JP5397048B2 - Digital camera, and its sensitivity setting method and program - Google Patents

Description

  The present invention relates to a digital camera capable of shooting with high sensitivity by pixel addition, and a shooting sensitivity setting method and program thereof.

  2. Description of the Related Art Conventionally, as a technique for improving imaging sensitivity in an imaging apparatus such as a digital camera, pixel addition processing for adding a pixel charge value of each pixel in an image or a pixel value after conversion to a digital signal in a horizontal and / or vertical direction There is a technique for amplifying the brightness of each pixel by performing the above. For example, in Patent Document 1 below, when an image pickup signal is read out from a CCD, the charge of pixels of the same color in the CCD is read out by adding two pixels in the vertical (vertical) direction, or read in the vertical (vertical) direction and vertical (vertical). ) Describes a digital camera that reads out by adding four pixels in the direction.

  In the above pixel addition processing, the sensitivity can be improved without amplifying the gain of the image pickup signal output from the CCD, or the amplification degree is kept within an allowable range, so that the high ISO sensitivity is obtained without degrading the image quality. (Shooting sensitivity) can be taken, and a shorter exposure time can be set as an exposure time (shutter speed) for obtaining an appropriate exposure during shooting.

JP 2006-352717 A

  However, when the sensitivity at the time of shooting is improved by the pixel addition process as described above, the size of the finally obtained image is reduced. That is, when pixel addition of 2 to 3 pixels in the vertical direction and 2 to 3 pixels in the horizontal direction is performed, the image size is reduced to 1/4 to 1/9 according to the addition magnification.

  For this reason, for example, when the ISO sensitivity is set by the user, the maximum value within the adjustment range of the gain of the imaging signal, i.e., the maximum that allows an acceptable image quality, is intended for shooting at a faster shutter speed. When an ISO sensitivity obtained by pixel addition processing that is higher than the ISO sensitivity obtained by setting the gain is set, the following problem occurs. In other words, if the image size after pixel addition obtained at the time of shooting is smaller than the preset image size at the time of recording (set image size), the pixel size is interpolated at the time of recording the shot image. Therefore, there is a problem that the image quality (substantial resolution) of the recorded image is lowered as a result.

  The present invention has been made in view of such conventional problems, and a digital camera capable of maintaining the image quality of a recorded image within a certain range in a configuration capable of shooting with high sensitivity by pixel addition, and its An object is to provide a method and a program for setting a photographing sensitivity.

In order to solve the above-described problem, in the digital camera according to the first aspect of the present invention, in the digital camera that records the subject image captured by the image sensor, gain means for amplifying the signal of the image sensor, Pixel addition means for amplifying the brightness of the subject image by performing pixel addition processing for adding a predetermined number of pixels to the subject image, image size setting means for setting an image size at the time of recording the subject image, and photographing Sensitivity setting means for setting the shooting sensitivity at the time, and the maximum sensitivity of the shooting sensitivity set by the sensitivity setting means has a maximum gain amount within an adjustment range in which the image quality allowed by the gain means can be secured. When the pixel addition is performed with the maximum number of additions that can be set in the image size set by the image size setting means by the pixel addition means Characterized in that the sensitivity.

In the digital camera according to the second aspect of the present invention, the selection control means for causing the user to select the photographing sensitivity to be secured at the time of photographing as a selection candidate of a plurality of stages of photographing sensitivity, and the sensitivity setting means include: characterized by the Turkey be set as the photographic sensitivity should ensure imaging sensitivity this selection control means was selected by the user at the time of photographing.

The digital camera according to the invention of claim 3 further comprises display means, wherein the selection control means displays any one of a plurality of selection screens each indicating a selection candidate whose upper limit is different from each other. causes display on the display means and the Turkey to select one of the imaging sensitivity, shown as selection candidates in the selection screen to the user.

  According to a fourth aspect of the present invention, in the digital camera according to the fourth aspect of the present invention, the second selection that allows the user to select one of a plurality of predetermined image sizes as the image size at the time of recording the subject image. Control means, and the image size setting means sets the image size selected by the user by the second selection control means as the image size at the time of recording the subject image.

  The digital camera according to claim 5 has a plurality of shooting modes as settable shooting modes, and the image size setting means determines in advance corresponding to the set shooting mode. The recorded image size is set as the image size when the subject image is recorded.

In the digital camera according to the sixth aspect of the present invention, the image sensor includes a pixel addition mode in which the signal charge of each pixel is added in the horizontal and / or vertical direction, and the signal charge of each pixel. Corresponding to two drive modes, ie, a normal mode for outputting without adding, the pixel adding means performs pixel addition processing on the subject image by driving the image sensor in the pixel adding mode. And

According to a seventh aspect of the present invention, in the digital camera according to the seventh aspect, the sensitivity setting means performs pixel addition processing by the pixel addition means when the gain setting means can cope with amplification of the signal of the image sensor. The signal of the image sensor is amplified by the gain means.

Further, in the digital camera according to the invention described in claim 8, when the sensitivity setting means is higher than the sensitivity that can be dealt with by amplification of the signal of the image sensor by the gain means, the gain means allows the sensitivity setting means. The maximum gain amount is set within an adjustment range in which image quality can be ensured, and pixel addition is performed with less than the maximum addition number that can be set in the image size set by the image size setting means by the pixel addition means. Features.

In the photographing sensitivity setting method according to the ninth aspect of the invention, a pixel addition process for recording a subject image picked up by an image sensor and adding a predetermined number of pixels to the subject image as necessary. A sensitivity setting method in a digital camera that amplifies the brightness of the subject image by performing the steps of: amplifying the signal of the imaging device; and setting an image size at the time of recording the subject image; A step of setting a photographing sensitivity at the time of photographing, and the maximum sensitivity of the photographing sensitivity set in the step of setting the photographing sensitivity is an adjustment capable of ensuring an acceptable image quality in the step of amplifying the signal of the image sensor. The maximum number of additions that can be set in the image size set in the step of setting the maximum gain amount within the range and setting the image size at the time of recording in the pixel addition process Characterized in that the sensitivity in the case of performing pixel addition.

In the program according to the tenth aspect, the subject image captured by the image sensor is recorded, and pixel addition processing for adding a predetermined number of pixels to the subject image is performed as necessary. To the computer of the digital camera that amplifies the brightness of the subject image, the processing for amplifying the signal of the image sensor, the processing for setting the image size at the time of recording the subject image, and the shooting sensitivity at the time of shooting The maximum sensitivity of the shooting sensitivity set in the process of setting the shooting sensitivity is the maximum gain within the adjustment range that can ensure the image quality allowed by the process of amplifying the signal of the image sensor. Set the amount and add the pixels with the maximum number of additions that can be set for the image size set in the process for setting the image size during recording in the pixel addition process. Characterized in that the sensitivity in the case of performing.

  According to the present invention, it is possible to maintain the image quality of a recorded image within a certain range in a configuration capable of photographing with high sensitivity by pixel addition.

1 is a block diagram of a digital camera according to the present invention. It is a schematic diagram of CCD which shows the principle of the reading method by 2 pixel addition mode. It is a schematic diagram of CCD which shows the principle of the reading method by 4 pixel addition mode. (A) is a conceptual diagram showing Bayer data consisting of imaging signals read out in the 2-pixel addition mode, and (b) is a conceptual diagram showing Bayer data consisting of imaging signals read out in the 2-pixel addition mode. It is explanatory drawing which shows the relationship between the largest pixel addition magnification which can obtain the image data of a recording pixel size, without performing the expansion process by pixel interpolation etc., and the largest ISO sensitivity which can be ensured. It is a figure which shows an image size selection menu. It is a flowchart which shows the ISO sensitivity setting process which CPU performs in a predetermined exposure mode. It is a figure which shows the ISO sensitivity selection menu displayed by the ISO sensitivity setting process.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 is a block diagram showing an outline of the electrical configuration of a digital camera 1 according to the present invention. The digital camera 1 has zoom, AF (autofocus), and AE (automatic exposure) functions, and has the following configuration.

  That is, the digital camera 1 includes a lens group that includes a zoom lens and a focus lens (not shown), a diaphragm, and a mechanical shutter. The actuator block 3 drives the zoom lens and the focus lens. A zoom motor and a focus motor, a diaphragm actuator for driving the diaphragm to control the opening degree, and a shutter actuator for opening and closing the mechanical shutter.

  The driver circuit 4 is constituted by a driver for driving the motors and actuators of the actuator block 3, and generates various drive signals in accordance with instructions of the CPU 5 that controls the entire digital camera 1, and outputs the drive signals to the actuator block. 3 is driven to drive each part of the lens block 2.

  The digital camera 1 also includes a CCD 6 on which subject light that has passed through the lens block 2 enters, a correlated double sampling circuit (CDS) 7, a programmable gain amplifier (PGA) 8, and an A / D converter (A / D). 9 is provided.

  The CCD 6 has a configuration in which a Bayer array primary color filter is provided on a photosensitive surface on which an optical image of a subject is formed and has an effective pixel number of about 10 million pixels, and a timing generator (TG) according to a command from the CPU 5. 10 is driven by the vertical / horizontal driver 11 based on the timing signal generated by 10 and outputs an analog imaging signal corresponding to the optical image of the subject to the correlated double sampling circuit 7.

  In the present embodiment, the CCD 6 has a configuration capable of being driven in three types of drive modes: a normal mode, a 2-pixel addition mode, and a 4-pixel addition mode. Here, the normal mode is a driving mode for reading out signal charges of all the pixels of the CCD 6 by a general frame reading method. The two-pixel addition mode is a driving mode for reading out the signal charges of all the pixels by adding the charges of the pixels of the same color by two pixels in the vertical (vertical) direction in the CCD 6. This is a drive mode for reading out the signal charges of the pixels in the CCD 6 by adding the charges of the pixels of the same color by four pixels in the vertical (vertical) direction and the vertical (vertical) direction.

  In this embodiment, the vertical / horizontal driver 11 drives the CCD 6 in the two-pixel addition mode or the four-pixel addition mode as required under the control of the CPU 5 to realize pixel addition processing. That is, in the present embodiment, the vertical / horizontal driver 11 functions as the pixel addition means of the present invention. Note that a specific method for reading an image pickup signal (signal charge) when the CCD 6 is driven in the 2-pixel addition mode and the 4-pixel addition mode will be described later.

  On the other hand, the correlated double sampling circuit 7 reduces noise included in the input imaging signal by correlated double sampling, and outputs it to the programmable gain amplifier 8. The programmable gain amplifier 8 adjusts the gain of the signal after noise reduction to a gain according to the ISO sensitivity set at the time of shooting. The A / D converter 9 samples the image signal after gain adjustment, converts it to a digital signal having a predetermined number of bits, and outputs the digital signal to the image processing unit 12.

  The image processing unit 12 generates R, G, and B color component data (hereinafter, RGB data) for each pixel based on the input digital imaging signal (Bayer data) using the SDRAM 13 as a working memory in accordance with a command from the CPU 5. RGB interpolation processing, YUV conversion processing for generating YUV data consisting of luminance signals (Y) and color difference signals (U, V) from RGB data for each pixel, and digital for improving image quality such as auto white balance and edge enhancement Perform signal processing. The YUV data converted by the image processing unit 12 is sequentially stored in the SDRAM 13.

  The YUV data is converted into a video signal every time one frame is stored in the SDRAM 13 and then sent to a liquid crystal monitor (LCD) 15 having a backlight (BL) 14 and displayed on the screen as a through image. The liquid crystal monitor 15 functions as display means of the present invention. The YUV data temporarily stored in the SDRAM 13 is compressed by the JPEG method or the like by the CPU 5 at the time of shooting in the recording mode, and finally recorded in the external memory 16 as a still image file of a predetermined format.

  The external memory 16 is composed of, for example, various memory cards, and the still image file recorded in the external memory 16 is read and expanded as needed by the CPU 5 according to the user's selection operation in the reproduction mode, and SDRAM 13 as YUV data. Is displayed on the liquid crystal monitor 15.

  The flash memory 17 stores various programs for causing the CPU 5 to control the respective units, for example, control programs related to AE control, AF control, AWB control, and the like, and various data used for the control. The various data includes, for example, a program diagram showing a combination of shutter speed, aperture (F value), and ISO sensitivity necessary for obtaining an appropriate exposure during AE control. The program includes a program for causing the CPU 5 to function as an image size setting unit, a sensitivity control unit, a selection control unit, a sensitivity setting unit, and a second selection control unit of the present invention, and to execute processing described later. include. Further, the flash memory 17 stores data defining the operation of the digital camera 1, and setting data that is changed by the user as necessary and setting data that is automatically changed by the CPU 5 are stored. The data includes setting data regarding shooting conditions.

  The digital camera 1 includes a shutter button (not shown), a power key, a mode changeover switch, a key input unit 18 including a zoom up and zoom down button, a rechargeable battery 19 such as a nickel metal hydride battery, and the like. A power supply control circuit 20 for supplying power to each unit, a microcomputer 21 for controlling them, a light emitting tube such as a xenon tube, and a driving circuit thereof, and a strobe circuit for emitting auxiliary light as necessary during photographing 22.

  The microcomputer 21 constantly scans the key input unit 18 for operations of various switches and the like, and when any operation key is operated by the user, an operation signal corresponding to the operation content is sent to the CPU 5. . The shutter button has a so-called half shutter function capable of two-stage operation, for example, a half-press operation and a full-press operation.

  Here, a specific reading method of the imaging signal in the above-described 2-pixel addition mode and 4-pixel addition mode in the CCD 6 will be described.

  FIG. 2 is a schematic diagram of the CCD 6 showing the principle of a method for reading an imaging signal in the two-pixel addition mode. The CCD 6 includes a large number of photosensitive CCDs (R, G, B in the figure) constituting pixels, a hold accumulation unit HOLD composed of CCDs that do not have a photosensitive function arranged in the horizontal direction, and a horizontal transfer unit 61. A vertical transfer unit (not shown) that vertically transfers the signal charges of the CCDs and an output circuit 62 are provided.

  In the present embodiment, the CPU 5 causes the vertical / horizontal driver 11 to generate a predetermined drive signal, so that in the two-pixel addition mode, the signal charge for one frame is read in 4/8 lines and 2 fields as shown in the figure. . That is, in the first field, only the signal charges of the odd-numbered lines (15, 13, 11,...) In the vertical direction are vertically transferred, and at that time, the signal charges for one line are transferred using the hold accumulation unit HOLD. By temporarily holding the transfer time for one line, the signal charges of the odd lines adjacent in the vertical direction, that is, the signal charges of two pixels of the same color are vertically added and transferred to the horizontal transfer unit 61. Thereafter, the odd line signals composed of the signal charges (R, G, R, G,...) After the vertical addition are sequentially swept from the output circuit 62. Thereafter, the signal charges of all odd lines are sequentially swept out.

  Next, in the second field, vertical addition similar to that in the first field is performed on the even-numbered lines (16, 14, 12,...) In the vertical direction, and the pixel arrangement (G, The signal charges for two lines after vertical addition consisting of B, G, B,...) Are sequentially swept from the output circuit 62. Thereafter, signal charges of all even lines are sequentially swept out.

  FIG. 4A is a conceptual diagram showing Bayer data composed of imaging signals when the CCD 6 is driven in the two-pixel addition mode. As shown in the figure, in the two-pixel addition mode, the number of pixels in the vertical direction is one half of the whole, but pixel information for the total number of pixels is reflected and the pixel value (luminance information) is doubled as a whole. Amplified Bayer data, that is, image data of about 5 million pixels is obtained, and the image data is temporarily stored in the SDRAM 13 at the time of photographing.

  FIG. 3 is a schematic diagram of the CCD 6 illustrating the principle of a method for reading an image signal in the 4-pixel addition mode. Also in the 4-pixel addition mode, as in the case of driving in the 2-pixel addition mode, the signal charge for one frame is read in 4/8 lines and 2 fields as shown in the figure.

  That is, in the first field, only the signal charges of (15, 13, 11,...) On the odd-numbered lines in the vertical direction are vertically transferred, and at that time, the signal charges for one line using the hold accumulation unit HOLD. Is temporarily held for the transfer time of one line, the signal charges of odd lines adjacent in the vertical direction are added, that is, the signal charges of two pixels of the same color are vertically added and transferred to the horizontal transfer unit 61. . At the same time, at the timing when the signal charge vertically added in the horizontal transfer unit 61 is transferred by two pixels, the signal charge that is vertically added next is added (horizontal addition) while being shifted by two pixels in the horizontal direction. Thereafter, two lines of signal charges composed of the same color pixel array (R, G, R, G,...) Are vertically added, and signals of two pixels of the same color existing every other pixel on the same line. Odd line signals obtained by horizontally adding charges are sequentially swept from the output circuit 62. Thereafter, the signal charges of all odd lines are sequentially swept out.

  Similarly, in the second field, vertical and horizontal additions similar to those in the first field are performed on the even-numbered lines (16, 14, 12,...) In the vertical direction, and the same color pixel array (G , B, G, B,...)) Are added vertically, and signal charges of two pixels of the same color existing every other pixel in the same line are added horizontally. The signals are swept in order. Thereafter, signal charges of all even lines are sequentially swept out.

  FIG. 4B is a conceptual diagram showing Bayer data including imaging signals when the CCD 6 is driven in the 4-pixel addition mode. As shown in the figure, in the four-pixel addition mode, the number of pixels in the vertical direction and the horizontal direction is each halved, but pixel information for the total number of pixels is reflected and the pixel value (luminance information) as a whole is reflected. Is amplified four times, that is, image data of about 2.5 million pixels is obtained, and the image data is temporarily stored in the SDRAM 13 at the time of photographing.

On the other hand, in the digital camera 1, the following seven types of recorded image sizes can be set by the user as the size of an image to be recorded at the time of photographing (hereinafter simply referred to as “recorded image size”). The specific numbers of pixels in the horizontal and vertical directions are as shown in parentheses.
・ 10M (3,648 × 2,736)
・ 3: 2 (3,648 × 2,432)
・ 16: 9 (3,648 × 2,048)
・ 5M (2,560 × 1,920)
・ 3M (2,048 × 1,536)
・ 2M (1,600 × 1,200)
・ VGA (640 × 480)

  In the digital camera 1, the ISO sensitivity at the time of shooting is “50”, “100”, “200”, “400”, “800”, “1600”, “3200”, “6400” at a maximum of 8 The ISO sensitivity of the stage can be set. Among the ISO sensitivities, “50” to “1600” are values that can be secured by adjusting the gain of the imaging signal within the adjustment range in which the allowable image quality can be secured by the programmable gain amplifier 8 described above. . Further, “3200” is a value that can be secured by driving the CCD 6 in the above-described two-pixel addition mode at the same time as adjusting the gain to the maximum value, and “6400” is simultaneously adjusting the gain to the maximum value. This is a value that can be secured by driving the CCD 6 in the 4-pixel addition mode described above.

  In this embodiment, since the effective number of pixels of the CCD 6 is about 10 million pixels (3,648 × 2,736), the print image size that can be set and the image data of each print image size are represented by pixels. A maximum pixel addition magnification that can be used when obtaining without performing enlargement processing by interpolation or the like, in other words, a drive mode in which an image pickup signal composed of signal charges having an image size equal to or larger than each recorded image size can be read from the CCD 6; The relationship with the maximum ISO sensitivity that can be secured by the pixel addition magnification (drive mode) is as shown in FIG.

  In the digital camera 1 having the above configuration, when the user requests the user to set the recording image size by a predetermined key operation, the CPU 5 displays the image size selection menu 100 shown in FIG. After being displayed on the monitor 15 and having the user select a desired image size by a predetermined key operation from the image size selection menu 100, the selected image size is set as a recording image size. That is, the setting data relating to the recorded image size stored in the flash memory 17 is updated.

  In the digital camera 1, as an exposure mode that is an operation mode related to exposure control at the time of shooting, a predetermined exposure mode in which the user can specify ISO sensitivity at the time of shooting, for example, shutter speed, aperture (F value), etc. , ISO mode (shooting conditions that determine the exposure) can be set manually by the user, or only the ISO speed is fixed to an arbitrary value, and the shutter speed and aperture (F value) are set accordingly. ISO sensitivity priority mode for automatically controlling to a value that can be secured is provided.

  At the time of shooting when the predetermined exposure mode is set, the CPU 5 controls the ISO sensitivity from “50” to “1600” to control the drive mode of the CCD 6 to the normal mode, and a programmable gain amplifier. 8 is ensured by controlling the gain of the image pickup signal. The ISO sensitivity of “3200” is ensured by controlling the drive mode of the CCD 6 to the two-pixel addition mode and controlling the gain to the maximum value. The ISO sensitivity of “6400” is ensured by controlling the drive mode of the CCD 6 to the 4-pixel addition mode and controlling the gain to the maximum value.

  Furthermore, while the predetermined exposure mode is set, if the user requests ISO sensitivity setting during shooting by a predetermined key operation, the CPU 5 performs the ISO sensitivity setting process shown in the flowchart of FIG. Run.

  In the ISO sensitivity setting process, the CPU 5 first confirms the currently set recording image size (step S1), and the following three types of ISO sensitivity setting menus determined in advance according to the confirmed recording image size. Any one of the (selection screens) is displayed on the liquid crystal monitor 15 (steps S2 to S6).

  That is, when the recorded image size is any one of “10M”, “3: 2”, and “16: 9” (YES in step S2), “1600” shown in FIG. The first ISO sensitivity setting menu 101a with the six-step ISO sensitivity as a selection candidate is displayed on the liquid crystal monitor 15, and the user selects the desired ISO sensitivity by a predetermined key operation from the six-step ISO sensitivity (step) S3).

  If the recorded image size is either “5M” or “3M” (NO in step S2, YES in step S4), the upper limit is “3200” shown in FIG. 7B. A second ISO sensitivity setting menu 101b with the stage ISO sensitivity as a selection candidate is displayed on the liquid crystal monitor 15, and the desired ISO sensitivity is selected by a predetermined key operation from the above seven stages of ISO sensitivity (step) S5).

  Furthermore, when the recorded image size is “2M” or “VGA” other than the above (NO in steps S2 and S4, YES in step S6), “6400” shown in FIG. The third ISO sensitivity setting menu 101c with the eight-step ISO sensitivity as the selection candidate is displayed on the liquid crystal monitor 15, and the desired ISO is displayed to the user by a predetermined key operation from the eight-step ISO sensitivity. Sensitivity is selected (step S6).

  Thereafter, in the first to third ISO sensitivity setting menus 101a to 101c described above, the ISO sensitivity selected by the user is set as the ISO sensitivity at the time of shooting (step S7). That is, the setting data relating to the shooting conditions stored in the flash memory 17 is updated.

  That is, in the ISO sensitivity setting process described above, the maximum ISO sensitivity shown in FIG. 5 that can be secured when image data of the recording image size set at that time is obtained without performing an enlargement process by pixel interpolation or the like is obtained. A plurality of ISO sensitivities at the upper limit are set as selection candidates, and the user is allowed to select one of the selection candidates as an imaging condition.

  Therefore, at the time of shooting at the ISO sensitivity designated by the user, it is possible to always obtain image data of the recorded image size without performing enlargement processing by pixel interpolation or the like. In this case, even when the user specifies the ISO sensitivity, the image quality (substantial resolution) of the recorded image can always be maintained within a certain range.

  In the present embodiment, at the time of shooting when the above-described predetermined exposure mode is set, the CPU 5 controls the drive mode of the CCD 6 to the normal mode, and the imaging signal by the programmable gain amplifier 8 is changed. The ISO sensitivity from “50” to “1600” is secured by controlling the gain, but the ISO sensitivity in such a range is secured by a combination of the above gain adjustment and the drive mode of the CCD 6 (other than the normal mode). You may make it do.

  For example, when the ISO sensitivity set by the user is “800” and the recording pixel size is “5M”, the gain is controlled to a gain corresponding to the ISO sensitivity “400”, and at the same time, the drive mode is set to the two-pixel addition mode. If the recording pixel size is “2M”, the gain is controlled to a gain corresponding to the ISO sensitivity “200”, and at the same time, the drive mode is controlled to the 4-pixel addition mode, so that the set ISO is set. Sensitivity may be ensured. That is, the combination of the gain of the imaging signal and the drive mode of the CCD 6 is arbitrary as long as image data of the set recording image size can be obtained without performing enlargement processing by pixel interpolation or the like.

  Further, in the ISO sensitivity setting process described above, the recording pixel size set at that time is confirmed, and the ISO sensitivity setting menu (first to third ISO sensitivity setting menus 101a to 101c) described above is checked accordingly. For example, in a configuration in which a plurality of shooting modes are prepared as lower modes of the recording mode and the recording pixel size is fixed for each shooting mode, check the shooting mode set at that time, Accordingly, the ISO sensitivity setting menu described above may be switched.

  In the present embodiment, when a predetermined exposure mode in which the user can specify the ISO sensitivity at the time of shooting is set as the exposure mode, the CPU 5 sets the ISO sensitivity at the time of shooting. By switching the ISO sensitivity setting menu to be displayed according to the recording pixel size set at that time, the upper limit of the ISO sensitivity at the time of shooting is set to ISO sensitivity corresponding to the recording pixel size, that is, image data of the recording image size. Although the case of controlling to the maximum ISO sensitivity that can be obtained without performing enlargement processing by pixel interpolation or the like has been described, even when the ISO sensitivity at the time of shooting is automatically set, the upper limit corresponds to the recording pixel size The ISO sensitivity may be controlled.

  That is, for example, during the AE control when the exposure mode for automatically setting the ISO sensitivity at the time of shooting is set, the ISO sensitivity for obtaining an appropriate exposure is set in the CPU 5 at that time by the user. The ISO sensitivity according to the pixel size and the recording pixel size determined in advance corresponding to the shooting mode set by the user, and image data of those recorded image sizes is enlarged by pixel interpolation or the like. The maximum ISO sensitivity that can be obtained without any problem may be controlled as the upper limit.

  In such a case, the image quality (substantial resolution) of the recorded image is always within a certain range even when the ISO sensitivity is automatically set in a configuration capable of shooting with high sensitivity by pixel addition. Can be maintained.

  In the present embodiment, pixel addition processing (two-pixel addition or four-pixel addition) in an image captured by the CCD 6 has been described as being performed inside the CCD 6 when an imaging signal is read from the CCD 6. A similar pixel addition process can be applied to the image data that has been output from the CCD 6. In this case, the pixel addition process may be performed by dedicated hardware, or may be performed by a computer such as the CPU 5 based on a predetermined program. The pixel addition process is not necessarily performed on the Bayer data, and may be performed on RGB data after RGB interpolation or Y, Cb, Cr data after YUV conversion.

1 Digital camera 5 CPU
6 CCD
8 Gain Amplifier 11 Vertical / Horizontal Driver 15 LCD Monitor 17 Flash Memory 18 Key Input Unit 100 Image Size Selection Menu 101a First ISO Sensitivity Setting Menu 101b Second ISO Sensitivity Setting Menu 101c Third ISO Sensitivity Setting Menu

Claims (10)

In a digital camera that records a subject image captured by an image sensor,
Gain means for amplifying the signal of the image sensor;
Pixel addition means for amplifying the brightness of the subject image by performing pixel addition processing for adding a predetermined number of pixels to the subject image;
Image size setting means for setting an image size at the time of recording the subject image;
Sensitivity setting means for setting the shooting sensitivity at the time of shooting,
The maximum sensitivity of the photographing sensitivity set by the sensitivity setting means sets the maximum gain amount within an adjustment range in which the image quality allowed by the gain means can be ensured, and the image size setting means by the pixel addition means A digital camera having sensitivity when pixel addition is performed with the maximum number of additions that can be set in the image size set in step 1 . A selection control means for allowing the user to select a plurality of levels of shooting sensitivity as selection candidates for the shooting sensitivity to be secured at the time of shooting;
The sensitivity setting means to set a photographic sensitivity should ensure imaging sensitivity this selection control means was selected by the user at the time of photographing
The digital camera according to claim 1, wherein the this. A display means,
The selection control means causes the display means to display a selection screen of a plurality of types of selection screens each indicating a selection candidate whose upper limit is different from each other, and any imaging sensitivity indicated as a selection candidate on the selection screen. Ru was selected to the user
The digital camera according to claim 2, wherein the this. A second selection control unit that allows the user to select one of a plurality of predetermined image sizes as the image size at the time of recording the subject image;
The image size setting means sets the image size selected by the user by the second selection control means as the image size at the time of recording the subject image. Digital camera. There are multiple shooting modes as settable shooting modes,
The image size setting means sets an image size determined in advance corresponding to a set shooting mode as an image size at the time of recording the subject image. The digital camera described. The imaging device supports two types of drive modes: a pixel addition mode in which signal charges of each pixel are added in the horizontal and / or vertical direction, and a normal mode in which the signal charges of each pixel are output without addition. And
The digital camera according to claim 1, wherein the pixel addition unit performs pixel addition processing on the subject image by driving the imaging device in the pixel addition mode. The sensitivity setting means amplifies the signal of the imaging element by the gain means without performing pixel addition processing by the pixel addition means, when it can cope with amplification of the signal of the imaging element by the gain means. The digital camera according to claim 1, wherein: If the sensitivity setting means is higher than the sensitivity that can be handled by amplification of the signal of the image sensor by the gain means, the maximum gain amount is set within an adjustment range in which the image quality allowed by the gain means can be secured, 8. The digital camera according to claim 1, wherein the pixel addition unit performs pixel addition with a value less than a maximum addition number that can be set in the image size set by the image size setting unit. Shooting sensitivity setting in a digital camera that records the subject image captured by the image sensor and amplifies the brightness of the subject image by performing pixel addition processing for adding a predetermined number of pixels to the subject image as necessary A method,
Amplifying the signal of the image sensor;
Setting an image size at the time of recording the subject image;
Including setting a shooting sensitivity at the time of shooting,
The maximum sensitivity of the photographing sensitivity set in the step of setting the photographing sensitivity is set to a maximum gain amount within an adjustment range in which an image quality allowed in the step of amplifying the signal of the image sensor can be secured, and An imaging sensitivity setting method characterized in that the sensitivity is obtained when pixel addition is performed with the maximum number of additions that can be set in the image size set in the step of setting the image size at the time of recording in pixel addition processing . A computer having a digital camera that records a subject image captured by an imaging device and amplifies the brightness of the subject image by performing pixel addition processing for adding a predetermined number of pixels to the subject image as necessary. ,
A process of amplifying the signal of the image sensor;
Processing for setting an image size at the time of recording the subject image;
Processing for setting the shooting sensitivity at the time of shooting,
The maximum sensitivity of the shooting sensitivity set in the process of setting the shooting sensitivity is set to the maximum gain amount within an adjustment range in which the image quality allowed by the process of amplifying the signal of the image sensor can be secured, and A program characterized by the sensitivity when pixel addition is performed with the maximum number of additions that can be set in the image size set in the process of setting the image size at the time of recording in the pixel addition process .

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