JPH10115550A - Optical detector and solid-state image sensing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical detector by which light is detected while a good SN ratio is ensured even when the greater part of the output current of a light-receiving element is occupied by a dark-current component. SOLUTION: The incident or nonincident state of light, to be measured, on a photoelectric conversion element 100 is generated periodically by a light shutoff control part 200 provided with an optical chopper 210 or the like. First, the mean value of dark currents generated by the photoelectric conversion element in the nonincident state is removed by a dark-current removal circuit 400, and the ratio of a dark-current component to a signal-current component is improved. In addition, an estimated residual-dark-current component in which a residual-dark-current component is found in an adjacent point of time in terms of time is subtracted by a difference computing circuit 500, and a signal component is extracted. Therefore, while a good SN ratio is ensured, the signal component is extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photodetector for measuring the intensity of light to be measured.

[0002]

2. Description of the Related Art For measuring the intensity of light to be measured, a semiconductor light receiving element such as a photodiode which generates a charge corresponding to the amount of received light of the light to be measured and outputs it as a current signal is frequently used. In measuring the amount of received light with high accuracy using such a light receiving element, the dark current of the light receiving element always poses a problem, and a method of reducing or removing the dark current according to the type of the light receiving element has been proposed.

[0003] As a proposed method, the dark current is
There is a method of cooling the light receiving element by paying attention to the fact that it is reduced when the operating temperature of the light receiving element is lowered (hereinafter referred to as conventional method 1). Also, using an optical chopper, the output current from the light receiving element in a state where the light to be measured is cut off is evaluated as a dark current, and the evaluation dark current is subtracted from the output current of the light receiving element in a transmission state of the light to be measured, There is a method of obtaining a current signal corresponding to the intensity of the light to be measured (hereinafter, referred to as Conventional Method 2).

An apparatus combining the conventional method 1 and the conventional method 2 (hereinafter referred to as a conventional example) is disclosed in Japanese Patent Laid-Open No. 61-2550.
No. 60 is disclosed.

[0005]

In the conventional photodetector, the dark current component is reduced by the above-described method, and therefore, has the following problems.

In the first conventional method, it is necessary to provide a cooling unit for cooling the light receiving element, so that the photodetector becomes large-scale. Furthermore, when the dark current is reduced by cooling, it often occurs that a sufficient SN ratio cannot be secured when the light to be measured is weak.

In the conventional method 2, a certain SN ratio can be secured when the amount of current generated by the reception of the light to be measured (hereinafter also referred to as a signal current amount) and the amount of dark current are substantially the same. The signal current amount is overwhelmingly smaller than the dark current amount,
For example, in the case of an InGaAs photodiode, it is impossible to secure a good SN ratio.

Accordingly, even in the conventional apparatus employing both the conventional method 1 and the conventional method 2, if the dark current component occupies most of the current signal from the light receiving element after cooling, the accuracy is low. Good measurement was difficult.

The present invention has been made in view of the above, and provides a photodetector capable of securing a good SN ratio even when a dark current component occupies most of the output current of a light receiving element. The purpose is to do.

Also, the present invention provides a solid-state imaging device capable of securing an excellent S / N ratio and capturing an incident light image even when a dark current component occupies most of the output current of a light receiving element corresponding to a pixel. It is intended to provide a device.

[0011]

According to a first aspect of the present invention, there is provided a photodetecting device comprising: (a) a light blocking control section for periodically controlling transmission and blocking of light to be measured; A photoelectric conversion element that generates a corresponding charge and outputs the signal as a current signal;
(C) receiving a current signal output from the photoelectric conversion element,
A first terminal connected between the input and output terminals according to the integration instruction signal.
And (d) receiving a dark current signal output from the photoelectric conversion element when the light to be measured is cut off, obtaining a substantially average value of the dark current, and responding to the dark current removal instruction signal. A dark current removing circuit that removes a substantially average value of a dark current from a current signal input to the integrating circuit; and (e) an output signal from the integrating circuit is input, and according to a subtraction instruction signal,
A first value of the output signal of the integration circuit after the integration of the dark current signal from which the approximately average value of the dark current has been removed for a predetermined time when the light to be measured is cut off, The second value and the first value of the output signal of the integration circuit after the integration circuit integrates the current signal from the photoelectric conversion element from which the approximately average value of the dark current has been removed for a predetermined time during transmission And (f) a light transmission state display signal output from the light blocking control unit, and an integration instruction signal in synchronization with a change in the light transmission state display signal. And a timing generation circuit for outputting a dark current removal instruction signal and a subtraction instruction signal.

In the light detecting device according to the first aspect, a light blocking control unit such as a light chopper operates to alternately and periodically generate a light blocking state and a light transmitting state. Then, the light-blocking control unit outputs a light-transmitting-state indication signal that becomes insignificant in the light-blocking state and significant in the light-transmitting state to the timing generation circuit.

When the light transmission state indicating signal changes from significant to insignificant, the timing generation circuit sets the integration instruction signal to insignificant, operates the integration circuit in the non-integration mode, and
The dark current removal instruction signal is made insignificant, and the dark current signal output from the photoelectric conversion element is input to the dark current removal circuit. The dark current elimination circuit obtains a substantially average value of the dark current signal until the dark current elimination instruction signal becomes significant based on the input dark current signal and the output signal from the integration circuit during the non-integration operation.

Next, the dark current removal instruction signal is made significant,
From the current signal flowing into the current signal input terminal of the integrating circuit, the dark current removing circuit continuously removes the approximate average value of the obtained dark current.

In this state, the integration instruction signal is made significant, and
A current signal obtained by removing a substantially average value of a dark current from the current signal output from the photoelectric conversion element is input to an integration circuit for a predetermined time, integrated, and charge is accumulated in the first capacitor. After a lapse of a predetermined time, the subtraction instruction signal is temporarily made significant, and the integration result of the integration circuit at that time is held in the difference calculation circuit.

Thereafter, when the light transmission state display signal changes from insignificant to significant, the electric charge stored in the first capacitance element is reset, and the light detection instruction signal is made significant.
The current signal output terminal of the photoelectric conversion element is connected to the current input terminal of the integration circuit. Then, the current signal obtained by removing the substantially average value of the dark current from the current signal output from the photoelectric conversion element is input to the integration circuit for a predetermined time and integrated, and the electric charge is accumulated in the first capacitor. After a lapse of a predetermined time, the subtraction instruction signal is temporarily made significant, and the integration result of the integration circuit at that time is notified to the difference calculation circuit.

Upon receiving the notification, the difference calculation circuit calculates the integration result corresponding to only the previously held dark current component and the integration result corresponding to the sum of the signal component and the dark current component notified this time. Is calculated and output.

Thus, in the photodetector according to the first aspect, even if most of the output current signal from the photoelectric conversion element is a dark current component, first, most of the dark current component is detected at a point in time that is close in time. After removing the approximate average value of the obtained dark current, the ratio between the dark current component and the signal current component is improved, and the remaining residual dark current component is further estimated at a time closer in time. By subtracting the dark current component,
Since the signal component is extracted, a good SN ratio is secured and the signal component is extracted. By measuring the signal components extracted in this way, the received light intensity of the light to be measured is accurately measured.

According to a second aspect of the present invention, there is provided the photodetector according to the first aspect, wherein (i) the photoelectric conversion element is a photodiode having a cathode terminal set to a reference potential;
i) The integration circuit includes an operational amplifier having a negative input terminal for inputting a current signal output from the photoelectric conversion element and a positive input terminal set to a reference potential.

The dark current generated by the photodiode, which is a photoelectric conversion element, increases as the bias voltage applied between the cathode terminal and the anode terminal increases.

According to a second aspect of the present invention, a cathode terminal of a photodiode serving as a photoelectric conversion element is set to a reference potential, and an anode terminal serving as a current signal output terminal is integrated with the reference potential in an imaginary short state. Since it is connected to the negative input terminal of the operational amplifier of the circuit, the bias voltage applied between the cathode terminal and the anode terminal can be reduced to the limit. Therefore, the absolute amount of the generated dark current is reduced. As a result, the SN ratio of the extracted signal component is improved.

According to a third aspect of the present invention, in the photodetector of the first aspect, the dark current elimination circuit includes: (i) a source terminal connected to a current signal input terminal of the integration circuit; And (ii) a second capacitance element having a gate terminal connected to the first terminal and a second terminal set to the reference potential, (Iii) a switching element that has a gate terminal of the field effect transistor connected to the first terminal, a second terminal connected to the output terminal of the integration circuit, and that opens and closes in response to a dark current removal instruction signal. It is characterized by.

According to a third aspect of the present invention, a dark current signal from the photoelectric conversion element in a light-blocking state is input to the source terminal of the field-effect transistor and a dark current removal instruction signal is obtained based on the approximate average value of the dark current. The signal output from the integrating circuit during the non-integrating operation is connected to the gate terminal of the field effect transistor and the second
To the first terminal of the capacitive element. As a result, the potential of the amount corresponding to the substantially average value of the dark current signal from the photoelectric conversion element during the period in which the dark current removal instruction signal is insignificant is applied to the first terminal of the second capacitor, that is, the electric field effect. A current generated at the gate terminal of the transistor and corresponding to this potential is removed from the current signal flowing into the current signal input terminal of the integrating circuit via the field effect transistor.

If the dark current removal instruction signal is significant, a potential value corresponding to a substantially average value of the dark current signal from the photoelectric conversion element before that is held at the first terminal of the second capacitor. . Therefore, when the dark current elimination instruction signal is significant, the substantially average value of the dark current when the previous dark current elimination instruction signal is insignificant is the current signal that continuously flows into the current signal input terminal of the integration circuit. Removed from

According to a fourth aspect of the present invention, the light to be measured is infrared light and the photoelectric conversion element is a photodiode made of InGaAs.

The photoelectric conversion element has an infrared sensitivity.
In a photodiode made of GaAs, most of the output current signal is a dark current component. Therefore, it is particularly preferable to adopt the configuration of the photodetector of the first aspect.

According to a fifth aspect of the present invention, there is provided a solid-state imaging device, wherein the photodetectors of the first aspect are arranged one-dimensionally or two-dimensionally.

According to a fifth aspect of the present invention, there is provided a solid-state imaging device, wherein a photodetector corresponding to pixels arranged one-dimensionally or two-dimensionally is provided.
, And a good S value is obtained for each pixel.
A suitable input image is captured with the N ratio secured.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a photodetector and a solid-state imaging device according to the present invention will be described below with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a configuration diagram of an embodiment of the photodetector of the present invention. As shown in FIG. 1, the light detection device (a) periodically enters through the light cutoff control unit 200 and (b) the light cutoff control unit 200 that controls transmission and cutoff of the light to be measured. (C) a signal output from the photoelectric conversion element 100 is input according to the integration instruction signal SM, and the photoelectric conversion element 100 is a photodiode that generates a charge corresponding to the intensity of the light to be measured and outputs the charge as a current signal. An integration circuit 300 for integrating the capacitance into the capacitance element 310 connected between the input and output terminals and discharging the electric charge accumulated in the capacitance element 310 in response to the reset instruction signal R1; The dark current signal output from the photoelectric conversion element 100 is input, a substantially average value of the dark current is obtained, and the integration circuit 300 is provided in accordance with the dark current removal instruction signal RM.
And (e) an output signal from the integration circuit 300 is input, and the light to be measured is cut off in response to the subtraction instruction signal SB. Holds the value V1 of the output signal of the integration circuit 300 after the integration circuit 300 integrates the dark current signal from which the substantially average value of the dark current has been removed for a predetermined time T at
The value V2 and the value of the output signal of the integration circuit 300 after the integration circuit 300 integrates the current signal from the photoelectric conversion element 100 from which the substantially average value of the dark current has been removed over a predetermined time T in the transmission state of the light to be measured. A difference calculation circuit 500 that outputs a signal corresponding to the difference from V1 and resets a held value in response to a reset instruction signal R2; and (f) a light transmission state display signal TR output from the light cutoff control unit 200.
And a timing generation circuit 600 that outputs an integration instruction signal SM, a reset instruction signal R1, a dark current removal instruction signal RM, a subtraction instruction signal SB, and a reset instruction signal R2 in synchronization with the light transmission state display signal TR. And

In the case of infrared measurement, a photodiode made of InGaAs can be suitably used as the photoelectric conversion element 100. In the following description, it is assumed that the dark current component occupies most of the current signal output from the photoelectric conversion element 100.

As shown in FIG. 1, the cathode terminal of the photoelectric conversion element 100 is grounded, and the photoelectric conversion element 100 outputs a current signal from the anode terminal.

The cathode terminal of the photoelectric conversion element 100 is grounded, and the anode terminal, which is a current signal output terminal, is connected to the ground level and the negative input terminal 321 of the operational amplifier 320 of the integration circuit 300 in an imaginary short state. Therefore, the bias voltage applied between the cathode terminal and the anode terminal can be reduced to the limit. Therefore, the absolute amount of the generated dark current is reduced.

The light cutoff control unit 200 controls the light to be measured in a cutoff state by (i) an optical chopper 210 disposed in an optical path of the light to be measured to the photoelectric conversion element 100 and (ii) an optical chopper 210. A photo-interrupter 220 that detects which state of the transmission state it is in and outputs a light transmission state display signal TR that is significant in the case of the transmission state.

The integrating circuit 300 includes (i) the photoelectric conversion element 1
00, an operational amplifier 320 having a negative input terminal 321 and a positive input terminal 322 grounded, and (ii) a negative input terminal 3 of the operational amplifier 320.
(Ii) a capacitor 310 having the first terminal connected to the first terminal;
i) a switch element 330 having a second terminal connected to the first terminal of the capacitive element 310, a second terminal connected to the output terminal 323 of the operational amplifier 320, and opening / closing in response to the integration instruction signal SM; (Iv) a switch element having a negative input terminal 321 of the operational amplifier 320 connected to the first terminal, a second terminal connected to the output terminal 323 of the operational amplifier 320, and opening and closing in response to the reset instruction signal R1. 340.

The dark current elimination circuit 400 includes (i) a field effect transistor 410 having a source terminal connected to the current signal input terminal of the integration circuit 300 and a drain terminal grounded, and (ii) a field effect transistor 410. The gate terminal of the capacitor 420 is connected to the first terminal, the second terminal is grounded, the capacitor 420 is connected to the first terminal, and (iii) the gate terminal of the field effect transistor 410 is connected to the first terminal. Is connected to the output terminal of the integration circuit 300, and includes a switch element 430 that opens and closes in response to the dark current removal instruction signal RM.

The difference calculation circuit 500 includes (i) the integration circuit 3
A switch element 510 that inputs the signal output from the first terminal 00 to the first terminal and opens and closes in response to the subtraction instruction signal SB;
(Ii) a capacitive element 520 for inputting a signal output from the second terminal of the switch element 510 to the first terminal;
i) the current signal output from the second terminal of the capacitive element 520 is input from the negative input terminal 531 and the positive input terminal 532 is grounded; and (iv) the negative input terminal 531 of the operational amplifier 530. And the first terminal are connected, and the second terminal is connected to the output terminal 533 of the operational amplifier 530. (v) The negative input terminal 531 of the operational amplifier 530 is connected to the first terminal. And a switch element 550 having a second terminal connected to the output terminal 533 of the operational amplifier 530 and opening and closing in response to the reset instruction signal R2.

The photodetector of this embodiment measures the amount of received light of the light to be measured as follows. FIG. 2 is a timing chart showing the operation of the photodetector of the present embodiment. In FIG. 2, the light transmission state display signal TR, the integration instruction signal SM, the reset instruction signal R1, the subtraction instruction signal SB, and the reset instruction signal R2 are significant at a high level. Each signal except for closing the switch element that controls the opening and closing, and at the low level is insignificant, and each signal except the light transmission state display signal TR opens the switching element that controls the opening and closing. On the other hand, the dark current elimination signal RM is insignificant at a high level, and the switch element 430 is closed, and is significant at a low level, and the switch element 430 is opened.

In the photodetector of this embodiment, the light chopper 210 of the light blocking controller 200 causes the photoelectric conversion element 100 to periodically generate the light blocking state and the light transmitting state of the light to be measured. Then, the alternating and periodic change of the light blocking state and the light transmitting state is detected by the photo interrupter 220, and is notified to the timing generation circuit 600 as the light transmitting state display signal TR.

When the light transmission state display signal TR changes from significant to insignificant, that is, when the non-incident state of the light to be measured for the photoelectric conversion element 100 starts, the timing generation circuit 600 generates the dark current removal instruction signal RM. As insignificant, switch element 430 is opened.

When a dark current is generated in the photoelectric conversion element 100 in this state, the dark current flows through the field effect transistor 410. Then, a gate potential at which a substantially average value of the amount of dark current flows through the field effect transistor 410 is generated at the first terminal of the capacitor 420.

Next, the timing generation circuit 600 makes the dark current removal instruction signal RM significant. As a result, the gate potential corresponding to the approximate average value of the amount of dark current immediately before the dark current removal instruction signal RM is made significant is held at the first terminal of the capacitor 420. Thereafter, the dark current removal circuit 400 The approximate average value of the dark current amount is continuously extracted from the current flowing into the current signal input terminal of the circuit 300.

Subsequently, after the timing generation circuit 600 makes the integration instruction signal significant, the reset instruction signal R1 is temporarily made significant.

Thereafter, over the time T, the photoelectric conversion element 1
The current signal obtained by removing the substantially average value of the dark current from the dark current signal output from 00 is input to the integration circuit, and the inflowing charge is accumulated in the capacitor 310. The electric charge accumulated in the capacitor 310 is an integral value of a dark current time T that cannot be extracted by the dark current removing circuit 400.

Next, the timing generation circuit 600 sets the subtraction instruction signal SB to be temporarily significant, and
By temporarily closing the switch element 510 of 00, the output value V1 of the integration circuit 300 at that time is held in the capacitance element 520 of the difference calculation circuit 500.

Thereafter, the light transmission state display signal TR changes from insignificant to significant, that is, the photoelectric conversion element 100
, The state of incidence of the light to be measured starts. As a result, the photoelectric conversion element 100 outputs a current signal including a signal current component and a dark current component.

After an appropriate time T1 has elapsed from the change of the light transmission state display signal TR from insignificant to significant, the reset instruction signal R1 is temporarily made significant, and the electric charge accumulated in the capacitor 310 is released. After that, over a period of time T, the current signal obtained by removing the substantially average value of the dark current from the current signal output from the photoelectric conversion element 100 is integrated with the integrating circuit 30.
0, and the inflowing charge is stored in the capacitor 310. The charge accumulated in the capacitor 310 extends over an integral value of the dark current over the time T that could not be extracted by the dark current removing circuit 400 and over a time T of the signal current corresponding to the reception of the measurement target light received by the photoelectric conversion element 100. It is the value of the sum with the integral value.

The current signal obtained by removing the substantially average value of the dark current from the current signal output from the photoelectric conversion element 100 is the sum of the dark current component and the signal current component, but the dark current component occupies the entire current. The ratio is much lower than the ratio of the dark current component in the current signal output from the photoelectric conversion element 100.

The time T of the current signal obtained by removing the substantially average value of the dark current from the current signal output from the photoelectric conversion element 100
As a result of the integration over the range, the value V of the output signal of the integration circuit 300 is
2 is V2 = V1 ′ + V3 (1) where V1 ′ is a contribution value of a dark current component and V3 is a contribution value of a signal current component. As described above, since most of the dark current in the current signal at the time of output from the photoelectric conversion element 100 has been removed from the current signal to be integrated, V1 ′ >> V
The relationship of 3 does not hold.

By the way, as described above, the output value of the integrating circuit 300 corresponding to the integration over the time T obtained by removing the substantially average value of the dark current amount from the dark current output from the same photoelectric conversion element 100 is V1. Therefore, V1 ′ ≒ V1. Therefore, V2 = V1 + V3 (2) is a very good approximation. Hereinafter, this approximation will be adopted.

In parallel with the integration operation by the integration circuit 300 of the current signal from which the substantially average value of the dark current has been removed from the current signal output from the photoelectric conversion element 100, the reset instruction signal R2 is made insignificant and the switch element 550 is set. To release.

After the integration of the current signal obtained by removing the substantially average value of the dark current from the current signal output from the photoelectric conversion element 100 over the time T, the subtraction instruction signal SB is temporarily made significant, and the difference calculation circuit 500 Is temporarily closed, and the output value V2 of the integrating circuit 300 is
It is transmitted to 10. As a result, the value V3 (= V2−V1)
Is accumulated in the capacitor 540, and the output value V3 is output as the output of the difference calculation circuit. From equation (2), the output value V3 reflects the amount of received light of the measurement target light.

As described above, since V1 >> V3 is not satisfied, the value V3 obtained by calculating the difference between the value V2 and the value V1 can be obtained by securing a good SN ratio and receiving the light to be measured. Reflects the quantity. Therefore, by sampling the value V3, the amount of received light of the light to be measured can be measured at a high SN ratio.

After sampling the value V3, the timing generation circuit 600 returns each signal to the initial state, and prepares for the next measurement.

That is, in the photodetector of this embodiment,
Even if most of the output current signal from the photoelectric conversion element is a dark current component, first, the dark current component and the signal current are removed by removing the approximate average value of the dark current obtained at a point in time that is close in time. After the ratio with the component is improved, the signal component is extracted by securing a good SN ratio by subtracting the estimated residual dark current component obtained when the remaining dark current component is further closer in time. . By measuring the signal components thus extracted, the received light intensity of the light to be measured can be accurately measured.

By arranging the photodetectors of this embodiment one-dimensionally or two-dimensionally and making each detector correspond to a pixel, the majority of the output current signal from the photoelectric conversion element is a dark current component. Even when such a photoelectric conversion element is used, it is possible to realize a one-dimensional or two-dimensional solid-state imaging element that executes a suitable input image capturing while securing a good SN ratio.

The present invention is not limited to the above embodiment, but can be modified. For example, even when the dark current component does not occupy most of the output current of the photoelectric conversion element, the photodetector of the present invention can be used, and the light reception amount of the light to be measured can be measured with extremely high accuracy. it can.

[0058]

As described above in detail, according to the photodetector of the present invention, the light cutoff control unit including the optical chopper or the like periodically changes the incident / non-incident state of the light to be measured to the photoelectric conversion element. First, the average value of the dark current generated by the photoelectric conversion element in the non-incident state is removed, and the ratio between the dark current component and the signal current component is improved. The signal component is extracted by subtracting the estimated residual dark current component obtained at a time point closer to the time. Therefore, a good SN ratio is secured and the signal component is extracted. As a result, without using cooling, even when a photoelectric conversion element in which most of the output current signal from the photoelectric conversion element is a dark current component is used, the SN ratio is secured and the The amount of received light can be measured.

Since the solid-state imaging device of the present invention employs the photodetector of the present invention in accordance with each pixel, the photoelectric conversion device in which most of the output current signal from the photoelectric conversion device is a dark current component. Even when an element is used, a suitable one-dimensional or two-dimensional imaging of an input image can be realized while securing the SN ratio.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a photodetector according to an embodiment of the present invention.

FIG. 2 is a timing chart illustrating the operation of the photodetector according to the embodiment of the present invention.

[Explanation of symbols]

100: photoelectric conversion element, 200: light blocking controller, 210
... Optical chopper, 220 ... Photo interrupter, 300 ...
Integration circuit, 310: capacitive element, 320: operational amplifier, 3
30, 340: switch element, 400: dark current elimination circuit, 410: field effect transistor, 420: capacitance element, 430: switch element, 500: difference calculation circuit, 5
10,550: switch element, 530: differential amplifier, 5
20, 540: Capacitance element, 600: Timing generation circuit.

Claims (5)

[Claims] A light-blocking controller that periodically controls transmission and blocking of the light to be measured; a photoelectric conversion element that generates a charge corresponding to the intensity of the light to be measured and outputs the charge as a current signal; An integration circuit that receives a current signal output from the conversion element and integrates the current signal into a first capacitance element connected between the input and output terminals in accordance with an integration instruction signal; The output dark current signal is input, an approximate average value of the dark current is determined, and a dark average value of the dark current is removed from the current signal input to the integration circuit according to the dark current removal instruction signal. A current removal circuit, an output signal from the integration circuit, and a dark current signal from which the substantially average value has been removed over a predetermined time when the light to be measured is cut off in accordance with the subtraction instruction signal, by the integration circuit. The product after integration While retaining the first value of the output signal of the circuit, the integration circuit integrates the current signal from the photoelectric conversion element from which the substantially average value has been removed over the predetermined time during transmission of the light to be measured. A difference calculation circuit that outputs a signal corresponding to a difference between a second value of the output signal of the integration circuit and the first value, and a light transmission state display signal output from the light blocking control unit, And a timing generation circuit that outputs the integration instruction signal, the dark current removal instruction signal, and the subtraction instruction signal in synchronization with a change in the light transmission state display signal. 2. The photoelectric conversion element is a photodiode having a cathode terminal set to a reference potential, and the integration circuit inputs a dark current signal output from a current signal output from the photoelectric conversion element. The photodetector according to claim 1, further comprising an operational amplifier having a negative input terminal and a positive input terminal set to the reference potential. 3. The dark current elimination circuit includes: a field effect transistor having a source terminal connected to a current signal input terminal of the integration circuit and a drain terminal set to a reference potential; and a gate of the field effect transistor. A second capacitor having a terminal connected to the first terminal, a second terminal set to a reference potential, and a gate terminal of the field-effect transistor connected to the first terminal; The light detection device according to claim 1, further comprising: a first switch element connected to an output terminal of the integration circuit, and opened and closed in response to a dark current removal instruction signal. 4. The photodetector according to claim 1, wherein the light to be measured is infrared light, and the photoelectric conversion element is a photodiode made of InGaAs. 5. A solid-state imaging device wherein the photodetectors according to claim 1 are arranged one-dimensionally or two-dimensionally.