JP2007088842A - Imaging apparatus, and method of driving imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus that generates a beautiful color image signal even at a dark place in the imaging apparatus having an imaging device in the color filter configuration of Bayer array, can form a high-grade live view color image or a moving picture, and to provide a method for driving an imaging device. <P>SOLUTION: When the imaging device is driven in a live view mode, or a moving picture mode, signal charge, which is generated by a plurality of pixels in which the same kinds of color filters are arranged in a plurality of pixels in which a plurality of kinds of color filters are arranged, is read to a plurality of vertical transmission sections each, and the read signal charge is added in a vertical direction for generating signal charge. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus that improves the S / N of a live view color image.

  In recent years, imaging devices such as digital cameras and video cameras have become more versatile and have higher image quality, and as with optical viewfinders, operations such as visual recognition of shooting standby images and subtle focus adjustments are performed on display devices. In response to the need, an imaging device having a live view function for displaying a shooting standby image (also referred to as a live view image) on an LCD monitor or the like has come into wide use.

  The live view operation usually reads out charges while performing pixel thinning at regular intervals from the image sensor, generates an image signal, and finally determines the angle of view in shooting, etc., and finally to an LCD monitor, EVF, etc. The operation mode to be displayed.

  On the other hand, in an imaging device represented by a CCD (Charge Coupled Device), high pixels and high density are accelerating. However, the photoelectric conversion amount per pixel is reduced, and the sensitivity is lowered. The signal level of the signal is lowered, resulting in a decrease in S / N. Particularly in the live view operation or the moving image shooting operation in which thinning-out reading is performed, since the S / N is significantly reduced and greatly affects the image reproducibility and image quality, the S / N is required to realize high-quality image formation. There is a need to improve. Various techniques for improving the S / N of live view images have been studied in the field of imaging devices.

For example, in an image pickup apparatus including an image pickup device having a color filter configuration in a vertical stripe arrangement, thinning is performed at regular intervals in the vertical direction to read out charges, and the read out charges are vertically added to generate an image signal. That is, there is a technique that compensates for a signal amount reduced by thinning by vertical addition and improves the S / N of a live view color image (see, for example, Patent Document 1).
JP 2000-308075 A

  As described above, various techniques for an imaging apparatus for improving the S / N of a live view image have been studied.

  The image pickup apparatus disclosed in Patent Document 1 compensates by vertically adding a signal amount reduced by thinning during a live view operation, thereby improving S / N. However, when photographing in a dark place or the like, the absolute amount of the incident light amount to the image sensor decreases, but such an absolute amount of the incident light amount is not compensated. In other words, it is considered difficult to obtain a beautiful live view color image when shooting in a dark place.

  Furthermore, the imaging device disclosed in Patent Document 1 relates to an imaging device including an imaging device having a color filter configuration with a vertical stripe arrangement. In recent years, an imaging device having a Bayer arrangement color filter configuration has been widely used. This does not suggest a technique for improving the S / N ratio of a live view color image in the imaging apparatus provided.

  The present invention has been made in view of the above problems, and in an imaging apparatus including an imaging device having a color filter configuration of a Bayer arrangement, a beautiful color can be obtained even in a dark place without causing an increase in cost and complexity of the imaging apparatus. An object of the present invention is to provide an imaging apparatus capable of generating an image signal and forming a high-quality live view color image or a moving image, and a driving method of the imaging element.

  The object is achieved by the invention described in any one of (1) to (9) below.

(1) a plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge;
A color filter configuration in which a plurality of types of color filters are arranged corresponding to the plurality of pixels, and at least one type of the color filters is arranged in a checkered pattern;
An image sensor having a plurality of vertical transfer units that vertically transfer the signal charges read from the plurality of pixels for each column;
Drive signal generating means for generating a drive control signal for controlling the drive of the image sensor;
A drive signal control means for controlling the operation of the drive signal generation means,
The drive signal control means is configured to output signal charges generated by the plurality of pixels having the same type of color filter among the plurality of pixels having the plurality of types of color filters. An image pickup apparatus that controls the operation of the drive signal generation unit so as to generate a signal charge by reading the signal charges to a plurality of vertical transfer units and adding the read signal charges in the vertical direction.

(2) The imaging device includes a display unit that displays an image captured by the imaging device based on an image signal read from the imaging device,
When the image pickup device is driven in a shooting standby mode and the generated image is displayed on the display means, or when the image pickup device is driven in a moving image mode to perform moving image shooting,
The drive signal control means is configured to output signal charges generated by the plurality of pixels having the same type of color filter among the plurality of pixels having the plurality of types of color filters. The above (1) is characterized in that the operation of the drive signal generating means is controlled so as to generate a signal charge by reading to a plurality of the vertical transfer units and adding the read signal charges in the vertical direction. The imaging device described.

  (3) The imaging apparatus according to (1) or (2), wherein the drive signal control unit controls the operation of the drive signal generation unit so as to change the number of additions.

  (4) The drive signal control means controls the operation of the drive signal generation means so as to change a display rate of the image displayed on the display means according to the number of additions. The imaging device according to (2) or (3) above.

(5) The imaging apparatus includes a substrate voltage generation unit that generates a substrate voltage for adjusting a saturation amount of the signal charge generated in the pixel,
The imaging apparatus according to any one of (1) to (4), wherein the substrate voltage generation unit generates the substrate voltage according to the number of additions.

(6) The imaging device includes photometric means for detecting the brightness of a subject;
An electronic shutter or an aperture for adjusting the exposure of the image sensor;
Exposure control means for controlling the operation of the electronic shutter or the diaphragm based on the detection result of the photometry means,
When displaying the image on the display means at a predetermined display rate according to the number of additions,
When the brightness of the subject detected by the photometry means exceeds a preset reference value,
The exposure control unit controls the electronic shutter or the aperture so that the shutter speed is increased or the aperture is decreased. The exposure control unit according to any one of the above (2) to (4), Imaging device.

(7) The imaging device includes photometric means for detecting brightness of a subject;
An amplifier for amplifying the image signal read from the image sensor;
Amplifier control means for controlling the operation of the amplifier based on the detection result of the photometry means,
When displaying the image on the display means at a predetermined display rate according to the number of additions,
When the brightness of the subject detected by the photometric means is below a preset reference value,
The imaging apparatus according to any one of (2) to (4), wherein the amplifier control unit controls the amplifier so as to increase an amplification degree of the amplifier.

(8) a plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge;
A color filter configuration in which a plurality of types of color filters are arranged corresponding to the plurality of pixels, and at least one type of the color filters is arranged in a checkered pattern;
A plurality of vertical transfer units that vertically transfer the signal charges read from the plurality of pixels for each column;
When reading the signal charge generated by the plurality of pixels,
Among the plurality of pixels in which the plurality of types of color filters are arranged, signal charges generated by the plurality of pixels in which the same type of color filter are arranged are respectively transferred to the plurality of the vertical transfer units. And a signal charge is generated by adding the read signal charges in the vertical direction.

  (9) The image pickup element driving method according to (8), wherein the addition is performed by changing the number of additions.

  In the inventions described in the above (1), (2), and (3), a plurality of types of color filters are arranged corresponding to a plurality of pixels, and at least one type of color filter is arranged in a checkered pattern. When an imaging device having an array of color filter configurations is driven in a shooting standby mode (also referred to as a live view mode) or a moving image mode, the same type among a plurality of pixels in which a plurality of types of color filters are arranged The signal charges generated by a plurality of pixels in which the color filters are arranged are read out to a plurality of vertical transfer units, respectively. That is, since signal charges of the same color are read out to one vertical transfer unit, addition can be performed without losing color information.

  In addition, the signal charges generated in most pixels are read without thinning out, and the read signal charges are added, so that even when shooting in a dark place, the reduced signal amount is reduced. It is possible to compensate, and it is possible to obtain a beautiful live view color image or a moving image with a good S / N.

  In addition, since the number of additions can be changed, by selecting the optimum number of additions according to the brightness of the subject, the reduced signal amount can be appropriately adjusted even when shooting in dark places. It is possible to compensate, and it is possible to obtain a beautiful live view color image or a moving image with a good S / N.

  In addition, since the number of additions can be changed, the number of additions can be used as one parameter for exposure control.

  In the inventions described in the above (8) and (9), a plurality of types of color filters are arranged corresponding to a plurality of pixels, and at least one type of color filter is arranged in a checkered pattern. When reading out signal charges generated by a plurality of pixels in an imaging device having a configuration, among a plurality of pixels having a plurality of types of color filters, a plurality of pixels having the same type of color filter are arranged. The signal charges generated by the pixels are read out to a plurality of vertical transfer units, respectively. That is, since signal charges of the same color are read out to one vertical transfer unit, addition can be performed without losing color information.

  In addition, the signal charges generated in most pixels are read without thinning out, and the read signal charges are added, so that even when shooting in a dark place, the reduced signal amount is reduced. It is possible to compensate, and it is possible to obtain a beautiful live view color image or a moving image with a good S / N.

  In addition, since the number of additions can be changed, by selecting the optimum number of additions according to the brightness of the subject, the reduced signal amount can be appropriately adjusted even when shooting in dark places. It is possible to compensate, and it is possible to obtain a beautiful live view color image or a moving image with a good S / N.

  As a specific embodiment of the imaging apparatus according to the present invention, a digital camera is typical, but a mobile phone with a camera, a digital video camera, and the like are also included.

  The appearance of a digital camera that is one of the representative embodiments of the imaging apparatus according to the present invention will be described with reference to FIG. 1A is a side view of the digital camera 1 according to the present invention, and FIG. 1B is a rear view. As shown in FIG. 1A, the digital camera 1 is composed of a camera body 2 and a lens unit 3.

  The lens unit 3 includes a photographing lens having a macro zoom (not shown), a diaphragm, a shutter, and the like.

  The camera main body 2 includes an LCD monitor 211 formed of an LCD (Liquid Crystal Display), an EVF (Electronic View Finder) 210, and external connection terminals for connecting the digital camera 1 to a personal computer (not shown). The image signal captured by the CCD area sensor 50 described later is subjected to predetermined signal processing, image display on the LCD monitor 211 and EVF 210, and image recording on a recording medium such as a memory card 277 described later, Alternatively, processing such as image transfer to a personal computer is performed.

  As shown in FIG. 1A, a built-in flash 212 that is hopped up when necessary is provided on the upper surface of the camera body 2.

  Further, as shown in FIG. 1B, an LCD for displaying a photographed image, reproducing a recorded image, or displaying a GUI such as a menu screen or various statuses is displayed at a substantially central portion on the back of the camera body 2. A monitor 211 and an EVF 210 are provided. In other words, the LCD monitor 211 and the EVF 210 function as display means in the imaging apparatus according to the present invention.

  As shown in FIG. 1B, a shutter setting button 203 for setting the operation mode of the digital camera 1 is provided near the shutter button 201 on the upper surface of the camera body 2. . The operation mode of the digital camera 1 set by the mode setting dial 203 includes “still image mode”, “moving image mode”, “reproduction mode”, and the like.

  For example, the still image mode is a mode for taking a picture from the shooting standby state (live view state) to the shooting through the exposure control process, and the moving image mode is the CCD area sensor 50 in the shooting standby state (live view state). In this mode, moving image shooting is performed based on the moving image signal read out from. The playback mode is a mode in which the captured image recorded on the memory card 277 is played back and displayed on the LCD monitor 211 or EVF 210.

  Further, as shown in FIG. 1B, a digital switch button 209 for changing the zoom magnification of the digital zoom is provided near the main switch 202, as shown in FIG. ing.

  Further, as shown in FIG. 1B, a menu button 207 for displaying a menu on the LCD monitor 211 and an image on the LCD monitor 211 near the menu button 207 are displayed at the lower back of the camera body 2. Is provided with a quick view button 208.

  Further, a selection / determination button 206 for performing various settings is provided at a substantially central portion on the back surface of the camera body 2. The selection / determination button 206 includes a jog dial (cross key) 204 for selecting various settings and a determination button 205 for confirming the setting selected by the jog dial (cross key) 204.

  Next, the configuration of a CCD area sensor 50 (hereinafter abbreviated as “CCD 50”) corresponding to the image sensor in the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram showing the configuration of the CCD 50 according to the present invention.

  As shown in FIG. 3, in the CCD 50, photodiodes 51 corresponding to the pixels in the present invention are arranged in a two-dimensional matrix in the light receiving area 52, and each photodiode 51 has R (red) light and G (green). ) Light and B (blue) light transmission filters arranged in a checkered pattern (Bayer array) color area imaging sensor photoelectrically convert the subject light image formed by the lens unit 3 to R (red) ) The image signal of each color component of light, G (green) light, and B (blue) light (signal composed of a signal sequence of pixel signals received in units of pixels) is generated.

  As shown in FIG. 3, the photodiode 51 is connected to a vertical shift register 53 corresponding to the vertical transfer unit in the present invention, and the vertical shift register 53 is connected to a horizontal shift register 54 provided below the CCD 50. Then, the signal charges accumulated in the photodiode 51 are amplified by the output unit 55 via these parts and output to the outside.

  Here, with reference to FIG. 5, a signal charge reading operation performed in the live view mode or the moving image mode in the CCD 50 having such a configuration will be described. FIG. 5 is a time chart of the drive control signal of the CCD 50. Note that the signal reading operation performed in the moving image mode is the same as the signal reading operation performed in the live view mode, and thus description thereof is omitted.

  In the present invention, when the CCD 50 is driven in the live view mode or the moving image mode, the signal charge of the same color is read out to one vertical shift register 53, and the read signal charges are added to increase the signal amount. Even when shooting in a dark place, the reduced signal amount can be compensated, and a beautiful live view color image or moving image with good S / N can be generated.

  As shown in FIG. 5, the signal charge generated by the photodiode 51 is read to the vertical shift register 54 by a charge read pulse φSG1 output at time t1 and t2 from a later-described timing generator 246 for driving the CCD 50. At this time, as shown in FIG. 3, the vertical shift register 53 of each column outputs, for example, the R signal and the G signal of the even-numbered row to the first column and the second column, respectively, and the third column, the fourth column. Read out electrodes (not shown) of the respective photodiodes 51 so that odd-numbered G signals and B signals are output, and R signals, G signals and G signals, and B signals are alternately output every two columns. Wired. In this way, the signal charge of any one color of the R signal, G signal, and B signal is read out to the vertical shift register 53 of each column.

  When the signal charge is read to the vertical shift register 53, the timing generator 246 next outputs the vertical transfer pulses φV1 to φV4, for example, five times continuously from time t3 to t4 as shown in FIG. Five signal charges per column are transferred from the vertical shift register 53 to the horizontal shift register 54. During this time, the horizontal transfer operation is stopped by stopping the output of the horizontal transfer pulses φH1 and φH2. The five signal charges transferred from the vertical shift register 53 to the horizontal shift register 54 in this way are added in the horizontal shift register 54.

  When the addition is completed, as shown in FIG. 5, the output of horizontal transfer pulses φH1 and φH2 is restarted from time t4, and the added signal charges are transferred in the horizontal direction. The horizontally transferred signal charge is output to the outside through the output unit 55. By repeating such an operation, a charge signal corresponding to one screen generated by each photodiode 51 is added by 5 pixels in the vertical direction and output from the CCD 50.

  Further, the number of additions can be changed according to, for example, the brightness of the subject under the control of a camera control CPU 291 described later.

  The substrate voltage Vs is a voltage for adjusting the saturation level of the signal charge generated by the photodiode 51, and an optimum voltage is given from the camera control CPU 291 described later according to the number of additions. The horizontal shift register 54 transfers a large amount of signal charge by addition, but there is an upper limit on the amount of signal charge that the horizontal shift register 54 can transfer, and the amount of signal charge exceeds the upper limit. In such a case, transfer failure occurs and noise is generated. Therefore, when the number of additions increases and the amount of signal charge generated by the addition increases, the substrate voltage Vs is adjusted to lower the saturation level of the signal charge generated by the photodiode 51 and add it. Limit the amount of previous signal charge. As a result, even if the addition is performed, the signal charge amount is prevented from exceeding the upper limit.

  Here, the relationship between the substrate voltage Vs and the number of saturated electrons will be described with reference to FIG. FIG. 4 is a schematic diagram showing an example of the relationship between the substrate voltage Vs and the number of saturated electrons (saturated charge amount). As shown in FIG. 4, the amount of saturated electrons can be reduced by setting the substrate voltage Vs to a high voltage. Therefore, by setting the optimum substrate voltage Vs according to the number of additions, the signal charge amount after the addition can be prevented from exceeding the upper limit, so that the horizontal transfer is stably performed.

  Next, the control system of the digital camera 1 will be described with reference to FIG. FIG. 2 is a block diagram of a control system of the digital camera 1 according to the present invention. In FIG. 2, the same members as those shown in FIG.

  The timing generator 246 generates a drive control signal for the CCD 50 based on a reference clock transmitted from a reference clock generator 271 described later. The drive control signal generated by the timing generator 246 includes, for example, an integration start / end timing signal for controlling the exposure start and end timings in the CCD 50, and a readout control signal (horizontal synchronization signal, vertical synchronization) of the light reception signal of each pixel. Clock signals such as a signal, a transfer signal, and the like. When these clock signals are supplied to the CCD 50, the CCD 50 performs drive control corresponding to each clock signal. That is, the timing generator 246 functions as drive signal generation means in the imaging apparatus according to the present invention.

  The drive control signal generated by the timing generator 246 is controlled according to the brightness of the subject, for example, under the control of a camera control CPU 291 described later.

  Next, the signal processing circuit 242 includes a CDS circuit 243 and an AGC circuit 244, and a predetermined process is performed on the image signal via these components. Hereinafter, a predetermined process for the image signal performed by the signal processing circuit 242 will be described.

  A CDS (Correlated Double Sampling) circuit 243 performs noise reduction at the time of reading from the image signal read from the CCD 50 and corrects the black level by performing an OB clamping operation.

  The AGC (automatic gain control) circuit 244 corresponds to the amplifier in the present invention, and adjusts the gain of the image signal processed by the CDS circuit 243 according to, for example, the brightness of the subject under the control of the camera control CPU 291 described later. To do.

  The A / D converter 245 converts each pixel signal constituting the image signal input from the AGC circuit 244 into a digital signal. The A / D converter 245 converts each pixel signal of an analog signal into, for example, a 14-bit digital signal based on the A / D conversion clock input from the reference clock generation unit 271.

  In this manner, the image signal read by the CCD 50 is subjected to predetermined processing by the signal processing circuit 242 and converted into a digital image signal. The digitized image signal is captured by the image processing CPU 261 and subjected to predetermined processing.

  The image processing CPU 261 is composed of a microcomputer, and comprehensively controls image signal processing operations performed by the digital camera 1. In the following, processing for a digital image signal performed by the image processing CPU 261 will be described.

  First, the image signal captured by the image processing CPU 261 is written into the image memory 275 in synchronization with the reading of the image signal output from the CCD 50. That is, the digital image signal used for the processing performed by the image processing CPU 261 is once recorded in the image memory 275, taken out from the image memory 275, and used for processing in each block.

  As shown in FIG. 2, the image processing CPU 261 includes, for example, a black level correction unit 263, a pixel interpolation unit 264, a resolution conversion unit 265, a white balance control unit 266, a gamma correction unit 267, a matrix calculation unit 268, a shading correction unit 269, The image processing unit 262 includes an image compression unit 270, a reference clock generation unit 271, an image size conversion unit 272, and the like. The image processing unit 262 performs known image signal processing on the digital image signal extracted from the image memory 275. It is something to apply. Then, the digital image signal that has been subjected to the predetermined processing in these parts is stored in the image memory 275 again.

  The reference clock generation unit 271 is a circuit that generates a reference clock used for driving control of the digital camera 1 and supplies the reference clock to each circuit. Specific examples of the reference clock in the present invention include a reference clock used for the timing generator 246, an A / D conversion clock used for the A / D converter 245, and the like. Generate a clock.

  The image size conversion unit 272 performs addition in the live view mode or the moving image mode to prevent the size of the image to be displayed on the LCD monitor 211, the EVF 210, and the like from changing. By controlling, the image is enlarged or reduced according to the number of additions, thereby generating an image of a constant size regardless of the number of additions.

  Next, the LCD monitor 211 performs display of an image signal captured by the CCD 50 and GUI display.

  The LCD drive circuit 279 includes a buffer memory (VRAM) that temporarily stores an image signal read from the image memory 275 by the image processing CPU 261, and displays the image signal on the LCD monitor 211 as a field image.

  Next, the camera control CPU 291 is composed of a microcomputer, and controls the drive of each member of the camera body 2 and the lens unit 3 sequentially based on switch signals generated by switch operations of a switch group 295 to be described later. The overall shooting operation of 1 is controlled.

  The camera control CPU 291 controls the exposure of the digital camera 1 based on the image signal read from the CCD 50. Specifically, the camera control CPU 291 reads the image data in the selected photometry area from the image data captured from the CCD 50 and written in the image memory 275, and calculates exposure control data based on the read image data. To do. Based on the calculated exposure control data and a preset program diagram, which will be described later, the shutter speed, the aperture value, the gain of the AGC circuit 244, and the number of signal charges added by the CCD 50 are determined. Then, the optimum exposure control is performed by controlling the diaphragm 352, the AGC circuit 244, and the timing generator 246 based on the determined control values. As described above, the CCD 50 functions as a photometric means in the imaging apparatus according to the present invention. The camera control CPU 291 functions as an exposure control unit, an amplifier control unit, and a drive signal control unit in the imaging apparatus according to the present invention. Thus, in the present invention, by adding the number of additions as the fourth parameter to the conventional three exposure control parameters such as the shutter speed, aperture value, and photographing sensitivity (corresponding to the gain of the AGC circuit 244), Since the shutter speed, aperture value, and shooting sensitivity can be set independently, shooting conditions can be set with a high degree of freedom. In addition, stable exposure control can be performed even in darker areas.

  Further, the camera control CPU 291 generates an optimum substrate voltage for the CCD 50 according to the number of additions determined by the exposure control described above. In this way, the camera control CPU 291 functions as a substrate voltage generation unit in the imaging apparatus according to the present invention.

  In addition, the camera control CPU 291 is determined by the above-described exposure control in order to prevent the size of the image displayed on the LCD monitor 211, the EVF 210, and the like from being changed by performing addition in the live view mode or the moving image mode. The operation of the image size conversion unit 272 is controlled so as to generate an image of a constant size regardless of the number of additions by enlarging or reducing the image according to the number of additions made.

  Next, the switch group 295 in FIG. 2 corresponds to the shutter button 201, the main switch 202, the mode setting dial 203, the selection / decision button 206, the menu button 207, the quick view button 208, the digital zoom button 209, and the like in FIG. Switch.

  Here, details of the exposure control operation using the number of pixel additions as one of the exposure control parameters will be described with reference to FIG. FIG. 6 is a schematic diagram showing an example of an exposure control program diagram in the digital camera 1 according to the present invention. It should be noted that the shutter speed SS, aperture value FNo, imaging sensitivity Sv (sense value; equivalent to the gain of the AGC circuit 244), exposure control value such as the number of additions, exposure value Ev (Exposure Value), and subject brightness Bv The value such as (Bright Value) is an example, and can be appropriately changed according to the sensitivity of the image sensor, the number of pixels, and the like.

  In the present invention, during live view operation or moving image mode, exposure control of the digital camera 1 is performed using the shutter speed SS, the aperture value Fno, the shooting sensitivity Sv (corresponding to the gain of the AGC circuit 244), and the number of additions as exposure control parameters. To do.

  When the subject is initially bright, for example, when the exposure value is Ev16 or more, as shown in FIG. 6, the aperture is set to F11, the gain of the AGC circuit 244 is set to 0 dB, and the number of additions is a fixed value of 3 (number of additions 2). Exposure is controlled by changing the speed SS.

  Next, when the brightness of the subject is lowered, for example, in the range of the exposure value from Ev16 to Ev8, the gain and the addition number of the AGC circuit 244 are set to the same fixed values as those when the exposure value is Ev16 or more. Exposure is controlled by changing the speed SS and the aperture value Fno.

  When the brightness of the subject further decreases, for example, when the exposure value is Ev8 or less, as shown in FIG. 6, the aperture value becomes a fixed value of open FNo. 2.8, so the gain of the AGC circuit 244 is increased. Alternatively, exposure control is performed by increasing the imaging sensitivity Sv by increasing the number of additions. The shutter speed SS is limited to about 1/12 seconds although the shutter speed SS is decreased. This is to prevent the display image from awkwardly moving like a frame advance due to a decrease in the frame rate accompanying a decrease in the shutter speed SS.

  Here, how the gain of the AGC circuit 244 or the number of additions changes when the exposure value falls below EV8 will be described with reference to FIG. FIG. 7 is a schematic diagram showing an example of the relationship between the subject luminance Bv and the photographing sensitivity Sv in the digital camera 1 according to the present invention.

  When the subject brightness is equal to or higher than Bv2.4 (corresponding to Ev8 in FIG. 6), as described above, the gain of the AGC circuit 244 is set to a fixed value of 0 dB and the number of additions is 3 (number of additions 2).

  Next, when the subject brightness is lower than Bv2.4, for example, when the subject brightness is in the range of Bv2.4 to Bv0.4, as shown in FIG. 7, the AGC circuit 244 reduces the subject brightness Bv. The imaging sensitivity Sv is increased by increasing the gain from 0 dB to 12 dB. Since the S / N ratio decreases when the gain of the AGC circuit 244 is increased, the upper limit is usually about 12 dB. Therefore, in an ordinary digital camera, for example, when the subject brightness is further lower than Bv2.4, the gain of the AGC circuit 244 cannot be increased above 12 dB, so that an appropriate exposure amount cannot be obtained. That is, in a dark place, a beautiful live view color image or a moving image with good S / N cannot be obtained. Therefore, in the present invention, as shown in FIG. 7, when the subject brightness is further lower than Bv2.4, the addition number is increased from 3 to 6, for example, as the subject brightness Bv decreases. Thus, the photographing sensitivity Sv is increased. In this way, a beautiful live view image or a moving image with good S / N can be obtained even in a dark place.

  Next, the relationship between the number of additions and the frame rate will be described with reference to FIG. FIG. 8 is a schematic diagram showing an example of the relationship between the number of additions and the frame rate (hereinafter referred to as display rate) in the digital camera 1 according to the present invention. When the number of additions is increased, the display rate is increased as shown in FIG. 8 because the number of horizontal lines of the image signal read from the CCD 50 is reduced. Further, when the number of additions is reduced, the display rate is lowered because the number of horizontal lines of the image signal read from the CCD 50 is increased.

  On the other hand, if the display rate becomes too fast, the image signal processing cannot be followed. If the display rate becomes too slow, the image displayed on the LCD monitor 211, EVF 210, etc. will be awkward like frame advance. Therefore, in the present invention, the camera control CPU 291 sets an appropriate range of the display rate in advance and sets the shutter speed, the aperture 352, or the gain of the AGC circuit 244 so that the display rate does not deviate from the range. , So that the number of additions is not significantly changed.

  Specifically, when the subject becomes brighter, the number of additions decreases and the display rate becomes slower. Therefore, the camera control CPU 291 previously sets an upper limit value serving as a reference for the brightness of the subject. When the brightness of the subject measured by the CCD 50 exceeds the upper limit, the exposure amount is controlled by controlling the timing generator 246 to increase the shutter speed or by controlling the aperture 352 to reduce the aperture. Decrease. As a result, the number of additions can be increased, so that a reduction in display rate can be prevented.

  On the other hand, when the subject becomes dark, the number of additions increases and the display rate becomes faster. Therefore, the camera control CPU 291 previously sets a lower limit value that serves as a reference for the brightness of the subject. When the brightness of the subject measured by the CCD 50 turns around the lower limit, the signal amount is increased by increasing the gain by controlling the AGC circuit 244. As a result, the number of additions can be reduced, so that an increase in display rate can be prevented.

  As described above, in the image pickup apparatus according to the present invention, when an image pickup device having a Bayer array color filter configuration is driven in the live view mode or the moving image mode, a single vertical transfer unit is supplied with signal charges of the same color. Since reading is performed, addition can be performed without losing color information.

  In addition, the signal charges generated in most pixels are read without thinning out, and the read signal charges are added, so that even when shooting in a dark place, the reduced signal amount is reduced. It is possible to compensate, and it is possible to obtain a beautiful live view color image or a moving image with a good S / N.

  Further, by changing the number of additions according to the brightness of the subject, the reduced signal amount can be compensated appropriately even when shooting in a dark place, etc., so that a good S / N is beautiful. An imaging apparatus capable of generating an image signal and forming a high-quality live view color image or moving image, and a driving method of the imaging element can be provided.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be changed or improved as appropriate. For example, in the above-described embodiment, the CCD area sensor is used as the photometric means. However, a dedicated photometric sensor such as SPD (Silicon Photo Diode) may be used.

  Also in the still image mode, the signal charge may be read out by the same method as the signal charge reading method performed in the above-described live view mode or moving image mode.

1 is a schematic external view of a digital camera according to the present invention. 1 is a circuit block configuration diagram of a digital camera according to the present invention. It is a schematic diagram which shows the structure of CCD in the digital camera which concerns on this invention. It is a schematic diagram which shows the relationship between the substrate voltage of CCD and the number of saturated electrons in the digital camera which concerns on this invention. 4 is a timing chart of a CCD drive control signal in the digital camera according to the present invention. It is a schematic diagram which shows an example of the exposure control program diagram in the digital camera which concerns on this invention. It is a schematic diagram which shows an example of the relationship between the subject brightness | luminance and imaging sensitivity in the digital camera which concerns on this invention. It is a schematic diagram which shows an example of the relationship between the addition number and frame rate in the digital camera which concerns on this invention.

Explanation of symbols

1 Digital Camera 2 Camera Body 201 Shutter Button 202 Main Switch 203 Mode Setting Dial 204 Jog Dial (Cross Key)
205 OK button 206 Select / OK button 207 Menu button 208 Quick view button 209 Digital zoom button 210 Electronic viewfinder (EVF)
211 LCD monitor 212 Built-in flash 242 Signal processing circuit 243 CDS circuit 244 AGC circuit 245 A / D converter 246 Timing generator 247 Aperture / shutter drive circuit 248 Focus / zoom motor drive circuit 261 Image processing CPU
262 Image processing unit 263 Black level correction unit 264 Pixel complementation unit 265 Resolution conversion unit 266 White balance control unit 267 Gamma correction unit 268 Matrix calculation unit 269 Shading correction unit 270 Image compression unit 271 Reference clock generation unit 272 Image size conversion unit 275 Image Memory 276 Memory card driver 277 Memory card 278 External communication I / F
279 LCD drive circuit 280 EVF drive circuit 291 Camera control CPU
292 Flash control circuit 295 Switch group (shutter button, etc.)
3 Lens Unit 351 Focus / Zoom Motor 352 Aperture 50 CCD Area Sensor 51 Photodiode 52 Light-Receiving Area 53 Vertical Shift Register (Vertical CCD)
54 Horizontal shift register (horizontal CCD)
55 Output section

Claims (9)

A plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge;
A color filter configuration in which a plurality of types of color filters are arranged corresponding to the plurality of pixels, and at least one type of the color filters is arranged in a checkered pattern;
An image sensor having a plurality of vertical transfer units that vertically transfer the signal charges read from the plurality of pixels for each column;
Drive signal generating means for generating a drive control signal for controlling the drive of the image sensor;
A drive signal control means for controlling the operation of the drive signal generation means,
The drive signal control means is configured to output signal charges generated by the plurality of pixels having the same type of color filter among the plurality of pixels having the plurality of types of color filters. An image pickup apparatus that controls the operation of the drive signal generation unit so as to generate a signal charge by reading the signal charges to a plurality of vertical transfer units and adding the read signal charges in the vertical direction. The imaging device has display means for displaying an image captured by the imaging device based on an image signal read from the imaging device,
When the image pickup device is driven in a shooting standby mode and the generated image is displayed on the display means, or when the image pickup device is driven in a moving image mode to perform moving image shooting,
The drive signal control means is configured to output signal charges generated by the plurality of pixels having the same type of color filter among the plurality of pixels having the plurality of types of color filters. The operation of the drive signal generation unit is controlled so as to generate a signal charge by reading the signal charges to a plurality of the vertical transfer units and adding the read signal charges in a vertical direction. Imaging device. The imaging apparatus according to claim 1, wherein the drive signal control unit controls the operation of the drive signal generation unit so as to change the number of additions. 3. The drive signal control means controls the operation of the drive signal generation means so as to change a display rate of the image displayed on the display means in accordance with the number of additions. Or the imaging device of 3. The imaging apparatus includes a substrate voltage generation unit that generates a substrate voltage for adjusting a saturation amount of the signal charge generated in the pixel,
5. The imaging apparatus according to claim 1, wherein the substrate voltage generation unit generates the substrate voltage in accordance with the number of additions. 6. The imaging device includes photometric means for detecting the brightness of a subject;
An electronic shutter or an aperture for adjusting the exposure of the image sensor;
Exposure control means for controlling the operation of the electronic shutter or the diaphragm based on the detection result of the photometry means,
When displaying the image on the display means at a predetermined display rate according to the number of additions,
When the brightness of the subject detected by the photometry means exceeds a preset reference value,
5. The imaging apparatus according to claim 2, wherein the exposure control unit controls the electronic shutter or the diaphragm so as to increase a shutter speed or reduce a diaphragm. 6. . The imaging device includes photometric means for detecting the brightness of a subject;
An amplifier for amplifying the image signal read from the image sensor;
Amplifier control means for controlling the operation of the amplifier based on the detection result of the photometry means,
When displaying the image on the display means at a predetermined display rate according to the number of additions,
When the brightness of the subject detected by the photometric means is below a preset reference value,
The imaging apparatus according to claim 2, wherein the amplifier control unit controls the amplifier so as to increase an amplification degree of the amplifier. A plurality of pixels arranged in a two-dimensional matrix and photoelectrically converting a subject optical image to generate a signal charge;
A color filter configuration in which a plurality of types of color filters are arranged corresponding to the plurality of pixels, and at least one type of the color filters is arranged in a checkered pattern;
A plurality of vertical transfer units that vertically transfer the signal charges read from the plurality of pixels for each column;
When reading the signal charge generated by the plurality of pixels,
Among the plurality of pixels in which the plurality of types of color filters are arranged, signal charges generated by the plurality of pixels in which the same type of color filter are arranged are respectively transferred to the plurality of the vertical transfer units. And a signal charge is generated by adding the read signal charges in the vertical direction. The method of driving an image sensor according to claim 8, wherein the addition is performed by changing the number of additions.

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