JP2015192219A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus which allows for shooting with two different exposure time.SOLUTION: An imaging apparatus transfers a first video signal, obtained by photoelectric conversion in a photoelectric conversion unit during a first exposure period, from the photoelectric conversion unit to a floating diffusion by turning a transfer gate on at the end of the first exposure period while turning a reset switch and a selection switch off; reads a first video image from the floating diffusion by turning the selection switch on, after end of the first exposure period; reads a second video signal, obtained by photoelectric conversion in the photoelectric conversion unit during a second exposure period by turning the transfer gate on at the end of the second exposure period following to the first exposure period, while the selection switch is turned on; and resets the floating diffusion by turning the reset switch on while turning the selection switch on, after reading the second video image.

Description

  The present invention relates to an imaging apparatus.

  Conventionally, in order to expand the dynamic range, a method of performing two different exposures during one frame period has been reported. For example, there is a method in which two photodiodes having different light receiving areas are provided in a pixel and two types of pixel outputs having different sensitivities are obtained (for example, see Patent Document 1).

  In addition, there is a method of obtaining a plurality of pixel outputs having different exposure times (see Non-Patent Document 1, for example).

JP 2000-125209 A

"Wide Intrascene Dynamic Range CMOS APS Using Dual Sampling", Orly Yadid-Pecht and Eric R. Fossum, IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 44, NO. 10, OCTOBER 1997 pp-1721-1722

  However, in Patent Document 1, it is necessary to manufacture a plurality of pixels having different sizes, and there is a problem that the structure and the manufacturing process are complicated.

  In Non-Patent Document 1, it is necessary to increase the reading speed to twice or more. When the speed is increased, power consumption increases, and when power consumption increases, there is a problem that noise increases due to increased heat generation.

  Therefore, an object of the present invention is to provide an imaging apparatus capable of performing imaging with two different exposure times without complicating the structure and the manufacturing process and suppressing an increase in reading speed. .

  An imaging device according to one aspect of the present invention includes a photoelectric conversion unit disposed in a pixel, a transfer gate connected to an output terminal of the photoelectric conversion unit, an output side of the transfer gate, and the transfer gate A floating diffusion that accumulates the output signal of the photoelectric conversion unit transferred via a reset switch that resets the floating diffusion, a selection switch that is connected to the floating diffusion and reads a signal, the transfer gate, the reset switch, And a drive unit that drives the selection switch, wherein the drive unit turns off the reset switch and the selection switch for a first video signal obtained by photoelectric conversion in the photoelectric conversion unit in a first exposure period. In the state, the transfer gate is turned on at the end of the first exposure period. To transfer from the photoelectric conversion unit to the floating diffusion, and after the first exposure period, the selection switch is turned on to read the first video signal from the floating diffusion, and the selection switch is turned on. The transfer gate is turned on at the end of the second exposure period following the first exposure period, and a second video signal obtained by photoelectric conversion in the photoelectric conversion unit in the second exposure period is read, and the second After the video signal is read, the floating diffusion is reset by turning on the reset switch while the selection switch is on.

  According to the present invention, it is possible to provide an imaging device capable of providing an imaging device capable of performing imaging with two different exposure times without complicating the structure and the manufacturing process and suppressing an increase in reading speed. can get.

It is a figure which shows the pixel part contained in the imaging device of embodiment. 1 is a diagram illustrating an imaging apparatus 500 according to Embodiment 1. FIG. It is a figure which shows the drive sequence of the imaging device 500 of embodiment. It is a figure which shows each signal level in the horizontal scanning period 1H of the 1st frame 1V in FIG. 3, and the horizontal scanning period 1H of the 2nd frame 2V.

  Hereinafter, embodiments to which the imaging apparatus of the present invention is applied will be described.

<Embodiment>
FIG. 1 is a diagram illustrating a pixel unit included in the imaging apparatus according to the embodiment.

  The pixel unit 100 included in the imaging device of the embodiment includes a photodiode PD, a transfer gate TX, a floating diffusion FD, a reset switch element RT, an output stage 110, and an output terminal 100A.

  One photodiode PD is provided for each of a plurality of pixels included in the imaging apparatus.

  The photodiode PD is an example of a photoelectric conversion unit. Here, a photodiode PD is shown as an example of the photoelectric conversion unit. However, the photoelectric conversion unit is not limited to a photodiode, and may be any element that can photoelectrically convert incident light and output an imaging signal.

  The photodiode PD has an anode grounded, and a cathode serving as an output terminal connected to the transfer gate TX.

  FIG. 1 shows one photodiode PD, but since there are actually a large number (N) of pixels, the pixel unit 100 includes N photodiodes PD. Here, N is an arbitrary integer of 2 or more.

  The transfer gate TX is composed of, for example, an FET (Field Effect Transistor). Here, as an example, a mode in which the transfer gate TX is an n-type FET will be described. However, the transfer gate TX is not limited to an n-type FET, and may be another type of transistor.

  The transfer gate TX has a source connected to the output terminal (cathode) of the photodiode PD and a drain connected to the floating diffusion FD. The gate of the transfer gate TX is connected to the drive unit of the imaging apparatus including the pixel unit 100 of Embodiment 1, and is driven by the drive unit.

  Note that the number of transfer gates TX is equal to the number of photodiodes PD. That is, the switch elements (TX) are connected one by one to the output side of the photodiode (PD).

  The floating diffusion FD is connected to the drain of the transfer gate TX. The floating diffusion FD is, for example, an n-type region of a pn junction diode and is electrically floating.

  The floating diffusion FD has a function like a capacitor, and accumulates an imaging signal (negative charge) output from the photodiode PD connected via the transfer gate TX.

  Since the floating diffusion FD has a predetermined saturation capacity, it is not possible to accumulate electric charges exceeding the predetermined saturation capacity. The floating diffusion FD is configured to have a predetermined saturation capacity depending on the application of the imaging device and the like. This saturation capacity corresponds to the saturation level of the floating diffusion FD. The saturation level is a level at which no more charge can be accumulated by the imaging signal.

  The reset switch element RT is, for example, an n-type FET, the source is connected to the floating diffusion FD, and the drain is connected to the power supply (VDD). The gate of the reset switch element RT is connected to the drive unit of the imaging apparatus including the pixel unit 100 of the first embodiment, and is driven by the drive unit. When the reset switch element RT is turned on, the floating diffusion is connected to the power source (VDD) and reset. The reset switch element RT is not limited to an n-type FET, but may be another type of transistor.

  The output stage 110 is a circuit for taking out the electric charge accumulated in the floating diffusion FD to the signal readout circuit. In the first embodiment, the output stage 110 includes, for example, a transistor 110A, a selection switch SL, and a transistor 110B.

  The transistor 110A is, for example, an n-type FET, the gate is connected to the floating diffusion FD, the drain is connected to the power supply (VDD), and the source is connected to the drain of the selection switch SL. The transistor 110A amplifies the signal level input to the gate from the floating diffusion FD and outputs the amplified signal level from the source to the selection switch SL. The transistor 110A forms a so-called source follower circuit with the transistor 110B.

  The selection switch SL is, for example, an n-type FET, the drain is connected to the output terminal of the transistor 110A, and the source is connected to the output terminal 100A. The gate of the selection switch SL is connected to the drive unit of the imaging apparatus including the pixel unit 100 of Embodiment 1, and is driven by the drive unit. The transistor 110B is, for example, an n-type FET, the bias voltage Bias is input to the gate, the drain is connected to the source of the selection switch SL, and the source is grounded.

  The output terminal 100 </ b> A is an output terminal of the pixel unit 100. The output terminal 100A is connected between the source of the selection switch SL and the drain of the transistor 110B. The pixel unit 100 outputs the imaging signal accumulated in the floating diffusion FD from the output terminal 100A (as PIXEL OUT) via the output stage 110. The output terminal 100A is connected to the input terminal of the signal readout unit of the imaging apparatus including the pixel unit 100 of the first embodiment.

  FIG. 2 is a diagram illustrating the imaging apparatus 500 according to the first embodiment.

  The imaging apparatus 500 includes a complementary metal oxide semiconductor (CMOS) imaging element 200. The CMOS image sensor 200 includes a pixel unit 210, a vertical scanning circuit 220, a column parallel ADC (Analog to Digital Converter) 230, and a horizontal readout circuit 240. The imaging apparatus 500 further includes a drive unit 250 and a signal processing unit 260. The signal processing unit 260 includes a frame memory 270 and a calculation unit 280.

  In the pixel unit 210, pixels of N rows (rows) × M columns (columns) are arranged. N and M are arbitrary integers. Each pixel is provided with one pixel portion 100 shown in FIG. The vertical scanning circuit 220 is a circuit that performs vertical scanning of pixels.

  The output terminal 100A shown in FIG. 1 is connected to the input terminal of the column parallel ADC 230. The column parallel ADC 230 digitally converts the signal output from each column of the pixel unit 210 and outputs the signal. The horizontal readout circuit 240 is connected to the output side of the column parallel ADC 230 and reads out a signal digitally converted by the column parallel ADC 230.

  The drive unit 250 performs drive control by inputting control signals to the gates of the transfer gate TX, the reset switch element RT, and the selection switch SL included in the N × M pixel units 100 included in the pixel unit 210. The drive unit 250 includes a computer such as a CPU (Central Processing Unit), a microcomputer, or an FPGA (Field Programmable Gate Array).

  The signal processing unit 260 receives a signal output via the signal readout line 200A of the CMOS image sensor 200 and performs signal processing.

  The frame memory 270 stores a video signal at the time of resetting each frame of the pixel corresponding to the address specified by the driving unit 250. The frame memory 270 is only required to store a video signal at the time of resetting each frame of pixels, and for example, a volatile or nonvolatile memory may be used. The frame memory 270 is only required to store a video signal at the time of resetting each pixel for at least one frame, and may be configured to be able to store a video signal at the time of resetting each pixel for a plurality of frames.

  The calculation unit 280 calculates the first exposure data and the second exposure data based on the first video signal and the second video signal output from the signal processing unit 260 and the video signal at the time of reset stored in the frame memory 270. Output. The arithmetic unit 280 is configured by a CPU (Central Processing Unit), a computer such as a microcomputer, a sequencer, or an FPGA (Field Programmable Gate Array).

  FIG. 3 is a diagram illustrating a driving sequence of the imaging apparatus 500 according to the embodiment.

  FIG. 3 shows a case where a control signal is input to the transfer gate TX, the reset switch element RT, and the selection switch SL of the pixel unit 100 of N rows (row1, row2,..., Row N). The operation is shown for two frame periods of the first frame 1V and the second frame 2V.

  Here, each frame period includes N horizontal scanning periods (1H to NH). Further, in order to obtain exposure data of two different exposure times with the photodiode PD of each pixel, exposure is performed in two exposure periods EX_A and EX_B having different lengths.

  The exposure period EX_A is an example of a first exposure period, the exposure period EX_B is an example of a second exposure period, and the lengths of the periods are different from each other. Here, a case where the exposure period EX_A is shorter than the exposure period EX_B will be described.

  In the exposure periods EX_A and EX_B, a first video signal and a second video signal are obtained, respectively. The first video signal and the second video signal are digitally converted by the column parallel ADC 230, and the calculation is performed by the calculation unit 280 of the signal processing unit 260 through the horizontal readout circuit 240.

  The computing unit 280 outputs first exposure data and second exposure data based on the video signal at the time of reset, the first video signal, and the second video signal. The first exposure data is exposure data corresponding to the charge amount generated by exposure in the exposure period EX_A, and the second exposure data is exposure data corresponding to the charge amount generated by exposure in the exposure period EX_B.

  Since the exposure period EX_B is longer than the exposure period EX_A, the exposure time differs between the first exposure data and the second exposure data.

  Note that the exposure periods EX_A and EX_B exist alternately without interruption, and the photodiode PD always performs photoelectric conversion in either of the exposure periods.

  In FIG. 3, control signals input to the gates of the reset switch elements RT of the pixel units 100 of N rows (row1, row2,, row N) in each frame period are RT_row1, RT_row2,. It is written RT_rowN.

  Further, the control signals input to the gates of the transfer gates TX of the N row (row1, row2,, row N) pixel units 100 in each frame period are denoted as TX_row1, TX_row2,..., TX_rowN. Further, control signals input to the gates of the selection switches SL of the N row (row1, row2,, rowN) pixel units 100 in each frame period are denoted as SL_row1, SL_row2,..., SL_rowN.

  Here, since N rows (row1, row2,, row N) are driven in the N horizontal scanning periods (1H to NH), the first row row1 will be described.

  In the horizontal scanning period 1H of the first frame 1V, when the control signal SL_row1 input to the gate of the selection switch SL rises to the H level and the pixel of row 1 is selected, the control signal TX_row1 is added at the end of the exposure period EX_B. Rises to the H level in a pulse shape for a very short period (predetermined short period). As a result, the transfer gate TX is turned on, and the second video signal obtained in the exposure period EX_B of the frame immediately before the first frame 1V is output from the output terminal 100A via the floating diffusion FD.

  When the pulse of the control signal TX_row1 falls to the L level, the exposure period EX_A starts.

  In the exposure period EX_A, while the control signal SL_row1 input to the gate of the selection switch SL is rising to the H level, the control signal RT_row1 is raised in a pulse shape for a very short period (a predetermined short period). The floating diffusion FD is reset to the power supply potential VDD.

  Then, after the control signal SL_row1 input to the gate of the selection switch SL falls to the L level, the control signal TX_row1 rises in a pulse form for a very short period (a predetermined short period) at the end of the exposure period EX_A. . Accordingly, the transfer gate TX is turned on, and the first video signal obtained in the exposure period EX_A of the first frame 1V is transferred to the floating diffusion FD. Thus, the first video signal is transferred to the floating diffusion FD when the control signal SL_row1 input to the gate of the selection switch SL is outside the pixel signal readout period in which the control signal SL_row1 is at the L level.

  Then, shortly before the end of the exposure period EX_B following the exposure period EX_A, the control signal SL_row1 that enters the period of the second frame 2V and is input to the gate of the selection switch SL rises to the H level. When a pixel is selected, the first video signal obtained in the exposure period EX_A of the first frame 1V and transferred to the floating diffusion FD is output from the output terminal 100A.

  Thereafter, at the end of the exposure period EX_B, the control signal TX_row1 rises in a pulse shape for a very short period (predetermined short period) to the H level. As a result, the transfer gate TX is turned on, and the second video signal obtained in the exposure period EX_B of the first frame 1V is output from the output terminal 100A via the floating diffusion FD.

  When the exposure period EX_A is entered again, the control signal RT_row1 is pulsed for a very short period (predetermined short period) while the control signal SL_row1 input to the gate of the selection switch SL rises to the H level. The floating diffusion FD is reset to the power supply potential VDD.

  As described above, the first video signal obtained in the exposure period EX_A of the first frame 1V and the second video signal obtained in the exposure period EX_B are output from the output terminal 100A.

  4 shows the signal levels of the control signals RT_row1, TX_row1, SL_row1, the potential of the floating diffusion FD, and the output terminal 100A in the horizontal scanning period 1H of the first frame 1V and the horizontal scanning period 1H of the second frame 2V in FIG. It is a figure which shows the signal level of the video signal (PIXEL OUT) output from the.

  As shown in FIG. 4A, the video signal (PIXEL OUT) is reset before the horizontal scanning period 1H of the first frame 1V starts. At this time, the first video signal obtained in the exposure period EX_A of the frame period immediately before the first frame 1V is transferred to the floating diffusion FD.

  When the control signal SL_row1 input to the gate of the selection switch SL rises to the H level and the pixel of row 1 is selected, the exposure period EX_A of the frame period immediately before the first frame 1V is obtained. Due to the first video signal, the level of the video signal (PIXEL OUT) is lowered to S11A.

  Level S11A represents the signal level of the first video signal obtained in the exposure period EX_A of the frame period immediately before the first frame 1V.

  When the transfer gate TX is turned on, the second video signal obtained in the exposure period EX_B of the frame immediately before the first frame 1V is output from the output terminal 100A via the floating diffusion FD. Both the potential of the FD and the level of the video signal (PIXEL OUT) are lowered. At this time, the level of the video signal (PIXEL OUT) decreases to S11B.

  Level S11B represents the signal level of the second video signal obtained in the exposure period EX_B of the frame immediately before the first frame 1V.

  Then, in the exposure period EX_A of the horizontal scanning period 1H of the first frame 1V, the control signal RT_row1 is pulsed only for a very short period (predetermined short period) while the control signal SL_row1 rises to the H level. When activated, the potential of the floating diffusion FD is reset. At this time, since the selection switch SL is turned on, the level of the video signal (PIXEL OUT) changes in the same manner as the potential of the floating diffusion FD, and when the horizontal scanning period 1H of the first frame 1V ends, S21RST (Reset level). Note that the level of the video signal (PIXEL OUT) decreases after the reset level S21RST is obtained, because of the reading of the next pixel (horizontal scanning period 2H).

  Further, as shown in FIG. 4B, the pixel of row 1 is selected by entering the period of the second frame 2V and the control signal SL_row1 input to the gate of the selection switch SL rising to H level. Then, the first video signal obtained in the exposure period EX_A of the first frame 1V and transferred to the floating diffusion FD is output from the output terminal 100A. As a result, the level of the video signal (PIXEL OUT) is lowered to S21A.

  Level S21A represents the signal level of the first video signal obtained in the exposure period EX_A of the first frame 1V. Note that the reset level before falling to the level S21A in FIG. 4B is the reset level in the horizontal scanning period NH.

  When the transfer gate TX is turned on, the second video signal obtained in the exposure period EX_B of the first frame 1V is output from the output terminal 100A via the floating diffusion FD, so that the potential of the floating diffusion FD and the video signal ( Both the levels of PIXEL OUT) decrease. At this time, the level of the video signal (PIXEL OUT) decreases to S21B.

  Level S21B represents the signal level of the second video signal obtained in the exposure period EX_B of the first frame 1V.

  Then, in the exposure period EX_A of the horizontal scanning period 1H of the second frame 2V, the control signal RT_row1 is pulsed only for a very short period (predetermined short period) while the control signal SL_row1 rises to the H level. When activated, the potential of the floating diffusion FD is reset. At this time, since the selection switch SL is turned on, the level of the video signal (PIXEL OUT) transitions in the same manner as the potential of the floating diffusion FD, and when the horizontal scanning period 1H of the second frame 2V ends, S31RST (Reset level).

  As described above, the signal level S21A of the first video signal obtained in the exposure period EX_A of the first frame 1V and the signal level S21B of the second video signal obtained in the exposure period EX_B of the first frame 1V are obtained. .

Here, the reset level S21RST obtained when the horizontal scanning period 1H of the first frame 1V ends is stored in the frame memory 270. The reset level S21RST is a reset level obtained in the same pixel in the same frame as the exposure period EX_A and the exposure period EX_B for obtaining the signal level S21A and the signal level S21B, respectively.
Then, using the signal level S21A, the signal level S21B, and the reset level S21RST stored in the frame memory 270, the calculation unit 280 can calculate the first exposure data and the second exposure data.

  The first exposure data is exposure data corresponding to the charge amount generated by exposure in the exposure period EX_A, and the second exposure data is exposure data corresponding to the charge amount generated by exposure in the exposure period EX_B.

  Here, a calculation method of the first exposure data and the second exposure data will be described.

  The first exposure data S1 can be obtained by subtracting the reset level S21RST from the signal level S21A. That is, S1 = S21A-S21RST.

  The second exposure data S2 can be obtained by subtracting the signal level S21A from the signal level S21B. That is, S2 = S21B-S21A.

  Further, the total exposure data S3 of the first exposure data and the second exposure data can be obtained by subtracting the reset level S21RST from the signal level S21B. That is, S3 = S21B-S21RST. This is the sum of the first exposure data S1 and the second exposure data S2.

  As described above, if the reset level S21RST obtained when the horizontal scanning period 1H of the first frame 1V ends is stored in the frame memory 270, the first exposure data S1, the second exposure data S2, and the exposure Data S3 can be obtained.

  This is the same for all horizontal scanning periods (ie, all pixels) and the same for all frames.

  Therefore, if the data representing the address of the pixel and the reset level obtained in the same pixel in the same frame are stored in all the pixels in the frame memory 270, the first exposure data S1, Second exposure data S2 and exposure data S3 can be obtained.

  Here, the reset level obtained in the same pixel in the same frame stored in the frame memory 270 is the signal level in the pixel selected in the horizontal scanning period 1H in the first frame 1V shown in FIGS. This is a reset level obtained in the same frame as the exposure period EX_A and the exposure period EX_B for obtaining S21A and the signal level S21B, respectively.

  As described above, according to the imaging apparatus 500 of the embodiment, it is possible to perform imaging with two different exposure times.

  Here, it is desirable that the exposure period EX_A and the exposure period EX_B are shorter than the exposure period EX_B as described above. This is because if the floating diffusion FD is saturated in the exposure period EX_A in which exposure is performed first, the signal may not be read by exposure in the exposure period EX_B following the exposure period EX_A. For this reason, in the embodiment, the exposure period EX_A is set shorter than the exposure period EX_B.

  Note that the exposure period EX_A may be longer than the exposure period EX_B when there is no possibility of saturation of the floating diffusion FD.

  The reason why the reset level S21RST is used when calculating the first exposure data S1 and the exposure data S3 is to cancel the reset noise of the floating diffusion FD. This is because the floating diffusion FD may cause fluctuations in the potential after reset due to noise accompanying on / off of the reset switch element RT.

  Further, since the video signal obtained in the exposure period EX_A stays in the floating diffusion FD much longer than the video signal obtained in the exposure period EX_B, a lot of noise is mixed due to dark current generated in the floating diffusion FD. There is a risk. However, if a video signal obtained by short-time exposure in the exposure period EX_A is used on the high luminance side, the influence of noise due to dark current or the like can be reduced, and the influence can be ignored.

  In the above description, the column parallel ADC 230 is provided in the CMOS image sensor 200 in the preceding stage of the horizontal readout circuit 240. However, the ADC used instead of the column parallel ADC is outside the CMOS image sensor 200, and the horizontal The readout circuit 240 may be inside the CMOS image sensor 200.

  As described above, according to the embodiment, it is possible to provide an imaging apparatus 500 that can perform imaging with two different exposure times without complicating the structure and the manufacturing process and suppressing an increase in reading speed. Can do.

  Further, in the method of obtaining a plurality of pixel outputs having different exposure times as in Non-Patent Document 1, when there are two types of pixels having different exposure times, it is necessary to reset each of the two types of pixels. Compared with the case of obtaining a video signal of one kind of signal level in the exposure time, it is necessary to increase the reading speed more than twice.

  On the other hand, in the imaging apparatus 500 according to the embodiment, two types of video signals (first video signal and second video signal) can be obtained with respect to one reset. Compared with the case of obtaining a video signal of one kind of signal level with an exposure time of 1, it is sufficient to increase the reading speed by 1.5 times. Can do.

  Here, the mode in which the first exposure data S1 and the exposure data S3 are calculated by the calculation unit 280 using the reset level S21RST stored in the frame memory 270 has been described.

  However, instead of the reset level S21RST stored in the frame memory 270, the first exposure data S1 and the exposure data S3 are calculated using the reset level S31RST obtained when the horizontal scanning period 1H of the second frame 2V ends. May be.

  The reset level S31RST is a frame (second frame 2V) next to the same frame (first frame 1V) as the exposure period EX_A and the exposure period EX_B for obtaining the signal level S21A and the signal level S21B, respectively. The reset level obtained.

  In this case, the first exposure data S1 is obtained by S1 = S21A-S31RST, and the exposure data S3 is obtained by S3 = S21B-S31RST.

  When the reset level S31RST is used instead of the reset level S21RST stored in the frame memory 270, the reset level obtained in another frame is used, so that the reset level shifts compared to the reset level S21RST. It is not necessary to store in the frame memory 270.

  In the above description, the imaging apparatus 500 that can perform photographing with two different exposure times has been described. However, photographing may be performed with three or more different exposure times.

  The imaging device according to the exemplary embodiment of the present invention has been described above, but the present invention is not limited to the specifically disclosed embodiment, and does not depart from the scope of the claims. Various modifications and changes are possible.

DESCRIPTION OF SYMBOLS 100 Pixel part 100A Output terminal 110 Output stage 110A Transistor SL selection switch PD Photodiode TX Transfer gate FD Floating diffusion RT Reset switch element 200 CMOS image sensor 210 Pixel part 220 Vertical scanning circuit 230 Column parallel ADC
240 horizontal readout circuit 250 drive unit 260 signal processing unit 270 frame memory 280 arithmetic unit 500 imaging device

Claims (7)

A photoelectric conversion unit disposed in the pixel;
A transfer gate connected to the output terminal of the photoelectric converter;
A floating diffusion connected to the output side of the transfer gate and storing the output signal of the photoelectric conversion unit transferred via the transfer gate;
A reset switch for resetting the floating diffusion;
A selection switch connected to the floating diffusion and reading the signal;
A drive unit for driving the transfer gate, the reset switch, and the selection switch;
The drive unit is
The transfer gate is turned on at the end of the first exposure period while the reset switch and the selection switch are turned off for the first video signal obtained by photoelectric conversion in the photoelectric conversion unit in the first exposure period. By transferring from the photoelectric conversion unit to the floating diffusion,
After the first exposure period ends, the selection switch is turned on to read the first video signal from the floating diffusion,
In a state where the selection switch is on, the transfer gate is turned on at the end of the second exposure period following the first exposure period, and second obtained by photoelectric conversion in the photoelectric conversion unit in the second exposure period. Read the video signal,
An imaging apparatus that resets the floating diffusion by turning on the reset switch while the selection switch is on after reading the second video signal.   The first exposure signal in the first exposure period is obtained by subtracting the signal level after the reset of the floating diffusion of the same pixel in the same frame as the first video signal from the first video signal. Imaging device.   By subtracting the signal level after the reset of the floating diffusion of the same pixel in the same frame as the second video signal from the second video signal, an exposure signal by the exposure in the first exposure period and the second exposure period is obtained. The imaging device according to claim 1 or 2.   By subtracting the signal level after the reset of the floating diffusion of the same pixel in the next frame of the same frame as the first video signal from the first video signal, a first exposure signal in the first exposure period is obtained. The imaging device according to claim 1.   By subtracting the reset signal level of the floating diffusion of the same pixel in the next frame of the same frame as the second video signal from the second video signal, exposure in the first exposure period and the second exposure period The imaging apparatus according to claim 1, wherein an exposure signal is obtained.   6. The imaging apparatus according to claim 1, wherein a second exposure signal obtained by exposure in the second exposure period is obtained by subtracting the first video signal from the second video signal. 7.   The imaging apparatus according to claim 1, wherein the first exposure period is shorter than the second exposure period.

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