Distance measurement device and apparatus

Abstract

To provide a technique advantageous for suppressing power consumption.SOLUTION: A distance measurement device comprises a plurality of pixels each including a photoelectric conversion element, and a calculation circuit for generating distance information based on a signal obtained by the plurality of pixels. A sequence for generating the distance information includes a plurality of distance measurement frames. Each of the plurality of distance measurement frames includes a plurality of subframes in which periods of time between a period of light irradiation by a light source and a period of performing a detection operation for detecting light reflected on an object by applying reverse bias to the photoelectric conversion element are different from each other. The distance measurement device further comprises a stop control circuit which generates a stop signal in the plurality of distance measurement frames when a plurality of signals obtained by the detection operation of each of the plurality of subframes satisfy a predetermined condition. Each of the plurality of pixels does not perform the detection operation for, from among the plurality of distance measurement frames, a distance measurement frame supplied with the stop signal from the stop control circuit.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to distance measuring devices and instruments. [Background technology]

[0002] There is known a distance measuring device of the Time of Flight (ToF) method, which measures distance by emitting light from a light source and detecting the light reflected by an object. Patent Document 1 describes distance measurement by the time gate method. In the time gate method, during a period in which a distance measuring operation for measuring the distance to an object is performed, a distance measuring operation is performed over a number of frames by changing the time from the irradiation of light to the detection operation for detecting the light reflected by the object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2017 / 0052065 Summary of the Invention [Problem to be solved by the invention]

[0004] In measuring the distance to an object with low reflectance, it is conceivable to repeat the distance measurement operation multiple times in order to improve the accuracy of detecting reflected light, but repeating the distance measurement operation increases power consumption.

[0005] An object of the present invention is to provide a technique that is advantageous in reducing power consumption. [Means for solving the problem]

[0006] In consideration of the above problems, a distance measuring device according to an embodiment of the present invention is a distance measuring device comprising a plurality of pixels each including a photoelectric conversion element, and an arithmetic circuit for generating distance information based on signals obtained by the plurality of pixels, wherein a sequence for generating the distance information includes a plurality of distance measuring frames (two or more distance measuring frames), each of the plurality of distance measuring frames including a plurality of subframes having different times between irradiation of light by a light source and a period in which a detection operation for detecting the light reflected by an object is performed by applying a reverse bias to the photoelectric conversion element, and further comprising a stop control circuit that generates a stop signal in the plurality of distance measuring frames when a plurality of signals obtained by the detection operation in each of the plurality of subframes satisfy a predetermined condition, and each of the plurality of pixels does not perform the detection operation in the distance measuring frame after the stop signal is supplied from the stop control circuit among the plurality of distance measuring frames. Effect of the Invention

[0007] According to the present invention, it is possible to provide a technique that is advantageous in reducing power consumption. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing an example of the configuration of a distance measuring device according to the present embodiment. [Diagram 2] 2 is a diagram showing an example of the configuration of a light receiving unit of the distance measuring device in FIG. 1; [Diagram 3] 2 is a diagram showing an example of the arrangement of a pixel in the distance measuring device of FIG. 1; [Figure 4] 2 is a diagram showing an example of the operation of the distance measuring device in FIG. 1; [Diagram 5] 2 is a diagram showing an example of the operation of the distance measuring device in FIG. 1; [Figure 6] 2 is a diagram showing an example of the operation of the distance measuring device in FIG. 1; [Figure 7] FIG. 2 is a diagram showing a modification of the distance measuring device in FIG. [Figure 8] 8 is a diagram showing an example of the arrangement of a pixel in the distance measuring device of FIG. 7; [Figure 9] FIG. 1 is a diagram showing an example of the configuration of a device incorporating a photoelectric conversion device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] A distance measuring device according to an embodiment of the present disclosure will be described with reference to Figures 1 to 8. Figure 1 is a block diagram that shows a schematic configuration example of a distance measuring device 100 according to this embodiment. As shown in Figure 1, the distance measuring device 100 includes a light emitting unit 101, a light receiving unit 102, a timing control unit 103, a register 104, an arithmetic circuit 105, and a communication interface (IF) 106.

[0011] The timing control unit 103 controls the operation timing of each component arranged in the distance measuring device 100. More specifically, the timing control unit 103 outputs a control signal to the light-emitting unit 101 to control the timing at which the light-emitting unit 101 emits light. The timing control unit 103 also outputs a control signal to the light-receiving unit 102 to control the timing at which the light-receiving unit 102 performs a detection operation to detect light reflected by an object.

[0012] The light-emitting unit 101 includes a light source 111 that emits light based on a control signal from the timing control unit 103. For example, a semiconductor laser diode is used as the light source 111. In this case, the light source 111 generates a laser light having a predetermined pulse width in response to the control signal supplied from the timing control unit 103. An optical member (not shown) such as a diffusion plate is disposed in the light-emitting unit 101, and the light emitted from the light source 111 is diffused and irradiated in a predetermined two-dimensional range.

[0013] The light receiving unit 102 includes a so-called image sensor. The light receiving unit 102 may be, for example, a CMOS sensor or a SPAD sensor using an avalanche photodiode (hereinafter, sometimes referred to as APD). The configuration of the light receiving unit 102 will be described later.

[0014] The arithmetic circuit 105 is arranged to generate distance information to the object 110 based on signals obtained by multiple pixels arranged in the light receiving unit 102. The arithmetic circuit 105 may generate a three-dimensional distance image or the like from the obtained distance information. The arithmetic circuit 105 may use a semiconductor device such as a CPU or ASIC.

[0015] The register 104 stores setting values ​​and the like for operating the distance measuring device 100. The communication IF 106 is provided for outputting data such as distance measurement information obtained by the distance measuring device 100 to the outside. Data for operating the distance measuring device 100 may also be supplied to the register 104 via the communication IF 106.

[0016] 2 is a block diagram showing an example of the configuration of the light receiving section 102 in this embodiment. The light receiving section 102 may include a pixel section 201, a control pulse generating circuit 215, a vertical scanning circuit 210, a horizontal scanning circuit 211, a readout circuit 212, signal lines 213, 216, 217, and an output circuit 214.

[0017] In the pixel unit 201, a plurality of pixels 204 are arranged in a two-dimensional array (matrix). Each of the pixels 204 includes a photoelectric conversion circuit 202 and a pixel circuit 203. As will be described later with reference to FIG. 3, in this embodiment, the photoelectric conversion circuit 202 includes an APD as a photoelectric conversion element. In this embodiment, the pixels 204 arranged in the pixel unit 201 include the photoelectric conversion circuit 202 and the pixel circuit 203, but are not limited thereto, and it is sufficient that at least the APD is arranged in a two-dimensional array in the pixel unit 201. Light incident on the pixel unit 201 is converted into an electric signal by the pixels 204 arranged in the pixel unit 201. The pixel circuit 203 outputs the electric signal photoelectrically converted by the photoelectric conversion circuit 202 to a signal line 213.

[0018] The control pulse generating circuit 215 controls the vertical scanning circuit 210, the horizontal scanning circuit 211, and the readout circuit 212 in accordance with a control signal supplied from the timing control unit 103. In addition, the control pulse generating circuit 215 supplies control pulses to each of the pixels 204 via signal lines 216 and 217.

[0019] The vertical scanning circuit 210 supplies a control pulse to each of the pixels 204 in accordance with the control pulse supplied from the control pulse generating circuit 215. The vertical scanning circuit 210 may include logic circuits such as a shift register and an address decoder.

[0020] The signal output from the photoelectric conversion circuit 202 of each pixel 204 is processed by the pixel circuit 203. The pixel circuit 203 may be provided with a counter circuit or the like. Also, the pixel circuit 203 may be provided with a stop control circuit, the details of which will be described below.

[0021] The horizontal scanning circuit 211 supplies a control pulse to the pixel circuit 203 for sequentially selecting the pixels 204 arranged in the pixel unit 201 for each column in order to read out the signal from the memory of each pixel 204 in which the digital signal is held. A signal is output to a signal line 213 from the pixel circuit 203 of the pixel 204 selected by the vertical scanning circuit 210 for the selected row. The signal output to the signal line 213 is output to the arithmetic circuit 105 via a readout circuit 212 including, for example, a multiplexer, and an output circuit 214.

[0022] 2, the pixels 204 are arranged in a two-dimensional array in the pixel section 201. However, this is not limited thereto, and the pixel section 201 may have a plurality of pixels 204 arranged in a one-dimensional array. Also, the pixel section 201 may have only a single pixel 204 arranged therein.

[0023] Fig. 3 is a block diagram showing an example of the configuration of a pixel 204 in this embodiment. As described above, the pixel 204 includes a photoelectric conversion circuit 202 and a pixel circuit 203. In the configuration shown in Fig. 3, the photoelectric conversion circuit 202 includes an APD 301 as a photoelectric conversion element. The pixel circuit 203 includes a quench element 302, a waveform shaping circuit 303, gate elements 304 to 306, and a distance measurement circuit 300. The distance measurement circuit 300 includes a counter circuit 307, a processing circuit 308, and a stop control circuit 309.

[0024] The APD 301 is connected to a quench element 302 that controls the avalanche current. A photon detection signal output from the APD 301 via a waveform shaping circuit 303 is controlled in time by a pulse signal GATE supplied from a control pulse generating circuit 215 to a gate element 304 via a signal line 217. The output of the gate element 304 is input to a distance measuring circuit 300.

[0025] The APD301 generates charge pairs according to the incident light by photoelectric conversion. A potential based on a potential Vdd, which is higher than the potential VPDL supplied to the anode, is supplied to the cathode of the APD301. A potential Vdd and a potential VPDL are supplied between the anode and cathode of the APD301 so that a reverse bias is applied so that photons incident on the APD301 are avalanche multiplied. By performing photoelectric conversion while supplying such a reverse bias, the charges generated by the incident light in the APD301 undergo avalanche multiplication, generating an avalanche current.

[0026] When a reverse bias is supplied, if the potential difference (voltage) between the anode and the cathode is greater than the breakdown voltage, the APD301 operates in Geiger mode. Hereinafter, the APD301 that uses Geiger mode operation to rapidly detect weak signals at a single photon level may be referred to as a Single Photon Avalanche Diode (SPAD). In this embodiment, a SPAD is used to rapidly detect weak signals, but the operation mode of the APD301 may be a linear mode operation in which avalanche multiplication is performed at a voltage equal to or lower than the breakdown voltage.

[0027] The quench element 302 has a function of converting a change in avalanche current generated in the APD 301 into a voltage signal. When the photocurrent is multiplied by avalanche multiplication in the APD 301, a current obtained by the multiplied charge flows to a connection node between the APD 301 and the quench element 302. Due to a voltage drop caused by this current, the potential of the cathode of the APD 301 drops, and the APD 301 no longer forms an avalanche. This stops the avalanche multiplication of the APD 301. After that, the potential Vdd of the power supply is supplied to the cathode of the APD 301 via the quench element 302, so that the potential supplied to the cathode of the APD 301 returns to the potential Vdd. In other words, the operating region of the APD 301 returns to the Geiger mode operation. In this way, the quench element 302 functions as a load circuit (quench element) when the charge is multiplied by avalanche multiplication, and has a function of suppressing the avalanche multiplication (quench operation). In addition, the quench element 302 has a function of returning the operating region of the APD 301 to the Geiger mode again after suppressing the avalanche multiplication (recharge operation). The application of a reverse bias to the APD 301 by this recharge operation is controlled in time by a pulse signal RC supplied from the control pulse generating circuit 215 to the gate element 305 via the signal line 216.

[0028] For example, an inverter circuit is used as the waveform shaping circuit 303. The waveform shaping circuit 303 shapes the potential change of the cathode of the APD 301 obtained when a photon is detected, and outputs a pulse signal.

[0029] For example, an AND circuit is used for the gate element 304, and the period during which the pixel 204 performs a detection operation to detect light is adjusted by controlling the High / Low level of the control pulse GATE. The detection period refers to a period during which photon detection is possible in the APD 301, and a pulse signal obtained by converting a potential change in the APD 301 by the waveform shaping circuit 303 is output to the counter circuit 307. In the following, a period during which the pixel 204 does not perform a detection operation may be referred to as a non-detection period. The non-detection period is a period during which a pulse signal is not output from the waveform shaping circuit 303 to the counter circuit 307. In an operation example shown in FIG. 4 described later, when the control pulse GATE is at a High level, it is a period during which the detection operation is performed, and when it is at a Low level, it is a non-detection period.

[0030] The counter circuit 307 arranged in the distance measuring circuit 300 is configured to be able to output a signal to the processing circuit 308 and the stop control circuit 309. The counter circuit 307 counts the number of times that a photon is detected by the APD 301 in the detection operation. The processing circuit 308 arranged in the distance measuring circuit 300 generates a plurality of signals indicating the count value of the counter circuit 307 at each timing when the detection operation is performed in order to generate distance information to the object 110. The signals generated by the processing circuit 308 are output to a signal line 213. Based on the signal value (electrical signal) of the signal output from the processing circuit 308, the arithmetic circuit 105 is able to generate distance information to the object 110 and perform distance measurement.

[0031] Fig. 4 is a diagram showing the operation timing of the time-gated ToF method in this embodiment. In this embodiment, a sequence F that generates one piece of distance information includes multiple ranging frames SF. In the configuration shown in Fig. 4, a period T1 of one sequence F is composed of m ranging frames SF of period T2.

[0032] Each of the multiple ranging frames SF includes multiple subframes GF with different times between the irradiation of light by the light source 111 and the period in which a detection operation is performed to detect light reflected by the target object 110 by applying a reverse bias to the APD 301, which is a photoelectric conversion element. In the configuration shown in Fig. 4, the period T2 of one ranging frame SF is composed of k subframes GF of period T3. In other words, there are k types of subframes GF with different times between the irradiation of light by the light source 111 and the period in which the APD 301 performs the detection operation to detect light.

[0033] Each subframe GF is composed of s photon detection frames MF of period T4. The number k of subframes GF included in one ranging frame SF and the number s of photon detection frames MF included in one subframe GF may have a relationship of k≦s, for example, but is not limited to this. At the start of each subframe GF, the light source 111 emits light. In response to the emission of light from the light source 111, a detection operation is performed. In subframe GF11, the rising position of the control pulse RC and the rising position of the control pulse GATE have a phase relationship of T6. Next, the detection operation is performed in the photon detection frame MF2 with the same phase relationship. Thereafter, the detection operation is performed up to the photon detection frame MFs. In subframe GF12, the rising position of the control pulse RC and the rising position of the control pulse GATE have a phase relationship shifted by a certain amount from the phase relationship of T6, and the detection operation is performed in the photon detection frame MF1. In this way, the detection operation is performed sequentially at different times from the emission of light up to subframe GF1k.

[0034] In the photon detection frame in which the detection operation is performed among the photon detection frames MF, the control pulse RC and the control pulse GATE are supplied as shown in FIG. 4. The control pulse RC performs a recharge operation, and a reverse bias is applied to the APD 301, which is a photoelectric conversion element, to make it possible to detect light. Next, when the control pulse GATE is supplied and a photon is detected by the APD 301, a pulse signal obtained by converting the potential change of the APD 301 by the waveform shaping circuit 303 is output to the counter circuit 307. In one photon detection frame MF, the control pulse RC and the control pulse GATE are repeatedly supplied, and the counter circuit 307 counts the number of times that the APD 301 detects a photon. Also, one photon detection frame MF may be a frame that calculates the logical sum of the output of the APD 301 and forms a 1-bit image. In this case, if the APD 301 detects a photon at least once during the period T4 of the photon detection frame MF, the value is 1, and if no photon is detected, the value is 0. The counter circuit 307 includes a memory for holding 1-bit information, and holds a 1 for the MF that detects a photon. When the MF is updated, the counter of the counter circuit 307 is incremented and the 1-bit memory is reset.

[0035] FIG. 5(a) is a diagram showing an example of operation in one ranging frame SF. In each subframe GF, the white portion indicates the timing when the detection operation is performed, and the black portion indicates a non-detection period. It can be seen that the detection operation is performed at different timings from the irradiation of light from the light source 111 depending on the subframe GF. In the example shown in FIG. 5(a), it is shown that the light reflected by the object 110 is detected in subframe GF15. The processing circuit 308 transmits the signal (count value) obtained in each subframe GF to the arithmetic circuit 105, so that the arithmetic circuit 105 can generate distance information.

[0036] In this embodiment, as described above, the arithmetic circuit 105 can generate one three-dimensional distance image or the like from the obtained distance information by one sequence F. In measuring the distance to an object with low reflectance, the signal (count value) obtained by the detection operation is small with only the signal obtained by one operation of the distance measurement frame SF, and there is a possibility that the S / N ratio cannot be obtained. Therefore, in this embodiment, in one sequence F, the operation of the distance measurement frame SF is repeated multiple times. This improves the accuracy of detecting reflected light, and as a result, it is possible to improve the accuracy of distance measurement. However, when the distance measurement frame F is repeated in one sequence F, there is a possibility that power consumption will increase due to the repetition of the above-mentioned recharge operation.

[0037] Therefore, in this embodiment, a stop control circuit 309 is provided in the distance measurement circuit 300 as shown in Fig. 3. The stop control circuit 309 generates a stop signal SS when a plurality of signals obtained by the detection operation of each of a plurality of subframes GF in a plurality of distance measurement frames SF satisfy a predetermined condition. As described above, the "multiple signals" obtained by the detection operation of each of a plurality of subframes GF are count values ​​generated by the processing circuit 308 at each timing when the detection operation is performed. For example, the multiple white circles shown in the count values ​​in Fig. 5(a) correspond to the "multiple signals".

[0038] As described above, distance measurement of an object with low reflectance is taken into consideration. In this case, the stop control circuit 309 may generate the stop signal SS based on a plurality of signal values ​​obtained by accumulating the signal values ​​of a plurality of signals obtained in each of a plurality of distance measurement frames SF for each of a plurality of pixels 204 for each of a plurality of subframes GF. The accumulation of the signal values ​​for each subframe GF may be performed by the processing circuit 308. For example, when one or more signal values ​​of the plurality of signals are equal to or greater than a predetermined threshold, the stop control circuit 309 may generate the stop signal SS as a predetermined condition is satisfied. In other words, it can be said that the stop control circuit 309 generates the stop signal SS in response to the acquisition of data for determining the distance (data for generating distance information).

[0039] The stop signal SS is, for example, a low-level signal supplied to the gate elements 305 and 306 via a signal line 310 shown in FIG. 3. When the stop signal SS is supplied to the gate element 305, the above-mentioned recharge operation is not performed regardless of the level of the control pulse RC. That is, in each of the multiple pixels 204, in a ranging frame SF after the stop signal SS is supplied from the stop control circuit 309 among the multiple ranging frames SF, a reverse bias is not applied to the APD 301, and the detection operation is not performed. This makes it possible to suppress power consumption in the ranging frame SF after sufficient data is obtained to generate distance information.

[0040] FIG. 6 shows an example of operation focusing on one pixel 204. Since none of the signal values ​​of the multiple signals obtained in the ranging frame SF1 reaches a predetermined threshold, the stop control circuit 309 does not generate a stop signal SS. It can be said that the stop control circuit 309 judges whether to generate a stop signal SS. Since the stop signal SS is not generated, a detection operation (white part of subframe GF) is also performed in the ranging frame SF2 next to the ranging frame SF1. The detection operation of the ranging frame SF2 causes the integrated values ​​of the signals in subframes GF15 and GF25 out of the multiple signal values ​​obtained by integrating the multiple signals obtained in the ranging frames SF1 and SF2 for each subframe GF to reach a predetermined threshold. Therefore, the stop control circuit 309 generates a stop signal SS. As a result, when the stop signal SS is supplied to the pixel 204 shown in FIG. 6, the pixel 204 does not perform a detection operation as shown in the ranging frame SFm. As a result, the detection operation is stopped, and power consumption can be reduced. The stop control circuit 309 may determine whether or not to generate a stop signal SS each time a ranging frame SF ends, as shown in Fig. 6. Alternatively, for example, after generating the stop signal SS, the stop control circuit 309 may continue to supply the stop signal SS until one sequence F ends without making a determination.

[0041] When the stop signal SS is generated by the detection operation of the ranging frame SF2, the stop signal SS may be supplied to the pixel 204 during the ranging frame SF3, for example. In that case, in the configuration of the pixel 204 shown in Fig. 3, the detection operation is stopped from the subframe of the ranging frame SF3 at the timing when the stop signal SS is supplied. Furthermore, from the ranging frame SF4 onwards, which is subsequent to the ranging frame SF3 to which the stop signal SS is supplied from the stop control circuit 309, the detection operation is no longer performed.

[0042] When multiple signals having one peak value as shown in FIG. 5(a) or FIG. 6 are obtained, the predetermined condition for the stop control circuit 309 to generate the stop signal SS may be when one or more of the multiple signal values ​​are equal to or greater than a predetermined threshold value, as described above. The one or more signal values ​​may be one peak value. Since the signal value exceeds the predetermined threshold value, it can be determined that data for generating distance information has been obtained. In addition, for example, the threshold value may be set in consideration of the difference between the floor noise and the peak value of multiple signals obtained by the detection operation. The distance measuring device 100 may be configured so that the user can set the threshold value appropriately. As a result, the stop signal SS is generated at an appropriate timing even in an environment with strong external light and large floor noise, and distance measurement accuracy can be improved.

[0043] The stop control circuit 309 may include a comparison circuit that simply compares a predetermined threshold value with a plurality of signal values. When any of the plurality of signal values ​​exceeds the threshold value, the stop control circuit 309 generates a stop signal SS. For example, the stop control circuit 309 may detect a signal value to be compared with the threshold value based on a first derivative value of a histogram (shown by a line graph of a plurality of signals (a plurality of white circles) of count values ​​in FIG. 5(a)) obtained from the plurality of signal values. In other words, the signal value to be compared with the threshold value can be obtained from the rising edge of the histogram or the falling edge of the histogram (after exceeding a predetermined value).

[0044] The predetermined condition for the stop control circuit 309 to generate the stop signal SS is not limited to the comparison between the peak value and the threshold value as described above. For example, the stop control circuit 309 may generate the stop signal SS when the similarity between the waveform of a histogram obtained from a plurality of signal values ​​and a predetermined waveform is within a predetermined range. The predetermined waveform may be an expected waveform generated in advance using a simulation or the like. The predetermined waveform for comparing the similarity may be an appropriate waveform selected by the user from a plurality of simulation waveforms depending on the specifications of the distance measuring device 100 and the environment in which distance measuring is performed, or an appropriate waveform may be automatically selected by the distance measuring device 100 (for example, the stop control circuit 309).

[0045] Also, instead of one peak value as shown in FIG. 5(a), a broad peak may be obtained over multiple subframes as shown in FIG. 5(b). Even in that case, for example, the stop control circuit 309 may generate a stop signal SS when a set threshold is exceeded by simply comparing a predetermined threshold with multiple signal values. Also, when a histogram as shown in FIG. 5(b) is obtained, one or more signal values ​​to be compared with the threshold may be detected based on the first differential value (rising and falling) of the histogram, and the detected one or more signal values ​​may be compared with the threshold. Also, for example, the stop control circuit 309 may detect one or more signal values ​​to be compared with the threshold from inflection points of the rising and falling of the histogram based on the second differential value of the histogram obtained from the multiple signal values. When the first differential value or the second differential value is used, the stop signal SS is generated at an appropriate timing compared to the case where the distance measurement is performed using the peak value, and the distance measurement accuracy may be improved. As a result, the one or more signal values ​​to be compared with the threshold may include the peak value of the multiple signal values. As described above, the stop signal SS may be generated based on a comparison between a waveform of a histogram obtained from a plurality of signal values ​​and a predetermined waveform.

[0046] 3, the stop control circuit 309 may be provided for each of the multiple pixels 204. In this case, the stop control circuit 309 may generate a stop signal for each of the multiple pixels 204 based on multiple signals obtained from each pixel 204. Therefore, in sequence F in which distance measurement is performed, power consumption for each pixel 204 can be suppressed.

[0047] However, the stop control circuit 309 is not limited to being arranged in each pixel 204. FIG. 7 is a block diagram showing a modified example of the distance measuring device 100 shown in FIG. 1. FIG. 8 is a diagram showing a configuration example of the pixel 204 arranged in the distance measuring device 100 shown in FIG. 7. In the configuration shown in FIG. 7 and FIG. 8, the distance measuring circuit 400 including the processing circuit 308 and the stop control circuit 309 is arranged outside the light receiving unit 102 including the pixel unit 201 (see FIG. 2) in which a plurality of pixels 204 are arranged. In addition, the counter circuit 307 of the distance measuring circuit 300 shown in FIG. 3 is arranged in the pixel 204 as shown in FIG. 8. The other configurations may be the same as those described above, and therefore the description of the similar configurations will be omitted as appropriate.

[0048] 7 and 8, the signal counted by the counter circuit 307 is supplied to the processing circuit 308 of the distance measuring circuit 400 via the signal line 213, and the same processing as described above is performed. Also, the stop control circuit 309 generates a stop signal SS in the same manner as described above based on the signal values ​​of the multiple signals generated by the processing circuit 308.

[0049] 7 and 8, the stop control circuit 309 may generate a stop signal SS for each of the pixels 204 based on a plurality of signals obtained from each pixel 204. This reduces power consumption for each pixel 204, thereby realizing low power consumption of the distance measuring device 100.

[0050] However, when the stop signal SS is generated for each pixel 204, the circuit configuration may become complicated, such as the arrangement of the signal line 310 for individually supplying the stop signal SS to each pixel 204. Therefore, the stop control circuit 309 may generate the stop signal SS based on a plurality of signals obtained from the pixels 204 arranged in a predetermined region among the plurality of pixels 204. For example, the stop control circuit 309 may supply the stop signal SS to all the pixels 204 arranged in the predetermined region when a plurality of signals obtained from a predetermined number of the pixels 204 arranged in the predetermined region satisfy a predetermined condition for generating the stop signal SS. By adopting a configuration in which the stop signal SS is supplied for each predetermined region, the circuit configuration between the stop control circuit 309 and the pixel unit 201 can be simplified compared to the case in which the stop signal SS is supplied for each pixel 204.

[0051] For example, the pixel unit 201 is divided into an appropriate number of regions, such as four. For each divided region, when signals obtained from 90% or more of the pixels 204 arranged in the divided region satisfy a predetermined condition for generating a stop signal SS, the stop signal SS is supplied to the pixels 204 in the region. This makes it possible to reduce power consumption for each divided region in the sequence F for performing distance measurement. The pixels 204 that output signals that satisfy the predetermined condition for generating the stop signal SS are not limited to 90% or more of the pixels 204 arranged in each region, and may be 50% or more, 60% or more, 70% or more, or 80% or more.

[0052] Also, for example, the stop control circuit 309 may supply the stop signal SS to all of the pixels arranged in the pixel unit 201 when a plurality of signals obtained from a predetermined number of pixels 204 among the pixels 204 arranged in a predetermined region satisfy a predetermined condition for generating the stop signal SS. For example, a user sets a region of interest as a predetermined region. The region of interest may be one or more of the regions obtained by dividing the pixel unit 201 into an appropriate number. Also, a user may set one or more arbitrary regions as the region of interest. For example, when signals obtained from 90% or more of the pixels 204 arranged in the region of interest satisfy a predetermined condition for generating the stop signal SS, the stop signal SS is supplied to all the pixels 204. Thereby, it is possible to generate distance information in the region of interest set by the user, and it is possible to suppress power consumption by not performing a detection operation more than necessary. The pixels 204 that output signals that satisfy the predetermined conditions for generating the stop signal SS are not limited to 90% or more of the pixels 204 arranged in the attention area, and may be 50% or more, 60% or more, 70% or more, or 80% or more. Also, for example, the distance measuring device 100 may be configured so that the user can select the ratio of the pixels 204 that output signals that satisfy the predetermined conditions for generating the stop signal SS.

[0053] The operation of suppressing power consumption in the distance measuring device 100 has been described above. However, the configuration of the distance measuring device 100 is not limited to the above. In the above, the APD 301 is used as the photoelectric conversion element, but a photodiode such as a PIN diode may be used as the photoelectric conversion element. In this case, the counter circuit 307 may not be provided, and a signal may be directly supplied from the PIN diode to the processing circuit 308. In the above, the count value is used as the signal value of the multiple signals, but when a photodiode is used as the photoelectric conversion element, the voltage value acquired at the timing of each detection operation may be used as the signal value of the multiple signals.

[0054] An application example of the distance measuring device 100 according to the above embodiment will be described below. FIG. 9 is a schematic diagram of an equipment EQP equipped with the distance measuring device 100. The distance measuring device 100 may be a semiconductor chip having a stacked structure in which a pixel unit 201 in which pixels 204 are arranged is provided. As shown in FIG. 9, the distance measuring device 100 is accommodated in a semiconductor package PKG. The package PKG may include a base on which the distance measuring device 100 is fixed, a cover such as glass facing the distance measuring device 100, and a conductive connection member such as a bonding wire or bump that connects a terminal provided on the base to a terminal provided on the distance measuring device 100. The equipment EQP may further include at least one of a control device CTRL, a processing device PRCS, a display device DSPL, and a memory device MMRY.

[0055] The optical system OPT forms an image on the pixel unit 201 and may be, for example, a lens, a shutter, or a mirror. The control device CTRL controls the operation of the distance measuring device 100 and may be, for example, a semiconductor device such as an ASIC. The processing device PRCS processes a signal output from the distance measuring device 100 and may be, for example, a semiconductor device such as a CPU or an ASIC. The display device DSPL may be an EL display device or a liquid crystal display device that displays data obtained by the distance measuring device 100. The memory device MMRY is a magnetic device or a semiconductor device that stores data obtained by the distance measuring device 100. The memory device MMRY may be a volatile memory such as an SRAM or a DRAM, or a non-volatile memory such as a flash memory or a hard disk drive. The mechanical device MCHN may have a moving part or a propulsion part such as a motor or an engine. The mechanical device MCHN also drives parts of the optical system OPT for, for example, zooming, focusing, and shutter operation. In the device EQP, the data output from the distance measuring device 100 is displayed on the display device DSPL, or transmitted to the outside by a communication device (not shown) included in the device EQP. For this reason, the device EQP may include a memory device MMRY and a processing device PRCS.

[0056] The equipment EQP incorporating the distance measuring device 100 can be applied to surveillance cameras, and on-board cameras mounted on transport equipment such as automobiles, railroad cars, ships, aircraft, and industrial robots. In addition, the equipment EQP incorporating the distance measuring device 100 can be applied not only to transport equipment but also to a wide range of equipment that uses object recognition, such as an intelligent transport system (ITS).

[0057] The disclosure of this specification includes the following ranging devices and instruments:

[0058] (Item 1) A distance measuring device comprising: a plurality of pixels, each of which includes a photoelectric conversion element; and an arithmetic circuit for generating distance information based on signals obtained by the plurality of pixels, the sequence for generating the distance information includes a plurality of ranging frames; each of the plurality of distance measurement frames includes a plurality of subframes having different times between irradiation of light by a light source and a period during which a detection operation is performed to detect the light reflected by an object by applying a reverse bias to the photoelectric conversion element; a stop control circuit that generates a stop signal when a plurality of signals obtained by the detection operation of each of the plurality of subframes in the plurality of ranging frames satisfy a predetermined condition, a stop control circuit for stopping the detection operation of each of the plurality of pixels during a distance measurement frame among the plurality of distance measurement frames after the stop signal is supplied from the stop control circuit;

[0059] (Item 2) 2. The distance measuring device according to item 1, wherein the stop control circuit generates the stop signal for each of the plurality of pixels based on the plurality of signals obtained at each pixel.

[0060] (Item 3) 3. The distance measuring device according to item 2, wherein the stop control circuit is arranged in each of the plurality of pixels.

[0061] (Item 4) 2. The distance measuring device according to item 1, wherein the stop control circuit generates the stop signal based on the plurality of signals obtained from pixels arranged in a predetermined area among the plurality of pixels.

[0062] (Item 5) The distance measuring device described in item 4, characterized in that the stop control circuit supplies the stop signal to all pixels arranged in the specified area when the multiple signals obtained from a predetermined number of pixels among the pixels arranged in the specified area satisfy the predetermined condition.

[0063] (Item 6) The distance measuring device described in item 4, characterized in that the stop control circuit supplies the stop signal to all of the plurality of pixels when the plurality of signals obtained from a predetermined number of pixels among the pixels arranged in the predetermined area satisfy the predetermined condition.

[0064] (Item 7) 7. The distance measuring device according to any one of items 4 to 6, wherein the stop control circuit is arranged outside a pixel section in which the plurality of pixels are arranged.

[0065] (Item 8) The distance measuring device according to any one of items 1 to 7, characterized in that the stop control circuit generates the stop signal for each of the plurality of pixels based on a plurality of signal values ​​obtained by accumulating the signal values ​​of the plurality of signals obtained in each of the plurality of distance measuring frames for each of the plurality of subframes.

[0066] (Item 9) 9. The distance measuring device according to item 8, wherein the predetermined condition includes a case where one or more of the plurality of signal values ​​is equal to or greater than a predetermined threshold value.

[0067] (Item 10) 10. The distance measuring device according to item 9, wherein the stop control circuit detects the one or more signal values ​​based on a first differential value of a histogram obtained from the plurality of signal values.

[0068] (Item 11) 11. The distance measuring device according to item 9 or 10, wherein the stop control circuit detects the one or more signal values ​​based on a second derivative value of a histogram obtained from the plurality of signal values.

[0069] (Item 12) 12. The distance measuring device according to any one of items 9 to 11, wherein the one or more signal values ​​include a peak value of the plurality of signal values.

[0070] (Item 13) A distance measuring device described in any one of items 8 to 12, characterized in that the specified condition includes a case where the similarity between the waveform of a histogram obtained from the multiple signal values ​​and a specified waveform is within a specified range.

[0071] (Item 14) 14. The distance measuring device according to any one of items 1 to 13, wherein the photoelectric conversion element includes an avalanche photodiode.

[0072] (Item 15) A distance measuring device according to any one of items 1 to 14, a processing device for processing a signal output from the distance measuring device; An apparatus comprising:

[0073] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0074] 100: distance measuring device, 105: calculation circuit, 204: pixel, 309: stop control circuit, F: sequence, GF: subframe, SF: distance measuring frame

Claims

1. A distance measuring device comprising: a plurality of pixels, each of which includes a photoelectric conversion element; and an arithmetic circuit for generating distance information based on signals obtained by the plurality of pixels, the sequence for generating the distance information includes a plurality of ranging frames; each of the plurality of distance measurement frames includes a plurality of subframes having different times between irradiation of light by a light source and a period during which a detection operation is performed to detect the light reflected by an object by applying a reverse bias to the photoelectric conversion element; a stop control circuit that generates a stop signal when a plurality of signals obtained by the detection operation of each of the plurality of subframes in the plurality of ranging frames satisfy a predetermined condition, a stop control circuit for stopping the detection operation of each of the plurality of pixels during a distance measurement frame among the plurality of distance measurement frames after the stop signal is supplied from the stop control circuit;

2. 2. The distance measuring device according to claim 1, wherein the stop control circuit generates the stop signal for each of the plurality of pixels based on the plurality of signals obtained at each pixel.

3. 3. The distance measuring device according to claim 2, wherein the stop control circuit is provided for each of the plurality of pixels.

4. 2. The distance measuring device according to claim 1, wherein the stop control circuit generates the stop signal based on the plurality of signals obtained from pixels arranged in a predetermined area among the plurality of pixels.

5. 5. The distance measuring device according to claim 4, wherein the stop control circuit supplies the stop signal to all pixels arranged in the specified region when the plurality of signals obtained from a predetermined number of pixels among the pixels arranged in the specified region satisfy the predetermined condition.

6. 5. The distance measuring device according to claim 4, wherein the stop control circuit supplies the stop signal to all of the plurality of pixels when the plurality of signals obtained from a predetermined number of pixels among the pixels arranged in the predetermined area satisfy the predetermined condition.

7. 5. The distance measuring device according to claim 4, wherein the stop control circuit is arranged outside a pixel section in which the plurality of pixels are arranged.

8. The distance measuring device according to claim 1, characterized in that the stop control circuit generates the stop signal for each of the plurality of pixels based on a plurality of signal values ​​obtained by accumulating the signal values ​​of the plurality of signals obtained in each of the plurality of distance measuring frames for each of the plurality of subframes.

9. 9. The distance measuring device according to claim 8, wherein the predetermined condition includes a case where one or more of the plurality of signal values ​​is equal to or greater than a predetermined threshold value.

10. 10. The distance measuring device according to claim 9, wherein the stop control circuit detects the one or more signal values ​​based on a first differential value of a histogram obtained from the plurality of signal values.

11. 10. The distance measuring device according to claim 9, wherein the stop control circuit detects the one or more signal values ​​based on a second derivative value of a histogram obtained from the plurality of signal values.

12. The distance measuring device according to claim 9 , wherein the one or more signal values ​​include a peak value of the plurality of signal values.

13. 9. The distance measuring device according to claim 8, wherein the predetermined condition includes a case where a similarity between a waveform of a histogram obtained from the plurality of signal values ​​and a predetermined waveform is within a predetermined range.

14. 2. The distance measuring device according to claim 1, wherein the photoelectric conversion element includes an avalanche photodiode.

15. A distance measuring device according to any one of claims 1 to 14, a processing device for processing a signal output from the distance measuring device; An apparatus comprising:

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