WO2018181013A1

WO2018181013A1 - Light detector

Info

Publication number: WO2018181013A1
Application number: PCT/JP2018/011754
Authority: WO
Inventors: 武廣秦; 尾崎　憲幸; 木村　禎祐; 謙太東; 柏田　真司
Original assignee: 株式会社デンソー
Priority date: 2017-03-29
Filing date: 2018-03-23
Publication date: 2018-10-04

Abstract

A light-receiving array unit (31) receives light radiated from a radiation unit and reflected from an object and outputs, in parallel, pulse signals individually output from a plurality of light-receiving units (80c). A time measuring unit (33c) measures the time elapsed since the input of a radiation timing signal representing the timing of light radiation by the radiation unit. A response obtaining unit (34) obtains, at fixed-interval timing, the number of responses, which is the number of light-receiving units, amongst the plurality of light-receiving units, that output pulse signals, and outputs an adjusted number of responses obtained by subtracting a bias value from the number of responses or dividing the number of responses by the bias value. A memory (6) has addresses associated with values of time measured by the time measuring unit. A histogram generating unit (52) accumulates and stores the adjusted number of responses in the memory address identified from the value of time measured by the time measuring unit as data in that address.

Description

Photodetector

Cross-reference of related applications

This international application is filed with Japanese Patent Application No. 2017-065325 filed with the Japan Patent Office on March 29, 2017 and with the Japan Patent Application No. filed with the Japan Patent Office on January 26, 2018. The contents of Japanese Patent Application No. 2017-0665325 and Japanese Patent Application No. 2018-011556 are hereby incorporated by reference into this international application.

This disclosure relates to a technique for detecting incoming light.

There has been known a photodetector that uses a SPAD array in which a plurality of SPADs are arranged and detects the received light intensity by counting the number of pulse signals (hereinafter, the number of responses) output from individual SPADs on which photons are incident. Yes. SPAD stands for Single Photon Avalanche Diode. SPAD is an avalanche photodiode that operates in Geiger mode and can detect the incidence of a single photon.

In Patent Document 1, it is assumed that the reflected light is received when the number of responses detected by the photodetector is equal to or greater than the trigger threshold after light irradiation, and the flight time of light from irradiation to light reception (hereinafter referred to as TOF). ), And a technique for obtaining a distance from the measured TOF to an object reflecting light is described. TOF is an abbreviation for Time Of Flight. In addition, in order to eliminate the influence of disturbance light incident on the SPAD array, the TOF measurement is repeatedly performed, a histogram in which the number of responses is integrated for each measurement time is created, and the time obtained from the maximum value of the histogram is obtained. The distance is used for calculation.

JP 2014-81254 A

However, as a result of detailed studies by the inventors, the following problems have been found in the prior art described in Patent Document 1. That is, when the disturbance light is strong, the number of responses detected in each measurement increases, and the integrated value in the histogram also increases. In order to prevent the overflow of the integrated value, it is necessary to prepare a memory having a sufficiently large bit width of the data area, that is, a memory having a large storage capacity, as a memory for storing the integrated value.

The present disclosure provides a technique capable of reducing the capacity of a memory for storing a histogram as compared with the prior art in a laser radar that uses a histogram for calculating the flight time of light.
A photodetector that is an aspect of the present disclosure includes a light receiving array unit, a time measuring unit, a response acquisition unit, a memory, and a histogram generation unit.

The light receiving array unit has a plurality of light receiving units that output pulse signals in response to the incidence of photons, receives the reflected light that is irradiated from the irradiation unit and reflected by the object, and is output from each of the plurality of light receiving units. Output pulse signals in parallel. The time measuring unit measures an elapsed time from when an irradiation timing signal indicating a timing at which the irradiation unit irradiates light is input. The response acquisition unit acquires a response number that is the number of light receiving units that output a pulse signal among a plurality of light receiving units at a fixed cycle timing, and subtracts a preset bias value from the response number or Outputs the number of adjustment responses divided. The memory is associated with a time value whose address is measured by the time measuring unit. The histogram generation unit accumulates and stores the number of adjustment responses as data of the address at the memory address specified from the time measured value in the time measuring unit.

According to such a configuration, when generating a histogram by integrating the number of adjustment responses, in order to integrate the number of adjustment responses that are smaller than the number of responses, compared to the case of integrating the number of responses as it is, Memory capacity can be reduced.

In addition, the code | symbol in the parenthesis described in the claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: It does not limit the technical scope of this indication. Absent.

It is a block diagram which shows the structure of the laser radar of 1st Embodiment. It is a graph which illustrates the histogram which accumulated the number of responses in correspondence with measured time. It is explanatory drawing regarding operation | movement of a response acquisition part. It is a block diagram which shows the structure of the laser radar of 2nd Embodiment. It is a block diagram which shows the structure of a disturbance light monitor part. It is explanatory drawing which shows the effect by changing a trigger threshold value according to the strength of disturbance light. It is a block diagram which shows the structure of the laser radar of 3rd Embodiment. FIG. 5 is a circuit diagram showing a configuration of a light receiving unit in the first to third embodiments. It is a block diagram which shows the structure of the laser radar of 4th Embodiment. It is a circuit diagram which shows the structure of the light-receiving part in 4th Embodiment.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Constitution]
The laser radar 1 of this embodiment is mounted on a vehicle, detects various objects existing around the vehicle, and generates information related to the object. As shown in FIG. 1, the laser radar 1 includes an irradiation unit 2, a light detection unit 3, a parameter setting unit 4, a signal processing unit 5, and a memory 6. The light detection unit 3, the signal processing unit 5, and the memory 6 correspond to a light detector. The photodetector may include at least one of the irradiation unit 2 and the parameter setting unit 4.

The irradiation unit 2 repeatedly irradiates pulsed laser light at a preset interval, and inputs an irradiation timing signal indicating the irradiation timing to the light detection unit 3. Hereinafter, the cycle of irradiating laser light is referred to as a measurement cycle.

The light detection unit 3 receives the reflected light of the laser light emitted from the irradiation unit 2, time information Tp representing TOF, which is a flight time of light required from irradiation to light reception, and a light amount representing the light amount at the time of light reception. Information Cp is generated. TOF is an abbreviation for Time Of Flight.

The light detection unit 3 includes a light receiving array unit 31, a trigger unit 32, a timer unit 33, and a response acquisition unit 34.
The light receiving array unit 31 includes M light receiving units 80. M is an integer of 2 or more. Each light receiving unit 80 includes a SPAD. SPAD is an abbreviation for Single Photon Avalanche Diode. The SPAD is an avalanche photodiode that operates in a Geiger mode in which a voltage higher than the breakdown voltage is applied as a reverse bias voltage, and is a detection element that can detect the incidence of a single photon. A total of M SPADs each having one M light receiving unit 80 are two-dimensionally arranged to form a light receiving surface.

As shown in FIG. 8, each light receiving unit 80 includes a SPAD 81, a quench resistor 82, an inverting circuit 83, a D flip-flop circuit (hereinafter referred to as a DFF circuit) 84, and a delay circuit 85. The SPAD 81 has an anode connected to a negative power source and a cathode connected to a positive power source via a quench resistor 82. The quench resistor 82 applies a reverse bias voltage to the SPAD 81. The quench resistor 82 stops the Geiger discharge of the SPAD 81 due to a voltage drop caused by the current flowing through the SPAD 81 when the photons enter the SPAD 81 and the SPAD 81 is broken down. As the quench resistor 82, a resistance element having a predetermined resistance value, or a MOSFET whose on-resistance can be set by a gate voltage is used.

An inversion circuit 83 is connected to the cathode of SPAD81. When the SPAD 81 is not broken down, the input of the inverting circuit 83 is at a high level. In a state where the SPAD 81 is broken down, a current flows through the quench resistor 82, whereby the input of the inverting circuit 83 changes to a low level. The DFF circuit 84 changes its output to a high level at a rising edge at which the output of the inverting circuit 83 changes from a low level to a high level. The output of the DFF circuit 84 is connected to the reset terminal of the latch circuit 84 via the delay circuit 83. The delay circuit 83 inverts the signal level of the output of the DFF circuit 84 and delays the signal level by a preset delay time τ and inputs it to the reset terminal. As a result, when the delay time τ elapses after the output of the DFF circuit 84 changes to the high level, the DFF circuit 84 is reset to change to the low level.

That is, when the photon is incident on the SPAD 81, the light receiving unit 80 outputs a pulse signal P having a pulse width τ in response to the photon. The pulse width τ is set to such a length that can be detected individually when photons are continuously input to the same SPAD 81. Hereinafter, each pulse signal output from the M light receiving units 80 is represented by P ₁ to P _M. The pulse signals P ₁ to P _M are output in parallel.

Trigger unit 32, the number of pulse signals P _{1 ~} P _M from the light receiving array 31 are simultaneously output, i.e., the number of responses is the number of light receiving portion 80 that outputs a pulse signal in response to photons, A trigger signal TG representing the light reception timing is output at a timing exceeding the trigger threshold TH set by the threshold setting unit 4.

The timer unit 33 is a so-called TDC, and measures the time from when the irradiation timing signal is input from the irradiation unit 2 to the light reception timing indicated by the trigger signal TG, and outputs it as time information Tp. TDC is an abbreviation for Time-> Digital-> Converter.

Response acquiring unit 34, the response number Cx is the number of the pulse signals P _{1 ~} P _M from the light receiving array portion 31 are output at the same time, acquired at a timing in accordance with the trigger signal TG, the bias value from the response speed Cx The number of adjustment responses, which is the result of subtracting Cb, is output as light amount information Cp representing the luminance of the received optical signal. That is, the light amount information (that is, the number of adjustment responses) Cp is expressed by equation (1).

Cp = Cx−Cb (1)
The timing according to the trigger signal TG may be a timing when the trigger signal TG is output, or may be a timing obtained by delaying the trigger signal TG by a predetermined delay amount. The bias value Cb is a value set by the parameter setting unit 4. The parameter setting unit 4 includes a mechanical switch that can set the trigger threshold TH and the bias value Cb, or a register that can electrically write the trigger threshold TH and the bias value Cb. Here, only the trigger threshold value TH is arbitrarily set. That is, the trigger threshold value TH corresponds to the target value. The bias value Cb is set to a value obtained by subtracting 1 from the set trigger threshold value TH. That is, the bias value Cb is expressed by equation (2). Substituting equation (2) into equation (1) yields equation (3).

Cb = TH-1 (2)
Cp = Cx-TH + 1 (3)
The trigger threshold TH may be a value larger than 0, and may be an integer or not an integer. The parameter setting unit 4 may be configured such that only the bias value Cb is arbitrarily set, and the trigger threshold value TH is calculated from the set bias value Cb. In this case, the bias value Cb corresponds to the target value. Further, the trigger threshold value TH and the bias value Cb do not necessarily need to be set in conjunction so as to satisfy the relationship shown in the expression (2). In this case, both the trigger threshold value TH and the bias value Cb correspond to the target value.

The memory 6 is an arbitrarily readable / writable RAM. As shown in FIG. 2, the address of the memory 6 is associated with the time bin of the timer unit 33. The time bin is an individual time region divided by the time resolution of the time measuring unit 33. The bit width of the data stored in the memory 6 is at least one of the expected value of the number of responses detected in one measurement and the number of times of integration X which is the number of times of integration when the signal processing unit 5 generates a histogram. It is set appropriately according to The cumulative number X may be 1 or more.

The signal processing unit 5 includes an information generation unit 51 and a histogram generation unit 52.
The histogram generation unit 52 operates for each measurement cycle, and updates the contents of the histogram stored in the memory 6 according to the time information Tp and the light amount information Cp output from the light detection unit 3. Specifically, data is read from the address of the memory 6 associated with the time information Tp, and the result of adding the light amount information Cp to the read data is written to the same address. Thereby, the integrated value of the light quantity information Cp is updated for the time bin indicated by the time information Tp.

The information generation unit 51 operates every X measurement cycles, that is, every time a histogram is generated, and generates information on an object that reflects light based on the histogram generated by the histogram generation unit 52. Specifically, the maximum value of the histogram is extracted as luminance, and for each extracted maximum value, a time bin corresponding to the address from which the maximum value is obtained is specified. Further, based on the combination of the extracted luminance and time bin (ie, TOF), an object including the distance to each object that caused the maximum value on the histogram and the reliability of the object. Generate information. The generated object information is provided to various in-vehicle devices that use the object information via an in-vehicle LAN (not shown).

[1-2. Operation]
As shown in FIG. 3, the response acquisition unit 34 does not use the response number Cx as it is, but uses the adjustment response number obtained by subtracting the bias value Cb as the light amount information Cp output to the signal processing unit 5. For this reason, when generating a histogram, the magnitude of the light quantity information Cp integrated in each measurement cycle is suppressed, and consequently the final integrated value of the light quantity information Cp is suppressed.

[1-3. effect]
According to the first embodiment described in detail above, the following effects are obtained.
(1a) According to the laser radar 1, since the final integrated value of the light quantity information Cp in the histogram is suppressed, if the integration count X is the same, the memory 6 for storing the histogram is compared with the conventional technique. Capacity can be reduced. Moreover, if the capacity | capacitance of the memory 6 is the same, compared with a prior art, the frequency | count X of integration can be increased and detection accuracy can be improved.

(1b) According to the laser radar 1, since the trigger threshold value TH and the bias value Cb can be arbitrarily set by the parameter setting unit 4, the integrated value can be set by changing the set value as appropriate according to the environment used. Can be suppressed more effectively.

[2. Second Embodiment]
[2-1. Difference from the first embodiment]
Since the basic configuration of the second embodiment is the same as that of the first embodiment, differences will be described below. Note that the same reference numerals as those in the first embodiment indicate the same configuration, and the preceding description is referred to.

In the first embodiment described above, the trigger threshold value TH and the bias value Cb are manually set by the parameter setting unit 4a. On the other hand, the second embodiment is different from the first embodiment in that it is automatically variably set.

As shown in FIG. 4, the laser radar 1 a of the present embodiment includes a disturbance light monitor unit 7 added to the laser radar 1 of the first embodiment, and the parameter setting unit 4 a detects the result of the disturbance light monitor unit 7. The trigger threshold value TH is set according to the ambient light information Cm, and the bias value Cb is set according to the above equation (1).

The disturbance light monitoring unit 7 includes a light receiving unit 71 and a counter 72 as shown in FIG.
The light receiving unit 71 has the same configuration as the light receiving unit 80 constituting the light receiving array unit 31. However, the SPAD of the light receiving unit 71 is disposed adjacent to the light receiving surface formed by the M SPADs 81 included in the light receiving array unit 31.

The counter 72 counts the pulse signal output from the light receiving unit 71 at a timing when measurement by the light detection unit 3 is not performed, and generates and outputs disturbance light information Cm according to the count result.

The parameter setting unit 4a variably sets the trigger threshold TH and the bias value Cb according to the disturbance light information Cm obtained from the disturbance light monitoring unit 7 before the irradiation unit 2 emits light for each measurement cycle. Specifically, the trigger threshold value TH and the bias value Cb are set to larger values as the amount of disturbance light indicated by the disturbance light information Cm increases. The parameter setting unit 4a sets the trigger threshold value TH and the bias value Cb based on, for example, the average level of ambient light or the size obtained by adding a predetermined margin to the average level. The disturbance light refers to light other than the reflected light that is irradiated from the irradiation unit 2, reflected by an object, and incident on the light detection unit 3.

[2-2. Operation]
According to the laser radar 1a, when the disturbance light is weak, the trigger threshold value TH is also set to a small value as shown in the upper part of FIG. 6, and when the disturbance light is strong, the trigger threshold value TH is given as shown in the lower part of FIG. Is also set to a large value. In any case, only the part of the response number Cx that exceeds the trigger threshold TH set to the average level of disturbance light, that is, the part obtained by subtracting the bias value Cb from the response number Cx is output as the light amount information Cp. . 3 and 6 exemplify the case where the adjustment response number Cp, which is the subtraction result, is clamped at zero, the present invention is not limited to this.

[2-3. effect]
According to 2nd Embodiment explained in full detail above, there exists the effect (1a) of 1st Embodiment mentioned above, and also there exist the following effects.

(2a) According to the laser radar 1a, it is possible to suppress the histogram overflow while maintaining the detection accuracy even when the disturbance light condition changes. That is, if the trigger threshold value TH and the bias value Cb are fixed to a large value in accordance with the situation where disturbance light is strongest, the detection accuracy of reflected light from an object with low reflection intensity or a distant object decreases. On the other hand, if the trigger threshold value TH and the bias value Cb are fixed to a small value in accordance with a situation where disturbance light is weak, the integrated value of the histogram increases, and it is necessary to increase the memory capacity or reduce the number of integrations. However, the laser radar 1a can suppress both of these disadvantages.

(2b) According to the laser radar 1a, the trigger threshold value TH is set according to the disturbance light, and the light amount information (that is, the number of adjustment responses) Cp is calculated using the bias value Cb set in conjunction with the trigger threshold value TH. Therefore, the light amount information Cp is obtained by removing noise components based on disturbance light. Further, according to the radar radar 1a, since a histogram is generated using such light quantity information Cp, signal light having an excellent signal-to-noise ratio can be extracted.

[3. Third Embodiment]
[3-1. Difference from the first embodiment]
Since the basic configuration of the third embodiment is the same as that of the first embodiment, differences will be described below. Note that the same reference numerals as those in the first embodiment indicate the same configuration, and the preceding description is referred to.

In the first embodiment described above, the trigger threshold value TH and the bias value Cb are manually set by the parameter setting unit 4. On the other hand, the third embodiment is different from the first embodiment in that the trigger threshold value TH and the bias value Cb are automatically variably set. Further, the second embodiment is different from the second embodiment in that the setting of the trigger threshold value TH and the bias value Cb is changed according to the luminance value integration state in the histogram.

As shown in FIG. 7, the laser radar 1b of the present embodiment differs from the laser radar 1 of the first embodiment in the configuration of a response acquisition unit 34b, a parameter setting unit 4b, and a signal processing unit 5b.
The response acquisition unit 34 b includes a maximum value monitor unit 341 in addition to the configuration that realizes the function of the response acquisition unit 34. The maximum value monitor unit 341 monitors the response number Cx output from the light receiving array unit 31 and extracts the maximum value as the predicted response number B. The extraction of the predicted response number B may be performed by an external instruction, may be performed periodically, or may be performed when a change in the surrounding environment is detected by some on-vehicle sensor.

The signal processing unit 5 b includes a margin calculation unit 53 in addition to the information generation unit 51 and the histogram generation unit 52.
The margin calculation unit 53 obtains a margin value A that represents the margin of memory each time the histogram generation unit 52 updates the histogram. As shown in FIG. 2, the maximum value among the maximum values of the histogram is extracted and set as the value Pmax. Let Dmax be the upper limit of integration, which is the upper limit of data that can be stored in accordance with the bit width of the data area constituting the memory. The margin value A may be obtained by equation (3) or may be obtained by equation (4). Where α represents the remaining number of integrations until the histogram generation is completed. A in FIG. 2 indicates the margin value A obtained by equation (3).

A = Dmax−Pmax (3)
A = (Dmax−Pmax) / α (4)
The parameter setting unit 4b compares the trigger threshold value TH set at that time with AB in accordance with the predicted response number B and the margin value A, and adopts the larger one as the trigger threshold value TH.

The parameter setting unit 4b executes the variable setting of the trigger threshold value TH using A and B only when the remaining number of times of integration α is less than or equal to a predetermined value or when the margin value A is less than or equal to a predetermined value. May be.

The trigger threshold value TH to be compared with AB may be a fixed value, or may be a variable value set according to the situation as shown in the second embodiment. Further, the parameter setting unit 4b sets the bias value Cb by the above-described method instead of the trigger threshold value TH, and sets the trigger threshold value TH from the set bias value Cb using the relationship of the expression (1). It may be configured.

[3-2. effect]
According to 2nd Embodiment explained in full detail above, there exists the effect (1a) of 1st Embodiment mentioned above, and also there exist the following effects.

(3a) In the laser radar 1b, since the trigger threshold value TH and thus the bias value Cb are set according to the margin value A, it is possible to further suppress the overflow of the integrated value of the light amount information Cp in the histogram. In other words, by having this function, it is possible to further improve the detection accuracy by reducing the memory capacity or increasing the number of integrations X.

[4. Fourth Embodiment]
[4-1. Difference from the first embodiment]
Since the basic configuration of the fourth embodiment is the same as that of the first embodiment, differences will be described below. Note that the same reference numerals as those in the first embodiment indicate the same configuration, and the preceding description is referred to.

In the first embodiment described above, the trigger signal TG is generated, and the histogram is updated using only the light amount information Cp obtained at the timing of the trigger signal TG. On the other hand, the fourth embodiment is different from the first embodiment in that the light amount information Cp is repeatedly generated in synchronization with the clock and the histogram is updated using all the light amount information Cp.

As shown in FIG. 9, the laser radar 1 c of this embodiment includes an irradiation unit 2, a light detection unit 3 c, a parameter setting unit 4 c, a signal processing unit 5 c, and a memory 6.
The light detection unit 3c includes a light receiving array unit 31c, a timer unit 33c, and a response acquisition unit 34c.

The light receiving array part 31c has M light receiving parts 80c. Each of the M light receiving portions 80c has a SPAD, and is similar to the first embodiment in that a light receiving surface in which M SPADs are two-dimensionally arranged is formed.

Each light receiving unit 80c includes a SPAD 81, a quench resistor 82, an inverting circuit 83, and a DFF circuit 84, as shown in FIG. That is, the light receiving unit 80c is different from the light receiving unit 80 of the first embodiment in that the delay circuit 85 is omitted and the connection state of the DFF circuit 84 is different.

The DFF circuit 84 latches the output of the inverting circuit 83 at the timing of the rising edge of the clock CK and outputs this as a pulse signal P. Further, the output of the DFF circuit 84 is reset by the reset signal RS.

That is, when the photon is incident on the SPAD 81, the light receiving unit 80c outputs the pulse signal P in response thereto. At this time, the pulse width of the pulse signal Pr output from the inverting circuit 83 continues until the Geiger discharge of the SPAD 81 is stopped by the voltage drop generated by the current flowing through the quench resistor 82. This pulse signal Pr is converted into a pulse signal P synchronized with the clock CK by the DFF circuit 84. That is, the pulse width of the pulse signal P output from the DFF circuit 84 includes a shift corresponding to the quantization error due to the clock CK.

Referring back to FIG. 9, the time measuring unit 33c has a synchronous counter that operates according to the clock CK. The timing unit 33c starts counting by the irradiation timing signal input from the irradiation unit 2, continues the counting operation at least for the time required for the optical signal to reciprocate the maximum detection distance, and calculates the count value as time information. Output as Tp. That is, the time information Tp changes in synchronization with the clock CK.

Response obtaining unit 34c is a response number Cx is the number of the pulse signals P _{1 ~} P _M outputted simultaneously from the light-receiving array portion 31c, determined at all times by using an encoder or the like. Further, the response acquisition unit 34c repeatedly calculates an adjustment response number, which is a result of subtracting the bias value Cb from the response number Cx, for each timing of the clock CK, and the calculation result represents the light amount representing the luminance of the received optical signal. Output as information Cp. That is, the light amount information Cp changes in synchronization with the clock CK, similarly to the time information Tp.

The parameter setting unit 4c variably sets the bias value Cb according to the disturbance light information Cm output from the signal processing unit 5c before the irradiation unit 2 emits light for each measurement cycle. Specifically, like the parameter setting unit 4a of the second embodiment, the parameter setting unit 4c sets the bias value Cb to a larger value as the amount of disturbance light indicated by the disturbance light information Cm increases.

The signal processing unit 5 c includes an information generation unit 51, a histogram generation unit 52, and an ambient light monitor unit 54.
The histogram generation unit 52 operates in the same manner as in the first embodiment, but the time information Tp and the light amount information Cp change in synchronization with the clock CK. Therefore, every time the time information Tp changes, the histogram generation unit 52 corresponds to the time information. The stored value of the address in the memory 6 is updated using the light amount information Cp.

The disturbance light monitor unit 54 is configured to perform the bias value from the end of the information generation by the information generation unit 51 to the start of the next measurement cycle, that is, during the period when the irradiation unit 2 is not irradiated with light. Is set to Cb = 0, the histogram generation unit 52 is caused to generate a histogram. Further, the disturbance light monitor unit 54 outputs the generated histogram itself or the average level of disturbance light extracted from the histogram as disturbance light information Cm.

[4-2. effect]
According to the fourth embodiment described in detail above, the effect (1a) of the first embodiment and the effect (2a) of the second embodiment described above are exhibited, and the following effects are further achieved.

(4a) According to the laser racer 1c, since the time information Tp and the light amount information Cp are always generated at the timing synchronized with the clock CK, it is not necessary to generate the trigger signal TG and the trigger unit 32 can be omitted. Can be simplified.

(4b) According to the laser radar 1c, since the disturbance light information Cm is generated using the light receiving array unit 31c used for measurement, a new sensor is not added to generate the disturbance light information Cm. High functionality can be realized.

[5. Other Embodiments]
As mentioned above, although embodiment of this indication was described, this indication is not limited to the above-mentioned embodiment, and can carry out various modifications.

(5a) In the above embodiment, the light amount information (that is, the adjustment response number) Cp is obtained by subtracting the bias value Cb from the response number Cx, but the present disclosure is not limited to this. For example, the light amount information Cp may be obtained by dividing the bias value Cb from the response number Cx. In this case, the trigger threshold value TH itself may be used as the bias value Cb. However, the trigger threshold value TH must be set to a value larger than 1 so that Cp <Cx / TH.

(5b) In the above embodiment, the trigger threshold value TH and the bias value Cb are set manually, based on the ambient light information Cm, the margin value A, and the predicted response number B. However, the present disclosure is limited to this. is not. For example, at least one of date / time information representing the current date / time, position information representing the current position, direction information representing the current traveling direction, and weather information representing the weather at the current position, a GPS device, a wireless communication device, etc. The trigger threshold value TH and the bias value Cb may be set on the basis of the amount of disturbance light obtained from the obtained information and estimated from the obtained information.

(5c) In the second embodiment, the disturbance light monitor unit 7 that measures the physical quantity of light is used to generate the disturbance light information Cm. However, the present disclosure is not limited to this. The disturbance light here refers to a response other than the signal emitted by itself, and the disturbance light information Cm only needs to know the magnitude of the disturbance light. Therefore, instead of the disturbance light monitor unit 7 or in addition to the disturbance light monitor unit 7, for example, a reflection characteristic monitor unit may be used. The reflection characteristic monitor unit detects at least one of the reflection characteristic of the object, specifically, reflectance, reflection intensity distribution, wavelength characteristic, and deflection characteristic, and generates disturbance light information Cm from the detection result.

(5d) In the second embodiment, the disturbance light monitor unit 7 is applied to the single light receiving array unit 31, but the present disclosure is not limited to this. For example, when a light receiving surface is formed by a plurality of pixels and each pixel is composed of a plurality of SPADs, the light detection unit 3 (that is, the light receiving array unit 31, the trigger unit 32, the time measuring unit 33, the response acquisition) is obtained for each pixel. Part 34). The disturbance light monitoring unit 7 may measure the disturbance light for each pixel, and the threshold setting unit 4a may be configured to change the trigger threshold TH for each pixel. The same applies when a reflection characteristic monitor unit is used instead of the ambient light monitor unit 7.

(5e) Although the maximum value of the observed response number Cx is used as the predicted response number B in the third embodiment, the present disclosure is not limited to this. For example, the number M of the light receiving units 311 constituting the light detecting unit 3 may be used as the predicted response number B. The trigger threshold TH and the predicted response number B may be set based on a past histogram, or may be set based on at least one history of the trigger threshold TH, the bias value Cb, and the response number Cx. Good. In this case, for example, the number of responses measured last time may be used, or any of the most recent average number of responses, the maximum number of responses, and the number of most frequent responses may be used. Furthermore, the trigger threshold value TH, the bias value Cb, and the predicted response number B may be set based on data obtained by analyzing past data and removing abnormal values.

(5f) In the first to third embodiments, the bias value Cb is set by the parameter setting unit, but the bias value may be set by the response acquisition unit. In this case, the response acquisition unit may acquire the bias threshold value TH and calculate the bias value Cb based on the acquired bias value TH.

(5g) The fourth embodiment differs from the first to third embodiments in the configuration of the light detection unit, but the disturbance light monitoring unit 54 in the fourth embodiment is changed to the first to third embodiments. Alternatively, the disturbance light monitoring unit 7 in the second embodiment, the maximum value monitoring unit 341 and the margin calculation unit 53 in the third embodiment may be applied to the fourth embodiment.

(5h) 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 from the wording described in the claims are embodiments of the present disclosure.

(5i) In addition to the laser radar described above, the present disclosure can be realized in various forms such as a system including the laser radar as a constituent element and a light amount information integration method.

Claims

It has a plurality of light receiving sections (80c) that output pulse signals in response to the incidence of photons, receives reflected light that is irradiated from the irradiation section and reflected by the object, and is output from each of the plurality of light receiving sections. A light receiving array section (31) configured to output the pulse signals in parallel;
A time measuring unit (33c) configured to measure an elapsed time since an irradiation timing signal indicating a timing at which the irradiation unit irradiated light is input;
At each fixed cycle timing, the number of responses, which is the number of light receiving units outputting the pulse signal among the plurality of light receiving units, is obtained, and a preset bias value is subtracted or divided from the number of responses. A response acquisition unit (34) configured to output the number of adjustment responses;
A memory (6) in which an address is associated with a time value measured by the time measuring unit;
A histogram generation unit (52) configured to accumulate and store the number of adjustment responses as data of the address at the address of the memory specified from the time measured value in the time measuring unit;
A photodetector.
It has a plurality of light receiving sections (80) that output pulse signals in response to the incidence of photons, receives reflected light that is irradiated from the irradiation section and reflected by the object, and is output from each of the plurality of light receiving sections. A light receiving array section (31) configured to output the pulse signals in parallel;
The number of responses, which is the number of light receiving units outputting the pulse signal among the plurality of light receiving units, is compared with a trigger threshold, and a trigger signal is output at the timing when the number of responses reaches the trigger threshold. A trigger unit (32) configured as follows:
At each timing according to the trigger signal, it is configured to measure the time from the input of the irradiation timing signal indicating the timing at which the irradiation unit has irradiated the light to the light reception timing of the optical signal indicated by the trigger signal. The timekeeping section (33),
A response acquisition unit (34) configured to acquire the number of responses at each timing according to the trigger signal and output an adjusted response number obtained by subtracting or dividing a preset bias value from the response number. When,
A memory (6) in which an address is associated with a time value measured by the time measuring unit;
A histogram generation unit (52) configured to accumulate and store the number of adjustment responses as data of the address at the address of the memory specified from the time measured value in the time measuring unit;
A photodetector.
The photodetector of claim 1, comprising:
A parameter setting unit (4) configured to set the bias value as a target value and variably set the target value;
Photo detector.
The photodetector according to claim 2, comprising:
A parameter setting unit (4) configured to set at least one of the trigger threshold value and the bias value as a target value and variably set the target value;
Photo detector.
The photodetector according to claim 4, comprising:
The parameter setting unit is configured to set the trigger threshold as the target value,
The response acquisition unit is configured to obtain a value obtained by subtracting 1 from the trigger threshold as the bias value, and obtain the adjustment response number by subtraction.
Photo detector.
The photodetector according to claim 4, comprising:
The parameter setting unit sets the trigger threshold and the bias value as the target values, and links the bias value and the trigger threshold so that the bias value is a value obtained by subtracting 1 from the trigger threshold. Configured to set,
The response acquisition unit is configured to obtain the adjustment response number by subtraction.
Photo detector.
The photodetector according to claim 3 or 6, wherein
The parameter setting unit is configured to acquire disturbance light information representing the amount of disturbance light, and to set the target value to a larger value as the amount of light indicated by the disturbance light information increases.
Photo detector.
The photodetector according to claim 7, comprising:
A disturbance light monitor unit (7) configured to measure disturbance light incident on the light receiving array unit;
The parameter setting unit is configured to acquire a measurement value in the disturbance light monitor unit as the disturbance light information.
Photo detector.
The photodetector of claim 8, comprising:
The disturbance light monitor unit is a state where the bias value of the response acquisition unit is set to zero, and the histogram generation unit accumulates the adjustment response number without performing irradiation by the irradiation unit, Configured to be a measurement result of the disturbance light,
Photo detector.
The photodetector according to claim 8 or 9, wherein
A plurality of pixels that receive the reflected light;
For each pixel, at least the light receiving array unit and the response acquisition unit are provided,
The disturbance light monitoring unit is configured to measure the disturbance light for each pixel,
The parameter setting unit is configured to change the target value for each pixel.
Photo detector.
The photodetector according to claim 3 or claim 4, wherein
The parameter setting unit is configured to acquire reflection characteristic information indicating the reflection amount of an object, and to set the target value to a larger value as the reflection amount indicated by the reflection characteristic information is larger.
Photo detector.
The photodetector of claim 11, comprising:
A reflection characteristic monitor unit configured to measure a reflection characteristic of an object that is a source of reflected light incident on the light receiving array unit;
The parameter setting unit is configured to acquire a measurement value in the reflection characteristic monitor unit as the reflection characteristic information.
Photo detector.
The photodetector of claim 12, comprising:
A plurality of pixels that receive the reflected light;
For each pixel, at least the light receiving array unit and the response acquisition unit are provided,
The reflection characteristic monitor unit is configured to measure the reflection characteristic for each pixel,
The parameter setting unit is configured to change the target value for each pixel.
Photo detector.
The photodetector according to claim 3 or claim 4, wherein
The parameter setting unit is configured to set the target value using date and time information, map information, and direction information.
Photo detector.
The photodetector according to claim 3 or claim 4, wherein
The parameter setting unit is configured to set the target value using a past setting value by the parameter setting unit;
Photo detector.
The photodetector according to claim 3 or claim 4, wherein
The parameter setting unit is configured to set the target value using an integration result of the number of adjustment responses generated in the past by the histogram generation unit.
Photo detector.
The photodetector according to claim 3 or claim 4, wherein
The parameter setting unit is configured to set the target value to a value obtained by subtracting a margin value that can be accumulated in the memory from the predicted response number of the light receiving array unit.
Photo detector.
The photodetector of claim 17, comprising:
The parameter setting unit is configured to set a difference between a maximum value of data that can be stored in the memory and a maximum value in the histogram stored in the memory as the margin value.
Photo detector.
The photodetector according to claim 17, wherein the parameter setting unit includes a maximum value of data that can be stored in the memory and a maximum value in the integration result of the number of adjustment responses stored in the memory. A value obtained by dividing the difference by the remaining number of integrations is configured as the margin value.
Photo detector.
The photodetector according to any one of claims 17 to 19,
The parameter setting unit is configured to set the number of the light receiving units included in the light receiving array unit as the predicted response number.
Photo detector.
The photodetector according to any one of claims 17 to 19,
The response acquisition unit is configured to observe a maximum number of responses that is a maximum value of the number of responses,
The parameter setting unit is configured to set the maximum response number as the predicted response number.
Photo detector.
The photodetector according to any one of claims 1 to 21,
A distance calculation unit (51) configured to obtain a distance to an object that has reflected light based on an integration result of the number of adjustment responses generated by the histogram generation unit.
A photodetector.
The photodetector according to any one of claims 1 to 22,
A photodetector further comprising the irradiation unit.
The photodetector according to any one of claims 1 to 23, wherein:
The number of responses is the number of the light receiving units that simultaneously output the pulse signals.