JP5335452B2 - IMAGING DEVICE, IMAGING DEVICE CONTROL METHOD, AND PROGRAM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus, a control method and a program which enable a dark subject to be photographed in a light state and suppress the phenomenon that the sky in the background is photographed to be whitish. <P>SOLUTION: The imaging apparatus includes an imaging element 14, an image processing circuit 20, an exposure control circuit 40, a system control unit 50, a longitudinal position detection sensor 75, etc. The system control unit 50 detects luminance of a face area of image data obtained by imaging the subject by the imaging element 14 and luminance of a sky area positioned at an upper position in the image data. Further, the system control unit 50 calculates a face correction value by adding a value corresponding to the difference between the luminance of the sky area and a permissible luminance upper-limit value of the sky area to a difference between the luminance of the face area and a luminance target value of the face area, and controls exposure based upon a value corresponding to the face correction value. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to an imaging apparatus having a function of detecting a subject area from image data obtained by photographing an object, a control side Ho及 beauty programs of the imaging apparatus.

  2. Description of the Related Art Conventionally, there is an imaging device (digital camera) having an automatic exposure control function that automatically determines exposure based on image data obtained by photographing a subject. As a photometric method performed for automatic exposure control in the imaging device, for example, photometry performed by averaging the luminance of the entire image data, or by dividing the image data into a plurality of blocks and weighting each block for photometry. There is multi-segment photometry. In addition, there are center-weighted metering in which metering is performed with emphasis on the center of image data, spot metering for metering only an arbitrary range in the center of image data, and the like.

  In addition, in order to ensure that the luminance of the main subject that is the main shooting target in the subject is appropriate, the photographer is instructed to specify the main subject area where the main subject exists using the screen of the image display unit. There is an imaging device that adjusts the exposure according to the luminance of the main subject area.

  Further, for example, a face is automatically detected from the image data obtained by photographing the subject as a main subject by a technique such as shape analysis, and automatic exposure control is performed so that the detected face is exposed appropriately. An imaging device has been proposed (see, for example, Patent Document 1). In the imaging apparatus described in Patent Document 1, even when the brightness of the entire image data is appropriate, if the face is under (blackish (dark)), the entire image data is brightened, and the face is over (white) Control is performed to darken the entire image data. In this way, shooting can be performed so that the luminance of the main subject is appropriate in various shooting scenes.

  However, in the above method, since the exposure is controlled so that the brightness of the face detected from the image data obtained by photographing the subject is appropriate, the background is overexposed even if the face brightness is appropriate. Or it may be under. In such a case, there has been a problem that when the entire image is viewed, it becomes a failed image.

  Conventionally, the brightness is also adjusted by performing image processing on the failed image as described above. However, in general, in the case of overexposure, the contrast of the image after image processing is lower than that in the case of underexposure, so that an image with a blurred impression is often obtained.

  Therefore, an imaging apparatus for suppressing the overexposure as described above has been proposed (see, for example, Patent Document 2). In the imaging apparatus described in Patent Document 2, when automatic exposure control is performed based on the detection result of the main subject, the luminance of the entire image data is compared with the luminance of the main subject region in the image data, and the higher luminance is more appropriate. By controlling the exposure so that it becomes a value, it is possible to prevent one from being overexposed.

JP 2003-107555 A JP 2008-70562 A

  However, in the imaging apparatus described in Patent Document 2, when the brightness of the entire image data and the brightness of the main subject region are extremely different, exposure control is performed even if exposure control is performed based on the entire photometric value and the subject photometric value. In some cases, it was insufficient.

  For example, in a shooting scene in which a person and the sky are reflected, if the exposure is adjusted to the overall photometric value, the person will be too dark, or conversely if the exposure is adjusted to the photometric value of the person, the sky will be overexposed. There was a problem (a phenomenon in which the sky appears whitish).

  If the lighting used for shooting is artificial, there is often no problem with the composition even if the brightness of the lighting is overexposure. Are often included in the angle of view. For this reason, when one of the person and the sky is set to an appropriate luminance and the other luminance fails, it cannot often be said that the image has a preferable composition.

An object of the present invention, along with making it possible to brightly shoot dark subject, possible to suppress the phenomenon that the empty background objects appear whitish and an imaging device, to provide a control side Ho及 beauty programs of the imaging apparatus It is in.

In order to achieve the above object, an imaging apparatus according to the present invention includes a detecting unit that detects a main subject region from image data obtained by imaging a subject with an image sensor, and a luminance of the main subject region of the image data. , Photometric means for detecting the brightness of the sky area located above the image data, and a value corresponding to the difference between the brightness of the sky area and the allowable brightness upper limit value of the sky area, the brightness of the main subject area and the In addition to calculating the main subject exposure correction value by adding to the difference in the luminance target value of the main subject area, and when imaging with the imaging element based on the value according to the main subject exposure correction value And a control means for controlling the exposure.

According to the present invention, it becomes possible to brightly shoot darker subject, it is possible to suppress the phenomenon of air objects appear whitish background.

It is a block diagram which shows the structure of the imaging device which concerns on embodiment of this invention. It is a flowchart which shows the whole operation | movement of an imaging device. 3 is a flowchart showing details of still image recording mode processing of FIG. 2. It is a flowchart which shows the detail of the photometry process of FIG. It is a flowchart which shows the detail of the photometry process of FIG. FIG. 4 is a flowchart illustrating details of imaging processing in FIG. 3. FIG. It is a flowchart which shows the detail of the backlight correction value DeltaBvC calculation process of FIG. 4a. It is a flowchart which shows the detail of the backlight correction value DeltaBvC calculation process of FIG. 4a. It is a flowchart which shows the detail of the empty correction value DeltaBvS calculation process of FIG. 4a. It is a flowchart which shows the detail of the empty correction value DeltaBvS calculation process of FIG. 4a. It is a flowchart which shows the detail of the whole brightness | luminance correction value DeltaBvAll calculation process of FIG. 4a. It is a flowchart which shows the detail of the face correction value DeltaBvFace calculation process of FIG. 4a. (A), (b), (c), (d) is a figure which shows the relationship between a whole luminance correction value and a face correction value. (A), (b) is a figure which shows an example of an area | region definition. (A), (b) is a figure which shows an example of a photometric weight definition.

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

  FIG. 1 is a block diagram showing a configuration of an imaging apparatus according to an embodiment of the present invention.

  In FIG. 1, an imaging apparatus 100 is configured as a digital camera, and includes a photographic lens 10, a shutter 12, an imaging element 14, an image processing circuit 20, a system control unit 50, a vertical position detection sensor 75, and the like, and a recording medium. 200 is built-in. In the following configuration of the imaging apparatus 100, descriptions of parts that are not directly related to the present invention are simplified or omitted.

  The imaging device 14 converts an optical image of a subject imaged through a photographing lens 10 and a shutter 12 having a diaphragm function into an electric signal when photographing a photographing target (subject). The lens barrier 102 prevents the imaging unit from being dirty or damaged by covering the imaging unit (including the imaging lens 10 and the imaging element 14). The A / D converter 16 converts the analog signal output from the image sensor 14 into a digital signal. The timing generation circuit 18 is controlled by the memory control circuit 22 and the system control unit 50, and supplies a clock signal and a control signal to the image sensor 14, A / D converter 16, and D / A converter 26.

  The image processing circuit 20 performs predetermined pixel interpolation processing and color conversion processing on the image data output from the A / D converter 16 or the memory control circuit 22. The image processing circuit 20 performs predetermined arithmetic processing using the captured image data, and performs TTL (through-the-lens) AF (autofocus) processing, AE (automatic exposure) processing, and EF (flash pre-processing). (Emission) processing. In this case, the system control unit 50 controls the exposure control circuit 40 and the distance measurement control circuit 42 based on the calculation result of the image processing circuit 20.

  Further, the image processing circuit 20 performs predetermined calculation processing using the captured image data, and also performs TTL AWB (auto white balance) processing based on the calculation result. Further, the image processing circuit 20 includes a face detection circuit (detection means), detects a human face area from the image data output from the A / D converter 16 or the memory control circuit 22, and is detected. Information related to the face area is notified to the system control unit 50.

  The memory control circuit 22 controls the A / D converter 16, the timing generation circuit 18, the image processing circuit 20, the image display memory 24, the D / A converter 26, the memory 30, and the compression / decompression circuit 32. The image data output from the A / D converter 16 is written into the image display memory 24 or the memory 30 via the image processing circuit 20 and the memory control circuit 22 or directly via the memory control circuit 22.

  The image display unit 28 is composed of a TFT LCD or the like, and displays display image data written in the image display memory 24 and output via the D / A converter 26. Further, the image display unit 28 can perform through display for displaying an image corresponding to the image data output from the imaging unit. If the captured images are sequentially displayed by the image display unit 28, the electronic viewfinder function can be realized. The image display unit 28 can arbitrarily turn on / off the display according to an instruction from the system control unit 50.

  The memory 30 stores a still image or a moving image obtained by shooting a shooting target, and has a storage capacity sufficient to store a predetermined number of still images or a moving image for a predetermined time. Thereby, even in the case of continuous shooting or panoramic shooting in which a plurality of still images are continuously shot, a large amount of image writing can be performed on the memory 30 at high speed. The memory 30 can also be used as a work area for the system control unit 50.

  The compression / decompression circuit 32 reads the image data stored in the memory 30, performs compression processing or expansion processing by adaptive discrete cosine transform (ADCT), wavelet transform, etc., and writes the processed image data to the memory 30. . The encryption / decryption circuit 34 performs an encryption process on the image data stored in the predetermined area of the memory 30 as necessary, and stores the encrypted image data in the predetermined area of the memory 30. Decoding processing is performed when image data is reproduced and displayed.

  The exposure control circuit 40 controls the shutter 12 and also has a flash light control function in cooperation with the flash 48. The distance measurement control circuit 42 controls the focusing of the photographic lens 10. The zoom control circuit 44 controls zooming of the taking lens 10. The lens barrier control circuit 46 controls the operation of the lens barrier 102. The flash 48 also has an AF auxiliary light projecting function and a flash light control function. The exposure control circuit 40 and the distance measurement control circuit 42 are controlled using the TTL method.

  A system control unit 50 (calculation unit, control unit) controls the entire imaging apparatus 100. Further, the system control unit 50 controls the exposure control circuit 40 and the distance measurement control circuit 42 based on the calculation result obtained by calculating the captured image data by the image processing circuit 20. Further, the system control unit 50 executes processing shown in each flowchart described later based on the program of the present invention.

  The system memory 52 stores constants and variables for operation of the system control unit 50, the program of the present invention, and the like. The nonvolatile memory 56 is composed of, for example, an EEPROM, a flash memory, etc., and stores data.

  The display unit 54 includes an LCD, an LED, a sound generation element, and the like, and notifies an operation state, a message, and the like using characters, images, sounds, and the like according to execution of a program by the system control unit 50. Further, the display unit 54 is provided with a part of its function in the optical viewfinder 104. The display content of the display unit 54 is omitted. The power switch (main switch) 60 is operated when the power of the imaging apparatus 100 is switched ON / OFF and the power of various accessories connected to the imaging apparatus 100 is switched ON / OFF.

  The first shutter switches SW1 and 62 are operated when the first shutter switch signal SW1 is turned ON during the operation of a shutter button (not shown) and an operation start such as AF processing, AE processing, AWB processing, and EF processing is instructed. To do. The second shutter switch SW2, 64 is operated when the second shutter switch signal SW2 is turned ON upon completion of the operation of the shutter button, and an operation start of a series of processing (exposure processing, development processing, recording processing) is instructed.

  Here, the exposure process is a process of writing a signal read from the image sensor 14 as image data in the memory 30 via the A / D converter 16 and the memory control circuit 22. The development process is a process using computations in the image processing circuit 20 and the memory control circuit 22. The recording process is a process of reading image data from the memory 30, compressing the image data by the compression / decompression circuit 32, and writing the image data to the recording medium 200.

  The operation unit 70 includes various buttons (menu button, set button, AF frame setting operation member, etc.), various switches (compression mode switch, REC review switch, etc.), a touch panel, and the like. Details of various buttons and switches are omitted. The mode changeover switch 72 is operated when switching setting of various function modes (automatic photographing mode, photographing mode, panoramic photographing mode, still image recording mode, moving image recording mode, reproduction mode, PC connection mode, etc.).

  The vertical position detection sensor 75 (detection means) is configured such that the posture of the imaging apparatus 100 is a vertical position (for example, a posture in which a digital camera that is normally used in a horizontal state is in a vertical state) or a horizontal position (a digital camera is It is detected whether the posture is in the horizontal position). Based on the detection result of the vertical position detection sensor 75, the system control unit 50 determines a background sky area, which is an upper area in image data obtained by imaging the subject with the imaging element 14. Further, the system control unit 50 determines a background sky area, which is an upper area in the image data, based on the luminance distribution of the image data.

  The power supply control circuit 80 includes a battery detection circuit, a DC-DC converter, a switch circuit that switches blocks to be energized, and the like. The power supply control circuit 80 detects the presence / absence of a battery, the type of battery, and the remaining battery level, controls the DC-DC converter based on the detection result and the instruction of the system control unit 50, and requires the necessary voltage. It supplies to each part including the recording medium 200 for a period. The power source 86 includes a primary battery (alkaline battery, lithium battery, etc.), a secondary battery (NiCd battery, NiMH battery, Li-ion battery, etc.), an AC adapter, etc., and a power control circuit 80 via connectors 84, 82. Connected to.

  The interface unit 90 manages an interface with the recording medium 200. The optical viewfinder 104 is configured to be able to take an image using only the optical viewfinder 104 without using the electronic viewfinder function of the image display unit 28. In the optical viewfinder 104, some functions (focus display, camera shake warning display, flash charge display, shutter speed display, aperture value display, exposure correction display, etc.) of the display unit 54 are provided.

  The recording medium 200 includes a memory card or a hard disk, and includes a recording unit 202 including a semiconductor memory or a magnetic disk, an interface unit 204 that manages an interface with the imaging apparatus 100, and a connector 206. The recording medium 200 is connected to the interface unit 90 via connectors 206 and 92. In the present embodiment, the recording medium 200 is built in the imaging device 100.

  Next, the operation of the imaging apparatus according to the present embodiment having the above configuration will be described with reference to FIGS.

  FIG. 2 is a flowchart showing the overall operation of the imaging apparatus.

  In FIG. 2, when the photographer operates the power switch 60 of the imaging apparatus to turn on the power, the system control unit 50 of the imaging apparatus initializes a flag and a control variable (step S201). Next, the system control unit 50 starts management processing relating to the file recorded on the recording medium 200 (step S201). Next, the system control unit 50 determines whether the mode set by the photographer using the mode changeover switch 72 is the still image recording mode, the moving image recording mode, or the playback mode (step S203, step S205, Step S207).

  When the mode switch 72 is set to the still image recording mode, the system control unit 50 executes still image recording mode processing (step S204). Details of the still image recording mode process will be described later with reference to FIG. If the mode switch 72 is set to the moving image recording mode, the system control unit 50 executes the moving image recording mode process (step S206). If the mode switch 72 is set to the playback mode, the system control unit 50 executes the playback mode process (step S208).

  When the mode changeover switch 72 is set to another mode other than the above mode, the system control unit 50 executes processing according to the set mode (step S209).

  The system control unit 50 performs processing corresponding to the mode set by the mode changeover switch 72 (any of step S204, step S206, step S208, and step S209), and then determines the setting position of the power switch 60 ( Step S210). If the power switch 60 is set to ON, the process returns to step S203. On the other hand, when the power switch 60 is set to OFF, the system control unit 50 performs an end process and shifts the power of the imaging apparatus to the OFF state (step S211).

  FIG. 3 is a flowchart showing details of the still image recording mode process (step S204) of FIG. Note that the still image recording mode process is terminated by an interrupt process or the like when the photographer switches the still image recording mode to another mode by the mode changeover switch 72 or when the power switch 60 is turned OFF. .

  In FIG. 3, the system control unit 50 of the imaging apparatus determines the shooting mode when the still image recording mode process is started (step S <b> 301). When the operation unit 70 is operated and there is an input for setting the shooting mode, the shooting mode is determined according to the setting, and when there is no input, the shooting mode at the end of the previous still image recording mode process is determined. Determine.

  Next, when the shooting mode is determined in step S301 described above, the system control unit 50 performs a through display in which an image corresponding to the image data output from the imaging unit is displayed on the image display unit 28 (step S302). Next, the system control unit 50 confirms the remaining capacity of the power source 86 (battery) using the power source control unit 80, confirms the presence / absence of the recording medium 200 and the remaining capacity via the interface unit 90, and the imaging apparatus 100. It is determined whether or not there is a problem with the operation (step S303).

  If there is a problem with the operation of the imaging apparatus 100, the system control unit 50 performs a predetermined warning display with an image or sound using the image display unit 28 (step S304), and returns the process to step S301. If there is no problem in the operation of the imaging apparatus 100, the system control unit 50 updates settings related to the focus as necessary (step S305). Here, whether or not “face priority” for setting the AF area according to the face position detected from the image data from the menu screen displayed on the image display unit 28 by pressing the menu button of the operation unit 70 is applied. The photographer can arbitrarily set it.

  Next, the system control unit 50 determines whether or not the AF frame setting is “face priority” (step S306). If the AF frame setting is not “face priority”, the process proceeds directly to step S308. When the AF frame setting is “face priority”, the system control unit 50 displays the through image based on the face detection result of the face detection circuit in the image processing circuit 20 notified from the image processing circuit 20. Update processing of the face frame to be superimposed on is performed (step S307). Thereafter, the process proceeds to step S308.

  Next, the system control unit 50 determines whether or not the first shutter switch signal SW1 of the first shutter switches SW1 and 62 is ON (step S308). If the first shutter switch signal SW1 is OFF, the process returns to step S305, and steps S305 and S306 are repeated. On the other hand, if the first shutter switch signal SW1 is ON, the process proceeds to step S309.

  Next, the system control unit 50 determines exposure conditions including an aperture value, a shutter time (shutter speed), and sensitivity by performing a photometric process for measuring the luminance of the photographing target (subject) (step S309). Details of the photometric processing will be described later with reference to FIG. In the photometric process, the flash 48 is set if necessary. The system control unit 50 calculates an overall luminance correction value, a face correction value, and a final exposure correction value based on the photometric result obtained by performing the photometric processing. Details will be described later. Next, the system control unit 50 adjusts the focus of the photographing lens 10 to the subject by performing a distance measurement process (step S310).

  Next, the system control unit 50 determines ON / OFF states of the first shutter switch SW1 signal 2 and the second shutter switch SW2 signal (steps S311 and S312). If the second shutter switch signal SW2 is turned on while the first shutter switch signal SW1 is turned on, the process proceeds to step S313.

  When the first shutter switch signal SW1 is turned off (when the second shutter switch signal SW2 is not turned on (OFF) and the first shutter switch signal SW1 is also released (OFF)), the process returns to step S305. Further, while the first shutter switch signal SW1 is ON and the second shutter switch signal SW2 is OFF, the processes of Step S311 and Step S312 are repeated.

  When the second shutter switch SW2, 64 is pressed by the photographer, the system control unit 50 sets the display state of the image display unit 28 from the through display state to the fixed color display state (step S313). Next, the system control unit 50 executes photographing processing (including exposure processing and development processing) (step S314).

  In the exposure process, captured image data is stored in the memory 30 via the A / D converter 16, the image processing circuit 20, the memory control circuit 22, or directly from the A / D converter 16 via the memory control circuit 22. Write to. In the development process, the system control unit 50 reads the image data written in the memory 30 as necessary and performs various processes. Details of the photographing process will be described later with reference to FIG.

  Next, the system control unit 50 performs a REC review display of the captured image corresponding to the image data obtained by the imaging process on the image display unit 28 (step S315). The REC review is a process for displaying a photographed image on the image display unit 28 for a predetermined time (review time) before recording image data on the recording medium 200 after photographing a subject for confirmation of the photographed image. It is. After performing the REC review display, the system control unit 50 executes a recording process in which the image data obtained by the imaging process is written to the recording medium 200 as an image file (step S316).

  Next, the system control unit 50 determines the ON / OFF state of the second shutter switch signal SW2 (step S317). If the second shutter switch signal SW2 is ON, the determination in step S317 is repeated, and the process waits for the second shutter switch signal SW2 to be OFF. During this time, the REC review display is continued.

  That is, when the recording process in step S316 is completed, the REC review display on the image display unit 28 is continued until the second shutter switch signal SW2 is turned OFF. With this configuration, the photographer can carefully check the captured image using the REC review by continuing to fully press the shutter button (not shown).

  After the photographer has taken a picture with the shutter button fully depressed, the process proceeds from step S317 to step S318 when the full push state is released by releasing the shutter button. The system control unit 50 determines whether or not a predetermined review time has elapsed (step S318). If the review time has elapsed, the process proceeds to step S319.

  Next, the system control unit 50 returns the display state of the image display unit 28 from the rec review display to the through display state (step S319). Through this process, after the photographer confirms the photographed image by the REC review display, the display state of the image display unit 28 is a through display that sequentially displays images corresponding to the image data output from the imaging unit for the next photographing. It will automatically switch to the state.

  Next, the system control unit 50 determines the ON / OFF state of the first shutter switch signal SW1 (step S320). If the first shutter switch signal SW1 is ON, the process returns to step S311. If the first shutter switch signal SW1 is OFF, the process returns to step S305.

  That is, if the shutter button is half-pressed (the first shutter switch signal SW1 is ON), the system control unit 50 prepares for the next shooting (step S311). On the other hand, when the shutter button is released (the first shutter switch signal SW1 is OFF), the system control unit 50 finishes a series of shooting operations and returns to the shooting standby state (step S305).

  4a and 4b are flowcharts showing details of the photometric process (step S309) in FIG.

  4A and 4B, the system control unit 50 of the imaging apparatus performs the following calculation based on image data obtained by imaging the subject read from the imaging element 14. On the exposure surface of the image sensor 14, a photometric area (photometric means) occupying 90% of the size of the exposure surface is set with the same central portion, and an image data area corresponding to the photometric area is set. Luminance is required. This photometric area only needs to be set to a size that requires the brightness of the entire exposure surface, and is generally set to occupy a size of about 70 to 100% of the exposure surface.

  The average brightness Y (h, v) (h = 0,1, ..., HMAX-1 v = 0,1 in each of the HMAX × VMAX areas obtained by dividing this photometric area (entire area) into horizontal HMAX and vertical VMAX ,..., VMAX-1) are calculated (step S401). Hereinafter, the average luminance Y (h, v) for each region is referred to as block luminance. HMAX and VMAX are design parameters. For example, HMAX = 8 and VMAX = 8. That is, a photometric area composed of a plurality of blocks of HMAX × VMAX is set in the image data.

  Next, the system control unit 50 performs the following calculation using the block luminance Y (h, v) obtained in step S401. That is, the backlight correction value DeltaBvC is calculated (step S402). Also, an empty correction value DeltaBvS is calculated (step S403). Also, the brightness correction value BvL is calculated (step S404). Details of the backlight correction value DeltaBvC calculation process will be described later with reference to FIGS. 6A and 6B, and details of the sky correction value DeltaBvS calculation process will be described later with reference to FIGS. 7A and 7B.

  In this case, the system control unit 50 sets the brightness correction value BvL according to the brightness of the subject for the brightness correction value BvL (step S404). The backlight correction value is a luminance correction value for suppressing the influence of backlight when it is assumed that the subject is photographed with backlight. The sky correction value is a luminance correction value for suppressing the influence of the sky when it is assumed that an object with the sky as a background is captured.

  Next, the system control unit 50 performs the following calculation based on the backlight correction value DeltaBvC, the sky correction value DeltaBvS, and the luminance correction value BvL. That is, the overall brightness correction value DeltaBvAll, which is a brightness correction value when assuming that the brightness of the entire photometric area of the image sensor 14 is an appropriate value, is calculated (step S405). Details of the overall brightness correction value (total exposure correction value) DeltaBvAll calculation process will be described later with reference to FIG.

  Next, the system control unit 50 refers to the face detection result (face detection information) of the face detection circuit in the image processing circuit 20 notified from the image processing circuit 20, and detects the face from the image data obtained by imaging the subject. Is detected (step S406). If no face is detected from the image data obtained by imaging the subject, the system control unit 50 sets the overall brightness correction value DeltaBvAll as the final exposure correction value LastHoseiDeltaBv (step S407), and ends the photometric process.

  On the other hand, when a face is detected from the image data obtained by imaging the subject, the system control unit 50 uses the block luminance Y (h, v) and the face detection information notified from the image processing circuit 20, A face correction value DeltaBvFace is calculated (step S408). Details of the face correction value (main subject exposure correction value) DeltaBvFace calculation process will be described later with reference to FIG.

  When a face is detected, the final exposure correction value LastHoseiDeltaBv is calculated so that the face correction value DeltaBvFace falls within a predetermined range after exposure control. The predetermined range is determined based on a gain-up amount when gain-up is performed on a low-luminance portion of image data. If a face is detected, the final exposure correction value LastHoseiDeltaBv is calculated based on the size of the main subject area (face area) of the image data.

  Next, the system control unit 50 obtains a difference Delta1 obtained by subtracting the overall brightness correction value DeltaBvAll from the face correction value DeltaBvFace (step S409). When the difference Delta1 is smaller than the threshold MIN_DELTA (YES in step S410), the system control unit 50 sets the threshold MIN_DELTA to Delta1 (step S411). If the difference Delta1 is greater than the threshold MAX_DELTA (YES in step S412), the system control unit 50 sets the threshold MAX_DELTA to Delta1 (step S413). Note that MIN_DELTA and MAX_DELTA are design parameters and satisfy MIN_DELTA <MAX_DELTA.

  Next, the system control unit 50 obtains the mixing ratio MixRatio1 according to the size of the face detected from the image data obtained by imaging the subject (step S414). In this case, 0 ≦ MixRatio1 ≦ 1 is set so that the mixing ratio MixRatio1 increases as the face detected from the image data of the subject increases. Next, the system control unit 50 updates the face correction value DeltaBvFace using the obtained difference Delta1, mixing ratio MixRatio1, and overall brightness correction value DeltaBvAll (step S415).

  The face correction value DeltaBvFace is adjusted to fall within the range of “DeltaBvAll + MIN_DELTA” to “DeltaBvAll + MAX_DELTA” by the processing in steps S409 to S415 described above. Along with this, the face correction value is updated so that the larger the face detected from the image data of the subject, the greater the influence of the face.

  Next, the system control unit 50 determines whether or not the overall luminance correction value DeltaBvAll is larger than the face correction value DeltaBvFace updated in step S415 (step S416). If the overall brightness correction value DeltaBvAll is not larger than the face correction value DeltaBvFace, the system control unit 50 sets the face correction value DeltaBvFace as the final exposure correction value LastHoseiDeltaBv (step S420). Thereby, the photometry process is completed.

  Each DeltaBv above indicates how much the actual brightness deviates from the target value. When the actual brightness is greater than the target value, the value becomes larger (positive), and the actual brightness is less than the target value. Small (negative) value when small. The face correction value DeltaBvFace represents the difference between the actual brightness and the target value with respect to the brightness of the face area. The overall brightness correction value DeltaBvAll represents the deviation between the actual brightness and the target value for the overall brightness of the photometric area. Final exposure control is performed such that the current exposure is shifted by the final exposure correction value LastHoseiDeltaBv.

  When the process proceeds to step S420 via step S416 (when the face correction value DeltaBvFace is larger than the overall luminance correction value DeltaBvAll), exposure control is performed in accordance with the face target value. Details will be described later. The face area approaches the target value, and the background (entire photometric area) is darker than the target. This is because priority is given to the face area as the main subject area, which preferentially prevents the face from becoming brighter than the target. This is shown in FIGS. 10 (a) and 10 (b).

  10A, 10B, 10C, and 10D show the exposure based on the current relationship between the face correction value DeltaBvFace and the overall luminance correction value DeltaBvAll, and the final exposure correction value LastHoseiDeltaBv. The relationship after control is shown.

  In FIGS. 10A and 10B, the vertical axis represents DeltaBv, and ◯ is the face correction value DeltaBvFace, and Δ is the overall luminance correction value DeltaBvAll. FIGS. 10A and 10B both show the case of DeltaBvAll <DeltaBvFace, and the face correction value DeltabvFace becomes 0 after the exposure control (LastHoseiDeltaBv = DeltaBvFace). That is, it shows how exposure control is performed in accordance with the brightness of the face area.

  If the overall brightness correction value DeltaBvAll is greater than the face correction value DeltaBvFace (YES in step S416), the system control unit 50 makes the following determination. That is, it is determined whether or not the difference obtained by subtracting the overall brightness correction value DeltaBvAll from the face correction value DeltaBvFace is larger than the threshold value MIN_DELTABV_FACE (step S417).

  When the difference obtained by subtracting the overall brightness correction value DeltaBvAll from the face correction value DeltaBvFace is larger than the threshold value MIN_DELTABV_FACE, the system control unit 50 performs the following processing. That is, the overall brightness correction value DeltaBvAll is set as the final exposure correction value LastHoseiDeltaBv (step S418). Thereby, the photometry process is completed. However, MIN_DELTABV_FACE <0.

  In this case, even if the exposure is adjusted to the entire photometric area based on the overall brightness correction value DeltaBvAll, the difference from the target brightness value of the face area can be suppressed within the threshold MIN_DELTABV_FACE. Therefore, the final exposure is controlled so as to match the target value of the entire photometric area luminance. This state is shown in FIG.

  FIG. 10C shows DeltaBvFace-DeltaBvAll> MIN_DELTABV_FACE, and the overall brightness correction value DeltaBvAll becomes 0 after the exposure control (LastHoseiDeltaBv = DeltaBvAll). That is, the exposure control is performed in accordance with the brightness of the entire photometric area. It can be seen that the brightness of the face area does not become smaller than the threshold MIN_DELTABV_FACE even if the exposure is adjusted to the brightness of the entire photometric area.

  If the difference obtained by subtracting the overall brightness correction value DeltaBvAll from the face correction value DeltaBvFace is not larger than the threshold value MIN_DELTABV_FACE (NO in step S417), the system control unit 50 performs the following process. That is, DeltaBvFace-MIN_DELTABV_FACE is set as the final exposure correction value LastHoseiDeltaBv (step S419). Thereby, the photometry process is completed.

  In this case, if the exposure is matched to the entire photometric area based on the overall brightness correction value DeltaBvAll, the brightness of the face area becomes smaller than the threshold value MIN_DELTABV_FACE. Therefore, the final exposure correction value LastHoseiDeltaBv is determined so that the difference from the target brightness value of the face area is MIN_DELTABV_FACE. This state is shown in FIG.

  In FIG. 10D, DeltaBvFace-DeltaBvAll <MIN_DELTABV_FACE. The brightness of the background (entire photometry area) is higher than the target value after exposure control, but the brightness of the face area is the threshold MIN_DELTABV_FACE, and the difference from the target brightness value of the face area is within a certain range. I understand.

  Note that the threshold value MIN_DELTABV_FACE may be determined according to the gain increase amount of the dark portion correction processing performed in the image processing described later (step S507 in FIG. 5). The dark part correction process is a process for gaining up a dark part (low luminance part) of the image data, and can brighten the face when the face region is dark.

  Therefore, at the time of the photometric process (step S309 in FIG. 3 (FIGS. 4a and 4b)), it is possible to set the threshold MIN_DELTABV_FACE to be smaller without causing any problem even if the face region is darker than the target by the gain increase in the dark part correction process. . By setting the threshold value MIN_DELTABV_FACE small, it is possible to bring the entire photometric area luminance closer to the target even when the total luminance correction value DeltaBvAll is large.

  FIG. 5 is a flowchart showing details of the photographing process (step S314) of FIG.

  In FIG. 5, the system control unit 50 of the imaging device acquires the shooting start date and time from a system timer (not shown) when shooting of the imaging device is started, and stores it in the system memory 52 (step S501). Next, the system control unit 50 obtains the exposure amount Ev when the image data used for the photometric processing is captured from the aperture value and the exposure time when the image data used for the photometric processing (step S309) is captured. . Then, this exposure amount Ev is corrected to compensate for the final exposure correction value LastHoseiDeltaBv obtained in the photometric process (step S309), and the final exposure amount LastEv is obtained.

  The system control unit 50 opens the shutter 12 having the aperture function according to the aperture value according to the photometric data (final exposure amount LastEv) obtained in the photometric processing (step S309) (step S502). Thus, exposure is started (step S503).

  Next, the system control unit 50 waits for the end of exposure of the image sensor 14 according to the photometric data (final exposure amount LastEv) obtained in the photometric process (step S309) (step S504). When the exposure end time is reached, the system control unit 50 closes the shutter 12 (step S505). Next, the system control unit 50 reads image data (charge signal) from the image sensor 14, and passes through the A / D converter 16, the image processing circuit 20, the memory control circuit 22, or from the A / D converter 16. The data is directly written into the memory 30 via the memory control circuit 22 (step S506). Steps S501 to S506 described above correspond to the exposure process.

  Next, the system control unit 50 reads out the image data written in the memory 30 as necessary, and sequentially performs image processing by the image processing circuit 20 (step S507). This image processing includes, for example, white balance processing, compression processing using the compression / expansion circuit 32, and the like. A dark part correction process for gaining up a dark part of the image data is also performed in step S507. The system control unit 50 writes the image data subjected to image processing in the memory 30.

  Next, the system control unit 50 reads the image data from the memory 30, expands the image data using the compression / expansion circuit 32, and resizes the image data for display on the image display unit 28. Then, the system control unit 50 transfers the resized image data to the D / A converter 26 so as to be displayed on the image display unit 28 (step S508). When the series of processes is completed, the shooting process is terminated.

  6a and 6b are flowcharts showing details of the backlight correction value DeltaBvC calculation process of FIG. 4a.

  6A and 6B, the system control unit 50 of the imaging apparatus refers to the face detection result of the face detection circuit in the image processing circuit 20 notified from the image processing circuit 20, and image data obtained by imaging the subject. Whether or not a face is detected is determined (step S601). When the face is detected from the image data obtained by imaging the subject, the system control unit 50 corresponds to the detected face area in the block luminance Y (h, v) obtained in step S401 in FIG. 4a. The average luminance value YLFace of the area to be calculated is obtained (step S602).

  Next, the system control unit 50 sets the threshold MaxYL to YLFace * MAX_YLLIMIT, sets the threshold MinYL to YLFace / MIN_YLLIMIT (step S603), and proceeds to step S622. MAX_YLLIMIT and MIN_YLLMIT are design parameters. For example, MAX_YLLIMIT = MIN_YLLIMIT = 2.

  On the other hand, if no face is detected from the image data obtained by imaging the subject, the system control unit 50 averages the luminance of the region A out of the block luminance Y (h, v) obtained in step S401 of FIG. 4a. A value YLA is obtained (step S604). The area A is an area near the center of the photometric area (the central area of the image data). When HMAX = VMAX = 8, for example, a block of 2 × 2 in the center may be used as shown in FIG. As shown in FIG. 11A, the region B may be set so as to surround the region A, the region C may be set so as to surround the region B, and the region D may be set so as to surround the region C.

  Next, the system control unit 50 sets the threshold MaxYL to YLA * MAX_YLLIMIT, sets the threshold MinYL to YLA / MIN_YLLIMIT (step S605), and proceeds to step S622.

  The system control unit 50 sets the gains B_Gain, C_Gain, and D_Gain for the regions B, C, and D to BGAIN, CGAIN, and DGAIN, respectively (step S622), and proceeds to step S606. Here, BGAIN, CGAIN, and DGAIN are design parameters. For example, BGAIN = 0.75, CGAIN = 0.67, and DGAIN = 0.5. A smaller gain is set in a region closer to the periphery of the image data.

  After the process of step S622, the system control unit 50 first initializes variables h and v to 0 in order to obtain the photometric weight of each block of HMAX × VMAX (step S606). Next, the system control unit 50 determines whether or not the variable v is smaller than VMAX (step S607). If the variable v is smaller than VMAX, the process proceeds to step S608; otherwise, the process proceeds to step S621.

  The system control unit 50 determines whether the variable h is smaller than HMAX (step S608). If the variable h is smaller than HMAX, the process proceeds to step S609; otherwise, the process proceeds to step S620. The system control unit 50 determines whether or not the block luminance Y (h, v) is larger than the threshold value MaxYL set in step S603 or step S605 (step S609). If the block luminance Y (h, v) is larger than the threshold MaxYL, the process proceeds to step S612, and if not, the process proceeds to step S610.

  Similarly, the system control unit 50 determines whether or not the block luminance Y (h, v) is smaller than the threshold MinYL set in step S603 or step S605 (step S610). If the block luminance Y (h, v) is smaller than the threshold value MinYL, the process proceeds to step S612. Otherwise, the process proceeds to step S611.

  When the block luminance Y (h, v) is not smaller than the threshold value MinYL, the system control unit 50 uses a predetermined default photometric weight as the backlight correction photometric weight Wc (h, v) of the block (h, v). W (h, v) is set (step S611). The default photometric weight W (h, v) assigned to each block (h, v) is set to a larger value as it is closer to the center of the photometric area, as shown in FIG. Yes.

  If the block luminance Y (h, v) is larger than the threshold MaxYL in step S609 or if the block luminance Y (h, v) is smaller than the threshold MinYL in step S610, the system control unit 50 makes the following determination. That is, it is determined whether or not the block luminance Y (h, v) belongs to the region B (step S612).

  When the block luminance Y (h, v) belongs to the region B, the system control unit 50 performs the following process. That is, a predetermined photometric weight W (h, v) of the block luminance Y (h, v) is multiplied by the gain B_Gain for the region B, and this is multiplied by the photometric weight Wc for backlight correction of the block luminance Y (h, v). (H, v) is set (step S613).

  If the block luminance Y (h, v) does not belong to the region B, the system control unit 50 determines whether or not the block luminance Y (h, v) belongs to the region C (step S614). When the block luminance Y (h, v) belongs to the region C, the system control unit 50 performs the following process. That is, a predetermined photometric weight W (h, v) of the block luminance Y (h, v) is multiplied by the gain C_Gain for the region C, and this is multiplied by the photometric weight Wc for backlight correction of the block luminance Y (h, v). (H, v) is set (step S615).

  When the block luminance Y (h, v) does not belong to the region C (step S614), the system control unit 50 determines whether or not the block luminance Y (h, v) belongs to the region D (step S616). ). When the block luminance Y (h, v) belongs to the region D, the system control unit 50 performs the following process. That is, a predetermined photometric weight W (h, v) of the block luminance Y (h, v) is multiplied by the gain D_Gain for the region D, and this is multiplied by the photometric weight Wc for backlight correction of the block luminance Y (h, v). (H, v) is set (step S617).

  Here, B_Gain, C_Gain, and D_Gain are set to satisfy the relationship of 0 <D_Gain <C_Gain <B_Gain <1. That is, when the block luminance Y (h, v) is larger than the threshold value MaxYL or smaller than the threshold value MinYL, the light metering weight Wc (h, v) for backlight compensation is the default metering as the block is farther from the area A. It is set to a smaller value than the weight W (h, v).

  When the block luminance Y (h, v) does not belong to the area D (belongs to the area A), the system control unit 50 performs the following settings. That is, a predetermined default photometric weight W (h, v) is set as the backlight correction photometric weight Wc (h, v) for the block luminance Y (h, v) (step S618).

  The system control unit 50 obtains the backlight correction photometric weight Wc (h, v) of the block luminance Y (h, v) in step S613, step S615, step S617, or step S618, and then increments the variable h (step S619). Thereafter, the process returns to step S608 to calculate the weight of the next block.

  If the variable h is not smaller than HMAX in step S608, the system control unit 50 increments the variable v (step S620), and returns to step S607 to calculate the weight of the next block.

  If the variable v is not smaller than VMAX in step S607, the system control unit 50 calculates the backlight correction value DeltaBvC from the block luminance Y (h, v) and the backlight correction weight Wc (h, v) based on the following equation. Calculate (step S621). Thereby, the backlight correction value DeltaBvC calculation process (step S402) is terminated.

  Here, Yref is a luminance target (luminance target value), and DeltaBvC represents how many degrees the weighted luminance average using the backlight correction weight deviates from the luminance target. In the present embodiment, the weighting average metering is performed by reducing the metering weight of a block (a region having a large luminance difference) that is greatly different from the brightness of the face region or the region A (region near the center of the metering region: center region). To calculate a backlight correction value. As a result, the influence of a bright background can be suppressed even under backlight conditions, and photometry can be performed with emphasis on the main subject area such as the face area or area A.

  7a and 7b are flowcharts showing details of the empty correction value DeltaBvS calculation process (step S403) in FIG. 4a.

  7A and 7B, the system control unit 50 of the imaging apparatus first determines the upward direction (sky direction) of the imaging apparatus. That is, since the system control unit 50 determines the upward direction (sky direction) of the imaging apparatus, is the vertical position detection sensor 75 that detects whether the attitude of the imaging apparatus is the vertical position or the horizontal position being operated? It is confirmed whether or not (step S701).

  As an example of the vertical position detection sensor 75, an iron ball is arranged in a space surrounded by a plurality of piezoelectric elements, and a piezoelectric element that outputs an electrical signal is detected by the weight of the iron ball, thereby detecting the position of the imaging device. A configuration that determines the upward direction is conceivable. Here, the situation where the vertical position detection sensor 75 is not operating refers to, for example, which piezoelectric element is a result of the imaging device being tilted in an unexpected direction (for example, the optical axis of the lens is directed upward). Also refers to the situation where the iron ball is not in contact. Alternatively, the iron ball rolls to a position over a plurality of piezoelectric elements, and the orientation of the imaging device is slightly tilted, and the piezoelectric element to which the weight of the iron ball is applied is switched, and the upward detection result is not stable. .

  When the vertical position detection sensor 75 is operating, the system control unit 50 determines the upward direction of the imaging device according to the output of the vertical position detection sensor 75 (step S702). On the other hand, when the vertical position detection sensor 75 is not operating (or when the imaging device does not have the vertical position detection sensor 75), the system control unit 50 determines the block luminance Y (h, v) obtained in step S401 of FIG. 4a. The upward direction of the imaging device is determined from the distribution of the image (step S703). That is, for example, the direction with more high-luminance blocks may be determined as the upward direction.

  The system control unit 50 shifts the default metering weight W (h, v) shown in FIG. 12A to the lower block luminance (h, v) and assigns it to the default sky-correcting metering. The weight Wa (h, v) is set (step S704). The downward direction is a direction opposite to the upward direction of the imaging apparatus determined in step S702 or step S703. When HMAX = VMAX = 8, the default photometric weight W (h, v) is as shown in FIG. 12A, and the default sky correction photometric weight Wa (h, v) is as shown in FIG. 12B. . When W (h, v) is shifted downward by one line in FIG. 12A, Wa (h, v) in FIG. 12B is obtained.

  By shifting W (h, v) downward by one line, the default sky correction photometric weight Wa (h, v) of the block luminance (h, v) located in the uppermost line is Wa. (H, v) = 0 is set. In other words, the second weight expressed by the sky correction photometric weight Wa (h, v) is smaller in the sky region than the first weight expressed by the photometric weight W (h, v). Is set as follows.

  Next, the system control unit 50 refers to the face detection result of the face detection circuit in the image processing circuit 20 notified from the image processing circuit 20, and whether the face is detected from the image data obtained by imaging the subject. It is determined whether or not (step S705). When the face is detected from the image data obtained by imaging the subject, the system control unit 50 corresponds to the detected face area in the block luminance Y (h, v) obtained in step S401 in FIG. 4a. The average luminance value YLFace of the area to be calculated is obtained (step S706).

  Next, the system control unit 50 sets the threshold value MaxYL used in clip processing to YLFace * MAX_YLLIMIT, and sets the threshold value MinYL to YLFace / MIN_YLLIMIT (step S707). Here, MAX_YLLIMIT and MIN_YLLIMIT are design parameters. For example, MAX_YLLIMIT = MIN_YLLIMIT = 2.

  Next, the system control unit 50 sets the gains for the regions Bs, Cs, and Ds to BSGAIN_FACE, CSGAIN_FACE, and DSGAIN_FACE, respectively (step S708), and proceeds to step S712. Here, BSGAIN_FACE, CSGAIN_FACE, and DSGAIN_FACE are design parameters. For example, BSGAIN_FACE = 0.75, CSGAIN_FACE = 0.67, and DSGAIN_FACE = 0.5.

  In addition, the region Bs, the region Cs, and the region Ds are obtained by shifting the regions B, C, and D used in the backlight correction value DeltaBvC calculation process in step S402 of FIG. 4A downward. When HMAX = VMAX = 8, for example, as shown in FIG. In this example, the line is shifted downward by one line.

  If no face is detected from the image data obtained by imaging the subject (NO in step S705), the system control unit 50 determines the area of the block luminance Y (h, v) obtained in step S401 of FIG. 4a. A luminance average value YLA of A is obtained (step S709). Next, the system control unit 50 sets the threshold value MaxYL to YLA * MAX_YLLIMIT, and sets the threshold value MinYL to YLA / MIN_YLLIMIT (step S710).

  Next, the system control unit 50 sets the gains for the regions Bs, Cs, and Ds to BSGAIN, CSGAIN, and DSGAIN, respectively (step S711), and proceeds to step S712. Here, BSGAIN, CSGAIN, and DSGAIN are design parameters. For example, BSGAIN = 1.0, CSGAIN = 1.0, and DSGAIN = 0.75.

  After the processing in step S708 or step S711, the system control unit 50 first initializes the variables h and v to 0 in order to obtain the photometric weight of each block of HMAX × VMAX (step S712). Next, the system control unit 50 determines whether or not the variable v is smaller than VMAX (step S713). If the variable v is smaller than VMAX, the process proceeds to step S714. Otherwise, the process proceeds to step S725.

  The system control unit 50 determines whether or not the variable h is smaller than HMAX (step S714). If the variable h is smaller than HMAX, the process proceeds to step S715. Otherwise, the process proceeds to step S724. The system control unit 50 determines whether or not the block luminance Y (h, v) is larger than the threshold value MaxYL set in step S707 or step S710 (step S715). If the block luminance Y (h, v) is larger than the threshold value MaxYL, the process proceeds to step S717, and if not, the process proceeds to step S716.

  Similarly, the system control unit 50 determines whether or not the block luminance Y (h, v) is smaller than the threshold MinYL set in step S707 or step S710 (step S716). If the block luminance Y (h, v) is smaller than the threshold MinYL, the process proceeds to step S717, and if not, the process proceeds to step S726. When the block luminance Y (h, v) is not smaller than the threshold value MinYL, the system control unit 50 uses the default photometric weight Wa (h, h, v) as the sky correction photometric weight Ws (h, v) of the block (h, v). v) is set (step S726).

  When the block luminance Y (h, v) is larger than the threshold MaxYL (YES in step S715), or when the block luminance Y (h, v) is smaller than the threshold MinYL (YES in step S716), the system control unit 50 Make a decision. That is, it is determined whether or not the block luminance Y (h, v) belongs to the region Bs (step S717).

  When the block luminance Y (h, v) belongs to the region Bs, the system control unit 50 uses the sky correction photometric weight Wa (h, v) of the block luminance Y (h, v) set in step S704 for the region Bs. Is multiplied by the gain Bs_Gain (step S718). This is the photometric weight Ws (h, v) for sky correction of the block luminance Y (h, v).

  If the block luminance Y (h, v) does not belong to the region Bs, the system control unit 50 determines whether or not the block luminance Y (h, v) belongs to the region Cs (step S719). When the block luminance Y (h, v) belongs to the area Cs, the system control unit 50 uses the area Cs for the sky correction photometric weight Wa (h, v) of the block luminance Y (h, v) set in step S704. Is multiplied by the gain Cs_Gain (step S720). This is the photometric weight Ws (h, v) for sky correction of the block luminance Y (h, v).

  When the block luminance Y (h, v) does not belong to the region Cs, the system control unit 50 determines whether or not the block luminance Y (h, v) belongs to the region Ds (step S721). When the block luminance Y (h, v) belongs to the area Ds, the system control unit 50 uses the sky correction photometric weight Wa (h, v) of the block luminance Y (h, v) set in step S704 for the area Ds. Is multiplied by the gain Ds_Gain (step S722). This is the photometric weight Ws (h, v) for sky correction of the block luminance Y (h, v).

  If the block luminance Y (h, v) does not belong to the region Ds, the process proceeds to step S726, and the default photometric weight Wa (h, v) is set as the sky correction photometric weight Ws (h, v) of the block (h, v). v) is set (step S726). After obtaining the sky correction photometric weight Ws (h, v) of the block luminance Y (h, v), the system control unit 50 increments the variable h (step S723) and calculates the weight of the next block. The process returns to step S714.

  If the variable h is not smaller than HMAX (NO in step S714), the system control unit 50 increments the variable v (step S724) and returns to step S713 to calculate the weight of the next block.

  When the variable v is not smaller than VMAX (NO in step S713), the system control unit 50 calculates the sky correction value DeltaBvS based on the following equation from the block luminance Y (h, v) and the sky correction weight Ws (h, v). Is calculated (step S725). Thereby, the sky correction value DeltaBvS calculation process (step S403) is terminated.

  Here, Yref is a luminance target (luminance target value), and DeltaBvS represents how many degrees the weighted luminance average using the sky correction weight deviates from the luminance target. By shifting the weight downward in step S704, it is possible to reduce the influence of the sky when there is a sky above the photometric area. Further, by reducing the photometric weight of the face area or a block whose luminance is significantly different from that of the area A, photometry is performed with emphasis on the main subject area such as the face area and the area A while suppressing the influence of the sky. be able to.

  FIG. 8 is a flowchart showing details of the overall luminance correction value DeltaBvAll calculation process (step S405) in FIG. 4a.

  In FIG. 8, the system control unit 50 of the imaging apparatus calculates the average luminance value Yup in the upper part of the photometric area from the block luminance Y (h, v) obtained in step S401 in FIG. 4A (step S801). Similarly, the system control unit 50 calculates the average luminance value Ydown below the photometric area from the block luminance Y (h, v) (step S802). For the upward direction of the photometric area, the direction determined in step S702 or S703 in FIG. 7A is used. In the case of HMAX = VMAX = 8, for example, the luminance average values of one line at the upper and lower ends may be Yup and Ydown, respectively.

  Next, the system control unit 50 obtains the mixture ratio α1 (0 ≦ α1 ≦ 1) from the value of Yup / Ydown, which is the ratio of the luminance average values of the upper and lower end 1 lines (step S803). It is set so that the mixing ratio α1 decreases as Yup / Ydown increases. Next, the system control unit 50 obtains the mixing ratio α2 (0 ≦ α2 ≦ 1) from the value of Yup (step S804). It is set so that the mixing ratio α2 decreases as Yup increases.

  Next, the system control unit 50 compares the mixing ratio α1 and the mixing ratio α2 (step S805). When the comparison result is α1 <α2, the system control unit 50 sets the mixing ratio α1 as the final mixing ratio α (step S806). If the comparison result is not α1 <α2, the system control unit 50 sets the mixing ratio α2 as the final mixing ratio α (step S807).

  Next, the system control unit 50 obtains the overall brightness correction value DeltaBvAll based on the following equation (step S808). That is, the overall brightness correction value DeltaBvAll is obtained based on the backlight correction value DeltaBvC, the sky correction value DeltaBvS, and the brightness correction value BvL. Thereby, the overall luminance correction value DeltaBvAll calculation process (step S405) is terminated.

  Yup / Ydown or Yup increases as the background sky brightness increases (the ratio of the sky brightness to the brightness of the lower part of the subject increases). The final mixing ratio α is set smaller as Yup / Ydown or Yup increases. For this reason, the effect of the sky correction value DeltaBvS that suppresses the influence of the sky brightness is generated in a situation where the influence of the sky brightness is considered to be large.

  FIG. 9 is a flowchart showing the face correction value DeltaBvFace calculation process (step S408) of FIG. 4a.

  In FIG. 9, the system control unit 50 of the imaging apparatus obtains DeltaBvSLimit based on the following equation (step S901).

  Here, YLS represents an average luminance value of the sky region in the image data obtained by imaging the subject, and YrefSKY represents a preset allowable luminance upper limit value that is an upper limit allowable as the luminance of the sky region. Therefore, DeltaBvSLimit represents the luminance difference from the allowable luminance upper limit value of the sky region. When HMAX = VMAX = 8, the empty area may be set to the upper one line, for example. What is necessary is just to use what was calculated | required by step S702 or step S703 of FIG.

  Next, the system control unit 50 obtains DeltaBvFace0 based on the following equation (step S902).

  Here, YLFace indicates the average luminance value of the face area, and YrefFACE indicates the luminance target of the face area. Therefore, DeltaBvFace0 indicates the luminance difference from the luminance target of the face area.

  Next, the system control unit 50 compares the DeltaBvSLimit obtained in step S901 with the DeltaBvFace0 obtained in step S902 (step S903). When the comparison result is DeltaBvFace0 <DeltaBvSLimit, the system control unit 50 sets the variable Delta2 as a difference obtained by subtracting DeltaBvFace0 from DeltaBvSLimit (step S904). Next, the system control unit 50 determines whether Delta2> MAX_DELTA is satisfied (step S905).

  When the comparison result is Delta2> MAX_DELTA, the system control unit 50 substitutes MAX_DELTA for Delta2 (step S906), and proceeds to step S907. If the comparison result is not Delta2> MAX_DELTA, the process proceeds to step S907 as it is. The system control unit 50 sets a mixing ratio MixRatio (0 ≦ MixRatio ≦ 1) according to the size of the face (step S907). Here, the mixing ratio MixRatio is set such that the larger the face, the smaller the MixRatio. Note that MAX_DELTA is a design parameter, for example, MAX_DELTA = 1.

  Next, the system control unit 50 multiplies Delta2 by the mixing ratio MixRatio set in step S907 (step S908). Further, the system control unit 50 adds the DeltaBvFace0 to the result obtained by multiplying the Delta2 by the mixing ratio MixRatio to obtain the face correction value DeltaBvFace (step S909). Thereby, the face correction value DeltaBvFace calculation process (step S408) is terminated.

  When the comparison result in step S903 is DeltaBvFace0 <DeltaBvSLimit, when exposure control is performed to match the face (so that DeltaBvFace0 becomes 0), the brightness of the sky region is as follows. That is, the brightness of the sky region exceeds the allowable brightness upper limit (DeltaBvFace> 0). For this reason, the exposure is not adjusted to the face itself, but is controlled so as to take into account the brightness of the sky region.

  When DeltaBvFace0 <DeltaBvSLimit is not satisfied (NO in step S903), the system control unit 50 sets DeltaBvFace0 as the face correction value DeltaBvFace (step S910). Thereby, the face correction value DeltaBvFace calculation process (step S408) is terminated.

  If the comparison result in step S903 is not DeltaBvFace0 <DeltaBvSLimit, the exposure area is controlled to match the face (so that DeltaBvFace0 becomes 0). In other words, the brightness of the sky region is smaller than the allowable brightness upper limit (DeltaBvSLimit <0). Therefore, it is possible to adjust the exposure to the face area to such an extent that the sky does not fly out (the sky does not appear whitish). That is, the brightness of the sky area of the image data is compared with a preset allowable brightness upper limit value, and the face correction value is corrected based on the comparison result.

  As described above, the face correction value DeltaBvFace is obtained by adding the difference between the brightness of the sky area and the allowable brightness upper limit value of the sky area to the difference between the brightness of the face area and the brightness target of the face area. In this way, it is possible not only to bring the luminance value of the face area closer to the luminance target, but also to suppress the phenomenon of the background sky appearing whitish.

  As described above in detail, according to the present embodiment, the following operations and effects are achieved. If the luminance difference between the main subject area and the background (sky) area is large because the angle of view (shooting target) includes both the main subject and the sky, the luminance difference between the main subject area and the background area is large due to artificial lighting. Unlike the case, control is performed so that both the main subject area and the background area do not deviate significantly from the appropriate luminance. As a result, it becomes possible to shoot a dark subject brightly and to suppress overexposure of the background sky.

[Other Embodiments]
In the above embodiment, the case where the face area detected by the face detection circuit of the image processing circuit 20 is the main subject area has been described as an example, but the present invention is not limited to this. A configuration in which the operation unit 70 includes a configuration (for example, a touch panel) (designation unit) that can designate the main subject region, and the main subject region is detected around the position designated by the photographer using the operation unit 70. It is good. For example, an area estimated to be occupied by the same subject may be determined from brightness, color difference, contrast, or motion information based on the position specified by the photographer and detected as the main subject area. .

  In the above embodiment, it is also possible to determine the main subject region using pattern matching based on the region designated by the photographer and use the determined main subject region. For example, it is possible to follow the movement of the main subject by tracking the moving subject on the main subject specified by the touch panel provided in the operation unit 70.

  When a part of the image data is cut out using the so-called electronic zoom function, the whole cut out area may be regarded as the whole photometric area. In this case, each correction value DeltaBv described above may be obtained using only the block luminance Y (h, v) in the cut-out area.

  The object of the present invention is achieved by executing the following processing. That is, a storage medium that records a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. This is the process of reading the code.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Moreover, the following can be used as a storage medium for supplying the program code. For example, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM or the like. Alternatively, the program code may be downloaded via a network.

  Further, the present invention includes a case where the function of the above-described embodiment is realized by executing the program code read by the computer. In addition, an OS (operating system) running on the computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, the present invention includes a case where the functions of the above-described embodiment are realized by the following processing. That is, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

14 Image sensor 20 Image processing circuit 40 Exposure control circuit 50 System control unit 75 Vertical position detection sensor

Claims (14)

Detecting means for detecting a main subject region from image data obtained by imaging a subject with an imaging element;
Photometric means for detecting the brightness of the main subject area of the image data and the brightness of the sky area located above the image data;
By adding a value corresponding to the difference between the brightness of the sky area and the allowable upper limit of the brightness of the sky area to the difference between the brightness of the main subject area and the brightness target value of the main subject area, an exposure correction value for main subject Calculating means for calculating
An image pickup apparatus comprising: a control unit that controls exposure at the time of image pickup by the image pickup device based on a value corresponding to the exposure correction value for the main subject. The calculation means multiplies the difference between the brightness of the sky area and the allowable brightness upper limit value of the sky area by subtracting the difference between the brightness of the main subject area and the brightness target value of the main subject area and the mixture ratio. ,
The exposure correction value for the main subject is calculated by adding to the difference between the luminance of the main subject region and the target luminance value of the main subject region, and the larger the main subject region, the smaller the mixing ratio. The imaging apparatus according to claim 1, wherein: Detecting means for detecting the posture of the imaging device;
3. The determination unit according to claim 1, further comprising: a determination unit that determines the sky region that is an upper region of the image data based on a result of detecting a posture of the imaging apparatus by the detection unit. Imaging device.   The imaging apparatus according to claim 1, further comprising a determining unit that determines the sky region that is an upper region of the image data based on a luminance distribution of the image data.   The imaging apparatus according to claim 1, wherein the detection unit detects a human face area as the main subject area. A designation means capable of designating a position of the main subject area;
The imaging apparatus according to claim 1, wherein the detection unit detects the main subject region using the position specified by the specification unit. The photometric means detects the luminance of a plurality of areas of the image data,
The calculation means calculates an overall exposure correction value from the brightness of a plurality of regions of the image data, calculates a final exposure correction value based on the main subject exposure correction value and the overall exposure correction value,
The imaging apparatus according to claim 1, wherein the control unit controls exposure when imaging is performed by the imaging element based on the final exposure correction value. It said photometric means divides the realm of the image data into a plurality of blocks, detects the respective block luminance,
The calculation means includes a backlight correction value obtained by first weighting each of the block luminances, and a weight of the sky region that is smaller for each of the block luminances than the first weighting. The imaging apparatus according to claim 7, wherein a sky correction value obtained by weighting 2 is calculated, and the backlight correction value and the sky correction value are mixed to calculate the overall exposure correction value. . The calculation means is configured so that the mixture ratio of the backlight correction value decreases as the luminance of the sky region increases compared to the luminance of the region located below the image data or as the luminance of the sky region increases. 9. The imaging apparatus according to claim 8, wherein the overall exposure correction value is calculated by mixing the backlight correction value and the sky correction value.   Detecting means for detecting a main subject region from image data obtained by imaging a subject with an imaging element;
  Photometric means for detecting the brightness of the main subject area of the image data and the brightness of the sky area located above the image data;
  Control means for controlling exposure when imaging is performed by the imaging device based on the difference between the luminance of the sky region and the allowable luminance upper limit value of the sky region and the luminance of the main subject region. An imaging device that is characterized. In a method for controlling an imaging apparatus including an imaging element,
A detection step of detecting a main subject region from image data obtained by imaging the subject with the imaging element;
A photometric step of detecting the brightness of the main subject area of the image data and the brightness of the sky area located above the image data;
By adding a value corresponding to the difference between the brightness of the sky area and the allowable upper limit of the brightness of the sky area to the difference between the brightness of the main subject area and the brightness target value of the main subject area, an exposure correction value for main subject A calculating step for calculating
Control method for an imaging apparatus, characterized in that it and a control step of controlling exposure time of performing imaging by based on the value in accordance with the exposure correction value for the main subject, the image pickup device. A method for controlling an imaging apparatus including an imaging element,
A detection step of detecting a main subject region from image data obtained by imaging the subject with the imaging element;
A photometric step of detecting the brightness of the main subject area of the image data and the brightness of the sky area located above the image data;
A control step of controlling exposure when imaging is performed by the imaging device based on the difference between the luminance of the sky region and the allowable luminance upper limit value of the sky region and the luminance of the main subject region. A control method for an imaging apparatus.   The program which has a computer-readable program code for making a computer perform the control method of the imaging device of Claim 11. A program having computer-readable program code for causing a computer to execute the method for controlling an imaging apparatus according to claim 12.

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