible of both the SPAD 5 and the photoconductive element 7. Therefore, the photodetection device 1 according to the fourth embodiment is characterized in that the sensitivity of the SPAD 5 and the photoconductive element 7 is improved.

[0106] FIG. 11A is a plan view showing a pixel structure of a photodetector 1 according to a fourth embodiment. As shown in FIG. 11A, the photodetector 1 according to the fourth embodiment detects whether or not incident light is received for each pixel group 32 including a total of nine pixels 16, three in each of the first direction X and the second direction Y. A SPAD 5 is disposed in one pixel 16a at the center of the pixel group 32, and photoconductive elements 7 are disposed in the remaining eight surrounding pixels 16b. In the central pixel 16a, the photoelectric conversion region 17 for the SPAD 5 is set in almost the entire area on the light incident surface side of the silicon layer 13. In the surrounding eight pixels 16b, the photoconductive elements 7 are disposed in almost the entire area on the light incident surface side of the silicon layer 13. This improves the sensitivity of the photoconductive elements 7, and for example, the first transistor 6 can be switched on or off depending on the average value of the amount of light received by the photoconductive elements 7 of the eight pixels 16b.

[0107] Of the pixel group 32, eight pixels 16b in which photoconductive elements 7 are arranged may include a SPAD 5, but the SPAD 5 cannot be used. Such pixels 16b are also called dummy pixels 16. Of the pixel group 32, only one pixel 16a performs light detection using the SPAD 5, and the number of pixels 16 performing light detection using the SPAD 5 is reduced. For this reason, when the light detection device 1 is used for distance measurement, the number of spots that detect reflected light from an object is reduced. However, when a distance measurement method is adopted in which spot light is irradiated onto an object and the reflected light is received, distance measurement can be performed without any problem even if light detection is performed using one pixel 16a per pixel group 32.

[0108] Fig. 11B is a plan view showing a pixel structure of a photodetector 1 according to a modified example of the fourth embodiment. In Fig. 11B, whether or not incident light has been received is detected for each pixel group 32 including two pixels 16 aligned in the first direction X. A SPAD 5 is arranged in one pixel 16a of the pixel group 32, and a photoconductive element 7 is arranged in the other pixel 16b.

[0109] The number of pixels 16 included in the pixel group 32 and the locations of the pixels 16 included in the pixel group 32 are arbitrary. In addition, the ratio of the pixels 16 having a SPAD 5 and the pixels 16 having a photoconductive element 7 included in the pixel group 32 is also arbitrary.

[0110] In this way, in the fourth embodiment, whether or not incident light has been received is detected for each pixel group 32, and a SPAD 5 or a photoconductive element 7 is arranged for each pixel 16, thereby improving the sensitivity of the SPAD 5 and the photoconductive element 7 and enabling the first transistor 6 to be sensitively switched on or off depending on the amount of incident light.

[0111] Fifth embodiment The photodetector 1 according to this embodiment can be used, for example, in a distance measuring system (also called a distance measuring module) 40 that measures the distance to an object in a non-contact manner. The distance measuring system 40 requires a photodetector (photoreceptor) 1 that receives the reflected light signal from the light emitting device 30, which is reflected by the object. The light emitting device 30 and the photodetector 1 may be disposed separately, or may be disposed on a common support member 42.

[0112] FIG. 12 is a cross-sectional view of a ToF sensor 43 in which the light emitting device 30 and the photodetector 1 are arranged on the same support member 42. As shown in FIG. 12, the light emitting device 30 and the photodetector 1 are supported by a common support member 42, and a light shielding wall 44 is arranged between the light emitting device 30 and the photodetector 1. The light emitting device 30 in FIG. 12 has an LDD substrate 4 and an LD chip 5 joined to each other, and a correction lens 7, similar to FIG. 1. The photodetector 1 in FIG. 12 has a light receiving element 45 and a condenser lens 46. The condenser lens 46 condenses a reflected light signal from an object and forms an image on the light receiving element.

[0113] (Configuration of distance measurement system 40) FIG. 12 shows an example of the configuration of a distance measuring system 40 as an implementation example of the light emitting device 30 according to this embodiment.

[0114] As shown in the figure, the distance measurement system 40 includes a light emitting unit 51, a driving unit 52, a power supply circuit 53, a light emitting side optical system 54, a light receiving side optical system 55, a light receiving unit 56, a signal processing unit 57, a control unit 58, and a temperature detection unit 59.

[0115] The light-emitting unit 51 emits light from a plurality of light sources. The light-emitting unit 51 and the light-emitting side optical system 54 correspond to the above-mentioned light-emitting device 30. As described later, the light-emitting unit 51 in this example has light-emitting elements 13 using VCSELs (Vertical Cavity Surface Emitting LASERs) as the respective light sources, and the light-emitting elements 13 are arranged in a predetermined manner, such as in a matrix.

[0116] The driving unit 52 is configured to have a power supply circuit 53 for driving the light emitting unit 51. The power supply circuit 53 generates a power supply voltage (a driving voltage Vd, described later) for the driving unit 52 based on an input voltage (an input voltage Vin, described later) from, for example, a battery (not shown) or the like provided in the distance measuring system 40. The driving unit 52 drives the light emitting unit 51 based on the power supply voltage.

[0117] Light emitted from the light-emitting unit 51 is irradiated onto a subject (object) S as a distance measurement target via a light-emitting side optical system 54. Then, the light thus irradiated is reflected from the subject S and enters a light-receiving surface of a light-receiving unit 56 via a light-receiving side optical system 55.

[0118] The light receiving unit 56 is a light receiving element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, which receives reflected light from the subject S incident via the light receiving side optical system 55 as described above, converts the light into an electrical signal, and outputs it. The light receiving unit 56 and the light receiving side optical system 55 correspond to the photodetector 1 shown in FIG.

[0119] The light receiving unit 56 performs, for example, CDS (Correlated Double Sampling) processing, AGC (Automatic Gain Control) processing, etc., on the electrical signal obtained by photoelectrically converting the received light, and further performs A / D (Analog / Digital) conversion processing. Then, the signal is output as digital data to the signal processing unit 57 at the downstream side.

[0120] Moreover, the light receiving unit 56 in this example outputs a frame synchronization signal Fs to the driving unit 52. This enables the driving unit 52 to cause the light emitting element 13 in the light emitting unit 51 to emit light at a timing corresponding to the frame period of the light receiving unit 56.

[0121] The signal processing unit 57 is configured as a signal processor, for example, a DSP (Digital Signal Processor), etc. The signal processing unit 57 performs various signal processes on the digital signal input from the light receiving unit 56.

[0122] The control unit 58 is configured with, for example, a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., or an information processing device such as a DSP, and controls the drive unit 52 for controlling the light emission operation by the light emitter 51, and controls the light receiving operation by the light receiver 56.

[0123] The control unit 58 has a function as a distance measuring unit 58a. The distance measuring unit 58a measures the distance to the subject S based on a signal input via the signal processing unit 57 (i.e., a signal obtained by receiving reflected light from the subject S). The distance measuring unit 58a in this example measures the distance to each part of the subject S in order to be able to identify the three-dimensional shape of the subject S. A specific distance measurement method in the distance measurement system 40 will be described later.

[0124] The temperature detection section 59 detects the temperature of the light-emitting section 51. The temperature detection section 59 may be configured to detect the temperature using, for example, a diode.

[0125] In this example, information on the temperature detected by the temperature detection unit 59 is supplied to the drive unit 52, which enables the drive unit 52 to drive the light emitting unit 51 based on the temperature information.

[0126] (Distance measurement method) As a distance measurement method in the distance measurement system 40, for example, a distance measurement method based on an STL (Structured Light) method or a ToF (Time of Flight) method can be adopted.

[0127] The STL method is a method for measuring distance based on an image of a subject S illuminated with light having a predetermined light / dark pattern, such as a dot pattern or a grid pattern.

[0128] Fig. 13A is an explanatory diagram of the STL method. In the STL method, a pattern light Lp having a dot pattern as shown in Fig. 13A is irradiated onto a subject S. The pattern light Lp is divided into a plurality of blocks BL, and a different dot pattern is assigned to each block BL (dot patterns are prevented from overlapping between blocks B).

[0129] FIG. 13B is a diagram illustrating the distance measurement principle of the STL method.

[0130] In this example, a wall W and a box BX placed in front of it are treated as a subject S, and pattern light Lp is irradiated onto the subject S. "G" in the figure diagrammatically represents the angle of view of the light receiving unit 56.

[0131] In addition, in the drawing, “BLn” denotes the light of a certain block BL in the pattern light Lp, and “dn” denotes the dot pattern of the block BLn projected on the light-receiving image by the light-receiving section 56.

[0132] Here, if there is no box BX in front of the wall W, the dot pattern of block BLn in the received light image is projected at the position of "dn'" in the figure. In other words, the position where the pattern of block BLn is projected in the received light image differs depending on whether or not there is a box BX; specifically, the pattern is distorted.

[0133] The STL method uses the fact that the irradiated pattern is distorted by the object shape of the subject S to determine the shape and depth of the subject S. Specifically, this method determines the shape and depth of the subject S from the way the pattern is distorted.

[0134] When the STL method is adopted, for example, an IR (Infrared) light receiving unit using a global shutter method is used as the light receiving unit 56. In the case of the STL method, the distance measuring unit 58a controls the driving unit 52 so that the light emitting unit 51 emits pattern light, detects distortion of the pattern from the image signal obtained via the signal processing unit 57, and calculates the distance based on the way the pattern is distorted.

[0135] Next, the ToF method is a method for measuring the distance to an object by detecting the flight time (time difference) of light emitted from the light-emitting unit 51, reflected by the object, and reaching the light-receiving unit 56.

[0136] When a so-called direct ToF (dTOF) method is adopted as the ToF method, a SPAD (Single Photon Avalanche Diode) is used as the light receiving unit 56, and the light emitting unit 51 is pulse-driven. In this case, the distance measuring unit 58a calculates the time difference between when light is emitted from the light emitting unit 51 and when it is received by the light receiving unit 56, based on a signal input via the signal processing unit 57, and calculates the distance to each part of the subject S based on the time difference and the speed of light.

[0137] When a so-called indirect ToF (iTOF) method (phase difference method) is adopted as the ToF method, a light receiving unit capable of receiving, for example, IR light is used as the light receiving unit 56.

[0138] <Applications to moving objects> The technology according to the present disclosure (the present 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 device, an airplane, a drone, a ship, a robot, etc.

[0139] FIG. 73 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a moving object control system to which the technology of the present disclosure can be applied.

[0140] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 73, 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. Also, as functional configurations 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.

[0141] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive 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.

[0142] The body system control unit 12020 controls the operation of various devices mounted on 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 head lamps, back lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves or signals of various switches transmitted from a portable device that replaces a key may be input to the body system control unit 12020. The body system control unit 12020 receives the input of these radio waves or signals and controls the door lock device, power window device, lamps, and the like of the vehicle.

[0143] The outside-vehicle 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 outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture an image outside the vehicle and receives the captured image. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for a person, a car, an obstacle, a sign, or characters on a road surface, based on the received image.

[0144] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal according to the amount of light received. The imaging unit 12031 can output the electrical signal as an image, or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0145] The in-vehicle 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 in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing.

[0146] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, the steering mechanism, or the braking device based on the information inside and outside the vehicle acquired by the outside-of-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output a control command to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the inter-vehicle distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane departure warning, etc.

[0147] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on the driver's operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle acquired by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0148] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12030 based on the information outside the vehicle acquired by the outside-vehicle information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside-vehicle information detection unit 12030, and perform cooperative control for the purpose of preventing glare, such as switching from high beams to low beams.

[0149] The audio / video output unit 12052 transmits at least one output signal of audio and video to an output device capable of visually or audibly notifying information to passengers in the vehicle or the outside of the vehicle. In the example of Fig. 73, an audio speaker 12061, a display unit 12062, and an instrument panel 12063 are exemplified as the output device. The display unit 12062 may include at least one of an on-board display and a head-up display, for example.

[0150] FIG. 74 is a diagram showing an example of the installation position of the imaging unit 12031.

[0151] In FIG. 74, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0152] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided at positions such as the front nose, side mirrors, rear bumper, back door, and the upper part of the windshield in the vehicle interior of the vehicle 12100. The imaging unit 12101 provided at the front nose and the imaging unit 12105 provided at the upper part of the windshield in the vehicle interior mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided at the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided at the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided at the upper part of the windshield in the vehicle interior is mainly used to detect a preceding vehicle, a pedestrian, an obstacle, a traffic light, a traffic sign, a lane, or the like.

[0153] 74 shows an example of the imaging ranges of the imaging units 12101 to 12104. An imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and an imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, an overhead image of the vehicle 12100 viewed from above is obtained by superimposing the image data captured by the imaging units 12101 to 12104.

[0154] 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 made up of a plurality of imaging elements, or may be an imaging element having pixels for detecting a phase difference.

[0155] For example, the microcomputer 12051 can extract, as a preceding vehicle, a three-dimensional object that is the closest three-dimensional object on the travel path of the vehicle 12100 and travels at a predetermined speed (for example, 0 km / h or more) in approximately the same direction as the vehicle 12100, by calculating the distance to each three-dimensional object in the imaging ranges 12111 to 12114 and the change over time of this distance (relative speed with respect to the vehicle 12100) based on the distance information obtained from the imaging units 12101 to 12104. Furthermore, the microcomputer 12051 can set a vehicle distance to be secured in advance in front of the preceding vehicle, and perform automatic brake control (including follow-up stop control) and automatic acceleration control (including follow-up start control). In this way, cooperative control can be performed for the purpose of automatic driving that travels autonomously without relying on the driver's operation.

[0156] For example, the microcomputer 12051 classifies and extracts three-dimensional object data on three-dimensional objects, such as two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects, based on the distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. Then, the microcomputer 12051 determines a collision risk indicating the degree of danger of collision with each obstacle, and when the collision risk is equal to or exceeds a set value and there is a possibility of collision, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0157] 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 or not a pedestrian is present in the captured images of the imaging units 12101 to 12104. The recognition of such 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 that indicate the contour of an object to determine whether or not the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the captured images of the imaging units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular contour line for emphasis on the recognized pedestrian. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating a pedestrian at a desired position.

[0158] An example of a vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to, for example, the imaging unit 12031, etc., among the configurations described above. Specifically, the light detection device 1 according to each embodiment can be applied to the imaging unit 12031. By applying the technology according to the present disclosure to the imaging unit 12031, a captured image that is easier to see can be obtained, thereby reducing driver fatigue.

[0159] The present technology can be configured as follows. (1) a light receiving element; a transistor for switching whether or not a current flows through the light receiving element; a photoconductive element that turns the transistor on or off in response to an amount of received light; a first resistor element that causes a current to flow through the light receiving element when the transistor is off; Light detection device. (2) when the transistor is on, a current flowing between the drain and source of the transistor flows to the light receiving element; When the transistor is off, the current flowing through the first resistor element flows to the light receiving element. The optical detection device according to (1). (3) the photoconductive element turns off the transistor when the amount of received light is equal to or greater than a predetermined reference amount, and turns on the transistor when the amount of received light is less than the reference amount; An optical detection device according to (1) or (2). (4) When the amount of light received by the photoconductive element is less than the reference amount, no current flows through the first resistive element, and when the amount of light received by the photoconductive element is equal to or greater than the reference amount, a current flows through the first resistive element. The optical detection device according to (3). (5) A plurality of pixels arranged in one or two dimensions, At least a part of the pixels includes the light receiving element, the transistor, the photoconductive element, and the first resistor element. An optical detection device according to any one of (1) to (4). (6) The photoconductive element corresponding to one of the light receiving elements is disposed along a boundary region between two adjacent pixels. The optical detection device according to (5). (7) a silicon layer having a photoelectric conversion region separated by the boundary region; a contact member disposed along the boundary region and penetrating the silicon layer; the photoconductive element is disposed along the boundary region on the light incident surface side of the silicon layer and is connected to the contact member; The light receiving element is configured using the photoelectric conversion region. The optical detection device according to (6). (8) The photoconductive element corresponding to one of the light receiving elements is Two photoconductive portions disposed separately along two adjacent boundary regions of the corresponding pixel; A wiring portion that electrically connects the two photoconductive portions, Each of the two photoconductive portions is connected to a corresponding one of the contact members. The optical detection device according to (7). (9) The photoconductive element corresponding to one of the light receiving elements is arranged in an L-shape along two adjacent boundary regions of the corresponding pixel. The optical detection device according to (7). (10) A silicon layer having a photoelectric conversion region separated by the boundary region, the photoconductive element is disposed on a side of the silicon layer farther from the light incident surface than the photoelectric conversion region; The light receiving element is configured using the photoelectric conversion region. The optical detection device according to (6). (11) A plurality of pixels arranged in one or two dimensions, The plurality of pixels include First pixels each having the light receiving element; a plurality of second pixels provided corresponding to the first pixels, each having the photoconductive element; The plurality of second pixels are arranged around the first pixel. An optical detection device according to any one of (1) to (4). (12) The photoconductive element is a laminate of a plurality of photoconductive layers each having at least one of a material and a film thickness different from each other, the plurality of photoconductive layers each change their resistance value in response to incidence of light of a different wavelength; An optical detection device according to any one of (1) to (11). (13) The transistor switches between allowing and not allowing a current to flow between a first node and a second node; one end of the light receiving element is connected to the second node; the photoconductive element switches between conducting and blocking electrical conduction between the second node and the gate of the transistor in response to an amount of received light; the first resistive element is connected between the first node and a gate of the transistor; An optical detection device according to any one of (1) to (12). (14) The photoconductive element brings the second node and the gate of the transistor into electrical continuity when the amount of received light is equal to or greater than a predetermined reference amount, and cuts off electrical continuity between the second node and the gate of the transistor when the amount of received light is less than the reference amount. (13) The optical detection device according to (13). (15) when the amount of light received by the photoconductive element is less than the reference amount, a first current path is generated through which a current flows from the first node through the transistor and the second node to the light receiving element; When the amount of light received by the photoconductive element is equal to or greater than the reference amount, the first current path is interrupted, and a second current path is generated through which a current flows from the first node to the light receiving element via the first resistor element and the photoconductive element. (14) The optical detection device according to claim 14. (16) The transistor switches between allowing and not allowing a current to flow between a first node and a second node; one end of the light receiving element is connected to the second node; the photoconductive element switches the voltage applied to the gate of the transistor in response to the amount of received light to switch the transistor on or off; the first resistor element is connected between the first node and the second node; An optical detection device according to any one of (1) to (12). (17) The photoconductive element turns off the transistor when the amount of received light is equal to or greater than a predetermined reference amount, and turns on the transistor when the amount of received light is less than the reference amount, when the amount of light received by the photoconductive element is less than the reference amount, a first current path is generated through which a current flows from the first node through the transistor and the second node to the light receiving element; When the amount of light received by the photoconductive element is equal to or greater than the reference amount, the first current path is interrupted, and a second current path is generated through which a current flows from the first node through the first resistor element and the second node to the light receiving element. (16) The optical detection device according to (16). (18) A second resistor element is connected to at least one of a current path through which a current passing through the transistor flows to the light receiving element and a current path through which a current passing through the first resistor element flows to the light receiving element. The optical detection device according to any one of (1) to (17). (19) A first substrate disposed on a light incident surface side; a second substrate laminated on the first substrate on the side opposite to the light incident surface, the light receiving element, the photoconductive element, and the first resistor element are disposed on the first substrate; the transistor is disposed on the second substrate; The first substrate and the second substrate transmit signals by bonding vias, bumps, or metal members. The optical detection device according to any one of (1) to (18). (20) a light emitting device for emitting an optical signal; a light receiving device that receives a reflected light signal of the light signal irradiated onto an object; a distance measuring device that measures a distance to the object based on the optical signal and the reflected optical signal, The light receiving device is A light receiving element; a transistor for switching whether or not a current flows through the light receiving element; a photoconductive element that turns the transistor on or off in response to an amount of received light; a first resistor element that causes a current to flow through the light receiving element when the transistor is off; Ranging system.

[0160] The aspects of the present disclosure are not limited to the above-mentioned individual embodiments, but include various modifications that may be conceived by a person skilled in the art, and the effects of the present disclosure are not limited to the above-mentioned contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and intent of the present disclosure derived from the contents defined in the claims and their equivalents. [Explanation of symbols]

[0161] REFERENCE SIGNS LIST 1 Light detection device, 2 Light receiving section, 3 Waveform shaping circuit, 5 Light receiving element, 6 First transistor, 7 Photoconductive element, 8 Quench resistor, 9 Second transistor, 10 Protection resistor, 11 First substrate, 12 Second substrate, 18 Contact member, 30 Light emitting device, 40 Distance measuring system, 42 Same support member, 43 Sensor

Claims

1. A light receiving element; a transistor for switching whether or not a current flows through the light receiving element; a photoconductive element that turns the transistor on or off in response to an amount of received light; a first resistor element that causes a current to flow through the light receiving element when the transistor is off; Light detection device.

2. When the transistor is on, a current flows between the drain and source of the transistor to the light receiving element, When the transistor is off, a current flowing through the first resistor element flows through the light receiving element.

2. The optical detection device according to claim 1.

3. the photoconductive element turns off the transistor when the amount of received light is equal to or greater than a predetermined reference amount, and turns on the transistor when the amount of received light is less than the reference amount; 2. The optical detection device according to claim 1.

4. When the amount of light received by the photoconductive element is less than the reference amount, no current flows through the first resistor element, and when the amount of light received by the photoconductive element is equal to or greater than the reference amount, a current flows through the first resistor element.

4. The optical detection device according to claim 3.

5. A plurality of pixels arranged in one or two dimensions, At least a part of the pixels includes the light receiving element, the transistor, the photoconductive element, and the first resistor element.

2. The optical detection device according to claim 1.

6. The photoconductive element corresponding to one of the light receiving elements is disposed along a boundary region between two adjacent pixels.

6. The optical detection device according to claim 5.

7. a silicon layer having a photoelectric conversion region partitioned by the boundary region; a contact member disposed along the boundary region and penetrating the silicon layer; the photoconductive element is disposed along the boundary region on the light incident surface side of the silicon layer and is connected to the contact member; The light receiving element is configured using the photoelectric conversion region.

7. The optical detection device according to claim 6.

8. The photoconductive element corresponding to one of the light receiving elements is two photoconductive portions disposed separately along two adjacent boundary regions of the corresponding pixel; a wiring portion for electrically connecting the two photoconductive portions, Each of the two photoconductive portions is connected to a corresponding one of the contact members.

8. The optical detection device according to claim 7.

9. the photoconductive element corresponding to one of the light receiving elements is disposed in an L-shape along two adjacent boundary regions of the corresponding pixel; 8. The optical detection device according to claim 7.

10. a silicon layer having a photoelectric conversion region separated by the boundary region; the photoconductive element is disposed on a side of the silicon layer farther from the light incident surface than the photoelectric conversion region; The light receiving element is configured using the photoelectric conversion region.

7. The optical detection device according to claim 6.

11. A plurality of pixels arranged in one or two dimensions, The plurality of pixels include First pixels each having the light receiving element; a plurality of second pixels provided corresponding to the first pixels, each having the photoconductive element; The plurality of second pixels are arranged around the first pixel.

2. The optical detection device according to claim 1.

12. the photoconductive element is a laminate of a plurality of photoconductive layers each having at least one of a material and a film thickness different from each other; the plurality of photoconductive layers each change their resistance value in response to incidence of light of a different wavelength; 2. The optical detection device according to claim 1.

13. The transistor switches between allowing and not allowing a current to flow between a first node and a second node; one end of the light receiving element is connected to the second node; the photoconductive element switches between conducting and blocking electrical connection between the second node and the gate of the transistor in response to an amount of received light; the first resistive element is connected between the first node and a gate of the transistor; 2. The optical detection device according to claim 1.

14. the photoconductive element brings the second node and the gate of the transistor into electrical continuity when the amount of received light is equal to or greater than a predetermined reference amount, and cuts off electrical continuity between the second node and the gate of the transistor when the amount of received light is less than the reference amount; 14. The optical detection device of claim 13.

15. When the amount of light received by the photoconductive element is less than the reference amount, a first current path is generated through which a current flows from the first node through the transistor and the second node to the light receiving element; When the amount of light received by the photoconductive element is equal to or greater than the reference amount, the first current path is interrupted, and a second current path is generated through which a current flows from the first node to the light receiving element via the first resistor element and the photoconductive element.

15. The optical detection device of claim 14.

16. The transistor switches between allowing and not allowing a current to flow between a first node and a second node; one end of the light receiving element is connected to the second node; the photoconductive element switches the voltage applied to the gate of the transistor in response to the amount of received light to switch the transistor on or off; the first resistor element is connected between the first node and the second node; 2. The optical detection device according to claim 1.

17. the photoconductive element turns off the transistor when the amount of received light is equal to or greater than a predetermined reference amount, and turns on the transistor when the amount of received light is less than the reference amount; When the amount of light received by the photoconductive element is less than the reference amount, a first current path is generated through which a current flows from the first node through the transistor and the second node to the light receiving element; When the amount of light received by the photoconductive element is equal to or greater than the reference amount, the first current path is interrupted, and a second current path is generated through which a current flows from the first node through the first resistor element and the second node to the light receiving element.

17. The optical detection device of claim 16.

18. a second resistor element connected to at least one of a current path through which a current passing through the transistor flows to the light receiving element and a current path through which a current passing through the first resistor element flows to the light receiving element; 2. The optical detection device according to claim 1.

19. A first substrate disposed on the light incident surface side; a second substrate laminated on the first substrate on the side opposite to the light incident surface, the light receiving element, the photoconductive element, and the first resistor element are disposed on the first substrate; the transistor is disposed on the second substrate; The first substrate and the second substrate transmit signals by bonding vias, bumps, or metal members.

2. The optical detection device according to claim 1.

20. A light emitting device that projects an optical signal; a light receiving device that receives a reflected light signal of the light signal irradiated onto an object; a distance measuring device that measures a distance to the object based on the optical signal and the reflected optical signal, The light receiving device is A light receiving element; a transistor for switching whether or not a current flows through the light receiving element; a photoconductive element that turns the transistor on or off in response to an amount of received light; a first resistor element that causes a current to flow through the light receiving element when the transistor is off; Ranging system.

Images