JP2008092477A - Photo-electric conversion device, its control method and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extendnd a dynamic range in a pixel structure where an accumulation unit for temporarily accumulating electric charges accumulated in a photo-electric conversion element is shared for a plurality of pixels. <P>SOLUTION: In the photo-electric conversion device 101, a control unit 14 performs control in first operation for discharging surplus electric charges to a floating diffusion FD in a case where the amount of accumulated charges in a first photo-diode PD 1 exceeds a saturation charge amount, and performs control in second operation for discharging the surplus electric charges to an electric charge discharging area in a case where the amount of accumulated charges in a second photo-diode PD 2 exceeds the saturation charge amount. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion device, a control method thereof, and an imaging device.

  Conventionally, many proposals have been made as methods for expanding the dynamic range of an image sensor.

  Patent Document 1 discloses a technique for outputting a signal corresponding to the logarithm of light incident on a photodiode (hereinafter referred to as “PD”).

  Patent Document 2 discloses a technique for expanding the dynamic range by performing photoelectric conversion in both PD and floating diffusion (hereinafter referred to as “FD”).

  Patent Document 3 discloses a technique for expanding the dynamic range by transferring the charge generated in the PD to the FD a plurality of times.

  In the image sensor, when the signal charge accumulated in the PD exceeds the saturation signal amount, it may leak into a low potential barrier. This is shown in FIG. FIG. 12 shows the cross-sectional structure of each part in the upper part, and shows the potential distribution in the lower part. The vertical axis of the potential distribution represents the surface potential of the semiconductor substrate under the insulating film. The horizontal position of the potential distribution shown in the lower part corresponds to the horizontal position of the cross-sectional structure shown in the upper part. 3, 5 and 13 described later are also illustrated in the same manner. As shown in FIG. 12A, the signal charge generated in the PD is accumulated in the parasitic capacitance of the PD. When the signal charge accumulated in the parasitic capacitance of the PD exceeds the saturation signal amount, it leaks into the FD beyond the potential barrier of the transfer switch TX as shown in FIG.

  Patent Document 4 discloses a technique for expanding the dynamic range by adding the signal charge leaked into the FD and the signal charge generated by the PD using the phenomenon shown in FIG.

In recent image pickup devices, in order to reduce the size of pixels, it has been attempted to reduce the pixel pitch by sharing a circuit (signal reading circuit) that reads a PD signal arranged in a pixel with a plurality of PDs. ing.
JP-A-11-313257 JP 2000-59688 A JP 2001-177775 A JP 2003-87665 A

  However, in a pixel structure sharing a signal readout circuit, it is extremely difficult to apply a method of capturing a surplus charge generated in a PD with an FD and expanding a dynamic range. Hereinafter, this state will be described with reference to FIGS. 13 and 14.

  FIG. 13 shows the cross-sectional structure of each part in the upper part and shows the potential distribution in the lower part. FIG. 14 is a diagram showing the relationship between the accumulated charge amount of each part and the exposure time. In FIG. 14, the horizontal axis represents time, and the vertical axis represents the amount of charge. 13A shows the state of the pixel at time t51 in FIG. 14, FIG. 13B shows the state of the pixel at time t52 in FIG. 14, FIG. 13C shows the state of the pixel at time t53 in FIG. (D) corresponds to the state of the pixel at time t54 in FIG. 14A shows the relationship between the accumulated charge amount of PD1 and the exposure time, FIG. 14B shows the relationship between the accumulated charge amount of PD2 and the exposure time, and FIG. 14C shows the accumulated charge amount of FD. The relationship with the exposure time is shown respectively. Here, of the two PDs sharing the signal readout circuit, the PD read first is PD1, and the PD read later is PD2. Further, it is assumed that PD1 is a pixel having a color filter with higher sensitivity than PD2.

  At time t51 (corresponding to FIG. 13A), PD1, PD2 and FD are reset, and signal charge accumulation is started.

  At time t52 (corresponding to FIG. 13B), signal charges are accumulated in PD1 and PD2.

  At time t53 (corresponding to FIG. 13C), the accumulated charge amount of PD1 exceeds the saturation charge amount. In PD1, since the potential barrier on the transfer switch TX1 side is the lowest, the signal charge generated in PD1 leaks to the FD.

  At time t54 (corresponding to FIG. 13D), the accumulated charge amount in PD1 and PD2 exceeds the saturation charge amount. In PD2, the potential barrier on the transfer switch TX2 side is the lowest. For this reason, surplus charges larger than the saturation charge amount of PD1 and surplus charges larger than the saturation charge of PD2 both leak into the FD, and the signal charges of PD1 and PD2 coexist in the FD.

  As described above, when signal charges leak into the FD from a plurality of pixels sharing the FD, the signal charges leaked from the PDs of both pixels are mixed. For this reason, in an image pickup device in which color filters are regularly arranged, information on adjacent pixels having other color filters is mixed, resulting in a signal different from a signal that should be originally obtained. As a result, in an imaging device having a pixel configuration that shares an FD, it is extremely difficult to expand the dynamic range by capturing surplus charges generated in the PD with the FD.

  The present invention has been made in view of the above problems, and in a pixel structure in which a storage unit for temporarily storing charges stored in a photoelectric conversion element is shared by a plurality of pixels, the dynamic range is expanded. Objective.

  According to a first aspect of the present invention, a first photoelectric conversion element and a second photoelectric conversion element that photoelectrically convert light into electric charges, and electric charges accumulated in the first and second photoelectric conversion elements are temporarily stored. A photoelectric conversion device in which a pixel having a storage unit for storing and an output unit for converting the charge transferred from the first and second photoelectric conversion elements to the storage unit and outputting the voltage is arranged in a two-dimensional array Therefore, when the accumulated charge amount of the first photoelectric conversion element exceeds the saturation charge amount, control is performed by the first operation of discharging the surplus charge to the accumulation unit, and the second photoelectric conversion element of the second photoelectric conversion element is controlled. When the accumulated charge amount exceeds the saturated charge amount, a control unit is provided that performs control in the second operation of discharging the surplus charge to the charge discharge region.

  A second aspect of the present invention relates to an imaging apparatus, and includes an optical system and the photoelectric conversion device.

  According to a third aspect of the present invention, a first photoelectric conversion element and a second photoelectric conversion element that photoelectrically convert light into electric charges, and electric charges accumulated in the first and second photoelectric conversion elements are temporarily stored. A photoelectric conversion device in which pixels having an accumulation unit for storing and an output unit for converting the electric charge transferred from the first and second photoelectric conversion elements to the accumulation unit and outputting the voltage are two-dimensionally arranged In the control method, when the accumulated charge amount of the first photoelectric conversion element exceeds the saturation charge amount, the surplus charge is discharged to the accumulation unit, and the accumulated charge amount of the second photoelectric conversion element is When the saturation charge amount is exceeded, control is performed by the second operation of discharging the surplus charge to the charge discharge region.

  ADVANTAGE OF THE INVENTION According to this invention, a dynamic range can be expanded in the pixel structure which shares the storage part which accumulate | stores the electric charge accumulate | stored in the photoelectric conversion element temporarily with several pixels.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of an imaging unit 100 according to a preferred embodiment of the present invention. In the photoelectric conversion device 101, a plurality of pixels are arranged in the vertical direction and the horizontal direction of the imaging surface. The vertical selection unit 102 outputs a control pulse for reading an electrical signal from the pixel for each of the row selection lines VSEL1 to VSELm. The electric signals of the respective pixels selected by the row selection lines VSEL1 to VSELm are selected by the control pulses of the column selection lines VSIG1 to VSIGm applied by the horizontal selection unit 104. The CDS circuit 103 performs CDS (Correlated Double Sampling) processing on the output signals of the pixels selected by the control pulses of the column selection lines VSIG1 to VSIGm. Signals processed by the CDS circuit 103 are sequentially output from the output line 105.

  FIG. 2 is a diagram showing details of pixels arranged in the photoelectric conversion device 101 of FIG. Reference numeral 201 denotes two pixels sharing a signal readout circuit. PD1 and PD2 are photodiodes (hereinafter referred to as “PD”) that convert light into electric charges. TX1 and TX2 are transfer switches that are driven by transfer pulses ΦTX1 and ΦTX2, respectively, and transfer charges generated in PD1 and PD2 to the FD, respectively.

  The FD is an accumulation unit (floating diffusion) that temporarily accumulates charges. Reference numeral 207 denotes an amplification MOS amplifier that functions as a source follower. Reference numeral 208 denotes a selection switch that selects a pixel by a vertical selection pulse ΦSEL. A reset switch 209 removes charges accumulated in the FD by a reset pulse ΦRES. A floating diffusion amplifier (hereinafter referred to as “FDA”) is configured by a constant current source (not shown) connected to the FD, the amplification MOS amplifier 207, and the signal readout circuit. The signal charge of the pixel selected by the selection switch 208 is converted into a voltage and output to the CDS circuit 103 in FIG. PD1 and PD2 are separately connected to the transfer switches TX1 and TX2, but share a signal readout circuit including the FD, the amplification MOS amplifier 207, the selection switch 208, and the reset switch 209.

  The charge state of the pixel sharing the FD will be described with reference to FIGS. FIG. 3 is a diagram showing the cross-sectional structure of each part in the upper part and the potential distribution in the lower part. FIG. 4 is a diagram showing the relationship between the accumulated charge amount of each part and the exposure time. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the amount of charge. 3A is a pixel state at time t71 in FIG. 4, FIG. 3B is a pixel state at time t72 in FIG. 4, FIG. 3C is a pixel state at time t73 in FIG. (D) corresponds to the state of the pixel at time t74 in FIG. 4A shows the relationship between the accumulated charge amount of PD1 and the exposure time, FIG. 4B shows the relationship between the accumulated charge amount of PD2 and the exposure time, and FIG. 4C shows the accumulated charge amount of FD. The relationship with the exposure time is shown respectively. Here, it is assumed that PD1 is a pixel having a color filter with higher sensitivity than PD2.

  At time t71 (corresponding to FIG. 3A), PD1, PD2, and FD are reset, and signal charge accumulation is started.

  At time t72 (corresponding to FIG. 3B), signal charges are accumulated in PD1 and PD2.

  At time t73 (corresponding to FIG. 3C), the accumulated charge amount of PD1 exceeds the saturation charge amount. In PD1, since the potential barrier on the transfer switch TX1 side is the lowest, the signal charge generated in PD1 leaks to the FD. Referring to the lower potential distribution in FIG. 3 (c), since the potential barrier of the semiconductor region (p-type semiconductor) on the left side of PD1 is sufficiently high, unless a large negative potential φTX1 is given to the gate electrode of TX1, Such a potential distribution can be easily obtained.

  At time t74 (corresponding to FIG. 3D), the accumulated charge amount in PD1 and PD2 exceeds the saturation charge amount. At this time, in PD2, the potential barrier on the OFD side is lower than the potential barrier on the transfer switch TX2 side. For this reason, surplus charges greater than the saturation charge amount accumulated in the PD2 leak into the OFD without leaking into the FD. If the configuration of the semiconductor region (channel) between FD and PD2 is substantially the same as the configuration of the semiconductor region between OFD and PD2, by applying a negative potential φTX2 to the gate electrode of TX2, Such a potential distribution is obtained. This is because by applying a negative potential to the gate electrode of TX2, the potential (potential) under the transfer switch TX2 is lowered and the potential barrier under the transfer switch TX2 is increased. In this way, at time t74, surplus charges greater than the saturation charge amount accumulated in PD1 leak into the FD. Excess charge accumulated in the PD 2 exceeding the saturation charge amount does not leak to the FD but leaks to the OFD.

  Next, with reference to FIGS. 4 and 5, the state of the charge of the pixel having the OFD in both PD1 and PD2 will be described. FIG. 5 shows the cross-sectional structure of each part in the upper part and shows the potential distribution in the lower part. 5A shows the state of the pixel at time t71 in FIG. 4, FIG. 5B shows the state of the pixel at time t72 in FIG. 4, FIG. 5C shows the state of the pixel at time t73 in FIG. (D) corresponds to the state of the pixel at time t74 in FIG.

  At time t71 (corresponding to FIG. 5A), PD1, PD2, and FD are reset and accumulation of signal charges is started.

  At time t72 (corresponding to FIG. 5B), signal charges are accumulated in PD1 and PD2.

  At time t73 (corresponding to FIG. 5C), the accumulated charge amount of PD1 exceeds the saturation charge amount. At this time, in PD1, the potential barrier on the transfer switch TX1 side is lower than the potential barrier on the OFD side. Therefore, surplus charges greater than the saturation charge amount accumulated in PD1 leak into FD without leaking into OFD. Assuming that the configuration of the semiconductor region between OFD and PD1 is substantially the same as the configuration of the semiconductor region (channel) between FD and PD1, this is achieved by applying a positive potential φTX1 to the gate electrode of TX1. Such a potential distribution is obtained. This is because by applying a positive potential to the gate electrode of TX1, the potential (potential) under the transfer switch TX1 increases, and the potential barrier under the transfer switch TX1 decreases. Depending on the configuration of the semiconductor region between OFD and PD1, the potential distribution shown in FIG. 5C can also be obtained by applying φTX1 of zero or a weak negative potential to the gate electrode of TX1. As described above, at time t73, the signal charge generated in PD1 leaks to the FD, but does not leak to the OFD.

  At time t74 (corresponding to FIG. 5D), the accumulated charge amount in PD1 and PD2 exceeds the saturation charge amount. At this time, in PD2, the potential barrier on the OFD side is lower than the potential barrier on the transfer switch TX2 side. For this reason, surplus charges greater than the saturation charge amount accumulated in the PD2 leak into the OFD without leaking into the FD. If the configuration of the semiconductor region (channel) between FD and PD2 is substantially the same as the configuration of the semiconductor region between OFD and PD2, by applying a negative potential φTX2 to the gate electrode of TX2, Such a potential distribution is obtained. This is because by applying a negative potential to the gate electrode of TX2, the potential (potential) under the transfer switch TX2 is lowered and the potential barrier under the transfer switch TX2 is increased. In this way, at time t74, surplus charges greater than the saturation charge amount accumulated in PD1 leak into the FD. Excess charge accumulated in the PD 2 exceeding the saturation charge amount does not leak to the FD but leaks to the OFD.

  In this way, even when the OFD is arranged only in PD2 as shown in FIG. 3 or when the OFD is arranged in both PD1 and PD2 as shown in FIGS. And the surplus charge of PD2 leaks to OFD.

  The charge leaked to the FD is added to the signal of PD1 after being read out, so that the dynamic range can be expanded in the same manner as in the configuration in which the conventional signal readout circuit is one pixel.

  For explanation, the number of PDs sharing the FD is two. However, the number of PDs is not limited to this, and may be three or more, for example. When the FD is shared by two PDs, the dynamic range can be expanded more effectively by the method described later.

  In the configuration shown in FIG. 5, it is determined whether to discharge charges on the OFD side or on the FD side according to the voltages of φTX1 and φTX2 applied to TX1 and TX2. However, the configuration shown in FIG. 6 may be used.

  FIG. 6 shows a structure having a charge discharging switch in addition to the transfer switch. 6A is the state of the pixel at time t71 in FIG. 4, FIG. 6B is the state of the pixel at time t72 in FIG. 4, FIG. 6C is the state of the pixel at time t73 in FIG. (D) corresponds to the state of the pixel at time t74 in FIG.

  At time t71 (corresponding to FIG. 6A), PD1, PD2, and FD are reset, and signal charge accumulation is started.

  At time t72 (corresponding to FIG. 6B), signal charges are accumulated in PD1 and PD2.

  At time t73 (corresponding to FIG. 6C), the accumulated charge amount of PD1 exceeds the saturation charge amount. In PD1, the potential barrier on the transfer switch TX1 side is lower than the potential barrier on the charge discharge switch TOFD1 side. Therefore, surplus charges greater than the saturation charge amount accumulated in PD1 leak into FD without leaking into OFD. If the configuration of the semiconductor region (channel) between FD and PD1 is substantially the same as the configuration of the semiconductor region (channel) between OFD and PD1, the potential of φTX1 is made higher than the potential of φTOFD1. Such a potential distribution is obtained. This is because when the potential of φTX1 is made higher than the potential of φTOFD1, the potential (potential) under the transfer switch TX1 becomes relatively higher than the potential (potential) under the charge discharge switch TOFD1. This is because the potential barrier below the transfer switch TX1 is relatively lower than the potential barrier below the charge discharge switch TOFD1.

  At time t74 (corresponding to FIG. 6D), the accumulated charge amount exceeds the saturation charge amount in both PD1 and PD2. At this time, in PD2, the potential barrier on the charge discharge switch TOFD2 side is lower than the potential barrier on the transfer switch TX2 side. For this reason, surplus charges greater than the saturation charge amount accumulated in the PD2 leak into the OFD without leaking into the FD. If the configuration of the semiconductor region (channel) between FD and PD2 is substantially the same as the configuration of the semiconductor region (channel) between OFD and PD2, the potential of φTX2 is made lower than the potential of φTOFD2. Such a potential distribution is obtained. This is because when the potential of φTX2 is made lower than the potential of φTOFD2, the potential (potential) under the transfer switch TX2 becomes relatively lower than the potential (potential) under the charge discharge switch TOFD2. This is because the potential barrier below the transfer switch TX2 is relatively higher than the potential barrier below the charge discharge switch TOFD2. In this way, at time t74, surplus charges greater than the saturation charge amount accumulated in PD1 leak into the FD. Excess charge accumulated in the PD 2 exceeding the saturation charge amount does not leak to the FD but leaks to the OFD.

  FIG. 7 is a diagram showing details of the pixel shown in FIG. The same components as those in FIG. 2 are denoted by the same reference numerals. OFD is an overflow drain that discharges surplus charges, and is connected to PD1 and PD2 via charge discharge switches TOFD1 and TOFD2, respectively. The charge discharge switches TOFD1 and TOFD2 are driven by charge discharge pulses ΦTOFD1 and ΦTOFD2, respectively. Then, surplus charges of PD1 and PD2 are distributed to either OFD or FD according to the voltage values of φTX1, φTX2, ΦTOFD1, and ΦTOFD2.

  Next, a temporal relationship between the FD readout operation and the PD readout operation will be described with reference to FIG. In FIG. 8, time is taken on the horizontal axis, and it is assumed that four PDs share an FD for the sake of explanation. First, the image sensor resets the PD and FD prior to the shooting operation. Thereafter, accumulation starts, a signal is generated in the PD, and when the PD signal operating in the PD1 mode becomes equal to or higher than the saturation charge, the charge is discharged to the FD. When the PD signal operating in the PD2 mode becomes equal to or higher than the saturation charge, the charge is discharged to the OFD. Whether the PD in the PD1 mode is PDa, PDb, PDc, or PDd is determined by a color determination unit to be described later. PDs other than the PD1 mode operate as the PD2 mode. When the accumulation ends, the FD signal is read out. Thereafter, the FD is reset once and PDa which is the first PD is read. Thereafter, the FD is reset again and the second PDb is read. This operation is repeated until the fourth PDd is read. The read signal is saturated by one of the four PDs by adding an FD signal to the PDa to PDd operating in the PD1 mode by a color determination calculation unit described later. Is output as an enlarged image.

  The color determination means determines which PD has which color filter performs the operation of PD1 having a large signal amount. This will be described with reference to FIG. As shown at 1201 in FIG. 9A, the color determination means performs pre-photographing in the image sensor used for the main photographing immediately before the photographer performs the photographing operation, and sends the image to the color judgment calculation unit. The color determination calculation unit determines the color with the largest signal amount from the average value of the specific region, and operates the PD having the color filter as the above-described PD1 mode. Then, in order to operate the remaining PD as the above-described PD2 mode, as shown at 1202 in FIG. 9A, information on PD that causes the image sensor or an image sensor driving unit (not shown) to operate as the PD1 mode or PD information to be operated as the PD2 mode is sent. An image sensor or an image sensor drive unit (not shown) determines a drive pattern based on information from the color determination calculation unit, and performs actual photographing. Reference numeral 1203 in FIG. 9A shows a state in which an FD signal and a plurality of PD signals are output in the main photographing as described above. As shown in 1204 of FIG. 9A, the output signal is output from the signal processing circuit to the PD that has been operated as the PD1 mode among a plurality of PDs based on information from the color determination calculation unit. Is added. Other PDs are processed without adding an FD signal as a mode of PD2.

  Further, as shown in FIG. 9B, in addition to the image sensor used for the actual photographing, there is a separate device for color determination, and an image to be captured from now on according to color information from the device for color determination. It is predicted which PD having which color filter has the largest amount of generated signals. Then, it is possible to operate the PD as a mode of PD1. In this case, data exchange (1206 to 1208) other than 1205 in FIG. 9B is the same as that in FIG.

  Each pixel has a color filter, which is regularly arranged in the vertical and horizontal directions as shown in FIG. FIG. 10A shows an array using three types of color filters, and FIG. 10B shows an array using four types of color filters. Here, it is assumed that the two pixels sharing the FD are arranged in the vertical direction. As shown in FIG. 10B, when four types of color filters are used, the most sensitive color filter is arranged in the above-described PD1. Since the two pixels sharing the FD are arranged in the vertical direction, the pixel arranged horizontally next to PD1 is also PD1. Therefore, the dynamic range of two colors is expanded. In the case shown in FIG. 10B, it is more preferable from the viewpoint of expanding the dynamic range to arrange two colors from a color filter with high sensitivity in the row where the dynamic range is expanded.

  When the three types of color filters shown in FIG. 10A are used, there are often two color filters with the highest sensitivity in normal shooting. Therefore, by setting the color filter having the lowest sensitivity to the row of PD2, the amount of charge handled by the PD of a color other than the PD having the color filter having the lowest sensitivity is increased, and other than the PD having the color filter having the lowest sensitivity. An image with an expanded dynamic range of pixels can be obtained.

  In addition, when a pixel having a color filter with the lowest sensitivity is saturated, the surrounding pixels may be regarded as saturated and the signal may be changed by signal processing.

  Next, an imaging apparatus incorporating the imaging unit 100 according to the present embodiment will be described. FIG. 11 is a diagram illustrating the imaging apparatus according to the present embodiment.

  Light rays enter the imaging unit 100 through the optical system 1 having a diaphragm mechanism and a lens. A mechanical shutter 2 is disposed between the optical system 1 and the imaging unit 100 or in the optical system 1. The optical system 1, the mechanical shutter 2, and the imaging unit 100 are driven by the drive circuit 7. The A / D converter 5 converts the analog signal processed by the CDS circuit (the CDS circuit 103 in FIG. 1) in the imaging unit 100 into a digital signal. The timing signal generation circuit 6 generates a timing signal to be provided to the imaging unit 100, the CDS circuit 103, and the A / D converter 5. The signal processing circuit 8 performs various signal processing on the A / D converted image data in addition to the above-described signal processing. The image memory 9 is used for temporarily storing a digital image signal during signal processing or for storing image data which is a digital image signal subjected to signal processing. The recording circuit 11 records the signal-processed image data on the recording medium 10. The display circuit 13 provides the image data subjected to the signal processing to the image display device 12 to display an image.

  A ROM 15 such as a non-volatile memory stores a control program, control data such as parameters and tables used when executing the program, and correction data such as a flaw address. A program, control data, and correction data stored in the ROM 15 are transferred to the RAM 16 and used by the control unit 14 that controls the entire imaging apparatus.

  Prior to the photographing operation, necessary programs, control data, and correction data are transferred from the ROM 15 to the RAM 16 when the operation of the control unit 14 such as when the image pickup apparatus is turned on. The optical system 1 drives a diaphragm and a lens in accordance with a control signal sent from the control unit 14 to form a subject image set to an appropriate brightness on the image sensor 100. Next, the mechanical shutter 2 is driven so as to shield the image capturing unit 100 in accordance with the operation of the image sensor in accordance with a control signal sent from the control unit 14. The imaging unit 100 is driven by a drive pulse generated by the drive circuit 7 based on an operation pulse generated by the timing signal generation circuit 6 controlled by the control unit 14, and converts the subject image into an electrical signal by photoelectric conversion. Output as an analog image signal. The analog image signal output from the imaging unit 100 is subjected to the operation pulse generated by the timing signal generation circuit 6 controlled by the control unit 14, the clock synchronization noise is removed by the CDS circuit 103, and the A / D converter 5. Is converted into a digital image signal. Next, in the signal processing circuit 8 controlled by the control unit 14, image processing such as color conversion, white balance, and gamma correction, resolution conversion processing, image compression processing, and the like are performed on the digital image signal. The image data signal-processed by the signal processing circuit 8 and the image data stored in the image memory 9 are converted into data suitable for the image recording medium 10 (for example, file system data having a hierarchical structure) in the recording circuit 11. . Then, after being recorded on the recording medium 10 or subjected to resolution conversion processing by the signal processing circuit 8, the display circuit 13 converts the image into a signal suitable for the image display device 12 (for example, NTSC analog signal). Or displayed on the display device 12.

  Here, the signal processing circuit 8 may output the digital image signal as it is to the image memory 9 or the recording circuit 11 as image data without performing signal processing. Further, when requested by the control unit 14, the signal processing circuit 8 outputs information on digital image signals and image data generated in the signal processing process to the control unit 14. Such information includes, for example, information such as the spatial frequency of the image, the average value of the designated area, the data amount of the compressed image, or information extracted from them. Further, the recording circuit 11 outputs information such as the type and free capacity of the image recording medium 10 to the control unit 14 when requested by the control unit 14.

It is a figure which shows the structure of the imaging part which concerns on suitable embodiment of this invention. It is a figure which shows the detail of the pixel arrange | positioned at a photoelectric conversion apparatus. It is a figure showing the positional relationship and potential of the photodiode and FD which concern on suitable embodiment of this invention. It is a figure explaining the relationship between the accumulation time and signal amount of the image pick-up element which concerns on suitable embodiment of this invention. It is a figure showing the positional relationship and potential of the photodiode and FD which concern on suitable embodiment of this invention. It is a figure showing the positional relationship and potential of a photodiode and FD in a structure having a charge discharge switch in addition to a transfer switch. It is a figure which shows the circuit structure in connection with reading of 2 pixels which share a signal reading circuit. It is a figure explaining the time relationship of the drive of an image sensor. It is a figure explaining the imaging device containing a color determination means. It is a figure explaining the positional relationship of the color filter of the image pick-up element which concerns on suitable embodiment of this invention. It is a block diagram of a digital camera to which an image sensor according to a preferred embodiment of the present invention is applied. It is a figure which shows a mode that when the signal charge accumulate | stored in PD exceeds the saturation signal amount, it leaks into the place where a potential barrier is low. It is a figure which shows the cross-sectional structure of each part common to the conventional 2 pixels, and its potential distribution. It is the figure explaining the relationship between the accumulation time of the conventional image pick-up element common to 2 pixels, and signal amount.

Explanation of symbols

14 Control Unit 101 Photoelectric Conversion Device PD1, Photodiode FD Floating Diffusion OFD Charge Discharge Area

Claims (9)

A first photoelectric conversion element and a second photoelectric conversion element that photoelectrically convert light into electric charge; an accumulation unit that temporarily accumulates electric charges accumulated in the first and second photoelectric conversion elements; and the first, A pixel having an output unit that converts the charge transferred from the second photoelectric conversion element to the storage unit into a voltage and outputs the voltage is a two-dimensionally arranged photoelectric conversion device,
When the accumulated charge amount of the first photoelectric conversion element exceeds the saturation charge amount, control is performed by the first operation of discharging the surplus charge to the accumulation unit, and the accumulated charge of the second photoelectric conversion element A photoelectric conversion device comprising: a control unit that performs control in a second operation of discharging the surplus charge to a charge discharge region when the amount exceeds a saturation charge amount.   The photoelectric conversion device according to claim 1, wherein the charge discharge region is disposed in the vicinity of the second photoelectric conversion element.   The photoelectric conversion device according to claim 2, wherein the charge discharge region is further disposed in the vicinity of the first photoelectric conversion element. A first transfer switch disposed between the first photoelectric conversion element and the storage unit;
A second transfer switch disposed between the second photoelectric conversion element and the storage unit;
A first charge discharge switch disposed between the first photoelectric conversion element and the charge discharge region;
A second charge discharge switch disposed between the second photoelectric conversion element and the charge discharge region;
With
When the control is performed in the first operation, the control unit applies a voltage higher than the voltage applied to the first charge discharge switch to the first transfer switch, and performs the control in the second operation. 4. The photoelectric conversion device according to claim 3, wherein, when performing, control is performed so that a voltage lower than a voltage applied to the second charge discharge switch is applied to the second transfer switch. 5.   5. The photoelectric conversion device according to claim 1, wherein a plurality of color filters are arranged in the pixel. 6. A colorimetric means different from the first and second photoelectric conversion elements;
Color determination means for determining a highly sensitive color among the image information acquired by the color measurement means;
With
The control unit drives the photoelectric conversion element in which the color filter determined to be high in sensitivity by the color determination unit among the first and second photoelectric conversion elements is arranged in the first operation. The photoelectric conversion device according to claim 5, wherein control is performed. Color determination means for determining a color with high sensitivity based on image information acquired from the first and second photoelectric conversion elements before actual photographing;
The control unit performs control so as to drive a photoelectric conversion element having a color filter determined to have high sensitivity by the color determination unit among the first and second photoelectric conversion elements in the first operation. The photoelectric conversion device according to claim 5, wherein the photoelectric conversion device is performed. Optical system,
The photoelectric conversion device according to any one of claims 1 to 7,
An imaging apparatus comprising: A first photoelectric conversion element and a second photoelectric conversion element that photoelectrically convert light into electric charge; an accumulation unit that temporarily accumulates electric charges accumulated in the first and second photoelectric conversion elements; and the first, A method of controlling a photoelectric conversion device in which pixels having an output unit that converts the charge transferred from the second photoelectric conversion element to the storage unit into a voltage and outputs the voltage are two-dimensionally arranged, and
When the accumulated charge amount of the first photoelectric conversion element exceeds the saturation charge amount, the excess charge is discharged to the accumulation unit, and the accumulated charge amount of the second photoelectric conversion element exceeds the saturation charge amount The control method of the photoelectric conversion device, characterized in that control is performed by a second operation of discharging the surplus charge to the charge discharge region.

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