WO2021124762A1 - Light receiving device, method for controlling light receiving device, and distance measuring device - Google Patents

Abstract

A light receiving device of the present disclosure comprises: an optical sensor; a time measurement unit; and a system control unit. The optical sensor receives continuously reflected pulse light from a distance measurement object, the continuously reflected pulse light based on the projection of continuously emitted pulse light from a light source unit. The time measurement unit generates, on the basis of the output pulse of the optical sensor, a histogram of reflected light events which are based on reflected light from the distance measurement object. On the basis of the histogram generated by the time measurement unit, the system control unit estimates the timing at which the reflected light events are generated, and on the basis of the estimation results, performs feedback control with respect to distance measurement-related characteristics.

Description

Light receiving device, control method of light receiving device, and distance measuring device

The present disclosure relates to a light receiving device, a control method of the light receiving device, and a distance measuring device.

As a light receiving element, there is a light receiving device using an element that generates a signal in response to the light reception of a photon. In a distance measuring device equipped with this type of light receiving device, the light emitted from the light source toward the distance measuring object is reflected by the distance measuring object as a measurement method for measuring the distance to the distance measuring object (subject). The ToF (Time of Flight) method is used to measure the time it takes to return.

In the conventional distance measuring device using the ToF method, in order to improve the distance accuracy, the distance measuring operation is repeatedly executed and a histogram of the light receiving element output is generated to statistically improve the S / N. ing. However, in the case of this conventional method, a large amount of memory is required to stack a large number of histograms. Therefore, by emitting a continuous pulse train from the light source and calculating the estimated distance from the result of accumulating the responses obtained from the reflected light, it is not necessary to stack a large number of histograms, and the amount of memory is reduced. (See, for example, Patent Document 1).

JP-A-2017-125844

Although the prior art described in Patent Document 1 does not require the stacking of a large number of histograms and can reduce the amount of memory, the estimated value of the distance is calculated from the cumulative result of the response obtained from the reflected light. Therefore, a process for estimating the distance is required, and it takes time to measure the distance accordingly.

The present disclosure is a light receiving device capable of estimating the timing of a reflected light event based on the reflected light from a distance measuring object during one histogram generation, and realizing distance measurement with dynamic feedback in a short time. It is an object of the present invention to provide a control method of a light receiving device and a distance measuring device having the light receiving device.

The first light receiving device of the present disclosure for achieving the above object is
Optical sensor,
Time measurement unit and
System control unit,
With
The optical sensor receives the continuously reflected pulsed light from the distance measurement object based on the irradiation of the continuously emitted pulsed light from the light source unit.
The time measurement unit generates a histogram of the reflected light event based on the reflected light from the distance measurement object based on the output pulse of the optical sensor.
The system control unit estimates the occurrence timing of the reflected light event based on the histogram generated by the time measurement unit, and feedback-controls the characteristics related to distance measurement based on the estimation result.

The control method of the light receiving device of the present disclosure for achieving the above object is described.
An optical sensor that receives continuously reflected pulsed light from a distance measuring object based on irradiation of continuously emitted pulsed light from a light source unit.
In controlling the light receiving device equipped with
Based on the output pulse of the optical sensor, generate a histogram of the reflected light event based on the reflected light from the distance measurement object.
Based on the generated histogram, the occurrence timing of the reflected light event is estimated, and feedback control is performed on the characteristics related to distance measurement based on the estimation result.

The second light receiving device of the present disclosure for achieving the above object is
Optical sensor,
Low pass filter,
Comparator and
Time measurement unit,
With
The optical sensor receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit, and receives the continuously reflected pulsed light.
The low-pass filter waveform-shapes the output pulse of the optical sensor to generate a histogram of reflected light events based on the reflected light from the distance-finding object.
The comparator compares the histogram generated by the low-pass filter with the distance measurement target judgment threshold value, and outputs a pulse whose pulse width is from the distance measurement start timing to the timing when the histogram exceeds the distance measurement target judgment threshold value.
The time measurement unit consists of a delta-sigma type time measurement unit that uses delta-sigma modulation technology, receives the output pulse of the comparator as an input, and feeds back the measurement result to the input.

The first ranging device of the present disclosure for achieving the above object has a configuration having the first light receiving device having the above configuration, and the second ranging device of the present disclosure has the second structure described above. It is configured to have a light receiving device.

FIG. 1 is a schematic configuration diagram showing an example of a distance measuring device to which the technique according to the present disclosure is applied. 2A and 2B are block diagrams showing an example of a specific configuration of the distance measuring device according to this application example. FIG. 3 is a circuit diagram showing an example of a basic pixel circuit using a SPAD element. FIG. 4A is a characteristic diagram showing the current-voltage characteristics of the PN junction of the SPAD element, and FIG. 4B is a waveform diagram provided for explaining the circuit operation of the pixel circuit. FIG. 5 is a diagram illustrating a method of repeatedly executing the distance measuring operation to generate a histogram. FIG. 6 is a diagram illustrating a light source unit that irradiates continuous pulsed light by using a plurality of laser light sources A to X and providing a time difference between the respective light emission timings. FIG. 7 is a block diagram showing an example of the configuration of the light receiving device according to the embodiment of the present disclosure. FIG. 8 is a timing waveform diagram illustrating control of the time measuring unit according to the first embodiment. FIG. 9 is a flowchart showing a processing flow of the control method of the light receiving device according to the embodiment of the present disclosure. FIG. 10 is a diagram for explaining the time resolution switching according to the first embodiment. FIG. 11 is a diagram for explaining the time resolution switching according to the second embodiment. FIG. 12 is a diagram for explaining the time resolution switching according to the specific example 3. FIG. 13 is a block diagram showing an example of the configuration of the light receiving device according to the second embodiment. 14A and 14B are diagrams for explaining an example in which a readout region due to continuous light emission and a readout region due to normal light emission are mixed in the pixel region of the optical sensor in the light receiving device according to the second embodiment. FIG. 15 is a diagram illustrating a modified example of the second embodiment. FIG. 16 is a block diagram showing an example of the configuration of the light receiving device according to the third embodiment. FIG. 17 is a timing waveform diagram showing signal waveforms of each part of the light receiving device according to the third embodiment. FIG. 18 is a circuit diagram for explaining an actual operation example of the time measuring unit including ΔΣTDC. FIG. 19 is a timing waveform diagram showing signal waveforms of each part of the circuit of FIG. FIG. 20A is a circuit diagram showing the basic configuration of the ΔΣ modulator, and FIG. 20B is a diagram modeling the basic configuration in the Z region. FIG. 21 is a diagram illustrating a difference in the distribution of quantization noise depending on the presence or absence of noise shaping. FIG. 22 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile control system to which the technique according to the present disclosure can be applied. FIG. 23 is a diagram showing an example of an installation position of the distance measuring device.

Hereinafter, embodiments for carrying out the technique according to the present disclosure (hereinafter, referred to as “embodiments”) will be described in detail with reference to the drawings. The technique according to the present disclosure is not limited to the embodiment. In the following description, the same reference numerals will be used for the same elements or elements having the same function, and duplicate description will be omitted. The explanation will be given in the following order.
1. 1. Description of the light receiving device of the present disclosure, the distance measuring device, its control method, and the general description 2. Distance measuring device to which the technology according to the present disclosure is applied 2-1. Specific configuration example of distance measuring device 2-2. Example of a basic pixel circuit using a SPAD element 2-3. Circuit operation example of a pixel circuit using a SPAD element 2-4. Regarding the generation of the histogram of the SPAD output 3. Embodiments of the present disclosure 3-1. Example 1 (Example of feeding back the distance measurement result to the time measurement unit)
3-2. Example 2 (Example of feeding back the distance measurement result to the optical sensor)
3-3. Example 3 (Example of feeding back the measurement result of the ΔΣ type time measurement unit to the input)
4. Modification example 5. Application example of the technology according to the present disclosure (example of mobile body)
6. Configuration that can be taken by this disclosure

<Explanation of the light receiving device and the ranging device of the present disclosure, in general>
In the first light receiving device and the first ranging device of the present disclosure, the timing at which the histogram generated by the time measuring unit exceeds a predetermined threshold value is estimated as the occurrence timing of the reflected light event for the system control unit. , The time resolution of the time measuring unit can be controlled based on the estimation result.

In the first light receiving device and the first distance measuring device of the present disclosure including the above-described preferable configuration, the system control unit is of the time measuring unit by changing the sampling frequency for sampling the output pulse of the light receiving element of the optical sensor. The time resolution can be switched. Further, regarding the system control unit, the time resolution of the time measurement unit is switched from a relatively coarse time resolution to a relatively fine time resolution at the timing when the histogram generated by the time measurement unit exceeds a predetermined threshold value. can do.

Alternatively, in the first light receiving device and the first ranging device of the present disclosure including the above-mentioned preferable configuration, the timing at which the histogram generated by the time measuring unit exceeds a predetermined threshold value is set for the system control unit. It can be estimated as the occurrence timing of the reflected light event, and the readout area in the pixel area of the optical sensor can be controlled based on the estimation result.

Further, in the first light receiving device and the first ranging device of the present disclosure including the above-described preferable configuration, the pixel area of the optical sensor includes a first readout area corresponding to a continuous light emitting area on the light source side. It is possible to have a configuration in which a second readout region corresponding to a normal light emitting region having a period longer than that of continuous light emission on the light source unit side is mixed. In this case, the system control unit may be configured to perform a process of estimating the occurrence timing of the reflected light event based on the histogram generated by the time measurement unit in the first read region.

Further, in the first light receiving device and the first ranging device of the present disclosure including the above-mentioned preferable configuration, the light receiving element of the optical sensor is composed of an element that generates a signal in response to the light reception of a photon, preferably. , Can be configured to consist of a single photon avalanche diode.

Further, in the first ranging device of the present disclosure including the above-mentioned preferable configuration, the light source unit is composed of a surface-emitting semiconductor laser in which light sources are two-dimensionally arranged in an array, preferably a surface-emitting semiconductor laser. , It can be configured to be a vertical resonator type surface emitting laser. The light emitting region of the light source unit may include a continuous light emitting region in which the light source continuously emits light and a normal light emitting region in which the light source emits light in a cycle longer than the continuous light emitting cycle. ..

Further, in the first ranging device of the present disclosure including the above-described preferable configuration, the pixel region of the optical sensor includes a first readout region corresponding to a continuous light emitting region on the light source portion side and a normal light emitting region on the light source portion side. The configuration can be set with a second read area corresponding to the area. At this time, the system control unit may be configured to perform a process of estimating the occurrence timing of the reflected light event for the first read region.

In the second light receiving device and the second ranging device of the present disclosure, the time measuring unit has a subtractor that takes a signal difference, an adder that performs time integration for the output of the subtractor, and a quantization for the output of the integrator. It can be configured to consist of a comparator that performs the above and a digital-analog converter that feeds back the output of the comparator as a subtraction input of the subtractor.

Further, in the second light receiving device and the second ranging device of the present disclosure including the above-mentioned preferable configuration, the light receiving element of the optical sensor is an element that generates a signal in response to the light reception of a photon, preferably a single element. It can be configured to consist of a photon avalanche diode.

<Distance measuring device to which the technology according to the present disclosure is applied>
FIG. 1 is a schematic configuration diagram showing an example of a distance measuring device to which the technique according to the present disclosure is applied. The distance measuring device 1 according to this application example has a peak wavelength in the infrared wavelength region as a measuring method for measuring the distance to the subject 10 which is the object to be measured. The ToF method is adopted, in which the flight time until the laser beam) is reflected by the subject 10 and returns is measured. In order to realize the distance measurement by the ToF method, the distance measuring device 1 according to this application example includes a light source unit 20 and a light receiving device 30. Then, as the light receiving device 30, the light receiving device according to the embodiment of the present disclosure described later can be used.

[Specific configuration example of distance measuring device]
An example of a specific configuration of the distance measuring device 1 according to this application example is shown in FIGS. 2A and 2B. The light source unit 20 has, for example, a laser drive unit 21, a laser light source 22, and a diffusion lens 23, and irradiates the subject 10 with a laser beam. The laser drive unit 21 drives the laser light source 22 under the control of the system control unit 40. The laser light source 22 is composed of, for example, a semiconductor laser, and emits laser light by being driven by the laser driving unit 21. The diffusing lens 23 diffuses the laser light emitted from the laser light source 22 and irradiates the subject 10 which is a distance measuring object.

The light receiving device 30 includes a light receiving lens 31, an optical sensor 32 which is a light receiving unit, and a signal processing unit 33, and receives the reflected laser light which is reflected by the subject 10 and returned from the irradiation laser light from the light source unit 20. To do. The light receiving lens 31 collects the reflected laser light from the subject 10 on the light receiving surface of the light sensor 32. The optical sensor 32 receives the reflected laser light from the subject 10 that has passed through the light receiving lens 31 in pixel units and performs photoelectric conversion. As the optical sensor 32, a two-dimensional array sensor in which pixels including a light receiving element are two-dimensionally arranged in a matrix (array) can be used.

The output signal of the optical sensor 32 is supplied to the system control unit 40 via the signal processing unit 33. The system control unit 40 is, for example, an application processor composed of a CPU (Central Processing Unit) or the like, controls the light source unit 20 and the light receiving device 30, and irradiates the subject 10 from the light source unit 20. The time required for the laser beam to be reflected by the subject 10 and returned is measured. Based on this measured time, the distance to the subject 10 can be obtained.

Then, in the distance measuring device 1 according to the present application example, as the optical sensor 32, the light receiving element of the pixel is an element that generates a signal in response to the light receiving of a photon, for example, SPAD (Single Photon Avalanche Diode). ) A sensor consisting of elements is used. That is, the light receiving device 30 in the distance measuring device 1 according to this application example has a configuration in which a SPAD element is used as the light receiving element of the pixel. The SPAD element operates in a Geiger mode in which the element is operated with a reverse voltage exceeding the breakdown voltage (yield voltage). The pixel light receiving element is not limited to the SPAD element, and various elements operating in the Geiger mode such as APD (avalanche photodiode) and SiPM (silicon photomultiplier) can be used.

[Example of basic pixel circuit using SPAD element]
FIG. 3 shows an example of the configuration of a basic pixel circuit in the light receiving device 30 using the SPAD element. Here, the basic configuration for one pixel is illustrated.

The basic pixel circuit of the pixel 50 with SPAD devices, the cathode electrode of the SPAD device 51, for example through a load 54 composed of P-type MOS transistor Q _L, is connected to a terminal 52 of the power supply voltage V _DD is applied , The anode electrode of the SPARC element 51 is connected to the terminal 53 to _{which the anode voltage Vano is applied.} As the anode voltage _Vano , a large negative voltage that causes avalanche multiplication is applied (see FIG. 4B). The gate electrode of the P-type MOS transistor Q _L, the bias voltage V _bias to operate the MOS transistor Q _L as the desired current source is applied.

Then, the cathode voltage V _CA of the MOSFET element 51 is derived as a MOSFET output (pixel output) via the CMOS inverter 55 composed of the P-type MOS transistor Q _p and the N-type MOS transistor Q _n. The CMOS inverter 55 can be said to be a comparison circuit (comparator) using _{the threshold voltage V th} as a comparison reference, and a waveform that shapes the waveform _{of the cathode voltage V CA} which is the output of the SPAD element 51 based _{on the threshold voltage V th.} It can also be called a shaping circuit.

A voltage equal to or higher than the breakdown voltage V _{BD is applied to the SPAD element 51.} An excess voltage above the breakdown voltage V _BD is called the _{excess bias voltage V EX.} Breakdown voltage The characteristics of the SPAD element 51 change depending on how large the excess bias voltage V _{EX is applied with respect to the voltage value of the BD.}

The I (current) -V (voltage) characteristics of the PN junction of the SPAD element 51 operating in the Geiger mode are shown in FIG. 4A. FIG. 4A _{illustrates the relationship between the breakdown voltage V BD} , the excess bias voltage V _EX , and the operating points of the SPAD element 51.

[Circuit operation example of a pixel circuit using a SPAD element]
Subsequently, an example of the circuit operation of the pixel circuit having the above configuration will be described with reference to the waveform diagram of FIG. 4B.

When no current is flowing through the SPAD element 51, a voltage having a value of _{(V DD −} V _{ano) is applied to the SPAD element 51.} This voltage value (V _{DD −} V _ano ) is (V _BD + V _EX ). Then, at the PN junction of the SPAD element 51, the dark electron generation rate DCR (Dark Count Rate) and the electrons generated by light irradiation cause an avalanche multiplication, and an avalanche current is generated.

When the cathode voltage V _CA drops and the voltage between the terminals of the SPAD element 51 _{becomes the breakdown voltage V BD} of the PN diode, the avalanche current stops. Then, the electrons generated and accumulated by the avalanche multiplication are discharged through the load 55 (for example, the P-type MOS transistor Q _L ), and the cathode voltage V _CA rises. Then, the cathode voltage V _CA recovers to the power supply voltage V _DD , and returns to the initial state again.

When light is incident on the SPAD element 51 and even one electron-hole pair is generated, it becomes a seed and an avalanche current is generated. Therefore, even if one photon is incident, a certain detection efficiency PDE (Photon Detection Efficiency) Can be detected with.

The above operation is repeated. Then, in this series of operations, the cathode voltage V _CA is waveform-shaped by the CMOS inverter 55, and the pulse signal having the pulse width T starting from the arrival time of one photon becomes the SPAD output (pixel output).

[Generation of Histogram of SPAD output]
In the conventional ranging device using the ToF method, it is necessary to estimate the place where the reflected light event (event based on the reflected light) occurs while the ambient light event (event based on the disturbance light) occurs. Here, the factors that cause the disturbance light event are dark (DC) generated when no light is incident, and afterpulse (AP) generated regardless of the incident light after the first pulsed light is generated. , Crosstalk due to the influence of the response of the adjacent SPAD element 51, ambient light, or the like can be exemplified.

Further, the SPAD element 51 is a high-performance device having extremely high sensitivity, and as shown in FIG. 5, since one pulse is generated (generated) for each event, an ambient light event and a reflected light event It is difficult to distinguish from. Therefore, in the conventional distance measuring device using the ToF method, the distance measuring operation is repeatedly executed, the time measured a plurality of times is accumulated to generate a histogram, and the count number by the reflected light is calculated from the count number of the disturbance light event. Statistically, the S / N is improved by using the time point at which it becomes superior as an estimated value.

However, in the case of the above-mentioned method, the distance measuring operation of irradiating one pulsed light at regular intervals and generating a histogram based on the reflected light is repeated a plurality of times. Therefore, it is not possible to estimate the time when the reflected light event occurs until a certain amount of time has passed from the start of distance measurement and the count number of the reflected light event becomes superior to the count number of the disturbance light event. As a result, in the conventional distance measuring device, it takes time to measure the distance, so that the distance measuring result can be fed back in real time to dynamically control the characteristics related to the distance measurement (for example, time resolution). Can not.

<Embodiment of the present disclosure>
In the embodiment of the present disclosure, in the distance measuring device 1 to which the technique according to the present disclosure is applied, which is shown in FIG. 2A, a plurality of distance measuring devices 1 are directed from the light source unit 20 toward the distance measuring object under the control of the system control unit 40. (Continuous emission pulsed light) is continuously irradiated (fired) in a short period of time.

The light source unit 20 that irradiates the continuously emitted pulsed light may have, for example, a configuration in which one general-purpose laser light source is used to blink and emit light, or a configuration in which a plurality of general-purpose laser light sources are used to sequentially emit light in a time-division manner. .. In the latter case, for example, as shown in FIG. 6, a plurality of laser light sources A to X are used to irradiate continuous emission pulsed light by giving a time difference to each emission timing, that is, by shifting the emission timing. Can be done. Further, as the light source unit 20, a surface emitting semiconductor laser (VCSEL: Vertical Cavity Surface Emitting Laser) in which light sources are arranged in an array (matrix) in two dimensions is used to emit light. It is also possible to have a configuration in which there is a time difference in the light emission timing of the unit.

By continuously irradiating a plurality of pulsed lights from the light source unit 20 in a short time, that is, by irradiating continuously emitted pulsed light, light receiving light that receives reflected light (continuous pulsed light) from a distance measuring object based on the irradiation. In the device 30, since the count number of reflected light events acquired by one histogram generation increases, it is superior to the count number of disturbance light events.

In this way, while the light source unit 20 continuously irradiates a plurality of pulsed lights in a short time, the light receiving device 30 receives the reflected light based on the irradiation and generates a histogram once. The count number of reflected light events acquired by histogram generation increases, which is superior to the count number of disturbance light events. This makes it possible to estimate the location where the reflected light event is likely to occur by generating the histogram once.

As a result, it is possible to estimate the occurrence timing (occurrence location) of the reflected light event during one histogram generation based on the irradiation of the continuous emission pulse light without executing the histogram generation multiple times. , The distance measurement time can be shortened as compared with the case where the histogram generation is executed a plurality of times. Then, since the distance measurement time can be shortened, the distance measurement result can be fed back in real time, and the characteristics related to the distance measurement such as the time resolution can be dynamically controlled.

FIG. 7 shows an example of the configuration of the light receiving device 30 according to the embodiment of the present disclosure. In the light receiving device 30 according to the present embodiment, as the optical sensor 32, an array sensor in which a plurality of pixels 40 including the SPAD element 51 are two-dimensionally arranged in a matrix (array) is used. In the optical sensor 32, the continuously emitted pulsed light emitted from the light source unit 20 toward the distance measuring object is reflected by the distance measuring object and returned as pulsed light (hereinafter, referred to as “continuously reflected pulse light”). (May be) to receive light.

The light receiving device 30 according to the present embodiment includes a signal processing unit 33 and a control circuit 34 in addition to the optical sensor 32. Each light receiving data of the plurality of pixels 40 in the optical sensor 32 is supplied to the signal processing unit 33. The control circuit 34 controls the signal processing unit 33 based on a trigger signal or the like given from the outside.

The signal processing unit 33 has, for example, a time-to-digital converter (TDC) 330, and each received light data output from the plurality of pixels 40 under the control of the control circuit 34. Is signal processed for distance measurement.

Specifically, the time measuring unit 330 uses, for example, the direct ToF method of calculating the distance directly from the flight time of light, and performs signal processing for distance measurement based on the received light data output from the pixel 40. .. That is, the time measuring unit 330 measures the time until the light emitted from the light source unit 20 toward the distance measuring object is reflected by the distance measuring object and returned.

In the light receiving device 30 according to the present embodiment, the continuously emitted pulsed light emitted from the light source unit 20 toward the distance measuring object in a short time is reflected by the distance measuring object and returned as reflected pulse light (continuous reflection). Receives pulsed light). Then, in the light receiving device 30, the time measuring unit 330 executes a histogram generation for the reflected light event once based on the received continuous reflected pulse light, and outputs the data related to the generated histogram to the system control unit 40 (see FIG. 2A). ). The system control unit 40 calculates the distance corresponding to the occurrence timing (occurrence location) of the reflected light event as the distance to the distance measurement target based on the data related to the histogram acquired from the time measurement unit 330.

In this way, by continuously irradiating a plurality of pulsed lights from the light source unit 20 in a short time, it is possible to estimate the occurrence timing (code) of the reflected light event during one histogram generation. , The distance measurement time can be shortened. Then, since the distance measurement time can be shortened, the distance measurement result can be fed back in real time, and the characteristics related to the distance measurement such as the time resolution can be dynamically controlled.

The following is a specific embodiment of the present embodiment, that is, a specific example for executing distance measurement in a short time, feeding back the distance measurement result in real time, and dynamically controlling characteristics related to distance measurement. Examples will be described.

[Example 1]
The first embodiment is an example in which the distance measurement result based on the acquired histogram is fed back to the time measurement unit 330 to control the time resolution of the time measurement unit 330, which is an example of the characteristics related to the distance measurement. FIG. 8 shows a timing waveform diagram illustrating the control of the time measuring unit 330 according to the first embodiment.

FIG. 8 shows the timing relationship between the continuous emission pulse light, the SPAD output pulse, and the synchronous clock, and the waveform of the moving average histogram. The continuously emitted pulsed light is pulsed light that is continuously emitted from the light source unit 20 in a short time. Here, for simplification, for example, five pulsed lights from the X point to the X'point are illustrated. ing. The SPAD output pulse is an output pulse of the SPAD element 51 that receives the continuously reflected pulse light from the distance measuring object based on the continuous emission pulse light, and the synchronous clock is a clock synchronized with the sampling timing. The moving average histogram is a histogram obtained by smoothing the time series data of the output of the SPAD element 51.

The time measurement unit (TDC) 330 has a configuration in which the time resolution can be switched by changing the sampling frequency for sampling the output pulse of the SPAD element 51, for example, a relatively coarse time resolution and a relatively fine time resolution. The configuration is switchable. In order to switch the time resolution, as shown in FIG. 8, a TDC operation threshold value is set for the moving average histogram. When the moving average histogram exceeds the TDC operation threshold, the time resolution of the time measuring unit 330 changes from a relatively coarse time resolution based on a relatively low sampling frequency to a relatively fine time based on a relatively high sampling frequency. Switch to resolution. The time resolution is the resolution at which the rising timing of the SPAD output pulse is acquired.

By increasing the density of the continuously emitted pulsed light in response to the disturbance light event, the moving average amount of the histogram to be acquired increases when responding by the continuously emitted pulsed light. Therefore, the TDC operation threshold can be estimated from the density of the continuously emitted pulsed light with respect to the moving average amount of the histogram. It is also possible to set a TDC operation threshold value estimated from the density of the continuously emitted pulsed light so that the time measurement unit 330 operates with a fine time resolution when the TDC operation threshold value is exceeded.

As described above, in the time measurement unit 330 according to the first embodiment, the SPAD output corresponding to the reception of the continuously reflected pulse light from the distance measuring object by the irradiation of the continuous emission pulse light from the light source unit 20 in a short time. Generate a histogram once based on the pulse. Then, the occurrence timing of the reflected light event is estimated by generating the histogram once, and the estimation result is fed back to the time measurement unit 330 (see FIG. 7). Specifically, when the histogram generated once exceeds the TDC operation threshold value, the time resolution of the time measuring unit 330 is switched from the coarse time resolution to the fine time resolution. As a result, the dynamic feedback control enables distance measurement with fine resolution only in the vicinity of the distance measurement object.

Note that one histogram generation is performed by the time measurement unit 330, and the estimation of the occurrence timing of the reflected light event based on one histogram generation is performed by the system control unit 40. Then, the estimation result of the occurrence timing of the reflected light event is fed back from the system control unit 40 to the time measurement unit 330, and the time resolution is switched.

Subsequently, the processing flow of the control method of the light receiving device 30 according to the present embodiment will be described with reference to the flowchart of FIG.

The optical sensor 32 receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit 20 in a short time (step S11). Next, the time measurement unit 330 receives the SPAD output pulse from the optical sensor 32 in response to the reception of the continuously reflected pulse light by the optical sensor 32, generates a histogram once based on the SPAD output pulse, and generates a histogram once, and the system control unit 330. Supply to 40 (step S12).

The system control unit 40 receives a histogram generated once from the time measurement unit 330, estimates the occurrence timing of the reflected light event based on the histogram generation (step S13), and measures the distance to the time measurement unit 330. Feedback control is performed for the characteristic (in this example, the time resolution) related to the above (step S14). The characteristics related to distance measurement are not limited to the time resolution, and may be a readout region in the pixel region of the optical sensor 32 as in the case of the second embodiment described later.

The processing flow shown in the flowchart of FIG. 9 is an example and is not limited to this. For example, for the processing after step S12, it is possible to use a processing flow in which feedback control is performed before the histogram is completely generated. Specifically, it is also possible to generate a histogram and change the time resolution when the moving average exceeds a certain threshold value.

Next, a method of switching the time resolution of the time measurement unit 330 will be described with a specific example. In the following, a case where the time resolution is switched to two stages will be described, but the case is not limited to the two stages.

(Specific example 1 of time resolution switching)
FIG. 10 is a diagram (timing waveform diagram) for explaining a specific example 1 for switching the time resolution of the time measuring unit 330. FIG. 10 shows the timing relationship between the SPAD output pulse and the sampling timing.

In Specific Example 1, the time measuring unit 330 switches the sampling frequency from a relatively low frequency (for example, 1 GHz) to a relatively high frequency (for example, 16 GHz) under feedback control from the system control unit 40. To do so. By switching the sampling frequency from a low frequency to a high frequency in this way, it is possible to improve the time resolution when the time measuring unit 330 acquires the rising timing of the SPAD output pulse.

(Specific example 2 of time resolution switching)
FIG. 11 is a diagram for explaining a specific example 2 for switching the time resolution of the time measuring unit 330.

In Specific Example 2, two types of the time measurement unit 330 _{are used: the time measurement unit 330 _11} having a coarse resolution and the time measurement unit 330 _{_12 having a fine resolution.} Then, under the feedback control from the system control unit 40, the resolution is coarse time measurement unit 330 _{_11,} resolution is to switch to the fine time measurement unit 330 _{_12.} Thus, the resolution is coarse time measurement unit 330 _{_11,} by switching the resolution is fine time measurement unit 330 _{_12,} in the time measuring unit 330, improving the time resolution in acquiring rise timing of the SPAD output pulse Can be done.

(Specific example 3 of time resolution switching)
FIG. 12 is a diagram for explaining a specific example 3 for switching the time resolution of the time measuring unit 330.

In Specific Example 3, the time measuring unit (TDC) 330 is a two-stage TDC (pipeline TDC). Specifically, the time measuring unit 330 is _{configured by connecting two time measuring units 330 _21} and a time measuring unit 330 _{_22} having coarse resolution in series with a time amplifier 331 of gain A interposed therebetween. Under feedback control from the system control unit 40, the rise timing of the SPAD output pulse is acquired using only _{the time measurement unit 330 _21 of the first stage, or the time measurement unit 330 _21} of the first stage and the time of the second stage. The measurement unit 330 _{_22} is used to switch whether to acquire the rise timing of the SPAD output pulse.

In the case of the specific example 3, as in the case of the specific example 1 and the specific example 2, the time resolution at the time of acquiring the rising timing of the SPAD output pulse can be improved in the time measuring unit 330. Note that the error in obtaining the rise timing of the SPAD output pulse with a time of the first stage measuring 330 _{_21} and 2-stage time measurement unit 330 _{_22,} error after amplification time amplifier 331 of gain A Therefore, the effect of the error is minute (1 / A).

[Example 2]
The second embodiment is an example in which the distance measurement result based on the acquired histogram is fed back to the time measurement unit 330 to control the read region in the pixel region of the optical sensor 32, which is an example of the characteristics related to the distance measurement. FIG. 13 shows an example of the configuration of the light receiving device 30 according to the second embodiment.

When, for example, a surface emitting semiconductor laser in which light sources are arranged two-dimensionally in an array, for example, a vertical cavity type surface emitting laser (VCSEL) is used as the light source unit 20, the light emitting unit (light source) is partially emitted. It is possible. As a result, for example, in the distance measuring device 1 that uses the vertical resonator type surface emitting laser as the light source unit 20, the light emitting region of the vertical resonator type surface emitting laser is a continuous light emitting region that continuously emits light in a short time and a continuous light emitting region. It is possible to provide a normal light emitting region in which light is emitted in a cycle longer than the cycle in which light is emitted. In other words, the continuous light emitting region and the normal light emitting region can be mixed in the light emitting region of the vertical resonator type surface emitting laser.

In the light receiving device 30 according to the second embodiment, as shown in FIG. 14A, the pixel area 320 of the optical sensor 32 corresponds to the continuous light emitting area and the normal light emitting area on the light source unit 20 side, and the reading area 320A by continuous light emitting is used. And the read area 320B by normal light emission can be set. Then, for the read region 320A by continuous light emission, the histogram generation is executed once based on the reflected light event occurrence timing estimation technique according to the first embodiment, that is, the received continuous reflected pulse light, and the generated histogram is obtained. Based on this, a technique for estimating the timing of occurrence of a reflected light event can be applied. Incidentally, the feedback process cannot be applied to the read-out region 320B by normal light emission because the light source unit 20 does not irradiate the continuous light emission pulse light in a short time.

As described above, in the pixel area 320 of the optical sensor 32, a first read area 320A due to continuous light emission from the light source unit 20 and a second read area 320B due to normal light emission from the light source unit 20 are set, and the first read is performed. By applying the reflected light event occurrence timing estimation technique according to the first embodiment to the region 320A, the following actions and effects can be obtained. For example, as shown in FIG. 14B, the light receiving content is acquired over the entire surface of the pixel area 320 of the optical sensor 32, but it is particularly effective in a situation where it is desired to increase the time resolution only in the central portion of the light receiving content. Can be done. Further, since the histogram is generated using only the SPAD output pulse of the first read area 320A, the capacity of the memory used for generating the histogram can be reduced.

(Modification of Example 2)
As a modification of the second embodiment, as shown in FIG. 15, using the result of the histogram acquired based on the continuous light emission, the setting position of the first read area 320A by the continuous light emission is set in the pixel area 320 of the optical sensor 32. You may change it. Specifically, as a first step, the entire surface of the pixel area 320 of the optical sensor 32 is read out with a coarse time resolution, and then, as a second step, it is found that a distance measuring object (subject) exists. The process of narrowing down the area of interest is performed. In the case of the figure on the right side of FIG. 15, the upper left and lower right of the pixel area 320 are the areas of interest, which enhances the time resolution of those areas. As described above, in the pixel region 320 of the optical sensor 32, narrowing down the first readout region 320A by continuous light emission is effective in reducing the power consumption of the light receiving device 30.

[Example 3]
Example 3 is an example in which a ΔΣ type time measuring unit (hereinafter, “ΔΣTDC” is used as the time measuring unit 330 and the measurement result of ΔΣTDC is fed back to the input. Here, ΔΣTDC uses a ΔΣ modulation technique. It is the time measurement unit that was there.

An example of the configuration of the light receiving device 30 according to the third embodiment is shown in FIG. In the light receiving device 30 according to the third embodiment, an analog low-pass filter (LPF) 56 composed of a resistance element R and a capacitive element C is provided after the CMOS inverter 55 that waveform-shapes _{the cathode voltage V CA of the SPAD element 51, and thereafter.} A comparator 57 is provided on the stage. The analog low-pass filter 56 waveform-shapes the output pulse of the SPAD element 51 to generate a histogram of the reflected light event. The comparator 57 has a distance measurement target determination threshold value as a comparison reference, and compares it with the output of the analog low-pass filter 56.

The output of the comparator 57 is input to the time measuring unit 330 composed of ΔΣTDC. The time measuring unit 330 using the delta-sigma modulation technique includes a subtractor 3301, an integrator 3302, a comparator 3303, and a digital-to-analog converter (DAC) 3304. The subtractor 3301 takes the difference between the two input signals. The integrator 3302 performs time integration on the output of the subtractor 3301. Comparator 3303 quantizes the output of integrator 3302.

In the light receiving device 30 according to the third embodiment of the above configuration, the feedback circuit portion is configured by using the digital-to-analog converter 3304, but the present invention is not limited to this configuration, and a general negative feedback system is used. It may have a circuit configuration.

FIG. 17 shows the signal waveform of each part of the light receiving device 30 according to the third embodiment. FIG. 17 shows the timing waveforms of the continuous emission pulse light emitted from the light source unit 20, the output pulse of the SPAD element 51, the output of the analog low-pass filter 56 (LPF output), and the output of the comparator 57 (CMP output). Shown.

As is clear from the timing waveform diagram of FIG. 17, the SPAD output pulse obtained by receiving the continuously reflected pulse light from the distance measuring object based on the continuous emission pulse light from the light source unit 20 is passed through the analog low pass filter 56. By shaping the waveform, it is possible to obtain a histogram in which the measurement times of the SPAD output pulses are accumulated. The comparator 57 compares the output (LPF output) of the analog low-pass filter 56 with the distance measurement target determination threshold value, and sets a pulse width from the distance measurement start timing to the timing when the LPF output exceeds the distance measurement target determination threshold value. Output. This pulse width is the estimated time until it is estimated that a reflected light event will occur.

Here, the actual operation of the time measuring unit 330 composed of ΔΣTDC will be described with reference to the circuit diagram of FIG. FIG. 18 is a circuit diagram for explaining the actual operation of the time measuring unit 330 including ΔΣTDC.

Here, a circuit configuration in which a low-pass filter 58 is provided on the output side of the time measurement unit 330 is shown, the TDC input is x, the TDC output is y, and the output of the low-pass filter 58 is z. The signal waveforms of each part of the circuit of FIG. 18, that is, the signal waveforms of the TDC input x, the TDC output y, and the output z of the low-pass filter 58 are shown in FIG.

As described above, in the third embodiment, as in the first and second embodiments, the histogram generated by the time measuring unit 330 is used, and the distance measurement result based on the histogram is obtained in the time resolution and the reading area of the optical sensor. Instead of feeding back to the control of, ΔΣTDC is used as the time measuring unit 330, and the measurement result of ΔΣTDC is fed back to the input.

Also in the case of the third embodiment, as in the case of the first and second embodiments, the light source unit 20 emits the continuously emitted pulsed light in a short time to receive the continuously reflected pulsed light from the distance measuring object. Since the occurrence timing of the reflected light event can be estimated based on the SPAD output pulse according to the above, the distance measurement can be performed in a short time.

Further, according to the third embodiment, the time measuring unit 330 may use a TDC method other than the method of accumulating the measurement times of the SPAD output pulses to generate a histogram, specifically, a method using the ΔΣ modulation technique. it can. Then, by using ΔΣTDC as the time measuring unit 330, it is possible to suppress the rounding error due to the time resolution and perform the distance measurement with a higher time resolution.

Here, the ΔΣ modulator which is the basis of the ΔΣ TDC used as the time measuring unit 330 will be described. A circuit diagram of the basic configuration of the ΔΣ modulator is shown in FIG. 20A, and a diagram in which the basic configuration is modeled in the z region is shown in FIG. 20B.

In the ΔΣ modulator having the above configuration, where x is the analog input, y is the analog output, and N _q is the quantization noise.
(X-yz ^-1 ) (1 / (1-z ^-1 ) + N _q = y
Therefore, the analog output y is
y = x + N _q (1-z ^-1 )
Is represented by the sum of the analog input x and the quantization noise N _{q that has passed through the high frequency pass filter.} Since the power of the quantization noise N _q is constant, the ΔΣ modulator including the integrator shifts the noise to the high frequency side due to the effect of so-called noise shaping, as shown in FIG. The delta-sigma modulator can achieve very high resolution by removing the noise that has transitioned to the high frequency side with a subsequent filter (corresponding to the low-pass filter 58 in FIG. 18) having an appropriate cutoff frequency. ..

FIG. 21 is a diagram for explaining the difference in the distribution of quantization noise depending on the presence or absence of noise shaping. In FIG. 21, the figure on the left side shows the case without noise shaping, and the figure on the right side shows the case with noise shaping.

As is clear from the above, by using the ΔΣ TDC composed of the ΔΣ modulator capable of achieving extremely high resolution due to the effect of noise shaping as the time measuring unit 330, the time measuring unit 330 having extremely high resolution is used. Will be realized.

<Modification example>
The technique according to the present disclosure has been described above based on the preferred embodiment, but the technique according to the present disclosure is not limited to the embodiment. The configurations and structures of the light receiving device and the distance measuring device described in the above embodiment are examples, and can be changed as appropriate.

<Application example of the technology according to the present disclosure>
The technology according to the present disclosure can be applied to various products. A more specific application example will be described below. For example, the technology according to the present disclosure includes any type of movement such as automobiles, electric vehicles, hybrid electric vehicles, motorcycles, bicycles, personal mobility, airplanes, drones, ships, robots, construction machines, agricultural machines (tractors), and the like. It may be realized as a distance measuring device mounted on the body.

[Mobile]
FIG. 22 is a block diagram showing a schematic configuration example of a vehicle control system 7000, which is an example of a mobile control system to which the technique according to the present disclosure can be applied. The vehicle control system 7000 includes a plurality of electronic control units connected via the communication network 7010. In the example shown in FIG. 22, the vehicle control system 7000 includes a drive system control unit 7100, a body system control unit 7200, a battery control unit 7300, an external information detection unit 7400, an in-vehicle information detection unit 7500, and an integrated control unit 7600. .. The communication network 7010 connecting these plurality of control units conforms to any standard such as CAN (Controller Area Network), LIN (Local Interconnect Network), LAN (Local Area Network) or FlexRay (registered trademark). It may be an in-vehicle communication network.

Each control unit includes a microcomputer that performs arithmetic processing according to various programs, a storage unit that stores a program executed by the microcomputer or parameters used for various arithmetics, and a drive circuit that drives various control target devices. To be equipped. Each control unit is provided with a network I / F for communicating with other control units via the communication network 7010, and is provided by wired communication or wireless communication with devices or sensors inside or outside the vehicle. A communication I / F for performing communication is provided. In FIG. 22, as the functional configuration of the integrated control unit 7600, the microcomputer 7610, the general-purpose communication I / F 7620, the dedicated communication I / F 7630, the positioning unit 7640, the beacon receiving unit 7650, the in-vehicle device I / F 7660, the audio image output unit 7670, The vehicle-mounted network I / F 7680 and the storage unit 7690 are shown. Other control units also include a microcomputer, a communication I / F, a storage unit, and the like.

The drive system control unit 7100 controls the operation of the device related to the drive system of the vehicle according to various programs. For example, the drive system control unit 7100 provides a driving force generator for generating the driving force of the vehicle such as an internal combustion engine or a driving motor, a driving force transmission mechanism for transmitting the driving force to the wheels, and a steering angle of the vehicle. It functions as a control device such as a steering mechanism for adjusting and a braking device for generating a braking force of a vehicle. The drive system control unit 7100 may have a function as a control device such as ABS (Antilock Brake System) or ESC (Electronic Stability Control).

The vehicle condition detection unit 7110 is connected to the drive system control unit 7100. The vehicle state detection unit 7110 may include, for example, a gyro sensor that detects the angular velocity of the axial rotation motion of the vehicle body, an acceleration sensor that detects the acceleration of the vehicle, an accelerator pedal operation amount, a brake pedal operation amount, or steering wheel steering. Includes at least one of the sensors for detecting angular velocity, engine speed, wheel speed, and the like. The drive system control unit 7100 performs arithmetic processing using a signal input from the vehicle state detection unit 7110 to control an internal combustion engine, a drive motor, an electric power steering device, a braking device, and the like.

The body system control unit 7200 controls the operation of various devices mounted on the vehicle body according to various programs. For example, the body system control unit 7200 functions as a keyless entry system, a smart key system, a power window device, or a control device for various lamps such as head lamps, back lamps, brake lamps, blinkers or fog lamps. In this case, the body system control unit 7200 may be input with radio waves transmitted from a portable device that substitutes for the key or signals of various switches. The body system control unit 7200 receives inputs of these radio waves or signals and controls a vehicle door lock device, a power window device, a lamp, and the like.

The battery control unit 7300 controls the secondary battery 7310, which is the power supply source of the drive motor, according to various programs. For example, information such as the battery temperature, the battery output voltage, or the remaining capacity of the battery is input to the battery control unit 7300 from the battery device including the secondary battery 7310. The battery control unit 7300 performs arithmetic processing using these signals to control the temperature of the secondary battery 7310 or the cooling device provided in the battery device.

The vehicle outside information detection unit 7400 detects information outside the vehicle equipped with the vehicle control system 7000. For example, at least one of the image pickup unit 7410 and the vehicle exterior information detection unit 7420 is connected to the vehicle exterior information detection unit 7400. The imaging unit 7410 includes at least one of a ToF (Time Of Flight) camera, a stereo camera, a monocular camera, an infrared camera, and other cameras. The vehicle exterior information detection unit 7420 is used to detect, for example, the current weather or an environment sensor for detecting the weather, or other vehicles, obstacles, pedestrians, etc. around the vehicle equipped with the vehicle control system 7000. At least one of the surrounding information detection sensors is included.

The environment sensor may be, for example, at least one of a raindrop sensor that detects rainy weather, a fog sensor that detects fog, a sunshine sensor that detects the degree of sunshine, and a snow sensor that detects snowfall. The ambient information detection sensor may be at least one of an ultrasonic sensor, a radar device, and a LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) device. The image pickup unit 7410 and the vehicle exterior information detection unit 7420 may be provided as independent sensors or devices, or may be provided as a device in which a plurality of sensors or devices are integrated.

Here, FIG. 23 shows an example of the installation positions of the image pickup unit 7410 and the vehicle exterior information detection unit 7420. The imaging units 7910, 7912, 7914, 7916, 7918 are provided, for example, at at least one of the front nose, side mirrors, rear bumpers, back door, and upper part of the windshield of the vehicle interior of the vehicle 7900. The image pickup unit 7910 provided on the front nose and the image pickup section 7918 provided on the upper part of the windshield in the vehicle interior mainly acquire an image in front of the vehicle 7900. The imaging units 7912 and 7914 provided in the side mirrors mainly acquire images of the side of the vehicle 7900. The image pickup unit 7916 provided on the rear bumper or the back door mainly acquires an image of the rear of the vehicle 7900. The imaging unit 7918 provided on the upper part of the windshield in the vehicle interior is mainly used for detecting a preceding vehicle, a pedestrian, an obstacle, a traffic light, a traffic sign, a lane, or the like.

Note that FIG. 23 shows an example of the shooting range of each of the imaging units 7910, 7912, 7914, 7916. The imaging range a indicates the imaging range of the imaging unit 7910 provided on the front nose, the imaging ranges b and c indicate the imaging ranges of the imaging units 7912 and 7914 provided on the side mirrors, respectively, and the imaging range d indicates the imaging range d. The imaging range of the imaging unit 7916 provided on the rear bumper or the back door is shown. For example, by superimposing the image data captured by the imaging units 7910, 7912, 7914, 7916, a bird's-eye view image of the vehicle 7900 as viewed from above can be obtained.

The vehicle exterior information detection units 7920, 7922, 7924, 7926, 7928, 7930 provided on the front, rear, side, corners of the vehicle 7900 and the upper part of the windshield in the vehicle interior may be, for example, an ultrasonic sensor or a radar device. The vehicle exterior information detection units 7920, 7926, 7930 provided on the front nose, rear bumper, back door, and upper part of the windshield in the vehicle interior of the vehicle 7900 may be, for example, a lidar device. These out-of-vehicle information detection units 7920 to 7930 are mainly used for detecting a preceding vehicle, a pedestrian, an obstacle, or the like.

Return to FIG. 22 and continue the explanation. The vehicle outside information detection unit 7400 causes the image pickup unit 7410 to capture an image of the outside of the vehicle and receives the captured image data. Further, the vehicle exterior information detection unit 7400 receives detection information from the connected vehicle exterior information detection unit 7420. When the vehicle exterior information detection unit 7420 is an ultrasonic sensor, a radar device, or a lidar device, the vehicle exterior information detection unit 7400 transmits ultrasonic waves, electromagnetic waves, or the like, and receives received reflected wave information. The vehicle exterior information detection unit 7400 may perform object detection processing or distance detection processing such as a person, a vehicle, an obstacle, a sign, or a character on a road surface based on the received information. The vehicle exterior information detection unit 7400 may perform an environment recognition process for recognizing rainfall, fog, road surface conditions, etc., based on the received information. The vehicle outside information detection unit 7400 may calculate the distance to an object outside the vehicle based on the received information.

Further, the vehicle exterior information detection unit 7400 may perform image recognition processing or distance detection processing for recognizing a person, a vehicle, an obstacle, a sign, a character on the road surface, or the like based on the received image data. The vehicle exterior information detection unit 7400 performs processing such as distortion correction or alignment on the received image data, and synthesizes the image data captured by different imaging units 7410 to generate a bird's-eye view image or a panoramic image. May be good. The vehicle exterior information detection unit 7400 may perform the viewpoint conversion process using the image data captured by different imaging units 7410.

The in-vehicle information detection unit 7500 detects the in-vehicle information. For example, a driver state detection unit 7510 that detects the driver's state is connected to the in-vehicle information detection unit 7500. The driver state detection unit 7510 may include a camera that captures the driver, a biosensor that detects the driver's biological information, a microphone that collects sound in the vehicle interior, and the like. The biosensor is provided on, for example, the seat surface or the steering wheel, and detects the biometric information of the passenger sitting on the seat or the driver holding the steering wheel. The in-vehicle information detection unit 7500 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 7510, and may determine whether the driver is dozing or not. You may. The in-vehicle information detection unit 7500 may perform processing such as noise canceling processing on the collected audio signal.

The integrated control unit 7600 controls the overall operation in the vehicle control system 7000 according to various programs. An input unit 7800 is connected to the integrated control unit 7600. The input unit 7800 is realized by a device such as a touch panel, a button, a microphone, a switch or a lever, which can be input-operated by a passenger. Data obtained by recognizing the voice input by the microphone may be input to the integrated control unit 7600. The input unit 7800 may be, for example, a remote control device using infrared rays or other radio waves, or an externally connected device such as a mobile phone or a PDA (Personal Digital Assistant) that supports the operation of the vehicle control system 7000. You may. The input unit 7800 may be, for example, a camera, in which case the passenger can input information by gesture. Alternatively, data obtained by detecting the movement of the wearable device worn by the passenger may be input. Further, the input unit 7800 may include, for example, an input control circuit that generates an input signal based on the information input by the passenger or the like using the input unit 7800 and outputs the input signal to the integrated control unit 7600. By operating the input unit 7800, the passenger or the like inputs various data to the vehicle control system 7000 and instructs the processing operation.

The storage unit 7690 may include a ROM (Read Only Memory) for storing various programs executed by the microcomputer, and a RAM (Random Access Memory) for storing various parameters, calculation results, sensor values, and the like. Further, the storage unit 7690 may be realized by a magnetic storage device such as an HDD (Hard Disc Drive), a semiconductor storage device, an optical storage device, an optical magnetic storage device, or the like.

The general-purpose communication I / F 7620 is a general-purpose communication I / F that mediates communication with various devices existing in the external environment 7750. General-purpose communication I / F7620 is a cellular communication protocol such as GSM (registered trademark) (Global System of Mobile communications), WiMAX, LTE (Long Term Evolution) or LTE-A (LTE-Advanced), or wireless LAN (Wi-Fi). Other wireless communication protocols such as (also referred to as (registered trademark)) and Bluetooth (registered trademark) may be implemented. The general-purpose communication I / F 7620 connects to a device (for example, an application server or a control server) existing on an external network (for example, the Internet, a cloud network, or a business-specific network) via, for example, a base station or an access point. You may. Further, the general-purpose communication I / F7620 uses, for example, P2P (Peer To Peer) technology, and is a terminal existing in the vicinity of the vehicle (for example, a terminal of a driver, a pedestrian, or a store, or an MTC (Machine Type Communication) terminal). May be connected with.

The dedicated communication I / F 7630 is a communication I / F that supports a communication protocol formulated for use in a vehicle. The dedicated communication I / F7630 uses a standard protocol such as WAVE (Wireless Access in Vehicle Environment), DSRC (Dedicated Short Range Communications), or cellular communication protocol, which is a combination of lower layer IEEE802.11p and upper layer IEEE1609. May be implemented. Dedicated communication I / F7630 typically includes vehicle-to-vehicle (Vehicle to Vehicle) communication, road-to-vehicle (Vehicle to Infrastructure) communication, vehicle-to-home (Vehicle to Home) communication, and pedestrian-to-pedestrian (Vehicle to Pedertian) communication. ) Carry out V2X communication, a concept that includes one or more of the communications.

The positioning unit 7640 receives, for example, a GNSS signal from a GNSS (Global Navigation Satellite System) satellite (for example, a GPS signal from a GPS (Global Positioning System) satellite), executes positioning, and executes positioning, and the latitude, longitude, and altitude of the vehicle. Generate location information including. The positioning unit 7640 may specify the current position by exchanging signals with the wireless access point, or may acquire position information from a terminal such as a mobile phone, PHS, or smartphone having a positioning function.

The beacon receiving unit 7650 receives radio waves or electromagnetic waves transmitted from a radio station or the like installed on the road, and acquires information such as the current position, traffic jam, road closure, or required time. The function of the beacon receiving unit 7650 may be included in the above-mentioned dedicated communication I / F 7630.

The in-vehicle device I / F 7660 is a communication interface that mediates the connection between the microcomputer 7610 and various in-vehicle devices 7760 existing in the vehicle. The in-vehicle device I / F7660 may establish a wireless connection using a wireless communication protocol such as wireless LAN, Bluetooth (registered trademark), NFC (Near Field Communication) or WUSB (Wireless USB). In addition, the in-vehicle device I / F7660 is connected via a connection terminal (and a cable if necessary) (not shown), USB (Universal Serial Bus), HDMI (registered trademark) (High-Definition Multimedia Interface), or MHL (Mobile). A wired connection such as High-definition Link) may be established. The in-vehicle device 7760 may include, for example, at least one of a passenger's mobile device or wearable device, or an information device carried or attached to the vehicle. In addition, the in-vehicle device 7760 may include a navigation device that searches for a route to an arbitrary destination. The in-vehicle device I / F 7660 exchanges control signals or data signals with these in-vehicle devices 7760.

The in-vehicle network I / F7680 is an interface that mediates communication between the microcomputer 7610 and the communication network 7010. The vehicle-mounted network I / F7680 transmits and receives signals and the like according to a predetermined protocol supported by the communication network 7010.

The microcomputer 7610 of the integrated control unit 7600 is via at least one of general-purpose communication I / F7620, dedicated communication I / F7630, positioning unit 7640, beacon receiving unit 7650, in-vehicle device I / F7660, and in-vehicle network I / F7680. Based on the information acquired in the above, the vehicle control system 7000 is controlled according to various programs. For example, the microcomputer 7610 calculates the control target value of the driving force generator, the steering mechanism, or the braking device based on the acquired information inside and outside the vehicle, and outputs a control command to the drive system control unit 7100. May be good. For example, the microcomputer 7610 realizes ADAS (Advanced Driver Assistance System) functions including vehicle collision avoidance or impact mitigation, follow-up driving based on inter-vehicle distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane deviation warning, and the like. Cooperative control may be performed for the purpose of. In addition, the microcomputer 7610 automatically travels autonomously without relying on the driver's operation by controlling the driving force generator, steering mechanism, braking device, etc. based on the acquired information on the surroundings of the vehicle. Coordinated control for the purpose of driving or the like may be performed.

The microcomputer 7610 has information acquired via at least one of general-purpose communication I / F7620, dedicated communication I / F7630, positioning unit 7640, beacon receiving unit 7650, in-vehicle device I / F7660, and in-vehicle network I / F7680. Based on the above, three-dimensional distance information between the vehicle and an object such as a surrounding structure or a person may be generated, and local map information including the peripheral information of the current position of the vehicle may be created. Further, the microcomputer 7610 may predict a danger such as a vehicle collision, a pedestrian or the like approaching or entering a closed road based on the acquired information, and may generate a warning signal. The warning signal may be, for example, a signal for generating a warning sound or turning on a warning lamp.

The audio image output unit 7670 transmits an output signal of at least one of audio and an image to an output device capable of visually or audibly notifying information to the passenger or the outside of the vehicle. In the example of FIG. 22, an audio speaker 7710, a display unit 7720, and an instrument panel 7730 are exemplified as output devices. The display unit 7720 may include, for example, at least one of an onboard display and a heads-up display. The display unit 7720 may have an AR (Augmented Reality) display function. The output device may be other devices other than these devices, such as headphones, wearable devices such as eyeglass-type displays worn by passengers, and projectors or lamps. When the output device is a display device, the display device displays the results obtained by various processes performed by the microcomputer 7610 or the information received from other control units in various formats such as texts, images, tables, and graphs. Display visually. When the output device is an audio output device, the audio output device converts an audio signal composed of reproduced audio data, acoustic data, or the like into an analog signal and outputs it audibly.

In the example shown in FIG. 22, at least two control units connected via the communication network 7010 may be integrated as one control unit. Alternatively, each control unit may be composed of a plurality of control units. Further, the vehicle control system 7000 may include another control unit (not shown). Further, in the above description, the other control unit may have a part or all of the functions carried out by any of the control units. That is, as long as information is transmitted and received via the communication network 7010, predetermined arithmetic processing may be performed by any control unit. Similarly, a sensor or device connected to one of the control units may be connected to the other control unit, and the plurality of control units may send and receive detection information to and from each other via the communication network 7010. ..

The above is an example of a vehicle control system to which the technology according to the present disclosure can be applied. The technique according to the present disclosure can be applied to the ToF camera in the above-described configuration, for example, when the imaging unit 7410 includes a ToF camera. Then, by applying the technique according to the present disclosure, it is possible to realize a light receiving device capable of performing distance measurement with high reliability. Then, by mounting the light receiving device as a light receiving device of the distance measuring device, for example, a vehicle control system capable of detecting an object to be measured with high accuracy can be constructed.

<Structure that can be taken by this disclosure>
The present disclosure may also have the following configuration.

≪A. First light receiving device ≫
[A-1] Optical sensor,
Time measurement unit and
System control unit,
With
The optical sensor receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit, and receives the continuously reflected pulsed light.
The time measurement unit generates a histogram of the reflected light event based on the reflected light from the distance measurement object based on the output pulse of the optical sensor.
The system control unit estimates the occurrence timing of the reflected light event based on the histogram generated by the time measurement unit, and feedback-controls the characteristics related to distance measurement based on the estimation result.
Light receiving device.
[A-2] The system control unit estimates the timing when the histogram generated by the time measurement unit exceeds a predetermined threshold value as the occurrence timing of the reflected light event, and based on the estimation result, the time of the time measurement unit. Control the resolution,
The light receiving device according to the above [A-1].
[A-3] The system control unit switches the time resolution of the time measurement unit by changing the sampling frequency for sampling the output pulse of the light receiving element of the optical sensor.
The light receiving device according to the above [A-2].
[A-4] The system control unit changes the time resolution of the time measurement unit from a relatively coarse time resolution to a relatively fine time resolution when the histogram generated by the time measurement unit exceeds a predetermined threshold value. Switch,
The light receiving device according to the above [A-3].
[A-5] The system control unit estimates the timing at which the histogram generated by the time measurement unit exceeds a predetermined threshold value as the occurrence timing of the reflected light event, and based on the estimation result, the pixel area of the optical sensor. Controls the read area in
The light receiving device according to the above [A-1].
[A-6] In the pixel region of the optical sensor, there is a first readout region corresponding to the continuous emission region on the light source side and a second readout region corresponding to the normal emission region having a longer cycle than the continuous emission on the light source side. Areas are mixed and
The system control unit performs a process of estimating the occurrence timing of the reflected light event based on the histogram generated by the time measurement unit for the first read area.
The light receiving device according to the above [A-5].
[A-7] The light receiving element of the optical sensor is composed of an element that generates a signal in response to the light reception of a photon.
The light receiving device according to any one of the above [A-1] to the above [A-6].
[A-8] The light receiving element of the optical sensor is composed of a single photon avalanche diode.
The light receiving device according to the above [A-7].

≪B. Control method of light receiving device ≫
[B-1] An optical sensor that receives continuously reflected pulsed light from a distance measuring object based on irradiation of continuously emitted pulsed light from a light source unit.
In controlling the light receiving device equipped with
Based on the output pulse of the optical sensor, generate a histogram of the reflected light event based on the reflected light from the distance measurement object.
Based on the generated histogram, the timing of occurrence of the reflected light event is estimated, and feedback control is performed on the characteristics related to distance measurement based on the estimation result.
Control method of the light receiving device.

≪C. Second light receiving device ≫
[C-1] Optical sensor,
Low pass filter,
Comparator and
Time measurement unit,
With
The optical sensor receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit.
The low-pass filter waveform-shapes the output pulse of the optical sensor to generate a histogram of reflected light events based on the reflected light from the distance-finding object.
The comparator compares the histogram generated by the low-pass filter with the distance measurement target judgment threshold value, and outputs a pulse whose pulse width is from the distance measurement start timing to the timing when the histogram exceeds the distance measurement target judgment threshold value.
The time measurement unit consists of a delta-sigma type time measurement unit that uses delta-sigma modulation technology, and receives the output pulse of the comparator as an input and feeds back the measurement result to the input.
Light receiving device.
[C-2] The time measurement unit
A subtractor that takes the difference between signals,
An adder that integrates time over the output of the subtractor,
A comparator that quantizes the output of the integrator, and
Digital-to-analog converter that feeds back the output of the comparator as the subtraction input of the subtractor,
The light receiving device according to the above [C-1].
[C-3] The light receiving element of the optical sensor is an element that generates a signal in response to the light reception of a photon.
The light receiving device according to the above [C-1] or the above [C-2].
[C-4] The light receiving element of the optical sensor is composed of a single photon avalanche diode.
The light receiving device according to the above [C-3].

<< D. First ranging device ≫
[D-1] Light source unit and
Receiver,
With
The light source unit irradiates the object to be measured with continuous emission pulsed light,
The light receiving device is
Optical sensor,
Time measurement unit and
System control unit,
With
The optical sensor receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit, and receives the continuously reflected pulsed light.
The time meter generates a histogram of the reflected light event based on the reflected light from the distance measurement object based on the output pulse of the optical sensor.
The system control unit estimates the occurrence timing of the reflected light event based on the histogram generated by the time measurement unit, and feedback-controls the characteristics related to distance measurement based on the estimation result.
Distance measuring device.
[D-2] The light source unit is composed of a surface emitting semiconductor laser in which light sources are two-dimensionally arranged in an array.
The distance measuring device according to the above [D-1].
[D-3] The surface emitting semiconductor laser is a vertical resonator type surface emitting laser.
The distance measuring device according to the above [D-2].
[D-4] In the light emitting region of the light source unit, a continuous light emitting region in which the light emitting unit continuously emits light and a normal light emitting region in which the light emitting unit emits light in a cycle longer than the continuous light emitting cycle are mixed.
The distance measuring device according to the above [D-2] or the above [D-3].
[D-5] In the pixel area of the optical sensor, it is possible to set a first read area corresponding to the continuous light emitting area on the light source side and a second read area corresponding to the normal light emitting area on the light source side. ,
The system control unit performs a process of estimating the occurrence timing of the reflected light event for the first read area.
The distance measuring device according to the above [D-4].

≪E. Second ranging device ≫
[E-1] Light source unit and
Receiver,
With
The light source unit irradiates the object to be measured with continuous emission pulsed light,
The light receiving device is
Optical sensor,
Low pass filter,
Comparator and
Time measurement unit,
With
The optical sensor receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit, and receives the continuously reflected pulsed light.
The lowpass filter waveform-shapes the output pulse of the photosensor to generate a histogram of reflected light events based on the reflected light.
The comparator compares the histogram generated by the low-pass filter with the distance measurement target judgment threshold value, and outputs a pulse whose pulse width is from the distance measurement start timing to the timing when the histogram exceeds the distance measurement target judgment threshold value.
The time measurement unit consists of a delta-sigma type time measurement unit that uses delta-sigma modulation technology, and receives the output pulse of the comparator as an input and feeds back the measurement result to the input.
Distance measuring device.

1 ... Distance measuring device, 10 ... Subject (measurement object), 20 ... Light source unit, 21 ... Laser drive unit, 22 ... Laser light source, 23 ... Diffuse lens, 30 ... .. Light receiving device, 31 ... Light receiving lens, 32 ... Optical sensor, 33 ... Signal processing unit, 40 ... System control unit, 50 ... Pixels, 51 ... SPAD element, 54.・ ・ Load, 55 ・ ・ ・ CMOS inverter, 330 ・ ・ ・ Time measurement unit

Claims (19)

1. Optical sensor,
   Time measurement unit and
   System control unit,
   With
   The optical sensor receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit, and receives the continuously reflected pulsed light.
   The time measurement unit generates a histogram of the reflected light event based on the reflected light from the distance measurement object based on the output pulse of the optical sensor.
   The system control unit estimates the occurrence timing of the reflected light event based on the histogram generated by the time measurement unit, and feedback-controls the characteristics related to distance measurement based on the estimation result.
   Light receiving device.
2. The system control unit estimates the timing when the histogram generated by the time measurement unit exceeds a predetermined threshold value as the occurrence timing of the reflected light event, and controls the time resolution of the time measurement unit based on the estimation result.
   The light receiving device according to claim 1.
3. The system control unit switches the time resolution of the time measurement unit by changing the sampling frequency for sampling the output pulse of the light receiving element of the optical sensor.
   The light receiving device according to claim 2.
4. The system control unit switches the time resolution of the time measurement unit from a relatively coarse time resolution to a relatively fine time resolution when the histogram generated by the time measurement unit exceeds a predetermined threshold value.
   The light receiving device according to claim 3.
5. The system control unit estimates the timing at which the histogram generated by the time measurement unit exceeds a predetermined threshold value as the occurrence timing of the reflected light event, and controls the readout area in the pixel area of the optical sensor based on the estimation result. To do,
   The light receiving device according to claim 1.
6. In the pixel area of the optical sensor, a first readout area corresponding to the continuous light emission region on the light source side and a second readout region corresponding to the normal light emission region having a longer cycle than the continuous light emission on the light source side are mixed. And
   The system control unit performs a process of estimating the occurrence timing of the reflected light event based on the histogram generated by the time measurement unit for the first read area.
   The light receiving device according to claim 5.
7. The light receiving element of the optical sensor consists of an element that generates a signal in response to the light reception of a photon.
   The light receiving device according to claim 1.
8. The light receiving element of the photosensor consists of a single photon avalanche diode.
   The light receiving device according to claim 7.
9. An optical sensor that receives continuously reflected pulsed light from a distance measuring object based on irradiation of continuously emitted pulsed light from a light source unit.
   In controlling the light receiving device equipped with
   Based on the output pulse of the optical sensor, generate a histogram of the reflected light event based on the reflected light from the distance measurement object.
   Based on the generated histogram, the timing of occurrence of the reflected light event is estimated, and feedback control is performed on the characteristics related to distance measurement based on the estimation result.
   Control method of the light receiving device.
10. Optical sensor,
    Low pass filter,
    Comparator and
    Time measurement unit,
    With
    The optical sensor receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit, and receives the continuously reflected pulsed light.
    The low-pass filter waveform-shapes the output pulse of the optical sensor to generate a histogram of reflected light events based on the reflected light from the distance-finding object.
    The comparator compares the histogram generated by the low-pass filter with the distance measurement target judgment threshold value, and outputs a pulse whose pulse width is from the distance measurement start timing to the timing when the histogram exceeds the distance measurement target judgment threshold value.
    The time measurement unit consists of a delta-sigma type time measurement unit that uses delta-sigma modulation technology, and receives the output pulse of the comparator as an input and feeds back the measurement result to the input.
    Light receiving device.
11. The time measurement unit
    A subtractor that takes the difference between signals,
    An adder that integrates time over the output of the subtractor,
    A comparator that quantizes the output of the integrator, and
    Digital-to-analog converter that feeds back the output of the comparator as the subtraction input of the subtractor,
    The light receiving device according to claim 10.
12. The light receiving element of the optical sensor consists of an element that generates a signal in response to the light reception of a photon.
    The light receiving device according to claim 10.
13. The light receiving element of the photosensor consists of a single photon avalanche diode.
    The light receiving device according to claim 12.
14. Light source and
    Receiver,
    With
    The light source unit irradiates the object to be measured with continuous emission pulsed light,
    The light receiving device is
    Optical sensor,
    Time measurement unit and
    System control unit,
    With
    The optical sensor receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit, and receives the continuously reflected pulsed light.
    The time meter generates a histogram of the reflected light event based on the reflected light from the distance measurement object based on the output pulse of the optical sensor.
    The system control unit estimates the occurrence timing of the reflected light event based on the histogram generated by the time measurement unit, and feedback-controls the characteristics related to distance measurement based on the estimation result.
    Distance measuring device.
15. The light source unit is composed of a surface emitting semiconductor laser in which light sources are arranged two-dimensionally in an array.
    The distance measuring device according to claim 14.
16. The surface emitting semiconductor laser is a vertical resonator type surface emitting laser.
    The distance measuring device according to claim 15.
17. The light emitting region of the light source unit includes a continuous light emitting region in which the light emitting unit continuously emits light and a normal light emitting region in which the light emitting unit emits light in a cycle longer than the continuous light emitting cycle.
    The distance measuring device according to claim 15.
18. In the pixel area of the optical sensor, it is possible to set a first read area corresponding to the continuous light emitting area on the light source side and a second read area corresponding to the normal light emitting area on the light source side.
    The system control unit performs a process of estimating the occurrence timing of the reflected light event for the first read area.
    The distance measuring device according to claim 17.
19. Light source and
    Receiver,
    With
    The light source unit irradiates the object to be measured with continuous emission pulsed light,
    The light receiving device is
    Optical sensor,
    Low pass filter,
    Comparator and
    Time measurement unit,
    With
    The optical sensor receives the continuously reflected pulsed light from the distance measuring object based on the irradiation of the continuously emitted pulsed light from the light source unit, and receives the continuously reflected pulsed light.
    The lowpass filter waveform-shapes the output pulse of the photosensor to generate a histogram of reflected light events based on the reflected light.
    The comparator compares the histogram generated by the low-pass filter with the distance measurement target judgment threshold value, and outputs a pulse whose pulse width is from the distance measurement start timing to the timing when the histogram exceeds the distance measurement target judgment threshold value.
    The time measurement unit consists of a delta-sigma type time measurement unit that uses delta-sigma modulation technology, and receives the output pulse of the comparator as an input and feeds back the measurement result to the input.
    Distance measuring device.

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