JP5019705B2 - Solid-state imaging device and driving method of solid-state imaging device - Google Patents

Description

  The present invention relates to a solid-state imaging device, and more particularly to an amplification type solid-state imaging device including a unit pixel having an amplification function and a driving method thereof.

  In recent years, amplification-type solid-state imaging devices represented by CMOS image sensors have been actively developed. In this type of solid-state imaging device (see, for example, Patent Document 1), the power supply voltage is lowered as the MOS design rule is reduced. As a result, the reset voltage when resetting the potential of the floating diffusion is lowered. It has become to. Originally, in a solid-state imaging device, it is advantageous to perform signal amplification before signal processing in order to improve the SN ratio. Therefore, in order to improve the S / N ratio, it is desired to increase the conversion efficiency when converting the signal charge into the signal voltage by reducing the capacity of the floating diffusion.

JP 2001-69408 A

  However, when the conversion efficiency of the floating diffusion increases (when the capacity of the floating diffusion decreases), the imaging sensitivity (sensor sensitivity) increases accordingly. For example, when strong light enters the imaging surface of the solid-state imaging device As a result, there arises a problem that the signal charges accumulated in the photoelectric conversion unit cannot be transferred to the floating diffusion. Even if the signal charge is successfully transferred from the photoelectric conversion unit to the floating diffusion, if the amplification transistor is operated as a source follower, the voltage applied to the gate of the amplification transistor becomes excessively low. Therefore, a sufficient voltage is not applied to the drain of the constant current source installed on the source side of the amplification transistor, the constant current source cannot operate well, and the linearity of the source follower is deteriorated. appear. Further, as a countermeasure against this, if the saturation signal amount in the photoelectric conversion unit is reduced, it becomes impossible to ensure the contrast of the portion with high luminance. Therefore, conventionally, it has been difficult to simultaneously improve the SN ratio and expand the dynamic range.

The solid-state imaging device according to the present invention includes a photoelectric conversion unit that photoelectrically converts incident light to accumulate signal charges, a transfer unit that transfers signal charges accumulated in the photoelectric conversion unit, and a transfer unit that transfers the signal charges. When the signal voltage converted from the signal charge to the signal voltage and the signal voltage converted by the charge voltage converter are read, the conversion efficiency of the charge voltage converter is higher than the first conversion efficiency or the first conversion efficiency. When reading the signal voltage converted by the control unit variably controlled to the second conversion efficiency and the charge-voltage conversion unit, the conversion efficiency of the charge-voltage conversion unit becomes the value of the first conversion efficiency and the second conversion efficiency. The read control unit that reads out the first signal voltage and the second signal voltage obtained in the set state is compared with the second signal voltage and a predetermined threshold level that is set in advance, and based on the comparison result , reading from the read control unit Is provided with a first signal voltage and an output processing unit that selects a signal voltage finally output from the second signal voltage, the control unit includes a capacitor connected to the charge-voltage converter, the voltage on capacitor A voltage application control unit that applies and controls the applied voltage, and has a reset element that resets the electric potential of the charge voltage conversion unit, and voltage application while maintaining the power supply voltage applied to the reset element in an on state. In a state where the voltage applied to the capacitor is set to a relatively low voltage by the control unit, the potential of the charge voltage conversion unit is reset by the reset element, and after the reset by the reset element, the power supply voltage applied to the reset element is turned on. While maintaining the voltage applied to the capacitor by the voltage application controller, the signal charge is transferred to the charge voltage converter by the transfer unit. Is shall.

  In the solid-state imaging device according to the present invention, when the signal charge accumulated in the photoelectric conversion unit is transferred to the charge voltage conversion unit by the transfer unit, the conversion efficiency of the charge voltage conversion unit is variably controlled by the control unit, It becomes possible to read out the signal voltage corresponding to the signal charge transferred from the photoelectric conversion unit to the charge voltage conversion unit while changing the conversion efficiency of the charge voltage conversion unit.

  According to the present invention, the signal voltage corresponding to the signal charge transferred from the photoelectric conversion unit to the charge-voltage conversion unit can be read by changing the conversion efficiency of the charge-voltage conversion unit. As a result, when the amount of incident light is small, the signal voltage is read with the conversion efficiency of the charge voltage conversion unit relatively high, and when the amount of incident light is large, the conversion efficiency of the charge voltage conversion unit is relatively By reading the signal voltage in a low state, imaging can be performed with appropriate sensitivity in any case, and a wider range of light intensity can be expressed within the same output voltage range. Therefore, the improvement of the SN ratio and the expansion of the dynamic range can be realized at the same time.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram illustrating a configuration example of a solid-state imaging device according to an embodiment of the present invention. The illustrated solid-state imaging device constitutes, for example, a CMOS image sensor, and includes an imaging region 2 in which a plurality of pixels 1 are arranged in a two-dimensional matrix, a vertical selection drive circuit 3, a column signal processing unit 4, The configuration includes a horizontal scanning circuit 5, a timing generator 6, and an output processing unit 8 that processes a signal output to the horizontal signal line 7.

  The configuration of the pixel 1 will be described in detail later. In the imaging region 2, a plurality of vertical signal lines (not shown) for reading out the signal of each pixel 1 in the vertical direction are formed together with the plurality of pixels 1. The vertical selection drive circuit 3 selects and drives each pixel 1 in the imaging region 2 row by row. A signal of each pixel 1 in the imaging region 2 is taken into the column signal processing unit 4 through a vertical signal line (not shown) formed for each column. The column signal processing unit 4 processes the signal of each pixel 1 taken in through the vertical signal line, and is configured using, for example, a load MOS transistor and a sample hold / CDS (Correlated Double Sampling) circuit. The sample and hold / CDS circuit is provided in parallel with the vertical signal line 18, and samples and holds signals for one row, performs CDS processing, and holds them in the form of electric charges.

  The horizontal scanning circuit 5 selectively scans the signal of each pixel 1 read through the vertical signal line of each column and processed by the column signal processing unit 4 in order in the horizontal direction and guides it to the horizontal signal line 7. . The horizontal scanning circuit 5 is configured using, for example, a plurality of selection transistors connected to the vertical signal lines of each column and a shift circuit that sequentially turns on the plurality of selection transistors in the horizontal direction. The timing generator 6 supplies various pulse signals necessary for the operation of each unit to the vertical selection drive circuit 3, the column signal processing unit 4, and the horizontal scanning circuit 5 based on a reference clock having a predetermined period. The output processing unit 8 performs output processing of the pixel signal read to the horizontal signal line 7 by the horizontal scanning circuit 5. This output processing includes pixel signal amplification processing, selection processing, AGC (Auto Gain Control) processing, A / D (analog / digital) conversion processing, and the like. Among these, pixel signal selection processing will be described in detail later.

  FIG. 2 is a diagram illustrating a configuration example of a pixel of the solid-state imaging device according to the embodiment of the present invention. The illustrated pixel (unit pixel) 1 generally includes a photodiode PD serving as a photoelectric conversion unit, a transfer transistor 11 serving as a transfer unit, a floating diffusion FD serving as a charge-voltage conversion unit, a reset transistor 12, and an amplification transistor. 13 and a MOS capacitor 14.

  The photodiode PD converts incident light incident on the photodiode PD into a signal charge by photoelectric conversion, and accumulates the signal charge. The transfer transistor 11 transfers the signal charge accumulated in the photodiode PD to the floating diffusion FD. The floating diffusion FD converts the signal charge transferred from the photodiode PD by the transfer transistor 11 into a signal voltage. The reset transistor 12 resets the potential of the floating diffusion FD to a certain level. The amplification transistor 13 amplifies and outputs the signal voltage of the floating diffusion FD.

  The MOS capacitor 14 is connected to the floating diffusion FD in order to vary the capacitance (junction capacitance) of the floating diffusion FD. The voltage control unit 15 applies a voltage to the MOS capacitor 5 and variably controls the applied voltage. The voltage control unit 15 may be provided in the vertical selection drive circuit 3 or may be provided separately from the vertical selection drive circuit 4. In the present embodiment, it is assumed that the voltage control unit 15 is provided in the vertical selection drive circuit 3. The voltage control unit 15 is configured using, for example, a voltage generation unit that generates a constant voltage and a voltage application unit that applies the voltage generated by the voltage generation unit to the MOS capacitor 14. Moreover, the voltage control part 15 is provided with a voltage adjustment part as needed. The voltage adjusting unit adjusts the voltage level when the voltage generated by the voltage generating unit is applied to the MOS capacitor 5 by the voltage applying unit.

  The gate electrode of the transfer transistor 11 is connected to the transfer signal line 16, the gate electrode of the reset transistor 12 is connected to the reset line 17, and the gate electrode of the amplification transistor 13 is connected to the floating diffusion FD. Further, a common power supply voltage VDD is applied to each of the reset transistor 12 and the amplifying transistor 13. The amplification transistor 13 operates as a load MOS transistor 19 connected to the vertical signal line 18 and a source follower circuit. The output voltage of the amplification transistor 13 is taken into the CDS circuit 20 through the vertical signal line 18 and then input to the signal amount determination circuit 21. The load MOS transistor 19 and the CDS circuit 20 are included in the column signal processing unit 4 described above. The signal amount determination circuit 21 is included in the output processing unit 8 described above.

  In the pixel 1 having the above configuration, signal charges are accumulated in the photodiode PD during a predetermined accumulation (exposure) period, and a reset pulse φRST is applied to the gate electrode of the reset transistor 12 through the reset line 17 at the end of the accumulation period. To do. As a result, the potential of the floating diffusion FD is reset to a constant level (reset signal level) corresponding to the power supply voltage VDD. Thereafter, a transfer pulse φTRF is applied to the gate electrode of the transfer transistor 11 through the transfer signal line 16. As a result, signal charges accumulated in the photodiode PD within the accumulation period are transferred from the photodiode PD to the floating diffusion FD. At this time, in the floating diffusion FD, the signal charge transferred from the photodiode PD is converted into a signal voltage corresponding to the charge amount (potential change) at that time. The signal voltage thus converted by the floating diffusion FD is amplified by the amplification transistor 4 and output to the vertical signal line 18.

  In general, the conversion efficiency η when converting a signal charge into a signal voltage by the floating diffusion FD is approximately expressed by the equation “η = q / CFD [μV / e]”. q is the charge amount of one electron, and CFD is the capacity of the floating diffusion. As can be seen from this equation, the conversion efficiency η of the floating diffusion FD in the pixel 1 is determined by the capacitance CFD of the floating diffusion. Further, the capacitance CFD of the floating diffusion changes according to a voltage (hereinafter also referred to as “capacitor voltage”) Vcap applied to the MOS capacitor 14. That is, when the capacitor voltage Vcap is increased, the capacitance CFD of the floating diffusion is increased accordingly, and when the capacitor voltage Vcap is decreased, the capacitance CFD of the floating diffusion is decreased accordingly.

  Therefore, the following relationship is established between the voltage Vcap applied to the MOS capacitor 5 and the conversion efficiency η of the floating diffusion FD. That is, when the capacitor voltage Vcap is increased, the capacitance CFD of the floating diffusion increases accordingly, so that the conversion efficiency η of the floating diffusion FD decreases. Conversely, when the capacitor voltage Vcap is lowered, the capacitance CFD of the floating diffusion is reduced accordingly, and the conversion efficiency η of the floating diffusion FD is increased. Therefore, the pixel 1 has a configuration in which the voltage Ccap applied to the MOS capacitor 14 is changed by the voltage control unit 15 so that the capacitance CFD of the floating diffusion FD and the conversion efficiency η depending thereon can be variably controlled. ing. In this example, the voltage Vcap applied to the MOS capacitor 14 is variably controlled by the voltage control unit 15 in two stages of on / off.

  Further, a CDS circuit 20 that performs CDS (Correlated Double Sampling) processing is connected to the vertical signal line 18. The signal voltage amplified and output to the vertical signal line 18 by the amplification transistor 13 is input to the CDS circuit 20 where the fixed pattern noise of the pixel is removed.

  FIG. 3 is a timing chart showing a driving method of the solid-state imaging device according to the embodiment of the present invention. In the figure, the power supply voltage VDD, the reset pulse φRST, the transfer pulse φTRF, and the Vcap application pulse are all controlled by the vertical selection drive circuit 3 based on the pulse signal supplied from the timing generator 6 to the vertical selection drive circuit 3. Is.

  First, the reset pulse φRST is turned on while the power supply voltage VDD is kept on (high). At this time, both the transfer pulse φTRF and the capacitor voltage Vcap are held in an off (low) state. Next, after the reset pulse φRST is turned off, the capacitor voltage Vcap and the transfer pulse φTRF are sequentially turned on. Next, the transfer pulse φTRF and the capacitor voltage Vcap are sequentially turned off. As a result, the transfer pulse φTRF is held in the on state for a part of the period during which the capacitor voltage Vcap is held in the on state.

  Thereafter, the reset pulse φRST is held in the on state, and the power supply voltage VDD is switched from the on state to the off state within this holding period. Next, the reset pulse φRST is switched from the on state to the off state within the period in which the power supply voltage VDD is held in the off state, and then the power supply voltage VDD is switched from the off state to the on state again. Incidentally, the conversion efficiency of the floating diffusion FD is converted according to the on / off state of the capacitor voltage Vcap. That is, when the capacitor voltage Vcap is off, the conversion efficiency of the floating diffusion FD is relatively high, and when the capacitor voltage Vcap is off, the conversion efficiency of the floating diffusion FD is relatively low.

  In the above driving method, the column signal processing unit 4 serving as a reading control unit performs reading of the reset signal and reading of the pixel signal from the pixel 1 in the following procedure. First, the first reset signal is read at an arbitrary timing within a period from when the reset signal φRST is first turned on / off to when the capacitor voltage Vcap is turned on, for example, at timing T1 shown in FIG. Next, the second reset signal is read at an arbitrary timing within a period from when the capacitor voltage Vcap is turned on to when the transfer pulse φTRF is turned on, for example, at timing T2 shown in FIG.

  Subsequently, the first pixel signal is read at an arbitrary timing within a period from when the transfer pulse φTRF is turned off to when the capacitor voltage Vcap is turned off, for example, timing T3 shown in FIG. Next, a second pixel signal is read at an arbitrary timing within a period from turning off the capacitor voltage Vcap to turning on the reset pulse φRST, for example, at a timing T4 shown in FIG.

  Here, at the timing T1 at which the reset signal is read for the first time, both the transfer pulse φTRF and the capacitor voltage Vcap are in the off state. As shown in FIG. 4A, the potential of the floating diffusion FD portion formed over 12G is between the end portion of the gate electrode 11G of the transfer transistor 11 and the end portion of the gate electrode 12G of the reset transistor 12 opposed thereto. The voltage level is partially lowered, and the potential level is lower than the power supply voltage VDD by Vfs1 due to the influence of the feedthrough of the reset transistor 12. Therefore, at the timing T1, the first reset signal is read at the level of “VDD + Vfs1”.

  Next, since the capacitor voltage Vcap is in the on state at the timing T2 at which the reset signal is read for the second time, the potential of the floating diffusion FD portion is equal to that of the transfer transistor 11 as shown in FIG. The state is uniformly lowered from the end of the gate electrode 11G to the gate electrode 12G of the reset transistor 12, and the potential level is reset by the coupling between the gate of the floating diffusion control transistor and the floating diffusion FD. It is lower by “Vfs2” than when reading a signal. Therefore, at the timing T2, the second reset signal is read at the level of “VDD + Vfs1 + Vfs2”.

  Next, by turning on the transfer pulse φTRF, the potential potential below the gate electrode 11G of the transfer transistor 11 is lowered as shown in FIG. Therefore, the signal charge accumulated in the photodiode PD between the time when the reset pulse φRST is turned on and off and the time when the transfer pulse φTRF is turned on (within the exposure period) is transferred to the floating diffusion FD through the gate electrode 11G of the transfer transistor 11. Is done.

  Therefore, at the timing T3 at which the transfer pulse φTRF is turned off after the signal charge transfer (transfer to the floating diffusion FD) and the first pixel signal is read, the capacitor voltage is the same as the second reset signal read. Vcap is on. Therefore, the potential of the floating diffusion FD portion is uniformly low from the end of the gate electrode 11 of the transfer transistor 11 to the gate electrode 12G of the reset transistor 12 as shown in FIG. Due to the transfer of the signal charge to the floating diffusion FD, the level becomes higher by “Q / C1” than when the second reset signal is read. Therefore, at the timing T3, the first pixel signal is read at the level of “VDD + Vfs1 + Vfs2-Q / C1”. Incidentally, Q is the amount of signal charge transferred from the photodiode PD to the floating diffusion FD, and C1 is the capacitance of the floating diffusion FD at the time of reading the first pixel signal.

  Thereafter, at the timing T4 when the pixel signal is read for the second time, the capacitor voltage Vcap is in an off state as in the case of reading the reset signal for the first time. Therefore, the potential of the floating diffusion FD portion is shown in FIG. As shown in the figure, the state is partially lowered between the end of the gate electrode 11G of the transfer transistor 11 and the end of the gate electrode 12G of the reset transistor 12 opposed thereto, and the potential level thereof is the second reset signal. It is higher by “Q / C2” than at the time of reading. Therefore, at the timing T4, the second pixel signal is read out at the level of “VDD + Vfs1 + Vfs2-Q / C2”. Incidentally, C2 is the capacitance of the floating diffusion FD at the time of reading the pixel signal for the second time, and takes a value smaller than C1.

  By reading out the reset signal and the pixel signal from each pixel 1 a plurality of times (in this example, twice) in the above procedure, the CDS circuit 20 reads out the signals at the respective timings T1, T2, T3, and T4. The received signals (reset signal, pixel signal) are taken in order. At that time, the CDS circuit 20 reduces the noise by calculating the difference between the pixel signal read at the timing T4 and the reset signal read at the timing T1, and the capacitor voltage Vcap is turned off (floating diffusion FD). The differential signal (hereinafter also referred to as “high sensitivity signal”) is output when the conversion efficiency of the signal is relatively low. Also, the CDS circuit 20 reduces the noise by calculating the difference between the pixel signal read at the timing T3 and the reset signal read at the timing T2, and the capacitor voltage Vcap is turned on (of the floating diffusion FD). A differential signal (hereinafter also referred to as “low sensitivity signal”) when the conversion efficiency is relatively high) is output.

  Therefore, when viewed from the relationship between the signal charge amount at the photodiode PD and the signal output at the output processing unit 8, as shown in FIG. 7, the high-sensitivity signal is in a state in which the conversion efficiency of the floating diffusion FD is increased ( The pixel signal obtained in a state where the imaging sensitivity is increased) and the low sensitivity signal is a pixel signal obtained in a state where the conversion efficiency of the floating diffusion FD is lowered (a state where the imaging sensitivity is lowered).

  The two pixel signals (high sensitivity signal and low sensitivity signal) obtained by changing the conversion efficiency of the floating diffusion FD in this way are selected by the output processing unit 8 and only one of the pixel signals is selected to be finally obtained. Extracted as signal output. As a specific pixel signal selection method, a method using a threshold can be employed. For example, the output processing unit 8 sets a certain signal output level as a threshold level, and the signal level determination circuit 21 provided as one of the signal selection processing functions in the output processing unit 8 determines the output level of the high sensitivity signal. The magnitude relation with the threshold level is compared and determined. If it is determined that the output level of the high sensitivity signal is equal to or lower than the threshold level, the high sensitivity signal is selected as the final signal output, and it is determined that the output level of the high sensitivity signal exceeds the threshold level. In this case, the low sensitivity signal is selected as the final signal output.

  In this case, the threshold value needs to be set to an optimum value in accordance with the fluctuation range of the voltage of the floating diffusion FD and the γ correction in the signal processing at the subsequent stage. The fluctuation range of the voltage of the floating diffusion FD is controlled by the set voltage of the capacitor voltage Vcap applied to the MOS capacitor 14. For this reason, the voltage control unit 15 is configured so that the capacitor voltage Vcap can take three or more values (for example, 0, low voltage, medium voltage, high voltage, etc.), and can be flexibly applied to subsequent signal processing whose specifications are unknown. It is desirable to be able to respond.

  As a result, when the amount of light incident on the photodiode PD is small (when the amount of signal charge accumulated in the photodiode PD is small), it is output from the CDS circuit 20 and read by the horizontal scanning circuit 5 to the horizontal signal line 7. By adopting (selecting) the output high-sensitivity signal as the final pixel signal (effective pixel signal) in the output processing unit 8, the subject can be imaged with high sensitivity suitable for dark imaging conditions. When the amount of light incident on the photodiode PD is large (when the amount of signal charge accumulated in the photodiode PD is large), the output processing unit 8 outputs the signal from the CDS circuit 20 and the horizontal scanning circuit 5 performs horizontal scanning. By adopting (selecting) the low sensitivity signal read out to the signal line 7 as the final pixel signal (effective pixel signal) in the output processing unit 8, the subject is imaged with low sensitivity suitable for bright shooting conditions. be able to. Therefore, since it is possible to pick up an image with appropriate sensitivity for both weak incident light and strong incident light, the signal-to-noise ratio of the signal can be improved.

  Further, even if the saturation signal amount in the photodiode PD is increased, the signal charge can be reliably transferred by ensuring that the capacitance of the floating diffusion FD is large by turning on the capacitor voltage Vcap during charge transfer. Become. Therefore, the operating point of the source follower can be set to a high voltage value, and the linearity of the output signal can be improved. Further, since a wider range of light quantity can be expressed within the same output voltage range, the dynamic range of the solid-state imaging device can be expanded. From the above, it is possible to simultaneously improve the SN ratio and expand the dynamic range.

  Further, when the potential of the floating diffusion FD is reset by the reset transistor 12, the voltage controller 15 turns off the capacitor voltage Vcap and turns on the reset pulse φRST under this off state. Since the potential of the floating diffusion FD is reset, when the capacitor voltage Vcap is switched from the off state to the on (relatively high) state after the reset, the potential of the floating diffusion FD is higher (deep). Can be reset to state.

  Further, after resetting by the reset transistor 12, the voltage controller 15 turns on the capacitor voltage Vcap (a relatively high state), and the transfer pulse φTRF is turned on under this on state, whereby the signal of the photodiode PD Since the charge is transferred to the floating diffusion FD by the transfer transistor 11, it is possible to efficiently and reliably transfer the signal charge to the floating diffusion FD while suppressing the backflow of the signal charge to the photodiode PD. it can.

  In the above embodiment, the reset signal and the pixel signal are read twice each while changing the conversion efficiency of the floating diffusion FD. However, the present invention is not limited to this. In a shooting environment brighter than a certain reference value, the conversion efficiency of the floating diffusion FD is set to a relatively low state, and the reset signal and the pixel signal are read once each. In a dark photographing environment less than the reference value, the conversion efficiency of the floating diffusion FD may be set to a relatively high state, and the reset signal and the pixel signal may be read once. When a bright part and a dark part coexist in one field of view, the reset signal and the pixel signal may be read by changing the setting of the conversion efficiency of the floating diffusion FD in each part.

It is the schematic which shows the structural example of the solid-state imaging device which concerns on embodiment of this invention. It is a figure which shows the structural example of the pixel of the solid-state imaging device which concerns on embodiment of this invention. 3 is a timing chart illustrating a method for driving the solid-state imaging device according to the embodiment of the present invention. FIG. 4 is a diagram for explaining a signal reading operation based on the timing chart of FIG. 3 (part 1); FIG. 4 is a diagram for explaining a signal reading operation based on the timing chart of FIG. 3 (part 2); FIG. 6 is a diagram for explaining a signal reading operation based on the timing chart of FIG. 3 (part 3); It is a figure which shows the relationship between the signal charge amount in a photodiode, and the signal output in an output process part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pixel, 2 ... Imaging region, 3 ... Vertical selection drive circuit, 4 ... Column signal processing part, 5 ... Horizontal scanning circuit, 6 ... Timing generator, 7 ... Horizontal signal line, 8 ... Output processing part, 11 ... Transfer transistor , 12 ... Reset transistor, 13 ... Amplification transistor, 14 ... MOS capacitor, 15 ... Voltage controller, 20 ... CDS circuit, 21 ... Signal amount determination circuit, FD ... Floating diffusion, PD ... Photodiode

Claims (2)

A photoelectric conversion unit that photoelectrically converts incident light and accumulates signal charges;
A transfer unit that transfers the signal charges accumulated in the photoelectric conversion unit;
A charge-voltage converter that converts the signal charge transferred by the transfer unit into a signal voltage;
A control unit that variably controls the conversion efficiency of the charge voltage conversion unit to the first conversion efficiency or the second conversion efficiency higher than the first conversion efficiency when reading the signal voltage converted by the charge voltage conversion unit When,
When the signal voltage converted by the charge-voltage converter is read, the conversion efficiency of the charge-voltage converter is obtained in a state where the conversion efficiency is set to the values of the first conversion efficiency and the second conversion efficiency , respectively . A read controller that reads the signal voltage of 1 and the second signal voltage;
The second signal voltage is compared with a predetermined threshold level set in advance, and based on the comparison result, the first signal voltage and the second signal voltage read from the read control unit are compared. An output processing unit for selecting a signal voltage to be finally output,
The controller includes a capacitor connected to the charge-voltage converter, and a voltage application controller that applies a voltage to the capacitor and controls the applied voltage.
A reset element for resetting the potential of the charge-voltage converter,
While maintaining the power supply voltage applied to the reset element in the ON state, the voltage application control unit sets the voltage applied to the capacitor to a relatively low voltage, and the reset element causes the charge voltage conversion unit to Reset the potential,
After the reset by the reset element, the transfer unit in a state where the voltage applied to the capacitor is set to a relatively high voltage by the voltage application control unit while maintaining the power supply voltage applied to the reset element in an on state. A solid-state imaging device that transfers the signal charge to the charge-voltage converter. A photoelectric conversion unit that photoelectrically converts incident light to accumulate signal charges, a transfer unit that transfers the signal charges stored in the photoelectric conversion unit, and a signal voltage that is transferred by the transfer unit to a signal voltage A charge voltage conversion unit that controls the conversion efficiency of the charge voltage conversion unit when reading the signal voltage converted by the charge voltage conversion unit, and the signal voltage converted by the charge voltage conversion unit. A method for driving a solid-state imaging device, comprising: a readout control unit that reads out; and an output processing unit that selects a signal voltage that is finally output based on the signal voltage read out from the readout control unit,
A transfer step of transferring the signal charge accumulated in the photoelectric conversion unit to the charge voltage conversion unit by the transfer unit while maintaining the power supply voltage applied to the solid-state imaging device in an on state;
After the transfer step, while maintaining the power supply voltage applied to the solid-state imaging device in the ON state, the charge voltage in the state where the conversion efficiency of the charge voltage conversion unit is set to the first conversion efficiency by the control unit A first pixel signal readout step of reading out the pixel signal level of the conversion unit by the readout control unit;
After the first pixel signal readout step, the control unit causes the charge voltage conversion unit to have a higher conversion efficiency than the first conversion efficiency while maintaining the power supply voltage applied to the solid-state imaging device in an on state. A second pixel signal readout step of reading out the pixel signal level of the charge-voltage conversion unit by the readout control unit in a state where the conversion efficiency is set to 2.
The output processing unit compares the pixel signal level read in the second pixel signal reading step with a predetermined threshold level set in advance, and based on the comparison result, in the first pixel signal reading step A selection step of selecting one of the read pixel signal level and the pixel signal level read in the second pixel signal read step as a pixel signal level to be finally output;
Before the transfer step, the charge voltage conversion unit is set in the state where the conversion efficiency of the charge voltage conversion unit is set to the second conversion efficiency while holding the power supply voltage applied to the solid-state imaging device in the ON state. A first reset signal reading step of reading the reset signal level of
After the first reset signal readout step and before the transfer step, the conversion efficiency of the charge voltage conversion unit is changed to the first conversion while maintaining the power supply voltage applied to the solid-state imaging device in the on state. A second reset signal reading step of reading a reset signal level of the charge-voltage converter in a state where the efficiency is set;
A method for driving a solid-state imaging device.

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