Distance image capturing device, and distance image capturing method

Abstract

This distance image capturing device comprises a light source unit, a light receiving unit that includes a pixel drive circuit and a pixel equipped with a plurality of charge accumulating units, and a distance image processing unit that controls the pixel drive circuit to accumulate charges in each of the charge accumulating units, and calculates the distance to a subject on the basis of the amount of charge accumulated in each of the charge accumulating units, wherein the distance image processing unit causes each of the charge accumulating units to accumulate charges using a plurality of drive patterns, and as a result of accumulating charges in the charge accumulating units in each of the plurality of drive patterns, makes the number of times light is received smaller for the charge accumulating units having a shorter accumulation delay time than for the charge accumulating units having a longer accumulation delay time, where the number of times light is received is the number of times charges are allowed to accumulate in the charge accumulating unit in a reflected light reception interval, which is an interval from a light emission timing until a reflected light reception time has elapsed.

Description

Range image capturing device and range image capturing method

[0001] This application claims priority to Japanese Patent Application No. 2023-129765, filed on August 9, 2023, the contents of which are incorporated herein by reference.

[0002] Taking advantage of the fact that the speed of light is known, a time-of-flight (hereinafter referred to as "TOF") distance imaging device has been realized, which measures the distance between a measuring device and an object based on the flight time of light in space (measurement space) (see, for example, Patent Document 1).

[0003] Japanese Patent No. 4235729

[0004] When such a distance imaging device simultaneously measures a close object (near-distance object) and a far-distance object (far-distance object), the reflected light from the close object is received with a higher intensity than the reflected light from the far-distance object. In this case, multiple reflections, known as flare, may occur in optical systems such as lenses. When flare occurs, the reflected light from the close object is superimposed on the pixel receiving the reflected light from the far-distance object, making it difficult to accurately measure the distance to the far-distance object. One possible way to suppress this flare is to apply special processing to the lens to make it less likely to produce flare, but this may increase manufacturing costs.

[0005] The present invention has been made in light of the above-mentioned problems, and aims to provide a distance image capturing device and a distance image capturing method that can suppress the flare phenomenon without increasing manufacturing costs.

[0006] The distance image pickup device of the present invention comprises a light source unit that irradiates a subject with a light pulse, a light receiving unit having pixels each including a photoelectric conversion element that generates a charge in response to the incident light and a plurality of charge accumulation units that accumulate the charge, and a pixel drive circuit that distributes and accumulates charge in each of the charge accumulation units at an accumulation timing synchronized with the irradiation timing of the light pulse, and a distance image processing unit that controls the pixel drive circuit to accumulate charge in each of the charge accumulation units and calculates the distance to the subject based on the amount of charge accumulated in each of the charge accumulation units, and the distance image processing unit controls the pixel drive circuit to accumulate charge in each of the charge accumulation units. Charge is accumulated in each of the charge accumulation units using a plurality of drive patterns each having a different number of charge accumulation units, and as a result of accumulating charge in the charge accumulation units in each of the plurality of drive patterns, the charge accumulation units having a smaller accumulation delay time, which is the difference between the irradiation timing and the accumulation timing, receive light fewer times than the charge accumulation units having a larger accumulation delay time, and the number of light receptions is the number of times charge is accumulated in the charge accumulation unit during the reflected light reception interval, which is the period from the irradiation timing to the elapse of the reflected light reception time, which is the time corresponding to the measurable distance.

[0007] The distance image capturing method of the present invention is a distance image capturing method performed by a distance image capturing device including: a light source unit that irradiates a subject with a light pulse; a light receiving unit having pixels each including a photoelectric conversion element that generates charge in response to the incident light and a plurality of charge accumulation units that accumulate the charge; a pixel drive circuit that distributes and accumulates charge in each of the charge accumulation units at an accumulation timing synchronized with the irradiation timing of the light pulse; and a distance image processing unit that controls the pixel drive circuit to accumulate charge in each of the charge accumulation units and calculates the distance to the subject based on the amount of charge accumulated in each of the charge accumulation units, wherein the distance image processing unit Charge is accumulated in each of the charge accumulation units using a plurality of drive patterns each having a different number of charge accumulation units that accumulate charge, and as a result of accumulating charge in the charge accumulation units in each of the plurality of drive patterns, the charge accumulation units having a smaller accumulation delay time, which is the difference between the irradiation timing and the accumulation timing, receive light fewer times than the charge accumulation units having a larger accumulation delay time, and the number of light receptions is the number of times charge is accumulated in the charge accumulation units during the reflected light reception interval, which is the period from the irradiation timing to the elapse of the reflected light reception time, which is the time corresponding to the measurable distance.

[0008] According to the present invention, the flare phenomenon can be suppressed without increasing the manufacturing cost.

[0009] FIG. 1 is a block diagram showing a schematic configuration of a distance image pickup device 1 of an embodiment. FIG. 2 is a block diagram showing a schematic configuration of a distance image sensor 32 of an embodiment. FIG. 3 is a circuit diagram showing an example of the configuration of a pixel 321 of an embodiment. FIG. 4 is a diagram explaining a frame period of an embodiment. FIG. 5 is a diagram explaining a frame period of an embodiment. FIG. 6 is a diagram explaining a frame period of an embodiment. FIG. 7 is a diagram explaining a frame period of an embodiment. FIG. 8 is a diagram explaining a frame period of an embodiment. FIG. 9 is a flowchart showing the flow of processing performed by the distance image pickup device 1 of an embodiment.

[0010] Hereinafter, a distance image capturing device according to an embodiment will be described with reference to the drawings.

[0011] Fig. 1 is a block diagram showing the schematic configuration of a distance imaging device according to an embodiment. The distance imaging device 1 includes, for example, a light source unit 2, a light receiving unit 3, and a distance image processing unit 4. Fig. 1 also shows a subject OB, which is an object to which the distance is to be measured by the distance imaging device 1.

[0012] The light source unit 2 irradiates a measurement target space containing the object OB with a light pulse PO under control of the distance image processor 4. The light source unit 2 is, for example, a surface-emitting semiconductor laser module such as a vertical cavity surface-emitting laser (VCSEL). The light source unit 2 includes a light source device 21 and a diffuser plate 22.

[0013] The light source device 21 is a light source that emits laser light in a near-infrared wavelength band (for example, a wavelength band of 850 nm to 940 nm) that becomes the light pulse PO that is irradiated onto the subject OB. The light source device 21 is, for example, a semiconductor laser light-emitting element. The light source device 21 emits pulsed laser light in response to control from the timing control unit 41.

[0014] The diffuser plate 22 is an optical component that diffuses the laser light in the near-infrared wavelength band emitted by the light source device 21 to the extent of the surface that is irradiated onto the subject OB. The pulsed laser light diffused by the diffuser plate 22 is emitted as a light pulse PO and irradiated onto the subject OB.

[0015] The light receiving unit 3 receives reflected light RL of the light pulse PO reflected by the object OB, the distance of which is to be measured in the range image pickup device 1, and outputs a pixel signal corresponding to the received reflected light RL. The light receiving unit 3 includes a lens 31 and a range image sensor 32.

[0016] The lens 31 is an optical lens that guides the incident reflected light RL to the range image sensor 32. The lens 31 emits the incident reflected light RL toward the range image sensor 32, causing the light to be received (incident) by pixels provided in the light receiving region of the range image sensor 32.

[0017] The range image sensor 32 is an imaging element used in the range image capturing device 1. The range image sensor 32 has a plurality of pixels arranged in a two-dimensional matrix. Each pixel of the range image sensor 32 has one photoelectric conversion element, a plurality of charge accumulation units corresponding to this one photoelectric conversion element, and a component that distributes charge to each of the charge accumulation units. In other words, the pixel is an imaging element with a distribution configuration in which charge is distributed and stored in a plurality of charge accumulation units.

[0018] The distance image sensor 32 distributes the charges generated by the photoelectric conversion elements to each charge accumulation unit in accordance with control from the timing control unit 41. The distance image sensor 32 also outputs pixel signals corresponding to the amount of charge distributed to the charge accumulation units. The distance image sensor 32 has a plurality of pixels arranged in a two-dimensional matrix, and outputs pixel signals for one frame corresponding to each pixel.

[0019] The distance image processing unit 4 controls the distance image capturing device 1 and calculates the distance to the subject OB. The distance image processing unit 4 includes a timing control unit 41, a distance calculation unit 42, and a measurement control unit 43.

[0020] The timing control unit 41 controls the timing of outputting various control signals required for measurement in accordance with the control of the measurement control unit 43. The various control signals here include, for example, a signal for controlling the irradiation of the light pulse PO, a signal for allocating and accumulating the reflected light RL in multiple charge accumulation units, a signal for controlling the number of accumulations per frame, etc. The number of accumulations is the number of times the process of allocating and accumulating electric charges in the charge accumulation units is repeated in a processing unit (for example, one frame or subframe).

[0021] The distance calculation unit 42 calculates the distance to the object OB based on the pixel signal output from the distance image sensor 32, and outputs the calculated distance. The distance calculation unit 42 calculates the delay time from when the light pulse PO is emitted until when the reflected light RL is received based on the amount of charge accumulated in the multiple charge accumulation units, and calculates the distance to the object OB according to the calculated delay time.

[0022] The measurement control unit 43 controls the timing control unit 41. For example, the measurement control unit 43 sets the number of integration times for one frame, and controls the timing control unit 41 so that imaging is performed according to the set contents.

[0023] With this configuration, in the distance image capturing device 1, the light source unit 2 irradiates a light pulse PO in the near-infrared wavelength band onto the subject OB, and the light receiving unit 3 receives the reflected light RL reflected by the subject OB, and the distance image processing unit 4 outputs distance information measuring the distance to the subject OB.

[0024] Note that while Figure 1 shows a distance image capturing device 1 configured such that the distance image processing unit 4 is provided inside the distance image capturing device 1, the distance image processing unit 4 may also be a component provided outside the distance image capturing device 1.

[0025] The configuration of the distance image sensor 32 will now be described with reference to Fig. 2. Fig. 2 is a block diagram showing a schematic configuration of the imaging element (distance image sensor 32) used in the distance image capturing device 1 of the embodiment.

[0026] As shown in FIG. 2, the distance image sensor 32 includes, for example, a light receiving area 320 in which a plurality of pixels 321 are arranged, a control circuit 322, a vertical scanning circuit 323 having a distribution operation, a horizontal scanning circuit 324, and a pixel signal processing circuit 325.

[0027] The light receiving area 320 is an area in which a plurality of pixels 321 are arranged, and FIG. 2 shows an example in which the pixels are arranged in a two-dimensional matrix of 8 rows and 8 columns. The pixels 321 accumulate electric charges corresponding to the amount of light received. The control circuit 322 comprehensively controls the range image sensor 32. The control circuit 322 controls the operation of the components of the range image sensor 32 in accordance with instructions from, for example, the timing control unit 41 of the range image processing unit 4. Note that the components of the range image sensor 32 may be directly controlled by the timing control unit 41, in which case the control circuit 322 may be omitted.

[0028] The vertical scanning circuit 323 is a circuit that controls the pixels 321 arranged in the light receiving region 320 row by row in accordance with control from the control circuit 322. The vertical scanning circuit 323 outputs a voltage signal corresponding to the amount of charge accumulated in each charge accumulation unit CS of the pixels 321 to the pixel signal processing circuit 325. For example, the vertical scanning circuit 323 distributes and accumulates the charge converted by the photoelectric conversion elements in each charge accumulation unit of the pixels 321 at an accumulation timing synchronized with the irradiation of the light pulse PO. Furthermore, the vertical scanning circuit 323 discharges the charge converted by the photoelectric conversion elements from a charge discharge unit (a drain gate transistor GD described later) at a timing different from the accumulation timing. In this case, the vertical scanning circuit 323 is an example of a "pixel driving circuit."

[0029] The pixel signal processing circuit 325 is a circuit that performs predetermined signal processing (e.g., noise suppression processing, A / D conversion processing, etc.) on the voltage signals output from the pixels 321 in each column to the corresponding vertical signal lines in accordance with control from the control circuit 322.

[0030] Horizontal scanning circuit 324 is a circuit that sequentially outputs signals output from pixel signal processing circuit 325 to horizontal signal lines in accordance with control from control circuit 322. As a result, pixel signals corresponding to the amount of charge accumulated for one frame are sequentially output to distance image processing unit 4 via the horizontal signal lines.

[0031] In the following description, it is assumed that the pixel signal processing circuit 325 performs A / D conversion processing and the pixel signals are digital signals.

[0032] The configuration of the pixel 321 will now be described with reference to Fig. 3. Fig. 3 is a circuit diagram showing an example of the configuration of the pixel 321 arranged in the light receiving region 320 of the range image sensor 32 of the embodiment. Fig. 3 shows an example of the configuration of one pixel 321 out of the multiple pixels 321 arranged in the light receiving region 320. The pixel 321 is an example of a configuration including four pixel signal readout units.

[0033] The pixel 321 includes one photoelectric conversion element PD, a drain gate transistor GD, and four pixel signal readout units RU that output voltage signals from corresponding output terminals O. Each pixel signal readout unit RU includes a readout gate transistor G, a floating diffusion FD, a charge storage capacitance C, a reset gate transistor RT, a source follower gate transistor SF, and a select gate transistor SL. In each pixel signal readout unit RU, the floating diffusion FD and the charge storage capacitance C form a charge storage unit CS.

[0034] 3, the four pixel signal readout units RU are distinguished from one another by adding a number from 1 to 4 after the reference symbol "RU" for each unit. Similarly, the components of the four pixel signal readout units RU are distinguished from one another by adding a number representing the corresponding pixel signal readout unit RU after the reference symbol.

[0035] 3, the pixel signal readout unit RU1, which outputs a voltage signal from the output terminal O1, includes a readout gate transistor G1, a floating diffusion FD1, a charge storage capacitance C1, a reset gate transistor RT1, a source follower gate transistor SF1, and a select gate transistor SL1. In the pixel signal readout unit RU1, the floating diffusion FD1 and the charge storage capacitance C1 form a charge storage unit CS1. The pixel signal readout units RU2 to RU4 have a similar configuration.

[0036] The photoelectric conversion element PD is a buried photodiode that photoelectrically converts incident light to generate electric charges and accumulates the generated electric charges. The photoelectric conversion element PD may have any structure. For example, the photoelectric conversion element PD may be a PN photodiode having a structure in which a P-type semiconductor and an N-type semiconductor are joined together, or a PIN photodiode having a structure in which an I-type semiconductor is sandwiched between a P-type semiconductor and an N-type semiconductor. Furthermore, the photoelectric conversion element PD is not limited to a photodiode, and may be, for example, a photogate-type photoelectric conversion element.

[0037] In pixel 321, the photoelectric conversion element PD photoelectrically converts the incident light to generate electric charges, which are then distributed to each of the four charge storage sections CS, and voltage signals corresponding to the amount of electric charge distributed are output to the pixel signal processing circuit 325.

[0038] The configuration of the pixels arranged in the range image sensor 32 is not limited to the configuration including four pixel signal readout units RU as shown in Fig. 3, but may be any pixel configured to include a plurality of pixel signal readout units RU. In other words, the number of pixel signal readout units RU (charge accumulation units CS) included in the pixels arranged in the range image sensor 32 may be two, three, five or more.

[0039] 3 shows an example in which the charge storage unit CS is configured by a floating diffusion FD and a charge storage capacitance C. However, the charge storage unit CS only needs to be configured by at least a floating diffusion FD, and the pixel 321 may not have a charge storage capacitance C.

[0040] 3 shows an example of a configuration including the drain gate transistor GD, but if there is no need to discard the charge accumulated (remaining) in the photoelectric conversion element PD, the pixel 321 may be configured without the drain gate transistor GD. The drain gate transistor GD is an example of a "charge discharge unit."

[0041] Here, if a flare phenomenon occurs when the distance image capturing device 1 simultaneously measures an object at a close distance (near-distance object) and an object at a long distance (long-distance object), the reflected light RL coming from the near-distance object will be superimposed on the pixel 321 that receives the reflected light RL coming from the long-distance object, making it difficult to accurately measure the distance to the long-distance object.

[0042] To address this issue, in this embodiment, a plurality of drive patterns are provided, and as a result of driving the plurality of drive patterns, the time (exposure time) for receiving reflected light RL from a close-distance object is made shorter than the time for receiving reflected light RL from a long-distance object. In other words, as a result of accumulating charges in the charge accumulation units CS in each of the plurality of drive patterns, the charge accumulation units CS with a short accumulation delay time receive light less frequently than the charge accumulation units CS with a long accumulation delay time.

[0043] The accumulation delay time is the difference between the irradiation timing and the accumulation timing. The irradiation timing is the timing when irradiation of the light pulse PO starts. The accumulation timing is the timing when the operation of accumulating charge in the charge accumulation unit CS starts (when the readout gate transistor G is turned on). A charge accumulation unit CS with a short accumulation delay time accumulates charge corresponding to reflected light RL arriving from a close-distance object. A charge accumulation unit CS with a long accumulation delay time accumulates charge corresponding to reflected light RL arriving from a long-distance object.

[0044] The number of light receptions is the number of times that reflected light RL can be received. The number of light receptions is the number of times that charge is accumulated in the charge accumulation unit CS from the irradiation timing until the reflected light reception time Tth (see FIG. 6A, etc.) has elapsed. The period from the irradiation timing until the reflected light reception time Tth has elapsed is also referred to as the reflected light reception interval. The reflected light reception time Tth is the time during which the reflected light RL is expected to be received after the light pulse PO has been irradiated. The reflected light reception time Tth is determined arbitrarily depending on the distance that the distance image capturing device 1 can measure. If charge is accumulated in the charge accumulation unit CS after the reflected light reception time Tth has elapsed from the irradiation timing, no charge corresponding to the reflected light RL will be accumulated in the charge accumulation unit CS, and only charge corresponding to external light will be accumulated.

[0045] In this manner, in this embodiment, the pixels 321 are driven so as to reduce the time (exposure time) for receiving reflected light RL from a close-distance object. This reduces the number of times that the pixels 321, which receive reflected light RL from a long-distance object, receive reflected light RL from a close-distance object. This makes it possible to accurately measure the distance to a long-distance object.

[0046] In the following description, a case where a plurality of drive patterns (first drive pattern to fourth drive pattern) are driven in one frame will be described as an example. However, this is not limited to this. A plurality of frames may be used, and a plurality of drive patterns may be driven in each frame. A plurality of drive patterns may be driven by providing a plurality of sub-frames in one frame.

[0047] An example of a frame period according to the embodiment will now be described with reference to Fig. 4. Fig. 4 is a diagram illustrating a frame period according to the embodiment.

[0048] This diagram shows a timing chart of elements corresponding to each of the items "LI," "G1" to "G4," and "GD." "LI" indicates the irradiation timing of the light pulse PO; when it is in the ON state, light is irradiated, and when it is in the OFF state, light is not irradiated. "G1" to "G4" indicate the accumulation timing of the read gate transistors G1 to G4; when it is in the ON state, charge is accumulated, and when it is in the OFF state, charge is not accumulated. "GD" indicates the drive timing of the drain gate transistor GD; when it is in the ON state, charge is discharged, and when it is in the OFF state, charge is not discharged.

[0049] 4, the frame period includes, for example, an accumulation period and a readout period. During the accumulation period, the cycle period is repeatedly executed a predetermined number of times N. During the cycle period, drive patterns corresponding to the first to fourth drive patterns are executed.

[0050] 4 is a reference drive pattern that sequentially accumulates charges in all four charge accumulation units CS at accumulation timings synchronized with the irradiation timing. In the first drive pattern, the drain gate transistor GD is turned off and the readout gate transistors G1 to G4 are sequentially turned on at the same timing as the irradiation timing of the light pulse PO.

[0051] Specifically, in the first drive pattern, the timing control unit 41 turns the drain gate transistor GD off and the read gate transistor G1 on at the irradiation timing via the control circuit 322. After a specific accumulation time To (e.g., the same time as the irradiation time for irradiating the light pulse PO) has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off. At the timing when the read gate transistor G1 is turned off, the read gate transistor G2 is turned on. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G3 is turned on. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G4 is turned on. After the storage time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on.

[0052] As a result, while each of the readout gate transistors G1 to G4 is controlled to be in the on state, the charge photoelectrically converted by the photoelectric conversion element PD is accumulated in the charge accumulation units CS1 to CS4. Then, at the timing when the readout gate transistor G4 is turned off, the drain gate transistor GD is turned on to discharge the charge. As a result, the charge photoelectrically converted by the photoelectric conversion element PD is discarded via the drain gate transistor GD. In the first drive pattern, this driving, in which charge is accumulated in the charge accumulation units CS1 to CS4 in order, is repeated a predetermined number of times N.

[0053] 4 is a drive pattern in which the accumulation timing of each of the readout gate transistors G1 to G4 relative to the irradiation timing is the same as that of the first drive pattern, and the readout gate transistor G1 is not turned on. In other words, the second drive pattern is a drive pattern in which, compared to the first drive pattern, charge is not accumulated in the charge accumulation unit CS1 corresponding to the readout gate transistor G1. In the second drive pattern, such driving in which charge is accumulated in the charge accumulation units CS2 to CS4 in order is repeated a predetermined number of times N.

[0054] Specifically, in the second driving pattern, the timing control unit 41, via the control circuit 322, turns the drain gate transistor GD off and turns the read gate transistor G2 on after the accumulation time To has elapsed since the irradiation timing. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G3 is turned on. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G4 is turned on. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on.

[0055] 4 is a drive pattern in which the accumulation timing of each of the readout gate transistors G1 to G4 relative to the irradiation timing is the same as that of the first drive pattern, and the readout gate transistors G1 and G2 are not turned on. That is, the third drive pattern is a drive pattern in which, compared to the first drive pattern, charge is not accumulated in the charge accumulation units CS1 and CS2 corresponding to the readout gate transistors G1 and G2. In the third drive pattern, such driving in which charge is accumulated in the charge accumulation units CS3 to CS4 in sequence is defined as a third accumulation period, and the driving corresponding to the third accumulation period is repeatedly executed a predetermined number of times N.

[0056] Specifically, in the third driving pattern, the timing control unit 41 turns the drain gate transistor GD off and turns the read gate transistor G3 on via the control circuit 322 after the accumulation time To×2 has elapsed since the irradiation timing. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G4 is turned on. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on.

[0057] 4 is a drive pattern in which the accumulation timing of each of the readout gate transistors G1 to G4 relative to the irradiation timing is the same as that of the first drive pattern, and the readout gate transistors G1 to G3 are not turned on. In other words, the fourth drive pattern is a drive pattern in which, unlike the first drive pattern, charge is not accumulated in the charge accumulation units CS1 to CS3 corresponding to the readout gate transistors G1 to G3. In the fourth drive pattern, such driving in which charge is accumulated only in the charge accumulation unit CS4 is repeatedly executed a predetermined number of times N.

[0058] Specifically, in the fourth driving pattern, the timing control unit 41 turns off the drain gate transistor GD and turns on the read gate transistor G4 after the accumulation time To×3 has elapsed from the irradiation timing via the control circuit 322. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the timing control unit 41 turns off the read gate transistor G4 and turns on the drain gate transistor GD.

[0059] The readout period is a period during which storage signals corresponding to the amount of charge stored in each charge storage unit CS are read out and output in each drive pattern. For example, the timing control unit 41 turns on the selection gate transistor SL via the control circuit 322, causing voltages (analog values) corresponding to the amount of charge stored in the charge storage units CS1 to CS4 to be output from the output terminals O1 to O4 to the pixel signal processing circuit 325. The pixel signal processing circuit 325 converts each of the analog values ​​output from the output terminals O1 to O4 into digital values ​​through A / D conversion processing, and outputs the digital values ​​as storage signals Q1 to Q4.

[0060] Here, the accumulation signal Q1 is a signal value obtained by converting the analog value output from the output terminal O1 into a digital value through A / D conversion processing. The accumulation signal Q2 is a signal value obtained by converting the analog value output from the output terminal O2 into a digital value through A / D conversion processing. The accumulation signal Q3 is a signal value obtained by converting the analog value output from the output terminal O3 into a digital value through A / D conversion processing. The accumulation signal Q4 is a signal value obtained by converting the analog value output from the output terminal O4 into a digital value through A / D conversion processing.

[0061] The distance calculation unit 42 calculates the distance to the object OB using the accumulation signals output during the readout period. Based on each of the accumulation signals Q1 to Q4 and the number of accumulations N, the distance calculation unit 42 calculates a corrected accumulation signal Q# corresponding to the amount of charge accumulated per the same number of accumulations. For example, the distance D to the object OB can be calculated using the following equation (1):

[0062] Q1#=Q1 Q2#=Q2 / 2 Q3#=Q3 / 3 Q4#=Q4 / 4 (1) where, Q1# is a corrected accumulation signal corresponding to accumulation signal Q1. Q2# is a corrected accumulation signal corresponding to accumulation signal Q2. Q3# is a corrected accumulation signal corresponding to accumulation signal Q3. Q4# is a corrected accumulation signal corresponding to accumulation signal Q4.

[0063] The distance calculation unit 42 calculates the distance to the object OB using the corrected accumulation signal Q#. For example, the distance to the object OB can be calculated using the following equation (2). Equation (2) shows an example in which charges corresponding to external light are accumulated in the charge accumulation unit CS1, and charges corresponding to external light and reflected light RL are accumulated in the charge accumulation units CS2 and CS3.

[0064] D = (Q3# - Q1#) / (Q2# + Q3# - 2Q1#) x c / 2 x Ta + c / 2 x Tc ... (2) where, D indicates the distance to the object OB. Q1# is a corrected accumulation signal corresponding to the accumulation signal Q1. Q2# is a corrected accumulation signal corresponding to the accumulation signal Q2. Q3# is a corrected accumulation signal corresponding to the accumulation signal Q3. c indicates the speed of light. Ta indicates the time width during which the light pulse PO is irradiated. Tc indicates the time difference between when the light pulse PO is irradiated and when the readout gate transistor G2 is set to the on state.

[0065] As described above, in the driving using the frame cycle of FIG. 4, in the first driving pattern in the frame cycle, charge is accumulated in each of the four charge accumulation units CS1 to CS4. In the second driving pattern in the frame cycle, charge is accumulated in each of the three charge accumulation units CS2 to CS4. In the third driving pattern, charge is accumulated in each of the two charge accumulation units CS3 to CS4. In the fourth driving pattern, charge is accumulated in one charge accumulation unit CS4. In the first driving pattern, the charge accumulation unit CS with the shortest accumulation delay time is the charge accumulation unit CS1, whose irradiation timing and accumulation timing are simultaneous. Charge is not accumulated in the charge accumulation unit CS1 (first charge accumulation unit) in the second to fourth driving patterns.

[0066] As a result, in the example of FIG. 4, the time (exposure time A described later) during which the pixel 321 that receives reflected light RL coming from a close-distance object accumulates electric charges can be controlled to be short.

[0067] 4, the time (exposure time A) during which the charge accumulation unit CS1 that receives reflected light RL from a close-distance object accumulates charge is the accumulation time To multiplied by the number of times N the first drive pattern is integrated. That is, exposure time A = To × N. On the other hand, the time (exposure time B) during which the charge accumulation unit CS4 that receives reflected light RL from a long-distance object accumulates charge is the accumulation time To multiplied by the sum (4N) of the number of times each of the first to fourth drive patterns is integrated. That is, exposure time B = To × (4N). That is, the exposure time A is controlled to be smaller than the exposure time B.

[0068] In this way, by controlling the time (exposure time A) during which the pixel 321 receives the reflected light RL coming from a close-distance object to be shorter than the exposure time B, it is possible to reduce the number of times that the pixel 321, which receives the reflected light RL coming from a long-distance object, receives the reflected light RL coming from a close-distance object. Therefore, it is possible to accurately measure the distance to the long-distance object.

[0069] Here, another example of a frame period of the embodiment will be described using FIG. 5 . FIG. 5 is a diagram illustrating a frame period of the embodiment. FIG. 5 shows a timing chart of elements corresponding to each of the items "LI," "G1" to "G4," and "GD." Since each of the items "LI," "G1" to "G4," and "GD" is the same as in FIG. 4 , their description will be omitted. Furthermore, the frame period shown in FIG. 5 includes an accumulation period and a readout period, similar to FIG. 4 . During the accumulation period, the cycle period is repeatedly executed a predetermined number of times N. During the cycle period, drive patterns corresponding to the first to fourth drive patterns, respectively, are executed.

[0070] In the frame period shown in Fig. 5, a specific non-accumulation time Ts is set. The non-accumulation time Ts is a time during which charge is not accumulated in the charge accumulation units CS. In the frame period shown in Fig. 5, control is performed so that charge is not accumulated in each of the charge accumulation units CS until the non-accumulation time Ts has elapsed from the irradiation timing.

[0071] 5, in each drive pattern, the reflected light RL arriving at the distance image capture device 1 is received after the non-accumulation time Ts has elapsed since the irradiation timing. In other words, the distance image capture device 1 does not receive reflected light RL arriving before the non-accumulation time Ts has elapsed since the irradiation timing, i.e., reflected light RL arriving from a close-distance object. This prevents the reception of reflected light RL arriving from a close-distance object, thereby reducing the number of times that reflected light RL arriving from a close-distance object is received by the pixel 321 that receives reflected light RL arriving from a long-distance object. This makes it possible to accurately measure the distance to a long-distance object.

[0072] The first drive pattern in Fig. 5 differs from Fig. 4 in that the accumulation timing of the charge accumulation unit CS1 is determined based on the point in time when the non-accumulation time Ts has elapsed since the irradiation timing. On the other hand, the first drive pattern in Fig. 5 is equivalent to the first drive pattern in Fig. 4 in that charges are accumulated in all of the four charge accumulation units CS in sequence.

[0073] Specifically, in the first driving pattern, the timing control unit 41 turns the drain gate transistor GD off and turns the read gate transistor G1 on via the control circuit 322 at a point in time when the non-accumulation time Ts has elapsed since the irradiation timing. After a specific accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off. At the timing when the read gate transistor G1 is turned off, the read gate transistor G2 is turned on. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G3 is turned on. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G4 is turned on. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on.

[0074] In the first driving pattern of FIG. 5, after the non-accumulation time Ts has elapsed from the irradiation timing, driving to accumulate charges in the charge accumulation units CS1 to CS4 in order is repeated a predetermined number of times N.

[0075] 5 differs from Fig. 4 in that the reference point is the time point when the non-accumulation time Ts has elapsed since the irradiation timing, but is equivalent to the second drive pattern in Fig. 4 in that charge is accumulated in the three charge accumulation units CS2 to CS4 in sequence, excluding the charge accumulation unit CS1 with the shortest accumulation delay time. In the second drive pattern, after the non-accumulation time Ts has elapsed since the irradiation timing, and further after the accumulation time To during which charge was accumulated in the charge accumulation unit CS1 in the first frame has elapsed, driving to accumulate charge in the charge accumulation units CS2 to CS4 in sequence is repeatedly executed a predetermined number of times N.

[0076] Specifically, in the second driving pattern, the timing control unit 41, via the control circuit 322, turns the drain gate transistor GD off and turns the read gate transistor G2 on after the non-accumulation time Ts has elapsed since the irradiation timing and after the accumulation time To has elapsed. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G3 is turned on. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G4 is turned on. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on.

[0077] 5 differs from Fig. 4 in that the reference point is the point when the non-accumulation time Ts has elapsed from the irradiation timing, but is equivalent to the third drive pattern in Fig. 4 in that charge is accumulated in the two charge accumulation units CS3 and CS4 in sequence, excluding the two charge accumulation units CS1 and CS2 with short accumulation delay times. In the third drive pattern, such driving in which charge is accumulated in the charge accumulation units CS3 and CS4 in sequence is repeated a predetermined number of times N.

[0078] Specifically, in the third driving pattern, the timing control unit 41 controls the control circuit 322 to turn off the drain gate transistor GD and turn on the read gate transistor G3 after the non-accumulation time Ts has elapsed since the irradiation timing and after an accumulation time To×2 has elapsed. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 was turned off, the read gate transistor G4 is turned on. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on.

[0079] 5 differs from Fig. 4 in that the reference point is the point when the non-accumulation time Ts has elapsed from the irradiation timing, but is equivalent to the fourth drive pattern in Fig. 4 in that charge is accumulated only in the single charge accumulation unit CS4 with the longest accumulation delay time. In the fourth drive pattern, such driving that accumulates charge only in the charge accumulation unit CS4 is defined as a fourth accumulation period, and driving corresponding to the fourth accumulation period is repeatedly executed a predetermined number of times N.

[0080] Specifically, in the fourth driving pattern, the timing control unit 41 turns off the drain gate transistor GD and turns on the read gate transistor G4 after the non-accumulation time Ts has elapsed from the irradiation timing and after an accumulation time To×3 has elapsed, via the control circuit 322. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on.

[0081] The readout period in Fig. 5 is the same as the readout period in Fig. 4, and therefore its description will be omitted. The distance calculation unit 42 can calculate the distance to the subject OB using the accumulation signal output during the readout period, similar to the method described in Fig. 4.

[0082] 5, the accumulation timing of the charge accumulation unit CS1 (first charge accumulation unit), which has the shortest accumulation delay time, is set to the timing after the predetermined non-accumulation time Ts has elapsed from the irradiation timing. This prevents the pixel 321, which receives reflected light RL from a close object, from receiving reflected light RL from a long-distance object, thereby reducing the number of times that the pixel 321 receives reflected light RL from a close object. This makes it possible to accurately measure the distance to a long-distance object.

[0083] Here, another example of a frame period of an embodiment will be described using FIG. 6 (FIGS. 6A to 6C). FIG. 6 is a diagram illustrating a frame period of an embodiment. FIG. 6 shows a timing chart of elements corresponding to each of the items "LI," "G1" to "G4," and "GD." Each of the items "LI," "G1" to "G4," and "GD" is the same as in FIG. 4, and therefore description thereof will be omitted. Furthermore, the frame period shown in FIG. 6 includes an accumulation period and a readout period, similar to FIG. 4. During the accumulation period, a cycle period is repeatedly executed a predetermined number of times N. During the cycle period, drive patterns corresponding to the first to fourth drive patterns, respectively, are executed.

[0084] In the frame period shown in FIG. 6A , a specific reflected light receiving time Tth is set. The reflected light receiving time Tth is the time from when the light pulse PO is emitted until the reflected light RL is received by the distance image capturing device 1, and corresponds to the measurable distance. That is, the reflected light RL arrives during the period from the irradiation timing until the reflected light receiving time Tth has elapsed (the reflected light receiving period). In other words, the reflected light RL does not arrive during a time period different from the reflected light receiving period. During this time period when the reflected light RL does not arrive, charge is accumulated in the charge accumulation unit CS that did not accumulate charge during the reflected light receiving period. By operating in this manner, the number of integration times for each charge accumulation unit CS is the same during the frame period.

[0085] In the frame cycle shown in Fig. 6A, during the period from the irradiation timing until the reflected light receiving time Tth has elapsed (the reflected light receiving section), driving similar to that shown in Fig. 4 is performed. Then, among the drive patterns, in a drive pattern in which there is a charge storage unit CS in which no charge has been stored, charge is stored in the charge storage unit CS that did not store charge in the reflected light receiving section after the reflected light receiving time Tth has elapsed from the irradiation timing (a time section different from the reflected light receiving section), that is, in a time section in which reflected light RL does not arrive.

[0086] As a result, in the frame cycle shown in FIG. 6A , all charge accumulation units CS accumulate charge in each drive pattern, and the number of integrations for each charge accumulation unit CS in one frame can be the same. In other words, the ambient light signal Qb (a signal value corresponding to the amount of charge accumulated in the charge accumulation unit CS in response to the amount of ambient light) included in each accumulation signal Q is the same. Therefore, for each accumulation signal Q, a uniform ambient light signal Qb can be used to calculate an accumulation signal (external light subtracted accumulation signal Qa) that does not include an ambient light component. Furthermore, since the number of times the ambient light component is accumulated is increased compared to the driving shown in FIGS. 4 and 5 , it is possible to calculate an ambient light signal Qb with reduced variations in ambient light. This allows for accurate calculation of the ambient light signal Qb, and therefore the value of the ambient light signal Qb to be subtracted from the accumulation signal Q can be accurately calculated. This makes it possible to accurately calculate the distance to the subject OB.

[0087] The first drive pattern in FIG. 6A is equivalent to the first drive pattern in FIG. 4, and therefore a description thereof will be omitted.

[0088] The second drive pattern of Figure 6A accumulates charge in each of the charge accumulation units CS2 to CS4 during the reflected light receiving period at the same accumulation timing as the second drive pattern of Figure 4, and accumulates charge in the charge accumulation unit CS1 during a time period different from the reflected light receiving period, i.e., a time period in which reflected light RL does not arrive.

[0089] Specifically, in the second driving pattern, the timing control unit 41, via the control circuit 322, turns the drain gate transistor GD off and turns the read gate transistor G2 on after the accumulation time To has elapsed since the irradiation timing. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G3 is turned on. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G4 is turned on. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on. Then, after the reflected light receiving time Tth has elapsed since the irradiation timing, the drain gate transistor GD is turned off and the read gate transistor G1 is turned on. After the read gate transistor G1 is turned on and the storage time To has elapsed, the read gate transistor G1 is turned off and the drain gate transistor GD is turned on.

[0090] In this way, in the second drive pattern, charge is accumulated in the charge accumulation unit CS1 during a time interval different from the reflected light receiving interval. Reflected light RL does not arrive during a time interval different from the reflected light receiving interval. Therefore, in the second drive pattern, only charge corresponding to ambient light is accumulated in the charge accumulation unit CS1. In the second drive pattern, such driving, in which charge is accumulated in the charge accumulation units CS2 to CS4 in order during the reflected light receiving interval and charge is accumulated in the charge accumulation unit CS1 during a time interval different from the reflected light receiving interval, is repeated a predetermined number of times N.

[0091] The third driving pattern of Figure 6A accumulates charges in each of the charge accumulation units CS3 to CS4 during the reflected light receiving period at the same accumulation timing as the third driving pattern of Figure 4, and then accumulates charges in the charge accumulation units CS1 to CS2 during a time period different from the reflected light receiving period, i.e., a time period during which reflected light RL does not arrive.

[0092] Specifically, in the third driving pattern, the timing control unit 41, via the control circuit 322, turns the drain gate transistor GD off and turns the read gate transistor G3 on after the accumulation time To×2 has elapsed since the irradiation timing. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G4 is turned on. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on. Then, after the reflected light receiving time Tth has elapsed since the irradiation timing, the drain gate transistor GD is turned off and the read gate transistor G1 is turned on. After the accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off. At the timing when the read gate transistor G1 is turned off, the read gate transistor G2 is turned on. After the read gate transistor G2 is turned on and the storage time To has elapsed, the read gate transistor G2 is turned off and the drain gate transistor GD is turned on.

[0093] In this way, in the third drive pattern, charge is accumulated in the charge accumulation units CS1 and CS2 during a time interval different from the reflected light receiving interval. Reflected light RL does not arrive during a time interval different from the reflected light receiving interval. Therefore, in the third drive pattern, only charge corresponding to ambient light is accumulated in the charge accumulation units CS1 and CS2. In the third drive pattern, such driving, in which charge is accumulated in the charge accumulation units CS3 and CS4 in sequence during the reflected light receiving interval and charge is accumulated in the charge accumulation units CS1 and CS2 during a time interval different from the reflected light receiving interval, is repeated a predetermined number of times N.

[0094] The fourth driving pattern of Figure 6A accumulates charge in the charge accumulation unit CS4 during the reflected light receiving period at the same accumulation timing as the fourth driving pattern of Figure 4, and then accumulates charge in the charge accumulation units CS1 to CS3 during a time period different from the reflected light receiving period.

[0095] Specifically, in the fourth driving pattern, the timing control unit 41, via the control circuit 322, turns the drain gate transistor GD off and turns the read gate transistor G4 on after the accumulation time To×3 has elapsed since the irradiation timing. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on. Then, after the reflected light receiving time Tth has elapsed since the irradiation timing, the drain gate transistor GD is turned off and the read gate transistor G1 is turned on. After the accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off. At the timing when the read gate transistor G1 is turned off, the read gate transistor G2 is turned on. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G3 is turned on. After the read gate transistor G3 is turned on and the storage time To has elapsed, the read gate transistor G3 is turned off and the drain gate transistor GD is turned on.

[0096] In this way, in the fourth drive pattern, charge is accumulated in the charge accumulation units CS1 to CS3 during a time interval different from the reflected light receiving interval. Reflected light RL does not arrive during a time interval different from the reflected light receiving interval. Therefore, in the fourth drive pattern, only charge corresponding to ambient light is accumulated in the charge accumulation units CS1 to CS3. In the fourth drive pattern, such driving, in which charge is accumulated only in the charge accumulation unit CS4 during the reflected light receiving interval and charge is accumulated in the charge accumulation units CS1 to CS3 during a time interval different from the reflected light receiving interval, is repeatedly executed a predetermined number of times N.

[0097] The readout period in Fig. 6A is the same as the readout period in Fig. 4, and therefore its description will be omitted. The distance calculation unit 42 calculates the distance to the subject OB using the accumulation signal output during the readout period.

[0098] First, the distance calculation unit 42 calculates the external light signal Qb. For example, the distance calculation unit 42 sets the smallest signal value among the accumulation signals Q1 to Q4 as the value of the external light signal Qb. That is, the external light signal Qb = min (Q1, Q2, Q3, Q4). The distance calculation unit 42 calculates an external light-subtracted accumulation signal Qa by subtracting the external light signal Qb from each of the accumulation signals Q1 to Q4. Specifically, the external light-subtracted accumulation signal Qa can be calculated using the following equation (3):

[0099] Qa1=Q1-Qb Qa2=Q2-Qb Qa3=Q3-Qb Qa4=Q4-Qb ... (3) where, Qa1 is the external light subtraction accumulation signal corresponding to accumulation signal Q1. Qa2 is the external light subtraction accumulation signal corresponding to accumulation signal Q2. Qa3 is the external light subtraction accumulation signal corresponding to accumulation signal Q3. Qa4 is the external light subtraction accumulation signal corresponding to accumulation signal Q4. Qb is the external light signal.

[0100] The distance calculation unit 42 calculates the distance D to the subject OB using the external light-subtracted accumulation signal Qa (external light-subtracted accumulation signals Qa1 to Qa4). Based on each of the external light-subtracted accumulation signals Qa1 to Qa4 and the number of accumulations N, the distance calculation unit 42 calculates a correction signal Qa# corresponding to the amount of reflected light accumulated per same number of accumulations. Qa1#=Q1a Qa2#=Q2a / 2 Qa3#=Q3a / 3 Qa4#=Q4a / 4 (4) where, Qa1# is a correction signal corresponding to the external light-subtracted accumulation signal Qa1. Qa2# is a correction signal corresponding to the external light-subtracted accumulation signal Qa2. Qa3# is a correction signal corresponding to the external light-subtracted accumulation signal Qa3. Qa4# is a correction signal corresponding to the external light-subtracted accumulation signal Qa4.

[0101] The distance calculation unit 42 calculates the distance to the object OB using the correction signal Qa# (correction signals Qa1# to Qa4#). For example, the distance D to the object OB can be calculated using the following equation (5). Equation (5) shows an example in which charges corresponding to the reflected light RL are accumulated in the charge accumulation units CS2 and CS3.

[0102] D = (Qa3#) / (Qa2# + Qa3#) × c / 2 × Ta + c / 2 × Tc ... (5) where, D indicates the distance to the subject OB. Qa2# is a correction signal corresponding to the external light subtracted accumulation signal Qa2. Qa3# is a correction signal corresponding to the external light subtracted accumulation signal Qa3. c indicates the speed of light. Ta indicates the time width during which the light pulse PO is irradiated. Tc indicates the time difference between when the light pulse PO is irradiated and when the readout gate transistor G2 is set to the on state.

[0103] As described above, in the driving using the frame cycle of FIG. 6A , in the first drive pattern in the frame cycle, charge is accumulated in each of the four charge accumulation units CS1 to CS4 during the reflected light receiving section. In the second drive pattern in the frame cycle, charge is accumulated in each of the three charge accumulation units CS2 to CS4 during the reflected light receiving section. In the third drive pattern, charge is accumulated in each of the two charge accumulation units CS3 to CS4 during the reflected light receiving section. In the fourth drive pattern, charge is accumulated in one charge accumulation unit CS4 during the reflected light receiving section. In the first drive pattern, the charge accumulation unit CS with the shortest accumulation delay time is charge accumulation unit CS1, whose irradiation timing and accumulation timing are simultaneous. In the second to fourth drive patterns, charge is not accumulated in charge accumulation unit CS1 (first charge accumulation unit) during the reflected light receiving section. Then, in the second to fourth drive patterns, the charge accumulation unit CS1 (first charge accumulation unit) that did not accumulate charge in the reflected light receiving section is made to accumulate charge in a time interval different from the reflected light receiving section. At this time, as a result of accumulating charge in the charge accumulation unit CS in a frame period, the sum of the first and second times is set to be the same as the third number. The first number is the number of times charge is accumulated in the charge accumulation unit CS1 (first charge accumulation unit) in the reflected light receiving section in the first to fourth drive patterns. The second number is the number of times charge is accumulated in the charge accumulation unit CS1 (first charge accumulation unit) in the first to fourth drive patterns in a time interval different from the reflected light receiving section. The third number is the number of times charge is accumulated in the charge accumulation unit CS4 (second charge accumulation unit) in the reflected light receiving section in the first to fourth drive patterns.

[0104] In other words, in the example of Figure 6A, control can be performed so that the number of integrations in each charge accumulation unit CS is the same in one frame period. The time (exposure time X) during which the charge accumulation unit CS1 accumulates charge is the accumulation time To multiplied by the sum (4N) of the number of integrations N for each of the first to fourth drive patterns. In other words, exposure time X = To x (4N). On the other hand, the time (exposure time Y) during which the charge accumulation unit CS4 accumulates charge is the accumulation time To multiplied by the sum (4N) of the number of integrations N for each of the first to fourth drive patterns. In other words, exposure time Y = To x (4N). In other words, exposure time X = exposure time Y. Furthermore, in the reflected light receiving section, pixel 321 is driven in the same manner as in Figure 4, so the time (exposure time A) corresponding to the time for receiving reflected light RL coming from a close-distance object is shorter than exposure time B corresponding to the time for receiving reflected light RL coming from a long-distance object.

[0105] In this way, by controlling the number of accumulations in each charge accumulation unit CS in a frame period to be the same while minimizing the time spent receiving reflected light RL from a close-distance object, the amount of external light signal Qb included in each accumulation signal Q can be made uniform for all accumulation signals Q. Furthermore, by increasing the number of times the external light component is accumulated, it is possible to calculate an external light signal Qb in which variations in external light are suppressed. This makes it possible to accurately calculate the distance to the subject OB.

[0106] Fig. 6B shows a first modification of Fig. 6A. In this modification, the first to fourth drive patterns are performed, followed by a fifth drive pattern (external light accumulation drive pattern). In the fifth drive pattern, the drive patterns in Fig. 6A are all performed together to accumulate charge corresponding to (only) external light in a time period different from the reflected light receiving period (a time period in which reflected light RL does not arrive).

[0107] In Figure 6B, the first to fourth drive patterns are the same as the first to fourth drive patterns in the frame cycle of Figure 4. In the frame cycle of Figure 6B, the fifth drive pattern is executed after the reflected light reception time Tth has elapsed from the start of the fourth drive pattern. In the fifth drive pattern, charge is accumulated three times in the charge accumulation unit CS1, two times in the charge accumulation unit CS2, and once in the charge accumulation unit CS3. This figure shows an example in which charge is accumulated in the following order: charge accumulation unit CS1, charge accumulation unit CS2, charge accumulation unit CS3, charge accumulation unit CS1, charge accumulation unit CS2, and charge accumulation unit CS1.

[0108] Specifically, in the fifth driving pattern, the timing control unit 41, via the control circuit 322, turns the drain gate transistor GD off and turns the read gate transistor G1 on after the reflected light receiving time Tth has elapsed since the start of the fourth driving pattern. After the accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off. At the timing when the read gate transistor G1 is turned off, the read gate transistor G2 is turned on. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G3 is turned on. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G1 is turned on. After the accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off. At the same time that the read gate transistor G1 is turned off, the read gate transistor G2 is turned on. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the same time that the read gate transistor G2 is turned off, the read gate transistor G1 is turned on. After the accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off and the drain gate transistor GD is turned on.

[0109] In this way, in the fifth drive pattern of FIG. 6B , by accumulating charges corresponding only to external light without irradiating the light pulse PO, the number of integrations in each charge accumulation unit CS is the same in a frame period. By providing the fifth drive pattern, the time required to execute each drive pattern (first drive pattern to fourth drive pattern) can be shortened compared to FIG. 6A . This allows the cycle period of FIG. 6B to be shorter than that of FIG. 6A . As a result, when the time required for driving one frame is set to be the same in FIG. 6A and FIG. 6B , the shorter cycle period in FIG. 6B makes it possible to lengthen the accumulation time or increase the number of integrations. In other words, the time (exposure time) for accumulating charges in each charge accumulation unit CS in one frame can be lengthened. By lengthening the exposure time, the signal-to-noise ratio (SN) of the accumulation signal can be improved, thereby improving the accuracy of the distance D to the subject OB. Furthermore, when the accumulation time and number of integrations are not changed between FIG. 6A and FIG. 6B , the cycle period is shorter in FIG. 6B than in FIG. 6A , making it possible to shorten the time required for driving one frame. That is, since the measurement time can be shortened in FIG. 6B, it becomes possible to measure a fast-moving subject with high accuracy.

[0110] Fig. 6C shows a second modification of Fig. 6A. In this modification, first, the first to third drive patterns of Fig. 6A are performed. Next, after the first to third drive patterns are performed, driving related to the accumulation of charge corresponding to external light (only) in a time period different from the reflected light receiving period (a time period in which reflected light RL does not arrive) is performed collectively as a fourth drive pattern (external light accumulation drive pattern).

[0111] In the second modification, a plurality of different drive patterns may be executed in the drive that accumulates charge in the reflected light receiving section during one frame period, and three drive patterns, a first drive pattern, a third drive pattern, and a fourth drive pattern, may be executed as shown in Fig. 6C. Note that the configuration may also be such that at least two or more drive patterns among the first drive pattern, the second drive pattern, the third drive pattern, the fourth drive pattern, the second drive pattern, the third drive pattern, the fourth drive pattern, and the third drive pattern are executed. Examples of the at least two drive patterns among the first drive pattern, the third drive pattern, the fourth drive pattern, and the fourth drive pattern include any combination of the first drive pattern and the second drive pattern, the first drive pattern and the third drive pattern, the second drive pattern and the fourth drive pattern, and the third drive pattern and the fourth drive pattern.

[0112] In Fig. 6C, the first to third drive patterns are the same as the first to third drive patterns in the frame cycle of Fig. 4. In the frame cycle of Fig. 6C, the fourth drive pattern is executed after the reflected light reception time Tth has elapsed from the start of the third drive pattern. In the fourth drive pattern, charge is accumulated twice in the charge accumulation unit CS1 and once in the charge accumulation unit CS2. This figure shows an example in which charge is accumulated in the order of charge accumulation unit CS1, charge accumulation unit CS2, and charge accumulation unit CS1.

[0113] 6C , the timing control unit 41, via the control circuit 322, turns the drain gate transistor GD off and turns the read gate transistor G1 on after the reflected light reception time Tth has elapsed since the start of the third drive pattern. After the accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off. At the timing when the read gate transistor G1 is turned off, the read gate transistor G2 is turned on. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G1 is turned on. After the accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off and the drain gate transistor GD is turned on.

[0114] In this way, in the fourth drive pattern of FIG. 6C , charges corresponding only to external light are accumulated without irradiating the light pulse PO. This results in a shorter cycle period in FIG. 6C than in the comparative example in which the fourth drive pattern is omitted from FIG. 6A . As a result, when the time required for one frame of drive is set to be the same in the comparative example and FIG. 6C , the shorter cycle period in FIG. 6C allows for a longer accumulation time or a larger number of integrations. In other words, the exposure time of each charge accumulation unit CS can be increased within a frame period. By increasing the exposure time, the signal-to-noise ratio (SN) of the accumulated signal can be improved, thereby improving the accuracy of the distance D to the object OB. Furthermore, when the accumulation time and number of integrations are not changed between the comparative example and FIG. 6C , the shorter cycle period in FIG. 6C allows for a shorter time required for one frame of drive. In other words, the shorter measurement time in FIG. 6C allows for accurate measurement of fast-moving objects.

[0115] Here, another example of a frame period of the embodiment will be described using FIG. 7 (FIGS. 7A and 7B). FIG. 7 is a diagram illustrating a frame period of the embodiment. FIG. 7 shows a timing chart of elements corresponding to each of the items "LI," "G1" to "G4," and "GD." Each of the items "LI," "G1" to "G4," and "GD" is the same as in FIG. 4, and therefore description thereof will be omitted. Furthermore, the frame period shown in FIG. 7 includes an accumulation period and a readout period, similar to FIG. 4. During the accumulation period, a cycle period is repeatedly executed a predetermined number of times N of integration. During the cycle period, drive patterns corresponding to the first to fourth drive patterns, respectively, are executed.

[0116] In the frame period shown in FIG. 7A, both the non-accumulation time Ts shown in FIG. 5 and the reflected light receiving time Tth shown in FIG. 6A are set.

[0117] In the frame cycle shown in Fig. 7A, charge is not accumulated in each charge accumulation unit CS until the non-accumulation time Ts has elapsed from the irradiation timing, and driving similar to that in Fig. 5 is performed in the reflected light receiving section. Then, as in Fig. 6A, in a drive pattern in which there is a charge accumulation unit CS in which charge is not accumulated, charge is accumulated in the charge accumulation unit CS that did not accumulate charge in the reflected light receiving section in a time section different from the reflected light receiving section.

[0118] 7A , in each drive pattern, the distance image capture device 1 does not receive reflected light RL that arrives before the non-accumulation time Ts has elapsed since the irradiation timing, i.e., reflected light RL that arrives from a close-distance object, and the number of integration times for each charge storage unit CS in one frame is the same. This reduces the number of times that reflected light RL that arrives from a close-distance object is received by the pixel 321 that receives reflected light RL from a long-distance object, and simplifies the process of calculating the distance.

[0119] The first drive pattern in FIG. 7A is equivalent to the first drive pattern in FIG. 5, and therefore a description thereof will be omitted.

[0120] In the second driving pattern of Figure 7A, based on the point when the non-accumulation time Ts has elapsed from the irradiation timing, charge is accumulated in each of the charge accumulation units CS2 to CS4 during the reflected light receiving period, and charge is accumulated in the charge accumulation unit CS1 during a time period different from the reflected light receiving period.

[0121] Specifically, in the second driving pattern, the timing control unit 41, via the control circuit 322, turns the drain gate transistor GD off and turns the read gate transistor G2 on after the non-accumulation time Ts has elapsed since the irradiation timing and after the accumulation time To has elapsed. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G3 is turned on. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G4 is turned on. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on. Then, after the reflected light receiving time Tth has elapsed since the irradiation timing, the drain gate transistor GD is turned off and the read gate transistor G1 is turned on. After the read gate transistor G1 is turned on and the storage time To has elapsed, the read gate transistor G1 is turned off and the drain gate transistor GD is turned on.

[0122] In the second drive pattern, the second accumulation period is defined as a drive in which charges are accumulated in charge accumulation units CS2 to CS4 in sequence during the reflected light receiving section, based on the point in time when the non-accumulation time Ts has elapsed since the irradiation timing, and charges are accumulated in charge accumulation unit CS1 during a time period different from the reflected light receiving section, and the drive corresponding to the second accumulation period is repeatedly executed a predetermined number of times N.

[0123] In the third driving pattern of Figure 7A, based on the point when the non-accumulation time Ts has elapsed from the irradiation timing, charge is accumulated in each of the charge accumulation units CS3 to CS4 during the reflected light receiving period, and charge is accumulated in the charge accumulation units CS1 to CS2 during a time period different from the reflected light receiving period.

[0124] Specifically, in the third driving pattern, the timing control unit 41, via the control circuit 322, turns off the drain gate transistor GD and turns on the read gate transistor G3 after a non-accumulation time Ts has elapsed since the irradiation timing and after an accumulation time To×2 has elapsed. After the accumulation time To has elapsed since the read gate transistor G3 was turned on, the read gate transistor G3 is turned off. At the timing when the read gate transistor G3 is turned off, the read gate transistor G4 is turned on. After the accumulation time To has elapsed since the read gate transistor G4 was turned on, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on. Then, after a reflected light receiving time Tth has elapsed since the irradiation timing, the drain gate transistor GD is turned off and the read gate transistor G1 is turned on. After the accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off. At the timing when the read gate transistor G1 is turned off, the read gate transistor G2 is turned on. After the read gate transistor G2 is turned on and the storage time To has elapsed, the read gate transistor G2 is turned off and the drain gate transistor GD is turned on.

[0125] In the third driving pattern, such driving is repeated a predetermined number of times N, with the point in time when the non-accumulation time Ts has elapsed from the irradiation timing as the reference point, to accumulate charges in the charge accumulation units CS3 to CS4 in sequence during the reflected light receiving period, and accumulate charges in the charge accumulation units CS1 to CS2 during a time period different from the reflected light receiving period.

[0126] In the fourth driving pattern of Figure 7A, based on the point when the non-accumulation time Ts has elapsed from the irradiation timing, charge is accumulated in the charge accumulation unit CS4 during the reflected light receiving period, and charge is accumulated in the charge accumulation units CS1 to CS3 during a time period different from the reflected light receiving period.

[0127] Specifically, in the fourth driving pattern, the timing control unit 41, via the control circuit 322, turns the drain gate transistor GD off and turns the read gate transistor G4 on after a non-accumulation time Ts has elapsed since the irradiation timing and after an accumulation time To×3 has elapsed. After the read gate transistor G4 is turned on and an accumulation time To has elapsed, the read gate transistor G4 is turned off and the drain gate transistor GD is turned on. Then, after a reflected light receiving time Tth has elapsed since the irradiation timing, the drain gate transistor GD is turned off and the read gate transistor G1 is turned on. After the accumulation time To has elapsed since the read gate transistor G1 was turned on, the read gate transistor G1 is turned off. At the timing when the read gate transistor G1 is turned off, the read gate transistor G2 is turned on. After the accumulation time To has elapsed since the read gate transistor G2 was turned on, the read gate transistor G2 is turned off. At the timing when the read gate transistor G2 is turned off, the read gate transistor G3 is turned on. After the read gate transistor G3 is turned on and the storage time To has elapsed, the read gate transistor G3 is turned off and the drain gate transistor GD is turned on.

[0128] In the fourth driving pattern, such driving is repeated a predetermined number of times N, accumulating charge in the charge accumulation unit CS4 during the reflected light receiving period, based on the point at which the non-accumulation time Ts has elapsed since the irradiation timing, and accumulating charge in the charge accumulation units CS1 to CS3 during a time period different from the reflected light receiving period.

[0129] The readout period in Fig. 7A is the same as the readout period in Fig. 4, and therefore its description will be omitted. The distance calculation unit 42 can calculate the distance to the subject OB using the accumulation signal output during the readout period, similar to the method described in Fig. 6A.

[0130] 7A , in a plurality of drive patterns, control is performed so that reflected light RL that arrives at the range image capture device 1 before the non-accumulation time Ts has elapsed from the irradiation timing is not received. Then, control is performed so that exposure time A<exposure time B in the reflected light receiving section and exposure time X=exposure time Y in the frame period.

[0131] As a result, the distance image capturing device 1 does not receive reflected light RL that arrives before the non-accumulation time Ts has elapsed from the irradiation timing, and by making exposure time A<exposure time B in the reflected light receiving section, it is possible to reduce the number of times reflected light RL that arrives from a close object is received by the pixel 321 that receives reflected light RL that arrives from a long-distance object. Furthermore, by controlling exposure time X=exposure time Y in the frame period, it is possible to simplify the process of calculating the distance.

[0132] Fig. 7B shows a first modification of Fig. 7A. In this modification, the first to fourth drive patterns are performed, followed by a fifth drive pattern (external light accumulation drive pattern). In the fifth drive pattern, the drive patterns in Fig. 7A are all performed together to accumulate charge corresponding to (only) external light in a time period different from the reflected light receiving period (a time period in which reflected light RL does not arrive).

[0133] In Fig. 7B, the first to fourth drive patterns are the same as the first to fourth drive patterns in the frame cycle of Fig. 5. In the frame cycle of Fig. 7B, the fifth drive pattern is executed after the reflected light reception time Tth has elapsed from the start of the fourth drive pattern. The fifth drive pattern of Fig. 7B is the same as the fifth drive pattern of Fig. 6B.

[0134] In this way, in the fifth drive pattern of FIG. 7B , by accumulating charges corresponding only to external light without irradiating the light pulse PO, the number of integrations in each charge accumulation unit CS is the same in a frame period. By providing the fifth drive pattern, the time required to execute each drive pattern (first drive pattern to fourth drive pattern) can be shortened compared to FIG. 7A . This allows the cycle period of FIG. 7B to be shorter than that of FIG. 7A . As a result, when the time required for driving one frame is set to be the same in FIG. 7A and FIG. 7B , the shorter cycle period in FIG. 7B makes it possible to lengthen the accumulation time or increase the number of integrations. In other words, the time (exposure time) for accumulating charges in each charge accumulation unit CS in one frame can be lengthened. By lengthening the exposure time, the signal-to-noise ratio (SN) of the accumulation signal can be improved, thereby improving the accuracy of the distance D to the subject OB. Furthermore, when the accumulation time and number of integrations are not changed between FIG. 7A and FIG. 7B , the cycle period is shorter in FIG. 6B than in FIG. 7A , thereby shortening the time required for driving one frame. In other words, since the measurement time can be shortened in Fig. 7B, it is possible to accurately measure a fast-moving subject. As explained in the example of Fig. 6C, the examples shown in Figs. 7A and 7B may also be configured to execute at least two or more drive patterns from the first to fourth drive patterns. The at least two drive patterns from the first to fourth drive patterns include any combination of the first and second drive patterns, the first and third drive patterns, the first and fourth drive patterns, the second and third drive patterns, the second and fourth drive patterns, and the third and fourth drive patterns, for example.

[0135] Here, the flow of processing performed by the distance imaging device 1 will be described with reference to Fig. 8. Fig. 8 is a flowchart showing the flow of processing performed by the distance imaging device 1 according to the embodiment. Fig. 8 shows the flow of processing for calculating the distance to the subject OB after driving according to the frame period.

[0136] Step S10: The distance imaging device 1 reads out the accumulation signals Q1 to Q4. Step S11: The distance imaging device 1 calculates the external light-subtracted accumulation signals Qa1 to Qa4. For example, the distance imaging device 1 sets the smallest signal value among the accumulation signals Q1 to Q4 as the external light signal Qb, which corresponds to the amount of external light only. The distance imaging device 1 calculates the external light-subtracted accumulation signals Qa1 to Qa4 by subtracting the external light signal Qb from each of the accumulation signals Q1 to Q4, as shown in equation (3). Step S12: The distance imaging device 1 calculates corrected accumulation signals (Qa1# to Q4a#). The distance imaging device 1 calculates the corrected accumulation signals (Qa1# to Qa4#) by normalizing the external light-subtracted accumulation signals Qa1 to Qa4 according to the number of accumulations N. The distance imaging device 1 calculates corrected accumulation signals (Qa1# to Q4a#) by normalizing the external light subtraction post-accumulation signals Qa1 to Qa4 by a value corresponding to the number of accumulations N, as shown in equation (4), for example. Step S13: The distance imaging device 1 calculates the distance to the subject OB using the corrected accumulation signals (Qa1# to Qa4#). Step S14: The distance imaging device 1 determines whether the drive performed in the frame period is a drive provided with a non-accumulation time Ts. Step S15: If the drive is a drive provided with a non-accumulation time Ts, the distance imaging device 1 corrects the distance calculated in step S13 in accordance with the non-accumulation time Ts.

[0137] As described above, the distance image capturing device 1 of the embodiment includes a light source unit 2, a light receiving unit 3, and a distance image processing unit 4. The light source unit 2 irradiates a light pulse PO onto the object OB. The light receiving unit 3 includes pixels 321 each including a photoelectric conversion element PD and a plurality of charge accumulation units CS, and a control circuit 322 (pixel drive circuit). The photoelectric conversion element PD generates electric charge in response to incident light. The charge accumulation units CS accumulate the electric charge. The vertical scanning circuit 323 distributes and accumulates the electric charge in each of the charge accumulation units CS at an accumulation timing synchronized with the irradiation of the light pulse PO according to a frame period. The distance image processing unit 4 controls the control circuit 322 (pixel drive circuit) to accumulate electric charge in each of the charge accumulation units CS. The distance image processing unit 4 calculates the distance D to the object OB based on the amount of electric charge accumulated in each of the charge accumulation units CS. The distance image processing unit 4 is provided with multiple drive patterns, and as a result of driving the multiple drive patterns, the charge accumulation units CS with shorter accumulation delay times receive light fewer times than the charge accumulation units CS with longer accumulation delay times. The number of light receptions is the number of times charge is accumulated in the charge accumulation units CS during the reflected light reception interval. As a result, the distance image capturing device 1 of the embodiment can control the time (exposure time A) during which the pixels 321 receiving reflected light RL from close-distance objects accumulate charge to be shorter, thereby reducing the number of times that the pixels 321 receiving reflected light RL from long-distance objects receive reflected light RL from close-distance objects. This makes it possible to accurately measure the distance to long-distance objects.

[0138] Furthermore, in the range imaging device 1 of the embodiment, a first drive pattern among a plurality of drive patterns causes charge to be accumulated in each of a plurality of N (N≧2) charge accumulation units CS. In a second drive pattern, charge is accumulated in M ​​(M<N) charge accumulation units CS. Then, in the first drive pattern, the first charge accumulation unit CS having the shortest accumulation delay time is not allowed to accumulate charge in the second drive pattern. As a result, in the range imaging device 1 of the embodiment, the time (exposure time A) during which the pixel 321 receiving reflected light RL from a close-distance object accumulates charge can be controlled to be short, thereby achieving the same effect as described above.

[0139] Furthermore, in the distance imaging device 1 of the embodiment, the accumulation timing of the charge accumulation unit CS1 (first charge accumulation unit), which has the shortest accumulation delay time, is set to the timing after a predetermined non-accumulation time Ts has elapsed from the irradiation timing. As a result, the distance imaging device 1 of the embodiment does not receive reflected light RL coming from close-distance objects, and can reduce the number of times that reflected light RL coming from close-distance objects is received by the pixels 321 that receive reflected light RL coming from long-distance objects, thereby achieving the same effect as described above.

[0140] Furthermore, in the range image capturing device 1 according to the embodiment, in the second drive pattern, the charge accumulation unit CS1 (first charge accumulation unit) that did not accumulate charge during the reflected light receiving period is caused to accumulate charge during a time period different from the reflected light receiving period. In this case, the sum of the first and second times of accumulating charge in the charge accumulation unit CS in each of the multiple drive patterns is set to be equal to the third number of times. The first number of times is the number of times charge is accumulated in the charge accumulation unit CS1 (first charge accumulation unit) during the reflected light receiving period. The second number of times is the number of times charge is accumulated in the charge accumulation unit CS1 (first charge accumulation unit) during a time period different from the reflected light receiving period. The third number of times is the number of times charge is accumulated in the charge accumulation unit CS4 (second charge accumulation unit) during the reflected light receiving period. As a result, in the distance image capturing device 1 of the embodiment, the number of times that the pixel 321 that receives reflected light RL coming from a long-distance object receives reflected light RL coming from a close-distance object can be reduced, and the process of calculating the distance can be simplified.

[0141] Furthermore, the distance imaging device 1 of the embodiment has an external light accumulation drive pattern that accumulates charge corresponding to only external light without irradiating the device with further light pulses PO after the plurality of drive patterns. The external light accumulation drive pattern accumulates charge in the charge accumulation unit CS1 (first charge accumulation unit) that did not accumulate charge in the second drive pattern. The accumulation timing of the first charge accumulation unit in the external light accumulation drive pattern is the timing after the reflected light reception time Tth has elapsed from the irradiation timing of the last drive pattern among the plurality of drive patterns. This improves the signal-to-noise ratio of the accumulation signal, thereby improving the accuracy of the distance D to the subject OB. Alternatively, it becomes possible to accurately measure a fast-moving subject.

[0142] All or part of the distance image capturing device 1 and distance image processing unit 4 in the above-described embodiment may be implemented by a computer. In this case, a program for implementing this function may be recorded on a computer-readable recording medium, and the program may be loaded and executed by a computer system. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into a computer system. Furthermore, the term "computer-readable recording medium" may also include media that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or media that store programs for a fixed period of time, such as volatile memory within a computer system that serves as a server or client. The program may be a program that implements part of the above-described functions, or may be a program that can implement the above-described functions in combination with a program already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA.

[0143] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0144] REFERENCE SIGNS LIST 1...Distance image capturing device 2...Light source section 3...Light receiving section 32...Distance image sensor 321...Pixel (pixel circuit) 4...Distance image processing section 42...Distance calculation section CS...Charge storage section PO...Light pulse RL...Reflected light

Claims

1. A light receiving unit having: a light source unit which irradiates a subject with a light pulse; pixels each having a photoelectric conversion element which generates a charge according to the incident light and a plurality of charge accumulation units which accumulate the charge; and a pixel drive circuit which distributes and accumulates charge in each of the charge accumulation units at an accumulation timing synchronized with the irradiation timing of the light pulse; and a distance image processing unit which controls the pixel drive circuit to accumulate charge in each of the charge accumulation units and calculates the distance to the subject based on the amount of charge accumulated in each of the charge accumulation units, wherein the distance image processing unit accumulates charge in each of the charge accumulation units using a plurality of drive patterns each having a different number of the charge accumulation units which accumulate charge, and as a result of accumulating charge in the charge accumulation units in each of the plurality of drive patterns, a charge accumulation unit having a smaller accumulation delay time, which is the difference between the irradiation timing and the accumulation timing, receives light less times than a charge accumulation unit having a larger accumulation delay time, the number of times of light reception is the number of times that charge is accumulated in the charge accumulation unit during a reflected light reception period that is a period from the irradiation timing to a reflected light reception time that is a time corresponding to a measurable distance.

2. The distance image capturing device of claim 1, wherein the distance image processing unit accumulates charge in each of N (N≧2) charge accumulation units in a first drive pattern among the plurality of drive patterns, accumulates charge in M ​​(M<N) charge accumulation units in a second drive pattern among the plurality of drive patterns, and does not accumulate charge in a first charge accumulation unit, which is the charge accumulation unit having the shortest accumulation delay time in the first drive pattern, in the second drive pattern.

3. The distance image capturing device according to claim 2, wherein the distance image processing section sets the accumulation timing of the first charge accumulation section to a timing after a predetermined non-accumulation time has elapsed from the irradiation timing.

4. The distance image capturing device of claim 2 or claim 3, wherein the distance image processing unit, in the second drive pattern, causes the first charge accumulation unit to accumulate charge in a time interval different from the reflected light receiving interval, and causes the sum of the first number of times that charge is accumulated in the first charge accumulation unit in the reflected light receiving interval and the second number of times that charge is accumulated in the first charge accumulation unit in a time interval different from the reflected light receiving interval to be the same as the third number of times that charge is accumulated in the second charge accumulation unit, which is the charge accumulation unit different from the first charge accumulation unit, in the reflected light receiving interval.

5. The distance imaging device of claim 2 or 3, further comprising an external light accumulation drive pattern after the plurality of drive patterns, which accumulates charge corresponding to only external light without irradiating the light pulse, wherein the external light accumulation drive pattern accumulates charge in the first charge accumulation section that did not accumulate charge in the second drive pattern, and wherein the accumulation timing of the first charge accumulation section in the external light accumulation drive pattern is a timing after the reflected light reception time has elapsed from the irradiation timing of the last drive pattern among the plurality of drive patterns.

6. A distance image capturing method performed by a distance image capturing device including a light source unit that irradiates a subject with a light pulse, a light receiving unit having pixels each having a photoelectric conversion element that generates a charge corresponding to the incident light and a plurality of charge accumulation units that accumulate the charge, a pixel drive circuit that distributes and accumulates charge in each of the charge accumulation units at an accumulation timing synchronized with the irradiation timing of the light pulse, and a distance image processing unit that controls the pixel drive circuit to accumulate charge in each of the charge accumulation units and calculates a distance to the subject based on the amount of charge accumulated in each of the charge accumulation units, wherein the distance image processing unit accumulates charge in each of the charge accumulation units using a plurality of drive patterns each having a different number of the charge accumulation units that accumulate charge, and as a result of accumulating charge in the charge accumulation units in each of the plurality of drive patterns, a charge accumulation unit having a smaller accumulation delay time, which is the difference between the irradiation timing and the accumulation timing, receives light less times than a charge accumulation unit having a larger accumulation delay time, the number of times of light reception is the number of times that charge is accumulated in the charge accumulation unit during a reflected light reception period that is a period from the irradiation timing to a reflected light reception time that is a time corresponding to a measurable distance.

Images