JP2018174308A - Photodetector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To temperature-compensate the detection sensitivity of an SPAD in a photodetector using the SPAD.SOLUTION: A photodetector 1A includes a detection unit 10 that detects light by applying a reverse bias voltage to an SPAD 4, a monitor SPAD 12 that has the same characteristics as the SPAD constituting the detection unit, a current source 14 that supplies a constant current to the monitor SPAD and operates the SPAD in a Geiger mode, and a voltage generating unit 18 that generates a reverse bias voltage to be applied to the SPAD of the detecting unit on the basis of a reference breakdown voltage set from a breakdown voltage generated at both ends of the monitor SPAD and a predetermined excess voltage.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a photodetector using the avalanche effect.

  In Patent Document 1, in a photodetector using an avalanche photodiode (hereinafter referred to as APD), in order to perform temperature compensation of APD, the temperature characteristic of current amplification factor is substantially the same as that of APD, and the reference is reverse-biased. It is disclosed to use a joint structure.

  In this photodetector, a transistor having a current injection junction structure for injecting a reference current into the reference junction structure is used and applied to the APD and the reference junction structure so as to keep the amplification factor of the reference current at a predetermined value. By controlling the voltage, the multiplication factor of the APD is controlled.

Japanese Patent No. 5211095

  Since the APD is temperature-compensated by controlling the multiplication factor of the APD, the one disclosed in Patent Document 1 is effective in the linear mode in which a reverse bias voltage less than the breakdown voltage is applied to the APD to operate. .

However, the technique disclosed in the cited document 1 cannot be applied to a photodetector that operates the APD in the Kaiger mode.
That is, the APD operating in the Geiger mode is called SPAD, and the reverse bias voltage is set to a voltage value higher than the breakdown voltage. SPAD is an abbreviation for Single Photon Avalanche Diode.

  Since SPAD breaks down in response to the incidence of photons, the photodetector using SPAD is configured to output a pulse signal having a predetermined pulse width when SPAD is broken down.

  Therefore, the output of the photodetector using SPAD is “1” or “0”, and this type of photodetector has no concept of controlling the multiplication factor. For this reason, it is difficult to temperature compensate the detection sensitivity by SPAD using the technique disclosed in Patent Document 1.

  In one aspect of the present disclosure, in a photodetector using SPAD, it is desirable to be able to compensate for temperature of SPAD detection sensitivity, more specifically, SPAD photon detection sensitivity.

The photodetectors (1A to 1F) according to one aspect of the present disclosure include a detection unit (10), a monitoring SPAD (12), a current source (14), and a voltage generation unit (18).
The detection unit includes SPAD (2) and is configured to perform light detection by applying a reverse bias voltage to SPAD. The monitoring SPAD is a SPAD having the same characteristics as the SPAD constituting the detection unit.

  The current source operates the monitoring SPAD in the Geiger mode by supplying a constant current to the monitoring SPAD. When the monitor SPAD is operated in Geiger mode, a breakdown voltage is generated at both ends thereof. Therefore, the voltage generator detects based on a reference breakdown voltage set from the breakdown voltage and a predetermined excess voltage. A reverse bias voltage to be applied to the SPAD is generated.

  As a result, the reverse bias voltage generated based on the reference breakdown voltage estimated to be the breakdown voltage when the photon is incident and the breakdown occurs and the predetermined excess voltage is applied to the SPAD of the detection unit. Will be.

  Therefore, even if the breakdown voltage changes due to the temperature change of SPAD, the excess voltage becomes a substantially predetermined voltage, and the photon detection sensitivity by SPAD can be stabilized.

  That is, in a photodetector using SPAD, a reverse bias voltage exceeding the breakdown voltage is applied to SPAD, and a photon is incident on SPAD, and a detection signal is output based on the current that flows when SPAD is broken down. .

  On the other hand, the breakdown voltage of SPAD changes with temperature. Specifically, the breakdown voltage increases as the temperature increases. For this reason, if the reverse bias voltage applied to SPAD is made constant, the excess voltage obtained by subtracting the breakdown voltage from the reverse bias voltage becomes lower as the temperature is higher. And the detection sensitivity of SPAD changes with the voltage change of excess voltage.

  Therefore, in the photodetector of the present disclosure, the monitoring SPAD is used to estimate the breakdown voltage of the SPAD of the detection unit as the reference breakdown voltage, and based on the reference breakdown voltage and a desired excess voltage, The bias voltage is set.

  Therefore, according to the photodetector of the present disclosure, it is possible to compensate the temperature of the detection sensitivity of the SPAD constituting the detection unit, and perform light detection with a desired detection sensitivity without being affected by the temperature change of the SPAD. Will be able to.

  In addition, the code | symbol in the parenthesis described in this column and a claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is shown. It is not limited.

It is a block diagram showing the structure of the photodetector of 1st Embodiment. It is a block diagram showing the structure of the photodetector of 2nd Embodiment. It is a block diagram showing the structure of the photodetector of 3rd Embodiment. It is a block diagram showing the structure of the photodetector of 4th Embodiment. It is a block diagram showing the structure of the photodetector of 5th Embodiment. It is a block diagram showing the structure of the photodetector of 6th Embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, the photodetector 1A according to the first embodiment includes a detection unit 10 including a plurality of SPADs 2 and a monitoring SPAD 12 having the same configuration as the SPAD 2 in the detection unit 10 and having similar characteristics. .

  The SPAD 2 and the monitoring SPAD 12 are APDs that can operate in the Geiger mode as described above. In the detection unit 10, the quenching resistors 4 are connected in series to the anodes of the plurality of SPADs 2, respectively.

  The quenching resistor 4 stops the Geiger discharge of the SPAD2 by generating a voltage drop due to the current flowing through the SPAD2 when the photon is incident on the SPAD2 and the SPAD2 is broken down. The quenching resistor 4 may be configured by a “resistor” which is a so-called general passive element, or may be configured by an active element such as a “transistor”.

  In the detection unit 10, the voltage generated at both ends of the quenching resistor 4 when each SPAD 2 breaks down and a current flows through the quenching resistor 4 is input to the pulse conversion unit 6 corresponding to each SPAD 2. The

  The pulse converter 6 is for outputting a pulse signal having a predetermined pulse width as a detection signal when a photon enters the corresponding SPAD 2, and when the voltage across the quenching resistor 4 is equal to or higher than the predetermined voltage. A digital pulse that becomes “1” is generated.

By the way, in order to operate the detection unit 10, it is necessary to apply a reverse bias voltage V _SPAD larger than the breakdown voltage to each SPAD 2 in the direction opposite to the forward direction. If the reverse bias voltage V _SPAD is kept constant, the detection sensitivity of each SPAD 2 changes depending on the temperature.

Therefore, in this embodiment, with the monitoring SPAD12 placed under the same environment and the detection unit 10, the breakdown voltage of SPAD2, estimates as a reference breakdown voltage _{V BD.} Then, based on its reference breakdown voltage _{V BD} and a predetermined excess voltage _{V EX,} it generates a reverse bias voltage _{V SPAD,} is applied to the cathode of each SPAD2 detection unit 10.

Therefore, the photodetector 1A includes a current source 14 that supplies a constant current to the monitoring _{SPAD 12} , a voltage source 16 that generates an excess voltage V _EX , and a voltage generator 18 that generates a reverse bias voltage V _SPAD. Is provided.

The voltage generator 18 is configured to generate the reverse bias voltage V _SPAD by adding the breakdown voltage of the monitoring SPAD 12 as the reference breakdown voltage V _BD to the excess voltage V _EX from the voltage source 16.

The voltage generator 18 may generate the reverse bias voltage V _SPAD so that the excess voltage V _EX is substantially constant based on the reference breakdown voltage V _BD and the excess voltage V _EX. It is not necessary to configure to add as it is.

Next, the current source 14 receives the power supply voltage V _B sufficiently higher than the breakdown voltage of the monitoring _{SPAD 12,} and supplies the constant current I _SPAD to the monitoring _SPAD 12, thereby operating the monitoring _SPAD 12 in Geiger mode. It is something to be made.

Note that the monitoring SPAD 12 is not connected to a quenching resistor like the SPAD 2 in the detection unit 10 and is configured to keep current flowing once it has broken down.
For this reason, the reference breakdown voltage V _BD that changes according to the temperature of the monitoring SPAD 12 is always input to the voltage generator 18. Since the monitoring SPAD 12 has the same characteristics as the SPAD 2 constituting the detection unit 10, the reference breakdown voltage _VBD corresponds to the breakdown voltage of SPAD2.

Therefore, a voltage obtained by adding a predetermined excess voltage V _EX to a reference breakdown voltage V _BD corresponding to the breakdown voltage of each SPAD 2 is always applied to the cathode of each SPAD 2 in the detection unit 10 as a reverse bias voltage V _SPAD. Will be applied.

Therefore, in the photodetector 1A of the present embodiment, the detection sensitivity of each SPAD 2 in the detection unit 10 is a constant detection sensitivity corresponding to the excess voltage V _EX without being affected by the temperature change. Therefore, according to the present embodiment, the temperature of the detection sensitivity of each SPAD 2 constituting the detection unit 10 can be compensated for temperature, and the change in detection accuracy due to temperature can be suppressed.

  The monitoring SPAD 12 may be configured so that light is incident from the outside. However, as shown by a dotted line in FIG. 1, a light shielding film 13 that prevents light from entering the monitoring SPAD 12 is provided. It may be.

Even in this case, since the monitoring SPAD 12 is broken down by noise, the reference breakdown voltage V _BD can be input to the voltage generator 18. In this case, since the reference breakdown voltage _VBD does not change under the influence of light incident on the monitoring _{SPAD 12} , the voltage generator 18 can generate the reverse bias voltage V _SPAD more stably. it can.

Further, for example, the monitoring SPAD 12 may be arranged on the back side of the detection unit 10 so that the light incident on the monitoring SPAD 12 is less than the light incident on the detection unit 10. Even in this case, substantially the same effect as that obtained when the light shielding film 13 is provided on the monitoring SPAD 12 can be obtained.
[Second Embodiment]
As shown in FIG. 2, the basic configuration of the photodetector 1B of the second embodiment is the same as that of the photodetector 1A of the first embodiment. The difference from the first embodiment is that the switch 22 and the voltage storage unit are different. 24 is added.

Therefore, in the present embodiment, the same components as those in the first embodiment will be given the same reference numerals in the drawings, and detailed description thereof will be omitted, and differences from the first embodiment will be described.
As shown in FIG. 2, the switch 22 is provided in the energization path from the current source 14 to the monitoring SPAD 12, and conducts the energization path in accordance with the distance measurement operation signal from the distance measuring device 20 using the photodetector 1 </ b> B. It is for blocking.

  The switch 22 is turned off when the distance measuring device 20 is performing distance measurement based on the detection signal from the detection unit 10, and is turned on when the distance measuring device 20 is stopping distance measurement. It becomes.

Therefore, when the distance measuring device 20 stops the distance measurement, the monitoring SPAD 12 is supplied with a current from the current source 14 and breaks down.
For this reason, the voltage storage unit 24 uses the breakdown voltage of the monitoring SPAD 12 as the reference breakdown voltage V _BD when the distance measurement device 20 stops distance measurement according to the distance measurement operation signal from the distance measurement device 20. Is set and stored as

Then, when the distance measuring device 20 starts the distance measurement, the voltage storage unit 24 outputs the stored reference breakdown voltage _VBD to the voltage generation unit 18 so that the voltage generation unit 18 receives the latest reference breakdown voltage _VBD. A reverse bias voltage V _SPAD corresponding to _BD is generated.

The reference breakdown voltage V _BD is stored by the voltage storage unit 24 by, for example, latching the reference breakdown voltage V _BD in a storage element by charging a capacitor or the like, or digitizing the reference breakdown voltage V _BD. Is stored in the memory.

  Thus, according to the photodetector 1B of the present embodiment, the monitoring SPAD 12 is operated when the distance measuring device 20 as an external device stops the distance measurement. For this reason, when the detection unit 10 is used for the distance measuring operation, the operation of the monitoring SPAD 12 can be stopped, and an increase in the power consumption of the photodetector 1B due to the current flowing through the monitoring SPAD 12 can be suppressed. .

  The distance measuring device 20 is mounted on a vehicle, for example, for irradiating distance measuring light forward in the traveling direction, and for measuring the distance from the reflected light to an obstacle existing in front of the vehicle. Yes, the detection unit of this embodiment is used to receive reflected light.

In the present embodiment, the operation of the switch 22 and the voltage storage unit 24 is switched according to the operation signal from the distance measuring device 20, but the operation of the switch 22 and the voltage storage unit 24 is switched by the distance. It is not limited to the measuring device 20. That is, the switch 22 and the voltage storage unit 24 may operate in response to a command from an external device that uses the detection signal from the detection unit 10.
[Third Embodiment]
As shown in FIG. 3, the basic configuration of the photodetector 1C of the third embodiment is the same as that of the photodetector 1A of the first embodiment. The difference from the first embodiment is that a plurality of monitoring SPAD12- , 12-n, and a reference breakdown voltage _VBD calculation / selection unit 30. ?
Therefore, in the present embodiment, the same components as those in the first embodiment will be given the same reference numerals in the drawings, and detailed description thereof will be omitted, and differences from the first embodiment will be described.

As shown in FIG. 3, the current source 14 has a current I _SPAD to be supplied to one monitoring SPAD in order to operate the plurality of monitoring SPADs 12-1, 12-2,..., 12-n in the Geiger mode. Is configured to supply a current that is n times the current. The supplied current is distributed to a plurality of monitoring SPADs 12-1, 12-2, ..., 12-n, and each of the monitoring SPADs 12-1, 12-2, ..., 12-n operates in Geiger mode. .

The breakdown voltages V _BD1 , V _BD2 ,..., V _BDn of the monitor SPADs 12-1, 12-2,..., 12-n are input to the calculation / selection unit 30. This is used to generate a reference breakdown voltage _VBD input to the voltage generator 18.

Then, the calculation / selection unit 30 selects a preset minimum value, maximum value, or median value from the plurality of breakdown voltages V _BD1 , V _{BD2 ,.} By calculating, the reference breakdown voltage _VBD input to the voltage generator 18 is generated.

This is because even if the monitoring SPAD 12 is configured to have the same characteristics as the SPAD 2, the variation in characteristics cannot be eliminated. If the variation in the characteristics of the monitoring SPAD 12 is large, an appropriate reference breakdown voltage V _BD is obtained. This is because the voltage cannot be input to the voltage generator 18.

In other words, in this embodiment, the reference breakdown voltage _VBD input to the voltage generation unit 18 is generated using a plurality of monitoring SPADs 12, so that even if the monitoring SPADs 12 have large variations, the reference breakdown voltage _VBD is appropriate. A reference breakdown voltage _VBD can be generated.

For this reason, according to the present embodiment, the voltage generation unit 18 can generate a more appropriate reverse bias voltage V _SPAD , and the temperature sensitivity of the detection sensitivity of the _{SPAD 2} in the detection unit 10 can be better compensated. be able to.

The calculation / selection unit 30 is for generating a more appropriate reference breakdown voltage V _BD using a plurality of breakdown voltages V _BD1 , V _BD2 ,..., V _BDn. Is preferable to select a median value from a plurality.
[Fourth Embodiment]
As shown in FIG. 4, the basic configuration of the photodetector 1D of the fourth embodiment is the same as that of the photodetector 1A of the first embodiment. The difference from the first embodiment is the voltage generator 18. The voltage control unit 40 is provided for setting an excess voltage V _EX to be added to the reference breakdown voltage V _BD .

Therefore, in the present embodiment, the same components as those in the first embodiment will be given the same reference numerals in the drawings, and detailed description thereof will be omitted, and differences from the first embodiment will be described.
As shown in FIG. 3, the voltage control unit 40 takes in the reference breakdown voltage V _BD is input to the voltage generator 18, based on the reference breakdown voltage V _BD, configured to set the excess voltage V _EX Has been.

This is SPAD2 from changing characteristics depending on the temperature, to control the detection sensitivity to a desired detection sensitivity is to be considered that it is better to also excess voltage V _EX adjusted depending on the temperature.

That is, in the present embodiment, the reference breakdown voltage _{V BD,} utilized as a detection signal of the temperature of the SPAD2, according to excess voltage _{V EX} used to generate the reverse bias voltage _{V SPAD} by the voltage generator 18 to a temperature Is set.

  As a result, also in the photodetector 1D of the present embodiment, as in the photodetectors 1A to 1C of each of the above embodiments, the detection sensitivity of each SPAD 2 constituting the detection unit 10 can be temperature-compensated and detected by temperature. The change in accuracy can be suppressed.

The voltage control unit 40 is, for example, by the reference breakdown voltage V _BD pressure resistance component, the excess voltage V _EX, is changed in proportion to the reference breakdown voltage V _BD, constituting at resistor divider It is possible.
[Fifth Embodiment]
As shown in FIG. 5, the basic configuration of the photodetector 1E of the fifth embodiment is the same as that of the photodetector 1A of the first embodiment. The difference from the first embodiment is the configuration of the detection unit 10. The output determination unit 50 and the threshold control unit 52 are provided.

Therefore, in the present embodiment, the same components as those in the first embodiment will be given the same reference numerals in the drawings, and detailed description thereof will be omitted, and differences from the first embodiment will be described.
The detection unit 10 is configured as a so-called light receiving array by arranging a plurality of SPADs 2 in a lattice pattern.

  As shown in FIG. 1, the quenching resistor 4 and the pulse conversion unit 6 are connected to the plurality of SPADs 2 provided in the detection unit 10, and a breakdown occurs when photons enter each SPAD2. When this occurs, a digital pulse is output from the pulse converter 6 as a detection signal.

  The output determination unit 50 counts the number of detection signals output from the plurality of SPADs 2 constituting the detection unit 10 via the pulse conversion unit 6, and detects when the count value is equal to or greater than a predetermined threshold value. It is determined that light is detected by the unit 10.

  This is because SPAD 2 may break down due to noise and output a detection signal via the pulse converter 6. That is, when the output determination unit 50 uses the detection unit 10 as one pixel for light detection, and the number of SPAD2s that output detection signals among the plurality of SPAD2s constituting the detection unit 10 is equal to or greater than a threshold value. The detection unit 10 determines that light is detected.

And if the output determination part 50 judges that the light was detected in the detection part 10, it will output the trigger signal showing that.
On the other hand, the threshold control unit 52 sets the threshold used by the output determination unit 50 based on the breakdown voltage of the monitoring SPAD 12.

In this embodiment, the predetermined breakdown voltage V _EX is added to the reference breakdown voltage V _BD to generate the reverse bias voltage V _SPAD to be applied to each _{SPAD 2} of the detection unit 10, and thus the operation of each _{SPAD 2} This is because the voltage changes.

That is, when the reverse bias voltage V _SPAD is set by adding a predetermined excess voltage V _EX to the reference breakdown voltage V _BD , the detection sensitivity of each _{SPAD 2} can be suppressed from decreasing with temperature, but applied to the SPAD 2. The reverse bias voltage V _SPAD changes. When the reverse bias voltage V _SPAD increases, the dark current flowing through the _{SPAD 2} increases, and the _{SPAD 2} is easily broken down by this dark current.

Therefore, in the present embodiment, even if SPAD2 is likely to malfunction due to dark current, a threshold is set according to the reference breakdown voltage _VBD in order to suppress a decrease in light detection accuracy by the detection unit 10. It is.

Note that when the reference breakdown voltage V _BD increases as the temperature rises, the reverse bias voltage V _SPAD also rises and SPAD2 is likely to malfunction, so that the threshold control unit 52 increases the reference breakdown voltage V _BD . What is necessary is just to comprise so that a threshold value may be increased.
[Sixth Embodiment]
In the photodetectors 1A to 1E of the first to fifth embodiments, the detection unit 10 includes a quenching resistor 4 connected to the anode of each SPAD 2 and a connection point between the anode of each SPAD 2 and the quenching resistor 4. The detection signal is output via the pulse converter 6.

Therefore, the voltage generator 18, by adding a reference breakdown voltage _{V BD} and a predetermined excess voltage _{V EX,} generates a reverse bias voltage _{V SPAD} to a higher potential than the anode of each SPAD2, each SPAD2 Configured to be applied to the cathode. For example, since the anode of SPAD2 does not become a negative potential, the reverse bias voltage V _SPAD is preferably a positive potential.

  On the other hand, in the photodetector 1F of the present embodiment, as shown in FIG. 6, the detection unit 10 has a quenching resistor 4 connected to the cathode of each SPAD2, and the detection signal is sent to the cathode of each SPAD2. The signal is output from the connection point with the quenching resistor 4 via the pulse converter 6.

Therefore, the detection unit 10, the power supply voltage _{V B} to the cathode of SPAD2 through the quenching resistor 4 are applied, in order to operate the SPAD2 in Geiger mode, the potential of the anode of the SPAD2, than the cathode It is necessary to lower the reverse bias voltage.

Therefore, in this embodiment, similarly to SPAD2 detection unit 10, the cathode of the monitoring SPAD12 power supply voltage _{V B} are applied, the current source 14 is connected to the anode of the monitor SPAD12, from anode to ground The current is made to flow.

Then, the voltage generation unit 18 takes in a negative reference breakdown voltage −V _BD lower than the power supply voltage V _B from the anode of the monitoring SPAD 12, and adds a negative excess voltage obtained from the negative side of the voltage source 16 to the negative reference breakdown voltage −V _BD. It is configured to add the -V _EX.

As a result, the voltage generator 18 adds the negative reference breakdown voltage −V _BD and the negative excess voltage −V _EX so that the reverse bias voltage −V _SPAD that has a lower potential than the cathode of the _{SPAD 2} is obtained. Generated. Then, the generated reverse bias voltage −V _SPAD is applied to the anode of each _{SPAD 2} in the detection unit 10. For example, since the cathode of SPAD2 does not have a negative potential, the reverse bias voltage -V _SPAD is preferably a negative potential.

Therefore, also in this embodiment, a reverse bias voltage V _SPAD obtained by adding the excess voltage V _EX to the reference breakdown voltage V _BD is applied between the cathode and anode of each SPAD 2 in the detection unit 10. The same effect as the above embodiment can be obtained.

As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the above-mentioned embodiment, It can implement in various deformation | transformation.
For example, in the first embodiment, it has been described that the monitor SPAD 12 may be provided with the light-shielding film 13 that prevents light from entering, but the monitor SPAD 12 is also provided in the second to fifth embodiments. A light shielding film 13 may be provided to shield the light. Further, when the monitor SPAD 12 is shielded from light, it is not always necessary to provide the light shielding film 13 as long as it can prevent light from entering the monitor SPAD 12.

  Further, in each of the above embodiments, the detection unit 10 has been described as being provided with a plurality of SPADs 2, but even when the detection unit 10 is provided with one SPAD 2, the configuration as in each of the above embodiments. If it does, it can suppress that the detection sensitivity by the detection part 10 falls.

  In addition, a plurality of functions of one constituent element in the above embodiment may be realized by a plurality of constituent elements, or a single function of one constituent element may be realized by a plurality of constituent elements. Further, a plurality of functions possessed by a plurality of constituent elements may be realized by one constituent element, or one function realized by a plurality of constituent elements may be realized by one constituent element. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claim are embodiment of this invention.

  DESCRIPTION OF SYMBOLS 1A-1F ... Photodetector, 2 ... SPAD, 10 ... Detection part, 12 ... SPAD for monitoring, 14 ... Current source, 18 ... Voltage generation part.

Claims (11)

A detection unit (10) including a SPAD (2) that is an avalanche photodiode operable in a Geiger mode, and configured to perform light detection by applying a reverse bias voltage in a direction opposite to the forward direction to the SPAD. When,
A monitoring SPAD (12) having the same characteristics as the SPAD constituting the detector;
A current source (14) for supplying a constant current to the monitoring SPAD and operating in Geiger mode;
A voltage generator (18) that generates a reverse bias voltage to be applied to the SPAD of the detector based on a reference breakdown voltage set from a breakdown voltage generated at both ends of the monitoring SPAD and a predetermined excess voltage. )When,
A photodetector.   The photodetector according to claim 1, wherein the voltage generation unit is configured to generate the reverse bias voltage by adding the reference breakdown voltage and the excess voltage. In the detection section, a quenching element (4) for stopping the SPAD from breaking down and Geiger discharge by the incidence of photons is connected to the cathode of the SPAD.
The photodetector according to claim 1, wherein the voltage generation unit is configured to apply a reverse bias voltage having a lower potential than the cathode to the anode of the SPAD. In the detection unit, a quenching element is connected to the anode of the SPAD to stop the SPAD from breaking down due to the incidence of photons to stop Geiger discharge,
The photodetector according to claim 1, wherein the voltage generation unit is configured to apply a reverse bias voltage having a higher potential than the anode to the cathode of the SPAD.   The photodetector according to claim 1, wherein the monitor SPAD is configured to be shielded from light and to be broken down by noise.   5. The photodetector according to claim 1, wherein the monitor SPAD is configured such that incident light is smaller than light incident on a detection unit. A switch (22) for conducting an energization path from the current source to the monitoring SPAD in accordance with an external command;
When the switch is energizing the energization path, the reference breakdown voltage is set and stored from the breakdown voltage of the monitoring SPAD, and the voltage generation unit does not depend on the state of the energization path. A voltage storage unit (24) for outputting a reference breakdown voltage;
The photodetector of any one of Claims 1-6 provided with these. A voltage controller (40) for setting the excess voltage used by the voltage generator to generate the breakdown voltage based on the reference breakdown voltage of the monitoring SPAD;
The photodetector of any one of Claims 1-7 provided with these. Calculation / selection that includes a plurality of the monitoring SPADs, sets or sets the reference breakdown voltage and supplies the voltage generation unit by calculating or selecting using a plurality of breakdown voltages obtained from the plurality of monitoring SPADs Part (30),
The photodetector of any one of Claims 1-8 provided with these. The detection unit includes a plurality of SPADs,
An output that counts the number of detection signals output from a plurality of SPADs of the detection unit, and outputs a trigger signal by determining that light is detected by the detection unit when the count value is equal to or greater than a predetermined threshold value A determination unit (50);
The photodetector of any one of Claims 1-9 provided with these. A threshold control unit (52) for setting the threshold based on the reference breakdown voltage;
The photodetector according to claim 10, comprising:

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