JP2011015205A - Digital camera and method for driving solid-state imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To capture a high-quality image of a subject, irrespective of whether the subject is light or dark, even when photographing takes place, with the ISO sensitivity fixed at a predetermined value.SOLUTION: A digital camera includes a solid-state imaging device which includes a plurality of pixels, arranged in a two-dimensional array on a surface of a semiconductor substrate, receives incident light from the subject, and outputs a captured image signal of the subject; a controller which selects a drive mode from a plurality of previously prepared drive modes (S2, S3, S4) depending on the brightness of the subject, when shooting takes place, based on a predetermined ISO sensitivity setting value; and a driver which drives the solid-state imaging device in the drive mode selected by the controller.

Description

  The present invention relates to a digital camera and a solid-state imaging device driving method capable of shooting a high-quality subject image regardless of the brightness of a shooting scene even when shooting with ISO sensitivity fixed to a predetermined sensitivity.

  When a subject is photographed with a digital camera, the shutter speed, aperture opening amount, and ISO sensitivity are adjusted according to the photographing scene. For example, in the case of a bright shooting scene, the shutter speed is set to a high speed, the aperture opening amount is set to a small value, and the ISO sensitivity is set to a low value (for example, ISO 100). In the case of a dark scene, the shutter speed is set low, the aperture opening amount is large, and the ISO sensitivity is set high (for example, ISO 400).

  Since these adjustment parameters (shutter speed, aperture opening amount, ISO sensitivity) are related to each other, for example, when high-speed shooting is required and the shutter speed is manually set to a high speed, the ISO sensitivity is automatically set to a high value. The opening amount is set large. In addition, when a deep depth of field is required, the aperture opening amount is reduced. However, since the amount of incident light is reduced, the shutter speed is set low and the ISO sensitivity is set high.

  For example, in the case of a CCD type solid-state imaging device, the ISO sensitivity is set by the gain of the output stage amplifier. In the case of a bright scene with a large amount of received light (when the signal charge amount increases), the amplifier gain may be low, so the ISO sensitivity is set to a low sensitivity. In a dark scene where the amount of received light is small, the ISO sensitivity is set to a high sensitivity in order to amplify the signal amount by increasing the amplifier gain. However, when the amplifier gain is increased, the noise component is also amplified in the same manner as the signal, so that the subject image becomes a noisy image.

  For this reason, in the prior art described in Patent Document 1, when the amplifier gain is increased, the solid-state image sensor is driven so that the amount of noise generated in the solid-state image sensor is reduced. In this prior art, the number of standby packets during signal charge transfer is reduced to reduce the amount of noise.

  However, in this prior art, when the ISO sensitivity is fixed at a predetermined sensitivity, the amplifier gain is determined and the number of standby packets is also determined. Therefore, when shooting with the ISO sensitivity fixed to a predetermined sensitivity, the quality of the subject image depends on the brightness of the shooting scene.

  As a conventional technique for changing the driving method of the solid-state imaging device in accordance with the photographing mode, there is Patent Document 2 below. However, the imaging mode in this prior art means an all-pixel readout mode, a 2-line thinning mode, a frame readout mode, and the like, and is not an imaging mode according to brightness, but driving when the ISO sensitivity is fixed to a predetermined sensitivity. There is no description about the change of the method.

JP 2004-221339 A Japanese Patent Laid-Open No. 2001-128066

  SUMMARY OF THE INVENTION An object of the present invention is to provide a digital camera and a solid-state image sensor driving method capable of shooting a high-quality subject image regardless of the brightness of the shooting scene even when shooting with the ISO sensitivity fixed to a predetermined sensitivity. There is.

  The digital camera of the present invention includes a solid-state imaging device in which a plurality of pixels are arranged in a two-dimensional array on the surface of a semiconductor substrate, receives incident light from a subject, and outputs a captured image signal of the subject, and a predetermined ISO sensitivity. Control means for selecting a drive mode according to the brightness of the subject from among a plurality of drive modes prepared in advance for shooting based on a set value, and the solid-state imaging according to the drive mode selected by the control means Drive means for driving the element.

  The solid-state imaging device driving method according to the present invention drives a solid-state imaging device in which a plurality of pixels are arranged in a two-dimensional array on the surface of a semiconductor substrate, receives incident light from a subject, and outputs a captured image signal of the subject. A method for driving the solid-state imaging device by selecting a driving mode corresponding to the brightness of the subject from a plurality of driving modes prepared in advance for performing shooting based on a predetermined ISO sensitivity setting value. It is characterized by.

  According to the present invention, even when shooting with ISO sensitivity fixed to a predetermined sensitivity, a high-quality subject image can be shot regardless of the brightness of the shooting scene.

It is a functional block diagram of the digital camera which concerns on one Embodiment of this invention. It is a surface schematic diagram of the solid-state image sensor shown in FIG. It is a flowchart which shows the imaging procedure of 1st Embodiment which the signal processing part shown in FIG. 1 performs. FIG. 3 is a simplified diagram of the pixel array (color filter array) shown in FIG. 2. FIG. 5 is a diagram showing a state in which signal charges are read out from every other pixel row from the state of FIG. 4 to a vertical charge transfer path. FIG. 6 is a diagram showing a state where signal charges on the vertical charge transfer path are transferred in two stages in the vertical direction from the state of FIG. 5. FIG. 7 is a diagram illustrating a state in which signal charges are read from the remaining pixel rows to the vertical charge transfer path from the state of FIG. 6. FIG. 8 is a diagram illustrating a state in which vertical transfer is performed in the state of FIG. 7 and signal charges on the horizontal charge transfer path are horizontally transferred to the output side. It is a figure which shows a mode that a signal charge is transferred from a line memory to the horizontal charge transfer path emptied by the horizontal transfer of FIG. It is a figure which shows the mode of the pixel mixing performed on a horizontal charge transfer path. It is a simplified diagram of a pixel arrangement for explaining a wide dynamic range driving method. It is a timing chart explaining a wide dynamic range drive method. It is a flowchart which shows the imaging procedure of 2nd Embodiment of this invention. It is a timing chart explaining the example which changes a dynamic range width with a wide dynamic range drive method. It is a flowchart which shows the imaging procedure of 3rd Embodiment of this invention. It is explanatory drawing of 4 pixel mixing and 8 pixel mixing. It is a flowchart which shows the imaging procedure of 4th Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a functional block diagram of a digital still camera according to an embodiment of the present invention. The digital still camera 1 controls a CCD type solid-state imaging device 100, a photographic lens 2, an aperture 3, a mechanical shutter 4, and a solid-state imaging device 100 that constitute a photographic optical system disposed in front of the solid-state imaging device 100. In addition, a signal including an AFE & TG unit (AFE: analog front end, TG: timing generator) 5 that processes an output signal of the solid-state imaging device 100 and a CPU (central processing unit) that performs overall control of the digital still camera 1 as a whole. A processing unit 6, a drive control unit 7 that controls the above-described photographing optical system, a flash light emitting unit 8 that emits flash light to the subject, and a light receiving unit 9 that receives reflected light from the subject of the flash light. Prepare.

  The drive control unit 7 and the AFE & TG unit 5 are respectively connected to the signal processing unit 6 and controlled by the signal processing unit 6. The flash light emitting unit 8 and the light receiving unit 9 are also connected to the signal processing unit 6, and the flash light emitting unit 8 is controlled by the signal processing unit 6 that detects the amount of light received by the light receiving unit 9.

  The signal processing unit 6 further includes an operation unit 11 for inputting an operation instruction (including shutter operation) from a user, an external memory 12 for storing photographed subject image data, and a liquid crystal display unit provided on the back of the camera. 13 and an input / output (I / O) unit 14 connected to an external device (not shown).

  The AFE & TG unit 5 includes a CDS unit 5a that performs correlated double sampling processing on an analog captured image signal output from the solid-state imaging device 100, a VGA unit 5b that performs variable gain control, and an A / D unit 5c that converts digital signals. And a timing generator TG unit 5d that generates and outputs various drive pulse signals (vertical transfer pulse and readout pulse φV, horizontal transfer pulse φH, line memory control pulse φLM) to the solid-state imaging device 100.

  FIG. 2 is a schematic view of the surface of the CCD solid-state imaging device 100 shown in FIG. In the solid-state imaging device 100, a plurality of photodiodes (portions shown by diagonal squares in the drawing) 101 are arranged in a two-dimensional array on the surface portion of a semiconductor substrate.

  When the odd-numbered photodiode group is the first pixel group and the even-numbered photodiode group is the second pixel group, the first pixel group and the second pixel group are ½ pixels in both the vertical and horizontal directions. They are formed by shifting the pitch and have a so-called honeycomb pixel arrangement as a whole.

  If only the first pixel group is viewed, the pixels 101 are arranged in a square lattice, and the color filters of the three primary colors of red (R), green (G), and blue (B) are arranged on each pixel in a Bayer arrangement. Even when only the second pixel group is viewed, the pixels 101 are arranged in a square lattice, and the color filters of the three primary colors of red (R), green (G), and blue (B) are Bayer arranged on each pixel.

  A vertical charge transfer path (VCCD) 102 is formed to meander along each pixel column, and a horizontal charge transfer path (HCCD) 103 is formed along the transfer direction end of each vertical charge transfer path 102 for horizontal charge transfer. An amplifier 104 is provided at the output end of the path 103 to output a voltage value signal corresponding to the amount of signal charge transferred as a captured image signal. In addition, a line memory 105 having a buffer area for each vertical charge transfer path 102 is provided between the transfer direction end of each vertical charge transfer path 102 and the horizontal charge transfer path 103.

  The line memory 105 is a line memory as described in, for example, Japanese Patent Application Laid-Open No. 2002-112119 and Japanese Patent Application Laid-Open No. 2002-112122, and is received from the vertical charge transfer path 102 in accordance with a line memory control pulse (φLM). The signal charge is temporarily held, and the held signal charge is transferred to the horizontal charge transfer path 103 in accordance with the transfer timing of the horizontal charge transfer path 103. Thereby, for example, the signal charge of a certain R pixel (the pixel on which the color filter R is mounted) and the signal charge of the R pixel diagonally to the lower left of the R pixel are transferred horizontally as will be described in detail later. Pixel addition can be performed on the path 103.

  Each pixel 101 is provided with four transfer electrodes for each pixel. Of the two central transfer electrodes adjacent to the pixel, one of the transfer electrodes on the lower side (HCCD 103 side), for example, serves also as a readout electrode. Yes. The readout electrode for the first pixel group is commonly applied to the readout electrode of the first pixel group, and the readout pulse for the second pixel group is applied to the readout electrode of the second pixel group. . In the figure, an arrow that protrudes diagonally downward to the right from each pixel 101 indicates the signal charge readout direction and readout position.

  Although the terms “vertical” and “horizontal” have been described, this means only “one direction” along the surface of the semiconductor substrate and “a direction substantially perpendicular to the one direction”.

  FIG. 3 is a flowchart showing an imaging procedure executed by the CPU of the signal processing unit 6 shown in FIG. When a power switch (not shown in FIG. 1) is turned on, a captured image signal is output from the solid-state imaging device 100 at a predetermined cycle, for example, 30 frames of captured image signals per second. The captured image signal of each frame is taken into the signal processing unit 6 through the AFE & TG unit 5 and is displayed on the LCD display unit 13 as a through image after being subjected to known image processing.

  Under such a state, the CPU 6 analyzes the captured image signal output from the solid-state imaging device 100, determines the focal distance to the subject, and adjusts the focus of the photographing lens 2 via the drive unit 7. The shutter speed and the aperture opening amount are determined, and the ISO sensitivity is set to a required fixed value. Whether the brightness data (EV value) of the subject obtained by analyzing the captured image signal is smaller than “7”, between “7” and “13”, or larger than “13”. Determine (step S1).

  As a result of this determination, if the EV value is smaller than “7”, that is, in the case of a dark shooting scene, the process proceeds to step S2, and if the EV value is between “7” and “13”, that is, shooting with normal brightness. If it is a scene, the process proceeds to step S3. If the EV value is larger than “13”, that is, if the scene is bright, the process proceeds to step S4.

  In each of Steps S2, S3, and S4, as will be described in detail later, a driving method of the solid-state imaging device 100 corresponding to the brightness of the shooting scene is set, and the process proceeds to Step S5.

  In step S <b> 5, photographing processing is performed according to the driving method of the image sensor 100. For example, when the CPU 6 drives the solid-state imaging device 100 by the driving method set through the AFE & TG unit 5 and detects the full press of the shutter release button input from the operation unit 11, the captured image output from the solid-state imaging device 100. Capture the signal. Then, the captured image signal is subjected to image processing according to the driving method of the solid-state imaging device 100, converted into JPEG image data, and stored in the external memory 12.

  In this embodiment, there are three types of driving methods for the solid-state imaging device 100: the pixel mixture driving mode set in step S2, the normal all-pixel driving mode set in step S3, and the wide dynamic range driving mode set in step S4. Drive timing data that is prepared in advance and that realizes each drive mode is stored in a ROM (not shown) in the CPU 6. Then, the driving timing data to be used is read out according to the brightness of the subject and transferred to the timing generator 5d, and the solid-state imaging device 100 is driven at the driving timing.

  First, the all pixel drive mode set in step S3 will be described. FIG. 4 is a simplified diagram of a pixel array (color filter array) of the solid-state imaging device 100 shown in FIG. As shown in the figure, in the solid-state imaging device 100 according to the present embodiment, every other pixel row extending in the direction of 45 degrees diagonally to the upper right has a G color filter for every other row, and the remaining pixel rows are every other row. The color filter (R, B) of the same color is alternately provided for every two consecutive pixels.

  V1 to V8 in the figure indicate vertical transfer electrodes. The transfer electrodes V1, V3, V5 and V7 are also used as readout electrodes. As shown in FIG. 5, when a read pulse is applied to the read electrodes V1 and V5, a signal charge (signal charge of the R pixel) corresponding to the amount of light received by the pixel is included in a potential packet formed under the read electrodes V1 and V5. Is “R”, the signal charge of the G pixel is “G”, and the signal charge of the B pixel is “B”).

  FIG. 6 shows a state where the vertical transfer pulse φV is applied to the transfer electrodes V1 to V8 in the state of FIG. 5 and the signal charge on the vertical charge transfer path is transferred by two stages in the vertical direction. In the state of FIG. 6, the signal charge on the vertical charge transfer path is stored in a potential packet below the transfer electrodes V3 and V7.

  Here, when a read pulse is applied to the read electrodes V3 and V7, the signal charge is read into the potential packet below the electrodes V3 and V7 from the remaining pixels where the signal charge is not read in FIG. It will be in the state shown. That is, the signal charges of the odd-numbered and even-numbered pixel rows adjacent vertically are individually arranged in a horizontal row.

  Thereafter, in this state, the vertical charge transfer path is driven to transfer in the vertical direction, whereby the signal charge is transferred while maintaining the state of one horizontal line, and the horizontal charge transfer path 103 is passed through the line memory 105 as shown in FIG. Is transferred.

  When individual signal charges in one horizontal row are transferred to the horizontal charge transfer path 103, vertical transfer is temporarily stopped, and the horizontal signal transfer path 103 is transferred in the horizontal direction to transfer individual signal charges in the horizontal row to the amplifier 104. The voltage value signals of the individual signal charges are individually output as captured image signals.

  Then, after the horizontal charge transfer path 103 becomes empty, the operation of performing vertical transfer again and putting the individual signal charges in the next horizontal row into the horizontal charge transfer path 103 is repeated as shown in FIG. Thus, each captured image signal of each pixel 101 for one screen is individually output.

  In the all-pixel drive mode of this solid-state imaging device, as described above, a voltage value signal corresponding to the signal charge amount detected by each pixel 101 is individually output from the amplifier 104, so that a high-definition image of the subject is reproduced. be able to.

  Next, the pixel mixture drive mode (pixel addition drive mode) set in step S2 will be described. As shown in FIGS. 8 and 9, the process is the same as the above-described all-pixel driving method until each horizontal row of individual signal charges is transferred to each buffer area of the line memory 105. The pixel mixture drive mode of the present embodiment is different in drive timing at the time of transfer from the line memory 105 to the horizontal charge transfer path 103.

  For example, the line memory 105 has a wiring connection in which different transfer pulses can be applied to every other transfer electrode (control electrode) provided in each buffer region in one horizontal row. For example, a wiring connection is made in which the pulse φLM1 is applied to every other control electrode, and the pulse φLM2 is applied to the remaining every other control electrode.

  In the all pixel drive mode, the pulse applied to the line memory (LM) 105 is set to φLM1 = φLM2, so that all the buffer areas of the line memory 105 are driven in the same manner. In this pixel mixed drive mode, φLM1 ≠ φLM2, and the drive timing is changed.

  As shown in FIG. 8, in the pixel array (color filter array) shown in FIG. 2,... GGBBGGBBGGBB. Are alternately transferred in the vertical direction. That is, two signal charges of the same color are arranged side by side.

  Therefore, first, as shown in FIG. 10A → FIG. 10B, every other signal charge of each buffer on the line memory 105 is transferred to the horizontal charge transfer path 103, and then FIG. ), The horizontal charge transfer path 103 is transferred by one stage in the horizontal direction. As a result, the color of the signal charge remaining on the line buffer 105 and the color of the signal charge transferred by one stage in the horizontal charge transfer path 103 are aligned in the same color. At this time, as shown in FIG. 10D, by transferring the signal charges on the line memory 105 to the horizontal charge transfer path, the signal charges for two pixels of the same color are added (mixed) on the horizontal charge transfer path. The

  Thereafter, the horizontal charge transfer path 103 is transferred in the horizontal direction, and a voltage value signal corresponding to the signal charge amount obtained by adding two pixels is output from the amplifier 104 as a picked-up image signal. When the horizontal charge transfer path becomes empty, Transfer is performed to transfer the next horizontal row of signal charges from the vertical charge transfer path to the line memory 105. By repeating such an operation, a captured image signal obtained by adding two pixels is output from the solid-state imaging device 100.

  In this pixel mixture drive mode, signal charges detected by two adjacent pixels of the same color are added together and output as a picked-up image signal, so that the image resolution of the subject image is lower than in the all-pixel drive mode. Since the amount of charge is increased by two pixels, it is possible to obtain a highly sensitive subject image that is not crushed black even in a dark scene.

  Next, the wide dynamic range drive mode set in step S4 will be described. In the pixel mixed drive mode described with reference to FIG. 10, for example, a certain signal charge B and a signal charge B on the upper right are added and output, but two pixels (2) that obtain these two signal charges B ( In the photodiode), exposure is started at the same time, exposure is ended at the same time, and the solid-state imaging device is driven at a drive timing with the same exposure period. On the other hand, in the wide dynamic range driving mode of the present embodiment, the solid-state imaging device is driven at a driving timing for changing the exposure period of two pixels, and each voltage value signal (imaging signal) of the signal charges having two different exposure times is used. ) Are individually output, and then two pixels of the long-exposure imaging signal and the short-exposure imaging signal are added by signal processing.

  In the present embodiment, in the same color filter array as in FIG. 4, pixels having transfer electrodes V1 and V5 as readout electrodes are pixels for short exposure, and pixels having transfer electrodes V3 and V7 as readout electrodes are pixels for long exposure. And FIG. 11 is a diagram in which signal charges due to long exposure are indicated by capital letters R, G, and B, and signal charges due to short exposure are indicated by small letters r, g, and b.

  FIG. 12 is a timing chart showing the wide dynamic range drive mode. Under the mechanical shutter “open” state, at the OFD (overflow drain) pulse application stop timing x, exposure starts at each of the long-time exposure pixel and the short-time exposure pixel, and accumulation of signal charges starts.

  When the read pulse 21 is applied to the read electrodes V1 and V5 at the next arbitrary timing y, the signal charge accumulated in the short-time exposure pixel between the timings x to y is read to the vertical charge transfer path. It will be. Since no readout pulse is applied to the readout electrodes V3 and V7 at the timing y, signal charge accumulation from the timing x continues in the long-time exposure pixels. Accumulation of signal charges starts again in the short-time exposure pixels that are once “empty” at the timing y.

  At the next timing z determined by the shutter speed, the mechanical shutter is “closed”, and the exposure of the long exposure pixels and the short exposure pixels is completed. Next, when the vertical charge transfer path is driven by the high-speed sweep pulse 22, the signal charge from timing x to y read from the short-time exposure pixel to the vertical charge transfer path at timing y is discarded.

  Thereby, signal charges at timings x to z (exposure period T) are accumulated in the long-time exposure pixels, and signal charges at timings y to z (exposure period t) are accumulated in the short-time exposure pixels. Will be.

  4 to 9 described in the all pixel drive mode, for example, in a reading process of a certain pixel row corresponding to FIG. 8, the picked-up image signals corresponding to the respective signal charge amounts in order of... GBbGgBbG. Output from the solid-state imaging device 100, and in the readout processing of the next row, a captured image signal corresponding to each signal charge amount is output from the solid-state imaging device 100 in the order of... RGgRrGgR. The picked-up image signal output from the solid-state image sensor 100 is subjected to signal processing by the signal processing unit 6 at the subsequent stage. At this time, two continuous pixels of the same color (two pixels of the same color arranged in an oblique direction in FIG. 11) are picked up. The image signal is subjected to pixel addition (R + r, G + g, B + b), and a wide dynamic range captured image signal is generated.

  As a result, even when the shooting scene is bright, it is possible to shoot a subject image that does not white out.

  As described above, according to the present embodiment, even when shooting with the ISO sensitivity fixed to a predetermined sensitivity, by changing the driving method of the solid-state imaging device 100 according to the brightness of the subject, it is possible to improve the quality of the subject. Images can be taken regardless of the brightness of the subject.

  FIG. 13 is a flowchart showing an imaging procedure according to another embodiment of the present invention. In the imaging procedure of FIG. 3, three methods of a pixel mixing driving mode, an all-pixel driving mode, and a wide dynamic range driving mode are prepared as driving methods of the solid-state imaging device. In this embodiment, a wider dynamic range driving mode is further provided. The dynamic range is subdivided into three modes of 200% mode, 400% mode, and 800% mode according to subject brightness.

  That is, if the EV value is greater than “13” as a result of the determination in step S1, the EV value in step S1a indicates whether the EV value is “13” or the EV value is “14”. It is determined whether it is “15”.

  If the EV value = 13, the process proceeds to step S4a to set the dynamic range 200% mode. If the EV value = 14, the process proceeds to step S4b to set the dynamic range 400% mode, and the EV value = 15. In this case, the process proceeds to step S4c, the dynamic range 800% mode is set, and the process proceeds to step S5. Other steps S2 and S3 are the same as those in the embodiment of FIG.

  FIG. 14 is a diagram illustrating drive timing for switching between the dynamic range 200% mode, 400% mode, and 800% mode. The dynamic ranges 200%, 400%, and 800% are realized by switching the timing y in FIG. 12 to the timings y1, y2, and y3 with respect to the timings x and z.

  That is, by setting a timing y1 that is T / 2, for example, with respect to the exposure period T of the timings x to z, a short exposure period T200 that realizes a dynamic range of 200% is determined. Further, for example, a short exposure period T400 that realizes a dynamic range of 400% by setting a timing y2 that becomes T / 4 is determined, and a short exposure that realizes a dynamic range of 800% by setting a timing y3 that becomes T / 8. Period T800 is decided.

  This makes it possible to automatically set a fine dynamic range even when the shooting scene is too bright, and to obtain a high-quality subject image without overexposure.

  FIG. 15 is a flowchart showing an imaging procedure according to still another embodiment of the present invention. In the imaging procedure of FIG. 13, the wide dynamic range driving mode is subdivided into three in the driving method of the solid-state imaging device of FIG. 3, but in the present embodiment, the pixel mixture driving mode of FIG. The number of added pixels is subdivided into three.

  That is, in this embodiment, when the EV value of the subject is smaller than “7”, the process proceeds to step S1b. When the EV value = 5 or 6, the process proceeds to step S2a to set the two-pixel mixed drive mode, and the EV value = In the case of 3 or 4, the process proceeds to step S2b to set the 4-pixel mixed drive mode, and in the case of EV value = 1 or 2, the process proceeds to step S2c to set the 8-pixel mixed drive mode, and the process proceeds to step S5. Other steps S3 and S4 are the same as those in the embodiment of FIG.

  The two-pixel mixed drive mode is the same as the two-pixel addition on the horizontal charge transfer path described in FIG. 10, and step S2a in FIG. 15 is the same as step S2 in FIG.

  In the four-pixel mixed drive mode in step S2b, for example, two G signal charges 51 and 52 that are adjacent in the vertical direction along a certain pixel column in FIG. 16 are read out to the vertical charge transfer path, and on this vertical charge transfer path. It will mix.

  At this time, the B signal charge 61 between the G signal charges 51 and 52 is not read out to the vertical charge transfer path, but after the G signal charges 51 and 52 are read, mixed, and output from the amplifier 104, Read, mix and output. Also on the adjacent vertical charge transfer paths, the two G signal charges 53 and 54 are subjected to pixel mixing.

  Then, the G signal charge (51, 52) and the G signal charge (53, 54) mixed in two pixels on the vertical charge transfer path are added on the horizontal charge transfer path as described in FIG. The signal charges are mixed and then output from the amplifier 104. Similarly, the G signal charges 55, 56, 57, and 58 are mixed from four pixels of the same color and output from the amplifier 104. Similarly, the B signal charge and R signal charge of other colors are mixed by four pixels and output from the amplifier 104.

  In this case, instead of the 8-phase driving electrodes V1 to V8 shown in FIG. 4 as the vertical transfer electrodes, the 16-phase driving electrodes V1 to V16 are provided on the vertical charge transfer path as shown in FIG. The vertical drive of pixel addition becomes easy. When the electrode wiring for 16-phase driving is necessary, when it is necessary to perform 8-phase driving (for example, when the driving method described in FIGS. 4 to 8 is performed), the same pulse φV1 is applied to the electrode V1 and the electrode V9. By applying the same pulse φV2 to V2 and V10, and so on, there is no problem and 8-phase driving is realized.

  For example, in FIG. 16, the adjacent G signal charges 51, 52, 55 and 56 of the same color are mixed on the vertical charge transfer path, and the G signal charge 53 is also set on the adjacent vertical charge transfer path. , 54, 57, 58 are mixed, and these are mixed on the horizontal charge transfer path to perform 8-pixel addition. Similarly, 8-pixel addition is performed for the B signal charge and the R signal charge.

  In this way, as the number of adjacent pixels of the same color increases, the signal charge amount with high sensitivity can be obtained even in a dark scene, and the image resolution decreases, but a high-quality subject image can be obtained. It becomes.

  FIG. 17 is a flowchart showing an imaging procedure according to still another embodiment of the present invention. The present embodiment is an imaging procedure that combines the embodiment of FIG. 13 and the embodiment of FIG. Depending on the brightness of the shooting scene, it is possible to appropriately select the driving method of the solid-state imaging device, that is, the driving mode, depending on the brightness of the shooting scene. Therefore, it is possible to always obtain a high-quality subject image.

  In the embodiment described above, the CCD type solid-state imaging device shown in FIG. 2, that is, a first pixel group in a square lattice arrangement in which the color filter array is a Bayer arrangement, and a ½ pixel pitch in the vertical and horizontal directions. A solid-state imaging device having a honeycomb pixel arrangement in which a second pixel group having a square lattice arrangement and a second pixel group having the same color filter arrangement as a Bayer arrangement is mixed has been described as an example. It is not limited to a solid-state image sensor. For example, it can be applied to a solid-state imaging device in which each pixel is arranged in a square lattice, and even if it is not a CCD type, it can read out the same color signal by mixing pixels, and can also output the same color signal with different exposure periods. The present invention can be applied to any solid-state imaging device that can be read by mixing.

  In the above-described embodiment, the CPU automatically sets the drive mode of the solid-state imaging device according to the brightness of the subject after the CPU sets the ISO sensitivity to a predetermined sensitivity based on the exposure condition of the subject. When the user manually sets the ISO sensitivity to a predetermined sensitivity, the CPU side may automatically set the drive mode of the solid-state imaging device according to the brightness of the subject.

  As described above, in the digital camera and the solid-state image sensor driving method according to the embodiment, the plurality of pixels are arranged in a two-dimensional array on the surface of the semiconductor substrate and receive the incident light from the subject, and the captured image of the subject A digital camera equipped with a solid-state imaging device that outputs a signal and a driving method of the solid-state imaging device, wherein the brightness of the subject is selected from a plurality of driving modes prepared in advance for performing shooting based on a predetermined ISO sensitivity setting value. The solid-state imaging device is driven by selecting a driving mode according to the height.

  In the digital camera and the solid-state image sensor driving method according to the embodiment, detection signals of a plurality of adjacent pixels selected when the brightness of the subject is dark and the EV value representing the brightness is smaller than a first predetermined value are detected. A pixel mixture drive mode for adding and outputting, and a long-time exposure pixel and a short-time exposure pixel that are selected when the subject is bright and the EV value is greater than a second predetermined value that is greater than the first predetermined value. Each of the detection signals is output individually, and then is selected when the wide dynamic range driving mode is added by signal processing, and the EV value is between the first predetermined value and the second predetermined value. An all-pixel drive mode in which signals are read independently is prepared in advance as the plurality of drive modes.

  In the driving method of the digital camera and the solid-state imaging device according to the embodiment, as the pixel mixture driving mode, a plurality of pixel mixture driving modes having different numbers of pixels to be added are prepared according to the brightness of the subject. Features.

  Further, in the driving method of the digital camera and the solid-state imaging device according to the embodiment, as the wide dynamic range driving mode, a plurality of wide dynamics having different ratios of the exposure period of the long exposure pixel and the exposure period of the short exposure pixel are used. A range driving mode is prepared according to the brightness of the subject.

  As a result, even when shooting is performed with the ISO sensitivity fixed to a predetermined value, a high-quality subject image can be obtained regardless of the brightness of the subject.

  The digital camera and the solid-state imaging device driving method according to the present invention change the driving method (driving timing) of the solid-state imaging device according to the brightness of the shooting scene even when the ISO sensitivity setting is fixed to a predetermined sensitivity. Digital still cameras, digital video cameras, camera-equipped mobile phones, camera-equipped electronic devices, omnidirectional imaging devices that place multiple digital cameras and shoot 360-degree images, etc. It is useful to apply to.

DESCRIPTION OF SYMBOLS 1 Digital still camera 2 Shooting lens 3 Aperture 4 Mechanical shutter 5 AFE & TG part 5a CDS part 5b VGA part 5c A / D part 5d TG (drive means)
6 Signal processor (including CPU)
100 Solid-state image sensor 101 Pixel (photodiode)
102 Vertical charge transfer path (VCCD)
103 Horizontal charge transfer path (HCCD)
104 Output amplifier 105 Line memory

Claims (8)

  A plurality of pixels are arranged in a two-dimensional array on the surface of a semiconductor substrate, receive incident light from a subject, and output a picked-up image signal of the subject, and photographing based on a predetermined ISO sensitivity setting value Control means for selecting a drive mode according to the brightness of the subject from a plurality of drive modes prepared in advance, and drive means for driving the solid-state imaging device in the drive mode selected by the control means; Digital camera equipped with.   2. The digital camera according to claim 1, wherein when the brightness of the subject is dark and a value representing the brightness is smaller than a first predetermined value, detection signals of a plurality of adjacent pixels selected and added are output. Each of the adjacent long exposure pixel and the short exposure pixel that is selected when the brightness of the subject is bright and the value representing the brightness is greater than a second predetermined value that is greater than the first predetermined value. A wide dynamic range drive mode in which detection signals are output and added, and a value representing the brightness of the subject is selected between the first predetermined value and the second predetermined value, and the detection signal of each pixel is independent. A digital camera in which all pixel drive modes to be read out are prepared in advance as the plurality of drive modes.   3. The digital camera according to claim 2, wherein a plurality of pixel mixture drive modes having different numbers of pixels to be added are prepared as the pixel mixture drive mode according to the brightness of the subject.   4. The digital camera according to claim 2, wherein, as the wide dynamic range driving mode, a plurality of wide dynamics having different ratios between an exposure period of the long exposure pixel and an exposure period of the short exposure pixel. A digital camera in which a range driving mode is prepared according to the brightness of the subject.   A method of driving a solid-state imaging device in which a plurality of pixels are arranged in a two-dimensional array on the surface of a semiconductor substrate and receive incident light from a subject and output a captured image signal of the subject, and a predetermined ISO sensitivity setting value A solid-state image sensor driving method for driving the solid-state image sensor by selecting a drive mode corresponding to the brightness of the subject from among a plurality of drive modes prepared in advance for shooting based on the above.   6. The method of driving a solid-state imaging device according to claim 5, wherein detection signals of a plurality of adjacent pixels selected when the brightness of the subject is dark and a value representing the brightness is smaller than a first predetermined value are added. And a pixel mixture driving mode to be output, and a long-exposure pixel that is selected and close when the brightness of the subject is bright and the value representing the brightness of the subject is greater than a second predetermined value that is greater than the first predetermined value. A wide dynamic range driving mode for outputting and adding detection signals of short-time exposure pixels, and a value representing the brightness of the subject selected between the first predetermined value and the second predetermined value. A solid-state imaging device driving method in which an all-pixel driving mode for independently reading out pixel detection signals is prepared in advance as the plurality of driving modes.   The solid-state imaging device driving method according to claim 6, wherein a plurality of pixel mixture drive modes having different numbers of pixels to be added are prepared according to brightness of the subject as the pixel mixture drive mode. Device driving method.   8. The method for driving a solid-state imaging device according to claim 6, wherein a ratio between an exposure period of the long exposure pixel and an exposure period of the short exposure pixel is different as the wide dynamic range driving mode. A method for driving a solid-state imaging device, wherein a plurality of wide dynamic range drive modes are prepared according to the brightness of the subject.

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