Distance image capturing device and distance image capturing method

Abstract

To drive pixels such that driving conditions of a first charge accumulation section which first accumulates charges among a plurality of charge accumulation sections, and driving conditions of other charge accumulation sections which accumulate charges second and thereafter become closer to each other.SOLUTION: In a frame period, driving of unit accumulation periods is executed an accumulation number of times. In an adjustment phase, first driving in which charge is not discharged to a charge discharge section and the charge is not accumulated in a charge accumulation section, and second driving in which the charge is discharged through the charge discharge section, are sequentially executed. A pixel is provided with the plurality of charge accumulation sections sharing a common power supply, the first discharge section that is at least one charge discharge section not sharing the power supply with the plurality of charge accumulation sections, and the second discharge section that is at least one charge discharge section sharing the power supply with the plurality of charge accumulation sections. A distance image processing unit excludes the first discharge section from targets of the first driving and the second driving in the adjustment phase, and sets the second discharge section as a target of the first driving and the second driving in the adjustment phase.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distance image capturing device and a distance image capturing method. [Background technology]

[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] The imaging elements (pixels) of such distance imaging devices are provided with a photoelectric conversion unit, multiple charge accumulation units, charge discharge units, etc. The pixels are driven in one frame cycle by repeatedly executing a unit accumulation period in which pulsed light is irradiated onto the subject and the light reflected by the object to be measured (the subject) is incident on the pixel. The unit accumulation period includes an accumulation phase in which charge is accumulated and a discharge phase in which the charge is discharged. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4235729 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even if the same amount of light is incident, there may be a difference in the amount of charge accumulated between the first charge accumulation unit, which accumulates charge first during the accumulation phase, and the other charge accumulation units, which accumulate charge second or later, which causes a deterioration in the accuracy of the distance measurement. One of the factors that causes a difference in the amount of charge accumulated between the first charge accumulation unit and the other charge accumulation units is differences in drive conditions. In drive for a unit accumulation period, the time for executing the accumulation phase is often set to be relatively short, and the time for executing the discharge phase is set to be relatively long. For this reason, the first charge accumulation unit starts accumulating charge when the state where charge is discharged via the charge discharge unit during the discharge phase of the previous unit accumulation period continues for a long period of time, and then switches to a state where charge is not discharged. On the other hand, the other charge accumulation units start accumulating charge when the short-term charge accumulation in the previous charge accumulation unit is completed. Such differences in drive conditions are thought to be one of the factors that cause deterioration in distance accuracy.

[0006] 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 drive pixels so that the drive conditions of a first charge storage section that first stores charge among a plurality of charge storage sections and the other charge storage sections that store charge second or later are similar to each other. [Means for solving the problem]

[0007] The distance image pickup device of the present invention comprises a light source unit that irradiates a subject with light pulses, a distance image sensor in which a plurality of pixels are arranged in a two-dimensional matrix, each pixel having a light source unit that irradiates a subject with light pulses, a photoelectric conversion element that generates charge in response to incident light, a charge drain unit that drains the charge generated by the photoelectric conversion element, and a plurality of charge accumulation units that accumulate the charge generated by the photoelectric conversion element, a light receiving unit having a pixel drive circuit that allocates and accumulates charge in each of the charge accumulation units at an accumulation timing synchronized with the irradiation timing of the light pulse irradiation in a frame period, and a distance image processing unit that calculates the distance to the subject based on the amount of charge accumulated in each of the charge accumulation units, and executes driving of a unit accumulation period a number of times in the frame period, and includes an accumulation phase in which charge is accumulated in the charge accumulation units in sequence at the accumulation timing in the unit accumulation period, and an accumulation phase in which charge is accumulated via the charge drain unit. a discharge phase for discharging a charge; an adjustment phase at the timing of switching from the discharge phase of the previously executed unit accumulation period to the unit accumulation period to be executed this time; a first drive that does not cause the charge discharge section to discharge charge and does not cause the charge storage section to accumulate charge in the adjustment phase; and a second drive that discharges charge via the charge discharge section are executed sequentially; the pixel is provided with a plurality of the charge storage sections that share a power supply, a first discharge section that is at least one of the charge discharge sections that does not share a power supply with the plurality of the charge storage sections, and a second discharge section that is at least one of the charge discharge sections that shares a power supply with the plurality of the charge storage sections; and the distance image processing section excludes the first discharge section from the first drive and the second drive in the adjustment phase, and includes the second discharge section as the first drive and the second drive in the adjustment phase.

[0008] 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 light pulses; a distance image sensor in which a plurality of pixels are arranged in a two-dimensional matrix, each pixel having a photoelectric conversion element that generates charge in response to incident light, a charge discharge unit that discharges the charge generated by the photoelectric conversion element, and a plurality of charge accumulation units that accumulate the charge generated by the photoelectric conversion element; a light receiving unit having a pixel drive circuit that allocates and accumulates charge in each of the charge accumulation units at an accumulation timing synchronized with an irradiation timing of the light pulse irradiation in a frame period; and a distance image processing unit that calculates a distance to the subject based on the amount of charge accumulated in each of the charge accumulation units, the distance image capturing method comprising: an accumulation phase in which driving of a unit accumulation period is executed an accumulation number of times in the frame period, and charge is accumulated in the charge accumulation units sequentially at the accumulation timing in the unit accumulation period; A discharge phase is executed to discharge charge via the charge discharge section, and an adjustment phase is executed at the timing of switching from the discharge phase of the unit accumulation period executed previously to the unit accumulation period to be executed this time, and a first drive that does not cause the charge discharge section to discharge charge and does not cause the charge accumulation section to accumulate charge in the adjustment phase, and a second drive that discharges charge via the charge discharge section are executed sequentially, and the pixel is provided with a plurality of the charge accumulation sections that share a power supply, a first discharge section that is at least one of the charge discharge sections that does not share a power supply with the plurality of the charge accumulation sections, and a second discharge section that is at least one of the charge discharge sections that shares a power supply with the plurality of the charge accumulation sections, and the distance image processing section excludes the first discharge section from the first drive and the second drive in the adjustment phase, and includes the second discharge section as the target of the first drive and the second drive in the adjustment phase. [Effects of the Invention]

[0009] According to the present invention, a pixel can be driven so that the driving conditions of a first charge accumulation section that accumulates charge first among a plurality of charge accumulation sections are similar to the driving conditions of other charge accumulation sections that accumulate charge second or later. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing the configuration of a distance image capturing device 1 according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a range image sensor 32 according to the embodiment. [Figure 3] FIG. 3 is a circuit diagram showing an example of the configuration of a pixel 321 according to an embodiment. [Figure 4A] FIG. 2 is a diagram schematically illustrating an example of a layout pattern of a pixel 321 according to an embodiment. [Figure 4B] 10 is a timing chart showing timings for driving a conventional pixel 321. [Figure 4C] FIG. 4C is a diagram showing an image of pixel signals Q1 to Q4 driven in FIG. 4B. [Figure 5] 10 is a timing chart showing a first example of timing for driving a pixel 321 according to an embodiment. [Figure 6] 10 is a timing chart showing a second example of timing for driving a pixel 321 according to an embodiment. [Figure 7] 10 is a timing chart showing a third example of timing for driving a pixel 321 according to an embodiment. [Figure 8A] FIG. 2 is a diagram schematically illustrating an example of a layout pattern of a pixel 321 according to an embodiment. [Figure 8B] FIG. 2 is a diagram schematically illustrating an example of a layout pattern of a pixel 321 according to an embodiment. [Figure 8C] FIG. 2 is a diagram schematically illustrating an example of a layout pattern of a pixel 321 according to an embodiment. [Figure 9] 10 is a timing chart showing a fourth example of timing for driving a pixel 321 according to an embodiment. [Figure 10] 10 is a timing chart showing a fifth example of timing for driving a pixel 321 according to an embodiment. [Figure 11] 10 is a timing chart showing a sixth example of timing for driving a pixel 321 according to an embodiment. [Figure 12] 10 is a timing chart showing a seventh example of timing for driving a pixel 321 according to an embodiment. [Figure 13] 10 is a timing chart showing an eighth example of timing for driving a pixel 321 according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a distance image capturing device according to an embodiment will be described with reference to the drawings.

[0012] Fig. 1 is a block diagram showing the schematic configuration of a distance image capturing device according to an embodiment. The distance image capturing 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 measured by the distance image capturing device 1.

[0013] The light source unit 2 irradiates the object OB with a light pulse PO in accordance with control from 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.

[0014] 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 pulses PO to be 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.

[0015] The diffusion 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 diffusion plate 22 is emitted as a light pulse PO and is irradiated onto the subject OB.

[0016] The light receiving unit 3 receives reflected light RL of the light pulse PO reflected by the object OB, and outputs a pixel signal corresponding to the received reflected light RL. The light receiving unit 3 includes a lens 31 and a distance image sensor 32.

[0017] The lens 31 is an optical lens that guides the incident reflected light RL to the range image sensor 32. The lens 31 outputs the incident reflected light RL to the range image sensor 32 side, and causes the light to be received (incident) by pixels provided in the light receiving region of the range image sensor 32.

[0018] The range image sensor 32 is an imaging element. 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.

[0019] The range image sensor 32 distributes the charges generated by the photoelectric conversion elements to the respective charge accumulation sections under the control of the timing control section 41. The range image sensor 32 also outputs pixel signals according to the amount of charge distributed to the charge accumulation sections. The range image sensor 32 has multiple pixels arranged in a two-dimensional matrix, and outputs pixel signals for one frame corresponding to each pixel.

[0020] The configuration of the range 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 (range image sensor 32) used in the range image capturing device 1 of the embodiment.

[0021] 2, the range image sensor 32 includes, for example, a light receiving area 320 in which a plurality of pixels 321 are arranged in a two-dimensional matrix, and a pixel drive circuit 322. The pixel drive circuit 322 includes, for example, a vertical scanning circuit 323 having a distribution operation, a horizontal scanning circuit 324, a pixel signal processing circuit 325, and a control circuit 326.

[0022] The light receiving region 320 is a region in which a plurality of pixels 321 are arranged in a two-dimensional matrix, and an example of an 8-row, 8-column arrangement is shown in Fig. 2. The pixels 321 accumulate electric charge corresponding to the amount of light received, and output an accumulation signal corresponding to the amount of accumulated electric charge.

[0023] The control circuit 326 comprehensively controls the range image sensor 32. The control circuit 326 controls the operation of the components of the range image sensor 32, for example, in response to instructions from 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 326 may be omitted.

[0024] The vertical scanning circuit 323 controls the pixels 321 arranged in the light receiving region 320 row by row in accordance with control from the control circuit 326. 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 charges 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. In addition, the vertical scanning circuit 323 discharges the charges converted by the photoelectric conversion elements from a charge discharge unit (a charge discharge transistor GD described later) during a period (e.g., a readout period) different from the accumulation period during which the charges are accumulated in the charge accumulation units CS.

[0025] The pixel signal processing circuit 325 performs predetermined signal processing (for example, 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 326.

[0026] Horizontal scanning circuit 324 outputs the signals output from pixel signal processing circuit 325 sequentially in time series under control of control circuit 326. As a result, one frame's worth of accumulated signals are sequentially output to distance image processing unit 4. In the following description, it is assumed that pixel signal processing circuit 325 performs A / D conversion processing and the accumulated signals are digital signals.

[0027] Here, the configuration of the pixel 321 will be described with reference to Fig. 3. Fig. 3 is a circuit diagram showing an example of the pixel 321. 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. This diagram shows an example in which the pixel 321 has four signal readout units RU (signal readout units RU1 to RU4).

[0028] The pixel 321 includes one photoelectric conversion element PD, a charge discharging transistor GD, and four signal readout units RU that output voltage signals from corresponding output terminals O. Each signal readout unit RU includes a transfer transistor G, a floating diffusion FD, a charge storage capacitance C, a reset transistor RT, a source follower transistor SF, and a selection transistor SL. The charge storage unit CS is composed of the floating diffusion FD and the charge storage capacitance C.

[0029] 3, the four signal readout units RU are distinguished from one another by adding a number from 1 to 4 after the symbol "RU" of each signal readout unit RU. Similarly, the components of each of the four signal readout units RU are distinguished from one another by adding a number representing each signal readout unit RU after the symbol.

[0030] 3, the four signal readout units RU are distinguished from one another by adding a number from 1 to 4 after the symbol "RU" of each signal readout unit RU. Similarly, the components of each of the four signal readout units RU are distinguished from one another by adding a number representing each signal readout unit RU after the symbol.

[0031] In pixel 321, signal readout unit RU1 outputs a voltage signal from output terminal O1. Signal readout unit RU1 includes a transfer transistor G1, a floating diffusion FD1, a charge storage capacitance C1, a reset transistor RT1, a source follower transistor SF1, and a selection transistor SL1. Charge storage unit CS1 is configured with floating diffusion FD1 and charge storage capacitance C1. Signal readout units RU2 to RU4 have a similar configuration.

[0032] The photoelectric conversion element PD is a buried photodiode that photoelectrically converts incident light to generate charges corresponding to the intensity of the incident light and accumulates the generated 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.

[0033] The charge discharging transistor GD is a transistor for discarding the charge generated in the photoelectric conversion element PD. When the charge discharging transistor GD is controlled to the on state by the pixel driving circuit 322, it discards the charge generated in the photoelectric conversion element PD (i.e., resets the photoelectric conversion element PD).

[0034] The pixel driving circuit 322 drives the pixel 321, distributes the electric charges generated by the photoelectric conversion element PD by photoelectrically converting the incident light to each of the four charge accumulation units CS, and outputs voltage signals corresponding to the amount of electric charge of the distributed electric charges to the pixel signal processing circuit 325.

[0035] For example, in driving the pixel 321, the pixel drive circuit 322 controls the accumulation drive signals TX1 to TX4 corresponding to the charge accumulation units CS1 to CS4 to be sequentially turned on in synchronization with the irradiation timing of the light pulse PO. This sequentially turns on the transfer transistors G1 to G4 corresponding to the charge accumulation units CS, and distributes and accumulates the charges in the corresponding charge accumulation units CS. As a result, the charges are accumulated in the charge accumulation units CS1, CS2, CS3, and CS4 in that order.

[0036] 3, the pixel 321 is not limited to a configuration including four signal readout units RU, but may be a pixel including a plurality of signal readout units RU. In other words, the number of signal readout units RU (charge accumulation units CS) included in a pixel arranged in the range image sensor 32 may be two, three, five or more.

[0037] 3 shows an example in which the charge storage unit CS is configured with a floating diffusion FD and a charge storage capacitance C. However, the charge storage unit CS only needs to be configured with at least a floating diffusion FD, and the pixel 321 may not have a charge storage capacitance C.

[0038] 1, distance image processing unit 4 controls distance image pickup device 1 and calculates the distance to subject OB. Distance image processing unit 4 includes a timing control unit 41, a distance calculation unit 42, and a measurement control unit 43.

[0039] 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 that controls whether or not to irradiate a light pulse PO, a signal that controls whether or not to accumulate charge in the charge accumulation unit, and a signal that sets the number of accumulations per frame. The number of accumulations is the number of times that the process of allocating and accumulating charge in the charge accumulation units CS is repeated, and corresponds to the number of allocations set in advance in a frame period. The product of this number of accumulations and the time (accumulation time) for accumulating charge in each charge accumulation unit per process of allocating and accumulating charge is the exposure time.

[0040] The distance calculation unit 42 outputs distance information calculated based on the pixel signals output from the distance image sensor 32. 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 CS. The distance calculation unit 42 calculates the distance to the object OB according to the calculated delay time. The measurement control unit 43 controls the timing control unit 41. For example, the measurement control unit 43 sets the number of accumulations and accumulation time width for one frame, and controls the timing control unit 41 so that imaging is performed according to the set contents. In other words, the measurement control unit 43 sets the frame period, and controls the timing control unit 41 so that imaging is performed according to the set contents.

[0041] Here, the problem of this embodiment will be described with reference to FIG. 4 (FIGS. 4A to 4C).

[0042] 4A schematically shows the layout pattern of a pixel 321. As shown in FIG. 4A, the pixel 321 is an integrated circuit in which a transistor, a transfer transistor G (transfer transistors G1 to G4), and a charge discharge transistor GD (charge discharge transistors GD1 and GD2) are mounted on a photoelectric conversion element PD. The transistor is, for example, an n-channel MOS transistor formed on a p-type semiconductor substrate, and is composed of a drain D (n-diffusion layer (n-type impurity diffusion layer)), a source (n-diffusion layer), and a gate G. In the example of FIG. 4A, transistors other than the transfer transistor G and the charge discharging transistor GD, specifically, transistors such as the charge discharging transistor GD, source follower transistors SF1 to SF4, selection transistors SL1 to SL4, and reset transistors RT1 to RT4 are omitted from the illustration. The photoelectric conversion element PD is formed in the shape of a regular hexagon with two opposing sides longer than the other four sides. The transfer transistors G1 and G3 are arranged on one of the two long sides of the hexagon of the photoelectric conversion element PD so as to be symmetrical with respect to an axis that passes through the center of the hexagon and is perpendicular to the two long sides of the hexagon. The transfer transistors G2 and G4 are arranged on one of the two long sides of the hexagon of the photoelectric conversion element PD other than the side on which the transfer transistors G1 and G3 are arranged so as to be symmetrical with respect to an axis that passes through the center of the hexagon and is perpendicular to the two long sides of the hexagon. The transfer transistors G1 and G2 are arranged so as to be symmetrical with respect to an axis that passes through the center of the hexagon and is parallel to the two long sides of the hexagon. The transfer transistors G3 and G4 are arranged so as to be symmetrical with respect to an axis that passes through the center of the hexagon and is parallel to the two long sides of the hexagon. The charge discharging transistors GD1 and GD2 are arranged at the vertex formed by the connection of two adjacent sides of the four shorter sides of the long hexagon of the photoelectric conversion element PD, so as to be symmetrical with respect to an axis that passes through the center of the long hexagon and is perpendicular to the two longer sides of the long hexagon. In this example, the gate G of the charge drain transistor GD1 is connected to a control signal GD_CL that controls the draining of charge. When the control signal GD_CL is High (1), charge is drained, and when it is Low (0 (zero)), charge is not drained. Furthermore, the gate G of the charge discharging transistor GD2 is fixed to a fixed value (0 (zero)). Therefore, the charge discharging transistor GD2 does not discharge charge at all times. Furthermore, the gates G of the transfer transistors G1 to G4 are connected to control signals G1_CL to G4_CL that control charge accumulation in the charge accumulation units CS1 to CS4 as the corresponding drains D. When the control signal Gk_CL is High (1), charge is accumulated, and when it is Low (0 (zero)), no charge is accumulated. Here, k is any of 1 to 4.

[0043] Fig. 4B is a timing chart showing an example of conventional driving of the pixel 321. The pixel is driven in a frame cycle, and as shown in Fig. 4B, one frame is divided into an accumulation period and a readout period. The accumulation period is a period during which charge is accumulated in the charge accumulation unit CS, and is a period during which driving of the pixel 321 shown in the unit accumulation period is repeated a predetermined number of times. The readout period is a period during which a pixel signal Q corresponding to the amount of charge accumulated in each charge accumulation unit CS is read out.

[0044] FIG. 4B shows a timing chart of elements corresponding to the items "GD," "Fixed to 0," "G1" to "G4," and "LIGHT." "GD" indicates the operation timing of the control signal GD_CL that controls the charge discharging transistor GD1. "Fixed to 0" indicates that the charge discharging transistor GD2 is low (fixed to 0 (zero)). "G1" to "G4" indicate the operation timing of the control signals G1_CL to G4_CL that control the transfer transistors G1 to G4. "LIGHT" indicates the irradiation timing of the light pulse PO. Specifically, the light is irradiated in the on state (when the timing signal is set to high (1)) and extinguished in the off state (when the timing signal is set to low (0 (zero))).

[0045] As shown in FIG. 4B, the unit accumulation period includes an accumulation phase A and a discharge phase B. In the accumulation phase A, first, the charge discharging transistor GD is controlled to be in the off state, and then the transfer transistor G1 is controlled to be in the on state. When an accumulation time (for example, an accumulation time To set corresponding to the irradiation time of the light pulse PO) has elapsed since the charge discharging transistor GD was controlled to be in the off state, the transfer transistor G1 is controlled to be in the off state. Here, the period during which the transfer transistor G1 is controlled to an ON state is the accumulation drive time Tc. The accumulation drive time Tc is set to be shorter than the accumulation time To. During the non-accumulation drive period (= To - Tc) of the accumulation time To during which the transfer transistor G1 is controlled to an OFF state, the charge converted by the photoelectric conversion element PD is accumulated in the photoelectric conversion element PD (not in the charge accumulation unit CS1). By controlling the transfer transistor G1 to an ON state, the charge accumulated in the photoelectric conversion element PD during the non-accumulation drive period moves from the photoelectric conversion element PD to the floating diffusion FD1 and is accumulated in the charge accumulation unit CS1. Furthermore, the charge converted by the photoelectric conversion element PD during the accumulation drive time Tc during which the transfer transistor G1 is controlled to an ON state is accumulated in the charge accumulation unit CS1. In other words, the transfer transistor G1 is controlled to an ON state during the accumulation drive time Tc, and the charge converted by the photoelectric conversion element PD during the accumulation time To is accumulated in the charge accumulation unit CS1. At the timing when the transfer transistor G1 is controlled to the off state, a light pulse PO is irradiated for an irradiation time To. Also, the transfer transistor G1 is controlled to the off state, and then the transfer transistor G2 is controlled to the on state. When the accumulation time To has elapsed since the transfer transistor G1 was controlled to the off state, the transfer transistor G2 is controlled to the off state. The period during which the transfer transistor G2 is controlled to the on state is the accumulation drive time Tc. The transfer transistor G2 is controlled to the off state, and then the transfer transistor G3 is controlled to the on state. When the accumulation time To has elapsed since the transfer transistor G2 was controlled to the off state, the transfer transistor G3 is controlled to the off state. The period during which the transfer transistor G3 is controlled to the on state is the accumulation drive time Tc. The transfer transistor G3 is controlled to the off state, and then the transfer transistor G4 is controlled to the on state. When the accumulation time To has elapsed since the transfer transistor G3 was controlled to the off state, the transfer transistor G4 is controlled to the off state. The period during which the transfer transistor G4 is controlled to the on state is the accumulation drive time Tc. Then, the charge discharging transistor GD is controlled to the on state. In the discharge phase B, the charge discharge transistor GD is maintained in the ON state, and the transfer transistors G1 to G4 are maintained in the OFF state until the next unit accumulation period begins.

[0046] FIG. 4C is a schematic diagram showing the magnitude of the signal values ​​of pixel signals Q1 to Q4 corresponding to the amount of charge accumulated in each of the charge accumulation units CS1 to CS4 when the driving shown in FIG. 4B is performed. FIG. 4C shows examples of patterns P1 and P2. In pattern P1, the signal value of pixel signal Q1 exhibits excessive GD (charge drain) compared to the other pixel signals Q2 to Q4, resulting in pixel signal Q1 exhibiting a smaller value than the other pixel signals. In pattern P2, the signal value of pixel signal Q1 exhibits insufficient GD (charge drain) compared to the other pixel signals Q2 to Q4, resulting in pixel signal Q1 exhibiting a larger value than the other pixel signals. Note that this is based on the assumption that the amount of light incident on pixel 321 does not change (is constant) at the timing when charge is accumulated in each of the charge accumulation units CS1 to CS4. As described above, there tends to be a difference in the amount of charge accumulated between the pixel signal Q1 and the other pixel signals Q2 to Q4. One factor behind this is the difference in driving conditions. As shown in FIG. 4B, in driving a unit accumulation period, the pixel 321 is often driven so that accumulation phase A is performed for a relatively short time and discharge phase B is performed for a relatively long time. For this reason, the charge accumulation unit CS1 starts accumulating charge when the discharge phase B of the previous unit accumulation period switches from a long state in which charge is discharged to a state in which charge is not discharged. Meanwhile, the other charge accumulation units start accumulating charge when the previous charge accumulation unit CS completes a short-term charge accumulation. Specifically, the charge accumulation unit CS2 starts accumulating charge when the previous charge accumulation unit CS1 completes a short-term charge accumulation. The charge accumulation unit CS3 starts accumulating charge when the previous charge accumulation unit CS2 completes a short-term charge accumulation. The charge storage unit CS4 starts accumulating charges when the short-term charge storage in the preceding charge storage unit CS3 is completed. This difference in driving conditions is one of the factors that causes the distance measurement accuracy to deteriorate. To address this issue, in this embodiment, the pixels are driven so that the drive conditions of the charge storage unit CS1, which stores charge first among the multiple charge storage units CS1 to CS4, and the drive conditions of the other charge storage units CS2 to CS4, which store charge second or later, are close to each other. A method for driving the pixel 321 of this embodiment will be described below with reference to Figs. 5 to 13. Figs. 5 to 7 are timing charts showing an example of driving the pixel 321 of this embodiment. Fig. 8 (Figs. 8A to 8C) is a diagram showing an example of the layout of the pixel 321 of this embodiment. Figs. 9 to 13 are timing charts showing an example of driving the pixel 321 of this embodiment.

[0047] The items "GD," "Fixed to 0," "G1" to "G4," and "LIGHT" in FIGS. 5 to 7 are the same as those in FIG. 4B, and therefore description thereof will be omitted.

[0048] Fig. 5 shows a driving example (first example) of the pixel 321 of this embodiment. As shown in Fig. 5, in this embodiment, the distance image pickup device 1 executes the adjustment phase X at timing TG1 in Fig. 4B, that is, at the timing of switching from the discharge phase B of the previously executed unit accumulation period to the unit accumulation period to be executed this time. The range image pickup device 1 sequentially executes a first drive KN1 and a second drive KN2 in the adjustment phase X. In the first drive KN1, the charge discharge unit (charge discharge transistor GD) is not caused to discharge charge, and charge is not stored in the charge storage unit CS. In the second drive KN2, charge is discharged via the charge discharge unit (charge discharge transistor GD). Here, the execution time Tg for executing the second drive KN2 is the same as the accumulation drive time Tc for executing the accumulation drive for accumulating charge in one charge accumulation section CS in the accumulation phase, that is, Tg=Tc. In this manner, in this embodiment, an adjustment phase X is provided in the driving of the pixel 321 during a unit accumulation period. This pulse-drives the charge discharging unit (charge discharging transistor GD) immediately before accumulating charge in the charge accumulation unit CS1, making it appear as if charge accumulation in the charge accumulation unit CS1 begins at the timing when short-term charge accumulation in the preceding charge accumulation unit is completed. This allows the driving conditions of the charge accumulation unit CS1 and the other charge accumulation units CS2 to CS4 that accumulate charge second or later to be closer to each other, making it possible to suppress deterioration in distance accuracy.

[0049] Fig. 6 shows a driving example (second example) of the pixel 321 of this embodiment. As shown in Fig. 6, the range image pickup device 1 may alternately perform the first driving KN1 and the second driving KN2 multiple times in the adjustment phase X.

[0050] Fig. 7 shows a driving example (third example) of the pixel 321 of this embodiment. As shown in Fig. 7, the range image pickup device 1 may perform driving in the adjustment phase X instead of continuing to maintain the charge discharging transistor GD in the on state in the discharge phase B, that is, may perform the first driving KN1 and the second driving KN2 alternately.

[0051] FIG. 8A shows a schematic layout of a pixel 321 in which the charge discharging transistor GD2 in FIG. 4A functions as a charge discharging section. In this example, the gate G of the charge drain transistor GD1 is connected to a control signal GD1_CL that controls the draining of charge. When the control signal GD1_CL is High (1), charge is drained, and when it is Low (0 (zero)), charge is not drained. The gate G of the charge discharging transistor GD2 is connected to a control signal GD2_CL that controls the discharging of charge. When the control signal GD2_CL is High (1), charge is discharged, and when it is Low (0 (zero)), charge is not discharged. By providing two charge discharging units (charge discharging transistors GD1 and GD2) in pixel 321, they can be used for different purposes. That is, one charge discharging unit (charge discharging transistor GD1) can be used to discharge charges for a long period of time, while the other charge discharging unit (charge discharging transistor GD2) can be used to match the driving conditions of charge storage unit CS1 and the other charge storage units CS2 to CS4. This makes it easy to match the driving conditions of the charge storage units CS while maintaining the function of discharging charges.

[0052] 8B is a schematic diagram illustrating a layout of the pixel 321 of FIG. 8A in which the buffer configurations of the control signals G1_CL to G4_CL and GD2_CL, indicated by the symbol GP, are aligned. By aligning the buffer configurations, for example by using the same power supply for the buffers, the waveforms (rising and falling waveforms) of the control signal for the charge discharging transistor GD2 can be made equivalent to the waveforms (rising and falling waveforms) of the control signals for the transfer transistors G1 to G4. This allows the electrical characteristics of the control waveform for the charge discharging unit (charge discharging transistor GD2), used to align the drive conditions of the charge storage unit CS, to be made closer to the electrical characteristics of the control waveform for the charge storage unit CS.

[0053] 8C shows a schematic layout of the photoelectric conversion element PD in the shape of a regular hexagon. In this way, the buffer configurations of the control signals G1_CL to G4_CL and GD2_CL indicated by the symbol GP are aligned, and the six gates G (the gates G of the two charge discharging transistors GD and the four transfer transistors G1 to G4) of the pixel 321 are symmetrically arranged with point symmetry about the center of the regular hexagon. This makes it possible to equalize the loads on each gate and to approximate the electrical characteristics of each control waveform.

[0054] 9 and 10 show a driving example using two charge discharging sections (charge discharging transistors GD1 and GD2) as shown in FIG.

[0055] 9 shows a driving example (fourth example) of the pixel 321 of this embodiment. In the adjustment phase X of the range image pickup device 1, the charge discharge section (charge discharge transistor GD1) used for discharging charge discharges charge, and the charge discharge section (charge discharge transistor GD2) used for aligning drive conditions sequentially performs the first drive KN1 and the second drive KN2.

[0056] 10 shows a driving example (fifth example) of the pixel 321 of this embodiment. The distance image pickup device 1 executes an adjustment phase X at the timing of switching from the discharge phase B of the previously executed unit accumulation period to the unit accumulation period to be executed this time, and also executes an adjustment phase X at the timing of ending the accumulation phase A.

[0057] 11 to 13 show driving examples in which one frame is made up of multiple subframes. Here, a case in which one frame has two subframes, a first subframe and a second subframe, will be described as an example. Also, Figs. 11 to 13 show driving examples in which one charge discharging unit is used, similar to the driving shown in Fig. 4A.

[0058] 11 to 13 show timing charts of elements corresponding to the items "GD.1," "G1.1" to "G4.1," "GD.2," "G1.2" to "G4.2," and "LIGHT." "GD.1" indicates the operation timing of the control signal GD_CL that controls the charge discharging transistor GD1 in the first subframe. "G1.1" to "G4.1" indicate the operation timing of the control signals G1_CL to G4_CL that control the transfer transistors G1 to G4 in the first subframe. "GD.2" indicates the operation timing of the control signal GD_CL that controls the charge discharging transistor GD1 in the second subframe. "G1.2" to "G4.2" indicate the operation timing of the control signals G1_CL to G4_CL that control the transfer transistors G1 to G4 in the second subframe. "LIGHT" indicates the irradiation timing of the light pulse PO. The irradiation timing of the light pulse PO is common to the first and second subframes.

[0059] 11 to 13, the distance image pickup device 1 first repeatedly executes driving of the first unit accumulation period a predetermined number of times (first accumulation count) as driving of the first sub-frame, and acquires pixel signals Q1 to Q4 as the driving results of the first sub-frame and stores them in memory. Next, the distance image pickup device 1 repeatedly executes driving of the second unit accumulation period a predetermined number of times (second accumulation count) as driving of the second sub-frame, and acquires pixel signals Q1 to Q4 as the driving results of the second sub-frame and stores them in memory. The distance image pickup device 1 then calculates the distance using the pixel signals Q1 to Q4 as the driving results of the first sub-frame stored in memory and the pixel signals Q1 to Q4 as the driving results of the second sub-frame.

[0060] Fig. 11 shows a driving example (sixth example) of the pixel 321 of this embodiment. In Fig. 11, the distance image pickup device 1 executes an adjustment phase X during a first unit accumulation period, and then executes a first accumulation phase A1, a first discharge phase B1, a second accumulation phase A2, and a second discharge phase B2 in that order. Furthermore, during the second unit accumulation period, the distance image pickup device 1 does not provide a charge accumulation section dedicated to external light, and executes an accumulation phase A at the same timing as the execution of the first discharge phase B1 during the first unit accumulation period, and then executes a discharge phase B.

[0061] During the first unit accumulation period, the charge accumulation unit CS1 is used as a charge accumulation unit dedicated to external light, accumulating only external light components. The reason why the first unit accumulation period includes a first discharge phase B1 is to delay the accumulation timing at which charges are accumulated in each of the charge accumulation units CS2 to CS4 relative to the irradiation timing of the light pulse PO compared to the driving shown in Fig. 5. By delaying the accumulation timing, the component of reflected light RL that arrives after being reflected by an object OB located at a relatively long distance is accumulated in one of the charge accumulation units CS2 to CS4. In the second unit accumulation period, the charge accumulation unit CS1 is used as a charge accumulation unit that accumulates the component of the reflected light RL that arrives after being reflected by the object OB at a short distance. As in the first unit accumulation period, each of the charge accumulation units CS2 to CS4 accumulates the component of the reflected light RL that arrives after being reflected by the object OB at a relatively long distance. Generally, the reflected light RL arriving after reflecting off a nearby subject OB has a large amount of light, while the reflected light RL arriving after reflecting off a distant subject OB has a small amount of light. By performing the driving shown in FIG. 11 , it is possible to reduce the number of times that the component of the reflected light RL arriving after reflecting off a nearby subject OB is accumulated, and increase the number of times that the component of the reflected light RL arriving after reflecting off a distant subject OB is accumulated. By reducing the number of times that the component of the reflected light RL arriving after reflecting off a nearby subject OB is accumulated, it is possible to prevent the amount of charge accumulated in the charge accumulation unit CS from becoming saturated, making it impossible to accurately calculate distance. By increasing the number of times that the component of the reflected light RL arriving after reflecting off a distant subject OB is accumulated, it is possible to accumulate an amount of charge in the charge accumulation unit CS that enables accurate distance calculation.

[0062] Specifically, the distance image pickup device 1 sequentially executes a first drive KN1 and a second drive KN2 in the adjustment phase X of the first unit accumulation period. In the first accumulation phase A1, accumulation drive is executed to accumulate charge in the charge accumulation unit CS1 for an accumulation drive time Tc, thereby accumulating charge of external light components in the charge accumulation unit CS. In the first discharge phase B1, the distance image pickup device 1 discharges charge via the charge accumulation unit (charge discharge transistor GD). In the second accumulation phase A2, the distance image pickup device 1 executes accumulation drive to accumulate charge in each of the charge accumulation units CS2 to CS4 in turn for an accumulation drive time Tc. In the second discharge phase B2, the distance image pickup device 1 discharges charge via the charge accumulation unit (charge discharge transistor GD). Furthermore, the distance image pickup device 1 sequentially executes the first drive KN1 and the second drive KN2 in the adjustment phase X of the second unit accumulation period. In the accumulation phase A, the distance image pickup device 1 executes accumulation drive to accumulate charge in each of the charge accumulation units CS1 to CS4 in turn for an accumulation drive time Tc. In the discharge phase B, the distance image pickup device 1 discharges charge via the charge accumulation unit (charge discharge transistor GD).

[0063] In this way, the distance image pickup device 1 executes the adjustment phase X at the timing of switching from the discharge phase B of the previously executed unit accumulation period to the unit accumulation period to be executed this time, in each of the multiple subframes provided in one frame. By providing the adjustment phase X before accumulating charge in the charge accumulation unit CS1 in the first accumulation phase A1 of the first unit accumulation period and before accumulating charge in the charge accumulation unit CS1 in the accumulation phase A of the second unit accumulation period, it is possible to bring the driving conditions closer to those of the other charge accumulation units CS2 to CS4.

[0064] 12 shows a driving example (seventh example) of the pixel 321 of this embodiment. The first accumulation phase A1, first discharge phase B1, second accumulation phase A2, and second discharge phase B2 in the first unit accumulation period, and the accumulation phase A and discharge phase B in the second unit accumulation period shown in FIG. 12 are the same as those in FIG. 12, the distance image capturing device 1 may start executing the adjustment phase X of the second unit accumulation period at the same timing as the adjustment phase X of the first unit accumulation period, and may execute the adjustment phase X of the second unit accumulation period for a longer period than the adjustment phase X of the first unit accumulation period. In this case, the distance image capturing device 1 alternately executes the first drive KN1 and the second drive KN2 multiple times in the adjustment phase X of the second unit accumulation period.

[0065] 12, the adjustment phase X of the first unit accumulation period starts at timing TG1. The first accumulation phase A1 in the first unit accumulation period starts at timing TG2. The accumulation phase A in the second unit accumulation period starts at timing TG3. Timing TG2 arrives earlier than timing TG3. If the elapsed time from timing TG1 to timing TG3 (i.e., the time to execute adjustment phase X in the second unit accumulation period) is greater than the time to execute the first drive KN1 and the second drive KN2 (once each), the distance image capturing device 1 may execute the first drive KN1 and the second drive KN2 alternately multiple times in the adjustment phase X of the second unit accumulation period.

[0066] Fig. 13 shows a driving example (eighth example) of the pixel 321 of this embodiment. In the driving example of Fig. 13, the component of the reflected light RL that arrives after being reflected by the object OB, which is located at a greater distance than in the driving shown in Figs. 11 and 12, is accumulated in the pixel 321. Specifically, in the first unit accumulation period, a range shift period sft is provided between the irradiation timing and the accumulation timing at which charge is accumulated in the charge accumulation unit CS2. In the second unit accumulation period, an interlocking period tm is provided between the irradiation timing and the accumulation timing at which charge is accumulated in the charge accumulation unit CS1, in conjunction with the driving of the first unit accumulation section. When such a range shift period sft is provided, the range image pickup device 1 may alternately perform the first drive KN1 and the second drive KN2 multiple times during the range shift period sft.

[0067] Specifically, in the example of FIG. 13, charge accumulation in the charge accumulation unit CS1 in the first unit accumulation period ends at timing TG4, and charge accumulation in the next charge accumulation unit CS2 starts at timing TG5. If the elapsed time from timing TG4 to timing TG5 (i.e., the time to execute adjustment phase X2 in the first unit accumulation period) is greater than the time to execute the first drive KN1 and the second drive KN2 (once each), the distance image capturing device 1 may execute the first drive KN1 and the second drive KN2 alternately multiple times in the adjustment phase X of the second unit accumulation period. Note that, when a range shift period sft is provided in driving with a frame cycle that does not include sub-frames, the distance image pickup device 1 may execute the adjustment phase X during that range shift period. For example, assume that the range shift period sft is provided between timings TG4 and TG5 in the accumulation phase of a unit accumulation period in a frame cycle. In this case, the distance image pickup device 1 ends charge accumulation in the charge accumulation unit CS1 at timing TG4 and starts charge accumulation in the next charge accumulation unit CS2 at timing TG5 during the accumulation phase of the unit accumulation period. Because the elapsed time from timing TG4 to timing TG5 is longer than the time required to perform the first drive KN1 and the second drive KN2 once each, the distance image pickup device 1 alternately executes the first drive KN1 and the second drive KN2 multiple times during the elapsed time.

[0068] As described above, the distance image capture device 1 of this 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 a distance image sensor 32 (pixel circuit) in which a plurality of pixels 321, each having a photoelectric conversion element PD and three or more charge accumulation units CS, are arranged in a two-dimensional matrix, and a pixel drive circuit 322. The photoelectric conversion element PD generates electric charge in response to the incident light. The charge accumulation units CS accumulate the electric charge. The pixel drive circuit 322 distributes and accumulates the electric charge in each charge accumulation unit CS at an accumulation timing synchronized with the irradiation timing of the light pulse PO according to a frame period. The distance image processing unit 4 calculates the distance to the object OB based on the amount of electric charge accumulated in each charge accumulation unit CS. The distance image capture device 1 executes driving for a unit accumulation period a number of times during a frame period. The range image pickup device 1 executes an accumulation phase A and a discharge phase B in a unit accumulation period, and executes an adjustment phase X at the timing of switching from the discharge phase B of the previously executed unit accumulation period to the unit accumulation period to be executed this time. In the accumulation phase A, charges are sequentially accumulated in the charge accumulation unit CS at accumulation timing synchronized with the irradiation timing. In the discharge phase B, charges are discharged via the charge discharge unit. In the adjustment phase X, the range image pickup device 1 executes a first drive KN1 and a second drive KN2 in sequence. In the first drive KN1, charges are not discharged from the charge discharge unit and charges are not accumulated in the charge accumulation unit. In the second drive KN2, charges are discharged via the charge discharge unit. The time Tg for executing the second drive KN2 is the same as the accumulation drive time Tc for executing accumulation drive to accumulate charges in one charge accumulation unit CS in the accumulation phase A. As a result, in the distance image capturing device 1 of the embodiment, the pixels can be driven so as to mitigate the difference in driving conditions between the first charge storage section, which is the first of the multiple charge storage sections to store charge, and the other charge storage sections, which store charge second or later.

[0069] 6, in the range image capturing device 1 of the embodiment, the first drive KN1 and the second drive KN2 may be executed multiple times in the adjustment phase X. This makes it possible to achieve the same effects as those described above.

[0070] 7, the distance image pickup device 1 of the embodiment may be configured to alternately execute the first drive KN1 and the second drive KN2 in the adjustment phase X in the discharge phase B. This allows the distance image pickup device 1 of the embodiment to achieve the same effects as those described above.

[0071] Furthermore, in the range image pickup device 1 of the embodiment, the charge discharging section is made up of two parts: a first charge discharging section (charge discharging transistor GD1) and a second charge discharging section (charge discharging transistor GD2). As shown in FIGS. 9 and 10, in the range image pickup device 1, in adjustment phase X, the first charge discharging section (charge discharging transistor GD1) may discharge charge, and the second charge discharging section (charge discharging transistor GD2) may sequentially perform first driving KN1 and second driving KN2. This makes it easy to align the driving conditions of the charge accumulation section CS while maintaining the function of discharging charge.

[0072] 10, the distance image pickup device 1 of the embodiment may be configured to execute the adjustment phase X at the timing when the accumulation phase A ends, and then execute the discharge phase B. This allows all of the drive conditions of the charge accumulation units CS1 to CS4 to be brought closer together.

[0073] 11 to 13, the distance image pickup device 1 of the embodiment may be configured to provide a plurality of subframes in a frame cycle, and drive the pixels 321 so that the accumulation timing relative to the irradiation timing differs in each of the plurality of subframes. The distance image pickup device 1 executes the adjustment phase X in each of the plurality of subframes at the timing of switching from the discharge phase B of the previously executed unit accumulation period to the unit accumulation period to be executed this time. This allows the distance image pickup device 1 of the embodiment to bring the drive conditions of the charge accumulation unit CS1 closer to the drive conditions of the other charge accumulation units CS2 to CS4 in driving the subframes.

[0074] 11 to 13, when a frame includes two subframes, the distance imaging device 1 of the embodiment may execute the adjustment phase X at the same timing TG1 (first timing) relative to the irradiation timing of the light pulse PO in the first and second subframes. The distance imaging device 1 executes the adjustment phase X at timing TG1 in the first subframe, executes the first accumulation phase A1 at timing TG2 (second timing), and executes the accumulation phase at timing TG3 (third timing) in the second subframe. Timing TG2 arrives earlier than timing TG3. The distance imaging device 1 starts executing the adjustment phase X at timing TG1 in the second unit accumulation period of the second subframe, and if the elapsed time from timing TG2 to timing TG3 is longer than the time required to execute each of the first drive KN1 and the second drive TN2 (once each), executes the first drive KN1 and the second drive KN2 alternately during that elapsed time. As a result, in the range image pickup device 1 of the embodiment, the drive conditions of the charge accumulation unit CS1 can be made closer to the drive conditions of the other charge accumulation units CS2 to CS4 in drive in a frame cycle including sub-frames.

[0075] Furthermore, in the range image pickup device 1 of the embodiment, when a range shift period sft is provided, as shown in FIG. 13, an adjustment phase X may be executed during the range shift period sft instead of the discharge phase B. In the storage phase A, the range image pickup device 1 ends charge storage in the charge storage unit CS1 at timing TG4 (fourth timing), and starts charge storage in the charge storage unit CS2, which stores charge next to the charge storage unit CS1, at timing TG5 (fifth timing). The time elapsed from timing TG4 to timing TG5 is longer than the time required to execute each of the first drive KN1 and the second drive KN2. The range image pickup device 1 alternately executes the first drive KN1 and the second drive KN2 during this elapsed time. As a result, in the range image pickup device 1 of the embodiment, the drive conditions of the charge storage units CS1 to CS4 can be made closer to each other during driving including the range shift period.

[0076] The range image capture device 1 and range image processing unit 4 in the above-described embodiment may be implemented in whole or in part by a computer. In this case, a program for implementing these functions may be recorded on a computer-readable recording medium and then 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 devices 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 devices that store programs for a fixed period of time, such as volatile memory within a computer system acting as a server or client. The program may also be designed to implement some of the above-described functions, or may be capable of implementing 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.

[0077] 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. [Explanation of symbols]

[0078] 1...Distance image capturing device 2...Light source section 3...Light receiving section 32...Distance image sensor 321...pixels 322...Pixel driving circuit 4...Distance image processing section 41...Timing control section 42...Distance calculation section CS…Charge storage section PO...light pulse RL…Reflected light

Claims

1. a light source unit that irradiates a subject with light pulses; a range image sensor in which a plurality of pixels are arranged in a two-dimensional matrix, each pixel having a photoelectric conversion element that generates an electric charge in response to incident light, a charge discharging section that discharges the electric charge generated by the photoelectric conversion element, and a plurality of charge accumulation sections that accumulate the electric charge generated by the photoelectric conversion element; and a pixel drive circuit that distributes and accumulates electric charge in each of the charge accumulation sections at an accumulation timing synchronized with an irradiation timing at which the light pulse is irradiated in a frame period; a distance image processing unit that calculates a distance to the subject based on the amount of charge accumulated in each of the charge accumulation units; Equipped with The distance image processing unit Executing driving of a unit accumulation period a number of times in the frame period; a storage phase for storing charges in the charge storage unit in sequence at the storage timing during the unit storage period and a discharge phase for discharging charges via the charge discharge unit are executed, and an adjustment phase is executed at a timing when the discharge phase of the previously executed unit storage period is switched to the unit storage period to be executed this time; In the adjustment phase, a first drive is sequentially performed in which the charge discharging unit does not discharge charge and the charge accumulating unit does not accumulate charge, and a second drive is performed in which charge is discharged via the charge discharging unit; the pixel is provided with a plurality of the charge storage units sharing a common power supply, a first discharge unit which is at least one of the charge discharge units not sharing a power supply with the plurality of the charge storage units, and a second discharge unit which is at least one of the charge discharge units sharing a power supply with the plurality of the charge storage units; The distance image processing unit The first discharge unit is excluded from the first driving and the second driving in the adjustment phase; the second discharge unit is a target of the first driving and the second driving in the adjustment phase; Range imaging device.

2. In the pixel, the photoelectric conversion element is formed in a hexagonal shape in a plan view, the four charge accumulation units are arranged at any vertices of the photoelectric conversion element so as to be symmetrical with respect to an axis passing through the center of the photoelectric conversion element; two of the charge discharge portions are disposed at vertices other than the vertex at which the charge accumulation portion is provided; 2. The distance imaging device according to claim 1.

3. the distance image processing unit controls a discharge time for discharging electric charges and a storage time for storing electric charges in the charge storage unit in the second driving of the adjustment phase to be the same time.

2. The distance imaging device according to claim 1.

4. a light receiving unit having a light source unit that irradiates a subject with light pulses; a range image sensor in which a plurality of pixels are arranged in a two-dimensional matrix, the pixels each having a photoelectric conversion element that generates an electric charge in response to incident light, a charge discharge unit that discharges the electric charge generated by the photoelectric conversion element, and a plurality of charge accumulation units that accumulate the electric charge generated by the photoelectric conversion element; a pixel drive circuit that distributes and accumulates electric charge in each of the charge accumulation units at an accumulation timing synchronized with an irradiation timing of the light pulse irradiation according to a frame period; and a range image processing unit that calculates a distance to the subject based on the amount of electric charge accumulated in each of the charge accumulation units, The distance image processing unit Executing driving of a unit accumulation period a number of times in the frame period; a storage phase for storing charges in the charge storage unit in sequence at the storage timing during the unit storage period and a discharge phase for discharging charges via the charge discharge unit are executed, and an adjustment phase is executed at a timing when the discharge phase of the previously executed unit storage period is switched to the unit storage period to be executed this time; In the adjustment phase, a first drive is sequentially performed in which the charge discharging unit does not discharge charge and the charge accumulating unit does not accumulate charge, and a second drive is performed in which charge is discharged via the charge discharging unit; the pixel is provided with a plurality of the charge storage units sharing a common power supply, a first discharge unit which is at least one of the charge discharge units not sharing a power supply with the plurality of the charge storage units, and a second discharge unit which is at least one of the charge discharge units sharing a power supply with the plurality of the charge storage units; The distance image processing unit The first discharge unit is excluded from the first driving and the second driving in the adjustment phase; the second discharge unit is a target of the first driving and the second driving in the adjustment phase; Range imaging method.

Images