Distance image imaging element and distance image imaging apparatus

Abstract

To secure uniformity of pixel output characteristics and to improve accuracy of distance measurement.SOLUTION: The distance image sensor includes a pixel array in which a plurality of pixels each including a photoelectric conversion element and N charge accumulation units are arranged, and a pixel drive circuit that drives the pixels to distribute and accumulate charges in the charge accumulation units (N≥2), the pixels each including the N transfer transistors that transfer charges from the photoelectric conversion element to the N charge accumulation units, the N reset transistors that reset the charge accumulation units, and the N control transistors connected between the reset transistors and the power supply line. In the pixel, a control terminal of at least one of the N control transistors is connected to a control line capable of controlling an ON state of the control transistor, and remaining control terminals other than the at least one control transistor are connected to fix the control transistor to an OFF state.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Time-of-Flight (hereinafter referred to as "TOF") distance imaging devices have been realized that utilize the known speed of light to measure the distance between a measuring device and an object based on the time of flight of light in space (measurement space) (see, for example, Patent Document 1). Imaging devices such as distance imaging devices capture images using a distance imaging element that includes a photoelectric conversion element such as a photodiode. Known TOF distance imaging devices include a photoelectric conversion element that converts the amount of incident light into electric charges, and a distance imaging element that distributes and accumulates the electric charges converted by the photoelectric conversion element in multiple charge accumulation units. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4235729 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, there are cases where the pixels of a distance image sensor are added together, and in such cases, it is necessary to add a control transistor to add the charges of each pixel and erase the added charges. With a conventional distance image sensor, for example, if you want to add (2 x 2) pixels, you add one control transistor for every four pixels, and if you want to add (4 x 4) pixels, you add one control transistor for every 16 pixels. In other words, with a conventional distance image sensor, if you want to add (K x K) pixels, you need to add one control transistor for every (K x K) pixels.

[0005] However, in conventional distance imaging devices, when the addition of multiple pixels as described above is viewed as a single pixel, some pixels have a control transistor and some do not, which causes the pixel symmetry to be disrupted and the uniformity of the pixel output characteristics to be lost.As a result, in conventional distance imaging devices, the uniformity of the pixel output characteristics is disrupted, which can reduce the accuracy of distance measurement.

[0006] The present invention has been made to solve the above problems, and its object is to provide a distance image pickup element and a distance image pickup device that can uniformize pixel output characteristics and improve the accuracy of distance measurement. [Means for solving the problem]

[0007] In order to solve the above problem, one aspect of the present invention is a distance imaging element comprising: a pixel array in which a plurality of pixels are arranged, each pixel having a photoelectric conversion element that generates a charge in response to incident light and N charge accumulation sections that accumulate the charge; and a pixel drive circuit that drives the pixels to allocate and accumulate the charge in each of the charge accumulation sections (where N is an integer greater than or equal to 2), wherein the pixels comprise: N transfer transistors that transfer the charge from the photoelectric conversion element to each of the N charge accumulation sections; N reset transistors corresponding to each of the N charge accumulation sections, each reset transistor resetting the charge accumulation section to a predetermined reset potential supplied from a power supply line; and N control transistors corresponding to the N reset transistors, each connected between the reset transistor and the power supply line; and in the pixel, at least one control terminal of the N control transistors is connected to a control wiring that can control the conduction state of the control transistor, and the remaining control terminals of the N control transistors other than the at least one are connected to fix the control transistor to a non-conductive state.

[0008] In addition, one aspect of the present invention is that, in the above-mentioned distance image pickup element, the pixel array has K types of pixels (where K is an integer less than or equal to N), and each of the K types of pixels has a control transistor, among the N control transistors, that is connected to the control wiring, in a different position.

[0009] In addition, one aspect of the present invention is that, in the above-mentioned distance image pickup element, the K types of pixels may each be arranged in a row, and a unit pixel structure consisting of the K types x K number of pixels may be formed on a semiconductor substrate.

[0010] In one aspect of the present invention, in the above-described distance image pickup element, the pixel array may be formed by repeating the unit pixel structure.

[0011] In addition, one aspect of the present invention is that in the above-mentioned distance image pickup element, the pixel may include a source follower transistor that converts the charge into an electrical signal, a selection transistor that selects the reading of the electrical signal of the pixel, and a charge discharge transistor that discharges the charge from the photoelectric conversion element.

[0012] Another aspect of the present invention is a distance image capturing device that includes a light source unit that irradiates a subject with a light pulse, a light receiving unit that has the distance image capturing element described above, 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. [Effects of the Invention]

[0013] According to the present invention, pixel output characteristics can be made uniform, and the accuracy of distance measurement can be improved. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a block diagram showing an example of a distance imaging device according to an embodiment of the present invention; [Figure 2]FIG. 1 is a block diagram showing an example of a distance image pickup element according to an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram illustrating an example of a pixel layout in the present embodiment. [Figure 4] FIG. 1 is a first diagram illustrating an example of a pixel according to the present embodiment. [Figure 5] FIG. 2 is a second diagram illustrating an example of a pixel according to the present embodiment. [Figure 6] FIG. 10 is a third diagram illustrating an example of a pixel according to the present embodiment. [Figure 7] FIG. 4 is a fourth diagram showing an example of a pixel in this embodiment. [Figure 8] FIG. 2 is a diagram illustrating an example of a pixel array according to the present embodiment. [Figure 9] 10 is a timing chart showing an example of operation in a normal mode of the distance image pickup device according to the present embodiment. [Figure 10] 10 is a timing chart showing an example of the operation in a binning mode of the range image pickup element according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] A distance image pickup element and a distance image pickup device according to an embodiment of the present invention will be described below with reference to the drawings.

[0016] FIG. 1 is a block diagram showing an example of a range image capturing device 100 according to this embodiment. As shown in Fig. 1, the distance image pickup device 100 includes 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 measure the distance to using the distance image pickup device 100.

[0017] The light source section 2 irradiates a light pulse PO into a space to be photographed, in which a subject OB, the distance of which is to be measured by the distance image pickup device 100, is present, under the control of the distance image processor 4. The light source section 2 is, for example, a surface-emitting semiconductor laser module such as a vertical cavity surface-emitting laser (VCSEL). The light source section 2 also includes a light source device 21 and a diffuser plate 22.

[0018] 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 that are 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 measurement control unit 43.

[0019] 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.

[0020] The light receiving unit 3 receives reflected light RL of the light pulse PO reflected by an object OB, the distance of which is to be measured in the range image pickup device 100, 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 pickup element 1.

[0021] The lens 31 is an optical lens that guides the incident reflected light RL to the distance image pickup element 1. The lens 31 outputs the incident reflected light RL to the distance image pickup element 1 side, and causes the light to be received (incident) by the pixel array 11 provided in the light receiving region of the distance image pickup element 1.

[0022] The distance image pickup element 1 is an image pickup element used in the distance image pickup device 100. Here, the configuration of the distance image pickup device 1 will be described with reference to FIG. FIG. 2 is a block diagram showing an example of the distance image pickup device 1 according to this embodiment.

[0023] As shown in FIG. 2, the distance image pickup device 1 includes a pixel array 11 including a plurality of pixels 10 in a two-dimensional light receiving area, and a pixel drive circuit 12 that controls each of the pixels 10.

[0024] Each pixel 10 included in the pixel array 11 includes, for example, one photoelectric conversion element PD, a plurality of charge accumulation units CS corresponding to the one photoelectric conversion element PD, and components that distribute charges to the respective charge accumulation units CS. A detailed configuration of the pixel 10 according to this embodiment will be described later with reference to the drawings.

[0025] The pixel driving circuit 12 distributes and accumulates electric charges in each of the electric charge accumulation sections CS at a predetermined accumulation timing synchronized with the irradiation of the light pulse PO. Furthermore, the pixel driving circuit 12 switches the pixel area between a normal mode (single pixel) and a binning mode in which a plurality of pixels 10 are added together, depending on the imaging scene (measurement scene).

[0026] 1, distance image processor 4 controls distance image pickup device 100 and calculates the distance to subject OB. Based on the amount of charge accumulated in each charge accumulation unit CS, distance image processor 4 measures the distance to subject OB, which exists in the measurement space, as the measured distance. Further, distance image processing unit 4 includes timing control unit 41, distance calculation unit 42, and measurement control unit 43.

[0027] 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 the irradiation of the light pulse PO, a signal that distributes and accumulates the reflected light RL in multiple charge accumulation units CS, and a signal that controls the number of accumulations per frame. The number of accumulations is the number of times that the process of distributing and accumulating electric charge in the charge accumulation units CS is repeated, and is a predetermined number of distributions per frame period. The product of this number of accumulations and the time duration (accumulation time duration) for accumulating electric charge in each charge accumulation unit CS per process of distributing and accumulating electric charge is the exposure time.

[0028] The distance calculation unit 42 outputs distance information calculated based on the pixel signals output from the distance image pickup device 1. 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.

[0029] With this configuration, in the distance image capturing device 100, 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 (distance image) measuring the distance to the subject OB.

[0030] Next, the detailed configuration of the pixel 10 according to this embodiment will be described with reference to FIGS. FIG. 3 is a diagram showing an example of the layout of the pixel 10 in this embodiment.

[0031] As shown in FIG. 3, the pixel 10 in this embodiment includes, on a semiconductor substrate SB, one photoelectric conversion element PD, four transfer transistors G (G1 to G4), two charge discharge transistors GD (GD1, GD2), four reset transistors RT (RT1 to RT4), four capacitors CAP (CAP1 to CAP4), four source follower transistors SF (SF1 to SF4), four selection transistors SL (SL1 to SL4), and four control transistors RS (RS1 to RS4).

[0032] In FIG. 3, the horizontal axis in plan view is the X-direction axis, and the vertical axis is the Y-direction axis. The photoelectric conversion element PD is arranged in the center of the semiconductor substrate SB of the pixel 10, and two charge discharge transistors GD (GD1, GD2) are arranged on the left and right of the X-axis, and two transfer transistors G (G1, G3) and two transfer transistors G (G2, G4) are arranged above and below in the Y-axis direction.

[0033] The transfer transistor G1 is connected to a reset transistor RT1, the transfer transistor G2 is connected to a reset transistor RT2, the transfer transistor G3 is connected to a reset transistor RT3, and the transfer transistor G4 is connected to a reset transistor RT4.

[0034] The four capacitors CAP (CAP1 to CAP4) are arranged so as to be symmetrical with one another with respect to the X-axis center line CX and the Y-axis center line CY. In addition, a selection transistor SL1, a source follower transistor SF1, and a control transistor RS1 are arranged above the capacitor CAP1 and the reset transistor RT1.

[0035] In addition, a selection transistor SL2, a source follower transistor SF2, and a control transistor RS2 are arranged below the capacitor CAP2 and the reset transistor RT2.

[0036] In addition, a selection transistor SL3, a source follower transistor SF3, and a control transistor RS3 are arranged above the capacitor CAP3 and the reset transistor RT3.

[0037] In addition, a selection transistor SL4, a source follower transistor SF4, and a control transistor RS4 are arranged below the capacitor CAP4 and the reset transistor RT4.

[0038] The pixel 10 has four control transistors RS, which is the same number as the capacitors CAP that are the charge storage units CS described later, and the four control transistors RS (RS1 to RS4) are arranged so as to be symmetrical with respect to the X-axis center line CX and the Y-axis center line CY. As shown in FIG. 3, in the pixel 10, the components are arranged so as to be symmetrical with respect to the X-axis center line CX and the Y-axis center line CY.

[0039] 4 to 7 are diagrams showing an example of a pixel 10 in this embodiment. In order to drive in binning mode, the pixel 10 of this embodiment has four control transistors RS (RS1 to RS4), the same number as the number of charge storage sections CS (capacitors CAP), and there are four types of pixels 10 (pixels 10-A to 10-B) with different signal connections to the control terminals of the four control transistors RS (RS1 to RS4).

[0040] In the examples shown in FIGS. 3 to 7, an example will be described in which the number N (N is an integer of 2 or more) of charge storage sections CS (capacitors CAP) is 4 (N=4).

[0041] FIG. 4 shows an example of a pixel 10-A, which is a type A pixel (hereinafter, sometimes referred to as pixel A) in this embodiment. The example of the pixels 10 shown in FIGS. 4 to 7 will be described as an example of a case where (4×4) pixels 10 are binned.

[0042] As shown in FIG. 4, pixel 10-A includes one photoelectric conversion element PD, four transfer transistors G (G1 to G4), two charge discharge transistors GD (GD1, GD2), four reset transistors RT (RT1 to RT4), four capacitors CAP (CAP1 to CAP4), four source follower transistors SF (SF1 to SF4), four selection transistors SL (SL1 to SL4), and four control transistors RS (RS1 to RS4).

[0043] The photoelectric conversion element PD is a buried photodiode that photoelectrically converts incident light, generates charges corresponding to the incident light (incident light), and accumulates the generated charges. In this embodiment, the incident light is incident from the space to be measured. The photoelectric conversion element PD has an anode terminal connected to the ground power line and a cathode terminal connected to the source terminals of the transfer transistors G (G1 to G4).

[0044] In pixel 10-A (10), the photoelectric conversion element PD photoelectrically converts incident light to generate electric charges, which are then distributed to each of the four charge accumulation units CS (CS1 to CS4), and voltage signals corresponding to the amounts of the distributed electric charges are output to the output lines PIXOUT.

[0045] The pixel driving circuit 12 synchronizes with the irradiation of the light pulse PO at a frame period under the control of the measurement control unit 43, and redirects the charges generated in the photoelectric conversion element PD by supplying accumulation control signals TX (TX1 to TX4) to the transfer transistors G (G1, G2, G3, G4) at the respective timings, causing the charges to be accumulated in the charge accumulation units CS1, CS2, CS3, CS4 in that order.

[0046] Here, the charge storage unit CS is composed of a floating diffusion FD and a capacitor CAP. That is, the charge storage unit CS1 is composed of a floating diffusion FD1 and a capacitor CAP1, the charge storage unit CS2 is composed of a floating diffusion FD2 and a capacitor CAP2, the charge storage unit CS3 is composed of a floating diffusion FD3 and a capacitor CAP3, and the charge storage unit CS4 is composed of a floating diffusion FD4 and a capacitor CAP4.

[0047] The floating diffusions FD (FD1 to FD4) are wirings between the transfer transistors G (G1 to G4) and the source follower transistors SF (SF1 to SF4). The capacitors CAP (CAP1 to CAP4) are, for example, CMOS capacitors.

[0048] The transfer transistors G (G1 to G4) are turned on (ON) by the control signals TX (TZ1 to TX4), and accumulate the charges generated by the photoelectric conversion elements PD in the charge accumulation sections CS (CS1 to CS4) and transfer the charges to the source follower transistors SF (SF1 to SF4).

[0049] The source follower transistors SF (SF1 to SF4) are transistors that convert charges into electrical signals, and output electrical signals (voltages) according to the charges accumulated in the charge accumulation sections CS (CS1 to CS4) to the selection transistors SL (SL1 to SL4).

[0050] The selection transistors SL (SL1 to SL4) select the readout of the electrical signals of the pixels SG. The selection transistors SL (SL1 to SL4) are turned on (ON) by control signals SEL (SEL1 to SEL4) and output pixel values ​​(output signals) to the output lines PIXOUT.

[0051] The reset transistors RT (RT1 to RT4) correspond to the charge storage units CS (CS1 to CS4), respectively, and reset the charge storage units CS (CS1 to CS4) to a predetermined reset potential supplied from the power supply line VDD. The reset transistors RT (RT1 to RT4) are turned on (ON) by control signals RST (RST1 to RST4), and reset the charge storage units CS (CS1 to CS4) to the reset potential supplied from the power supply line VDD via the control transistors RS (RS1 to RS4) described later.

[0052] The control transistors RS (RS1 to RS4) correspond to the reset transistors RT (RT1 to RT4) and are connected between the reset transistors RT (RT1 to RT4) and a power supply line VDD. The wiring between the control transistors RS (RS1 to RS4) and the reset transistors RT (RT1 to RT4) functions as floating diffusions FDC (FDC1 to FDC4) that output the added charges in a binning mode in which a plurality of pixels 10 are added together.

[0053] The control terminal of at least one of the four control transistors RS (RS1 to RS4) (the control transistor RS1 in pixel A) is connected to a wiring (control wiring) of a control signal RTC1 that can control the on state of the control transistor RS. Furthermore, the control terminals of all the other transistors (other than the control transistor RS1 in pixel A) among the four control transistors RS (RS1 to RS4) are connected to a power supply line VSS so that the control transistor RS is fixed to the off state.

[0054] In pixel A (pixel 10-A), the floating diffusion FDC1 is turned on by the wiring (control wiring) of the control signal RTC1, and is reset to the reset potential supplied from the power supply line VDD.

[0055] The two charge drain transistors GD (GD1, GD2) are connected between the photoelectric conversion element PD and the power supply line VDD, and drain the charge from the photoelectric conversion element PD. The charge drain transistors GD (GD1, GD2) are turned on by a control signal RSTD, and discharge the charge generated in the photoelectric conversion element PD by flowing it to the power supply line VDD (erasing the charge).

[0056] The transfer transistors G (G1 to G4), charge discharging transistors GD (GD1, GD2), reset transistors RT (RT1 to RT4), source follower transistors SF (SF1 to SF4), selection transistors SL (SL1 to SL4), and control transistors RS (RS1 to RS4) are NMOS (N-channel Metal Oxide Semiconductor) transistors.

[0057] FIG. 5 also shows an example of a pixel 10-B, which is a type B pixel (hereinafter, sometimes referred to as pixel B) in this embodiment.

[0058] The pixel 10-B shown in FIG. 5 has the same basic configuration as the pixel 10-A described above, but differs in the connection of the control signals (control wiring) of the control transistors RS (RS1 to RS4). 5, the control terminal of at least one of the four control transistors RS (RS1 to RS4) (the control transistor RS2 in pixel B) is connected to a wiring (control wiring) for a control signal RTC2 that can control the on state of the control transistor RS. In addition, the control terminals of all the other transistors (other than the control transistor RS2 in pixel B) among the four control transistors RS (RS1 to RS4) are connected to a power supply line VSS so as to fix the control transistor RS in the off state.

[0059] In pixel B (pixel 10-B), the floating diffusion FDC2 is turned on by the wiring (control wiring) of the control signal RTC2, and is reset to the reset potential supplied from the power supply line VDD.

[0060] FIG. 6 also shows an example of a pixel 10-C, which is a type C pixel (hereinafter, sometimes referred to as pixel C) in this embodiment.

[0061] The pixel 10-C shown in FIG. 6 has the same basic configuration as the pixel 10-A described above, but differs in the connection of the control signals (control wiring) of the control transistors RS (RS1 to RS4). 6, the control terminal of at least one of the four control transistors RS (RS1 to RS4) (the control transistor RS3 in pixel C) is connected to a wiring (control wiring) for a control signal RTC3 that can control the on state of the control transistor RS. In addition, the control terminals of all the other transistors (other than the control transistor RS3 in pixel C) among the four control transistors RS (RS1 to RS4) are connected to a power supply line VSS so that the control transistor RS is fixed to the off state.

[0062] In pixel C (pixel 10-C), the floating diffusion FDC3 is turned on by the wiring (control wiring) of the control signal RTC3, and is reset to the reset potential supplied from the power supply line VDD.

[0063] FIG. 7 also shows an example of a pixel 10-D, which is a type D pixel (hereinafter, sometimes referred to as pixel D) in this embodiment.

[0064] The pixel 10-D shown in FIG. 7 has the same basic configuration as the pixel 10-A described above, but differs in the connection of the control signals (control wiring) of the control transistors RS (RS1 to RS4). 7, the control terminal of at least one of the four control transistors RS (RS1 to RS4) (the control transistor RS4 in pixel D) is connected to a wiring (control wiring) of a control signal RTC4 that can control the on state of the control transistor RS. In addition, the control terminals of all the other transistors (other than the control transistor RS3 in pixel D) among the four control transistors RS (RS1 to RS4) are connected to a power supply line VSS so as to fix the control transistor RS in the off state.

[0065] In pixel D (pixel 10-D), the floating diffusion FDC4 is turned on by the wiring (control wiring) of the control signal RTC4, and is reset to the reset potential supplied from the power supply line VDD.

[0066] In this way, each of the four types of pixels 10, pixel A to pixel D, has a different position of the control transistor RS connected to the wiring of the control signal RTC (RTC1 to RTC4) among the four (an example of N) control transistors RS (RS1 to RS4).

[0067] Next, the configuration of the pixel array 11 will be described with reference to FIG. FIG. 8 is a diagram showing an example of the pixel array 11 in this embodiment. As shown in FIG. 8(a), the pixel array 11 has four types of pixels 10 (an example of K types), namely, pixels A to D (where K is an integer equal to or smaller than N, which is the number of charge storage sections CS).

[0068] In the pixel array 11, four types of pixels 10 (pixels 10-A to 10-D) are arranged in a row (for example, in FIG. 8(a) a horizontal example), and a pixel unit GU1 (unit pixel structure) consisting of a 4 types x 4 matrix (4 x 4 matrix) is formed on the semiconductor substrate SB. The pixel array 11 is formed by repeating the pixel units GU1.

[0069] FIG. 8(b) shows an example of wiring in the pixel array 11 of FIG. 8(a). 8(b), wiring LN1 indicates the wiring for floating diffusion FDC1, wiring LN2 indicates the wiring for floating diffusion FDC2, wiring LN3 indicates the wiring for floating diffusion FDC3, and wiring LN4 indicates the wiring for floating diffusion FDC4.

[0070] The wirings LN1 to LN4 of the floating diffusions FDC (FDC1 to FDC4) are drawn out to upper layer wirings of the semiconductor substrate SB.

[0071] By arranging pixels 10-A to 10-D of the same type in a horizontal row, the wiring LN1 to wiring LN4 of the floating diffusions FDC (FDC1 to FDC4) can be wired in straight lines, as shown in Figure 8(b), and can be wired in the shortest possible way.

[0072] Next, the operation of the distance image pickup device 1 according to this embodiment will be described with reference to the drawings. FIG. 9 is a timing chart showing an example of the operation of the range image pickup device 1 according to this embodiment in the normal mode.

[0073] In Figure 9, the horizontal axis represents time, and the vertical axis represents, from top to bottom, the waveforms of control signals TX1 to TX4, control signal RTC, control signal RSTa, control signal SELa, control signal RSTb, control signal SELb, control signal RSTc, control signal SELc, control signal RSTd, and control signal SELd.

[0074] 9, the reset signal (control signal RST) sent to pixel A is referred to as the control signal RSTa, and the control signal SEL sent to pixel A is referred to as the control signal SELa. Also, the reset signal (control signal RST) sent to pixel B is referred to as the control signal RSTb, and the control signal SEL sent to pixel B is referred to as the control signal SELb.

[0075] Similarly, the reset signal (control signal RST) sent to pixel C is referred to as the control signal RSTc, and the control signal SEL sent to pixel C is referred to as the control signal SELc. The reset signal (control signal RST) sent to pixel D is referred to as the control signal RSTd, and the control signal SEL sent to pixel D is referred to as the control signal SELd.

[0076] First, in the normal mode shown in FIG. 9, the pixel drive circuit 12 fixes the control signal RTC to an H (high) state, and fixes the control transistors RS (RS1 to RS4) to an on state.

[0077] Also, as shown in FIG. 9, during the period until time T1, the pixel driving circuit 12 turns on the transfer transistors G (G1 to G4) using control signals TX (TX1 to TX4), causing charges to accumulate in the charge accumulation units CS (CS1 to CS4).

[0078] Next, at time T1, the pixel drive circuit 12 sets the control signal SELa (SEL1 to SEL4) to the H state, causing the pixel value (output signal) of pixel A to be output to the output line PIXOUT. Next, at time T2, the pixel drive circuit 12 sets the control signal RSTa (RST1 to RST4) to the H state to reset the charge storage unit CS (CS1 to CS4) of the pixel A.

[0079] Next, at time T3, the pixel drive circuit 12 sets the control signal SELb (SEL1 to SEL4) to the H state, causing the pixel value (output signal) of pixel B to be output to the output line PIXOUT. Next, at time T4, the pixel drive circuit 12 sets the control signal RSTb (RST1 to RST4) to the H state to reset the charge storage unit CS (CS1 to CS4) of the pixel B.

[0080] Next, at time T5, the pixel drive circuit 12 sets the control signal SELc (SEL1 to SEL4) to the H state, causing the pixel value (output signal) of pixel C to be output to the output line PIXOUT. Next, at time T6, the pixel drive circuit 12 sets the control signal RSTc (RST1 to RST4) to the H state to reset the charge storage unit CS (CS1 to CS4) of the pixel C.

[0081] Next, at time T7, the pixel drive circuit 12 sets the control signal SELd (SEL1 to SEL4) to the H state, causing the pixel value (output signal) of pixel D to be output to the output line PIXOUT. Next, at time T8, the pixel drive circuit 12 sets the control signal RSTd (RST1 to RST4) to the H state to reset the charge storage unit CS (CS1 to CS4) of the pixel D. FIG. 10 is a timing chart showing an example of the operation of the distance image pickup device 1 according to this embodiment in a (4×4) pixel binning mode.

[0082] In Figure 10, the horizontal axis represents time, and the vertical axis represents, from top to bottom, the waveforms of control signals TX1 to TX4, control signal RTC, control signal RSTa, control signal SELa, control signal RSTb, control signal SELb, control signal RSTc, control signal SELc, control signal RSTd, and control signal SELd.

[0083] In FIG. 10, the control signals RSTa, SELa, RSTb, SELb, RSTc, SELc, RSTd, and SELd are the same as those in FIG. 9 described above.

[0084] 10, the pixel drive circuit 12 fixes the control signals RSTa, RSTb, RSTc, and RSTd to the H state, thereby fixing the reset transistors RT (RT1 to RT4) to the ON state. Also, the pixel drive circuit 12 fixes the control signals SELb, SELc, and SELd to the L (low) state, thereby fixing the selection transistors SL (SL1 to SL4) of pixels B to D to the OFF state.

[0085] Also, as shown in FIG. 10, during the period until time T11, the pixel driving circuit 12 turns on the transfer transistors G (G1 to G4) using control signals TX (TX1 to TX4), causing charges to accumulate in the charge accumulation units CS (CS1 to CS4).

[0086] Next, at time T11, the pixel drive circuit 12 sets the control signal SELa (SEL1 to SEL4) to the H state, causing pixel A to output a pixel value (output signal) corresponding to the charges summed by binning to the output line PIXOUT. Next, at time T12, the pixel drive circuit 12 sets the control signals RTC (RTC1 to RTC4) to the H state to reset the charge storage units CS (CS1 to CS4) of the (4×4) pixels.

[0087] As described above, the distance image pickup element 1 according to this embodiment comprises a pixel array 11 in which a plurality of pixels 10 are arranged, and a pixel drive circuit 12 that drives the pixels 10 to distribute and store charge in each charge storage section CS. Each pixel 10 has a photoelectric conversion element PD that generates charge according to incident light, and N charge storage sections CS that store the charge (where N is an integer of 2 or greater). Each pixel 10 comprises N transfer transistors G, N reset transistors RT, and a control transistor RS. The N transfer transistors G are Charges are transferred from the photoelectric conversion element PD to each of the N charge accumulation units CS. The N reset transistors RT correspond to each of the N charge accumulation units CS and reset the charge accumulation units CS to a predetermined reset potential supplied from a power supply line VDD. The N control transistors RS correspond to each of the N reset transistors RT and are connected between the reset transistors RT and the power supply line. In the pixel 10, at least one control terminal of the N control transistors RS is connected to a control line that can control the conduction state of the control transistor RS, and the remaining control terminals of the N control transistors RS other than at least one are connected to fix the control transistor RS to a non-conductive state.

[0088] As a result, by providing the same number of control transistors RS as the charge storage sections CS, the distance image pickup element 1 according to this embodiment does not have a mixture of pixels 10 with and without control transistors, and can maintain uniformity in pixel output characteristics. Therefore, the distance image pickup element 1 according to this embodiment can uniformize pixel output characteristics and improve the accuracy of distance measurement.

[0089] Furthermore, in this embodiment, the pixel array 11 has K types of pixels 10 (for example, four types of pixels A to D) (where K is an integer equal to or less than N), and each of the K types of pixels 10 has a different position of the control transistor RS connected to the wiring of the control signal RTC among the N control transistors RS.

[0090] As a result, the distance image pickup device 1 according to this embodiment can maintain uniformity of pixel output characteristics while realizing bling control by using K types of pixels 10 (for example, four types of pixels A to D).

[0091] In addition, in this embodiment, K types of pixels 10 are each arranged in a row (for example, horizontally), and a pixel unit GU1 (unit pixel structure) consisting of a matrix of K types x K (for example, (4 x 4) pixels) is formed on the semiconductor substrate SB.

[0092] As a result, the distance image pickup element 1 according to this embodiment can form the wiring of the floating diffusion FDCs (FDC1 to FDC4) in straight lines, enabling the wiring to be the shortest. Therefore, the distance image pickup element 1 according to this embodiment can reduce the parasitic capacitance in the wiring of the floating diffusion FDCs (FDC1 to FDC4) and can also reduce the influence of noise.

[0093] In this embodiment, the pixel array 11 is formed by repeating pixel units GU1. As a result, the distance image pickup element 1 according to this embodiment forms the pixel array 11 by repeating pixel units GU1 consisting of a matrix of K types x K (for example, (4 x 4) pixels), thereby enabling the number of pixels to be safely increased while maintaining uniformity in pixel output characteristics.

[0094] In addition, in this embodiment, the pixel 10 includes a source follower transistor SF that converts electric charges into an electric signal, a selection transistor SL that selects the readout of the electric signal of the pixel 10, and a charge discharging transistor GD that discharges electric charges from the photoelectric conversion element PD.

[0095] As a result, the distance image pickup element 1 according to this embodiment can properly read out the electrical signal of the pixel 10 using the source follower transistor SF and the selection transistor SL, and can properly initialize the photoelectric conversion element PD using the charge discharging transistor GD.

[0096] The distance image capturing device 100 according to this embodiment also includes a light source unit 2 that irradiates a light pulse PO onto the subject OB, a light receiving unit 3 that has the above-mentioned distance image capturing element 1, and a distance image processing unit 4 that controls the pixel driving circuit 12 to accumulate charge in each of the charge accumulation units CS and calculates the distance to the subject based on the amount of charge accumulated in each of the charge accumulation units CS.

[0097] As a result, the range image pickup device 100 according to this embodiment has the same effects as the range image pickup element 1 described above, making it possible to make pixel output characteristics uniform and improve the accuracy of distance measurement.

[0098] The present invention is not limited to the above-described embodiment, and can be modified within the scope of the present invention. For example, in the above embodiment, the photoelectric conversion element PD is an embedded photodiode that photoelectrically converts incident light to generate charges and accumulates the generated charges. However, the present invention is not limited to this, and 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.

[0099] Furthermore, in the above embodiment, an example was described in which the pixel 10 has four charge storage units CS, but this is not limited to this, and the pixel 10 may have any other number (N) of charge storage units CS as long as the number is two or more.

[0100] In the above embodiment, the pixel array 11 includes four types of pixels 10 as an example of K types of pixels 10, but this is not limiting. For example, when binning (2×2) pixels, two types of pixels 10 may be included. Furthermore, for example, when binning (3×3) pixels, three types of pixels 10 may be included.

[0101] Furthermore, in the above embodiment, the pixel array 11 has been described as an example in which pixels 10 of the same type are arranged side by side in a horizontal direction, but this is not limited to this, and for example, pixels 10 of the same type may be arranged side by side in a vertical direction.

[0102] In the above embodiment, the transfer transistors G (G1 to G4), the charge discharge transistors GD (GD1, GD2), the reset transistors RT (RT1 to RT4), the source follower transistors SF (SF1 to SF4), the selection transistors SL (SL1 to SL4), and the control transistors RS (RS1 to RS4) are NMOS transistors, but this is not limited to this and other transistors such as PMOS transistors may also be used.

[0103] Each component of the above-described distance imaging device 100 or pixel drive circuit 12 has an internal computer system. A program for realizing the functions of each component of the above-described distance imaging device 100 or pixel drive circuit 12 may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to perform processing in each component of the above-described distance imaging device 100 or pixel drive circuit 12. Here, "reading a program recorded on a recording medium into a computer system and executing it" includes installing the program into a computer system. The "computer system" here includes hardware such as an OS and peripheral devices.

[0104] Furthermore, a "computer system" may include multiple computer devices connected via a network, including communication lines such as the Internet, WAN, LAN, and dedicated lines. Furthermore, a "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. Thus, the recording medium storing the program may be a non-transitory recording medium such as a CD-ROM.

[0105] The recording medium also includes internal or external recording media accessible from a distribution server for distributing the program. The program may be divided into multiple parts, downloaded at different times, and then combined into components of the range image capture device 100 or pixel drive circuit 12. Alternatively, each divided program may be distributed by a different distribution server. Furthermore, the term "computer-readable recording medium" also includes a storage medium that stores a program for a certain period of time, such as volatile memory (RAM) within a computer system that serves as a server or client when a program is transmitted over a network. The program may also be a storage medium for implementing part of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that can realize the above-described functions in combination with a program already stored in the computer system.

[0106] Furthermore, some or all of the above-described functions may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each of the above-described functions may be individually implemented as a processor, or some or all of the functions may be integrated into a processor. Furthermore, the integrated circuit implementation method is not limited to LSI, and may be implemented using a dedicated circuit or a general-purpose processor. Furthermore, if an integrated circuit implementation technology that can replace LSI emerges due to advances in semiconductor technology, an integrated circuit based on that technology may be used. [Explanation of symbols]

[0107] 1...Distance image sensor 2...Light source section 3...Light receiving section 4...Distance image processing section 10...pixels 11...Pixel array 12...Pixel driving circuit 21...Light source device 22...Diffuser 31...Lens 41...Timing control section 42...Distance calculation section 43...Measurement control section 100...Distance image capturing device CS, CS1, CS2, CS3, CS4...Charge storage section FD, FD1, FD2, FD3, FD4, FDC1, FDC2, FDC3, FDC4...Floating diffusion G, G1, G2, G3, G4...Transfer transistors GD, GD1, GD2...charge discharge transistors OB…Subject PIXOUT...output line PD...photoelectric conversion element PO...light pulse RL…Reflected light RS, RS1, RS2, RS3, RS4...Control transistors RT, RT1, RT2, RT3, RT4...Reset transistors SF, SF1, SF2, SF3, SF4...Source follower transistors SL, SL1, SL2, SL3, SL4...Select transistors

Claims

1. A distance image pickup device comprising: a pixel array in which a plurality of pixels are arranged, each pixel having a photoelectric conversion element that generates an electric charge in response to incident light and N charge accumulation units that accumulate the electric charge; and a pixel drive circuit that drives the pixels to allocate and accumulate the electric charge in each of the charge accumulation units (where N is an integer of 2 or greater), The pixel is the N transfer transistors that transfer the charges from the photoelectric conversion element to the N charge accumulation units, respectively; reset transistors corresponding to the N charge storage units, respectively, which reset the charge storage units to a predetermined reset potential supplied from a power supply line; control transistors corresponding to the N reset transistors, the N control transistors being connected between the reset transistors and the power supply line; Equipped with In the pixel, at least one control terminal of the N control transistors is connected to a control wiring capable of controlling the conductive state of the control transistor, and the remaining control terminals of the N control transistors other than at least one are connected so as to fix the control transistor in a non-conductive state. Range imaging sensor.

2. the pixel array has K types of pixels (where K is an integer equal to or less than N); The K types of pixels each have a different position of the control transistor connected to the control wiring among the N control transistors. The distance image pickup device according to claim 1 .

3. The K type pixels are arranged in a row, The unit pixel structure configured with the matrix of K types x K pieces is formed on a semiconductor substrate. The distance image pickup device according to claim 2 .

4. The pixel array is formed by repeating the unit pixel structure. The distance image pickup device according to claim 3 .

5. The pixel is a source follower transistor that converts the charge into an electrical signal; a selection transistor for selecting a readout of the electrical signal of the pixel; a charge drain transistor that drains the charge from the photoelectric conversion element; The distance image pickup device according to claim 4 , comprising:

6. a light source unit that irradiates a subject with light pulses; a light receiving section having the distance image pickup element according to any one of claims 1 to 5; a distance image processing unit that controls the pixel drive circuit to accumulate charges 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; A distance image capturing device comprising:

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