Photoelectric conversion device

Abstract

To provide a photoelectric conversion device that can acquire accurate distance information.SOLUTION: A photoelectric conversion device has: a light receiving unit that generates a light receiving signal according to incident light through photoelectric conversion; a time-digital conversion unit that periodically performs an operation to output a time count value indicating the time elapsed from light emission from a light source device until input of the light receiving signal, every time a predetermined period elapses within a first distance measurement period; and a comparison unit that outputs a comparison result based on a first time count value that is the time count value obtained from the time-digital conversion unit at a first time included in the first distance measurement period, and a second time count value that is the time count value at a second time included in the first distance measurement period. The photoelectric conversion device performs processing based on the comparison result.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a photoelectric conversion device. [Background technology]

[0002] Patent Document 1 discloses a distance measuring device that measures the distance to an object by repeatedly emitting light from a light source and receiving light, including reflected light from the object, with a light receiving element. Patent Document 1 also discloses a process for generating a frequency distribution based on a count value indicating the time from light emission to the incidence of a photon and a weight determined based on the number of reactions of the light receiving element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-001764 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a photoelectric conversion device such as that described in Patent Document 1, there are cases where it is required to obtain distance information with higher accuracy.

[0005] An object of the present invention is to provide a photoelectric conversion device capable of acquiring highly accurate distance information. [Means for solving the problem]

[0006] According to one disclosure of the present specification, there is provided a photoelectric conversion device characterized by having a light receiving unit that generates a light receiving signal corresponding to incident light by photoelectric conversion, a time-to-digital conversion unit that periodically performs an operation of outputting a time count value indicating the elapsed time from the light emission of a light source device to the input of the light receiving signal every time a predetermined period has elapsed in one ranging period, a comparison unit that outputs a comparison result based on a first time count value, which is a time count value obtained from the time-to-digital conversion unit in a first hour included in the one ranging period, and a second time count value, which is a time count value in a second hour included in the one ranging period, a weight determination unit that outputs a weight value based on the comparison result, and a frequency distribution generation unit that uses the weight value to add frequencies and generates a frequency distribution of the time count values ​​in the one ranging period.

[0007] According to one disclosure of the present specification, a photoelectric conversion device is provided that includes a light receiving unit that generates a light receiving signal corresponding to incident light by photoelectric conversion, a time-to-digital conversion unit that periodically performs an operation of outputting a time count value indicating the elapsed time from the light emission of a light source device to the input of the light receiving signal every time a predetermined period has elapsed in one ranging period, and a comparison unit that performs a comparison based on a first time count value output from the time-to-digital conversion unit at a first time included in the one ranging period and a second time count value output from the time-to-digital conversion unit at a second time included in the one ranging period and prior to the first time, wherein the comparison unit outputs either the first time count value or the second time count value as a time count value used to generate a frequency distribution in which a plurality of time intervals are associated with light receiving count values ​​based on the number of times the time count value corresponding to the corresponding time interval is output, based on the result of the comparison. Effect of the Invention

[0008] According to the present invention, a photoelectric conversion device capable of acquiring highly accurate distance information is provided. [Brief description of the drawings]

[0009] [Figure 1]1 is a block diagram showing a schematic configuration of a distance measuring device according to a first embodiment. [Diagram 2] 2 is a block diagram showing the configuration of a light receiving section and a distance measuring section according to the first embodiment. FIG. [Diagram 3] 1 is a diagram showing the configuration and operation of a pixel according to a first embodiment; [Figure 4] 2 is a block diagram showing the configuration of a distance measuring unit according to the first embodiment. FIG. [Diagram 5] 4 is a graph showing an example of measurement of a time count value according to the first embodiment. [Figure 6] 4 is a table showing an example of setting weight values ​​according to the first embodiment. [Figure 7] 4 is a graph showing weighting in generating a frequency distribution according to the first embodiment. [Figure 8] FIG. 11 is a block diagram showing the configuration of a distance measuring unit according to a second embodiment. [Figure 9] 13 is a table showing an example of setting weight values ​​according to the second embodiment. [Figure 10] FIG. 11 is a block diagram showing the configuration of a distance measuring unit according to a third embodiment. [Figure 11] 13 is a table showing an example of the operation of a comparison section and a retention selection section according to the third embodiment. [Figure 12] FIG. 13 is a schematic diagram of a light detection system according to a fourth embodiment. [Figure 13] FIG. 13 is a schematic diagram of a device according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The same elements or corresponding elements in multiple drawings are denoted by the same reference numerals, and the description thereof may be omitted or simplified.

[0011] [First embodiment] Fig. 1 is a block diagram showing a schematic configuration of a distance measuring device 1 according to the first embodiment. As shown in Fig. 1, the distance measuring device 1 has a light receiving device 2, a light source device 3, and a signal processing device 4. The light receiving device 2 has a light receiving unit 20 and an optical system 26. The light source device 3 has a light emitting unit 30. The signal processing device 4 has a control unit 40 and a distance measuring unit 41.

[0012] It should be noted that the configuration of the distance measuring device 1 shown in this embodiment is an example, and the configuration of the distance measuring device 1 is not limited to the illustrated configuration. For example, the light source device 3 may be disposed outside the distance measuring device 1. Even in this case, the light emitting unit 30 operates in response to a control signal from the control unit 40. The configuration and operation of the distance measuring device 1 described in this embodiment can also be applied to other photoelectric conversion devices that generate signals by photoelectric conversion. Examples of photoelectric conversion devices include an imaging device and a focus detection device.

[0013] The distance measuring device 1 is a device that measures the distance to the object X to be measured using technology such as LiDAR (Light Detection And Ranging). The distance measuring device 1 measures the distance from the distance measuring device 1 to the object X based on the time difference between when light is emitted from the light source device 3 and when the reflected light from the object X is received by the light receiving device 2. The distance measuring device 1 can also measure the distance at multiple points two-dimensionally by emitting light to a predetermined distance measuring range including the object X and receiving the reflected light by a pixel array. This allows the distance measuring device 1 to measure and output the distribution of the distance from the distance measuring device 1 to the object X in the distance measuring range.

[0014] The light received by the light receiving device 2 includes ambient light such as sunlight, disturbance light from other light sources, and the like, in addition to the reflected light from the object X. The distance measuring device 1 repeatedly performs an operation of measuring the time difference between the emission of light and the reception of the reflected light as a time count value multiple times. The distance measuring device 1 then generates a frequency distribution in which the light reception count value of the pulse based on the incident light is associated with each of the multiple time count values. The distance measuring device 1 then performs distance measurement with reduced influence of ambient light, etc., by using a method of determining that the reflected light is incident during the time interval of the time count value corresponding to the maximum light reception count value.

[0015] The signal processing device 4 may include a processor that performs arithmetic processing of digital signals, a memory that stores digital signals, and a control circuit that controls the operations of the light receiving device 2 and the light source device 3. The control unit 40 outputs a control signal that controls the light emission timing of the light emitting unit 30, a control signal that controls the operation timing of the light receiving unit 20, and a control signal that controls the operation timing of the distance measuring unit 41.

[0016] The light source device 3 is a device that emits light such as laser light to the outside of the distance measuring device 1. The light emitting unit 30 of the light source device 3 includes, for example, a semiconductor laser diode as a light source. The light emitting unit 30 emits laser light having a predetermined pulse width based on a control signal from the control unit 40. This laser light is diffused by an optical system such as a diffusion plate, and is irradiated to a predetermined range.

[0017] The optical system 26 includes optical elements such as lenses that form an image of incident light on the light receiving unit 20. Reflected light generated by the laser light emitted from the light emitting unit 30 being reflected by the object X forms an image on the light receiving unit 20 via the optical system 26.

[0018] The light receiving unit 20 is, for example, a photoelectric conversion device including an avalanche photodiode (hereinafter referred to as APD) as a photoelectric conversion element. In this case, when one photon is incident on the APD and an electric charge is generated, one pulse is generated by avalanche multiplication. However, the light receiving unit 20 may be, for example, a photoelectric conversion element using another photodiode.

[0019] The distance measuring unit 41 generates a frequency distribution based on the electrical signal output from the light receiving unit 20. The distance measuring unit 41 also generates distance information indicating the distance from the distance measuring device 1 to the object X based on the frequency distribution.

[0020] 2 is a block diagram showing the configuration of the light receiving unit 20 and the distance measuring unit 41 according to the first embodiment. The light receiving unit 20 has a pixel array 21 and a pixel driving unit 22. The distance measuring unit 41 has a column processing unit 410, a transfer unit 420, and a distance calculation unit 430.

[0021] In the pixel array 21, a plurality of pixels 210 are arranged in a plurality of rows and a plurality of columns. Each of the plurality of pixels 210 has a photoelectric conversion unit 211 including a photoelectric conversion element, and a pixel circuit 212. The photoelectric conversion unit 211 generates a signal according to incident light. The signal generated by the photoelectric conversion unit 211 of each pixel 210 is shaped into a pulse signal in the pixel circuit 212. The pixel circuit 212 outputs the pulse signal to the column processing unit 410 via a signal line 24 arranged for each column of the pixel array 21.

[0022] The pixel driving unit 22 supplies a control signal to each of the plurality of pixel circuits 212 based on a control signal supplied from the control unit 40. The pixel driving unit 22 supplies a control signal to each pixel circuit 212 for each row via a driving line 23 provided for each row of the pixel array 21. The pixel driving unit 22 may include logic circuits such as a shift register and an address decoder. In this way, the pixel driving unit 22 selects a row for outputting a signal from the pixel circuit 212 to the column processing unit 410.

[0023] The column processing units 410 are arranged to correspond to each column of the pixel array 21. A timing control signal such as a clock signal is input from the control unit 40 to each of the multiple column processing units 410. The column processing units 410 are signal processing circuits that perform processing such as time-to-digital conversion on the pulse signals output from the pixel circuits 212. The signals output from the column processing units 410 for each column are input to the transfer unit 420.

[0024] The transfer unit 420 is a transfer circuit that sequentially transfers the signals of each column output from the column processing unit 410 to the distance calculation unit 430 based on a control signal supplied from the control unit 40.

[0025] The distance calculation unit 430 is a signal processing circuit that processes the signal input from the transfer unit 420. The distance calculation unit 430 may be arranged on the semiconductor chip on which the column processing unit 410 is arranged, or may be arranged on a different semiconductor chip (for example, a signal processing circuit chip such as a digital front end).

[0026] 2 shows a circuit configuration in which the column processing unit 410 processes output signals from multiple pixels 210 in the same column, and the distance calculation unit 430 processes output signals from all pixels 210 in the pixel array 21, but the configuration is not limited to this. For example, a signal processing circuit equivalent to the column processing unit 410 may be arranged corresponding to each of the multiple pixels 210, and a signal processing circuit equivalent to the distance calculation unit 430 may be arranged corresponding to each of the multiple pixels 210. Furthermore, a signal processing circuit equivalent to the distance calculation unit 430 may be arranged corresponding to each column of the pixel array 21, similar to the column processing unit 410.

[0027] 2, the pixel array 21 includes a plurality of pixels 210 arranged two-dimensionally, but is not limited thereto. For example, the arrangement of the plurality of pixels 210 may be one-dimensional. Also, the light receiving unit 20 may include only a single pixel 210.

[0028] Furthermore, the function of the pixel circuit 212 does not necessarily have to be provided for each pixel 210. For example, one pixel circuit 212 may be shared by a plurality of pixels 210. In this case, the pixel circuit 212 provides a signal processing function to the plurality of pixels 210 by sequentially processing signals output from the plurality of photoelectric conversion units 211.

[0029] Fig. 3(a) is a diagram showing the configuration of a pixel 210 according to the first embodiment. Figs. 3(b) and 3(c) are diagrams showing the operation of the pixel 210. The pixel 210 has a photoelectric conversion unit 211, a quenching element 213, a waveform shaping unit 214, and a selection circuit 215. The quenching element 213, the waveform shaping unit 214, and the selection circuit 215 correspond to the pixel circuit 212 shown in Fig. 2.

[0030] The photoelectric conversion unit 211 is an APD, and generates charges according to incident light by photoelectric conversion. An electric potential VL is supplied to the anode of the photoelectric conversion unit 211. The cathode of the photoelectric conversion unit 211 is connected to a first terminal of the quench element 213 and an input terminal of the waveform shaping unit 214. A electric potential VH higher than the electric potential VL supplied to the anode is supplied to a second terminal of the quench element 213. As a result, a reverse bias voltage is supplied to the anode and cathode of the photoelectric conversion unit 211 such that the photoelectric conversion unit 211 performs an avalanche multiplication operation. When electric charges are generated by incident light in the photoelectric conversion unit 211 to which the reverse bias voltage is supplied, the electric charges cause avalanche multiplication, and an avalanche current is generated.

[0031] There are two operation modes when a reverse bias voltage is supplied to the photoelectric conversion unit 211: Geiger mode and linear mode. The Geiger mode is a mode in which the photoelectric conversion unit 211 operates with a potential difference between the anode and the cathode that is greater than the breakdown voltage, and the linear mode is a mode in which the photoelectric conversion unit 211 operates with a potential difference between the anode and the cathode that is close to or less than the breakdown voltage.

[0032] An APD operated in Geiger mode is called a SPAD (Single Photon Avalanche Diode). In this case, for example, the potential VL is −30 V and the potential VH is 1 V. The photoelectric conversion unit 211 may be operated in either a linear mode or a Geiger mode. In the case of a SPAD, the potential difference is larger than that of an APD in linear mode, and the effect of avalanche multiplication is prominent, so a SPAD is preferable.

[0033] The quench element 213 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication. The quench element 213 suppresses the potential supplied to the photoelectric conversion unit 211 to suppress avalanche multiplication (quench operation). The quench element 213 also returns the potential supplied to the photoelectric conversion unit 211 to the potential VH by passing a current corresponding to the potential drop caused by the quench operation (recharge operation). The quench element 213 may be a resistive element or a MOS transistor. When the quench element 213 is a MOS transistor, a constant potential may be input to the gate of the MOS transistor. When the quench element 213 is a MOS transistor, a recharge operation may be performed at a constant cycle by inputting a periodic pulse signal to the gate of the MOS transistor.

[0034] The waveform shaping unit 214 shapes the potential change of the cathode of the photoelectric conversion unit 211 obtained when a photon is detected, and outputs a pulse signal. For example, an inverter circuit is used as the waveform shaping unit 214. Although an example using one inverter as the waveform shaping unit 214 is shown in Fig. 3(a), the waveform shaping unit 214 may be a circuit in which a plurality of inverters are connected in series, or may be another circuit having a waveform shaping effect.

[0035] 2 supplies a control signal to the selection circuit 215 via the drive line 23. In response to this control signal, the selection circuit 215 switches between electrical connection and non-connection between the output terminal of the waveform shaping unit 214 and the signal line 24. The selection circuit 215 may include, for example, a switch, a buffer circuit, etc.

[0036] Next, the operation of the pixel 210 will be described with further reference to Figures 3(b) and 3(c). As shown in Figure 3(a), a connection node between the photoelectric conversion unit 211, the quenching element 213, and the input terminal of the waveform shaping unit 214 is referred to as node A. Also, as shown in Figure 3(a), a connection node between the output terminal of the waveform shaping unit 214 and the selection circuit 215 is referred to as node B.

[0037] FIG. 3(b) is a graph showing the time change of the potential of node A in FIG. 3(a). FIG. 3(c) is a graph showing the time change of the potential of node B in FIG. 3(a). In the period from time t0 to time t1, a voltage of VH-VL is applied to the photoelectric conversion unit 211 in FIG. 3(a). When a photon is incident on the photoelectric conversion unit 211 at time t1, avalanche multiplication occurs in the photoelectric conversion unit 211. As a result, an avalanche current flows through the quench element 213, and the potential of node A drops. Thereafter, the amount of potential drop becomes larger, and the voltage applied to the photoelectric conversion unit 211 gradually decreases. Then, at time t2, the avalanche multiplication in the photoelectric conversion unit 211 stops. As a result, the potential of node A does not drop below a certain value. Thereafter, during the period from time t2 to time t3, a current flows to node A from the node at potential VH to compensate for the potential drop, and at time t3, node A settles to its original potential.

[0038] In the above process, the potential of node B becomes high level during the period when the potential of node A is lower than a certain threshold. In this way, the waveform of the drop in the potential of node A caused by the incidence of a photon is shaped by the waveform shaping unit 214 and output as a pulse to node B. This pulse signal is input to the column processing unit 410 via the selection circuit 215 and the signal line 24.

[0039] Next, the configuration and operation of the distance measuring unit 41 will be described in more detail. Fig. 4 is a block diagram showing the configuration of the distance measuring unit 41 according to this embodiment. Fig. 4 shows functional blocks of one pixel 210 out of the multiple pixels 210, one column processing unit 410 corresponding to the one pixel 210, and a distance calculation unit 430. The column processing unit 410 has a time-to-digital conversion unit (TDC) 411, a holding unit 412, and a comparison unit 413. The distance calculation unit 430 has a weight determination unit 431 and a frequency distribution generation unit 432.

[0040] The pixels 210 of the light receiving unit 20 output a pulse signal, which is a light receiving signal corresponding to the incident light, to the column processing unit 410. The pulse signal output from the pixels 210 is input to the time digital conversion unit 411. The time digital conversion unit 411 counts the time by counting the pulses of the clock signal input from the control unit 40, and generates a time count value whose value increases by one every time a predetermined time elapses. The time digital conversion unit 411 starts counting the time in synchronization with the light emission timing of the light emission unit 30, and outputs the time count value at the timing when the pulse signal indicating the incident light is input from the pixel 210 to the holding unit 412 and the comparison unit 413. As a result, the time digital conversion unit 411 performs an output operation of a time count value indicating the elapsed time from the light emission of the light emission unit 30 to the input of the pulse signal indicating the incident light.

[0041] The light emission in the light-emitting unit 30 and the light reception in the pixel 210 are performed periodically every time a predetermined period elapses within one ranging period. Therefore, the output operation of the time count value in the time-to-digital conversion unit 411 is also performed periodically every time a predetermined period elapses within one ranging period. Hereinafter, the time count value generated corresponding to the Nth (N is an integer) light emission within one ranging period may be denoted as "TC(N)".

[0042] The holding unit 412 (first holding unit) temporarily holds the time count value output from the time-to-digital conversion unit 411. The holding unit 412 also outputs the held time count value to the comparison unit 413. Thus, the holding unit 412 has a function of temporarily holding a time count value previously output from the time-to-digital conversion unit 411 and outputting the past time count value to the comparison unit 413.

[0043] The comparison unit 413 compares the time count value input from the time-to-digital conversion unit 411 with the time count value input from the holding unit 412. Here, it is assumed that the comparison timing in the comparison unit 413 is after the Nth light emission in one distance measurement period. In this case, the time-to-digital conversion unit 411 outputs the Nth time count value TC(N), and the holding unit 412 outputs the (N-1)th time count value TC(N-1), which is one period before. That is, the comparison unit 413 compares the time count value TC(N) (first time count value) with the time count value TC(N-1) (second time count value). Then, the comparison unit 413 outputs the time count value TC(N) and the comparison result to the weight determination unit 431.

[0044] The time count value in holding unit 412 is updated after the comparison in comparing unit 413 is completed. That is, after the comparison between time count value TC(N) and time count value TC(N-1) is completed as described above, holding unit 412 erases time count value TC(N-1) and holds time count value TC(N).

[0045] The weight determination unit 431 determines a weight value used for weighting the light reception count value in generating the frequency distribution, based on the comparison result input from the comparison unit 413. The weight determination unit 431 outputs the time count value and the determined weight value to the frequency distribution generation unit 432.

[0046] The frequency distribution generating unit 432 generates a frequency distribution based on the time count value and the weight value. The frequency distribution is data in which each time count value is associated with a light receiving count value obtained by counting the number of times the time count value is input. Each time a time count value and a weight value are input, the frequency distribution generating unit 432 updates the frequency distribution by adding a value equal to the number of weight values ​​to the light receiving count value of the time count value.

[0047] When the light emitting unit 30 emits light and the light receiving unit 20 receives light a predetermined number of times within one distance measurement period, the frequency distribution generating unit 432 completes the generation of the frequency distribution. The frequency distribution generating unit 432 generates distance information from the generated frequency distribution using a predetermined algorithm. This algorithm may detect the maximum value of the light receiving count value from the frequency distribution and calculate the distance information from the time count value corresponding to the maximum value. The frequency distribution generating unit 432 may output the frequency distribution as it is without calculating the distance information. In this case, a process of calculating the distance information from the frequency distribution may be performed in an external signal processing device. Also, the weight determining unit 431 may be configured to output the time count value and the weight value to the outside, in which case the external signal processing device has a function of performing the process of the frequency distribution generating unit 432.

[0048] Next, a specific example of the processing performed in the distance measuring unit 41 of this embodiment will be described with reference to Figs. 5 to 7. Fig. 5 is a graph showing an example of measuring the time count value according to this embodiment. The horizontal axis of Fig. 5 indicates the number of times measurements including light emission by the light emitting unit 30 and light reception by the light receiving unit 20 were performed within one distance measurement period. Note that the horizontal axis of Fig. 5 denotes the first measurement as the 0th measurement. The vertical axis of Fig. 5 indicates the time count value obtained in each measurement.

[0049] As described above, the time count value indicates the elapsed time from light emission to light reception in each measurement. Since this elapsed time is proportional to the distance from the distance measuring device 1 to the object X, if the position of the object X is constant, this time count value is expected to be constant in each measurement. However, as shown in FIG. 5, various values ​​of the time count value may actually be measured. This is because various values ​​of the time count value may be measured due to dark counts due to thermally generated charges rather than charges due to incident light, noise due to detection of external light such as sunlight, etc.

[0050] Data points with the maximum time count value (16383), such as the 5th and 7th data points, indicate that no photons were incident until the time count value in the time-to-digital conversion unit 411 reached the maximum value. This indicates that no object X reflecting the emitted light exists within a predetermined distance range. In this way, the distance measuring device 1 of this embodiment can also acquire information indicating the absence of the object X. Note that when the amount of emitted light is small or when the reflectance of the object X is small, the pixel 210 is less likely to detect a photon. Therefore, even if the object X actually exists, the pixel 210 may not be able to detect a photon, and even in such a case, the time count value may become the maximum value. Such photon detection failures occur randomly with a probability according to the amount of incident light, and may become a noise factor in the time count value.

[0051] As described above, since the time count values ​​caused by noise occur randomly, when close time count values ​​are measured consecutively, the probability that these time count values ​​are caused by noise is low. Therefore, when close time count values ​​are measured consecutively, these time count values ​​are likely to properly indicate the distance to the object X or the absence of the object X. Therefore, the weight determination unit 431 of this embodiment reduces the influence of the time count values ​​caused by noise by increasing the weight of the time count values ​​when close time count values ​​are obtained consecutively.

[0052] Fig. 6 is a table showing an example of setting weight values ​​according to this embodiment. In the example of Fig. 6, the comparison unit 413 calculates the absolute difference (absolute value of the difference between two values) between the time count value TC(N) at the time of comparison and the previous time count value TC(N-1) at the time of comparison, and determines whether the calculated absolute difference is equal to or smaller than a threshold value. The comparison unit 413 outputs the comparison result to the weight determination unit 431, and the weight determination unit 431 determines the weight value based on the comparison result.

[0053] 6, when the absolute difference is greater than the threshold, the weight determination unit 431 determines the weight value to be "1" (first weight value) and outputs it to the frequency distribution generation unit 432. When the absolute difference is equal to or less than the threshold, the weight determination unit 431 determines the weight value to be "2" (second weight value) and outputs it to the frequency distribution generation unit 432. The five periods T1 in FIG. 5 indicate output periods of time count values ​​corresponding to a case where an event in which the absolute difference is equal to or less than the threshold occurs only once.

[0054] Moreover, the weight determination unit 431 has a function of storing the number of times that an event in which the absolute difference is equal to or less than the threshold has occurred consecutively up to at least three times. As shown in FIG. 6, when an event in which the absolute difference is equal to or less than the threshold has occurred consecutively two times, the weight determination unit 431 determines the weight value to be "4" (third weight value) and outputs it to the frequency distribution generation unit 432. When an event in which the absolute difference is equal to or less than the threshold has occurred consecutively three times, the weight determination unit 431 determines the weight value to be "8" and outputs it to the frequency distribution generation unit 432. A period T2 in FIG. 5 indicates an output period of a time count value corresponding to a case in which an event in which the absolute difference is equal to or less than the threshold has occurred consecutively two times. A period T3 in FIG. 5 indicates an output period of a time count value corresponding to a case in which an event in which the absolute difference is equal to or less than the threshold has occurred consecutively three times.

[0055] In the above example, the weight values ​​are values ​​that can be expressed as 2M (M is an integer), such as "1" (20), "2" (21), "4" (22), and "8" (23). By setting the weight values ​​to values ​​that are an integer power of 2 in this way, it is possible to perform calculation processing by bit shift calculation, and the calculation processing can be simplified. However, the weight values ​​are not limited to these settings, and may be values ​​such as "3" that cannot be expressed as 2M. In addition, the weight value may be set to a fraction such as "1 / 2" under some conditions, in which case the contribution of the time count value that satisfies the condition to the frequency distribution can be reduced. That is, the above-mentioned M may be a negative integer. In addition, the weight value may be set to "0" under some conditions, in which case the time count value that satisfies the condition is not reflected in the frequency distribution.

[0056] FIG. 7 is a graph showing weighting in the generation of the frequency distribution according to this embodiment. The horizontal axis of FIG. 7 is the time count value, and the vertical axis of FIG. 7 is the light-receiving count value. FIG. 7 shows the light-receiving count value corresponding to each time interval in the form of a bar graph. FIG. 7 also shows a schematic diagram of a frequency distribution update process performed when the weight determination unit 431 outputs the time count value TC(N) and the corresponding weight value to the frequency distribution generation unit 432. At this time, the frequency distribution generation unit 432 adds the light-receiving count value of the time count value TC(N) by the number of weight values. For example, when the weight value is "8", the frequency distribution generation unit 432 adds 8 to the light-receiving count value corresponding to the time count value TC(N) to update the frequency distribution. In FIG. 7, the white boxes indicate the light-receiving count values ​​that have already been added before the Nth measurement, and the boxes with diagonal hatching indicate the light-receiving count values ​​added in the Nth measurement.

[0057] As described above, the weight value determined by the weight determination unit 431 is set so as to increase the weight of a time count value when a series of time count values ​​close to each other are obtained. Time count values ​​caused by noise have a tendency not to have a series of close values. Therefore, by weighting with this weight value and generating a frequency distribution, it is possible to increase the ratio (S / N ratio) of the light reception count value caused by reflected light from the object X to the light reception count value caused by noise, and to reduce the influence of noise.

[0058] As described above, according to this embodiment, a time count value obtained at a certain measurement in one distance measurement period is compared with a time count value obtained earlier, and a weight value is determined based on the comparison result. By applying this weight value to the generation of the frequency distribution, the influence of the time count value caused by factors other than the reflected light from the object X is reduced. Therefore, according to this embodiment, a photoelectric conversion device capable of acquiring highly accurate distance information is provided. Furthermore, by performing weighted addition of the light reception count value in the frequency distribution using the method of this embodiment, distance measurement can be performed with high accuracy.

[0059] 6, weight values ​​are defined for the cases where the number of consecutive occurrences of an event in which the absolute difference is equal to or less than the threshold is two and three, but similar definitions may be used for the case where the number of consecutive occurrences is four or more. In that case, for example, if the number of consecutive occurrences is M, the weight value may be 2M.

[0060] In this embodiment, the comparison unit 413 compares the time count value TC(N) at the time of comparison with the time count value TC(N-1) immediately before the time of comparison, but is not limited to this. For example, the comparison unit 413 may be configured to compare the time count value TC(N) at the time of comparison with the time count value TC(N-2) two times before the time of comparison.

[0061] [Second embodiment] In this embodiment, a modification of the first embodiment in which a plurality of past time count values ​​can be stored in the distance measuring unit 41 will be described. In this embodiment, the description of elements common to the first embodiment may be omitted or simplified.

[0062] Fig. 8 is a block diagram showing the configuration of the distance measuring unit 41 according to this embodiment. As shown in Fig. 8, the column processing unit 410 has a holding unit 412a (first holding unit) and a holding unit 412b (second holding unit). That is, in this embodiment, the one holding unit 412 in Fig. 4 is replaced with two holding units 412a and 412b.

[0063] The holding unit 412a temporarily holds the time count value output from the time-to-digital conversion unit 411. The holding unit 412a also outputs the held time count value to the comparison unit 413 and the holding unit 412b. Therefore, the holding unit 412b has a function of holding and outputting the time count value output from the time-to-digital conversion unit 411 two cycles ago.

[0064] The holding unit 412b temporarily holds the time count value output from the holding unit 412a. The holding unit 412a can also output the held time count value to the comparing unit 413. Thus, the holding unit 412a has a function of holding and outputting the time count value output from the time-to-digital converting unit 411 one cycle before.

[0065] The comparison unit 413 compares the time count value input from the time-to-digital conversion unit 411 with the time count value input from the holding unit 412a. The comparison unit 413 further compares the time count value input from the time-to-digital conversion unit 411 with the time count value input from the holding unit 412b. Here, it is assumed that the comparison timing in the comparison unit 413 is after the Nth light emission in one distance measurement period. In this case, the time-to-digital conversion unit 411 outputs the Nth time count value TC(N), and the holding unit 412a outputs the (N-1)th time count value TC(N-1) which is one cycle before. The holding unit 412b outputs the (N-2)th time count value TC(N-2) which is one cycle before. That is, the comparison unit 413 compares the time count value TC(N) (first time count value) with the previous time count value TC(N-1) (second time count value) at the time of comparison. Furthermore, the comparison unit 413 compares the time count value TC(N) at the time of comparison with the time count value TC(N-2) before the time of comparison (third time count value). Then, the comparison unit 413 outputs the time count value TC(N) and the comparison result to the weight determination unit 431.

[0066] The time count values ​​in the holding units 412a and 412b are updated after the comparison in the comparing unit 413 is completed. That is, after the comparison based on the time count values ​​TC(N), TC(N-1), and TC(N-2) is completed as described above, the holding unit 412a erases the time count value TC(N-1) and holds the time count value TC(N). Also, the holding unit 412b erases the time count value TC(N-2) and holds the time count value TC(N-1).

[0067] FIG. 9 is a table showing an example of setting weight values ​​according to this embodiment. In the example of FIG. 9, the comparison unit 413 calculates a first absolute difference between the time count value TC(N) at the time of comparison and the previous time count value TC(N-1) at the time of comparison, and calculates a second absolute difference between the time count value TC(N) at the time of comparison and the time count value TC(N-2) before the previous time at the time of comparison. Then, the comparison unit 413 determines whether the calculated first absolute difference is equal to or smaller than a threshold value, and whether the calculated second absolute difference is equal to or smaller than a threshold value. Furthermore, the comparison unit 413 outputs these comparison results to the weight determination unit 431, and the weight determination unit 431 determines the weight value based on these comparison results. Note that the threshold value used to determine the first absolute difference and the threshold value used to determine the second absolute difference may be the same value or different values.

[0068] 9, when the first absolute difference is greater than the threshold and the second absolute difference is greater than the threshold, the weight determination unit 431 determines the weight value to be "1" (first weight value) and outputs it to the frequency distribution generation unit 432. When the first absolute difference is greater than the threshold and the second absolute difference is equal to or less than the threshold, the weight determination unit 431 determines the weight value to be "2" (second weight value) and outputs it to the frequency distribution generation unit 432. When the first absolute difference is equal to or less than the threshold and the second absolute difference is greater than the threshold, the weight determination unit 431 determines the weight value to be "4" (third weight value) and outputs it to the frequency distribution generation unit 432. When the first absolute difference is equal to or less than the threshold and the second absolute difference is equal to or less than the threshold, the weight determination unit 431 determines the weight value to be "8" (fourth weight value) and outputs it to the frequency distribution generation unit 432.

[0069] In this embodiment, the column processing unit 410 has two holding units 412a, 412b, so that the comparison unit 413 can compare the time count value obtained at a certain measurement within one distance measurement period with the time count value obtained two measurements ago. Therefore, the distance measuring device 1 of this embodiment can determine the weight value with higher accuracy by making a comparison taking into account the measurements up to two measurements ago even if the time count values ​​are not necessarily consecutive. Therefore, a photoelectric conversion device capable of acquiring distance information with high accuracy is provided.

[0070] In addition, compared to the configuration with one holding unit as in the first embodiment, the configuration of this embodiment has an increased number of holding units, and therefore the memory capacity is increased. Therefore, the configuration of the first embodiment can reduce the circuit scale compared to the configuration of this embodiment.

[0071] 9, the weight value "4" when the first absolute difference is equal to or smaller than the threshold value and the second absolute difference is greater than the threshold value is greater than the weight value "2" when the first absolute difference is greater than the threshold value and the second absolute difference is equal to or smaller than the threshold value. This enables weighting that gives priority to the previous time count value TC(N-1) over the time count value TC(N-2) before last.

[0072] In this embodiment, an example in which the number of holding units is two is shown, but the number of holding units may be three or more. In this case, the time count value obtained in a measurement older than two measurements ago can be held and used for comparison, so that the weight value can be determined with higher accuracy.

[0073] [Third embodiment] In this embodiment, a modified example will be described in which past time count values ​​can be stored in the distance measuring unit 41 and output as a signal for generating a frequency distribution. In this embodiment, the description of elements common to the first embodiment may be omitted or simplified.

[0074] 10 is a block diagram showing the configuration of the distance measurement unit 41 according to this embodiment. As shown in Fig. 10, the column processing unit 410 of this embodiment further includes a retention selection unit 414 in addition to the configuration of the column processing unit 410 shown in Fig. 4.

[0075] The hold selection unit 414 has a function of selecting whether to output the time count value output from the time-to-digital conversion unit 411 to the hold unit 412 for updating, or not to update. The hold selection unit 414 may be, for example, a switch that switches between connection and disconnection between the time-to-digital conversion unit 411 and the hold unit 412. The selection operation in the hold selection unit 414 is controlled based on the comparison result in the comparison unit 413. As a result, the hold unit 412 has a function of outputting the time count value TC(NK) output from the time-to-digital conversion unit 411 K periods ago (K is an integer equal to or greater than 1) to the comparison unit 413.

[0076] The comparator 413 compares the time count value TC(N) input from the time-to-digital converter 411 with the time count value TC(NK) input from the holder 412. Unlike the first embodiment, the comparator 413 of this embodiment has a function of selectively outputting either the time count value TC(N) or the time count value TC(NK) to the weight determiner 431 based on the comparison result.

[0077] Fig. 11 is a table showing an example of the operation of the comparison unit 413 and the retention selection unit 414 according to this embodiment. In the example of Fig. 11, the comparison unit 413 calculates the absolute difference between the time count value TC(N) at the time of comparison and the previous time count value TC(N-1) at the time of comparison, and judges whether the calculated absolute difference is equal to or smaller than a threshold value. The comparison unit 413 outputs the comparison result to the weight determination unit 431 and the retention selection unit 414. The weight determination unit 431 determines a weight value based on the comparison result. Note that the determination of the weight value performed by the weight determination unit 431 can be the same as that in the first embodiment, and therefore a description thereof will be omitted.

[0078] Based on the comparison result, the comparison unit 413 selects whether to output the time count value TC(N) or the time count value TC(NK) to the weight determination unit 431. As shown in Fig. 11, when the absolute difference is greater than the threshold, the comparison unit 413 outputs the time count value TC(N) at the time of comparison to the weight determination unit 431. When the absolute difference is equal to or less than the threshold, the comparison unit 413 outputs the time count value TC(NK) held in the holding unit 412 to the weight determination unit 431.

[0079] The hold selection unit 414 selects whether or not to update the time count value in the hold unit 412 based on the comparison result. When the absolute difference is greater than the threshold, the hold selection unit 414 operates to update the time count value TC(NK) held in the hold unit 412 to the time count value TC(N). When the absolute difference is equal to or less than the threshold, the comparison unit 413 operates to maintain the time count value TC(NK) held in the hold unit 412 as it is without updating it. When the time count value in the hold unit 412 is to be updated, the update operation is performed after the comparison in the comparison unit 413 is completed.

[0080] In this embodiment, the comparison unit 413 compares the time count value TC(N) with the time count value TC(NK) and selectively outputs either one to the weight determination unit 431 depending on the comparison result. In addition, when the time count value TC(NK) is output, the time count value is not updated. This allows the comparison unit 413 to operate in such a way that it repeatedly outputs the same time count value when time count values ​​close to each other are acquired multiple times in succession. When the same time count value is repeatedly input to the frequency distribution generation unit 432, the number of counts of the light reception count value at the same time interval is repeatedly added. This generates a frequency distribution in which the light reception count value caused by the reflected light from the object X is more emphasized, and the influence of noise is reduced. Therefore, a photoelectric conversion device capable of acquiring highly accurate distance information is provided.

[0081] In this embodiment, the determination of the weight value by the weight determination unit 431 and the weighting by the frequency distribution generation unit 432 are not essential. That is, the time count value output from the comparison unit 413 may be used for generating the frequency distribution as it is without weighting. Even in this case, the count numbers of the light reception count values ​​in the same time interval are repeatedly added, thereby reducing the influence of noise, and a photoelectric conversion device capable of acquiring a highly accurate signal is provided.

[0082] [Fourth embodiment] Fig. 12 is a block diagram of a light detection system according to this embodiment, more specifically, a block diagram of a range image sensor including the range finder 1 described in the above embodiment.

[0083] 12, the distance image sensor 501 includes an optical system 502, a photoelectric conversion device 503, an image processing circuit 504, a monitor 505, and a memory 506. The distance image sensor 501 receives light (modulated light, pulsed light) emitted from a light source device 511 toward a subject and reflected from the surface of the subject. The distance image sensor 501 can obtain a distance image according to the distance to the subject, based on the time from emission to reception of light. The light source device 511 corresponds to the light source device 3 in the above-described embodiment.

[0084] The optical system 502 includes one or more lenses, guides image light (incident light) from a subject to the photoelectric conversion device 503, and forms an image on the light receiving surface (sensor unit) of the photoelectric conversion device 503. The optical system 502 corresponds to the optical system 26 in the above-described embodiment.

[0085] The light receiving unit 20 and distance measuring unit 41 of the above-described embodiment can be applied as the photoelectric conversion device 503. The photoelectric conversion device 503 supplies an image processing circuit 504 with a distance signal indicating a distance determined from a light reception signal.

[0086] Image processing circuit 504 (signal processing unit) performs image processing to construct a distance image based on the distance signal supplied from photoelectric conversion device 503. The distance image (image data) obtained by the image processing can be displayed on monitor 505 and stored (recorded) in memory 506.

[0087] The range image sensor 501 configured in this manner can obtain an accurate range image by applying the configuration of the above-described embodiment.

[0088] [Fifth embodiment] FIG. 13(a) and FIG. 13(b) are block diagrams of devices related to the vehicle-mounted distance measuring device in this embodiment. The device 80 has a distance measuring unit 803, which is an example of the distance measuring device 1 in the above-mentioned embodiment, and a signal processing device (processing device) that processes a signal from the distance measuring unit 803. The device 80 has a distance measuring unit 803 that measures the distance to an object, and a collision determination unit 804 that determines whether or not there is a possibility of collision based on the measured distance. Here, the distance measuring unit 803 is an example of a distance information acquisition means that acquires distance information to the object. In other words, the distance information is information related to the distance to the object, etc. The collision determination unit 804 may use the distance information to determine the possibility of collision.

[0089] The device 80 is connected to a vehicle information acquisition device 810, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. In addition, the device 80 is connected to a control ECU 820, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 804. In addition, the device 80 is also connected to an alarm device 830 that issues an alarm to the driver based on the judgment result of the collision judgment unit 804. For example, when the judgment result of the collision judgment unit 804 indicates that there is a high possibility of a collision, the control ECU 820 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 830 warns the user by sounding an alarm such as a sound, displaying alarm information on the screen of a car navigation system, etc., and applying vibrations to a seat belt or steering wheel. These devices of the device 80 function as a mobile object control unit that controls the operation of controlling the vehicle as described above.

[0090] In this embodiment, the device 80 measures distances around the vehicle, for example, in front or behind. Fig. 13(b) shows the device when measuring distances in front of the vehicle (distance measurement range 850). A vehicle information acquisition device 810 as a distance measurement control means sends an instruction to the device 80 or distance measurement unit 803 to perform a distance measurement operation. With this configuration, the accuracy of distance measurement can be further improved.

[0091] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to prevent deviation from lanes, etc. Furthermore, the device is not limited to vehicles such as automobiles, but can be applied to moving bodies (moving devices) such as ships, aircraft, artificial satellites, industrial robots, and consumer robots. In addition, the present invention can be applied to devices that use object recognition or biometric recognition, such as intelligent transport systems (ITS) and surveillance systems, in addition to moving bodies.

[0092] [Modified embodiment] The present invention is not limited to the above-described embodiments and can be modified in various ways. For example, an example in which a part of the configuration of any of the embodiments is added to another embodiment, or an example in which a part of the configuration of any of the embodiments is replaced with a part of the configuration of another embodiment, is also an embodiment of the present invention.

[0093] The disclosure of this specification includes the complement of the concepts described in this specification. In other words, if the specification states, for example, that "A is B" (A=B), the specification is deemed to disclose or suggest that "A is not B" even if the statement that "A is not B" (A≠B) is omitted. This is because when it states that "A is B," it is assumed that the case that "A is not B" is taken into consideration.

[0094] The disclosure of this specification includes the following configurations. (Configuration 1) a light receiving unit that generates a light receiving signal according to incident light by photoelectric conversion; a time-to-digital conversion unit that periodically performs an operation of outputting a time count value indicating an elapsed time from light emission by a light source device to input of the light receiving signal every time a predetermined period elapses in one distance measurement period; a comparison unit that outputs a comparison result based on a first time count value that is a time count value obtained from the time-to-digital conversion unit during a first time period included in the one ranging period and a second time count value that is a time count value during a second time period included in the one ranging period; a weight determination unit that outputs a weight value based on the comparison result; a frequency distribution generating unit that generates a frequency distribution of the time count values ​​in the one distance measuring period by using the weight value for frequency addition; A photoelectric conversion device comprising: (Configuration 2) The weight determination unit outputs the weight value based on an absolute difference between the first time count value and the second time count value. 2. The photoelectric conversion device according to configuration 1. (Configuration 3) The weight determination unit outputs a first weight value when the absolute difference is greater than a threshold, and outputs a second weight value greater than the first weight value when the absolute difference is equal to or less than the threshold. 3. The photoelectric conversion device according to configuration 2. (Configuration 4) The weight determination unit stores past comparison results and outputs the weight value further based on the past comparison results. 4. The photoelectric conversion device according to any one of configurations 1 to 3. (Configuration 5) The weight determination unit outputs a first weight value when an absolute difference between the first time count value and the second time count value is greater than a threshold value, outputs a second weight value greater than the first weight value when the absolute difference is equal to or less than the threshold value, and outputs a third weight value greater than the second weight value when a comparison result in which the absolute difference is equal to or less than the threshold value is repeated a plurality of times. 5. The photoelectric conversion device according to configuration 4. (Configuration 6) A first holding unit that holds the time count value output from the time-to-digital conversion unit, The comparison unit acquires the time count value held in the first holding unit as the second time count value. 6. The photoelectric conversion device according to any one of configurations 1 to 5. (Configuration 7) The first holding unit updates the held time count value every time the time count value is output from the time-to-digital conversion unit. 7. The photoelectric conversion device according to configuration 6. (Configuration 8) The second time period is a period immediately preceding the first time period. 8. The photoelectric conversion device according to any one of configurations 1 to 7. (Configuration 9) The comparison unit outputs the comparison result further based on a third time count value output from the time-to-digital conversion unit at a third time that is included in the same distance measurement period as the first time and that is prior to the second time. 2. The photoelectric conversion device according to configuration 1. (Configuration 10) The weight determination unit outputs the weight value based on a first absolute difference between the first time count value and the second time count value and a second absolute difference between the first time count value and the third time count value. 10. The photoelectric conversion device according to configuration 9. (Configuration 11) The weight determination unit outputs a first weight value when the first absolute difference and the second absolute difference are greater than a threshold, and outputs a second weight value greater than the first weight value when the first absolute difference is greater than the threshold and the second absolute difference is equal to or less than the threshold. 11. The photoelectric conversion device according to configuration 10. (Configuration 12) the weight determination unit outputs a third weight value that is greater than the second weight value when the first absolute difference is equal to or less than the threshold value and the second absolute difference is greater than the threshold value. 12. The photoelectric conversion device according to claim 11, (Configuration 13) The weight determination unit outputs a fourth weight value that is greater than the third weight value when the first absolute difference and the second absolute difference are equal to or less than the threshold value. 13. The photoelectric conversion device according to configuration 12. (Configuration 14) a first holding unit that holds the time count value output from the time-to-digital conversion unit; a second holding unit that holds the time count value output from the first holding unit; 14. The photoelectric conversion device according to any one of configurations 9 to 13, further comprising: (Configuration 15) Each time the time count value is input from the time-to-digital conversion unit, the first holding unit updates the held time count value to the time count value input from the time-to-digital conversion unit, and the second holding unit updates the held time count value to the time count value input from the first holding unit. 15. The photoelectric conversion device according to configuration 14. (Configuration 16) the second time period is a period immediately preceding the first time period; The third time period is the period immediately preceding the second time period. 16. The photoelectric conversion device according to any one of configurations 9 to 15. (Configuration 17) A first holding unit that holds the time count value output from the time-to-digital conversion unit, The comparison unit acquires the time count value held in the first holding unit as the second time count value, The comparison unit outputs either the first time count value or the second time count value as a signal for generating the frequency distribution based on a result of the comparison. 6. The photoelectric conversion device according to any one of configurations 1 to 5. (Configuration 18) The method further includes the steps of: selecting whether or not to update the time count value in the first holding unit based on the comparison result; 18. The photoelectric conversion device according to claim 17, (Configuration 19) the comparison unit outputs either the first time count value or the second time count value as a signal for generating the frequency distribution based on an absolute difference between the first time count value and the second time count value; The selection unit controls whether or not to update the time count value in the first holding unit based on the absolute difference. 19. The photoelectric conversion device according to configuration 18. (Configuration 20) the comparison unit outputs the first time count value as a signal for generating the frequency distribution when the absolute difference is greater than a threshold value, and outputs the second time count value as a signal for generating the frequency distribution when the absolute difference is equal to or less than the threshold value; The selection unit controls the first holding unit so that the time count value in the first holding unit is updated when the absolute difference is greater than the threshold value, and controls the first holding unit so that the time count value in the first holding unit is not updated when the absolute difference is equal to or less than the threshold value. 20. The photoelectric conversion device according to claim 19, (Configuration 21) a light receiving unit that generates a light receiving signal according to incident light by photoelectric conversion; a time-to-digital conversion unit that periodically performs an operation of outputting a time count value indicating an elapsed time from light emission by a light source device to input of the light receiving signal every time a predetermined period elapses in one distance measurement period; a comparison unit that performs a comparison based on a first time count value output from the time-to-digital conversion unit during a first time included in the one ranging period and a second time count value output from the time-to-digital conversion unit during a second time included in the one ranging period and prior to the first time; having The comparison unit outputs either the first time count value or the second time count value as a time count value used to generate a frequency distribution in which a plurality of time intervals are associated with light receiving count values ​​based on the number of times the time count value corresponding to the corresponding time interval is output, based on a result of the comparison. A photoelectric conversion device comprising: (Configuration 22) The photoelectric conversion device according to any one of configurations 1 to 21, a signal processing unit that processes a signal output from the photoelectric conversion device; 1. An optical detection system comprising: (Configuration 23) A mobile object, The photoelectric conversion device according to any one of configurations 1 to 21, a moving object control unit that controls the moving object based on distance information acquired by the photoelectric conversion device; A moving object comprising:

[0095] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for implementing one or more of the functions.

[0096] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0097] 1 Ranging device 20 Light receiving section 411 Time Digital Converter 412, 412a, 412b holding part 413 Comparison Section 431 Weight Determination Unit

Claims

1. a light receiving unit that generates a light receiving signal according to incident light by photoelectric conversion; a time-to-digital conversion unit that periodically performs an operation of outputting a time count value indicating an elapsed time from light emission by a light source device to input of the light receiving signal every time a predetermined period elapses in one distance measurement period; a comparison unit that outputs a comparison result based on a first time count value obtained from the time-to-digital conversion unit during a first time period included in the one ranging period and a second time count value obtained during a second time period included in the one ranging period; a weight determination unit that outputs a weight value based on the comparison result; a frequency distribution generating unit that generates a frequency distribution of the time count value in the one distance measuring period by using the weight value for frequency addition; A photoelectric conversion device comprising:

2. The weight determining unit outputs the weight value based on an absolute difference between the first time count value and the second time count value.

2. The photoelectric conversion device according to claim 1.

3. The weight determination unit outputs a first weight value when the absolute difference is greater than a threshold, and outputs a second weight value greater than the first weight value when the absolute difference is equal to or less than the threshold.

3. The photoelectric conversion device according to claim 2.

4. The weight determination unit stores past comparison results and outputs the weight value further based on the past comparison results.

2. The photoelectric conversion device according to claim 1.

5. The weight determination unit outputs a first weight value when an absolute difference between the first time count value and the second time count value is greater than a threshold value, outputs a second weight value greater than the first weight value when the absolute difference is equal to or less than the threshold value, and outputs a third weight value greater than the second weight value when a comparison result in which the absolute difference is equal to or less than the threshold value is repeated a plurality of times.

5. The photoelectric conversion device according to claim 4.

6. a first holding unit that holds the time count value output from the time-to-digital conversion unit; The comparison unit acquires the time count value held in the first holding unit as the second time count value.

2. The photoelectric conversion device according to claim 1.

7. The first holding unit updates the held time count value every time the time digital conversion unit outputs the time count value.

7. The photoelectric conversion device according to claim 6.

8. The second time period is a period immediately preceding the first time period.

2. The photoelectric conversion device according to claim 1.

9. The comparison unit outputs the comparison result further based on a third time count value output from the time-to-digital conversion unit at a third time that is included in the same distance measurement period as the first time and that is prior to the second time.

2. The photoelectric conversion device according to claim 1.

10. The weight determination unit outputs the weight value based on a first absolute difference between the first time count value and the second time count value and a second absolute difference between the first time count value and the third time count value.

10. The photoelectric conversion device according to claim 9.

11. The weight determination unit outputs a first weight value when the first absolute difference and the second absolute difference are greater than a threshold, and outputs a second weight value greater than the first weight value when the first absolute difference is greater than the threshold and the second absolute difference is equal to or less than the threshold. The photoelectric conversion device according to claim 10 .

12. The weight determination unit outputs a third weight value that is greater than the second weight value when the first absolute difference is equal to or less than the threshold value and the second absolute difference is greater than the threshold value. The photoelectric conversion device according to claim 11 .

13. The weight determination unit outputs a fourth weight value that is greater than the third weight value when the first absolute difference and the second absolute difference are equal to or less than the threshold value.

13. The photoelectric conversion device according to claim 12.

14. a first holding unit that holds the time count value output from the time-to-digital conversion unit; a second holding unit that holds the time count value output from the first holding unit; The photoelectric conversion device according to claim 9 , further comprising:

15. Each time the time count value is input from the time-to-digital conversion unit, the first holding unit updates the held time count value to the time count value input from the time-to-digital conversion unit, and the second holding unit updates the held time count value to the time count value input from the first holding unit.

15. The photoelectric conversion device according to claim 14.

16. the second time period is a period immediately preceding the first time period, The third time period is a period immediately preceding the second time period.

10. The photoelectric conversion device according to claim 9.

17. a first holding unit that holds the time count value output from the time-to-digital conversion unit; The comparison unit acquires the time count value held in the first holding unit as the second time count value, The comparison unit outputs either the first time count value or the second time count value as a signal for generating the frequency distribution based on a result of the comparison.

2. The photoelectric conversion device according to claim 1.

18. The time count value in the first holding unit is updated based on the comparison result.

18. The photoelectric conversion device according to claim 17.

19. the comparison unit outputs either the first time count value or the second time count value as a signal for generating the frequency distribution based on an absolute difference between the first time count value and the second time count value; The selection unit controls whether or not to update the time count value in the first holding unit based on the absolute difference.

20. The photoelectric conversion device according to claim 18,

20. the comparison unit outputs the first time count value as a signal for generating the frequency distribution when the absolute difference is greater than a threshold value, and outputs the second time count value as a signal for generating the frequency distribution when the absolute difference is equal to or less than the threshold value; The selection unit controls the first holding unit so that the time count value in the first holding unit is updated when the absolute difference is greater than the threshold value, and controls the first holding unit so that the time count value in the first holding unit is not updated when the absolute difference is equal to or less than the threshold value.

20. The photoelectric conversion device according to claim 19.

21. a light receiving unit that generates a light receiving signal according to incident light by photoelectric conversion; a time-to-digital conversion unit that periodically performs an operation of outputting a time count value indicating an elapsed time from light emission by a light source device to input of the light receiving signal every time a predetermined period elapses in one distance measurement period; a comparison unit that performs a comparison based on a first time count value output from the time-to-digital conversion unit at a first time included in the one ranging period and a second time count value output from the time-to-digital conversion unit at a second time included in the one ranging period and prior to the first time; having The comparison unit outputs either the first time count value or the second time count value as a time count value used to generate a frequency distribution in which a plurality of time intervals are associated with light receiving count values ​​based on the number of times the time count value corresponding to the corresponding time interval is output, based on a result of the comparison. A photoelectric conversion device comprising:

22. The photoelectric conversion device according to any one of claims 1 to 21, a signal processing unit that processes a signal output from the photoelectric conversion device; 1. An optical detection system comprising:

23. A mobile object, The photoelectric conversion device according to any one of claims 1 to 21, a moving object control unit that controls the moving object based on distance information acquired by the photoelectric conversion device; A moving object comprising:

Images