Light detection device

Abstract

[Problem] To provide a light detection device with which dead time can be reduced without adversely affecting PDE characteristics. [Solution] A light detection device according to an embodiment of the present disclosure comprises an avalanche photodiode, at least one resistance element, and a plurality of transistors that switch the electrical connection between the avalanche photodiode and the resistance element.

Description

Optical detection device

[0001] The present disclosure relates to an optical detection device.

[0002] An optical detection device used in a ToF (Time Of Flight) distance measurement sensor or a photon counter is provided with an avalanche photodiode typified by a SPAD (Single Photon Avalanche Diode). The dynamic range characteristics of such an avalanche photodiode depend on the dead time and the PDE (Photon Detection Efficiency). In order to obtain desired PDE characteristics, when the excess voltage applied to the avalanche photodiode is increased, the swing amount of the cathode becomes large. In this case, the dead time becomes long, and as a result, photon count loss is likely to occur in a high-light-intensity illumination environment.

[0003] Japanese Unexamined Patent Application Publication No. 2019-7877

[0004] The present disclosure provides an optical detection device capable of reducing the dead time without deteriorating the PDE characteristics.

[0005] The optical detection device according to an embodiment of the present disclosure includes an avalanche photodiode, at least one resistive element, and a plurality of transistors that switch the electrical connection between the avalanche photodiode and the resistive element.

[0006] The at least one resistive element includes a first resistive element and a second resistive element having a resistance value different from that of the first resistive element, and the plurality of transistors include a first transistor connected to the avalanche photodiode via the first resistive element and a second transistor connected to the avalanche photodiode via the second resistive element.

[0007] The resistive element is a resistive wire, one end of the resistive wire is connected to the avalanche photodiode, and the plurality of transistors may include a first transistor connected to the other end of the resistive wire and a second transistor connected in the middle of the resistive wire.

[0008] The plurality of transistors may include a first MOS transistor and a second MOS transistor having the same conductivity type as the first MOS transistor, wherein the gate of the first MOS transistor is connected to a first signal line and the gate of the second MOS transistor is connected to a second signal line different from the first signal line.

[0009] The plurality of transistors may include a first MOS transistor and a second MOS transistor having the opposite conductivity to the first MOS transistor, and the gates of the first MOS transistor and the second MOS transistor may be connected in common to a single signal line.

[0010] The light detection device further comprises a pixel array in which a plurality of pixels are arranged in a matrix, wherein the plurality of pixels include a first pixel having the avalanche photodiode, the at least one resistive element, and the plurality of transistors, and a second pixel having the same circuit configuration as the first pixel, wherein in the first pixel, the gates of the plurality of transistors are commonly connected to a first signal line, and in the second pixel, the gates of the plurality of transistors may be commonly connected to a second signal line different from the first signal line.

[0011] In the aforementioned pixel array, the first pixels may be arranged in odd-numbered rows, and the second pixels may be arranged in even-numbered rows.

[0012] In the aforementioned pixel array, the first pixels may be arranged in odd-numbered rows, and the second pixels may be arranged in even-numbered rows.

[0013] The light detection device may further include an illuminance meter for measuring the amount of light incident on the light detection device, and a control circuit for controlling the plurality of transistors based on the measured value of the illuminance meter.

[0014] The control circuit may set the level of the first control signal transmitted through the first signal line and the level of the second control signal transmitted through the second signal line based on the measured value.

[0015] The light detection device may further include a constant current source for controlling the recharge current of the avalanche photodiode.

[0016] The at least one resistive element may include a first resistive element and a second resistive element connected in parallel with the first resistive element, and the plurality of transistors may include a first transistor connected to the avalanche photodiode via the first resistive element, a second transistor connected to the avalanche photodiode without going through the first or second resistive element, and a third transistor connected to the avalanche photodiode via the second resistive element.

[0017] This figure shows the circuit configuration of the photodetector according to the first embodiment. This is a cross-sectional view of the main part of the photodetector shown in Figure 1. This is a timing chart showing the changes in cathode voltage and output voltage when the control signal is at a low level. This is a timing chart showing the changes in cathode voltage and output voltage when the control signal is at a high level. This figure shows the circuit configuration of the photodetector according to a comparative example. This is a timing chart for explaining the operation of the photodetector 100 according to a comparative example. This figure shows the circuit configuration of the photodetector according to the second embodiment. This figure shows the circuit configuration of the photodetector according to the third embodiment. This is a cross-sectional view of the main part of the photodetector shown in Figure 7. This figure shows the circuit configuration of the photodetector according to a modified example of the third embodiment. This figure shows the circuit configuration of the photodetector according to the fourth embodiment. This is a cross-sectional view of the main part of the photodetector shown in Figure 10. This is a timing chart showing the changes in cathode voltage and output voltage under low-light illumination conditions. This is a timing chart showing the changes in cathode voltage and output voltage under high-light illumination conditions. This is a plan view showing the schematic configuration of the photodetector according to the fifth embodiment. This figure shows the circuit configuration of the first pixel. This figure shows the circuit configuration of the second pixel. This is a plan view showing the schematic configuration of the photodetector according to the sixth embodiment. This figure shows the circuit configuration of the photodetector according to the seventh embodiment. Figure 16 is a cross-sectional view of the main part of the light detection device. Figure 17 is a cross-sectional view along the cutting line A-A. This is a plan view showing the schematic configuration of the light detection device according to the eighth embodiment. This is a diagram showing an example of the pixel circuit configuration. This is a diagram showing an example of the correlation between the illuminance meter measurement value and the control signal level. This is a plan view showing the schematic configuration of the light detection device according to the ninth embodiment. This is a diagram showing an example of the correlation between the illuminance meter measurement value and the levels of the first control signal and the second control signal. This is a diagram showing the circuit configuration of the light detection device according to the tenth embodiment. Figure 24 is a cross-sectional view of the main part of the light detection device. Figure 25 is a cross-sectional view along the cutting line B-B. Figure 25 is a cross-sectional view along the cutting line C-C. This is a diagram showing the circuit configuration of the light detection device according to the eleventh embodiment. This is a block diagram showing an example of the schematic configuration of the vehicle control system. This is an explanatory diagram showing an example of the installation position of the external information detection unit and the imaging unit.

[0018] Preferred embodiments of this disclosure will be described in detail below with reference to the attached drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0019] (First Embodiment) Figure 1 is a diagram showing the circuit configuration of a photodetector according to the first embodiment. Figure 2 is a cross-sectional view of the main part of the photodetector shown in Figure 1. The photodetector 1 shown in Figures 1 and 2 comprises an avalanche photodiode PD, a first transistor Tr1, a second transistor Tr2, a resistor R, and an inverter element INV.

[0020] An avalanche photodiode PD is a light-receiving element, exemplified by SPADs. A negative voltage is applied to the anode terminal A of the avalanche photodiode PD. The cathode terminal K of the avalanche photodiode PD is connected to a first transistor Tr1 via a resistor R, and also to a second transistor Tr2.

[0021] The first transistor Tr1 is an n-channel conductive MOS transistor. The gate of the first transistor Tr1 is connected to the first signal line SW1. The drain is connected to the inverter element INV. The source is connected to the resistor element R. The first transistor Tr1 turns on and off depending on the level of the control signal input to the gate from the first signal line SW1. When the control signal is high level, the first transistor Tr1 is in the ON state, and when the control signal is low level, the first transistor Tr1 is in the OFF state.

[0022] The second transistor Tr2 is a p-channel conductive MOS transistor. The gate of the second transistor Tr2 is connected to the first signal line SW1. The drain is connected to the inverter element INV. The source is connected to the cathode terminal K of the avalanche photodiode PD. The second transistor Tr2 turns on and off according to the level of the control signal common to the first transistor Tr1. When the control signal is low level, the second transistor Tr2 is ON, and when the control signal is high level, the second transistor Tr2 is OFF.

[0023] One end of the resistor R is connected to the cathode terminal K of the avalanche photodiode PD, and the other end is connected to the source of the first transistor Tr1. The resistor R is positioned below the first transistor Tr1, as shown in Figure 2. The resistor R is made of, for example, polysilicon.

[0024] The input terminals of the inverter element INV are connected to the drains of the first transistor Tr1 and the second transistor Tr2, respectively. The voltage Vout at the output terminal OUT of the inverter element INV changes to a high or low level depending on the comparison result between the voltage Vcathode at the cathode terminal K of the avalanche photodiode PD and the threshold voltage Vth.

[0025] The operation of the photodetector 1 configured as described above will be explained below with reference to Figures 3A and 3B. In this operation, a negative voltage is applied to the anode terminal A of the avalanche photodiode PD.

[0026] Figure 3A is a timing chart showing the changes in cathode voltage Vcathode and output voltage Vout when the control signal is low level. When the control signal is low level, the first transistor Tr1 is in the off state and the second transistor Tr2 is in the on state. Therefore, the cathode terminal K is connected to the inverter element INV without going through the resistor element R.

[0027] In Geiger mode, when the cathode voltage Vcathode falls below the threshold voltage Vth, the output voltage Vout changes from a low level to a high level. The cathode voltage Vcathode then drops to the quench voltage Vq. Subsequently, when the cathode voltage Vcathode increases and exceeds the threshold voltage Vth, the output voltage Vout changes from a high level to a low level.

[0028] Figure 3B is a timing chart showing the changes in cathode voltage Vcathode and output voltage Vout when the control signal is high level. When the control signal is high level, the first transistor Tr1 is ON and the second transistor Tr2 is OFF. Therefore, the cathode terminal K is connected to the inverter element INV via the resistor element R. Even in this state, when the cathode voltage Vcathode falls below the threshold voltage Vth, the output voltage Vout changes from a low level to a high level. The cathode voltage Vcathode decreases to the quench voltage Vq. After that, when the cathode voltage Vcathode increases and exceeds the threshold voltage Vth, the output voltage Vout changes from a high level to a low level.

[0029] In Figure 3B, since the cathode terminal K is connected to the resistive element R, a voltage V1, which is the product of the recharge current value and the resistance value of the resistive element R, is applied to the cathode voltage Vcathode. As a result, the quench voltage Vq is boosted to near the threshold voltage Vth. Consequently, the swing amount, which represents the difference between the power supply voltage VDD and the quench voltage Vq, becomes smaller.

[0030] Here, a comparative example to be compared with this embodiment will be described with reference to Figures 4 and 5.

[0031] Figure 4 shows the circuit configuration of a photodetector according to a comparative example. The photodetector 100 shown in Figure 4 differs from the photodetector 1 according to the first embodiment in that it does not include a first transistor Tr1, a second transistor Tr2, and a resistive element R.

[0032] Figure 5 is a timing chart illustrating the operation of the photodetector 100 in the comparative example. In this comparative example as well, when the cathode voltage Vcathode falls below the threshold voltage Vth, the output voltage Vout changes from a low level to a high level. Subsequently, when the cathode voltage Vcathode increases from the quench voltage Vq and exceeds the threshold voltage Vth, the output voltage Vout changes from a high level to a low level.

[0033] In the photodetector 100 of this comparative example, increasing the overvoltage applied between the terminals of the avalanche photodiode PD in order to obtain the desired PDE increases the swing amount Vm. In this case, the dead time tdead, which corresponds to the time from when the cathode voltage Vcathode falls below the threshold voltage Vth to when it rises above it, is extended. As a result, photon count loss is more likely to occur in high-light illumination environments.

[0034] In contrast, in the light detection device 1 according to this embodiment, the switching operation of the first transistor Tr1 and the second transistor Tr2 can switch whether or not a resistive element R is electrically connected to the cathode terminal K of the avalanche photodiode PD. Specifically, in a high-light illumination environment, the first transistor Tr1 is turned on while the second transistor Tr2 is turned off, thereby generating a current path from the cathode terminal K to the inverter element INV via the resistive element R. In a low-light illumination environment, the first transistor Tr1 is turned off while the second transistor Tr2 is turned on, thereby generating a current path from the cathode terminal K to the inverter element INV without going through the resistive element R.

[0035] When the cathode terminal K is connected to the resistive element R, as shown in Figure 3B, the quench voltage Vq is boosted to near the threshold voltage Vth due to the voltage drop. As a result, the swing amount Vm is reduced, and the dead time tdead can be reduced without lowering the excess voltage. In other words, the dead time tdead can be reduced without degrading the PDE characteristics. Furthermore, it becomes possible to improve the photon count loss in high-light illumination environments and widen the dynamic range.

[0036] (Second Embodiment) Figure 6 shows the circuit configuration of the photodetector according to the second embodiment. In the photodetector 2 according to this embodiment, the first transistor Tr1 is a p-channel conductive MOS transistor, and the second transistor Tr2 is an n-channel conductive MOS transistor. In other words, the conductivity type of each transistor is the opposite of that in the first embodiment.

[0037] Under low-light conditions, a high-level control signal is input to the gates of the first transistor Tr1 and the second transistor Tr2 via the first signal line SW1. In this case, the first transistor Tr1 is in the off state, and the second transistor Tr2 is in the on state.

[0038] On the other hand, under high-light illumination conditions, a low-level control signal is input to the gates of the first transistor Tr1 and the second transistor Tr2 via the first signal line SW1. In this case, the first transistor Tr1 is turned on, and the second transistor Tr2 is turned off. At this time, the cathode terminal K is connected to the resistive element R, so, similar to the first embodiment, the quench voltage Vq is boosted to near the threshold voltage Vth due to the voltage drop. As a result, the swing amount Vm is reduced, and the dead time tdead can be reduced without reducing the excess voltage.

[0039] Therefore, in this embodiment as well, it is possible to reduce the dead time tdead without degrading the PDE characteristics.

[0040] (Third Embodiment) Figure 7 is a diagram showing the circuit configuration of the light detection device according to the third embodiment. Figure 8 is a cross-sectional view of the main part of the light detection device shown in Figure 7.

[0041] In the photodetector 3 according to this embodiment, both the first transistor Tr1 and the second transistor Tr2 are p-channel conductive MOS transistors. That is, in this embodiment, the conductivity type of the first transistor Tr1 is the same as that of the second transistor Tr2.

[0042] The gate of the first transistor Tr1 is connected to the first signal line SW1, and the gate of the second transistor Tr2 is connected to the second signal line SW2. The second signal line SW2 is formed on the same layer as the first signal line SW1, as shown in Figure 8.

[0043] The first control signal input to the gate of the first transistor Tr1 through the first signal line SW1 is inverted with respect to the second control signal input to the gate of the second transistor Tr2 through the second signal line SW2. That is, when one of the first control signal and the second control signal is at a high level, the other is at a low level.

[0044] In a low light intensity illumination environment, a high-level first control signal is input to the gate of the first transistor Tr1 through the first signal line SW1, and at the same time, a low-level second control signal is input to the gate of the second transistor Tr2 through the second signal line SW2. In this case, the first transistor Tr1 is in an off state, and the second transistor Tr2 is in an on state.

[0045] On the other hand, in a high light intensity illumination environment, a low-level first control signal is input to the gate of the first transistor Tr1 through the first signal line SW1, and at the same time, a high-level second control signal is input to the gate of the second transistor Tr2 through the second signal line SW2. In this case, the first transistor Tr1 is in an on state, and the second transistor Tr2 is in an off state. At this time, since the cathode terminal K is connected to the resistance element R, similar to the first embodiment, the quench voltage Vq is boosted to near the threshold voltage Vth by the voltage drop. As a result, since the swing amount Vm becomes small, it is possible to reduce the dead time tdead without reducing the overvoltage.

[0046] Therefore, also in this embodiment, it is possible to reduce the dead time tdead without deteriorating the PDE characteristics. Further, in this embodiment, since the conductivity types of the first transistor Tr1 and the second transistor Tr2 are the same, it is possible to reduce the load on the manufacturing process as compared with the case where the conductivity types are different.

[0047] (Modification Example) FIG. 9 is a diagram showing a circuit configuration of a photodetection device according to a modification example of the third embodiment. The photodetection device 3a according to this modification example is different from the third embodiment in that both the first transistor Tr1 and the second transistor Tr2 are n-channel MOS transistors. Therefore, in a low-light illumination environment, a low-level first control signal is input to the gate of the first transistor Tr1 through the first signal line SW1, and at the same time, a high-level second control signal is input to the gate of the second transistor Tr2 through the second signal line SW2. In this case, the first transistor Tr1 is turned off, and the second transistor Tr2 is turned on.

[0048] On the other hand, in a high-light illumination environment, a high-level first control signal is input to the gate of the first transistor Tr1 through the first signal line SW1, and at the same time, a low-level second control signal is input to the gate of the second transistor Tr2 through the second signal line SW2. In this case, the first transistor Tr1 is turned on, and the second transistor Tr2 is turned off. At this time, since the cathode terminal K is connected to the resistance element R, similar to the third embodiment, the quench voltage Vq is boosted to near the threshold voltage Vth by the voltage drop. As a result, since the swing amount Vm becomes small, it is possible to reduce the dead time tdead without reducing the overvoltage.

[0049] Therefore, also in this modification example, it is possible to reduce the dead time tdead without deteriorating the PDE characteristics. Also, in this modification example, since the conductivity types of the first transistor Tr1 and the second transistor Tr2 are the same, it is possible to reduce the load on the manufacturing process compared to the case where the conductivity types are different.

[0050] (Fourth Embodiment) FIG. 10 is a diagram showing a circuit configuration of a photodetection device according to the fourth embodiment. FIG. 11 is a cross-sectional view of a main part of the photodetection device shown in FIG. 10.

[0051] In the photodetector 4 according to this embodiment, a first resistive element R1 is provided between the cathode terminal K of the avalanche photodiode PD and the source of the first transistor Tr1, and a second resistive element R2 is provided between the cathode terminal K of the avalanche photodiode PD and the source of the second transistor Tr2. In this embodiment, the resistance value of the first resistive element R1 is greater than the resistance value of the second resistive element R2. That is, in this embodiment, the first resistive element R1 and the second resistive element R2, which have different resistance values, are connected to the cathode terminal K.

[0052] The operation of the photodetector 4 configured as described above will be explained below with reference to Figures 12A and 12B. In this operation, a negative voltage is applied to the anode terminal A of the avalanche photodiode PD.

[0053] Figure 12A is a timing chart showing the changes in cathode voltage Vcathode and output voltage Vout under low-light illumination conditions. Under low-light illumination conditions, a low-level control signal is input to the gates of the first transistor Tr1 and the second transistor Tr2 via the first signal line SW1. In this case, the first transistor Tr1 is in the off state and the second transistor Tr2 is in the on state. Therefore, the cathode terminal K is connected to the second resistor R2, which is set to a low resistance value.

[0054] Figure 12B is a timing chart showing the changes in cathode voltage Vcathode and output voltage Vout under high-light illumination conditions. Under high-light illumination conditions, a high-level control signal is input to the gates of the first transistor Tr1 and the second transistor Tr2 via the first signal line SW1. In this case, the first transistor Tr1 is in the ON state and the second transistor Tr2 is in the OFF state. As a result, the cathode terminal K is connected to the first resistor element R1, which is set to a high resistance value. Therefore, due to the voltage drop, the quench voltage Vq is increased to near the threshold voltage Vth compared to when the second resistor element R2 is connected to the cathode terminal K. As a result, the swing amount Vm is reduced, and the dead time tdead can be reduced without reducing the excess voltage.

[0055] Therefore, in this embodiment as well, it is possible to reduce the dead time tdead without degrading the PDE characteristics.

[0056] (Fifth Embodiment) Figure 13 is a plan view showing a schematic configuration of the light detection device according to the fifth embodiment. The light detection device 5 according to this embodiment has a pixel array 20. In the pixel array 20, first pixels 201 and second pixels 202 are arranged in a two-dimensional matrix. In this embodiment, the first pixels 201 are arranged in odd-numbered columns, and the second pixels 202 are arranged in even-numbered columns. The minimum period of the light detection device 5 according to this embodiment is the operating period of one first pixel 201 and one second pixel 202 adjacent in the row direction (X direction). Note that the first pixels 201 may be arranged in even-numbered columns, and the second pixels 202 may be arranged in odd-numbered columns.

[0057] Figure 14A shows the circuit configuration of the first pixel 201. Figure 14B shows the circuit configuration of the second pixel 202. As shown in Figures 14A and 14B, the circuit configurations of the first pixel 201 and the second pixel 202 are the same. However, in the first pixel 201, the gates of the first transistor Tr1 and the second transistor Tr2 are connected to the first signal line SW1. On the other hand, in the second pixel 202, the gates of the first transistor Tr1 and the second transistor Tr2 are connected to the second signal line SW2. In this embodiment, the first signal line SW1 is an odd-numbered signal line, and the second signal line SW2 is an even-numbered signal line.

[0058] In the light detection device 5 according to this embodiment, configured as described above, if, for example, the first pixel 201 is set to detect high-intensity light and the second pixel 202 is set to detect low-intensity light, a high-level control signal is constantly input to the gates of the first transistor Tr1 and the second transistor Tr2 through the first signal line SW1. At the same time, a low-level control signal is constantly input to the gates of the first transistor Tr1 and the second transistor Tr2 through the second signal line SW2.

[0059] In the above case, in the first pixel 201, the cathode terminal K of the avalanche photodiode PD is always electrically connected to the resistive element R, while in the second pixel 202, the cathode terminal K of the avalanche photodiode PD is not always electrically connected to the resistive element R. In the first pixel 201, the quench voltage Vq is boosted to near the threshold voltage Vth, so the swing amount Vm becomes smaller, and as a result, the dead time tdead can be reduced without lowering the overvoltage.

[0060] Therefore, according to this embodiment, the dead time tdead can be reduced without degrading the PDE characteristics. In addition, in this embodiment, both pixel regions for detecting high-intensity light and pixel regions for detecting low-intensity light are mixed within the pixel array 20. As a result, it is possible to reduce photon count loss even in lighting environments with large changes in background light.

[0061] (Sixth Embodiment) Figure 15 is a plan view showing a schematic configuration of the photodetector according to the sixth embodiment. Here, the differences from the fifth embodiment described above will be explained in detail.

[0062] In the pixel array 20 of the light detection device 6 according to this embodiment, the first pixels 201 are arranged in odd-numbered rows, and the second pixels 202 are arranged in even-numbered rows. Furthermore, the minimum period of the light detection device 6 according to this embodiment is the operating period of one adjacent first pixel 201 and one adjacent second pixel 202 in the column direction (Y direction). Note that the first pixels 201 may be arranged in even-numbered rows, and the second pixels 202 may be arranged in odd-numbered rows.

[0063] The circuit configurations of the first pixel 201 and the second pixel 202 are the same as in the fifth embodiment. In this embodiment, the odd-numbered first signal line SW1 is connected to the gates of the first transistor Tr1 and the second transistor Tr2 located in the first pixel 201. On the other hand, the even-numbered second signal line SW2 is connected to the gates of the first transistor Tr1 and the second transistor Tr2 located in the second pixel 202.

[0064] In the light detection device 6 according to this embodiment, configured as described above, if, for example, the first pixel 201 is set to detect high-intensity light and the second pixel 202 is set to detect low-intensity light, a high-level control signal is constantly input to the gates of the first transistor Tr1 and the second transistor Tr2 through the first signal line SW1. At the same time, a low-level control signal is constantly input to the gates of the first transistor Tr1 and the second transistor Tr2 through the second signal line SW2.

[0065] In the above case, in the first pixel 201, the cathode terminal K of the avalanche photodiode PD is always electrically connected to the resistive element R, while in the second pixel 202, the cathode terminal K of the avalanche photodiode PD is not always electrically connected to the resistive element R. In the first pixel 201, the quench voltage Vq is boosted to near the threshold voltage Vth, so the swing amount Vm becomes smaller, and as a result, the dead time tdead can be reduced without lowering the overvoltage.

[0066] Therefore, according to this embodiment, similar to the first embodiment, it is possible to reduce the dead time tdead without degrading the PDE characteristics. Furthermore, in this embodiment, similar to the fifth embodiment, both pixel regions for detecting high-intensity light and pixel regions for detecting low-intensity light are mixed within the pixel array 20. As a result, it is possible to reduce photon count loss even in lighting environments where background light changes significantly.

[0067] (Seventh Embodiment) Figure 16 is a diagram showing the circuit configuration of the light detection device according to the seventh embodiment. Figure 17 is a cross-sectional view of the main part of the light detection device shown in Figure 16. Figure 18 is a cross-sectional view along the cutting line A-A shown in Figure 17.

[0068] In this embodiment, as shown in Figure 16, both the first transistor Tr1 and the second transistor Tr2 are connected to the cathode terminal K of the avalanche photodiode PD via a resistor R. Specifically, as shown in Figure 17, the cathode terminal K is connected to the resistor R via a contact plug 71. The source of the first transistor Tr1 is connected to the resistor R via a contact plug 72. The source of the second transistor Tr2 is connected to the resistor R via a contact plug 73.

[0069] As shown in Figure 18, the resistive element R according to this embodiment is a resistive wire. The cathode terminal K of the avalanche photodiode PD is connected to one end of this resistive wire via a contact plug 71. The first transistor Tr1 is connected to the other end of this resistive wire via a contact plug 72. Furthermore, the second transistor Tr2 is connected to the middle of this resistive wire via a contact plug 73. As a result, the length of the resistive wire between the cathode terminal K and the first transistor Tr1 is longer than the length of the resistive wire between the cathode terminal K and the second transistor Tr2. Therefore, the resistance value between the cathode terminal K and the first transistor Tr1 is greater than the resistance value of the resistive element R between the cathode terminal K and the second transistor Tr2.

[0070] In the light detection device 7 configured as described above, a control signal is input to the gates of each transistor via the first signal line SW1 so that the first transistor Tr1 is turned off and the second transistor Tr2 is turned on in a low-light illumination environment.

[0071] On the other hand, under high-light illumination conditions, a control signal is input to the gates of each transistor via the first signal line SW1, causing the first transistor Tr1 to turn on and the second transistor Tr2 to turn off. As a result, the cathode terminal K is connected to a resistor R with a long wiring length. Therefore, the quench voltage Vq is boosted to near the threshold voltage Vth due to the voltage drop. Consequently, the swing amount Vm is reduced, and the dead time tdead can be reduced without lowering the excess voltage.

[0072] Therefore, in this embodiment as well, it is possible to reduce the dead time tdead without degrading the PDE characteristics.

[0073] (Eighth Embodiment) Figure 19 is a plan view showing a schematic configuration of a light detection device according to the eighth embodiment. The light detection device 8 according to this embodiment comprises a pixel array 20, an illuminance meter 30, and a control circuit 40. In the pixel array 20, pixels 200 are arranged in a two-dimensional matrix.

[0074] Figure 20 shows an example of the circuit configuration of pixel 200. Since pixel 200 has the same circuit configuration as the light detection device 1 according to the first embodiment described above, a detailed explanation is omitted.

[0075] The illuminance meter 30 measures the amount of light incident on the light detection device 8. The measured value from the illuminance meter 30 is input to the control circuit 40.

[0076] The control circuit 40 is connected to the pixel 200 via the first signal line SW1. The control circuit 40 sets the level of the control signal SG transmitted on the first signal line SW1 according to the measurement value of the illuminance meter 30.

[0077] Figure 21 shows an example of the correlation between the measured value of the illuminance meter 30 and the level of the control signal SG. In Figure 21, the horizontal axis represents the measured value of the illuminance meter 30, and the vertical axis represents the level of the control signal SG. In Figure 21, the control circuit 40 sets the control signal SG to a low level until the measured value reaches 100 μW. When the measured value reaches 100 μW, the control circuit 40 changes the control signal SG from a low level to a high level.

[0078] In this embodiment, an illumination environment in which the measured value does not reach 100 μW corresponds to a low-light illumination environment. In this case, the control circuit 40 simultaneously outputs a low-level control signal SG to the gates of the first transistor Tr1 and the second transistor Tr2. In this case, the first transistor Tr1 is turned off and the second transistor Tr2 is turned on. As a result, the cathode terminal K of the avalanche photodiode PD is not electrically connected to the resistive element R.

[0079] Furthermore, an illumination environment where the measured value exceeds 100 μW corresponds to a high-intensity illumination environment. In this case, the control circuit 40 simultaneously outputs a high-level control signal SG to the gates of the first transistor Tr1 and the second transistor Tr2. In this case, the first transistor Tr1 is turned on, and the second transistor Tr2 is turned off. As a result, the cathode terminal K of the avalanche photodiode PD is electrically connected to the resistive element R. Therefore, due to the voltage drop, the quench voltage Vq is raised to near the threshold voltage Vth compared to when the second resistive element R2 is connected to the cathode terminal K. As a result, the swing amount Vm is reduced, and the dead time tdead can be reduced without reducing the excess voltage.

[0080] Therefore, in this embodiment as well, it is possible to reduce the dead time tdead without degrading the PDE characteristics.

[0081] (Ninth Embodiment) Figure 22 is a plan view showing a schematic configuration of the light detection device according to the ninth embodiment. The light detection device 9 according to this embodiment includes a pixel array 20, an illuminance meter 30, and a control circuit 40, similar to the eighth embodiment described above. In the pixel array 20, similar to the sixth embodiment, the first pixels 201 are arranged in odd-numbered rows, and the second pixels 202 are arranged in even-numbered rows. The circuit configurations of the first pixels 201 and the second pixels 202 are the same as in the sixth embodiment, so their description is omitted.

[0082] The illuminance meter 30 measures the amount of light incident on the light detection device 9. The measured value from the illuminance meter 30 is input to the control circuit 40.

[0083] The control circuit 40 is connected to the first pixel 201 via the first signal line SW1 and to the second pixel 202 via the second signal line SW2. The control circuit 40 sets the level of the first control signal SG1 that transmits through the first signal line SW1 and the level of the second control signal SG2 that transmits through the second signal line SW2, according to the measurement value of the illuminance meter 30.

[0084] Figure 23 shows an example of the correlation between the measured values ​​of the illuminance meter 30 and the levels of the first control signal SG1 and the second control signal SG2. In Figure 23, the horizontal axis shows the measured values ​​of the illuminance meter 30, and the vertical axis shows the levels of each control signal.

[0085] In Figure 23, the control circuit 40 sets the first control signal SG1 to a low level until the measured value reaches 100 μW, and then changes it from a low level to a high level once the measured value reaches 100 μW. The control circuit 40 also sets the second control signal SG2 to a low level until the measured value reaches 200 μW, and then changes it from a low level to a high level once the measured value reaches 200 μW.

[0086] In this embodiment, in lighting environments where the measured value does not reach 100 μW, the control circuit 40 sets both the first control signal SG1 and the second control signal SG2 to a low level. In this case, at the first pixel 201 and the second pixel 202, the first transistor Tr1 is turned off and the second transistor Tr2 is turned on. As a result, the cathode terminal K of the avalanche photodiode PD is not electrically connected to the resistive element R.

[0087] Furthermore, in lighting environments where the measured value exceeds 100 μW but does not reach 200 μW, the control circuit 40 changes the first control signal SG1 to a high level while maintaining the second control signal SG2 at a low level. In this case, in the first pixel 201, the first transistor Tr1 is turned on and the second transistor Tr2 is turned off. As a result, the cathode terminal K of the avalanche photodiode PD is electrically connected to the resistive element R. On the other hand, in the second pixel 202, the off state of the first transistor Tr1 and the on state of the second transistor Tr2 are maintained.

[0088] Furthermore, in lighting environments where the measured value exceeds 200 μW, the control circuit 40 sets not only the first control signal SG1 but also the second control signal SG2 to a high level. In this case, in the second pixel 202, similar to the first pixel 201, the first transistor Tr1 is turned on and the second transistor Tr2 is turned off at the same time. As a result, the cathode terminal K of the avalanche photodiode PD is electrically connected to the resistive element R. Therefore, in each pixel, the quench voltage Vq is increased to near the threshold voltage Vth due to the voltage drop. As a result, the swing amount Vm is reduced, and the dead time tdead can be reduced without reducing the excess voltage.

[0089] Therefore, in this embodiment as well, it is possible to reduce the dead time tdead without degrading the PDE characteristics. Furthermore, in this embodiment, similar to the sixth embodiment, both pixel regions for detecting high-intensity light and pixel regions for detecting low-intensity light are mixed within the pixel array 20. As a result, it is possible to reduce photon count loss even in lighting environments with large changes in background light.

[0090] (Tenth Embodiment) Figure 24 is a diagram showing the circuit configuration of the light detection device according to the tenth embodiment. Figure 25 is a cross-sectional view of the main part of the light detection device shown in Figure 24. Figure 26A is a cross-sectional view along the cutting line B-B shown in Figure 25. Figure 26B is a cross-sectional view along the cutting line C-C shown in Figure 25.

[0091] The light detection device 10 according to this embodiment further includes a third transistor Tr3 and a second resistor R2, in addition to the components of the light detection device 1 according to the first embodiment. The third transistor Tr3 is an n-channel conductive MOS transistor.

[0092] The gate of the third transistor Tr3 is connected to the second signal line SW2. The drain is connected to the input terminal of the inverter element INV. The source is connected to the cathode terminal K of the avalanche photodiode PD via the second resistor element R2. As shown in Figure 26A, the third transistor Tr3 is on the same layer as the first transistor Tr1 and the second transistor Tr2, and is positioned at the vertex of the triangle formed together with the first transistor Tr1 and the second transistor Tr2.

[0093] The second resistor R2 is connected in parallel with the first resistor R1. As shown in Figure 26B, the second resistor R2 is on the same layer as the first resistor R1 and is located directly below the third transistor Tr3. The resistance value of the second resistor R2 may be the same as or different from that of the first resistor R1. If the resistance values ​​of these two resistors are different, the resistance value of the second resistor R2 may be greater than or less than that of the first resistor R1.

[0094] In low-light lighting conditions, the control circuit 40 outputs a low-level first control signal to the gates of the first transistor Tr1 and the second transistor via the first signal line SW1, and at the same time outputs a low-level second control signal to the gate of the third transistor Tr3 via the second signal line SW2. In this case, the first transistor Tr1 and the third transistor Tr3 are turned off, and the second transistor Tr2 is turned on.

[0095] Under a medium-intensity lighting environment, the control circuit 40 outputs a high-level first control signal to the gates of the first transistor Tr1 and the second transistor via the first signal line SW1, and simultaneously outputs a high-level second control signal to the gate of the third transistor Tr3. In this case, the first transistor Tr1 and the third transistor Tr3 are turned on, and the second transistor Tr2 is turned off. At this time, the combined resistance value connected to the cathode terminal K becomes smaller than the resistance value of the first resistor R1.

[0096] Under high-light illumination conditions, the control circuit 40 outputs a high-level first control signal to the gates of the first transistor Tr1 and the second transistor via the first signal line SW1, while simultaneously outputting a low-level second control signal to the gate of the third transistor Tr3. In this case, the first transistor Tr1 is turned on, and the second transistor Tr2 and the third transistor Tr3 are turned off. At this time, the resistance value connected to the cathode terminal K is the resistance value of the first resistor R1. Therefore, similar to the first embodiment, the quench voltage Vq is boosted to near the threshold voltage Vth due to the voltage drop. As a result, the swing amount Vm is reduced, and the dead time tdead can be reduced without reducing the excess voltage.

[0097] Therefore, in this embodiment as well, it is possible to reduce the dead time tdead without degrading the PDE characteristics. Furthermore, in this embodiment, by connecting the second resistive element R2 in parallel with the first resistive element R1, the variation in the voltage drop amount due to the resistive elements increases. As a result, in the light detection device 10 according to this embodiment, it is possible to set the light detection conditions more optimally according to the light intensity of the lighting environment.

[0098] (Eleventh Embodiment) Figure 27 shows the circuit configuration of the photodetector according to the eleventh embodiment. The photodetector 1 according to this embodiment further includes a constant current source M in addition to the components of the photodetector 1 according to the first embodiment. The constant current source M is composed of, for example, a p-channel conductive MOS transistor. In this case, the power supply voltage VDD is applied to the drain. The source is connected to the drains of the first transistor Tr1 and the second transistor Tr2, respectively.

[0099] In the light detection device 11 according to this embodiment, configured as described above, similar to the first embodiment, one of the first transistor Tr1 and the second transistor Tr2 is turned on and the other is turned off simultaneously, depending on the light intensity of the lighting environment. Specifically, in a high-light-intensity lighting environment, the first transistor Tr1 is turned on and the second transistor Tr2 is turned off. At this time, the cathode terminal K is electrically connected to the resistive element R. As a result, the quench voltage Vq is increased to near the threshold voltage Vth due to the voltage drop across the resistive element R. As a result, the swing amount Vm is reduced, and the dead time tdead can be reduced without reducing the excess voltage.

[0100] Furthermore, in this embodiment, by adjusting the voltage supplied to the gate of the MOS transistor, which functions as a constant current source M, the recharge current used to raise the cathode voltage Vcathode of the avalanche photodiode PD, which has dropped to the quench voltage Vq, can be controlled.

[0101] <Examples of application to mobile devices> The technology disclosed herein (this technology) can be applied to various products. For example, the technology disclosed herein may be implemented as a device mounted on any type of mobile device such as automobiles, electric vehicles, hybrid electric vehicles, motorcycles, bicycles, personal mobility devices, airplanes, drones, ships, and robots.

[0102] Figure 28 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile control system to which the technology described herein may be applied.

[0103] The vehicle control system 12000 comprises a plurality of electronic control units connected via a communication network 12001. In the example shown in Figure 28, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an external information detection unit 12030, an internal information detection unit 12040, and an integrated control unit 12050. The functional configuration of the integrated control unit 12050 is shown in the figure, which includes a microcomputer 12051, an audio / image output unit 12052, and an in-vehicle network interface 12053.

[0104] The drivetrain control unit 12010 controls the operation of devices related to the vehicle's drivetrain according to various programs. For example, the drivetrain control unit 12010 functions as a control device for a drivetrain generating device that generates driving force for the vehicle, such as an internal combustion engine or a drive motor; a drivetrain transmission mechanism that transmits driving force to the wheels; a steering mechanism that adjusts the steering angle of the vehicle; and a braking device that generates braking force for the vehicle.

[0105] 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 system, or various lamps such as headlights, reverse lights, brake lights, turn signals, or fog lights. In this case, the body system control unit 12020 may receive radio waves transmitted from a portable device that replaces a key or signals from various switches. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock system, power window system, lamps, etc.

[0106] The external information detection unit 12030 detects information from outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the external information detection unit 12030. The external information detection unit 12030 causes the imaging unit 12031 to capture images of the outside of the vehicle and receives the captured images. Based on the received images, the external information detection unit 12030 may perform object detection processing such as detecting people, cars, obstacles, signs, or characters on the road surface, or distance detection processing.

[0107] The imaging unit 12031 is a light sensor that receives light and outputs an electrical signal corresponding 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.

[0108] The in-vehicle information detection unit 12040 detects information inside the vehicle. The in-vehicle information detection unit 12040 is connected to, for example, a driver status detection unit 12041 that detects the driver's state. The driver status detection unit 12041 includes, for example, a camera that captures images of the driver, and the in-vehicle information detection unit 12040 may calculate the driver's level of fatigue or concentration, or determine whether the driver is drowsy, based on the detection information input from the driver status detection unit 12041.

[0109] The microcomputer 12051 can calculate control target values ​​for the drive force generator, steering mechanism, or braking device based on information inside and outside the vehicle acquired by the external information detection unit 12030 or the internal information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing ADAS (Advanced Driver Assistance System) functions, including vehicle collision avoidance or impact mitigation, following driving based on distance between vehicles, maintaining vehicle speed, vehicle collision warning, or vehicle lane departure warning.

[0110] Furthermore, the microcomputer 12051 can perform cooperative control for purposes such as autonomous driving, where the vehicle drives autonomously without driver intervention, by controlling the drive force generating device, steering mechanism, or braking device, etc., based on information about the vehicle's surroundings acquired by the external information detection unit 12030 or the internal information detection unit 12040.

[0111] Furthermore, the microcomputer 12051 can output control commands to the body system control unit 12020 based on external information acquired by the external information detection unit 12030. For example, the microcomputer 12051 can control the headlights according to the position of a preceding or oncoming vehicle detected by the external information detection unit 12030, and perform coordinated control aimed at reducing glare, such as switching from high beams to low beams.

[0112] The audio-image output unit 12052 transmits at least one of audio and image output signals to an output device capable of visually or audibly notifying information to the vehicle's occupants or to those outside the vehicle. In the example shown in Figure 28, the output devices are exemplified as an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an onboard display and a head-up display.

[0113] Figure 29 shows an example of the installation position of the imaging unit 12031.

[0114] In Figure 29, the vehicle 12100 has imaging units 12101, 12102, 12103, 12104, and 12105 as the imaging unit 12031.

[0115] The imaging units 12101, 12102, 12103, 12104, and 12105 are installed, for example, on the front nose, side mirrors, rear bumper, back door, and the upper part of the windshield inside the vehicle 12100. The imaging unit 12101 installed on the front nose and the imaging unit 12105 installed on the upper part of the windshield inside the vehicle mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 installed on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 installed on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The forward images acquired by imaging units 12101 and 12105 are mainly used for detecting preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, or lanes.

[0116] Figure 29 shows an example of the imaging ranges of imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of imaging unit 12101 located on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of imaging units 12102 and 12103 located on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of imaging unit 12104 located on the rear bumper or back door. For example, by superimposing the image data captured by imaging units 12101 to 12104, an overhead view image of the vehicle 12100 can be obtained.

[0117] At least one of the imaging units 12101 to 12104 may have a function for acquiring distance information. For example, at least one of the imaging units 12101 to 12104 may be a stereo camera consisting of multiple image sensors, or an image sensor having pixels for phase difference detection.

[0118] For example, the microcomputer 12051, based on distance information obtained from the imaging units 12101 to 12104, can determine the distance to each object within the imaging range 12111 to 12114 and the temporal change of this distance (relative speed to the vehicle 12100). In particular, it can extract the closest object on the vehicle 12100's path that is traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or more) as the preceding vehicle. Furthermore, the microcomputer 12051 can set a predetermined distance to be maintained before the preceding vehicle and perform automatic braking control (including follow-and-stop control) and automatic acceleration control (including follow-and-start control), etc. In this way, cooperative control aimed at autonomous driving, etc., that drives autonomously without driver operation, can be performed.

[0119] For example, the microcomputer 12051 can use distance information obtained from imaging units 12101 to 12104 to classify and extract three-dimensional object data related to three-dimensional objects, such as motorcycles, passenger cars, large vehicles, pedestrians, utility poles, and other three-dimensional objects, and use this data for automatic obstacle avoidance. For example, the microcomputer 12051 identifies obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines the collision risk, which indicates the degree of risk of collision with each obstacle. If the collision risk is above a set value and there is a possibility of collision, the microcomputer 12051 can provide driving assistance to avoid collisions by outputting a warning to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or evasive steering via the drive system control unit 12010.

[0120] At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared light. For example, the microcomputer 12051 can recognize pedestrians by determining whether or not pedestrians are present in the images captured by the imaging units 12101 to 12104. Such pedestrian recognition is performed, for example, by a procedure to extract feature points from the images captured by the imaging units 12101 to 12104 as infrared cameras, and a procedure to perform pattern matching on a series of feature points that indicate the contour of an object to determine whether or not it is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the imaging units 12101 to 12104 and recognizes a 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 indicating a pedestrian at a desired position.

[0121] The above describes an example of a vehicle control system to which the technology of this disclosure may be applied. The technology of this disclosure can be applied to, for example, the imaging unit 12031 of the configuration described above. Specifically, one of the optical detection devices of the embodiments described above can be mounted on the imaging unit 12031. By applying the technology of this disclosure to the imaging unit 12031, the optical characteristics are improved. As a result, it becomes possible to improve the performance of the vehicle 12100.

[0122] The embodiments described above are merely examples of how to realize this technology, and there is a corresponding relationship between the matters in the embodiments and the inventive features in the claims. Similarly, there is a corresponding relationship between the inventive features in the claims and the matters in the embodiments of this technology that bear the same name. However, this technology is not limited to the embodiments and can be realized by making various modifications to the embodiments without departing from the gist of the technology.

[0123] Furthermore, this technology can take the following configuration.

[0124] (1) A light detection device comprising an avalanche photodiode, at least one resistive element, and a plurality of transistors for switching the electrical connection between the avalanche photodiode and the resistive element.

[0125] (2) The photodetector according to (1), wherein the at least one resistive element includes a first resistive element and a second resistive element having a different resistance value from the first resistive element, and the plurality of transistors include a first transistor connected to the avalanche photodiode via the first resistive element and a second transistor connected to the avalanche photodiode via the second resistive element.

[0126] (3) The photodetector according to (1), wherein the resistive element is a resistive wire, one end of the resistive wire is connected to the avalanche photodiode, and the plurality of transistors include a first transistor connected to the other end of the resistive wire and a second transistor connected in the middle of the resistive wire.

[0127] (4) The photodetector according to any one of (1) to (3), wherein the plurality of transistors includes a first MOS transistor and a second MOS transistor having the same conductivity type as the first MOS transistor, the gate of the first MOS transistor is connected to a first signal line, and the gate of the second MOS transistor is connected to a second signal line different from the first signal line.

[0128] (5) The photodetector according to any one of (1) to (3), wherein the plurality of transistors includes a first MOS transistor and a second MOS transistor having the opposite conductivity type to the first MOS transistor, and the gates of the first MOS transistor and the second MOS transistor are connected in common to a single signal line.

[0129] (6) The photodetector according to (1), further comprising a pixel array in which a plurality of pixels are arranged in a matrix, wherein the plurality of pixels include a first pixel having the avalanche photodiode, the at least one resistive element, and the plurality of transistors, and a second pixel having the same circuit configuration as the first pixel, wherein in the first pixel, the gates of the plurality of transistors are commonly connected to a first signal line, and in the second pixel, the gates of the plurality of transistors are commonly connected to a second signal line different from the first signal line.

[0130] (7) The light detection device according to (6), wherein in the pixel array, the first pixels are arranged in odd-numbered rows and the second pixels are arranged in even-numbered rows.

[0131] (8) The light detection device according to (6), wherein in the pixel array, the first pixels are arranged in odd rows and the second pixels are arranged in even rows.

[0132] (9) The light detection device according to (6), further comprising: an illuminometer for measuring the amount of light incident on the light detection device; and a control circuit for controlling the plurality of transistors based on the measured value of the illuminometer.

[0133] (10) The optical detection device according to (9), wherein the control circuit sets the level of a first control signal transmitted through the first signal line and the level of a second control signal transmitted through the second signal line based on the measured value.

[0134] (11) The photodetector according to any one of (1) to (10), further comprising a constant current source for controlling the recharge current of the avalanche photodiode.

[0135] (12) The photodetector according to (1), wherein the at least one resistive element includes a first resistive element and a second resistive element connected in parallel with the first resistive element, and the plurality of transistors include a first transistor connected to the avalanche photodiode via the first resistive element, a second transistor connected to the avalanche photodiode without going through the first resistive element or the second resistive element, and a third transistor connected to the avalanche photodiode via the second resistive element.

[0136] 1-11: Light detection device 20: Pixel array 30: Illuminance meter 40: Control circuit 200: Pixel 201: First pixel 202: Second pixel PD: Avalanche photodiode R: Resistor R1: First resistor R2: Second resistor SW1: First signal line SW2: Second signal line Tr1: First transistor Tr2: Second transistor Tr3: Third transistor

Claims

1. A photodetector comprising an avalanche photodiode, at least one resistive element, and a plurality of transistors for switching the electrical connection between the avalanche photodiode and the resistive element.

2. The photodetector according to claim 1, wherein the at least one resistive element includes a first resistive element and a second resistive element having a different resistance value from the first resistive element, and the plurality of transistors include a first transistor connected to the avalanche photodiode via the first resistive element and a second transistor connected to the avalanche photodiode via the second resistive element.

3. The photodetector according to claim 1, wherein the resistive element is a resistive wire, one end of the resistive wire is connected to the avalanche photodiode, and the plurality of transistors include a first transistor connected to the other end of the resistive wire and a second transistor connected in the middle of the resistive wire.

4. The photodetector according to claim 1, wherein the plurality of transistors include a first MOS transistor and a second MOS transistor having the same conductivity type as the first MOS transistor, the gate of the first MOS transistor being connected to a first signal line, and the gate of the second MOS transistor being connected to a second signal line different from the first signal line.

5. The photodetector according to claim 1, wherein the plurality of transistors include a first MOS transistor and a second MOS transistor having the opposite conductivity type to the first MOS transistor, and the gates of the first MOS transistor and the second MOS transistor are connected in common to a single signal line.

6. The photodetector according to claim 1, further comprising a pixel array in which a plurality of pixels are arranged in a matrix, wherein the plurality of pixels include a first pixel having the avalanche photodiode, the at least one resistive element, and the plurality of transistors, and a second pixel having the same circuit configuration as the first pixel, wherein in the first pixel, the gates of the plurality of transistors are commonly connected to a first signal line, and in the second pixel, the gates of the plurality of transistors are commonly connected to a second signal line different from the first signal line.

7. The photodetector according to claim 6, wherein in the pixel array, the first pixels are arranged in odd-numbered rows and the second pixels are arranged in even-numbered rows.

8. The photodetector according to claim 6, wherein in the pixel array, the first pixels are arranged in odd-numbered rows and the second pixels are arranged in even-numbered rows.

9. The light detection device according to claim 6, further comprising: an illuminance meter for measuring the amount of light incident on the light detection device; and a control circuit for controlling the plurality of transistors based on the measured value of the illuminance meter.

10. The optical detection device according to claim 9, wherein the control circuit sets the level of a first control signal transmitted through the first signal line and the level of a second control signal transmitted through the second signal line based on the measured value.

11. The photodetector according to claim 1, further comprising a constant current source for controlling the recharge current of the avalanche photodiode.

12. The photodetector according to claim 1, wherein the at least one resistive element includes a first resistive element and a second resistive element connected in parallel with the first resistive element, and the plurality of transistors include a first transistor connected to the avalanche photodiode via the first resistive element, a second transistor connected to the avalanche photodiode without going through the first resistive element or the second resistive element, and a third transistor connected to the avalanche photodiode via the second resistive element.

Images