Imaging element

Abstract

To provide an imaging element for shortening reading time of a pixel signal, performing reading processing of a signal of a pixel at high speed, and improving a frame rate in imaging.SOLUTION: The imaging element includes: a first pixel which has a first photoelectric conversion part for converting light into an electric charge; a second pixel which has a second photoelectric conversion part which is a photoelectric conversion part for converting the light into the electric charge and is arranged side by side with the first photoelectric conversion part in a row direction; a first signal line which is electrically connected to the first pixel; a second signal line which is electrically connected to the second pixel; a first comparison part which has a first input terminal electrically connected to the first signal line and a first output terminal; a first storage part which is electrically connected to the first output terminal; a second comparison part which has a second input terminal electrically connected to the second signal line and a second output terminal; and a second storage part which is electrically connected to the first output terminal and the second output terminal.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an imaging device.

Background Art

[0002] Conventionally, an imaging device having a storage unit that stores a digital value corresponding to the amount of light received by a pixel, and a storage unit that temporarily stores a digital value for signal processing and horizontal transfer control has been known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] According to a first aspect of the invention, the imaging device includes a first pixel having a first photoelectric conversion unit that converts light into charges, a second pixel having a photoelectric conversion unit that converts light into charges and is arranged side by side with the first photoelectric conversion unit in the row direction, a first signal line electrically connected to the first pixel, a second signal line electrically connected to the second pixel, a first comparison unit having a first input terminal electrically connected to the first signal line and a first output terminal, a first storage unit electrically connected to the first output terminal, a second comparison unit having a second input terminal electrically connected to the second signal line and a second output terminal, and a second storage unit electrically connected to the first output terminal and the second output terminal.

Brief Description of the Drawings

[0005]

Figure 1

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[0006] (First Embodiment) FIG. 1 is a diagram showing a configuration example of a camera 1 which is an example of an imaging device according to the first embodiment. The camera 1 includes a photographing optical system (imaging optical system) 2, an imaging device 3, a control unit 4, a memory 5, a display unit 6, and an operation unit 7. The photographing optical system 2 has a plurality of lenses including a focus adjustment lens (focus lens) and an aperture stop, and forms a subject image on the imaging device 3. Note that the photographing optical system 2 may be detachable from the camera 1.

[0007] The imaging device 3 is an imaging device such as a CMOS image sensor or a CCD image sensor. The imaging device 3 receives the light beam that has passed through the photographing optical system 2 and images the subject image formed by the photographing optical system 2. A plurality of pixels having a photoelectric conversion unit are arranged in a two-dimensional manner (row direction and column direction) in the imaging device 3. The photoelectric conversion element is constituted by a photodiode (PD). The imaging device 3 photoelectrically converts the received light to generate a signal, and outputs the generated signal to the control unit 4.

[0008] The memory 5 is a recording medium such as a memory card. Image data, control programs, etc. are recorded in the memory 5. Writing data to the memory 5 and reading data from the memory 5 are controlled by the control unit 4. The display unit 6 displays an image based on the image data, information related to shooting such as shutter speed and aperture value, and a menu screen, etc. The operation unit 7 includes various setting switches such as a release button, a power switch, and switches for switching various modes, and outputs signals based on respective operations to the control unit 4.

[0009] The control unit 4 is composed of a processor such as a CPU, FPGA, ASIC, etc., and memories such as a ROM and a RAM, and controls each part of the camera 1 based on a control program. The control unit 4 supplies a signal for controlling the imaging element 3 to the imaging element 3 to control the operation of the imaging element 3. Also, the control unit 4 performs various image processes on the signal output from the imaging element 3 to generate image data. The control unit 4 is also an image generation unit that generates image data, and generates still image data and moving image data based on the signal output from the imaging element 3. The image processes include image processes such as gradation conversion processing and color interpolation processing.

[0010] The control unit 4 performs a process of individually reading signals of all pixels of the imaging element 3 and a process of mixing (adding) and reading signals of a plurality of pixels. The control unit 4 controls the imaging element 3 to select (set) a method for reading pixel signals. For example, when the control unit 4 displays a through image (live view image) of a subject on the display unit 6 or when performing video shooting, it performs a process of mixing and reading signals of a plurality of pixels. Also, when performing high-resolution still image shooting, the control unit 4 performs a process of individually reading signals of all pixels.

[0011] FIG. 2 is a block diagram showing a configuration example of an image sensor according to the first embodiment. The image sensor 3 is configured by laminating a first substrate 111 on which a plurality of pixels 10 are formed and a second substrate 112 on which a plurality of analog / digital conversion units (AD conversion units) 40 are formed. The first substrate 111 and the second substrate 112 are each configured using a semiconductor substrate. The circuits provided on the first substrate 111 and the circuits provided on the second substrate 112 are electrically connected by bumps, electrodes, etc.

[0012] The first substrate 111 has a plurality of pixels 10 arranged two-dimensionally. The pixel 10 outputs a photoelectric conversion signal and a dark signal, which will be described later, to the second substrate 112. In FIG. 2, the pixel 10 in the upper left corner is defined as the pixel 10(1,1) in the first row and the first column, and the pixel 10 in the lower right corner is defined as the pixel 10(4,4) in the fourth row and the fourth column, and 16 pixels 10 in 4 pixels in the row direction × 4 pixels in the column direction are shown. Note that the number and arrangement of the pixels arranged in the image sensor are not limited to the illustrated example.

[0013] The second substrate 112 has a plurality of AD conversion units 40. In the present embodiment, the AD conversion unit 40 is provided for each pixel 10. In FIG. 2, 16 AD conversion units 40 from the AD conversion unit 40(1,1) to the AD conversion unit 40(4,4) are shown. As will be described later, the AD conversion unit 40 includes a comparison unit and a storage unit, and converts the input photoelectric conversion signal and dark signal into digital signals having a predetermined number of bits, respectively.

[0014] FIG. 3 is a circuit diagram showing a configuration example of a part of the image sensor according to the first embodiment. The image sensor 3 has a plurality of pixels 10, a plurality of AD conversion units 40, a read control unit 60, a signal processing unit 70, and an input / output unit 80.

[0015] Pixel 10 includes a photoelectric conversion unit 11, a transfer unit 12, a reset unit 13, a floating diffusion (FD) 14, an amplification unit 15, and a current source 16. The photoelectric conversion unit 11 is a photodiode PD that converts incident light into charges and accumulates the photoelectrically converted charges. The transfer unit 12 is composed of a transistor M1 controlled by a signal TX and transfers the charges photoelectrically converted by the photoelectric conversion unit 11 to the FD 14. The transistor M1 is a transfer transistor. The FD 14 accumulates (holds) the charges transferred to the FD 14. The current source 16 generates a current for reading a signal from the pixel 10 and supplies the generated current to the signal line 18 and the amplification unit 15.

[0016] The amplification unit 15 is composed of a transistor M3 whose gate (terminal) is connected to the FD 14, amplifies the signal due to the charges accumulated in the FD 14, and outputs it to the signal line 18. The transistor M3 is an amplification transistor. The reset unit 13 is composed of a transistor M2 controlled by a signal RST, discharges the charges accumulated in the FD 14, and resets the voltage of the FD 14. The transistor M2 is a reset transistor.

[0017] The pixel 10 sequentially outputs, to the signal line 18, a signal (dark signal) when the voltage of the FD 14 is reset and a signal (photoelectric conversion signal) corresponding to the charges transferred from the photoelectric conversion unit 11 to the FD 14 by the transfer unit 12. The dark signal is an analog signal indicating a reference level with respect to the photoelectric conversion signal. Also, the photoelectric conversion signal is an analog signal generated based on the charges photoelectrically converted by the photoelectric conversion unit 11. The dark signal and the photoelectric conversion signal sequentially output from the pixel 10 are input to the AD conversion unit 40 via the signal line 18 and bumps or the like.

[0018] The AD conversion unit 40 includes a comparison unit 20, a switch SW1, a storage unit 25, and a selection unit 30. The comparison unit 20 is configured to include a comparator circuit. A ramp signal, which is a reference signal that changes with the passage of time from a signal generation circuit (not shown), is input to the first terminal 21 of the comparison unit 20. A signal (photoelectric conversion signal, dark signal) output from the pixel 10 to the signal line 18 is input to the second terminal 22 of the comparison unit 20, either directly or after being amplified by an amplification circuit (not shown). The comparison unit 20 compares the signal input from the pixel 10 with the reference signal, and outputs an output signal, which is the comparison result, from the output terminal 23.

[0019] The comparison unit 20 is connected to the storage unit 25 via the switch SW1. The switch SW1 is composed of a transistor and electrically connects or disconnects the comparison unit 20 and the storage unit 25. When the switch SW1 is in the on state, it outputs the output signal of the comparison unit 20 to the storage unit 25.

[0020] The storage unit 25 is composed of a plurality of latch circuits corresponding to the number of bits of the digital signal to be stored. An output signal indicating the comparison result by the comparison unit 20 is input to one input terminal (G terminal) of each latch circuit via the switch SW1. A clock signal indicating a count value is input to the other input terminal (D terminal) of each latch circuit from a counter circuit (not shown). In the example shown in FIG. 3, a clock signal indicating a count value, cnt<0> to cnt, is input to the other input terminal (D terminal) of each latch circuit respectively. <n>is input, and the AD conversion unit 40 becomes an n-bit AD conversion circuit.

[0021] Based on the output signal of the comparison unit 20 and the clock signal from the counter circuit, the storage unit 25 stores, as a digital signal, a count value corresponding to the elapsed time from the start of comparison by the comparison unit 20 until the comparison result is inverted. In other words, based on the signal output from the comparison unit 20, the storage unit 25 stores, as a digital signal, a count value corresponding to the time until the magnitude relationship (inversion) between the level of the signal output from the pixel 10 and the level of the reference signal changes.

[0022] When the dark signal of the pixel 10 is input to the comparison unit 20, the comparison unit 20 compares the dark signal with the reference signal and outputs the comparison result to the storage unit 25. Based on the comparison result by the comparison unit 20 and the clock signal, the storage unit 25 stores, as a digital signal based on the dark signal, a count value corresponding to the elapsed time from the start of comparison by the comparison unit 20 until the inversion of the comparison result. Also, when the photoelectric conversion signal of the pixel 10 is input to the comparison unit 20, the comparison unit 20 compares the photoelectric conversion signal with the reference signal and outputs the comparison result to the storage unit 25. Based on the comparison result by the comparison unit 20 and the clock signal, the storage unit 25 stores, as a digital signal based on the photoelectric conversion signal, a count value corresponding to the elapsed time from the start of comparison by the comparison unit 20 until the inversion of the comparison result. In this way, the AD conversion unit 40 converts the photoelectric conversion signal, which is an analog signal, into a digital signal with a predetermined number of bits, and converts the dark signal, which is an analog signal, into a digital signal with a predetermined number of bits.

[0023] The selection unit 30 is composed of a multiplexer controlled by the signal SEL, and the signal of the pixel converted into a digital signal (n-bit digital signal in FIG. 3) is input from the storage unit 25. The selection unit 30 outputs the signal of the pixel input from the storage unit 25 to the signal line 50 (hereinafter referred to as the data line). The data line 50 is composed of a plurality of signal lines corresponding to the number of bits of the digital signal output from the AD conversion unit 40. In the imaging device 3, the data line 50 (n signal lines in FIG. 3) is provided for each column of a plurality of AD conversion units 40 arranged in the vertical direction, that is, the column direction (vertical direction).

[0024] The signal processing unit 70 is configured to include an amplifier circuit, a decoder circuit, and the like. The signal of the pixel converted into a digital signal (digital signal based on the dark signal, digital signal based on the photoelectric conversion signal) is input to the signal processing unit 70 via the data line 50. The processing unit 70 performs signal processing such as correlated double sampling and code conversion on the signal input from the AD conversion unit 40 via the data line 50, and outputs it to the input / output unit 80. The input / output unit 80 has an input / output circuit corresponding to a high-speed interface such as SLVS and LVDS. The input / output unit 80 outputs (transmits) the signal input from the signal processing unit 70 to the control unit 4 of the camera 1 at high speed.

[0025] The read control unit 60 is commonly provided for the plurality of pixels 10 and the plurality of AD conversion units 40. The read control unit 60 is composed of a plurality of circuits including a timing generator, and is arranged separately on the first substrate 111 and the second substrate 112. Note that the read control unit 60 may be arranged on either the first substrate 111 or the second substrate 112, or may be arranged on different substrates from the first substrate 112 and the second substrate 112.

[0026] The read control unit 60 is controlled by the control unit 4 of the camera 1, and supplies signals such as the signal TX and the signal RST described above to each pixel 10 to control the operation of each pixel 10. The read control unit 60 supplies a signal to the gate of each transistor of the pixel 10 to put the transistor in an on state (connected state, conductive state, short-circuit state) or an off state (disconnected state, non-conductive state, open state, cut-off state).

[0027] The read control unit 60 supplies the signal SEL described above to the selection unit 30 of each AD conversion unit 40 to control the selection unit 30 of each AD conversion unit 40. When the selection unit 30 is enabled (turned on) by the read control unit 60, the signal of the pixel converted into a digital signal input from the storage unit 25 is output to the signal processing unit 70 via the data line 50. The read control unit 60 sequentially turns on the selection unit 30 of each AD conversion unit 40, and causes the signal of the pixel stored in the storage unit 25 connected to the turned-on selection unit 30 to be output to the data line 50. It can also be said that the read control unit 60 sequentially selects a plurality of AD conversion units 40 and reads out the signal of the pixel converted into a digital signal from the selected AD conversion unit 40. The signal processing unit 70 receives the signal of the n-bit pixel converted into a digital signal for each data line 50.

[0028] FIG. 4 is a diagram for explaining the read process of the image sensor according to the first embodiment. The image sensor 3 is provided with a switch SW2 (switches SW2a to SW2h in FIG. 4) for connecting or disconnecting the comparison unit 20 of the AD conversion unit 40 and the storage unit 25 of the AD conversion unit 40 different from the AD conversion unit 40. In the present embodiment, the switch SW2 connects the output terminal 23 of the comparison unit 20 of one AD conversion unit 40 and the input terminal (G terminal) of the storage unit 25 of the other AD conversion unit 40 among two adjacent AD conversion units 40 in the row direction.

[0029] In the example shown in FIG. 4, a switch SW2 is provided between each comparator 20 of the AD conversion units 40 in the odd-numbered columns and each memory unit 25 of the AD conversion units 40 in the even-numbered columns. The switch SW2 is composed of transistors. For example, the switch SW2a is a connection part 2a that connects the comparator 20 of the AD conversion unit 40(1,1) and the memory unit 25 of the AD conversion unit 40(1,2) among the AD conversion units 40 in the first row. The switch SW2e is a connection part 2e that connects the comparator 20 of the AD conversion unit 40(3,1) and the memory unit 25 of the AD conversion unit 40(3,2) among the AD conversion units 40 in the third row. The read control unit 60 (see FIG. 3) supplies signals to each of the switches SW2a to SW2h to control the on / off of each switch.

[0030] The read control unit 60 performs a process of individually reading out the signals of each pixel of the imaging device 3 (individual readout process) and a process of adding and reading out the signals of a plurality of pixels (addition readout process). In the individual readout process, the read control unit 60 sequentially selects the AD conversion units 40 of the imaging device 3 row by row, from the first row to the fourth row in FIG. 4, and reads out the pixel signals from the selected AD conversion units 40.

[0031] In the addition readout process, as shown in FIG. 5(a), the read control unit 60 controls a plurality of switches SW to connect the respective FD14s of the plurality of pixels 10 to each other, thereby adding the signals of the plurality of pixels. Note that the read control unit 60 may also add the signals of the plurality of pixels by controlling a plurality of switches SW to connect the amplification units 15 of the plurality of pixels 10 to the same signal line 18, as shown in FIG. 5(b). The read control unit 60 selects, row by row or multiple rows at a time, some of the AD conversion units 40 (hereinafter referred to as the first AD conversion units) into which the signal generated by adding the signals of the plurality of pixels is input among the plurality of AD conversion units 40 of the imaging device 3, and performs a process of reading out the pixel signals.

[0032] In this embodiment, the addition readout process has a first readout method, a second readout method, and a third readout method. The first readout method is a method of sequentially selecting the first AD conversion unit 40 for each row and reading out the signals of the pixels converted into digital signals. The first AD conversion unit 40 is an AD conversion unit that is selected by thinning out the AD conversion units 40 in specific rows or columns among all the AD conversion units 40. The first AD conversion unit 40 receives the signals of the added pixels and converts the signals of the added pixels into digital signals.

[0033] The second readout method is a method of sequentially selecting the first AD conversion unit 40 for each of a plurality of rows and reading out the signals of the pixels converted into digital signals. The third readout method is a method of performing AD conversion of the signals of the pixels (for example, photoelectric conversion signals) and reading out the signals of the pixels (for example, digital signals based on dark signals) converted into digital signals simultaneously (in parallel). The control unit 4 of the camera 1 controls the readout control unit 60 to switch the method of reading out the signals of the pixels.

[0034] (Individual readout process) In the individual readout process, the readout control unit 60 turns on the switches SW1 of the plurality of AD conversion units 40 of the imaging device 3 to cause each AD conversion unit 40 to perform AD conversion. The readout control unit 60 sequentially selects these plurality of AD conversion units 40 in units of one row and sequentially outputs the signals of the pixels converted into digital signals from the selected AD conversion unit 40 to the data line 50.

[0035] (First readout method of addition readout process) In the first reading method, the read control unit 60 turns on the switches SW1 of the plurality of first AD conversion units 40 respectively, and causes each of the plurality of first AD conversion units 40 to perform AD conversion. The read control unit 60 sequentially selects these plurality of first AD conversion units 40 in units of one row, and causes the pixel signals converted into digital signals from the selected first AD conversion unit 40 to be output to the data line 50. Thus, in the case of the first reading method, the read control unit 60 uses only the first AD conversion units 40 among all the AD conversion units 40. The other AD conversion units 40 different from the first AD conversion units 40 (hereinafter referred to as the second AD conversion units) and the data lines 50 to which these second AD conversion units 40 are connected are not used and are in a standby state in the case of the first reading method.

[0036] (Second Reading Method of Additive Readout Processing) In the second reading method, the read control unit 60 controls the switch SW1 and the switch SW2, and in addition to the first AD conversion unit 40, also uses the storage unit 25 and the selection unit 30 of the second AD conversion unit 40 and the data line 50 connected to the second AD conversion unit 40. In the second reading method, by using the data lines 50 provided for different columns, it is possible to simultaneously read out the pixel signals converted into digital signals from the AD conversion units 40 of a plurality of rows. The imaging device 3 can read out the pixel signals in a shorter time than when the first AD conversion units 40 are selected in units of one row and the pixel signals are sequentially read out to the data line 50.

[0037] (Third Reading Method of Additive Readout Processing) Also in the case of the third reading method, in addition to the first AD conversion unit 40, the reading control unit 60 uses the storage unit 25 and the selection unit 30 of the second AD conversion unit 40 and the data line 50 connected to the second AD conversion unit 40. The reading control unit 60 controls the switch SW1 and the switch SW2 to control whether to output the output signal of the comparison unit 20 of the first AD conversion unit 40 to the storage unit 25 of the first AD conversion unit 40 or the storage unit 25 of the second AD conversion unit 40. It can also be said that the reading control unit 60 switches the storage unit 25 that is the output destination of the comparison result by the comparison unit 20 of the first AD conversion unit 40.

[0038] In the third reading method, when a dark signal is input to the comparison unit 20 of the first AD conversion unit 40 and when a photoelectric conversion signal is input to the comparison unit 20 of the first AD conversion unit 40, the reading control unit 60 switches the connection destination of the comparison unit 20 of the first AD conversion unit 40 to the storage unit 25 of the first AD conversion unit 40 or the storage unit 25 of the second AD conversion unit 40. For example, when a dark signal is input to the comparison unit 20 of the first AD conversion unit 40, the reading control unit 60 connects the comparison unit 20 of the first AD conversion unit 40 and the storage unit 25 of the first AD conversion unit 40. The comparison unit 20 of the first AD conversion unit 40 outputs an output signal indicating the comparison result between the dark signal and the reference signal to the storage unit 25 of the first AD conversion unit 40 via the switch SW1. The storage unit 25 of the first AD conversion unit 40 stores a digital signal based on the dark signal based on the output signal of the comparison unit 20.

[0039] After the AD conversion of the dark signal is completed, the read control unit 60 starts reading the digital signal based on the dark signal from the storage unit 25 of the first AD conversion unit 40 to the data line 50. Further, the read control unit 60 connects the comparison unit 20 of the first AD conversion unit 40 and the storage unit 25 of the second AD conversion unit 40. At this time, when a photoelectric conversion signal is input to the comparison unit 20 of the first AD conversion unit 40, the comparison unit 20 of the first AD conversion unit 40 outputs an output signal indicating the comparison result between the photoelectric conversion signal and the reference signal to the storage unit 25 of the second AD conversion unit 40 via the switch SW2. The storage unit 25 of the second AD conversion unit 40 stores the digital signal based on the photoelectric conversion signal based on the output signal of the comparison unit 20 of the first AD conversion unit 40.

[0040] Thus, in the third read method, when performing AD conversion of the dark signal and when performing AD conversion of the photoelectric conversion signal, AD conversion is performed using different storage units 25. Thereby, reading of the digital signal based on the dark signal and AD conversion of the photoelectric conversion signal can be performed in parallel. Similarly, reading of the digital signal based on the photoelectric conversion signal and AD conversion of the dark signal can be performed in parallel. For this reason, the imaging device 3 does not need to wait for the completion of the read process of the pixel signal to the data line 50 and can start the next AD conversion process, and can read the pixel signal in a short time. Hereinafter, with reference to FIGS. 4 to 10, the first to third read methods of the individual read process and the addition read process will be further described.

[0041] (Individual read process) When the individual read process is instructed by the control unit 4, the read control unit 60 turns on each switch SW1 of the AD conversion units 40(1,1) to 40(4,4) and turns off the switches SW2a to SW2h as shown in FIG. 4.

[0042] The read control unit 60 turns on the reset units 13 of pixels 10(1,1) to 10(4,4). As a result, the voltages of the respective FD14s in each pixel 10 are reset. The dark signals of pixels 10(1,1) to 10(4,4) are output to the AD conversion units 40(1,1) to 40(4,4) via the signal lines 18 connected to the respective pixels 10. The AD conversion units 40(1,1) to 40(4,4) convert the input dark signals into digital signals. Digital signals based on the dark signals of pixels 10(1,1) to 10(4,4) are stored in the respective storage units 25 of the AD conversion units 40(1,1) to 40(4,4).

[0043] The read control unit 60 turns on the selection units 30 of the AD conversion units 40(1,1) to 40(1,4), which are the AD conversion units in the first row, and turns off the selection units 30 of the AD conversion units 40 in the other rows except the first row. As a result, the digital signals based on the dark signals of the respective AD conversion units 40(1,1) to 40(1,4) are output to the data lines 50a to 50d via the selection units 30 of the respective AD conversion units 40.

[0044] After reading the digital signals based on the dark signals from each AD conversion unit 40 in the first row, the read control unit 60 turns on the selection units 30 of the AD conversion units 40(2,1) to 40(2,4), which are the AD conversion units in the second row, and turns off the selection units 30 of the AD conversion units 40 in the other rows except the second row. As a result, the digital signals based on the dark signals of the respective AD conversion units 40(2,1) to 40(2,4) are output to the data lines 50a to 50d via the selection units 30 of the respective AD conversion units 40. Similarly, the read control unit 60 sequentially selects the AD conversion units 40 after the third row, one row at a time in the order of the third row, the fourth row, and the fifth row, and reads the digital signals based on the dark signals from the selected AD conversion units 40.

[0045] The read control unit 60 turns on the transfer units 12 of pixels 10(1,1) to 10(4,4) respectively. As a result, in each pixel 10, the charges photoelectrically converted by the respective PD11s are transferred to the FD14s. The photoelectric conversion signals of pixels 10(1,1) to 10(4,4) are output to the AD conversion units 40(1,1) to 40(4,4) respectively via the signal lines 18 connected to the respective pixels 10. The AD conversion units 40(1,1) to 40(4,4) convert the input photoelectric conversion signals into digital signals. Digital signals based on the photoelectric conversion signals of pixels 10(1,1) to 10(4,4) are stored in the respective storage units 25 of the AD conversion units 40(1,1) to 40(4,4).

[0046] In the same manner as when the read control unit 60 reads out the digital signals based on the dark signals from each AD conversion unit 40, the read control unit 60 sequentially selects one row at a time in the order of the first row, the second row, the third row, the fourth row, and the fifth row, and reads out the digital signals based on the photoelectric conversion signals from the selected AD conversion units 40.

[0047] In this way, in the individual read process, the read control unit 60 individually reads the signals of the pixels of the imaging device 3. The digital signals based on the dark signals and the digital signals based on the photoelectric conversion signals sequentially output to the data lines 50a to 50d are subjected to signal processing such as correlated double sampling by the signal processing unit 70 (see FIG. 3), and then output to the control unit 4 via the input / output unit 80.

[0048] (The first to third read methods of the addition read process) In the first to third readout methods of the addition readout process, the readout control unit 60 adds the signals of the plurality of pixels for each of the plurality of pixels. Hereinafter, an example in which the signals of four pixels of 2 pixels × 2 pixels are added will be described. The signal obtained by adding the signal of pixel 10(1,1), the signal of pixel 10(1,2), the signal of pixel 10(2,1), and the signal of pixel 10(2,2) is input to the AD conversion unit 40(1,1). The signal obtained by adding the signals of pixel 10(1,3), pixel 10(1,4), pixel 10(2,3), and pixel 10(2,4) is input to the AD conversion unit 40(1,3). Also, the signal obtained by adding the signals of pixel 10(3,1), pixel 10(3,2), pixel 10(4,1), and pixel 10(4,2) is input to the AD conversion unit 40(3,1), and the signal obtained by adding the signals of pixel 10(3,3), pixel 10(3,4), pixel 10(4,3), and pixel 10(4,4) is input to the AD conversion unit 40(3,3).

[0049] The AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3) function as the first AD conversion unit described above. In FIG. 6, these AD conversion units 40 surrounded by thick lines are examples of the AD conversion units used in the case of the first readout method. Note that the AD conversion units 40 surrounded by thick lines in FIG. 7 are examples of the AD conversion units used in the case of the second readout method, and the AD conversion units 40 surrounded by thick lines in FIGS. 8 and 9 are examples of the AD conversion units used in the case of the third readout method.

[0050] (The first readout method of the addition readout process) When the read control unit 60 is instructed by the control unit 4 to use the first read method, as shown in FIG. 6, it turns on the switch SW1 of each of the AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3), and turns off the switches SW2a to SW2h. When the added dark signal is input to the AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3), they convert the dark signal into a digital signal. Digital signals based on the added dark signal are stored in the storage units 25 of the AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3), respectively.

[0051] The read control unit 60 turns on the selection units 30 of the AD conversion units 40(1,1) and 40(1,3) in the first row, respectively, and turns off the selection units 30 of the other AD conversion units 40 different from the AD conversion units 40(1,1) and 40(1,3). As a result, the digital signal based on the added dark signal of the AD conversion unit 40(1,1) is output to the data line 50a via the selection unit 30 of the AD conversion unit 40(1,1). Also, the digital signal based on the added dark signal of the AD conversion unit 40(1,3) is output to the data line 50c via the selection unit 30 of the AD conversion unit 40(1,3).

[0052] After reading the digital signals based on the dark signals from the AD conversion units 40(1,1) and 40(1,3) in the first row, the read control unit 60 turns on the selection units 30 of the AD conversion units 40(3,1) and 40(3,3) in the third row respectively. Also, the read control unit 60 turns off the selection units 30 of the other AD conversion units 40 different from the AD conversion units 40(3,1) and 40(3,3) respectively. Thereby, the digital signal based on the added dark signal of the AD conversion unit 40(3,1) is output to the data line 50a via the selection unit 30 of the AD conversion unit 40(3,1). Also, the digital signal based on the added dark signal of the AD conversion unit 40(3,3) is output to the data line 50c via the selection unit 30 of the AD conversion unit 40(3,3). Thereafter, in the same manner, the read control unit 60 sequentially selects the AD conversion units 40 every other row, and reads the digital signals based on the dark signals from each selected AD conversion unit 40.

[0053] When the added photoelectric conversion signals are input, the AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3) convert the photoelectric conversion signals into digital signals. In the respective storage units 25 of the AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3), the digital signals based on the added photoelectric conversion signals are stored respectively. The read control unit 60 sequentially selects the AD conversion units 40 every other row in the same manner as when reading the digital signals based on the dark signals from each AD conversion unit 40, and reads the digital signals based on the photoelectric conversion signals from each selected AD conversion unit 40.

[0054] Thus, in the first read method, the read control unit 60 sequentially selects some of all the AD conversion units 40 of the imaging device 3 one row at a time, and reads the signals of the pixels converted into digital signals. The digital signals based on the dark signals and the digital signals based on the photoelectric conversion signals sequentially output to the data lines 50a and 50c are output to the control unit 4 by the input / output unit 80 after being signal-processed by the signal processing unit 70.

[0055] (Second Readout Method for Addition Readout Processing) When the second readout method is instructed by the control unit 4, the readout control unit 60 turns on each switch SW1 of the AD conversion units 40(1,1) and 40(1,3) as shown in FIG. 7. Also, the readout control unit 60 turns on the switch SW2e and the switch SW2f. When the switch SW2e is turned on, the comparison unit 20 of the AD conversion unit 40(3,1) and the storage unit 25 of the AD conversion unit 40(3,2) are electrically connected. Also, when the switch SW2f is turned on, the comparison unit 20 of the AD conversion unit 40(3,3) and the storage unit 25 of the AD conversion unit 40(3,4) are electrically connected. The AD conversion units 40(3,2) and 40(3,4) function as the second AD conversion units described above.

[0056] When the added dark signal is input to the AD conversion units 40(1,1) and 40(1,3), the AD conversion units 40(1,1) and 40(1,3) convert the dark signal into a digital signal. Digital signals based on the added dark signal are stored in the respective storage units 25 of the AD conversion units 40(1,1) and 40(1,3).

[0057] When the added dark signal is input to the comparison unit 20 of the AD conversion unit 40(3,1), the comparison unit 20 outputs an output signal indicating the comparison result between the dark signal and the reference signal to the storage unit 25 of the AD conversion unit 40(3,2) via the switch SW2e. The storage unit 25 of the AD conversion unit 40(3,2) stores a digital signal based on the added dark signal based on the output signal of the comparison unit 20 of the AD conversion unit 40(3,1). In this way, the added dark signal input to the comparison unit 20 of the AD conversion unit 40(3,1) is converted into a digital signal by the comparison unit 20 of the AD conversion unit 40(3,1) and the storage unit 25 of the AD conversion unit 40(3,2).

[0058] When the comparison unit 20 of the AD conversion unit 40(3,3) receives the added dark signal, it outputs an output signal indicating the comparison result between the dark signal and the reference signal to the storage unit 25 of the AD conversion unit 40(3,4) via the switch SW2f. The storage unit 25 of the AD conversion unit 40(3,4) stores a digital signal based on the added dark signal based on the output signal of the comparison unit 20 of the AD conversion unit 40(3,3). In this way, the added dark signal input to the comparison unit 20 of the AD conversion unit 40(3,3) is converted into a digital signal by the comparison unit 20 of the AD conversion unit 40(3,3) and the storage unit 25 of the AD conversion unit 40(3,4).

[0059] The read control unit 60 turns on each of the selection units 30 of the AD conversion units 40(1,1) and 40(1,3) in the first row, and each of the selection units 30 of the AD conversion units 40(3,2) and 40(3,4) in the third row. Also, the read control unit 60 turns off the selection units 30 of the other AD conversion units 40 different from the AD conversion units 40(1,1), 40(1,3), 40(3,2), and 40(3,4).

[0060] The added dark signal input to the comparison unit 20 of the AD conversion unit 40(1,1) is converted into a digital signal by the AD conversion unit 40(1,1) and then output to the data line 50a via the selection unit 30 of the AD conversion unit 40(1,1), as schematically shown by the arrow 90a. Also, the added dark signal input to the comparison unit 20 of the AD conversion unit 40(3,1) is converted into a digital signal by the comparison unit 20 of the AD conversion unit 40(3,1) and the storage unit 25 of the AD conversion unit 40(3,2) and then output to the data line 50b via the selection unit 30 of the AD conversion unit 40(3,2), as schematically shown by the arrow 90b.

[0061] The added dark signal input to the comparison unit 20 of the AD conversion unit 40(1, 3) is converted into a digital signal by the AD conversion unit 40(1, 3) and then output to the data line 50c via the selection unit 30 of the AD conversion unit 40(1, 3), as schematically shown by arrow 90c. Also, the added dark signal input to the comparison unit 20 of the AD conversion unit 40(3, 3) is converted into a digital signal by the comparison unit 20 of the AD conversion unit 40(3, 3) and the storage unit 25 of the AD conversion unit 40(3, 4), and then output to the data line 50d via the selection unit 30 of the AD conversion unit 40(3, 4), as schematically shown by arrow 90d. Thereafter, in the same manner, the read control unit 60 sequentially selects the AD conversion units 40 two rows at a time and reads out the digital signal based on the dark signal from each selected AD conversion unit 40.

[0062] When the added photoelectric conversion signal is input, the AD conversion units 40(1, 1) and 40(1, 3) convert the photoelectric conversion signal into a digital signal. Digital signals based on the added photoelectric conversion signal are stored in the respective storage units 25 of the AD conversion units 40(1, 1) and 40(1, 3). The added photoelectric conversion signal input to the comparison unit 20 of the AD conversion unit 40(3, 1) is converted into a digital signal by the comparison unit 20 of the AD conversion unit 40(3, 1) and the storage unit 25 of the AD conversion unit 40(3, 2), and is stored in the storage unit 25 of the AD conversion unit 40(3, 2). Also, the added photoelectric conversion signal input to the comparison unit 20 of the AD conversion unit 40(3, 3) is converted into a digital signal by the comparison unit 20 of the AD conversion unit 40(3, 3) and the storage unit 25 of the AD conversion unit 40(3, 4), and is stored in the storage unit 25 of the AD conversion unit 40(3, 4).

[0063] The read control unit 60 sequentially selects the AD conversion units 40 two rows at a time in the same manner as when reading out the digital signal based on the dark signal from each AD conversion unit 40, and reads out the digital signal based on the photoelectric conversion signal from each selected AD conversion unit 40.

[0064] As described above, in the second reading method, the reading control unit 60 controls the switches SW1 and SW2 to also use the AD conversion unit 40 that is in a standby state in the case of the first reading method and the data lines 50b and 50d connected to the AD conversion unit 40. Therefore, the reading control unit 60 can sequentially select two rows of the AD conversion unit 40 at a time and read out the signals of the pixels converted into digital signals. As a result, the signals of the pixels can be read out in a shorter time than when the AD conversion unit 40 is sequentially selected one row at a time to read out the pixel signals. The digital signals based on the dark signals sequentially output to the data lines 50a to 50d and the digital signals based on the photoelectric conversion signals are subjected to signal processing by the signal processing unit 70 and then output to the control unit 4 by the input / output unit 80.

[0065] (Third Reading Method of Addition Reading Process) FIGS. 8 and 9 are diagrams for explaining the reading process of the imaging device when the third reading method is instructed by the control unit 4. FIG. 8 shows the connection states of the switches SW1 and SW2 when the dark signal added to the comparison unit 20 of the AD conversion unit 40 is input. FIG. 9 shows the connection states of the switches SW1 and SW2 when the photoelectric conversion signal added to the comparison unit 20 of the AD conversion unit 40 is input. In the examples shown in FIGS. 8 and 9, the AD conversion units 40(1,2), 40(1,4), 40(3,2), and 40(3,4) function as the second AD conversion unit described above.

[0066] When the dark signal added to the comparison unit 20 of the AD conversion unit 40 is input, the reading control unit 60 turns on the switches SW1 of the AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3) as shown in FIG. 8. Further, the reading control unit 60 turns off the switches SW2a to SW2h.

[0067] The read control unit 60 causes each of the AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3) to perform AD conversion of the added dark signal. For example, as schematically shown by arrow 91a, the added dark signal input to the comparator 20 of the AD conversion unit 40(1,1) is converted into a digital signal by the AD conversion unit 40(1,1) and stored in the storage unit 25 of the AD conversion unit 40(1,1). Also, as schematically shown by arrow 91c, the added dark signal input to the comparator 20 of the AD conversion unit 40(1,3) is converted into a digital signal by the AD conversion unit 40(1,3) and stored in the storage unit 25 of the AD conversion unit 40(1,3).

[0068] Simultaneously with the AD conversion of the dark signal, the read control unit 60 reads out digital signals based on the photoelectric conversion signals stored at the time of the previous AD conversion of the photoelectric conversion signals from the storage units 25 of each of the AD conversion units 40(1,2), 40(1,4), 40(3,2), and 40(3,4). For example, as schematically shown by arrow 92b, a digital signal based on the added photoelectric conversion signal is output to the data line 50b from the storage unit 25 of the AD conversion unit 40(1,2). Also, as schematically shown by arrow 92d, a digital signal based on the added photoelectric conversion signal is output to the data line 50d from the storage unit 25 of the AD conversion unit 40(1,4). Thereafter, similarly, the read control unit 60 sequentially selects the AD conversion units 40 every other row and reads out digital signals based on the photoelectric conversion signals from each selected AD conversion unit 40.

[0069] When the added photoelectric conversion signal is input to the comparator 20 of the AD conversion unit 40, the read control unit 60 turns off each switch SW1 of the AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3) as shown in FIG. 9. Also, the read control unit 60 turns on the switches SW2a, SW2b, SW2e, and SW2f.

[0070] The read control unit 60 causes each of the comparison unit 20 of the AD conversion unit 40(1,1) and the storage unit 25 of the AD conversion unit 40(1,2), the comparison unit 20 of the AD conversion unit 40(1,3) and the storage unit 25 of the AD conversion unit 40(1,4), the comparison unit 20 of the AD conversion unit 40(3,1) and the storage unit 25 of the AD conversion unit 40(3,2), and the comparison unit 20 of the AD conversion unit 40(3,3) and the storage unit 25 of the AD conversion unit 40(3,4) to perform AD conversion of the added photoelectric conversion signal. For example, as schematically shown by the arrow 91b, the added photoelectric conversion signal input to the comparison unit 20 of the AD conversion unit 40(1,1) is converted into a digital signal by the comparison unit 20 of the AD conversion unit 40(1,1) and the storage unit 25 of the AD conversion unit 40(1,2), and is stored in the storage unit 25 of the AD conversion unit 40(1,2). Also, as schematically shown by the arrow 91d, the added photoelectric conversion signal input to the comparison unit 20 of the AD conversion unit 40(1,3) is converted into a digital signal by the comparison unit 20 of the AD conversion unit 40(1,3) and the storage unit 25 of the AD conversion unit 40(1,4), and is stored in the storage unit 25 of the AD conversion unit 40(1,4).

[0071] Simultaneously with the AD conversion of the photoelectric conversion signal, the read control unit 60 reads out digital signals based on the dark signals stored at the time of the previous AD conversion of the dark signal from the storage units 25 of the AD conversion units 40(1,1), 40(1,3), 40(3,1), and 40(3,3) respectively. For example, as schematically shown by the arrow 92a, a digital signal based on the added dark signal is output to the data line 50a from the storage unit 25 of the AD conversion unit 40(1,1). Also, as schematically shown by the arrow 92c, a digital signal based on the added dark signal is output to the data line 50c from the storage unit 25 of the AD conversion unit 40(1,3). Thereafter, similarly, the read control unit 60 sequentially selects the AD conversion unit 40 every other row, and reads out digital signals based on the photoelectric conversion signal from each selected AD conversion unit 40.

[0072] Thus, in the third reading method, the read control unit 60 controls the switches SW1 and SW2 to perform AD conversion using different storage units 25 depending on whether AD conversion of the dark signal or AD conversion of the photoelectric conversion signal is performed. As a result, the imaging device 3 can perform AD conversion of the pixel signals and readout of the pixel signals converted into digital signals to the data lines 50 in parallel. Therefore, the pixel signals can be read out in a short time.

[0073] (Comparison of the First to Third Reading Methods of the Addition Readout Process) FIG. 10 is a diagram comparing the first to third reading methods of the addition readout process of the imaging device according to the first embodiment. FIG. 10(a) shows the process in the case of the first reading method, FIG. 10(b) shows the process in the case of the second reading method, and FIG. 10(c) shows the process in the case of the third reading method. Also, in FIGS. 10(a) to 10(c), on the same time axis, the readout process of the dark signal from pixel 10, the AD conversion process of the dark signal, the readout process of the digital signal based on the dark signal, the readout process of the photoelectric conversion signal from pixel 10, the AD conversion process of the photoelectric conversion signal, and the readout process of the digital signal based on the photoelectric conversion signal are shown side by side.

[0074] In the case of the second reading method of FIG. 10(b), as described above, the read control unit 60 sequentially selects two rows of the AD conversion units 40 at a time and reads out the digital signal based on the dark signal and the digital signal based on the photoelectric conversion signal. Therefore, the read control unit 60 can read out the digital signal based on the dark signal from each AD conversion unit 40 in about half the time compared to the case of the first reading method of FIG. 10(a), and can also read out the digital signal based on the photoelectric conversion signal from each AD conversion unit 40 in about half the time. As a result, the imaging device 3 can improve the frame rate during shooting.

[0075] In the case of the third readout method of FIG. 10(c), as described above, the readout control unit 60 performs the AD conversion of the dark signal (or the photoelectric conversion signal) read from the pixel and the readout of the photoelectric conversion signal (or the dark signal) converted into a digital signal in parallel. Therefore, the imaging device 3 can further improve the frame rate during shooting as compared with the case of the second readout method of FIG. 10(b).

[0076] It is also conceivable to separately provide a storage unit for AD conversion and a storage unit for signal readout to the data line 50 for each pixel 10. However, in this case, the area of the imaging device increases. In the present embodiment, it is not necessary to separately provide a storage unit for AD conversion and a storage unit for signal readout to the data line 50, and an increase in the area of the imaging device can be prevented.

[0077] According to the above-described embodiment, the following operational effects can be obtained. (1) The imaging device 3 includes a first photoelectric conversion unit 11 and a second photoelectric conversion unit 11 that generate charges by photoelectric conversion, a first comparison unit 20 that outputs a first signal based on a result of comparing a signal based on the charges generated in the first photoelectric conversion unit 11 with a reference signal, a first storage unit 25 that stores a signal based on the first signal when the first signal is output from the first comparison unit 20, a second comparison unit 20 that outputs a second signal based on a result of comparing a signal based on the charges generated in the second photoelectric conversion unit 11 with a reference signal, a second storage unit 25 that stores a signal based on the second signal when the second signal is output from the second comparison unit 20, a first connection unit (switch SW2) that can connect or disconnect the first comparison unit 20 and the second storage unit 25, and a control unit (readout control unit) that controls the first connection unit to control whether to output the first signal to the first storage unit or the second storage unit. Since it is configured in this way, the readout control unit 60 according to the present embodiment can shorten the readout time of the pixel signal by controlling the switch SW2 to perform the readout process of the pixel signal.

[0078] (2) In this embodiment, the imaging device 3 performs the second readout method and the third readout method by controlling the switches SW1 and SW2. As a result, the signal readout process of the pixels can be performed at high speed. Also, the frame rate during imaging can be improved.

[0079] The following modifications are also within the scope of the present invention, and it is also possible to combine one or more of the modification examples with the above-described embodiment.

[0080] (Modification Example 1) In the above-described embodiment, an example in which the readout control unit 60 adds signals of a plurality of pixels to perform an addition readout process has been described. The readout control unit 60 may perform a process of thinning out pixels in a specific row or column among all the pixels and reading out signals (thinning-out readout process). Also in the case of the thinning-out readout process, the readout control unit 60 may perform a readout method similar to the first to third readout methods described above.

[0081] (Modification Example 2) In the above-described embodiment, an example in which the imaging device 3 is configured by laminating the first substrate 111 and the second substrate 112 has been described. However, the first substrate 111 and the second substrate 112 do not have to be laminated.

[0082] (Modification Example 3) In the above-described embodiment, an example in which the data line 50 is composed of a plurality of signal lines corresponding to the number of bits of the digital signal output from the AD conversion unit 40 has been described. The data line 50 may be a single signal line or any number of signal lines.

[0083] (Modification Example 4) In the above-described embodiment and modification examples, an example in which a photodiode is used as the photoelectric conversion unit has been described. However, a photoelectric conversion film (organic photoelectric film) may be used as the photoelectric conversion unit.

[0084] (Modification Example 5) The imaging device and the imaging apparatus described in the above embodiments and modifications may be applied to cameras, smartphones, tablets, cameras built into PCs, in-vehicle cameras, cameras mounted on unmanned aerial vehicles (drones, radio control aircraft, etc.).

[0085] In the above, various embodiments and modifications have been described, but the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

[0086] The disclosure content of the following priority basis application is incorporated herein by reference. Japanese Patent Application No. 2019-69145 (filed on March 29, 2019)

Explanation of Reference Numerals

[0087] 1... Imaging apparatus, 3... Imaging device, 4... Control unit, 10... Pixel, 11... Photoelectric conversion unit, 20... Comparison unit, 25... Storage unit, 40... AD conversion unit, 60... Read control unit< / n>

Claims

[Claim 1] a first pixel having a first photoelectric conversion unit that converts light into an electric charge; A second pixel including a second photoelectric conversion unit that converts light into an electric charge and that is arranged alongside the first photoelectric conversion unit in the row direction; A first signal line electrically connected to the first pixel; A second signal line electrically connected to the second pixel; a first comparison section having a first input terminal electrically connected to the first signal line and a first output terminal; a first storage unit electrically connected to the first output terminal; a second comparing section having a second input terminal electrically connected to the second signal line and a second output terminal; a second storage unit electrically connected to the first output terminal and the second output terminal; An imaging element comprising:

Images