JP2010166396A - Method of driving image sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To read all the charges of a sub-pixel under exposure, in an image sensor capable of independently controlling timing to read signal charges of a main pixel and timing to read signal charges of a slave pixel. <P>SOLUTION: Before the lapse of a first predetermined time from the start of exposure, signal charges are read from the photodetector of a sub-pixel by a second reading means to remove unwanted charges stored in the photodetector of the sub-pixel. When the first predetermined time elapses from the start of exposure, signal charges are read from the photodetector of the sub-pixel by a second reading means to start exposure of the sub-pixel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image sensor driving method, and more particularly to an image sensor driving method capable of independently controlling a signal charge readout timing of a main pixel and a signal charge readout timing of a slave pixel.

  In order to obtain an image with a wide dynamic range, an imaging apparatus using an imaging device including a relatively high-sensitivity high-sensitivity pixel and a relatively low-sensitivity low-sensitivity element is known. However, the sensitivity ratio between the high-sensitivity pixel and the low-sensitivity pixel cannot be changed because it depends on the structure of the image sensor. Therefore, it is difficult to shoot with an optimum dynamic range according to the scene.

To deal with such a problem, Patent Document 1 is configured such that the signal charge readout timing of the main pixel and the signal charge readout timing of the slave pixel can be controlled independently, and at least one charge accumulation start time is controlled. Thus, there is described an image pickup device that can change the sensitivity of at least one of the image signal of the main pixel and the image signal of the sub-pixel. According to the image sensor described in Patent Document 1, it is possible to capture an image with an optimum dynamic range according to the scene.
JP-A-2005-72966

  As the resolution of the image sensor increases, the photodiode is miniaturized, and the width of the vertical transfer path (VCCD) is also becoming finer. When the line width of the VCCD is reduced, the saturation capacity of the VCCD is also reduced. In order to increase the saturation capacity of the VCCD, it is conceivable to increase the potential of the VCCD. In this case, the dark current characteristic deteriorates due to an increase in the dark current of the VCCD, and the image quality deteriorates when the ISO sensitivity is high. Occurs. Therefore, it is not preferable to design the potential of VCCD deeply.

  As described above, the line width of the VCCD becomes finer and the potential of the VCCD cannot be deepened from the viewpoint of image quality, so that all unnecessary charges accumulated in the photodiode cannot be read out to the VCCD. In addition, when all the unnecessary charges accumulated in the photodiode are read out, the read voltage (depletion voltage that depletes the photodiode) increases.

  As the depletion voltage is increased in this way, when controlling the readout timing of the main pixel and the sub-pixel independently in order to acquire an image with a wide dynamic range, out of unnecessary charges of the sub-pixel during the exposure period. There was a phenomenon that all could not be read out (leftovers occurred). Since all the charges of the sub-pixels during the exposure period cannot be read, the image quality of the finally created image is deteriorated.

  The present invention has been made in view of such circumstances, and in an imaging device capable of independently controlling the readout timing of the signal charge of the main pixel and the readout timing of the signal charge of the slave pixel, the charge of the subpixel being exposed. An object of the present invention is to provide a method of driving an image sensor for reading out all of the above.

  In order to achieve the above object, the image sensor driving method according to claim 1 is a plurality of light receiving elements arranged two-dimensionally, including a light receiving element of a main pixel and a light receiving element of a sub-pixel. A light receiving element, an exposure start means for simultaneously starting exposure of the light receiving element of the main pixel and the light receiving element of the sub pixel, and the light receiving element of the main pixel and the sub pixel by shielding the plurality of light receiving elements from light. A mechanical shutter that terminates exposure to the light receiving elements simultaneously, and a vertical transfer that is arranged for each vertical line of the plurality of light receiving elements, and that transfers signal charges read from the light receiving elements in the vertical direction in synchronization with a vertical transfer pulse. A first readout means for reading out the signal charge accumulated in the light receiving element of the main pixel to the vertical transfer path by the first readout pulse, and receiving the sub-pixel by the second readout pulse. A second readout means for reading out the signal charge accumulated in the element to the vertical transfer path and a common connection to the output ends of the plurality of vertical transfer paths, and the signal charge output from the vertical transfer path is transferred to the horizontal transfer pulse. An image pickup comprising a horizontal transfer path that transfers in the horizontal direction in synchronization with the output and a generation unit that is connected to the output end of the horizontal transfer path and generates an output signal corresponding to the signal charge output from the horizontal transfer path An element driving method comprising: an exposure start step of starting exposure by the exposure start means; and a light receiving element of the sub-pixel by the second readout means at the elapse of a first predetermined time after the start of exposure. Reading out the signal charge from the subpixel exposure start step for starting signal charge accumulation in the light receiving element of the subpixel from the elapse of the first predetermined time, and the first predetermined time from the start of exposure. Before the elapse of time, a removal step of reading out signal charges from the light receiving element of the subpixel by the second reading means and removing unnecessary charges accumulated in the light receiving element of the subpixel; An exposure end step of ending exposure by the mechanical shutter when the second predetermined time has elapsed.

  According to the present invention, the signal charge is read from the light receiving element of the subpixel by the second reading means and accumulated in the light receiving element of the subpixel before the first predetermined time elapses from the start of exposure. Since the signal charge is read from the light receiving element of the sub-pixel by the second reading means when the first predetermined time has elapsed after the charge is removed and exposure is started, the depletion voltage is reduced and the exposure is in progress. All the charges of the sub-pixels can be read out.

  According to a second aspect of the present invention, in the image sensor driving method according to the first aspect, the removing step removes unnecessary charges accumulated in the light receiving element of the sub-pixel by a plurality of the second readout pulses. It is characterized by.

  As a result, the depletion voltage can be reduced and all the charges of the sub-pixels being exposed can be read out.

  3. The image sensor driving method according to claim 1, wherein the removing process reads the signal charge from the light receiving element of the sub-pixel by the second reading unit, and then performs the sub-pixel exposure. Until the start process starts the accumulation of signal charges in the light receiving element of the sub-pixel, the vertical transfer pulse is continuously applied to the vertical transfer path to read out to the vertical transfer path through the removal process. The signal charge is removed from the vertical transfer path.

  As a result, the depletion voltage can be reduced and all the charges of the sub-pixels being exposed can be read out.

  4. The method of driving an image sensor according to claim 1, wherein the sub-pixel exposure is performed after the removal step reads out a signal charge from the light-receiving element of the sub-pixel by the second readout unit. The signal charge read out to the vertical transfer path by the removing process is changed to the pinning state by starting the accumulation of signal charges in the light receiving element of the sub-pixel. It is characterized by being removed from the vertical transfer path.

  As a result, the depletion voltage can be reduced and all the charges of the sub-pixels being exposed can be read out.

  5. The image sensor driving method according to claim 1, wherein the vertical transfer pulse is continuously applied to the vertical transfer path after the exposure is completed in the exposure end step. And a sweeping step of removing the signal charge read out to the vertical transfer path by the sub-pixel exposure start process from the vertical transfer path.

  Thereby, the signal charge read to the vertical transfer path by the subpixel exposure start process can be appropriately removed.

  According to a sixth aspect of the present invention, in the method for driving an image pickup device according to the fifth aspect, the light receiving element of the main pixel and the second read-out device are used by the first read-out device and the second read-out device after the sweep-out step is completed. The signal charge accumulated in the light receiving element of the sub-pixel is read out to the vertical transfer path.

  Thus, a captured image can be acquired based on the signal charges accumulated in the light receiving elements of the main pixel and the sub pixels.

  According to the present invention, the signal charge is read from the light receiving element of the subpixel by the second reading means and accumulated in the light receiving element of the subpixel before the first predetermined time elapses from the start of exposure. Since the signal charge is read from the light receiving element of the sub-pixel by the second reading means when the first predetermined time has elapsed after the charge is removed and exposure is started, the depletion voltage is reduced and the exposure is in progress. All the charges of the sub-pixels can be read out.

  The best mode for carrying out the present invention will be described below.

  FIG. 1 is a diagram illustrating an example of an electrical configuration of the digital camera 1. As shown in the figure, the digital camera 1 includes a lens 10, an aperture 11, a lens / aperture drive unit 12, a CCD 13, an AFE & TG unit 14, a signal processing unit 19, an operation unit 21, an external memory 22, an LCD display unit 23, an I / O interface unit 24, flash 25, and the like.

  Each unit operates under the control of the CPU 20 of the signal processing unit 19, and the CPU 20 controls each unit of the digital camera 1 by executing a predetermined control program based on an input from the operation unit 21.

  The digital camera 1 includes a ROM (not shown), in which various data necessary for control are recorded in addition to a control program executed by the CPU 20. The CPU 20 controls each part of the digital camera 1 by reading a control program recorded in the ROM into a main memory (not shown) and sequentially executing the program.

  The operation unit 21 includes a power button, a shutter release button, a shooting mode / playback mode switch, and the like (not shown), and outputs a signal corresponding to each operation to the CPU 20.

  The lens 10 and the diaphragm 11 include a zoom lens, a focus lens, and a mechanical shutter (not shown). The lens 10 and the diaphragm 11 are driven by a lens / diaphragm driving unit 12 to perform zooming, focusing, aperture opening amount (F value) change, and mechanical shutter opening / closing. . The CPU 20 controls the lens / diaphragm driving unit 12 to adjust the position of a focus lens (not shown) to the in-focus position, and also controls the aperture amount of the aperture so that the exposure amount becomes an appropriate exposure.

  The CCD 13 is disposed at the rear stage of the diaphragm 11 and receives subject light transmitted through the lens 10 and the like.

  FIG. 2 is a schematic view of the light receiving surface of the CCD 13. As shown in the figure, on the light receiving surface of the CCD 13, a row of light receiving elements (photodiodes) 13a of the main pixel and a row of light receiving elements 13b of the sub pixel are alternately arranged, and the row of the main pixel 13a is the sub pixel 13b. A so-called honeycomb pixel array is formed that is shifted by 1/2 pitch with respect to the column. The arrangement of the light receiving elements of the CCD 13 is not limited to this example. For example, a so-called Bayer pixel arrangement may be used.

  Further, three primary color filters (R = red, G = green, B = blue) are provided on each light receiving element, and R pixels and G pixels are alternately arranged in each column of the main pixels 13a. And columns in which B pixels and G pixels are alternately arranged are alternately arranged. Similarly, for each column of the sub-pixels 13b, columns in which R pixels and G pixels are alternately arranged and columns in which B pixels and G pixels are alternately arranged are alternately arranged.

  Each column of the main pixel 13a and each column of the sub-pixel 13b is provided with one VCCD for each column, and the readout of the main pixel to the VCCD 13c and the readout of the sub-pixel to the VCCD 13d are performed by individual readout pulses. It can be done independently. Further, as will be described later, the residual charges in the light receiving elements of the main pixel 13a and the sub-pixel 13b can be simultaneously discarded to the semiconductor substrate side by the OFD shutter pulse.

  Note that the main pixel 13a and the sub-pixel 13b may be configured to be read to a common VCCD as long as the reading of the main pixel 13a and the sub-pixel 13b to the VCCD can be controlled independently.

  The subject light imaged on the light receiving surface of the CCD 13 is converted into an electrical signal by each light receiving element and accumulated.

  The electrical signals accumulated in the respective light receiving elements are read independently to the VCCDs 13c and 13d by the respective readout pulses of the main pixel 13a and the sub-pixel 13b supplied from the timing generator 18 of the AFE & TG unit. The VCCDs 13c and 13d transfer this signal to a horizontal transfer path (HCCD) (not shown) line by line in synchronization with the clock supplied from the timing generator 18. Further, the HCCD outputs the signal for one line transferred from the VCCDs 13c and 13d to the AFE & TG unit in synchronization with the clock supplied from the timing generator 18.

  The AFE & TG unit includes a correlated double sampling circuit (CDS) 15, a variable gain amplifier (VGA) 16, and an A / D converter 17.

  The CDS 15 removes noise included in the image signal. The VGA 16 amplifies the image signal from which the noise component has been removed with a predetermined gain corresponding to the set photographing sensitivity (ISO sensitivity). The analog image signal subjected to the required signal processing is converted into a digital image signal having a gradation width of a predetermined bit by the A / D converter 17. This image signal is so-called RAW data, and has a gradation value indicating the density of R, G, and B for each pixel. The digital image signal is output to the signal processing unit 19 and stored in a main memory (not shown).

  The signal processing unit 19 performs predetermined signal processing on the image signals of R, G, and B colors stored in the main memory, and the image signal (Y / C) composed of the luminance signal Y and the color difference signals Cr and Cb. Signal).

  Further, the signal processing unit 19 performs compression processing in a predetermined format (for example, JPEG) on the image signal (Y / C signal) composed of the input luminance signal Y and the color difference signals Cr and Cb in accordance with a compression command from the CPU 20. To generate compressed image data. The generated data can be recorded in the external memory 22.

  The external memory 22 may be removable from the main body of the digital camera 1 such as a memory card, or may be built in the main body of the digital camera 1. In the case of detachable, a card slot is provided in the main body of the digital camera 1, and the card slot is used by being loaded.

  In addition, the signal processing unit 19 controls display on the LCD display unit 23 in accordance with a command from the CPU 20. The LCD display unit 23 can display a moving image (through image) and use it as an electronic viewfinder, and can display a photographed image before recording (post-view image), a reproduced image read from the external memory 22, and the like. LCD monitor.

  The I / O interface 24 is a serial interface such as USB 2.0, IEEE 1394, wireless LAN, or the like, and enables data input / output between the digital camera 1 and an external device.

  The flash 25 emits photographing auxiliary light in accordance with a command from the CPU 20.

<First Embodiment>
With reference to FIG. 3, the unnecessary charge sweeping operation of the sub-pixel of the digital camera 1 of the first embodiment will be described.

  The user can set the digital camera 1 to the dynamic range expansion photographing mode using the operation unit 21. The dynamic range expansion photographing mode is a mode in which the main pixel 13a and the sub-pixel 13b are photographed with different exposure times, and an image obtained by enlarging the dynamic range is obtained by performing addition processing on the images photographed by the respective pixels. is there. In this mode, the user can set an arbitrary dynamic range expansion rate.

  When the digital camera 1 is set to the dynamic range expansion shooting mode and a shutter release button (not shown) of the operation unit 21 is operated, the CPU 20 opens a mechanical shutter (not shown) to expose the main pixel 13a and the sub pixel 13b of the CCD 13. Then, charge accumulation is started (timing T1).

  Thereafter, the CPU 20 controls the TG 18 and outputs an OFD shutter pulse (timing T1 to T2). The OFD shutter pulse is applied from the TG 18 to an overflow drain electrode (not shown) of the CCD 13 in synchronization with the horizontal synchronizing signal. The charges accumulated in the main pixel 13a and the sub-pixel 13b by the OFD shutter pulse are transferred to the substrate in the CCD 13. To the side.

  That is, the exposure period for photographing is from the time point when the application of the OFD shutter pulse is completed (timing T2) to the time point when the mechanical shutter is closed (timing T4). Therefore, the application of the OFD shutter pulse is controlled so that this exposure period is an exposure time for proper exposure. In the dynamic range expansion photographing mode, the main pixel 13a is exposed during the exposure time for proper exposure, and the main pixel 13a accumulates signal charges corresponding to the exposure amount.

  Here, the sub-pixel 13b needs to be exposed with an exposure time (timing T3 to T4) that causes the underexposure to be less than the appropriate exposure according to the enlargement ratio of the dynamic range. For this reason, the CPU 20 controls the TG 18, outputs a TG pulse (readout pulse) of the subpixel at timing T3, and controls the exposure time of the subpixel to be timings T3 to T4. Therefore, the sub-pixel 13b accumulates signal charges corresponding to the exposure amount during the period from the timing T3 to T4.

  This read pulse is composed of potentials VH, VM, and VL as shown in FIG. The potentials VL and VM are applied when the charge of the VCCD 13d is transferred in the vertical direction, and the potential VH is a potential applied when the charge accumulated in the sub-pixel 13b is read out to the VCCD 13d (during field shift). is there. For example, VL is −8V, VM is 0V, and VH is 14V, and the potential VH is applied at timing T3, and the unnecessary charge of the subpixel 13b is read out to the subpixel VCCD 13d. That is, after the potential VH is applied, the sub-pixel 13b newly starts to accumulate signal charges according to the exposure amount.

  However, since one TG pulse at the timing T3 may not be able to read all of the unnecessary charges of the sub-pixel 13b (unread reading may occur), the CPU 20 removes unnecessary charges at the timings T2 to T3. A TG pulse for reading (pulse of potential VH) is output. The TG pulse for reading out this unnecessary charge is preferably output immediately before the timing T3. As will be described later, it is preferable to output a plurality of outputs.

  As described above, after the exposure start times of the main pixel 13a and the sub-pixel 13b are controlled to be different from each other, at the timing T4, the CPU 20 simultaneously exposes the main pixel 13a and the sub-pixel 13b by closing the mechanical shutter. finish. Thereafter, the VCCDs 13c and 13d are swept out at high speed (continuous output of vertical transfer clocks with potentials VL and VM), and unnecessary charges on the VCCDs 13c and 13d are swept out. Further, the TG pulse of the main pixel and the TG pulse of the sub-pixel are output, and the charges accumulated in the main pixel 13a and the sub-pixel 13b are read out to the VCCDs 13c and 13d (timing T5).

  Thereafter, these charges are transferred through the VCCDs 13c and 13d and a horizontal transfer path (not shown) to acquire an image (timing T5 to T6). Description of dynamic range expansion processing using an image shot with appropriate exposure at the main pixel and an image shot with exposure below the appropriate exposure according to the dynamic range expansion rate at the sub-pixel Is omitted.

  FIG. 4 is a graph showing the relationship between the number of sub-pixel TG pulses output at timings T2 to T3 and the depletion voltage of the sub-pixel 13b when the power supply voltage is 14V. As shown in the figure, the depletion voltage is reduced as the number of TG pulses increases. That is, as the number of TG pulses increases, a phenomenon in which all the charges of the subpixel cannot be read is less likely to occur. For example, when it is desired that the depletion voltage has a margin of 2.0 V or more from the power supply voltage, it is understood that the TG pulse is required about nine times. The period for outputting these TG pulses may be determined as appropriate.

  As described above, when the TG pulse is output during the exposure period and the exposure period is reset to start photographing, a plurality of TG pulses are output immediately before that to read out all unnecessary charges in the pixel. It becomes possible.

<Second Embodiment>
Next, the unnecessary charge sweeping operation of the sub-pixel of the digital camera 1 according to the second embodiment will be described. FIG. 5 is a timing chart of the unnecessary charge sweeping operation in the second embodiment, and the description of the parts common to FIG. 3 is omitted.

  As in the first embodiment, in the dynamic range expansion shooting mode, after the mechanical shutter is opened (timing T1), the OFD shutter pulse is output, and the exposure of the main pixel 13a starts from the time of the last OFD shutter pulse output. (Timing T2).

  Further, at timing T3, a TG pulse is output from the sub-pixel 13b, and exposure of the sub-pixel 13b is started by reading out unnecessary charges from the sub-pixel 13b. Further, at timing T4, the mechanical shutter is closed, and the exposure of the main pixel 13a and the sub-pixel 13b is simultaneously finished.

  Here, since there is a possibility that one of the unnecessary charges of the sub-pixel 13b cannot be read with one TG pulse at the timing T3, the CPU 20 outputs a TG pulse at the timing T2-T3 to output the sub-pixel 13b. After the unnecessary charges are read out, high-speed sweeping (continuous output of vertical transfer clocks of potentials VL and VM) is performed on the VCCD 13d of the sub-pixel.

  In this way, by removing unnecessary charges read from the subpixel 13b to the VCCD 13d of the subpixel by high-speed sweeping, the depletion voltage is reduced, and then all unnecessary charges of the subpixel 13b can be read by the TG pulse applied thereafter. It becomes possible.

  When outputting a plurality of TG pulses in the first embodiment, high-speed sweeping of the VCCD 13d may be performed between each TG pulse output.

<Third Embodiment>
Next, the unnecessary charge sweeping operation of the sub-pixel of the digital camera 1 according to the third embodiment will be described. FIG. 6 is a timing chart of the unnecessary charge sweeping operation in the third embodiment, and the description of the parts common to FIG. 3 is omitted.

  As in the first embodiment, in the dynamic range expansion shooting mode, after the mechanical shutter is opened (timing T1), the OFD shutter pulse is output, and the exposure of the main pixel 13a starts from the time of the last OFD shutter pulse output. (Timing T2).

  Further, at timing T3, a TG pulse is output from the sub-pixel 13b, and exposure of the sub-pixel 13b is started by reading out unnecessary charges from the sub-pixel 13b. Further, at timing T4, the mechanical shutter is closed, and the exposure of the main pixel 13a and the sub-pixel 13b is simultaneously finished.

  Here, since there is a possibility that one of the unnecessary charges of the sub-pixel 13b cannot be read with one TG pulse at the timing T3, the CPU 20 outputs a TG pulse at the timing T2-T3 to output the sub-pixel 13b. After the unnecessary charges are read out, the sub-pixel VCCD 13d is brought into the pinning state. Here, the pinning state refers to a state in which a potential well is not formed in a channel region under each transfer electrode by controlling each transfer electrode (not shown) of the VCCD to a predetermined potential (for example, a potential VL). Therefore, unnecessary charges read from the sub-pixel 13b to the VCCD 13d are discharged without being accumulated in the VCCD 13d.

  In this way, by removing unnecessary charges read from the subpixel 13b to the VCCD 13d of the subpixel by the pinning state, the depletion voltage is reduced, and then all unnecessary charges of the subpixel 13b can be read by the TG pulse applied thereafter. It becomes possible.

  In the present embodiment, the unnecessary charge sweeping operation of the sub-pixel is performed in the dynamic range expansion photographing mode of the digital camera 1. However, if the main pixel 13a and the sub-pixel 13b have different exposure times, other modes are possible. It is also applicable to. For example, the present invention may be applied to a case where shooting is performed with different exposure times for the main pixel 13a and the sub-pixel 13b in a mode in which two images having different shooting sensitivities are shot in one shutter release operation.

FIG. 1 is a diagram illustrating an example of an electrical configuration of the digital camera 1. FIG. 2 is a schematic view of the light receiving surface of the CCD 13. FIG. 3 is a timing chart showing an unnecessary charge sweeping operation of the sub-pixel of the digital camera 1 according to the first embodiment. FIG. 4 is a graph showing the relationship between the number of TG pulses of the sub-pixel and the depletion voltage of the sub-pixel 13b. FIG. 5 is a timing chart of the unnecessary charge sweeping operation in the second embodiment. FIG. 6 is a timing chart of the unnecessary charge sweeping operation in the third embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Digital camera, 10 ... Lens, 11 ... Aperture, 12 ... Lens and aperture drive part, 13 ... CCD, 13a ... Main pixel, 13b ... Subpixel, 13c ... VCCD of main pixel, 13d ... VCCD of subpixel, 14 ... AFE & TG section, 18 ... timing generator, 19 ... signal processing section, 20 ... CPU, 21 ... operation section

Claims (6)

A plurality of light-receiving elements arranged two-dimensionally, including a light-receiving element of a main pixel and a light-receiving element of a sub-pixel;
Exposure start means for simultaneously starting exposure of the light receiving element of the main pixel and the light receiving element of the sub-pixel;
A mechanical shutter that simultaneously terminates exposure of the light receiving element of the main pixel and the light receiving element of the sub-pixel by shielding the plurality of light receiving elements;
A vertical transfer path that is arranged for each vertical line of the plurality of light receiving elements, and that transfers signal charges read from the light receiving elements in a vertical direction in synchronization with a vertical transfer pulse;
First readout means for reading out signal charges accumulated in the light receiving element of the main pixel to the vertical transfer path by a first readout pulse;
Second readout means for reading out the signal charge accumulated in the light receiving element of the sub-pixel by the second readout pulse to the vertical transfer path;
A horizontal transfer path that is connected in common to the output ends of the plurality of vertical transfer paths, and that transfers signal charges output from the vertical transfer paths in the horizontal direction in synchronization with horizontal transfer pulses;
Generating means connected to the output end of the horizontal transfer path and generating an output signal corresponding to the signal charge output from the horizontal transfer path;
A method for driving an image sensor comprising:
An exposure start step of starting exposure by the exposure start means;
When the first predetermined time has elapsed from the start of exposure, the signal charge is read from the light receiving element of the subpixel by the second reading means, so that the light reception of the subpixel from the first predetermined time has elapsed. A sub-pixel exposure start step for starting signal charge accumulation in the device;
Before the first predetermined time elapses from the start of exposure, the signal charge is read from the light receiving element of the subpixel by the second reading means, and unnecessary charges accumulated in the light receiving element of the subpixel are removed. A removal step to remove;
An exposure end step of ending the exposure by the mechanical shutter when a second predetermined time has elapsed since the start of exposure; and
A method for driving an image sensor, comprising:   2. The image sensor driving method according to claim 1, wherein in the removing step, unnecessary charges accumulated in the light receiving element of the sub-pixel are removed by a plurality of the second readout pulses. 3.   From the time when the removing step reads out the signal charge from the light receiving element of the subpixel by the second reading unit to the time when the subpixel exposure start step starts accumulation of the signal charge in the light receiving element of the subpixel. 3. The signal charge read to the vertical transfer path by the removing step is removed from the vertical transfer path by continuously applying the vertical transfer pulse to the vertical transfer path. The driving method of the image sensor described in 1.   From the time when the removing step reads out the signal charge from the light receiving element of the subpixel by the second reading unit to the time when the subpixel exposure start step starts accumulation of the signal charge in the light receiving element of the subpixel. 3. The imaging device according to claim 1, wherein the signal charge read to the vertical transfer path by the removing step is removed from the vertical transfer path by setting the vertical transfer path to a pinning state. 4. Driving method.   After the exposure is completed by the exposure end step, the vertical transfer pulse is continuously applied to the vertical transfer path, and the signal charge read to the vertical transfer path by the sub-pixel exposure start step is transferred to the vertical transfer path. 5. The image pickup element driving method according to claim 1, further comprising a sweeping step of removing from the image pickup device.   After completion of the sweeping-out step, the signal charges accumulated in the light receiving element of the main pixel and the light receiving element of the sub-pixel are read out to the vertical transfer path by the first reading unit and the second reading unit. The method for driving an image pickup device according to claim 5, wherein:

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