WO2018235944A1

WO2018235944A1 - Optical distance measurement device

Info

Publication number: WO2018235944A1
Application number: PCT/JP2018/023817
Authority: WO
Inventors: 晶文植野; 武廣秦; 柏田　真司
Original assignee: 株式会社デンソー
Priority date: 2017-06-22
Filing date: 2018-06-22
Publication date: 2018-12-27

Abstract

The optical distance measurement device (1A, 1B, 1C, 1D) according to one aspect of the present disclosure is provided with an irradiation unit (3), a plurality of SPADs (4), a plurality of signal output units (6, 8), a response number detection unit (20, 40), a timing recognition unit (45), and a timing correction unit (56, 57). The response number detection unit is configured to detect, on the basis of a pulse signal, a response number representing the number of responding SPADs. The timing recognition unit is configured to recognize a temporary timing on the basis of the state of time-series change in the number of responses and to recognize, according to the temporary timing, a detection timing that represents a timing at which the optical distance measurement device has detected light. The timing correction unit is configured to acquire a correction time that represents a time difference between the temporary timing and a real timing corresponding to the distance to an object, and to set, as the detection timing, the timing obtained by correcting the temporary timing by the amount of the correction time.

Description

Optical ranging device

Cross-reference to related applications

This international application is filed in Japan Patent Application No. 2017-122287 filed with the Japan Patent Office on June 22, 2017, and the Japanese Patent Application filed with the Japan Patent Office on June 11, 2018. The Japanese Patent Application No. 2017-122287 and the Japanese Patent Application No. 2018-111123 are hereby incorporated by reference in their entirety.

The present disclosure relates to a light ranging device that measures a distance from a round trip time of light to an object, and relates to a technique for detecting light using a SPAD.

Patent Document 1 below proposes a technique for detecting light incident on a SPAD by detecting the presence or absence of responses of a plurality of SPADs in synchronization with a clock. In the technique of Patent Document 1 below, it is considered that the number of SPADs responding (hereinafter, the number of SPAD responses) is detected in synchronization with a clock, and the number of SPAD responses increases as the light intensity increases. .

JP, 2014-081253, A

According to the technique of Patent Document 1, the smaller the number of SPADs in response, and the longer the time during which SPAD responds, that is, the time when SPAD outputs a pulse, the distance to the object. Tend to lag behind the true timing corresponding to

As a result of detailed investigations by the inventor, it has been found that in the technique of Patent Document 1, it is difficult to accurately estimate the timing at which light is detected from the number of responses of SPAD.
One aspect of the present disclosure is to provide a technology that enables a SPAD to accurately estimate the timing at which light is detected by a light ranging device that detects light using a SPAD.

The optical distance measuring apparatus according to one aspect of the present disclosure includes an irradiation unit, a plurality of SPADs, a plurality of signal output units, a response number detection unit, a timing recognition unit, and a timing correction unit.
The irradiating unit is configured to irradiate a light wave to an area where an object is to be detected. The plurality of SPADs are configured to respond to the incidence of photons including reflected waves of light waves. The plurality of signal output units are configured to output a pulse signal when the SPAD responds to each of the plurality of SPADs. The response number detection unit is configured to detect the number of responses representing the number of SPADs that are responding based on the pulse signal.

The timing recognition unit recognizes temporary timing based on the change state of the number of responses along the time series, and recognizes detection timing representing the timing at which the optical distance measuring device detects light according to the temporary timing. Configured The timing correction unit obtains a correction time representing a time difference between the temporary timing and the true timing corresponding to the distance to the object, and detects the timing corrected by the correction time with respect to the temporary timing. Configured to set.

According to such an optical distance measuring apparatus, since the timing obtained by correcting the provisional timing by the correction time is recognized as the detection timing, the true timing and the provisional timing corresponding to the distance to the object are obtained. Time difference can be corrected. Therefore, the timing at which the SPAD detects light can be accurately estimated.

In addition, the code in the parentheses described in the claims indicates the correspondence with the specific means described in the embodiment described later as one aspect, and the technical scope of the present disclosure is limited. Absent.

It is a block diagram showing composition of an optical ranging device of a 1st embodiment. It is an explanatory view showing composition of an optical ranging device. It is an operation example of a light ranging device model in a 1st embodiment. It is a graph which shows an example of the light reception amount and the time change of a level value. It is explanatory drawing which shows the example of a response of SPAD when light is strong. It is explanatory drawing which shows the example of a response of SPAD when light is weak. It is a graph which shows an example of the map used for correction | amendment by a light quantity. It is a graph which shows an example of the effect of a distance correction result. It is a graph which shows an example of an offset value when there are few disturbing lights. It is a graph which shows an example of an offset value when disturbance light is large. It is a graph which shows an example of the map used for correction | amendment by offset value and light quantity. It is a block diagram which shows the structure of the optical distance measuring apparatus of 3rd Embodiment. It is a graph which shows an example of the map used for the correction | amendment by response duration. It is a block diagram which shows the structure of the optical distance measuring apparatus of 4th Embodiment. It is a graph which shows an example of the map used for the correction | amendment by saturation. It is a graph which shows an example of the process which integrates the response number of SPAD by multiple light wave irradiation.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. First embodiment]
[1-1. Constitution]
An optical distance measuring apparatus 1A shown in FIG. 1 is an apparatus for measuring a distance from a round trip time of light to an object, and is a light detector for detecting light using an avalanche photodiode (hereinafter referred to as APD), particularly SPAD. Equipped with The optical distance measuring apparatus 1A recognizes the distance to the object by, for example, emitting signal light such as a laser radar, and using a light detector to recognize the timing at which the reflected light is received with respect to the timing at which the signal light is emitted. Have a function to

SPAD is an abbreviation of Single Photon Avalanche Diode. SPAD operates by applying a voltage higher than the breakdown voltage as a reverse bias voltage. Since SPAD breaks down upon incidence of photons, this type of photodetector usually detects a voltage change when SPAD breaks down and outputs a digital pulse of a predetermined pulse width (hereinafter referred to as a pulse signal) Configured.

As shown in FIG. 1, the optical distance measuring apparatus 1 </ b> A includes an irradiation unit 3, a plurality of light receiving units 2, and a plurality of level detection circuits 20. In addition, the optical distance measuring apparatus 1A may include an adder 40, a peak detection unit 45, and an arithmetic unit 50A. At least the plurality of light receiving units 2 and the plurality of level detection circuits 20 of the light ranging device 1A constitute a light detector that detects light. In the present embodiment, part of the adder 40 and the peak detection unit 45 also constitutes a light detector.

The irradiation unit 3 includes, for example, a laser diode as a light source, and irradiates a light wave to a region where it is intended to detect an object to be a target of distance measurement from the light source. The irradiation unit 3 irradiates the light wave every cycle set according to a clock to be described later, for example, every 100 ms, so that the reflected wave can be received by the light detector.

As shown in FIG. 2, the plurality of light receiving units 2 are arranged in a grid in the vertical and horizontal directions to form a light receiving unit array 10 that constitutes one pixel for light detection. Each light receiving unit 2 is configured to output a pulse signal as a response when photons are incident. As shown in FIG. 2, each light receiving unit 2 includes an SPAD 4, a quench resistor 6, and a pulse output unit 8.

SPAD 4 has a cathode connected to reverse bias voltage VB and an anode connected to quench resistor 6 and pulse output 8. The quench resistor 6 is connected in series to the conduction path to the SPAD 4.

The quench resistor 6 applies a reverse bias voltage VB to the SPAD 4 and generates a voltage drop due to the current flowing through the SPAD 4 when photons are incident on the SPAD 4 and the SPAD 4 breaks down, thereby stopping the Geiger discharge of the SPAD 4 It is a thing. The quench resistor 6 is formed of a resistive element having a predetermined resistance value, or a MOSFET or the like whose on-resistance can be set by a gate voltage.

The pulse output unit 8 is connected to the connection point of the SPAD 4 and the quench resistor 6. The pulse output unit 8 outputs the value 1 when the SPAD 4 is not broken down. In the pulse output unit 8, when the SPAD 4 breaks down, a current flows through the quench resistor 6, and a voltage equal to or greater than the threshold voltage is generated at both ends of the quench resistor 6, the above-described pulse signal has a value 0 Output digital pulse. That is, the quench resistor 6 and the pulse output unit 8 are configured to output a pulse signal when the SPAD 4 responds to each of the plurality of SPADs 4.

Each level detection circuit 20 is provided for each light receiving unit 2 and has a function of detecting whether a pulse signal from the light receiving unit 2 is obtained, that is, whether the SPAD 4 responds.

The level detection circuit 20 includes an inverter 21 and a clock synchronization unit 22. The inverter 21 is configured as a known inverter in a logic circuit that inverts and outputs an input. The clock synchronization unit 22 is configured as a clock synchronization circuit that receives a clock (CLK) that is a periodic pulse, and outputs an input signal value at the time of clock input each time the clock is input.

The input signal value here is the output of the inverter 21 in the clock synchronization unit 22. The clock synchronization unit 22 is configured as, for example, a D flip flop. The clock synchronization unit 22 outputs the value input from the inverter 21 each time a clock is input.

The adders 40 are known adders that add and output the pulses output from the respective level detection circuits 20. The output from the adder 40 is referred to as a level value. The level value is a response number representing the number of light receiving units 2 outputting pulse signals, that is, the number of light receiving units 2 outputting a value of 0. Therefore, the level value also indicates the intensity of incident light. It can be said.

A pulse signal is output from the light receiving unit 2 configured in this way at a frequency according to the amount of light in the surrounding area. For this reason, when strong light such as sunlight is incident on the light receiving unit 2, the number of pulse signals output from the light receiving unit 2 per unit time, that is, the pulse rate is significantly increased.

The peak detection unit 45 recognizes a detection timing representing a timing at which the optical distance measuring device 1A detects light by recognizing a temporary timing obtained based on a change state of the level value along the time series. However, the detection timing here is a provisional detection timing before correction.

Further, the provisional timing indicates the timing at which this change state satisfies a preset condition based on the change state of the number of responses along the time series. Specifically, the provisional timing is timing to be a reference for obtaining detection timing, and here, for example, a timing at which the actual level value becomes the maximum value is adopted. Note that as the provisional timing, any timing that satisfies a predetermined condition such as the timing when the calculated level value becomes the maximum value or the timing when the level value increases and becomes the predetermined value may be adopted.

When adopting the timing at which the calculated level value becomes the maximum value, this timing is based on the rate of change of the level value as the slope of the tangent when the level value is a specific value when the level value increases and decreases. It may be expressed as the timing of the intersection of a plurality of tangents. Specifically, in a graph as shown in FIG. 4 in which the horizontal axis is time series and the vertical axis is level value, when crossing points at a plurality of tangents when the level value is a predetermined value such as half of the maximum value are obtained Good.

Further, the timing when the calculated level value becomes the maximum value may be the timing when the level value becomes the center value with respect to a plurality of timing when the level value becomes a specific value. The peak detection unit 45 acquires the operating state of the irradiation unit 3, that is, the irradiation timing of the light wave. Then, a signal corresponding to the difference between the irradiation timing and the provisional timing is output. The output from the peak detection unit 45 is input to the calculation unit 50A.

The arithmetic unit 50A is mainly configured of a well-known microcomputer including a CPU 51 and a semiconductor memory (hereinafter, memory 52) such as a RAM, a ROM, and a flash memory. The various functions of the calculation unit 50A are realized by the CPU 51 executing a program stored in a non-transitional tangible recording medium. In this example, the memory 52 corresponds to a non-transitional tangible storage medium storing a program.

Also, by executing this program, a method corresponding to the program is executed. Note that the non-transitional tangible recording medium has a meaning excluding the electromagnetic wave in the recording medium. Further, the number of microcomputers constituting the arithmetic unit 50A may be one or more.

[1-2. Processing and operation]
The arithmetic unit 50A includes a response time correction unit 56 and a light amount correction unit 57 as shown in FIG. 1 as a configuration of functions realized by the CPU 51 executing a program. The method for realizing these elements constituting the arithmetic unit 50A is not limited to software, and part or all of the elements may be realized using one or more hardware. For example, when the above function is realized by an electronic circuit that is hardware, the electronic circuit may be realized by a digital circuit including many logic circuits, an analog circuit, or a combination thereof.

Here, an operation example of the optical distance measuring apparatus model in which four SPADs 4 are provided is shown in FIG. The level value indicates the maximum value at the timing when the number of responding SPADs 4 becomes maximum. In the example shown in FIG. 3, when the SPAD [3] responds, the level value becomes 4 and becomes the maximum value. In FIG. 3, the light receiving unit 2 is described as SPAD [N]. However, N is a number for specifying one of the four light receiving units 2 by a number, and is any one of 0, 1, 2, 3.

Here, in the optical distance measuring apparatus 1A of this embodiment, the relationship between the amount of light received by the signal light, that is, the amount of light incident on the plurality of SPADs, and the level value is as shown in FIG.
Referring to FIG. 4, the level value increases as the amount of light received by the signal light increases. However, a time difference ΔT1 occurs between the true timing P at which the amount of light received by the signal light is maximum and the timing L at which the level value is maximum. Therefore, in order to detect the timing of light reception using the level value, it is preferable to correct by the time difference ΔT1.

The true timing P is the timing corresponding to the distance to the object, and the timing at which the amount of light emitted to the optical distance measuring device 1A is maximum is ideal, but the true timing P is Since it can not be detected by the optical distance measuring apparatus 1A, when using the true timing P, the timing experimentally obtained in advance is used.

In this embodiment, in order to recognize more accurate detection timing, the timing L at which the level value becomes maximum is the timing at which the amount of light received by the signal light is maximized by the functions of the response time correction unit 56 and the light amount correction unit 57. Correct to get closer to P. That is, in the functions as the response time correction unit 56 and the light amount correction unit 57, the time difference ΔT1 from the true timing P at which the light reception amount peaks with respect to the temporary timing, here the timing L at which the response number peaks It is calculated as a correction time, and this timing is recognized as the timing when light is detected.

In detail, the response time correction unit 56 corrects the tentative timing using the correction time corresponding to the length of the response continuation time that represents the time for which the responding SPAD 4 continues the response. In this embodiment, a fixed value set in advance is adopted as the correction time corresponding to the response continuation time.

The light quantity correction unit 57 is configured to calculate the correction time according to the light reception environment of the light ranging device 1A. In the following description, although the configuration in which the light amount correction unit 57 calculates the correction time using a map is described, the present invention is not limited to this configuration, and the correction time is calculated using an equation that returns the correction time when a parameter indicating the light reception environment is input. It may be calculated.

Here, the light amount correction unit 57 obtains a correction time according to the light intensity in the light reception environment. The light intensity is a value indicating the magnitude of the amount of incident light, and, for example, the height of the peak of the level value or the rate of change of the level value (for example, the slope of the tangent at a specific point in the level value graph of FIG. 4). It can be obtained by the size.

When the light intensity is relatively strong, as shown in FIG. 5, the time difference ΔTA between the timing A1 at which the incident light quantity peaks and the timing A2 at which the level value reaches the maximum value Lmax becomes relatively small. When the light intensity is strong, the amount of incident light is large, so many SPADs 4 respond in a relatively short time, and when the amount of incident light reaches a peak, most SPADs 4 have responded It is from.

On the other hand, when the light intensity is weak, as shown in FIG. 6, the time difference ΔTB between the timing B1 at which the incident light quantity peaks and the timing B2 at which the level value reaches the maximum Lmax is large relative to the time difference ΔTA. Become. When the light intensity is weak, the amount of incident light is small, so the SPAD 4 responds gradually according to the increase in the amount of light.

In the case where the light shown in FIG. 5 is strong, the number of responses increases by 8 during the period [A] which is the initial stage of light detection, and the period of [B] where the light intensity reaches its peak and the light intensity weakens. In the period [C], the number of responses is increased by 4 or 3 which is less than 8. In the example shown in FIG. 6 where the light is weak, the number of responses increases by one in the period of [A], and the number of responses increases by three or four more than one in the periods of [B] and [C]. That is, when the light is strong, many SPADs 4 respond in the early stage of detection, and the increase in the number of responses slows down in the subsequent period. As a result, a difference occurs between the timings A2 and B2 at which the level value becomes the maximum value Lmax between when the light is strong and when the light is weak.

Therefore, the light amount correction unit 57 of the present embodiment obtains the correction time according to the light intensity according to the map as shown in FIG. That is, as the maximum value Lmax of the level value increases, a map in which the correction amount decreases is adopted. When the maximum value Lmax of the level value becomes large, the SPAD 4 approaches saturation before the timing when the incident light amount peaks, and this timing is shifted to the near distance side than the timing when the original level value becomes the maximum Lmax. is there.

The light amount correction unit 57 sets a time value obtained by adding the correction time corresponding to the light intensity and the correction time corresponding to the response duration time obtained by the response time correction unit 56 to the above-described time difference ΔT1, as a level value. Is corrected so as to be close to the true timing P at which the light reception amount peaks. Specifically, the timing obtained by subtracting the time difference ΔT1 from the timing L at which the level value becomes maximum is recognized as a detection timing.

Since the provisional timing is corrected by ΔT1 to be the true timing by the functions of the response time correction unit 56 and the light amount correction unit 57, the difference between the irradiation timing and the provisional timing is the irradiation timing and the true timing. Corrected to the difference between

As a result, as shown in FIG. 8, the calculated distance representing the distance to the object obtained only by the peak of the level value is corrected to be the corrected distance. The corrected distance roughly corresponds to the true distance to the object.

[1-3. effect]
According to the first embodiment described above, the following effects can be obtained.
(1a) The optical distance measuring apparatus 1A described above includes a plurality of SPADs 4, a plurality of quench resistors 6 and pulse output units 8, a level detection circuit 20, an adder 40, a peak detection unit 45, and a response time correction unit And a light amount correction unit 57.

The plurality of SPADs 4 are configured to respond to the incidence of photons. The plurality of quench resistors 6 and the pulse output unit 8 are configured to output a pulse signal when the SPAD 4 responds to each of the plurality of SPADs 4. The level detection circuit 20 and the adder 40 are configured to detect the number of responses representing the number of SPADs 4 that are responding based on the pulse signal.

The peak detection unit 45 recognizes temporary timing based on the change state along the time series of the number of responses, and recognizes detection timing representing the timing at which the light ranging device 1A detects light according to the temporary timing. Configured to The response time correction unit 56 and the light amount correction unit 57 obtain a correction time representing a time difference between the temporary timing and the true timing corresponding to the distance to the object, and for the temporary timing, only the correction time It is configured to set the corrected timing as the detection timing.

According to such an optical distance measuring apparatus 1A, since the timing obtained by correcting the provisional timing by the correction time is recognized as the detection timing, the true timing and the provisional timing corresponding to the distance to the object are obtained. And the time difference between Therefore, the timing at which the SPAD 4 detects light can be accurately estimated.

(1b) In the above-described optical distance measuring apparatus 1A, the peak detection unit 45 is configured to recognize the timing at which the number of responses takes the maximum value as a temporary timing.
According to such an optical distance measuring apparatus 1A, since the timing when the number of responses reaches the maximum value may be set as the tentative timing, the tentative timing can be recognized by a simple process.

(1c) In the above-described light ranging apparatus 1A, the light quantity correction unit 57 is configured to calculate the correction time according to the light reception environment of the light ranging apparatus 1A.
According to such an optical distance measuring apparatus 1A, since the correction time is calculated according to the light receiving environment of the optical distance measuring apparatus 1A, when the light receiving environment changes, it is possible to cope with the change. Therefore, detection timing can be estimated more accurately.

(1d) In the above-described optical distance measuring apparatus 1A, the response time correction unit 56 calculates the correction time in consideration of the number of responses at temporary timing and the response continuation time representing the time for which the responding SPAD 4 continues the response. Configured to

According to such an optical distance measuring apparatus 1A, the correction time is calculated in consideration of the number of responses and the response continuation time, so that the light quantity for the optical distance measuring apparatus 1A and the characteristics of the SPAD 4 can be considered. . Therefore, detection timing can be estimated more accurately.

(1e) In the above-described light ranging apparatus 1A, the light quantity correction unit 57 is configured to calculate the correction time according to the intensity of light incident on the light ranging apparatus 1A. SPAD 4 saturates early when the light intensity becomes strong, and temporary timing tends to change, so correction is performed using this tendency.

According to such an optical distance measuring apparatus 1A, the correction time is calculated according to the intensity of the light incident on the light distance measuring apparatus 1A. Therefore, the correction time is calculated according to the change of the temporary timing. Can.
Therefore, detection timing can be estimated more accurately.

(1f) In the above-described optical distance measuring apparatus 1A, the level detection circuit 20 is configured as a clock synchronous circuit having a function of recognizing a pulse signal each time a clock input in a preset cycle is received.

According to such an optical distance measuring apparatus 1A, since the function of recognizing a pulse signal is realized by hardware called a clock synchronization circuit, the pulse signal can be recognized with a simple configuration as compared with the configuration using software. .

[2. Second embodiment]
[2-1. Differences from the First Embodiment]
Second Embodiment The basic configuration of the second embodiment is the same as that of the first embodiment, and the difference will be described below. The same reference numerals as those in the first embodiment denote the same components, and reference is made to the preceding description.

In the first embodiment described above, the correction time is determined using the maximum value of the level value. On the other hand, the optical distance measuring apparatus 1B of the second embodiment is different from the first embodiment in that the correction time is obtained using the offset value of the level value in addition to the maximum value of the level value.

[2-2. Constitution]
In the light ranging device 1B of the second embodiment, the light quantity correction unit 57 calculates the offset value Loff of the level value in addition to the maximum value Lmax of the level value, as shown in FIGS. The offset value Loff of the level value represents the number of SPADs 4 that constantly respond. In addition to the signal light to be received, the light receiving unit 2 receives light according to the ambient brightness as disturbance light, and a part of the SPAD 4 responds with the disturbance light.

The light quantity correction unit 57 recognizes an arbitrary value such as an average value or a median value of the number of SPADs 4 that respond in a period in which signal light is not emitted as the number of SPADs 4 that constantly respond, and this value as an offset value Loff. recognize.

The offset value Loff increases or decreases depending on the amount of disturbance light, and when there is little disturbance light, as shown in FIG. 9, the maximum value Lmax of the level value becomes larger than the offset value Loff. On the other hand, when there is much disturbance light, as shown in FIG. 10, the maximum value Lmax of the level value is smaller than the offset value Loff.

The light quantity correction unit 57 may set the correction time using a map in which the offset value Loff is also taken into consideration in addition to the maximum value Lmax of the level value, as shown in FIG. Here, when the offset value Loff occupied in the maximum value Lmax of the level value increases, the SPAD 4 tends to be saturated before the response due to the incident light starts, and thus the peak tends to occur earlier. Therefore, the light quantity correction unit 57 may adopt a map in which the correction amount decreases as the offset value Loff increases.

[2-3. effect]
According to the second embodiment described above, the effect (1a) of the first embodiment described above is exhibited, and further, the following effect is exhibited.

(2a) In the above-described optical distance measuring apparatus 1B, the response time correction unit 56 and the light amount correction unit 57 are configured to calculate the correction time in consideration of the offset value representing the number of regularly responding SPADs.

According to such an optical ranging device 1B, it is possible to recognize the intensity of incident light excluding disturbance light by adding the offset value. Then, the detection timing can be corrected according to the intensity of the incident light.

[3. Third embodiment]
3-1. Differences from the First Embodiment]
In the first embodiment described above, a fixed value is adopted as the correction time for correcting the temporary timing in accordance with the length of the response continuation time. On the other hand, the third embodiment is different from the first embodiment in that the correction time is varied according to the length of the response continuation time.

[3-2. Constitution]
In the optical distance measuring apparatus 1C according to the third embodiment, the computing unit 50C further includes a response time computing unit 58 as shown in FIG. 1 as a configuration of functions realized by the CPU 51 executing a program.

The function of the response time calculation unit 58 is configured to calculate the correction time according to the light reception environment of the light ranging device 1A. Here, the above-mentioned time difference ΔT1 tends to be larger as the response duration time of the SPAD 4 becomes longer. Therefore, in the function of the response time calculation unit 58, the correction time is varied according to the response continuation time of the SPAD 4 in the light reception environment.

More specifically, the function of the response time calculation unit 58 inputs a signal from at least one level detection circuit 20, and monitors whether or not a pulse signal is output from the level detection circuit 20. Then, the response continuation time of the monitoring target SPAD 4 is recognized by measuring the time from when the pulse signal is output until when it is not output.

Further, in the function of the response time calculation unit 58, a correction time according to the length of the measured response continuation time is set using a map as shown in FIG. In the map shown in FIG. 13, when the response duration time becomes long, the timing when the level value takes the maximum value is shifted to the long distance side, and a map is adopted in which the correction amount increases as the response duration time increases.

[3-3. effect]
According to the third embodiment described above, the effect (1a) of the first embodiment described above is exhibited, and further, the following effect is exhibited.

(3a) In the above-described optical distance measuring apparatus 1C, the response time calculation unit 58 measures the response continuation time for the SPAD 4 by monitoring whether or not the SPAD 4 is responding for at least one SPAD 4. Configured The response time correction unit 56 and the light amount correction unit 57 are configured to calculate the correction time in consideration of the response continuation time measured by the response time calculation unit 58.

According to such an optical distance measuring apparatus 1C, since the response continuation time is actually measured and the correction time is determined using this response continuation time, the accuracy of the correction can be improved. Therefore, detection timing can be estimated more accurately.

[4. Fourth embodiment]
[4-1. Differences from the Third Embodiment]
In the third embodiment described above, the response continuation time is actually measured to determine the correction time. On the other hand, the fourth embodiment is different from the third embodiment in that the response continuation time is estimated by temperature and the correction time is determined using the estimated response continuation time. The reason why the response duration time is estimated from the temperature in the present embodiment is that it is known that the SPAD 4 changes its response duration time according to the temperature change.

[4-2. Constitution]
An optical distance measuring apparatus 1D according to the fourth embodiment further includes a SPAD temperature detection unit 48, as shown in FIG. The SPAD temperature detection unit 48 is configured as a known temperature sensor that detects the temperature of the SPAD 4 or the temperature around the SPAD 4. The function as the light amount correction unit 57 of the calculation unit 50D corresponds to the SPAD temperature detection unit 48 using a previously prepared relational expression or map for specifying the relationship between the SPAD temperature detection unit 48 and the response continuation time. The response duration time is specified, and the correction time is calculated using the map shown in FIG. 13 described above.

[4-3. effect]
According to the fourth embodiment described above, the effect (1a) of the first embodiment described above is exhibited, and further, the following effect is exhibited.

(4a) In the above-described optical distance measuring apparatus 1C, the SPAD temperature detection unit 48 is configured to acquire the temperature of the SPAD 4 or the temperature around the SPAD 4 for at least one SPAD 4. The response time correction unit 56 and the light amount correction unit 57 are configured to calculate the response continuation time according to the temperature, and to calculate the correction time in consideration of the response continuation time.

According to such an optical distance measuring apparatus 1C, the temperature of the SPAD 4 or the temperature around it is obtained, and the response continuation time is calculated according to the temperature, so that the accuracy of the correction can be improved. Therefore, detection timing can be estimated more accurately.

[5. Fifth embodiment]
[5-1. Differences from the First Embodiment]
In the first embodiment described above, the correction time ΔT1 is determined according to the number of responses of SPAD2.
On the other hand, the fifth embodiment is different from the first embodiment in that the correction time ΔT1 is determined according to the degree of saturation of SPAD2.

5-2. Constitution]
The light amount correction unit 57 of the fifth embodiment determines the correction time ΔT1 according to the saturation of the SPAD 2 as shown in FIG.

The degree of saturation of SPAD2 indicates the ratio of the number of SPAD2 responses to the total number of SPAD2. For example, in the example of the timing [C] in FIG. 5, the total number of SPAD2s is 16 and the number of SPADs 2 that respond is 15, so the degree of saturation is about 94%.

The relationship between the degree of saturation of the SPAD 2 and the correction time is set so that the correction time decreases as the degree of saturation increases, as shown in the graph of FIG. The tendency in this graph is almost the same as the relationship between the number of responses of SPAD 2 and the correction time shown in FIG.

5-3. effect]
According to the fifth embodiment described above, the effect (1a) of the first embodiment described above is exhibited, and further, the following effect is exhibited.

(5a) The light quantity correction unit 57 according to the fifth embodiment calculates the correction time in consideration of the response rate to the total number of SPADs.
According to such a configuration, not only the amount of incident light but also the ratio to the number of SPADs is taken into consideration, a system in which the number of SPADs in a pixel dynamically changes, or a system in which pixels of different SPAD numbers coexist However, the same correction time can be adopted without changing the correction time according to the total number of SPADs.

[6. Sixth embodiment]
6-1. Differences from the First Embodiment]
In the first embodiment described above, the tentative timing is determined based on the number of responses of the SPAD 2 obtained by the one-time light wave irradiation. On the other hand, the sixth embodiment is different from the first embodiment in that the number of responses of the SPAD 2 obtained by irradiation of light waves a plurality of times is integrated, and a provisional timing is determined based on this value.

6-2. Constitution]
The peak detection unit 45 of the sixth embodiment recognizes a change in the number of responses along the time series each time the irradiation unit 3 irradiates a light wave. For example, as shown in FIG. 16, for the irradiation of light waves for an arbitrary number of times including the latest irradiation, the relationship between the time from the time of irradiation of the light waves and the number of responses is acquired as data indicating a change state. Here, data indicating the change state for the past three times is acquired.

Note that data indicating a change state in the past is recorded in any memory. For example, data indicating a change state is stored in the memory 52 of the arithmetic unit 50 and obtained from the memory 52.

The peak detection unit 45 integrates the number of responses for each time after each light wave is irradiated on data indicating a change state in the past, and obtains an integrated change state which is data after the integration. The integrated change state is obtained by simply integrating the number of responses for three times, as shown in the second diagram from the bottom of FIG.

Subsequently, the peak detection unit 45 divides the integrated change state by the number of integrations, here three times, and determines the position of the peak from the number of responses or the saturation based on the integrated change state after division. To recognize the tentative timing.

6-3. effect]
According to the sixth embodiment described above, the effect (1a) of the first embodiment described above is exhibited, and further, the following effect is exhibited.

(6a) The peak detection unit 45 recognizes the change state along the time series of the number of responses every time the irradiation unit 3 irradiates the light waves, and integrates the number of responses for each time after each light wave is irradiated The temporary timing is recognized based on the change state.

According to such a configuration, since the number of responses can be smoothed, noise resistance can be improved.
[7. Other embodiments]
As mentioned above, although embodiment of this indication was described, this indication can be variously deformed and implemented, without being limited to the above-mentioned embodiment.

(7a) In the above embodiment, the configuration for obtaining the correction time is realized as software processing, and the configuration of the peak detection unit 45 is realized as hardware, but the present invention is not limited to this. For example, the configuration for obtaining the correction time and the configuration of the peak detection unit 45 may be implemented as software processing, hardware, or a combination thereof.

(7b) The plurality of functions of one component in the above embodiment may be realized by a plurality of components, or one function of one component may be realized by a plurality of components . Also, a plurality of functions possessed by a plurality of components may be realized by one component, or one function realized by a plurality of components may be realized by one component. In addition, part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above-described embodiment may be added to or replaced with the configuration of the other above-described embodiment. In addition, all the aspects contained in the technical thought specified from the wording described in the claim are an embodiment of this indication.

(7c) A system including the

light ranging devices

1A, 1B, 1C, and 1D in addition to the

light ranging devices

1A, 1B, 1C, and 1D described above, the

light ranging devices

1A, 1B, 1C, and 1D. The present disclosure can be realized in various forms such as a program for causing a computer to function as a part of the configuration, a non-transitional real recording medium such as a semiconductor memory storing the program, a light detection method, and the like.

[8. Correspondence between the configuration of the embodiment and the configuration of the present disclosure]
In the above embodiment, the quench resistor 6 and the pulse output unit 8 correspond to the signal output unit in the present disclosure, and in the above embodiment, the level detection circuit 20 and the adder 40 correspond to the response number detection unit in the present disclosure. Further, in the above embodiment, the peak detection unit 45 corresponds to the timing recognition unit in the present disclosure, and in the above embodiment, the SPAD temperature detection unit 48 corresponds to the temperature acquisition unit in the present disclosure.

Further, in the above embodiment, the response time correction unit 56 and the light amount correction unit 57 correspond to a timing correction unit and a correction operation unit in the present disclosure, and in the above embodiment, the response time calculation unit 58 is a response measurement unit in the present disclosure. Equivalent to. Further, in the above embodiment, the level detection circuit 70 corresponds to a clock synchronization circuit as referred to in the present disclosure.

Claims

An optical distance measuring apparatus (1A, 1B, 1C, 1D) which measures a distance from a round trip time of light to an object,
An irradiation unit (3) for irradiating a light wave to an area where an object is to be detected;
A plurality of SPADs (4) configured to respond to the incidence of photons including the reflected waves of the lightwaves;
A plurality of signal output units (6, 8) configured to output a pulse signal when the SPAD responds to the plurality of SPADs;
A response number detection unit (20, 40) configured to detect the number of responses representing the number of SPADs that are responding based on the pulse signal;
The timing at which the optical distance measuring device detects light according to the tentative timing, recognizing the tentative timing that satisfies the preset condition based on the chronological change of the number of responses. A timing recognition unit (45) configured to recognize a detection timing representing
A correction time representing a time difference between the provisional timing and the true timing corresponding to the distance to the object is acquired, and the timing corrected by the correction time with respect to the provisional timing is used as the detection timing. A timing correction unit (56, 57) configured to set;
Light range finder equipped with
The optical distance measuring apparatus according to claim 1, wherein
The optical distance measuring apparatus, wherein the timing recognition unit recognizes the timing at which the number of responses takes a maximum value as the temporary timing.
The optical distance measuring apparatus according to claim 1 or 2, wherein
A correction operation unit (56, 57) configured to calculate the correction time according to the light reception environment of the light ranging device;
Optical ranging device further equipped with
The optical distance measuring apparatus according to claim 3, wherein
A light distance measuring apparatus, wherein the correction operation unit is configured to calculate the correction time according to the intensity of light incident on the light distance measuring device.
The optical distance measuring apparatus according to claim 3 or 4, wherein
The optical distance measuring apparatus, wherein the correction calculation unit calculates the correction time in consideration of a response rate to the total number of the SPADs.
The optical distance measuring apparatus according to any one of claims 3 to 5, wherein
The optical distance measuring apparatus, wherein the correction calculation unit calculates the correction time in consideration of an offset value representing the number of regularly responding SPADs.
The optical distance measuring apparatus according to any one of claims 3 to 6, wherein
The light ranging configured to calculate the correction time in consideration of the number of responses at the temporary timing, and a response continuation time representing a time for which a response SPAD continues a response. apparatus.
The optical distance measuring apparatus according to claim 7, wherein
A response measuring unit (58) configured to measure the response continuation time for the SPAD by monitoring whether or not the SPAD is responding for at least one SPAD;
And further
The optical distance measuring apparatus, wherein the correction calculation unit calculates the correction time in consideration of the response duration time measured by the response measurement unit.
The optical distance measuring apparatus according to claim 7, wherein
A temperature acquisition unit (48) configured to acquire the temperature of the SPAD or the temperature around the SPAD for at least one SPAD;
And further
The optical distance measuring apparatus, wherein the correction calculation unit calculates the response continuation time according to the temperature, and calculates the correction time in consideration of the response continuation time.
The optical distance measuring apparatus according to any one of claims 1 to 9, wherein
The timing recognition unit recognizes a change state along the time series of the response number each time the irradiation unit irradiates a light wave, and integrates change of the response number for each time after each light wave is irradiated. An optical ranging device configured to recognize the temporary timing based on a state.