Imaging device, imaging method, and computer program

Abstract

To provide an imaging device capable of suppressing power consumption when transferring charges collectively.SOLUTION: An imaging device has a plurality of pixels each having a photoelectric conversion unit, a charge accumulation unit that accumulates charge generated in the photoelectric conversion unit, a source follower unit that generates a voltage corresponding to the charge in the charge accumulation unit, a voltage holding unit that holds the voltage generated in the source follower unit, and a current amount control unit that controls the amount of current supplied to the source follower unit to be different depending on the amount of charge in the charge accumulation unit when the charges generated in the plurality of pixels are transferred collectively to the charge accumulation unit and the voltage corresponding to the charges is generated in the source follower unit and held in the voltage holding unit.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an imaging apparatus, an imaging method, a computer program, and the like. [Background technology]

[0002] For example, in CMOS image sensors, a so-called global electronic shutter has been proposed that matches the signal charge accumulation period (exposure period) between multiple pixels. The global electronic shutter has a storage section that stores the signal for each pixel, starts accumulation for all pixels at the same time, and transfers the charge to the storage section at the same time when accumulation ends.

[0003] The imaging device described in Patent Document 1 enables global electronic shutter operation by using multiple pixels that perform photoelectric conversion and charge-to-voltage conversion to output a voltage, and multiple voltage holding capacitors that hold the voltages output by each of these pixels. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-108066 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the imaging device of Patent Document 1 has a problem in that when signals are transferred collectively from the photoelectric conversion units to the voltage holding capacitors, the source follower current sources of all the pixels operate simultaneously, resulting in large peak power consumption.

[0006] Therefore, one object of the present invention is to provide an imaging device capable of suppressing power consumption when transferring charges in a batch. [Means for solving the problem]

[0007] An imaging device according to one aspect of the present invention comprises: A plurality of pixels each having a photoelectric conversion unit; a charge storage unit that stores charges generated in the photoelectric conversion unit; a source follower unit that generates a voltage corresponding to the charge in the charge storage unit; a voltage holding unit for holding the voltage generated by the source follower unit; and a current amount control unit that controls the amount of current supplied to the source follower unit to vary depending on the amount of charge in the charge accumulation unit when the charges generated in a plurality of the pixels are transferred collectively to the charge accumulation unit, and the voltage corresponding to the charges is generated in the source follower unit and held in the voltage holding unit. Effect of the Invention

[0008] According to the present invention, it is possible to provide an imaging device capable of suppressing power consumption when transferring electric charges in a batch. [Brief description of the drawings]

[0009] [Figure 1] 1 is a functional block diagram showing a configuration of an imaging device according to a first embodiment of the present invention. [Diagram 2] 2 is a block diagram showing an example of the configuration of a light receiving surface of a PD substrate 21 of the image sensor according to the first embodiment of the present invention. FIG. [Diagram 3] 2 is a block diagram showing an example of the configuration of a non-light receiving surface of a PD substrate 21 of the image sensor according to the first embodiment of the present invention. FIG. [Figure 4] 2 is a block diagram showing an example of the configuration of a laminated substrate 22 of the image sensor according to the first embodiment of the present invention. FIG. [Diagram 5] 2 is an equivalent circuit diagram showing a configuration example of a pixel and a readout circuit of an image sensor. [Figure 6] 4 is a timing chart showing an example of a method for driving the image sensor according to the first embodiment of the present invention. [Figure 7] 4 is a flowchart illustrating an example of an imaging method using the imaging device according to the first embodiment. [Figure 8]11 is a block diagram showing an example of the configuration of a non-light-receiving surface of a PD substrate of an image sensor according to a second embodiment of the present invention. FIG. [Figure 9] 10A to 10C are diagrams illustrating an example of the operation of the imaging device according to the second embodiment of the present invention. [Figure 10] 11A and 11B are block diagrams illustrating an example of the configuration of a PD of an image sensor according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram showing an example of the configuration of a non-light-receiving surface of a PD substrate of an image sensor according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment. In each drawing, the same members or elements are given the same reference numerals, and duplicated descriptions are omitted or simplified.

[0011] <Embodiment 1> Fig. 1 is a functional block diagram showing the configuration of an image capture device according to a first embodiment of the present invention. Note that some of the functional blocks shown in Fig. 1 are realized by causing a CPU or the like serving as a computer (not shown) included in the image capture device to execute a computer program stored in a memory serving as a storage medium (not shown).

[0012] However, a part or all of these may be realized by hardware, which may be a dedicated circuit (ASIC) or a processor (a reconfigurable processor, DSP), etc.

[0013] 1 may not be built in the same housing, and may be configured by separate devices connected to each other via signal paths. The imaging device of the embodiment described below is applicable to digital still cameras, digital video cameras, in-vehicle cameras, surveillance cameras, smartphones, etc.

[0014] 1 includes an optical system 1, an image sensor 2, a signal processing unit 3, a compression / decompression unit 4, a synchronization control unit 5, an operation unit 6, an image display unit 7, and an image recording unit 8. The optical system 1 includes a lens, a lens driving mechanism, a mechanical shutter mechanism, an aperture mechanism, etc., and forms an optical image of a subject on the light receiving surface of the image sensor 2. Of these, movable parts are driven based on control signals from the synchronization control unit 5.

[0015] The imaging element 2 is, for example, an XY address type CMOS (Complementary Metal Oxide Semiconductor) image sensor, and performs imaging operation and generates an imaging signal in response to a control signal from a synchronization control unit 5. Furthermore, the imaging signal is digitized by an AD conversion circuit included in the imaging element 2 and output to a signal processing unit 3 as an image signal.

[0016] The signal processing unit 3, under the control of the synchronization control unit 5, performs image processing such as noise correction and white balance processing on the digitized image signal input from the imaging element 2. In addition, the signal processing unit 3 generates control information for AF (Auto Focus), AE (Auto Exposure), etc.

[0017] The image signal and control information that have been subjected to image processing in the signal processing unit 3 are output to the synchronization control unit 5. The signal processing unit 3 also includes an amplifier that digitally amplifies an output signal output from a voltage holding unit (to be described later), and controls the amplification rate according to the ISO sensitivity setting, etc.

[0018] The compression / decompression unit 4 operates under the control of a synchronization control unit 5, and performs compression / encoding processing and decompression / decoding processing of image signals.

[0019] The synchronization control unit 5 includes, for example, a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), etc. as a computer. The CPU in the synchronization control unit 5 comprehensively controls each unit of the imaging device 100 by executing a computer program stored in the ROM or the like.

[0020] The operation unit 6 is composed of various operation members such as a shutter release button, and outputs a control signal according to an input operation by the user to the synchronization control unit 5. The input operation by the user includes, for example, setting the recording mode such as still image or video, exposure control (aperture, shutter speed, ISO sensitivity), and the like.

[0021] The image display unit 7 supplies an image signal to a display device such as an LCD (Liquid Crystal Display) to display an image. The image recording unit 8 is, for example, capable of receiving a portable recording medium and stores compressed and encoded image data files.

[0022] Fig. 2 is a block diagram showing an example of the configuration of the light receiving surface of the PD substrate 21 of the image sensor according to the first embodiment of the present invention. In Fig. 2, 10(pq) represents a PD (Photo Diode) located in the pth row and qth column. Fig. 2 shows an example of an arrangement of 4 rows x 4 columns of pixels, but in reality, for example, tens of millions of pixels or more are arranged two-dimensionally. Here, the PD functions as a photoelectric conversion unit that generates electric charges in response to incident light.

[0023] A color filter is arranged in front of each pixel. In the example of Fig. 2, color filters that transmit the wavelength bands of R (red), G (green), and B (blue) are arranged in a so-called Bayer array. Note that the color filters are not limited to this, and complementary colors may be used, or, for example, some of the G (green) may be replaced with clear (transparent).

[0024] Alternatively, a part of the color filter may be a filter that transmits a wavelength band of invisible light such as IR (infrared). That is, the color filter may transmit light of at least one wavelength band of red, green, blue, and invisible light.

[0025] 3 is a block diagram showing an example of the configuration of a non-light receiving surface of the PD substrate 21 of the image sensor according to the first embodiment of the present invention. On this non-light receiving surface, pixel circuits 11(pq) connected to the respective PDs 10(pq) are arranged two-dimensionally. In this embodiment, each pair of the PD 10(pq) and the pixel circuit 11(pq) is called a pixel. That is, each pixel includes the PD 10(pq) and the pixel circuit 11(pq) as a photoelectric conversion unit.

[0026] The voltage signal output from the pixel circuit 11(pq) can be further transferred to the laminated substrate 22 via an electrical contact CONT for each pixel. In addition, each pixel is connected to a vertical scanning circuit 20 of the laminated substrate 22, and a control signal is supplied from the vertical scanning circuit 20.

[0027] A signal line SL for supplying a control signal is provided for each row, and a common control signal is supplied to all pixels in the same row. The PD substrate 21 is, for example, an N-type silicon substrate, and the PD is an N-type semiconductor region that accumulates electrons from electron-hole pairs generated when light is received.

[0028] 4 is a block diagram showing an example of the configuration of the laminated substrate 22 of the image sensor according to the first embodiment of the present invention. The laminated substrate 22 has laminated circuits 12(pq) connected to the respective pixel circuits 11(pq) of the PD substrate 21 arranged two-dimensionally.

[0029] The stacked circuits 12(pq) and the pixel circuits 11(pq) are connected at the contacts CONT, and the voltage signals output from the pixel circuits 11(pq) can be transferred to the corresponding stacked circuits 12(pq) for all pixels at once and stored. The stored pixel signals are transmitted row by row by the vertical scanning circuit 20 for scanning the stacked circuits 12(pq) via the vertical output line VL(q0) to the AD conversion circuit AD(q0), where they are AD converted.

[0030] The AD converted digital signals are output in column sequence by the horizontal scanning circuit 30 via the horizontal output line HL to the output unit 50. The output unit 50 includes a known parallel-serial conversion means (hereinafter referred to as P / S conversion means), and sequentially converts the digital imaging signals transferred to the horizontal output line HL into a high-speed serial transmission format such as LVDS and outputs the converted signals. LVDS is an abbreviation for Low Voltage Differential Signaling.

[0031] The timing generating circuit 40 generates pulse signals for controlling the vertical scanning circuit 20, the AD conversion circuit AD(q0), and the horizontal scanning circuit 30, respectively.

[0032] In the imaging device 100 according to this embodiment, one vertical output line VL(q0) is provided for each column, and is shared by all pixels in the same column. Also, one AD conversion circuit AD(q0) is provided for each column. Note that, in order to increase the signal readout speed, two or more vertical output lines and AD conversion circuits may be provided for each column.

[0033] Here, the AD conversion circuit AD(q0) receives the pixel signal from the vertical output line VL(q0) and a reference signal RAMP whose signal level varies in proportion to time. Then, the AD conversion circuit AD(q0) performs AD conversion by comparing the pixel signal with the reference signal RAMP and counting the time until the signal levels of the pixel signal and the reference signal RAMP match.

[0034] 5 is an equivalent circuit diagram showing a configuration example of a pixel and a readout circuit of the image sensor according to the first embodiment of the present invention. In the PD 10(pq) and the pixel circuit 11(pq), the charge generated in the PD is transferred to a charge accumulation section (floating diffusion, hereinafter referred to as FD) via a transfer transistor TX. The FD has a floating capacitance and functions as a charge accumulation section that accumulates the charge generated in the photoelectric conversion section.

[0035] The first amplification transistor SF1 constitutes a source follower circuit consisting of FD and a first current source CCS1. The source follower circuit functions as a source follower section that generates a voltage corresponding to the charge stored in FD. The first reset transistor RES1 resets FD with a predetermined voltage VDD. The first selection transistor SEL1 is connected to the source of the first amplification transistor SF1.

[0036] The transfer transistor TX, first reset transistor RES1, and first selection transistor SEL1 can be controlled by pulse signals PTX, PRES1, and PSEL1 supplied from the vertical scanning circuit 20, respectively, to control charge transfer, reset, readout operations, etc. from the PD.

[0037] A current amount control unit 111 is connected to the first current source CCS1, and variably controls the amount of current flowing through the first amplification transistor SF1 of each pixel. That is, as described later, the amount of current supplied to the source follower unit is controlled to be different depending on the amount of accumulated charge in the FD.

[0038] In addition, the source follower section consisting of the first amplification transistor SF1, the first current source CCS1, and the current amount control section 111 may have a structure in which a part of the source follower section or the source follower section is shared by multiple pixels. For example, the first amplification transistors SF1 of two pixels may be connected to the first current source CCS1. This makes it possible to reduce the circuit area corresponding to each pixel and the number of operating circuits (power).

[0039] The source of the first selection transistor SEL1 is connected to the stacked circuit 12(pq) via a contact CONT. The stacked circuit 12(pq) includes two voltage holding capacitors CN and CS that store a voltage signal from the pixel circuit 11(pq). Here, the voltage holding capacitors CN and CS function as voltage holding units for holding the voltage generated in the source follower unit.

[0040] The voltage holding capacitance CN holds a noise voltage (hereinafter referred to as an N signal) immediately after the reset of the FD of the pixel circuit 11 (pq). Meanwhile, the voltage holding capacitance CS holds a signal voltage (hereinafter referred to as an S signal) of the FD corresponding to the signal charge generated by the incident light in the PD. Note that the larger the capacitance of the voltage holding capacitances CN and CS, the smaller the kTC noise accompanying the reset operation can be.

[0041] The decoupling transistor DX is a transistor for controlling the connection between the pixel circuit 11(pq) and the stack circuit 12(pq). The write transistors MWN and MWS are transistors for writing voltage signals to the voltage holding capacitors CN and CS, respectively.

[0042] The voltage holding capacitors CN and CS are connected to the gate of the second amplifying transistor SF2 via the write transistors MWN and MWS, respectively, and form a source follower circuit together with the second current source CCS2.

[0043] The second reset transistor RES2 resets the voltage holding capacitors CN and CS with a predetermined voltage VDD. The second selection transistor SEL2 is connected to the source of the second amplification transistor SF2 and selectively transmits a voltage signal to the vertical output line VL(q0).

[0044] The separation transistor DX, the write transistors MWN, MWS, the second reset transistor RES2, and the second select transistor SEL2 can be controlled by pulse signals PDX, PMWN, PMWS, PRES2, and PSEL2 supplied from a vertical scanning circuit 20. The vertical scanning circuit 20 controls the transfer of voltage signals, resetting, readout operations, and the like.

[0045] 6 is a timing chart showing an example of a method for driving the image sensor according to the first embodiment of the present invention. Each pulse signal is applied to the gate of each transistor, turning the transistor ON at Hi (High) and OFF at Lo (Low). The brackets in the pulse signal name correspond to the row number in the block diagram.

[0046] In FIG. 6, from time t600 to time t601, PRES1, PRES2, PMWS, and PMWN are set to Hi, and the charges of FD and the voltage holding capacitances CS and CN are reset.

[0047] At time t602, PSEL1, PDX, and PMWN are set to Hi, and at time t603, PMWN is set to Lo, thereby writing the voltage (N signal) after reset release of FD to the voltage holding capacitance CN of the stacked circuit 12 (pq).

[0048] At time t604, PTX is set to Hi, and at time t605, PTX is set to Lo, thereby transferring the charge stored in the PD to the FD.

[0049] With PSEL1 and PDX kept at Hi, PMWS is set to Hi at time t605 and to Lo at time t607, whereby the voltage of FD (S signal) that has changed according to the signal charge of PD is written to the voltage holding capacitance CS.

[0050] At time t608, PSEL1 and PDX are set to Lo, and the pixel circuit 11(pq) is separated from the multilayer circuit 12(pq). In this manner, the period from time t602 to time t608 represents a global electronic shutter operation in which a voltage signal based on the signal charge of each pixel is transferred to the multilayer circuit of the multilayer substrate simultaneously for all pixels.

[0051] By setting PSEL2(0) of the first row to Hi from time t609 to time t611, and setting PMWN(0) of the first row to Hi from time t609 to time t610, the N signal of the first row is transferred to the AD conversion circuit via the vertical output line VL(q0) and is AD converted.

[0052] From time t610 to time t611, PMWS(0) for the first row is set to Hi, so that the S signal for the first row is transferred to the AD conversion circuit via the vertical output line VL(q0) and AD converted. At time t612, the vertical scanning circuit 20 transitions to scanning the second row.

[0053] By setting PSEL2(1) in the second row to Hi from time t612 to time t614, and setting PMWN(1) in the second row to Hi from time t612 to time t613, the N signal in the second row is transferred to the AD conversion circuit via the vertical output line VL(q0) and is AD converted.

[0054] From time t613 to time t614, the PMWS(1) of the second row is set to Hi, so that the S signal of the second row is transferred to the AD conversion circuit via the vertical output line VL(q0) and AD converted. Similar operations are then repeated from the third row onwards, until the readout scanning of all pixels is completed.

[0055] As described above, the period from time t609 to time t614 represents the readout scanning period of the first row (laminated circuit 12(0q)) and the second row (laminated circuit 12(1q)) of the laminated substrate after the simultaneous transfer of all pixels.

[0056] Fig. 7 is a flowchart for explaining an example of an imaging method using the imaging device according to embodiment 1. Note that the operation of each step in the flowchart in Fig. 7 is performed sequentially by the CPU serving as a computer in the synchronization control unit 5 executing a computer program stored in a memory.

[0057] In step S701, shooting conditions such as the shooting mode, ISO sensitivity, exposure time, etc. are set based on instructions from the user or a predetermined automatic algorithm.

[0058] In step S702, if the ISO sensitivity is greater than the predetermined value A1, the process proceeds to step S703, otherwise the process proceeds to step S704. Here, the ISO sensitivity is set automatically or manually in response to the charge amount (signal level) of the charge storage unit that is assumed based on the subject brightness, etc.

[0059] In step S703, the amount of current supplied from the first current source CCS1 is set to the first current amount I1 by the current amount control unit 111. After the process of step S703, the process proceeds to step S707.

[0060] On the other hand, in step S704, the amount of current supplied from the first current source CCS1 is set to the second current amount I2 by the current amount control unit 111. Here, the first current amount I1 in step S703 is set to, for example, half the second current amount I2 in S704.

[0061] Thus, in steps S703 and S704, the current amount control unit 111 varies the amount of current supplied to the source follower unit according to the amplification factor of the amplifier means in the image sensor 2, which amplifies an analog signal corresponding to the charge generated in each pixel and which is set according to the ISO sensitivity, or according to the amplification factor of the amplifier means in the signal processing unit 3.

[0062] In step S705, the image sensor captures an image using the driving method described in the timing chart of Fig. 6. That is, the charges generated in multiple pixels are transferred to the charge storage section all at once, and a voltage corresponding to the charges is converted to a voltage by the source follower section and held in the voltage holding section.

[0063] The voltages held in the voltage holding units are then read out sequentially as pixel signals, and the pixel signals from which fixed pattern noise and the like have been removed are output by subtracting the voltage held in the voltage holding unit CN from the voltage held in the voltage holding unit CS.

[0064] Then, the signal processing unit 3 performs a predetermined image processing on the pixel signal, and the captured image data is displayed as a live view on the image display unit 7. Alternatively, the captured image data is output to and recorded in the image recording unit 8. The predetermined image processing includes signal level (amplification rate) adjustment using digital gain, noise reduction processing, white balance adjustment, shading correction processing, and the like.

[0065] In step S706, the signal amount (e.g., a value equivalent to brightness such as an average value) of a predetermined region of the imaging data acquired in step S705 is calculated. If this signal amount is greater than the predetermined value B1, the process proceeds to step S707, otherwise, the process proceeds to step S703. That is, the current amount control unit varies the amount of current supplied to the source follower unit according to the level of the output signal output from the voltage holding unit corresponding to the amount of accumulated charge in the charge accumulation unit.

[0066] In step S707, live view photography or still image photography is performed in the same manner as in step S705. That is, charges generated in a plurality of pixels are transferred collectively to the charge storage section, converted into a voltage corresponding to the amount of accumulated charge by the source follower section, and held in the voltage holding section. At this time, the current amount control section controls the amount of current supplied to the source follower section according to the amount of accumulated charge in the charge storage section so as to be different, such as a first current amount I1 or a second current amount I2.

[0067] The voltages held in the voltage holding units are then read out sequentially as pixel signals. At this time, the voltage held in the voltage holding units CN is subtracted from the voltage held in the voltage holding units CS to output pixel signals from which fixed pattern noise and the like has been removed. After shooting, predetermined image processing and output operations are performed, and the flow of Fig. 7 ends. Note that the flow of Fig. 7 is repeatedly executed, for example, at a predetermined cycle.

[0068] In this way, when it is determined in step S702 that the ISO sensitivity is set higher than the predetermined value, it is assumed that the subject is dark and the amount of charge stored in the PD and the voltage amplitude written to the voltage holding capacitance CS are small. Therefore, in this case, by reducing the amount of current supplied from the first current source CCS1 to the first current amount I1 when writing a voltage to the voltage holding capacitance CS in step S703, it is possible to suppress the power consumed during simultaneous transfer of all pixels.

[0069] Also in step S706, the brightness of the subject is detected based on the signal amount in a predetermined region, and if the signal amount is equal to or less than a predetermined value B1, it is determined that the subject is dark. Therefore, in this case, the amount of current supplied from the first current source CCS1 when writing a voltage to the voltage holding capacitance CS is reduced to the first current amount I1, thereby making it possible to suppress the power consumed during simultaneous transfer of all pixels.

[0070] In this embodiment, the ISO sensitivity and the output signal amount are compared with a predetermined value and a predetermined amount, respectively, and based on the result, when the subject is relatively dark, the amount of current supplied from the first current source CCS1 is reduced to the first current amount I1. However, it is also possible to determine only one of them and reduce the amount of current supplied from the first current source CCS1 to the first current amount I1.

[0071] Furthermore, when reducing the amount of current supplied from the first current source CCS1 when writing a voltage to the voltage holding capacitance CS, the write speed per unit time decreases, so the Hi period of the pulse signals PMWS and PMWN may be lengthened.

[0072] In the above example, when the illuminance (brightness of the subject) is low (when the ISO sensitivity is greater than a predetermined value A1 or when the signal amount in a predetermined area is equal to or less than a predetermined value B1), the amount of current supplied from the first current source CCS1 is reduced to the first current amount I1.

[0073] However, when the illuminance (brightness of the subject) decreases relatively (when the ISO sensitivity increases relatively or when the signal amount in a specified area decreases relatively, etc.), the amount of current supplied from the first current source CCS1 may be relatively decreased in multiple stages or continuously.

[0074] In addition, when the amount of current supplied from the first current source CCS1 to the voltage holding capacitance CS is relatively decreased (increased), the amount of current supplied from the first current source CCS1 to the voltage holding capacitance CN immediately before that is also relatively decreased (increased) in the same way.

[0075] As described above, according to the first embodiment, a global electronic shutter type imaging device 100 with reduced power consumption can be realized by variably controlling the amount of current supplied from the first current source CCS1 in accordance with the amount of accumulated charge corresponding to the amount of incident light (brightness of the subject).

[0076] <Embodiment 2> FIG. 8 is a block diagram showing an example of the configuration of the non-light receiving surface of the PD substrate of the image sensor according to the second embodiment of the present invention.

[0077] 8, signal lines SL1 and SL2 are provided in each row, SL1 is connected to an R pixel and a B pixel in the same row, and SL2 is connected to a G pixel in the same row. The current amounts of the first current sources of the R and B pixels and the first current source of the G pixel are controlled independently of each other.

[0078] 9 is a diagram for explaining an example of the operation of the imaging device according to the second embodiment of the present invention. In the second embodiment, for the R pixel and the B pixel selected by the signal line SL1, the current amount supplied from the first current source is set to the first current amount I1 by the current amount control unit 111.

[0079] On the other hand, for the G pixel selected by the signal line SL2, the amount of current supplied from the first current source is set to the second current amount I2 by the current amount control unit 111. Here, for example, the first current amount I1 is set to, for example, half of the second current amount I2.

[0080] For example, when imaging a gray subject, the amount of charge stored in the PD of the R pixel and the B pixel and the voltage amplitude written to the voltage holding capacitance CS are relatively small compared to the amount of charge stored in the PD of the G pixel and the voltage amplitude written to the voltage holding capacitance CS. Therefore, in the second embodiment, by reducing the amount of current supplied from the first current source when writing voltage to the voltage holding capacitance CS of the R pixel and the B pixel, it is possible to suppress power consumption during simultaneous transfer of all pixels.

[0081] In this embodiment, the R pixel and the B pixel are connected to the signal line SL1, and the G pixel is connected to the signal line SL2, but the B pixel may be connected to the signal line SL1, and the R pixel and the G pixel may be connected to the signal line SL2. In other words, when writing a voltage to the voltage holding capacitance CS of the B pixel, the amount of current supplied from the first current source may be relatively reduced.

[0082] When performing control as in the second embodiment, the color saturation may be detected, and if it is determined that the color saturation is equal to or lower than a predetermined value (i.e., the subject is substantially gray), the current amount for each color may be controlled as described above. If the color saturation is greater than the predetermined value, the current amount for each color may not be controlled as described above.

[0083] Alternatively, the color distribution in the image signal may be detected, and in an area where the saturation of a predetermined color is relatively high, the amount of current supplied from the first current source to pixels of that color may be relatively increased, or in an area where the saturation of a predetermined color is relatively high, the amount of current supplied from the first current source to pixels of colors other than that color may be relatively decreased.

[0084] Alternatively, the color temperature in the image signal may be detected, and if the color temperature is high, the amount of current supplied from the first current source to the B pixel may be relatively increased, or the amount of current supplied from the first current source to the R pixel may be relatively decreased.

[0085] Conversely, when the color temperature is low, for example, the amount of current supplied from the first current source to the B pixel may be relatively reduced, or the amount of current supplied from the first current source to the R pixel may be relatively increased.

[0086] It is also possible to specify this according to pixels that have the spectral characteristics of non-visible light, such as IR (infrared) filters. In this case, since the IR pixels have a larger signal amount than the G pixels, it is desirable to reduce the current amount in the visible range, such as the G pixels.

[0087] That is, for pixels in which the amount of photoelectric conversion is relatively large due to a filter with high light transmittance, the amount of current supplied from the first current source may be relatively increased when a voltage is written to the voltage holding capacitance CS.

[0088] In addition, when the amount of current supplied from the first current source that writes a voltage to the voltage holding capacitance CS is reduced, the writing speed per unit time decreases. Therefore, the voltage holding capacitance CS of the pixel having the spectral characteristic may be made small, or the capacitance may be made variable and controlled to be small.

[0089] In this way, since the amount of charge in the charge storage unit changes according to the spectral characteristics of the pixel, the amount of current supplied from the first current source is controlled according to the spectral characteristics of the pixel in the second embodiment. That is, by making the amount of current supplied from the first current source different for pixels having color filters of different colors, it is possible to realize a global electronic shutter type imaging device 100 with reduced power consumption.

[0090] <Embodiment 3> 10A and 10B are block diagrams showing an example of the configuration of a PD of an image sensor according to embodiment 3 of the present invention. Fig. 10A is a diagram showing an example in which one pixel is provided with a pair of photoelectric conversion units PD101 and PD102 having approximately the same size (sensitivity).

[0091] This structure is primarily used for image plane phase difference detection, and a common microlens for focus detection is disposed in front of PD101 and PD102. PD101 and PD102 are configured so that light enters from different exit pupils of the optical system.

[0092] In addition, the configuration for detecting phase difference on the imaging surface is not limited to a multi-pixel structure, and may be a structure in which multiple pixels in which light from one of two exit pupils incident on the photoelectric conversion unit is blocked by a light-shielding layer, and multiple pixels in which light from the other exit pupil is blocked by a light-shielding layer are arranged within the image sensor.

[0093] 10B is a diagram showing an example in which a pair of photoelectric conversion units PD101 and PD102 with different sizes (sensitivities) are provided in one pixel. This structure is mainly used for imaging aimed at a wide dynamic range. For example, the dynamic range is expanded by using a signal from a large photoelectric conversion unit for low brightness areas and a signal from a small photoelectric conversion unit for high brightness areas.

[0094] 10A and 10B, each pixel has multiple photoelectric conversion units. Here, a signal based on the photoelectric conversion of PD101 is designated as signal A, and a signal based on the photoelectric conversion of PD102 is designated as signal B. Also, a signal obtained by adding (mixing) the signals based on the photoelectric conversion of PD101 and PD102 is designated as signal A+B.

[0095] 10A, when the A signal or the B signal is read and a voltage is written to the voltage holding capacitance CS, the amount of current supplied from the first current source to the source follower section is relatively reduced to a first current amount, whereas when the A+B signal is read and a voltage is written to the voltage holding capacitance CS, the amount of current supplied from the first current source is set to a second current amount.

[0096] 10B, when the A signal is read and a voltage is written to the voltage holding capacitance CS, the amount of current supplied from the first current source to the source follower is relatively reduced to a first current amount, and when the B signal or the A+B signal is read and a voltage is written to the voltage holding capacitance CS, the amount of current supplied from the first current source is set to a second current amount.

[0097] That is, in the third embodiment, the amount of current supplied from the first current source to the source follower unit is made different between when the charges of a plurality of photoelectric conversion units are read out separately and when the charges are added and read out.

[0098] The first current amount I1 is set to, for example, half the second current amount I2. That is, the current amount control unit connected to the first current source is set to be different depending on the size (sensitivity) of the PD. Therefore, when the amount of charge stored in the PD and the voltage amplitude written to the voltage holding capacitance CS are small, the amount of current supplied from the first current source is reduced when writing a voltage to the voltage holding capacitance CS, thereby suppressing power consumption during simultaneous transfer of all pixels.

[0099] In this way, since the amount of charge in the charge storage unit changes depending on the size (sensitivity) of PD, in the third embodiment, the amount of current supplied from the first current source is made to differ when writing a voltage to the voltage holding capacitance CS depending on the size (sensitivity) of PD, thereby realizing a global electronic shutter type imaging device 100 with reduced power consumption.

[0100] <Embodiment 4> FIG. 11 is a block diagram showing an example of the configuration of a non-light-receiving surface of a PD substrate of an image sensor according to embodiment 4 of the present invention, and shows an example of the configuration for limiting (selecting) the pixels from which signals are read out, that is, for so-called thinning readout.

[0101] The thinning-out readout can be realized by always setting the first selection transistor SEL1 and the second selection transistor SEL2 or the transfer transistor TX in the row to Lo, etc. Also, thinning-out readout can be performed not only on rows but also on columns.

[0102] In the configuration of the fourth embodiment shown in FIG. 11, for example, in a given frame, it is possible to operate so that the first row (11(0q)) and the fourth row (11(3q)) are output, and the hatched second row (11(1q)) and the third row (11(2q)) are not output. This is called the first readout mode. On the other hand, as explained in the first to third embodiments, the configuration in which all rows are output for each frame is called the second readout mode.

[0103] In the configuration of embodiment 4 shown in FIG. 11, a signal line SL is provided for each row, and all pixels in the same row can be selected simultaneously, so that the current amount control unit 111 connected to the first current source CCS1 can be controlled for each row.

[0104] In the first read mode, the current amount control unit 111 connected to the row that does not output sets the current amount supplied from the first current source CCS1 to 0, that is, the power consumption of the row that does not output is reduced. The current amount control unit 111 connected to the row that does output is set to the second current amount I2. In the second read mode, the current amount control unit 111 is set to the first current amount I1. Here, the first current amount I1 is set to, for example, half the second current amount I2.

[0105] In the second readout mode, more pixels are transferred simultaneously for all pixels than in the first readout mode. At this time, the power consumed during the simultaneous transfer of all pixels can be reduced by reducing the amount of current supplied from the first current source to write a voltage to the voltage holding capacitance CS.

[0106] That is, in embodiment 4, the amount of current supplied from the first current source CCS1 is made different between a first readout mode in which signals from the multiple pixels are thinned out and read out, and a second readout mode in which signals from the multiple pixels are read out without thinning out the signals.

[0107] In this way, since the amount of charge in the charge storage section may change depending on the number of pixels to be driven, in the fourth embodiment, the amount of current supplied from the first current source to the voltage holding capacitor CS is controlled depending on the number of pixels to be driven, thereby realizing a global electronic shutter type imaging device 100 with reduced power consumption.

[0108] Although the present invention has been described in detail based on the preferred embodiment, the present invention is not limited to the above embodiment, and various modifications are possible based on the spirit of the present invention, and are not excluded from the scope of the present invention. The above embodiment includes the following combinations.

[0109] (Configuration 1) An imaging device comprising: a plurality of pixels each having a photoelectric conversion unit; a charge accumulation unit that accumulates charge generated in the photoelectric conversion unit; a source follower unit that generates a voltage corresponding to the charge in the charge accumulation unit; a voltage holding unit that holds the voltage generated in the source follower unit; and a current amount control unit that controls the amount of current supplied to the source follower unit to be different depending on the amount of charge in the charge accumulation unit when the charges generated in the plurality of pixels are transferred collectively to the charge accumulation unit, and the voltage corresponding to the charges is generated in the source follower unit and held in the voltage holding unit.

[0110] (Configuration 2) The imaging device according to configuration 1, wherein the current amount control section is shared by a plurality of pixels.

[0111] (Configuration 3) The imaging device according to configuration 1 or 2, wherein the source follower section is shared by a plurality of pixels.

[0112] (Configuration 4) An imaging device described in any one of configurations 1 to 3, characterized in that each of the pixels has a color filter on its front surface, and the color filter transmits light of at least one wavelength band of red, green, blue, and invisible light.

[0113] (Configuration 5) The imaging device according to configuration 4, wherein the current amount control section causes the current amount to differ for pixels having color filters of different colors.

[0114] (Configuration 6) An amplifier is provided for amplifying a signal corresponding to the charge generated in the plurality of pixels, 6. The imaging device according to any one of configurations 1 to 5, wherein the current amount control section varies the amount of current depending on an amplification factor of the amplifier means.

[0115] (Configuration 7) The imaging device according to any one of configurations 1 to 6, wherein the current amount control section varies the amount of current depending on the level of the output signal output from the voltage holding section.

[0116] (Configuration 8) An imaging device described in any one of configurations 1 to 7, characterized in that each of the pixels has multiple photoelectric conversion units, and the current amount control unit makes the amount of current different when the charges of the multiple photoelectric conversion units are read out separately and when they are added together and read out.

[0117] (Configuration 9) An imaging device described in any one of configurations 1 to 8, comprising a first readout mode in which signals from a plurality of the pixels are thinned out and read out, and a second readout mode in which signals from a plurality of the pixels are read out without thinning out, wherein the current amount control unit differentiates the amount of current between the first readout mode and the second readout mode.

[0118] (Method) An imaging method for controlling an imaging device having a plurality of pixels each having a photoelectric conversion unit, a charge accumulation unit that accumulates charge generated in the photoelectric conversion unit, a source follower unit that generates a voltage corresponding to the charge in the charge accumulation unit, and a voltage holding unit for holding the voltage generated in the source follower unit, characterized in that when charges generated in a plurality of the pixels are transferred collectively to the charge accumulation unit, and the voltage corresponding to the charge is generated in the source follower unit and held in the voltage holding unit, the imaging method controls the amount of current supplied to the source follower unit to be different depending on the amount of charge in the charge accumulation unit.

[0119] (Program) A computer program for controlling each unit of the imaging device according to any one of configurations 1 to 9 by a computer.

[0120] In order to realize a part or all of the control in the above-mentioned embodiment, a computer program that realizes the functions of the above-mentioned embodiment may be supplied to an imaging device or the like via a network or various storage media. Then, a computer (or a CPU, MPU, or the like) in the imaging device or the like may read and execute the program. In this case, the program and the storage medium storing the program constitute the present invention. [Explanation of symbols]

[0121] 1:Optical system 2: Image sensor 3: Signal processing section 4: Compression and expansion section 5: Synchronization control section 6:Operation unit 7: Image display section 8: Image recording section 10(pq), 101, 102: Photodiode 11(pq):Pixel circuit 111: Current amount control unit 12(pq): Multilayer circuit 20: Vertical scanning circuit 30: Horizontal scanning circuit 40: Timing generation circuit 50: Output section TX: Transfer transistor FD: Charge storage section (floating diffusion) RES1, RES2: Reset transistors SF1, SF2: Amplification transistors SEL1, SEL2: selection transistors CCS1, CCS2: Current source CONT: Electrical contact MWS, MWN: Write transistor CS, CN: Voltage holding capacitance

Claims

1. A plurality of pixels each having a photoelectric conversion unit; a charge storage unit that stores charges generated in the photoelectric conversion unit; a source follower unit that generates a voltage corresponding to the charge in the charge storage unit; a voltage holding unit for holding the voltage generated by the source follower unit; a current amount control unit that controls the amount of current supplied to the source follower unit to be different depending on the amount of charge in the charge accumulation unit when the charges generated in a plurality of the pixels are transferred collectively to the charge accumulation unit and the voltage corresponding to the charges is generated in the source follower unit and held in the voltage holding unit.

2. The imaging device according to claim 1 , wherein the current amount control section is shared by a plurality of pixels.

3. 2. The imaging device according to claim 1, wherein the source follower section is shared by a plurality of pixels.

4. 2. The imaging device according to claim 1, wherein the pixels each have a color filter on a front surface thereof, the color filter transmitting light of at least one wavelength band of red, green, blue, and invisible light.

5. 5. The image pickup apparatus according to claim 4, wherein the current amount control section varies the amount of current for pixels having color filters of different colors.

6. an amplifier for amplifying a signal corresponding to the charges generated in the plurality of pixels; 2. The image pickup apparatus according to claim 1, wherein the current amount control section varies the current amount according to an amplification factor of the amplifier means.

7. 2. The image pickup apparatus according to claim 1, wherein the current amount control section varies the amount of current depending on the level of the output signal output from the voltage holding section.

8. The imaging device according to claim 1, wherein each of the pixels has a plurality of photoelectric conversion units, and the current amount control unit makes the amount of current different when the charges of the plurality of photoelectric conversion units are read out separately and when the charges are added together and read out.

9. a first readout mode in which signals of the plurality of pixels are thinned and read out; a second readout mode in which signals of the plurality of pixels are read out without being thinned out; Equipped with 2 . The image pickup apparatus according to claim 1 , wherein the current amount control unit makes the current amount different between the first readout mode and the second readout mode.

10. A plurality of pixels each having a photoelectric conversion unit; a charge storage unit that stores charges generated in the photoelectric conversion unit; a source follower unit that generates a voltage corresponding to the charge in the charge storage unit; a voltage holding unit for holding the voltage generated by the source follower unit, an imaging method comprising the steps of: transferring charges generated in a plurality of pixels to the charge accumulation section all at once; generating the voltage corresponding to the charges in the source follower section and holding it in the voltage holding section; and controlling the amount of current supplied to the source follower section to be different depending on the amount of charge in the charge accumulation section.

11. A computer program for controlling each unit of the imaging device according to any one of claims 1 to 9 by a computer.

Images