JP2010068046A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent brightness of digital image data for contrast AF from being different from that of a through image even when a contrast AF mode is entered by the start of a contrast AF operation for imaging operation while the through image is displayed. <P>SOLUTION: An imaging apparatus determines an amount of luminance variation as a difference between digital image data in the through image display and digital image data for contrast AF when the through image display mode is changed to the contrast AF mode, and corrects the digital image data for contrast AF to be displayed on an image display unit on the basis of the amount of luminance variation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to, for example, a digital single-lens reflex camera, and more particularly to digital image data when exposure control is switched between a live view display for displaying an image for monitoring during shooting and an image displayed during contrast AF. The present invention relates to an imaging apparatus that performs correction.

  In recent years, digital single-lens reflex cameras have advanced multi-functionality and high image quality, similar to digital cameras. Along with this, there is a demand for a digital single-lens reflex camera to display operations on a display device such as visual angle of view at the time of photographing and fine focus adjustment, as with an optical viewfinder. In response to this requirement, a digital single-lens reflex camera has a live view function, a live view function, which displays an image formed on an image sensor as a moving image image on a display device such as an LCD monitor or EVF. Is popular.

The live view display function usually reads out image charges while performing processing such as pixel thinning or pixel mixing at regular intervals on the charge generated by the image sensor, and determines the angle of view in shooting. In order to do so, it is finally displayed on a display device such as an LCD monitor or EVF.
The contrast AF function operates when the user presses the shutter halfway, acquires a through image while moving the focus position of the lens, calculates a contrast evaluation value from the image, and based on this contrast evaluation value To detect the focus position.
Each of the through image display function and the contrast AF function has exposure control suitable for each operation, and performs different exposure control. As techniques related to exposure control, there are, for example, Patent Documents 1 and 2.
Patent Document 1 provides a fixed metering mode and an adaptive metering mode for exposure control, sets the fixed metering mode when displaying a through image, and weights the horizontal contrast of a captured image based on a metering table. On the other hand, the adaptive metering mode is set at the time of shooting for recording, and the three metering tables are switched according to the position of the main subject detected by the contrast information of the AF area, and the fixed metering mode is set. It discloses that similar photometry is performed. As a result, Patent Document 1 can acquire an image in an appropriate exposure state at the time of shooting for recording. At the same time, in Patent Document 1, when the subject is moving at the time of displaying a through image, the exposure condition changes according to the change in the position of the subject. This prevents the brightness of display screens such as LCDs and EVFs that change the display from changing or flickering, and allows stable images to be displayed.

According to Patent Document 2, an appropriate exposure cannot always be obtained in response to a sudden change in the shooting environment, and as a result, an image may be skipped or crushed. It is disclosed that correction can be made. Patent Document 2 discloses that the brightness level of the through image is corrected based on the exposure setting value, and the display mode of the portion having the predetermined brightness level is changed in the through image with the corrected brightness level. .
JP 2001-272710 A JP 2007-208356 A

However, Patent Document 1 calculates each exposure condition suitable for the through image display and the recording shooting by changing the light metering method between the through image display and the recording shooting. No consideration is given to the exposure conditions during contrast AF.
Japanese Patent Application Laid-Open No. 2004-151561 corrects the brightness level of the through image based on the exposure setting value and performs display, but does not consider switching the exposure condition between the through image display and the contrast AF.

  The present invention has been made in view of such circumstances, and even when the exposure mode is switched due to the start of the contrast AF operation for the shooting operation while displaying a through image, the display screen for displaying the subject etc. through is displayed. Providing an imaging device that suppresses changes in brightness, prevents the appearance of through images during contrast AF and prevents deterioration in visibility, and can display high-quality through images even during contrast AF without causing an increase in price or complexity. The purpose is to do.

  An imaging apparatus according to a main aspect of the present invention includes an imaging unit that captures a subject image and outputs digital image data, an AE control unit that sets an exposure condition of the imaging unit, and digital image data obtained by the imaging unit An image display unit for displaying an image as a through image, an AF processing unit for detecting an AF evaluation value from digital image data obtained by the photographing unit, and an exposure of the imaging unit from the digital image data obtained by the imaging unit A luminance change detection unit that detects a luminance change amount of the image according to a change in conditions; and an image correction unit that corrects an image displayed on the image display unit based on the luminance change amount detected by the luminance change detection unit. When the AF evaluation value is not detected, the AE control unit sets the through-image display exposure condition, causes the image pickup unit to pick up an image, displays the image on the image display unit, and detects the AF evaluation value. AE control unit The AF processing unit sets exposure conditions for detection and causes the imaging unit to perform imaging. The image correction unit corrects the digital image data based on the luminance change amount detected by the luminance change detection unit and displays an image. Display on the screen.

  According to the present invention, even when the exposure mode is switched due to the start of the contrast AF operation for the shooting operation while displaying the through image, the luminance change of the display screen displaying the subject or the like is suppressed, and the contrast is controlled. It is possible to provide an imaging device that prevents the appearance and visibility of a through image during AF from being prevented and that can display a high-quality through image even during contrast AF without causing an increase in cost and complexity.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a functional block diagram of a digital single-lens reflex camera as an imaging apparatus. This digital single lens reflex camera includes a main body 1 and an interchangeable lens 2. The main body 1 and the interchangeable lens 2 can be attached to and detached from each other.
A lens-side system controller 3 is mounted on the interchangeable lens 2. The lens side system controller 3 is connected to a lens driving unit 4, an aperture driving unit 5, and a lens side communication control unit 6. The interchangeable lens 2 includes a lens 7 and a diaphragm 8. The lens 7 and the diaphragm 8 are disposed on the same optical axis.

The lens 7 includes a focus lens and a zoom lens. The lens 7 is controlled and driven by the lens driving unit 4. The lens driving unit 4 includes a motor and a motor driver, and is driven based on focus position data output from the AF processing unit 20 on the main body 1 side.
The diaphragm 8 is controlled and driven by the diaphragm driver 5. The aperture drive unit 5 includes a motor and a motor driver, and controls the diameter of the aperture 8 based on aperture value data output by the AE processing unit 19 on the main body 1 side.
Regarding the driving of the lens 7 and the diaphragm 8, the lens 7 and the diaphragm 8 are driven by performing data communication between the body 1 and the interchangeable lens 2 of the digital single-lens reflex camera.

  The lens side communication control unit 6 transmits and receives data to and from the main body 1. The lens side system controller 3 controls the lens driving unit 4, the aperture driving unit 5, and the lens side communication control unit 6, respectively.

A body-side system controller 10 is mounted on the main body 1. The body side system controller 10 includes a strobe control unit 11, a mechanical shutter drive unit 12, an image sensor drive unit 13, an input control unit 14, a user interface (UI) control unit 15, a body The side communication control unit 16 is connected. The body-side system controller 10 includes a memory 18, an AE processing unit 19, an AF processing unit 20, an image processing unit 21, a compression / expansion / contraction unit 22, a display control unit 23, and the like via a system bus 17. A recording medium control unit 24 is connected.
The main body 1 includes a strobe 25, a mechanical shutter 26, an image sensor 27, a liquid crystal display (LCD) 28, an EVF 29, a recording medium 30, a photometric sensor 31, a distance measuring sensor 32, a shutter button, and the like. And an operation button group 33 having. Further, the output terminal of the image sensor 27 in the main body 1 is connected to the system bus 17 via a correlated double sampling circuit (CDS) 34, an AMP 35, and an A / D converter 36.

The strobe 25 emits light and is controlled by the strobe controller 11.
The mechanical shutter 26 is driven by a mechanical shutter driving unit 12 including a motor and a motor driver. The mechanical shutter driving unit 12 controls the opening / closing of the mechanical shutter 26 according to the shutter speed data output from the AE processing unit 19 in accordance with the timing of the pressing signal of the shutter button of the operation button group 33 from the UI control unit 15. To do. Here, the UI control unit 15 receives and controls input information from a user interface for operating the camera by the user. The UI control unit 15 receives input information from a user interface including various buttons such as a shutter button, and transmits the input information to the body side system controller 10 to control the operation of the camera.

  The image sensor 27 has a photocathode formed by arranging a large number of light receiving elements in a matrix. The image sensor 27 receives the subject image formed by the lens 7 on the photoelectric surface and photoelectrically converts the subject image. The image sensor 27 has RGB color filters arranged in a mosaic pattern corresponding to the light receiving elements arranged in a matrix. The image sensor 27 reads out each charge accumulated for each pixel corresponding to each light receiving element in synchronization with the vertical transfer clock signal and the horizontal transfer clock signal supplied from the image sensor drive unit 13 and outputs them as an image signal. To do. The exposure time of charges in each pixel is controlled by an electronic shutter drive signal given from the image sensor drive unit 13. The image signal output from the image sensor 27 is subjected to noise removal by the CDS 34, gain adjustment is performed, amplified by the AMP 35, and converted into digital image data by the A / D converter 36.

The memory 18 is a working memory for temporarily writing digital image data acquired by A / D conversion by the A / D converter 36, for example.
The AE processing unit 19 reads the digital image data stored in the memory 18, calculates the luminance of the subject from the digital image data, and exposes the shutter speed data of the mechanical shutter 26, aperture value data of the aperture 8, and exposure conditions such as sensitivity. To decide. At the same time, the AE processing unit 19 adjusts the white balance of the digital image data read from the memory 18.
The aperture value data output from the AE processing unit 19 is converted into a communication command by the body side system controller 10 and sent to the body side communication control unit 16. The body side communication control unit 16 sends an aperture value data command to the lens side communication control unit 6 through the communication path 37. The lens-side system controller 3 receives the aperture value data command from the body-side system controller 10, and drives and controls the aperture drive unit 5 in accordance with this command to vary the diameter of the aperture 8.

  The AF processing unit 20 reads the digital image data written in the memory 18 and determines the focus position from the digital image data using the area information set by the UI control unit 15. In other words, when the shutter button of the user interface 33 is pressed (shooting instruction) by the user, the AF processing unit 20 receives the shooting instruction through the UI control unit 15 and is continuously written in the memory 18 according to the shooting instruction. The focus position data for driving the lens 7 is calculated by processing the obtained image data.

  The focus position data output from the AF processing unit 20 is converted into a communication command by the body side system controller 10 and sent to the body side communication control unit 16. The body side communication control unit 16 sends a command of focus position data to the lens side communication control unit 6 through the communication path 37. The lens-side system controller 3 receives a focus position data command from the body-side system controller 10, and drives and controls the lens driving unit 4 according to this command to move the position of the lens 7.

  The image processing unit 21 performs processing such as colorization on the digital image data written in the memory 18. Since the image sensor 27 is a single-plate image sensor, the digital image data written in the memory 18 needs to be colored. However, the image processing unit 21 performs interpolation operation on the digital image data to generate a luminance signal and a color difference signal to generate color image data, and further performs processing such as gamma correction, contrast intensity correction, and contour enhancement. I do.

  The compression / decompression unit 22 performs a compression process on the digital image data processed by the image processing unit 21 using a compression format such as JPEG to generate an image file. This image file is written in the recording medium 30 controlled by the recording medium control unit 24, for example. In the reproduction mode, the compression / decompression unit 22 reads an image file written on the recording medium 30 and performs decompression processing, and sends the decompressed image data to the display control unit 23.

  The display control unit 23 controls the LCD 28 or the EVF 29 to display image data. When the image data written in the memory 18 is displayed on the LCD 28 or the EVF 29 as a through image, the image data is displayed on the LCD 28 or the EVF 29. Convert to a format that can be displayed with. When the through image display mode is selected by the setting of the UI control unit 15, the display control unit 23 sequentially displays the image data updated at a predetermined interval in the memory 18 on the LCD 28 or the EVF 29 as a through image. At this time, the focus mode is set to contrast AF, and the focus mode is not changed during operation.

The body-side system controller 10 controls a series of imaging operations of the digital single-lens reflex camera. The body-side system controller 10 controls the operation timing of the strobe control unit 11, the mechanical shutter driving unit 12, and the image sensor driving unit 13. According to the timing of pressing the shutter button on the user interface 33 (shooting instruction) from the control unit 15, the flash 25 emits light, the mechanical shutter 26 opens and closes, and the charge readout from the image sensor 27 is controlled, and the CDS 34 and AMP 35. The digital image data is written in the memory 18 by controlling the operation of the A / D converter 36.
The body-side system controller 10 receives a user operation on the user interface 33 through the UI control unit 15, and when the through image display mode is selected by the user operation on the user interface 33, the through image is displayed on the LCD 28 or the EVF 29. To control. Further, when the body side system controller 10 half-presses the shutter button of the user interface 33, the body side system controller 10 shifts from the through image display mode to the contrast AF mode. When the body side system controller 10 is fully pressed with respect to the shutter button of the user interface 33, the body side system controller 10 performs control for performing actual photographing.

Further, the body side system controller 10 calculates and calculates a luminance correction amount for correcting the luminance of the digital image data for contrast AF when the through image display mode is shifted to the contrast AF mode, thereby obtaining a digital image for contrast AF. It corrects data and has a luminance change detection unit 10-1 and an image correction unit 10-2. Note that the luminance change detection unit 10-1 and the image correction unit 10-2 are functions included in the body-side system controller 10, but are shown outside the body-side system controller 10 in FIG. is there.
The luminance change detection unit 10-1 performs a through based on the difference between the digital image data at the time of live view display and the digital image data for contrast AF written in the memory 18 when the live view display mode is shifted to the contrast AF mode. A luminance change amount accompanying a change in exposure condition when the image display mode is shifted to the contrast AF mode is detected. In this case, the luminance change detection unit 10-1 detects the luminance distribution pattern of the shooting screen from the digital image data, and detects the luminance change amount based on the luminance pattern.
The image correction unit 10-2 corrects the digital image data for contrast AF displayed on the LCD 28 or the EVF 29 based on the luminance change amount detected by the luminance change detection unit 10-1.

Next, the operation of the camera configured as described above will be described with reference to a flowchart showing exposure control in the through image display mode and the contrast AF mode shown in FIG.
When the through image display mode is selected by the user, the through image display mode is sent to the body side system controller 10 through the UI control unit 15. The body side system controller 10 starts an operation for displaying a through image on the LCD 28 or the EVF 29. When the live view display operation is started, the digital single lens reflex camera is ready to shoot.

  However, the image sensor 27 receives the subject image formed by the lens 7 on the photoelectric surface, photoelectrically converts the subject image, and outputs it as an image signal. The image signal output from the image sensor 27 is subjected to noise removal by the CDS 34, gain adjustment is performed, amplified by the AMP 35, and converted into digital image data by the A / D converter 36. This digital image data is temporarily written in the memory 18.

  Next, when the live view display operation is started, the body side system controller 10 sets an exposure for live view display in step S1. In this through image display exposure setting, the AE processing unit 19 reads the digital image data stored in the memory 18, calculates the luminance of the subject from the digital image data, and uses the through image display exposure control value. The exposure conditions such as the electronic shutter speed, aperture value data of the aperture 8, and sensitivity set for the image sensor 27 are determined. The AF processing unit 20 reads the digital image data written in the memory 18 and determines a focus position from the digital image data using the area information set by the UI control unit 15.

  The body-side system controller 10 sends electronic shutter speed data set in the image sensor 27 to the image sensor drive unit 13, and transmits the aperture value data and focus position data of the aperture 8 from the body side communication control unit 16 through the communication path 37. The data is sent to the lens side communication control unit 6. The lens-side system controller 3 receives the aperture value data command from the body-side system controller 10, and drives and controls the aperture drive unit 5 in accordance with this command to vary the diameter of the aperture 8. At the same time, the lens-side system controller 3 receives a command of focus position data from the body-side system controller 10, and drives and controls the lens driving unit 4 according to this command to move the position of the lens 7.

  However, by setting the focus position of the lens 7, the diameter of the diaphragm 8, and the electronic shutter speed of the image sensor 27 under the determined exposure conditions, the image sensor 27 displays the subject image formed by the lens 7 in step S2. Light is received by the photocathode, and the subject image is photoelectrically converted and output as an image signal. The image signal output from the image sensor 27 is subjected to noise removal by the CDS 34, gain adjustment is performed, amplified by the AMP 35, and converted into digital image data by the A / D converter 36. This digital image data is temporarily written in the memory 18.

Next, in step S3, the image processing unit 21 performs interpolation operation on the digital image data written in the memory 18 to generate a luminance signal and a color difference signal to generate color image data, and further performs gamma correction. Processing such as contrast correction and contour enhancement is performed.
Next, in step S5, the display control unit 23 sequentially converts the digital image data updated and written in the memory 18 into a format that can be displayed on the LCD 28 or the EVF 29, and displays the digital image data on the LCD 28 or the EVF 29 as a through image. .

In parallel with the display of the live view image, the AE processing unit 19 reads the live view digital image data stored in the memory 18 in step S4, and the subject brightness used when the live view image is displayed from the digital image data. A subject luminance value for obtaining the value Bv and the exposure condition for the main photographing is calculated. Further, the AE processing unit 19 calculates a through image display exposure control value and a main photographing exposure control value according to the subject luminance value Bv and a predetermined program diagram. The through image display exposure control value and the actual photographing exposure control value are temporarily stored in the memory 18, respectively. As a result, the through-image exposure control value and the actual photographing exposure control value are stored in the memory 18 as appropriate exposure conditions reflecting the luminance value of the subject. Among these, the exposure control value for the through image is sequentially reflected in the exposure control when acquiring the digital image data for the through image.
Note that the calculation of the through image display exposure control value and the actual shooting exposure control value by the AE processing unit 19 is not limited to step S4, and when the through image is being displayed on the LCD 28 or the EVF 29, At any point.

  Next, in step S6, the body side system controller 10 determines whether or not the shutter button of the user interface 33 is half-pressed through the UI control unit 15 to switch to the contrast AF mode. If the result of this determination is that the shutter button of the user interface 33 has not been pressed halfway, the body side system controller 10 proceeds to step S7 and determines whether or not to end the through image display. If the result of this determination is that the live view display is not terminated, the body side system controller 10 returns to step S1 and continues the live view display. The through image display is continued until the end of the through image display is selected.

When the user presses the shutter button of the user interface 33 halfway with the through image displayed in this manner, the body side system controller 10 shifts from the through image display mode to the contrast AF mode in step S6. .
First, the body side system controller 10 performs exposure setting for exposure calculation for contrast AF in step S10. The exposure setting for the contrast AF uses the exposure setting for the through image display. Also, when the shooting mode is set to manual by the user or when the through image exposure correction is performed, the image used for the exposure calculation cannot be properly captured, so the exposure condition is set again. In other words, the AE processing unit 19 reads the digital image data written in the memory 18 at the time of displaying the through image, calculates the luminance of the subject from the digital image data, and obtains the through image display exposure control value. 27 determines the speed and sensitivity of the electronic shutter to be set to 27 and the exposure condition of aperture value data of the aperture 8. The AF processing unit 20 reads the digital image data written in the memory 18 and determines a focus position from the digital image data using the area information set by the UI control unit 15.

  The body-side system controller 10 sends data on the electronic shutter speed and sensitivity of the image sensor 27 to the image sensor drive unit 13 and transmits the aperture value data and focus position data of the aperture 8 from the body-side communication control unit 16 to the communication path. 37 to the lens side communication control unit 6. As a result, the lens-side system controller 3 drives and controls the lens driving unit 4 according to the focus position data to move the position of the lens 7, and drives and controls the diaphragm driving unit 5 according to the aperture value data to reduce the diameter of the diaphragm 8. Make it variable.

  However, with the focus position of the lens 7, the diameter of the diaphragm 8, the electronic shutter speed and sensitivity of the image sensor 27 set according to the determined exposure conditions, the image sensor 27 captures the subject image formed by the lens 7 in step S11. Is received by the photocathode, and the subject image is photoelectrically converted and output as an image signal. The image signal output from the image sensor 27 is subjected to noise removal by the CDS 34, gain adjustment is performed, amplified by the AMP 35, and converted into digital image data by the A / D converter 36. This digital image data is temporarily written in the memory 18 as contrast AF exposure calculation data.

  Next, in step S12, the AE processing unit 19 reads out the contrast AF exposure calculation digital image data stored in the memory 18, calculates the subject brightness value Bv from the digital image data, and further, the subject brightness value Bv. And an exposure control value for contrast AF is calculated according to a predetermined program diagram and a control table. This exposure control value for contrast AF is sequentially reflected in exposure control when acquiring digital image data for calculating contrast AF exposure. The exposure control value for contrast AF is temporarily written in the memory 18.

  Next, in step S <b> 13, the body side system controller 10 sends the contrast AF exposure control value temporarily written in the memory 18 to the image sensor driving unit 13 and also from the body side communication control unit 16 to the communication path 37. To the lens side communication control unit 6. As a result, the lens-side system controller 3 drives and controls the diaphragm drive unit 5 in accordance with the exposure control value for contrast AF to vary the diameter of the diaphragm 8. Thereby, exposure setting for contrast AF is performed.

  Next, under the exposure setting for contrast AF, the body side system controller 10 performs a subject imaging operation in step S14. That is, the image sensor 27 captures the subject image formed by the lens 7 and outputs the image signal. The image signal output from the image pickup device 27 is subjected to noise removal by the CDS 34, gain adjustment is performed, amplified by the AMP 35, converted into digital image data for contrast AF by the A / D converter 36, and stored in the memory 18. Written temporarily.

Next, the AF processing unit 20 reads the digital image data for contrast AF written in the memory 18 and determines the focus position from the digital image data for contrast AF using the area information set by the UI control unit 15. To do.
Next, in step S15, the body-side system controller 10 issues a command to the luminance change detection unit 10-1 and the image correction unit 10-2, and for contrast AF when the through image display mode is shifted to the contrast AF mode. A luminance correction amount for correcting the luminance of the digital image data is calculated and obtained. In other words, the luminance change detection unit 10-1 makes a difference between the digital image data at the time of live view display and the digital image data for contrast AF written in the memory 18 when shifting from the live view display mode to the contrast AF mode. From the through image display mode to the contrast AF mode, a luminance change amount associated with a change in exposure condition is detected. In this case, the luminance change detection unit 10-1 detects the luminance distribution pattern of the shooting screen from the digital image data, and detects the luminance change amount based on the luminance pattern.
Next, the image correcting unit 10-2 corrects the digital image data for contrast AF displayed on the LCD 28 or the EVF 29 based on the luminance change amount detected by the luminance change detecting unit 10-1.

Here, the operation of correcting the digital image data for contrast AF will be specifically described.
FIG. 3 is a diagram for explaining a process of detecting a luminance change amount when the through image display mode is shifted to the contrast AF mode. The number of pixels of the image sensor 27 is, for example, x pixels in the horizontal direction and y pixels in the vertical direction, and the total number of pixels is x × y. Normally, the number of pixels of the digital image data acquired by the imaging device 27 during the live view display and the contrast AF mode operation is the number of pixels y / n in the vertical direction and the number of pixels x / n in the horizontal direction, respectively. Reduced image data DS is obtained by reducing the size. Here, n is the number of pixels with a small ratio between the image sensor 27, the LCD 28, and the EVF 29. At this time, the reduction processing of the image data is performed by, for example, thinning out, pixel addition, or the like.

  As shown in the AE processing area in FIG. 3, the AE processing unit 19 divides the reduced image data DS into a plurality of areas each having a predetermined size, and the average luminance for each of the divided areas. Calculate the value. For example, the AE processing unit 19 divides the reduced image data DS into a plurality of grid-like areas perpendicular to the x and y directions, for example, a plurality of 7 × 7 areas, and the average luminance value Bv0 for each of these areas. ~ Bv48 is calculated. 4A shows an example of the luminance distribution of a plurality of average luminance values Bv0 to Bv48 at the time of live view display calculated by the AE processing unit 19, and FIG. 4B shows the average of each area in the contrast AF mode. An example of the luminance portion of the luminance values Bv0 to Bv48 is shown.

  As shown in the AF processing area in FIG. 3, the AF processing unit 20 divides the reduced image data DS into a plurality of areas with a predetermined size as a unit, and each of the divided plurality of areas. AF evaluation values Ha to Hk are calculated. Contrast AF is executed based on the AF evaluation values Ha to Hk.

  On the other hand, as shown in FIGS. 4A and 4B, when the luminance distribution in the through image display is compared with the luminance distribution in the contrast AF mode, the luminance distribution in the contrast AF mode is the luminance in the through image display. The luminance distribution has an average luminance value Bv that is generally larger than the distribution. With such a luminance distribution in the contrast AF mode, when the digital image data acquired in the contrast AF mode operation is displayed on the LCD 28 or EVF 29, the image displayed on the LCD 28 or EVF 29 is the LCD 28 or The image is brighter than the image displayed on the EVF 29. For this reason, it is necessary to correct the digital image data acquired during the contrast AF mode operation.

  However, the brightness change detection unit 10-1 shows the brightness distribution of the plurality of average brightness values during the live view display shown in FIG. 4A when the live view display mode is shifted to the contrast AF mode. The difference between the brightness distribution of the plurality of average brightness values in the contrast AF mode shown in FIG. As a result, the amount of change in luminance associated with the change in exposure conditions when shifting from the through image display mode to the contrast AF mode is calculated. Here, the greater the difference between the luminance change amount, that is, the luminance distribution during live view display and the luminance distribution during contrast AF mode, the greater the correction amount for the digital image data displayed on the LCD 28 or EVF 29. On the other hand, when the difference is small and the luminance change amount is close to “0”, the correction amount is small.

  FIGS. 5A, 5B, and 5C show the input / output relationship during correction for the digital image data. Corrections to digital image data are classified into, for example, three patterns. The first pattern is a case where the amount of change in luminance, which is the difference between the luminance distribution of the plurality of average luminance values during live view display and the luminance distribution of the plurality of average luminance values in the contrast AF mode, is small, and at the time of proper exposure. is there. The input data output characteristic of the correction for the digital image data at the appropriate exposure is equal between the input signal and the output signal as shown in FIG. 5A, and does not change between the through image display and the contrast AF mode. Indicates.

  The second pattern is a case where the amount of change in luminance, which is the difference between the luminance distribution during live view display and the luminance distribution during contrast AF mode, is a negative value. The contrast is different between live view display and contrast AF mode. This is an underexposure when the brightness in the AF mode is reduced. As shown in FIG. 5B, the input data output characteristic of the correction for the digital image data at the time of underexposure is such that the rate of increase of the output signal is reduced as the input signal is increased. A γ curve that brightens the image in the AF mode is shown. Note that the input data output characteristic of this correction has a large amount of change in luminance when the γ curve rises.

  The third pattern is a case where the amount of change in luminance, which is the difference between the luminance distribution during live view display and the luminance distribution during contrast AF mode, has a positive value, and contrast AF between live view display and contrast AF. When the mode is overexposed, the brightness becomes brighter. The input data output characteristic of the correction for the digital image data at the time of overexposure increases the rate of increase of the output signal as the input signal increases as shown in FIG. A γ curve that darkens the image during AF is shown. Note that the input data output characteristic of this correction has a small amount of change in luminance when the γ curve rises.

Therefore, if the first pattern at the appropriate exposure with a small amount of luminance change, which is the difference between the live view display calculated by the luminance change detection unit 10-1 and the operation in the contrast AF mode, the image correction unit 10 is used. -2 performs correction on digital image data according to a γ curve having input data output characteristics that do not change between the through image display and the contrast AF mode as shown in FIG.
If the second pattern at the time of underexposure in which the luminance change amount, which is the difference between the live view display calculated by the luminance change detection unit 10-1 and the operation in the contrast AF mode, becomes a negative value, image correction is performed. The unit 10-2 corrects the digital image data according to a γ curve having an input data output characteristic that brightens the image in the contrast AF mode as compared to the through image display as shown in FIG.
If it is the third pattern at the time of overexposure when the brightness change amount, which is the difference between the live view display calculated by the brightness change detection unit 10-1 and the operation in the contrast AF mode, becomes a positive value, image correction is performed. The unit 10-2 corrects the digital image data according to a γ curve having an input data output characteristic that darkens the image at the time of contrast AF as compared to the through image display as shown in FIG. The correction method may be performed using a table in addition to the method of changing the γ curve. Further, the image correction unit 10-2 shown in FIG. 1 may incorporate the correction function in the display control unit 23.

FIG. 6 shows the switching operation timing between the live view display and the contrast AF mode. The display frame timing indicates that one frame image is displayed at a frame interval tv. The through image / contrast AF indicates whether it is a through image display or a contrast AF mode, shows a through image display in a low level period, and shows a contrast AF mode in a high level period. The exposure setting indicates the time required for the exposure setting in the high level period. The exposure indicates the time required for exposure in the high level period. Reading indicates the time required for reading in a high level period. The display image generation indicates the time required for display image generation in the high level period.
The correction amount detection / display image correction operates only in the contrast AF mode, and indicates the time required for calculating the correction amount and correcting the digital image data in the high level period. The corrected display image indicates that the digital image data corrected in the high level period is displayed on the LCD 28 or the EVF 29.

  Therefore, when the through image / contrast AF is at the high level and the mode is switched to the contrast AF mode, as described above, the luminance change detection unit 10-1 performs the through image during the high level period of the correction amount detection / display image correction. From the difference between the digital image data at the time of display and the digital image data for contrast AF, the amount of change in luminance accompanying the change in exposure conditions when the through image display mode is shifted to the contrast AF mode is detected. Next, the image correcting unit 10-2 corrects the digital image data for contrast AF displayed on the LCD 28 or the EVF 29 based on the luminance change amount detected by the luminance change detecting unit 10-1.

  In this way, the display frame timing, through image / contrast AF, exposure setting, reading, display image generation, and correction amount detection / display image correction are performed on the display frame timing. That is, if the exposure is appropriate, the digital image data is corrected according to the γ curve that does not change between the through image display and the contrast AF mode as shown in FIG. If the image is underexposed, the digital image data is corrected according to a γ curve that brightens the image in the contrast AF mode as compared to the through image display as shown in FIG. If overexposed, the digital image data is corrected in accordance with a γ curve that darkens the image at the time of contrast AF as compared to the through image display as shown in FIG. Thereby, even if the through image display and the contrast AF mode are switched, the brightness of the image displayed on the LCD 28 or the EVF 29 is not changed.

However, the image correcting unit 10-2 of the image processing unit 21 receives the digital image data for contrast AF displayed on the LCD 28 or the EVF 29 based on the luminance change amount detected by the luminance change detecting unit 10-1 in step S16. to correct. At this time, the effect of correction on the digital image data for contrast AF is reflected only in the through image displayed on the LCD 28 or EVF 29, and does not affect the focus position detection process.
Next, in step S <b> 17, the image processing unit 21 sends the contrast AF digital image data corrected by the correction amount to the display control unit 23. As a result, the display control unit 23 displays the corrected digital image data for contrast AF on the LCD 28 or the EVF 29.

  Next, in step S18, the body side system controller 10 determines whether or not an instruction to end the contrast AF mode is received from the user interface 33 through the UI control unit 15. As a result of this determination, if no instruction to end the contrast AF mode is received from the user interface 33, the body side system controller 10 returns to step S10, and displays the corrected digital image data for contrast AF on the LCD 28 or EVF 29. Continue. Upon receiving an instruction to end the contrast AF mode from the user interface 33, the body side system controller 10 returns to step S1 and switches from the contrast AF mode to the through image display mode.

  As described above, according to the first embodiment, when the through image display mode is shifted to the contrast AF mode, the luminance that is the difference between the digital image data at the time of displaying the through image and the digital image data for contrast AF is displayed. The amount of change is obtained, and the digital image data for contrast AF displayed on the LCD 28 or EVF 29 is corrected based on the amount of change in luminance. Accordingly, even when the through image is displayed and the contrast AF mode is switched by the start of the contrast AF operation for the photographing operation, the brightness of the digital image data for contrast AF displayed on the LCD 28 or the EVF 29 is There is no fluctuation compared with the brightness of the live view image. However, the brightness change of the display screen that displays the subject etc. in contrast AF mode can be suppressed, the through image looks good in contrast AF, and the visibility is prevented from being lowered, and a high quality through image is displayed even in contrast AF. it can. Since the digital image data for contrast AF is only corrected based on the luminance change amount that is the difference between the digital image data at the time of live view display and the digital image data for contrast AF, there is no need to provide a separate unit or the like. , Without increasing the price or complexity.

Next, a second embodiment of the present invention will be described with reference to the drawings.
The second embodiment differs from the first embodiment in the method of detecting a luminance change. In other words, the luminance change detection unit 10-1 determines the difference between the appropriate exposure during live view display and the exposure in the contrast AF mode based on a predetermined exposure condition calculation formula when the live view display mode is shifted to the contrast AF mode. An amount is detected, and a luminance change amount is detected based on the amount of deviation.

If the amount of deviation is small and the exposure is appropriate, the image correction unit 10-2 does not correct the digital image data.
If the divergence amount is a negative value and the image is underexposed, the image correction unit 10-2 makes the input data output characteristic that brightens the image in the contrast AF mode as compared to the through image display as shown in FIG. The digital image data is corrected according to a γ curve having
If the divergence amount is a positive value and the image is overexposed, the image correction unit 10-2 has an input data output characteristic that darkens the image at the time of contrast AF as compared to the through image display as shown in FIG. The digital image data is corrected according to the γ curve.

FIG. 7 shows a program diagram during live view display. In the figure, Sv represents the sensitivity set in the image sensor 27 for the luminance value Bv of the subject, Tv represents the shutter speed, and Av represents the aperture value.
Since a proper exposure is normally obtained when a through image is displayed, the sensitivity Sv, the luminance value Bv, the shutter speed Tv, and the aperture value Av are:
Bv + Sv = Tv + Av (1)
The relationship holds.

On the other hand, in the contrast AF mode, a P diagram of a through image display is used, but control is performed so that a fixed shutter speed is used within a range of luminance values of a specific subject.

  Table 1 shows the relationship between the brightness of the subject and the shutter speed in the contrast AF mode. When the subject brightness Bv is “Bv ≧ 6” and “Bv <0”, the operation is performed according to the program diagram.

When the subject brightness Bv is “6> Bv ≧ 3”, for example, the shutter speed is set to 1/100, and when the subject brightness Bv is “3> Bv ≧ 0”, the shutter speed is set to 1/50. . At this time, since the shutter speed is fixed when the subject brightness Bv is “6> Bv ≧ 0”, the control deviates from the program diagram, and the sensitivity Sv, the brightness value Bv, the shutter speed Tv, and the aperture value Av are set. Is
Bv + Sv ≠ Tv + Av (2)
As a result, the exposure is inappropriate for a through image. For this reason, the image displayed on the LCD 28 or the EVF 29 becomes over or under as shown in FIGS. 8A, 8B, and 8C, for example.

However, if the shutter speed in the through image display mode at the same subject brightness is Tv1, and the shutter speed in the contrast AF mode is Tv2, the deviation from the appropriate exposure is
ΔTv = Tv1-Tv2 (3)
Is obtained by calculating.

When the deviation amount ΔTv is “0”, the exposure is in an appropriate state and no correction is performed.
On the other hand, when the divergence amount ΔTv> 0, the overexposure occurs, so that the correction process is performed in the same manner as the overexposure in the first embodiment. That is, if overexposed, the digital image data is corrected according to a γ curve that darkens the image at the time of contrast AF as compared to the through image display as shown in FIG.
When the deviation amount ΔTv <0, the underexposure is caused. Therefore, the luminance correction of the display image is suppressed by performing the same correction process as in the case of the underexposure in the first embodiment. That is, if the image is underexposed, the digital image data is corrected according to the γ curve that brightens the image in the contrast AF mode as compared to the through image display as shown in FIG.

  However, even if the through image display and the contrast AF mode are switched, the brightness of the image displayed on the LCD 28 or the EVF 29 is not changed.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a functional block diagram showing a first embodiment of a digital single lens reflex camera as an imaging apparatus according to the present invention. 6 is a flowchart showing exposure control in a through image display mode and a contrast AF mode in the apparatus. The figure for demonstrating the detection process of the brightness | luminance variation | change_quantity when it transfers to the contrast AF mode from the through image display mode in the same apparatus. The figure which shows an example of distribution of the some average luminance value computed by the AE process part in the apparatus. The figure which shows the input / output relationship at the time of correction | amendment with respect to the digital image data according to the luminance variation of the luminance distribution at the time of the through image display in the same apparatus, and the luminance distribution at the time of contrast AF mode. The figure which shows the switching operation | movement timing of the through image display and contrast AF mode in the same apparatus. The program diagram at the time of the through image display in 2nd Embodiment of the digital single-lens reflex camera as an imaging device which concerns on this invention. The figure which shows an example of overexposure and underexposure as a through image of improper exposure in the same apparatus.

Explanation of symbols

  1: main body, 2: interchangeable lens, 3: lens side system controller, 4: lens drive unit, 5: aperture drive unit, 6: lens side communication control unit, 7: lens, 8: aperture, 10: body side system controller 11: Strobe control unit, 12: Mechanical shutter (mechanical shutter) drive unit, 13: Image sensor drive unit, 14: Input control unit, 15: User interface (UI) control unit, 16: Body side communication control unit, 17 : System bus, 18: Memory, 19: AE processing unit, 20: AF processing unit, 21: Image processing unit, 22: Compression / expansion unit, 23: Display control unit, 24: Recording medium control unit, 25: Strobe, 26 : Mechanical shutter, 27: Image sensor, 28: Liquid crystal display (LCD), 29: EVF, 30: Recording medium, 31: Photometric sensor, 32: Distance sensor 33: Operation button group, 34: Correlated double sampling circuit (CDS), 35: AMP, 36: A / D converter, 37: Communication path, 10-1: Brightness change detection unit, 10-2: Image correction unit .

Claims (10)

An imaging unit that captures a subject image and outputs digital image data;
An AE control unit for setting an exposure condition of the imaging unit;
An image display unit for displaying the digital image data obtained by the imaging unit as a through image;
An AF processing unit for detecting an AF evaluation value from the digital image data obtained by the photographing unit;
A luminance change detection unit that detects a luminance change amount of an image accompanying a change in an exposure condition of the imaging unit from the digital image data obtained by the imaging unit;
An image correction unit that corrects an image to be displayed on the image display unit based on the luminance change amount detected by the luminance change detection unit;
Comprising
When the AF evaluation value is not detected, the AE control unit sets an exposure condition for the through image display, causes the imaging unit to perform imaging, and displays the image on the image display unit.
When detecting the AF evaluation value, the AE control unit sets an exposure condition for detection of the AF processing unit to cause the imaging unit to perform imaging, and the image correction unit detects the luminance change. Correcting the digital image data based on the amount of change in luminance detected by the unit and causing the image display unit to display the corrected data.
An imaging apparatus characterized by that.   The imaging apparatus according to claim 1, wherein the luminance change detection unit detects a luminance distribution pattern of a shooting screen from the digital image data, and detects a luminance change amount based on the luminance pattern.   The luminance change detection unit, when transitioning from the through image display mode to the contrast AF mode, determines the exposure condition from the difference between the digital image data during the through image display and the digital image data during the contrast AF mode. The imaging apparatus according to claim 1, wherein the luminance change amount associated with the change is detected. If the brightness change amount detected by the brightness change detection unit is small and appropriate exposure,
The image correction unit corrects the digital image data according to input data output characteristics having a γ curve that does not change between the through image display and the contrast AF mode.
The imaging apparatus according to claim 3. If the brightness change amount detected by the brightness change detection unit is under-exposed,
The image correction unit corrects the digital image data according to a γ curve having an input data output characteristic that brightens the image in the contrast AF mode than in the through image display;
The imaging apparatus according to claim 3. If the brightness change amount detected by the brightness change detection unit is overexposed,
The image correction unit corrects the digital image data according to a γ curve having an input data output characteristic that darkens the image at the time of the contrast AF than at the time of the through image display.
The imaging apparatus according to claim 3.   The luminance change detection unit detects a deviation amount from an appropriate exposure at the time of displaying the through image based on a predetermined exposure condition calculation formula, and detects the luminance change amount based on the deviation amount. The imaging device according to claim 1. If the deviation detected by the luminance change detector is small and the exposure is appropriate,
The image correction unit does not correct the digital image data;
The imaging apparatus according to claim 7. If the divergence amount detected by the luminance change detection unit is a condition that is overexposed,
The image correction unit corrects the digital image data according to a γ curve having an input data output characteristic that darkens the image at the time of the contrast AF than at the time of the through image display.
The imaging apparatus according to claim 7. If the divergence detected by the luminance change detection unit is underexposed,
The image correction unit corrects the digital image data according to a γ curve having an input data output characteristic that brightens the image in the contrast AF mode than in the through image display;
The imaging apparatus according to claim 7.

Images