JP2008085638A - Photographing device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a more practical photographing device and photographing method for detecting a defective image by utilizing a result of division photometry using a solid-state imaging element without using sensors other than the solid-state imaging element. <P>SOLUTION: A CPU performs the following operations. The CPU groups a plurality of blocks divided during division photometry into a plurality of groups that are less than the total number of the blocks (step S11). The CPU uses the luminance integrated value of each block acquired by the division photometry to calculate an average luminance value of each group (step S12). The CPU makes one group as a reference group, subtracts the average luminance value of each group adjacent to the reference group from the average luminance value of the reference group and calculates a luminance difference between groups (step S13). The CPU compares the calculated luminance difference between groups with a prescribed value for comparison (step S14). When it is judged that the luminance difference between groups is larger than the prescribed value, the CPU warns a photographer that image data are defective image (step S15). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and an imaging method for converting an imaging signal obtained by imaging a subject image with a solid-state imaging device into digital image data and recording the digital image data on a recording medium, and in particular, other than an imaging system such as a finger hook. The present invention relates to a photographing apparatus and a photographing method for detecting defective images caused by external factors.

  As a photographing device, a subject image is picked up by a solid-state image pickup device such as a CCD image sensor (hereinafter, referred to as a CCD), and an image pickup signal obtained thereby is converted into digital image data, which is converted into an internal memory or a memory card. Digital cameras and mobile phones with cameras that record on these recording media are in widespread use.

  In recent years, such photographing apparatuses have been miniaturized, and a finger may be caught on the lens surface unexpectedly when photographing. When the shutter operation is performed without noticing this, a defect such as a part of the generated image data darkening occurs, and the capacity of the recording medium is wasted due to the defective image data (Patent Document 1). reference). In order to prevent this, in Patent Document 1, the luminance value of the imaging signal output from the solid-state imaging device is compared with the luminance value output from a photometric sensor provided separately from the solid-state imaging device, and a comparison value is obtained. Is outside the allowable range, image data is not recorded on the recording medium.

A similar technique has been proposed for an imaging apparatus including a strobe device (see Patent Documents 2 and 3). In Patent Document 2, an abnormality detection unit provided in a strobe control unit detects a light emission failure of a strobe, and when an abnormality is detected, image data is not recorded on a recording medium. In Patent Document 3, contrast (brightness difference) is detected for a predetermined reference area in image data, and shielding of strobe light by a lens barrel or the like is detected.
JP 2000-307934 A JP 2005-142828 A JP 2005-277492 A

  The techniques of Patent Documents 1 to 3 detect defective images caused by external factors other than the imaging system, such as shielding of subject light by finger hooks, light emission failure of a strobe device, light shielding of strobe light by a lens barrel or the like. Although technical, they all have drawbacks. In Patent Document 1, it is necessary to use a sensor (photometric sensor) other than the solid-state imaging device, and the photographing apparatus becomes large. In Patent Document 2, since defect detection is not performed based on subject light incident on a solid-state image sensor, a defective image due to strobe light or subject light shielding cannot be detected.

  In Patent Document 3, specifically, it is detected whether or not there is a place where the lightness changes suddenly in the reference region. If the line is symmetric with respect to the line connecting the optical axes, and if it is symmetric, take a procedure such as determining whether the lightness between the lightness abrupt changes is lower than a predetermined value. ing. As described above, the technique disclosed in Patent Document 3 detects defective images using actually acquired image data, but the procedure is complicated and impractical.

  The present invention has been made in view of the above-described problems, and more practically detects defective images using the results of split photometry using a solid-state image sensor without using a sensor other than the solid-state image sensor. An object of the present invention is to provide a typical photographing apparatus and photographing method.

  In order to achieve the above object, an imaging apparatus of the present invention converts an imaging signal obtained by imaging subject light with a solid-state imaging device into digital image data, and records the image data on a recording medium. The image data is divided into a plurality of blocks, and the divided photometry means for integrating the luminance signal for each divided block, and the plurality of blocks divided by the divided photometry means are a plurality of blocks smaller than the total number of blocks. Grouping means for grouping into groups, average brightness value calculating means for calculating an average brightness value for each group using the brightness integrated value of each block calculated by the divided photometry means, and among the plurality of groups One group is set as a reference group, and the average luminance value of this reference group is used to determine the value of each group adjacent to this reference group. An inter-group luminance difference calculating means for calculating an inter-group luminance difference by subtracting the average luminance value; a comparison determining means for comparing the inter-group luminance difference calculated by the inter-group luminance difference calculating means with a predetermined value; and And a warning unit that warns the photographer that the image data is a defective image when the comparison determination unit determines that the luminance difference between groups is larger than a predetermined value.

  The inter-group luminance difference calculating means preferably uses a group located at the center of the image data as a reference group.

  Further, when the average luminance value of the neighboring adjacent group is larger than the average luminance value of the reference group, it is determined that the backlight is determined to be in the backlight state by the backlight determination unit and the backlight determination unit. In order to correct a luminance gradient due to backlight by selecting two or more groups having a large average luminance value from the adjacent groups and dividing the average luminance value of the reference group by the average luminance value of the selected group. A correction coefficient calculating means for calculating a correction coefficient for the reference group, and a luminance gradient is corrected by subtracting a value obtained by multiplying the average luminance value of each adjacent group adjacent to the reference group by the correction coefficient from the average luminance value of the reference group A group-to-group brightness difference calculating unit for calculating a luminance difference between groups, and a group calculated by the group luminance difference calculating unit for backlighting. A backlight comparison comparison means for comparing and determining a luminance difference between a group and a predetermined value, and the warning means determines that the luminance difference between groups is greater than a predetermined value by the backlight comparison determination unit. It is preferable to warn the photographer that the image data is a defective image.

  Further, it is preferable that the divided photometry unit divides the image data into eight equal parts in the vertical and horizontal directions to form 64 blocks.

  Further, it is preferable that the grouping means group the plurality of blocks so that a central portion of the image data is large and a peripheral portion is small.

  Further, the warning means is a display means for displaying the image data, and the group on which the luminance difference between groups is determined to be larger than a predetermined value by the comparison determination means or the backlight comparison determination means is displayed on the screen. It is preferable to give a warning by showing.

  Further, it is preferable that a thinning-out processing unit for performing a thinning-out process of the luminance signal is provided before the multi-division photometry unit.

  In addition, it is preferable to provide a strobe light emitting unit that emits strobe light toward the subject when imaging with the solid-state image sensor.

  The optical system that guides subject light to the solid-state imaging device is preferably configured by a bending optical zoom lens mechanism.

  Furthermore, it is preferable that the optical system that guides subject light to the solid-state imaging device is configured by a zoom lens mechanism using a liquid lens.

  In order to achieve the above object, according to the imaging method of the present invention, an imaging signal obtained by imaging subject light by a solid-state imaging device is converted into digital image data, and the image data is recorded on a recording medium. In the photographing method, the step of dividing the image data into a plurality of blocks, integrating the luminance signal for each of the divided blocks, and the plurality of blocks divided by the divided photometry means, a plurality of blocks less than the total number of blocks A step of grouping into groups; a step of calculating an average luminance value for each of the groups using the luminance integrated value of each block calculated by the divided photometric means; and one group of the plurality of groups as a reference group The average brightness value of each group adjacent to this reference group is subtracted from the average brightness value of this reference group. Calculating the inter-group luminance difference, comparing the inter-group luminance difference calculated by the inter-group luminance difference calculating means with a predetermined value, and determining the inter-group luminance difference by the predetermined value. And a step of warning the photographer that the image data is a defective image when it is determined that the image data is larger.

  The present invention groups a plurality of blocks divided at the time of division metering into a plurality of groups, calculates an average luminance value for each group, and calculates an average luminance value of each group adjacent to the reference group from the average luminance value of the reference group. By subtracting and calculating a luminance difference between groups and comparing this with a predetermined value, a defective image due to finger catching or the like is detected, and a solid-state image sensor is used without using a sensor other than the solid-state image sensor. It is possible to detect a defective image by using the result of the divided photometry used.

  In FIG. 1, a lens barrel 12 that holds an imaging lens 11 and a strobe light emitting unit 13 that emits strobe light toward a subject are provided on the front surface of the digital camera 10. A release button 14 and a mode dial 15 are provided on the top surface of the digital camera 10, and a memory card slot 17 in which a memory card 16 is detachably loaded is provided on the side surface of the digital camera 10. .

  In FIG. 2, a liquid crystal display (LCD) 18 and an operation unit 19 are provided on the back surface of the digital camera 10. The LCD 18 displays captured images, so-called through images, and various menu screens. The operation unit 19 is a power button for turning on / off the power of the digital camera 10, a zoom operation button for changing the zoom lens of the imaging lens 11 to the wide side / tele side, a menu screen on the LCD 18, The menu button is operated when determining the selection contents, and a cross key for moving the cursor in the menu screen.

  In the digital camera 10, a shooting mode for taking a still image, a playback mode for displaying the shot image on the LCD 18, and a setting mode for making various settings can be selected. These modes are switched by rotating the mode dial 15. Further, on / off setting of strobe light emission from the strobe light emitting unit 13 is performed by operating the operation unit 19.

  The release button 14 is a two-stage push switch. After the subject is framed by the through image displayed on the LCD 18, when the release button 14 is lightly pressed (half-pressed), photographing preparation processing such as automatic exposure adjustment (AE) and automatic focus adjustment (AF) is performed. In this state, when the release button 14 is pressed once more (fully pressed), imaging is performed by the CCD 21 (see FIG. 2) with the optimum exposure and focus settings determined in the shooting preparation process. An imaging signal for one screen acquired by this imaging is converted into image data and then recorded on the memory card 16.

  FIG. 3 shows an electrical configuration of the digital camera 10. The light that has passed through the imaging lens 11 is incident on the imaging surface (light receiving surface) of the CCD 21 after the amount of light is adjusted by the diaphragm 20. Photosensors are arranged in a plane on the imaging surface of the CCD 21, and the subject image formed on the imaging surface of the CCD 21 is converted into signal charges of an amount corresponding to the amount of incident light by each photosensor. The signal charge accumulated in each photosensor is sequentially read out as a voltage signal (imaging signal) corresponding to the signal charge based on a pulse given from the CCD driver 22.

  The imaging signal output from the CCD 21 is input to the analog signal processing unit 23. The analog signal processing unit 23 includes a sampling hold circuit, a color separation circuit, a gain adjustment circuit, and the like. After the correlated double sampling (CDS) processing is performed in the analog signal processing unit 23, R, G, B Each color signal is subjected to color separation processing, and the signal level of each color signal is adjusted.

  The signal output from the analog signal processing unit 23 is converted into a digital signal by the A / D converter 24 and then input to the digital signal processing unit 25. The digital signal processing unit 25 includes a color separation circuit, a luminance / color difference (YC) signal generation circuit, a gamma correction circuit, a sharpness correction circuit, a contrast correction circuit, and the like, and performs processing in accordance with instructions from the CPU 26. The image data input to the digital signal processing unit 25 is converted into a luminance signal (Y signal) and a color difference signal (Cr, Cb signal) and subjected to predetermined processing such as gamma correction, and then the bus 27 is connected. Stored in the memory 28.

  The timing generator (TG) 29 provides timing signals to the CCD driver 22, the analog signal processing unit 23, the A / D converter 24, and the digital signal processing unit 25 in accordance with instructions from the CPU 26. The circuit is synchronized.

  The image data stored in the memory 28 is read in accordance with an instruction from the CPU 26 and sent to the display control unit 30. The display control unit 30 converts the image data into a display signal (video signal) and then outputs it to the LCD 18. The image data in the memory 28 is periodically rewritten whenever an image signal for one screen is output from the CCD 21, and a video signal generated from the image data is supplied to the LCD 18, so that the CCD 21 captures the image data. An image is displayed on the LCD 18 in real time (this display is referred to as a through image display). The photographer can confirm the shooting angle of view from the through image displayed on the LCD 18.

  When the release button 14 is fully pressed, capturing of image data for recording is started. When a mode for compressing and recording image data is selected, the compression / decompression processing unit 31 compresses image data newly acquired as image data for recording based on an instruction from the CPU 26 to a predetermined compression such as JPEG. Compress according to format. The compressed image data is recorded on the memory card 16 via a card interface (card I / F) 62. On the other hand, when the mode for recording uncompressed image data is selected, the image data is recorded in the memory card 16 without being compressed without performing the compression processing by the compression / decompression processing unit 31.

  In the playback mode, the image data read from the memory card 16 is decompressed by the compression / decompression processor 31 and output to the LCD 18 via the display controller 30.

  The CPU 26 is a main control unit that performs overall control of each circuit in the digital camera 10. The CPU 26 includes a data storage device such as a ROM 33 and a RAM 34. The ROM 33 stores programs processed by the CPU 26 and various data necessary for control. The RAM 34 is a working memory used when the CPU 26 performs various arithmetic processes. Used as The CPU 26 controls the operation of the corresponding circuit based on the input signals from the release button 14, the mode dial 15, and the operation unit 19, and performs autofocus (AF) control and automatic exposure (AE) in the preparatory stage before photographing. ) Perform control and “defective image detection processing” according to the present invention.

  The CPU 26 performs various calculations based on an AF evaluation value (focus evaluation value) and a luminance integrated value generated by a circuit in the digital signal processing unit 25 described later, and a lens driving unit including a focus motor based on the calculation result. 35, the focus lens in the imaging lens 11 is moved to the in-focus position, the aperture drive unit 36 including the iris motor is controlled to set an appropriate aperture value, and the charge accumulation time (electronic) of the CCD 21 is controlled. Set the shutter speed. Further, the CPU 26 determines a defective image caused by an external factor other than the imaging system, such as a finger hooking on the imaging lens 11 or the strobe light emitting unit 13, based on the integrated luminance value calculated for each block obtained by dividing the screen. To detect.

  In addition, when the flash light emission mode is set, the CPU 26 gives an instruction to the light emission control unit 37 according to the half-press operation and full-press operation of the release button 14 and causes the flash light emission unit 13 to perform the light emission operation. . The strobe light emitting unit 13 performs pre-light emission (preliminary light emission) for photometry when the release button 14 is pressed halfway, and performs main light emission for shooting when the release button 14 is fully pressed.

  As shown in FIG. 4, an AF calculation unit 40 for calculating an AF evaluation value is provided in the digital signal processing unit 25 described above. The AF calculation unit 40 includes a high-pass filter (HPF) 41, an absolute value processing unit 42, an AF area extraction unit 43, and an integration unit 44. The luminance signal (Y signal) generated by the YC signal generation circuit 45 and Of the color difference signals (Cr, Cb signals), the AF evaluation value is calculated using the Y signal. Specifically, the HPF 41 receives the Y signal for one screen from the YC signal generation circuit 45 and passes only the high-frequency component of the Y signal. The absolute value processing unit 42 converts the high frequency component that has passed through the HPF 41 into an absolute value, and inputs the absolute value to the AF area extraction unit 43. The AF area extraction unit 43 cuts out a signal in a focus target area (AF area) set in advance in the screen (for example, the center of the screen), and inputs this to the integration unit 44. The integrating unit 44 integrates the signals in the AF area that have been converted to absolute values, and outputs an integrated value (AF evaluation value).

  The AF evaluation value output from the integrating unit 44 is sent to the CPU 26. During the AF control, the CPU 26 controls the lens driving unit 35 to acquire the AF evaluation value at each lens position while moving the focus lens in the imaging lens 11, and the position where the AF evaluation value is maximized (the in-focus position). ) And the focus lens is moved to this in-focus position.

In the digital signal processing unit 25, a multi-division photometry unit 46 is provided. The multi-divided photometry unit 46 receives the Y signal for one screen from the YC signal generation circuit 45 and, as shown in FIG. 5, the 64 blocks B _{1 to} B ₆₄ of the image pickup surface 21a of the CCD 21 divided vertically and horizontally into eight. The Y signal is integrated for each block. Luminance integrated value _SY 1 _{to SY 64} for each of the blocks _B 1 _{.about.B 64} is sent to the CPU 26. During the AE control, the CPU 26 performs a well-known calculation process on the luminance integrated values SY _{1 to} SY ₆₄ based on a predetermined algorithm, and determines an appropriate exposure (aperture value, shutter speed).

On the other hand, during the defective image detection process, the CPU 26 performs the process described below based on FIG. 6 on the luminance integrated values SY _{1 to} SY ₆₄ input from the multi-division photometry unit 46 to detect a defective image. . First, when the CPU 26 acquires the luminance integrated values SY _{1 to} SY ₆₄ from the multi-division photometry unit 46 (step S10), as shown in FIG. 7, the blocks B _{1 to} B ₆₄ of the imaging surface 21a are divided into nine groups G1. -G9 are reintegrated, and the luminance integrated values SY ₁ -SY ₆₄ are grouped (step S11). Next, average luminance values GY _{1 to} GY ₉ of the luminance integrated values are calculated for each of the groups G1 to G9 (step S12).

Specifically, the average luminance values GY _{1 to} GY ₉ are calculated by integrating the luminance integrated values belonging to each group and dividing the integrated value by the number of blocks in the group, as shown in the following equation. .

GY ₁ = (SY ₁ + SY ₂ + SY ₉ + SY ₁₀ ) / 4
GY ₂ = (SY ₇ + SY ₈ + SY ₁₅ + SY ₁₆ ) / 4
GY ₃ = (SY ₄₉ + SY ₅₀ + SY ₅₇ + SY ₅₈ ) / 4
GY ₄ = (SY ₅₅ + SY ₅₆ + SY ₆₃ + SY ₆₄ ) / 4
GY ₅ = (SY ₃ +... + SY ₆ + SY ₁₁ +... + SY ₁₄ ) / 8
GY ₆ = (SY ₁₇ + SY ₁₈ +... + SY ₄₁ + SY ₄₂ ) / 8
GY ₇ = (SY ₂₃ + SY ₂₄ +... + SY ₄₇ + SY ₄₈ ) / 8
GY ₈ = (SY ₅₁ +... + SY ₅₄ + SY ₅₉ +... + SY ₆₂ ) / 8
GY ₉ = (SY ₁₉ +... + SY ₂₂ +... + SY ₄₃ +... + SY ₄₆ ) / 16

Next, a luminance difference (average luminance value difference) between one group set as a reference and a group adjacent thereto is calculated (step S13). Specifically, as shown in the following equation, the reference group and group G9 located in the center of the imaging surface 21a, the average luminance value of the group G1~G8 adjacent group G9 from the average luminance value GY ₉ Group G9 A value obtained by subtracting GY _{1 to} GY ₈ (brightness difference between groups DY _{1 to} DY ₈ ) is calculated.

DY _n = GY ₉ -GY _n (n = 1, 2,..., 8)

Then, it is determined whether or not each of the calculated inter-group luminance differences DY _{1 to} DY ₈ is greater than a predetermined threshold value α (α ≧ 0) (step S14). If the inter-group luminance differences DY _{1 to} DY ₈ are all smaller than the threshold value α (NO in step S14), it is determined that there is no abnormality (decrease in luminance) due to finger touching on the areas of the groups G1 to G8. finish. On the other hand, if any of the inter-group luminance differences DY _{1 to} DY ₈ is greater than the threshold value α (YES in step S14), it is determined that there is an abnormality (decrease in luminance) due to finger catching or the like, and the photographer is warned. (Step S15).

  As an aspect of step S15, specifically, the defect detection area (the group determined as NO in step S14) is displayed on the LCD 18 by hatching display, frame highlighting, or the like. In addition to this, a warning message or a warning icon may be displayed on the LCD 18. Further, the digital camera 10 may be provided with an acoustic output unit such as a speaker or a light emitting unit such as an LED, and a warning may be given by sound or light. FIG. 8 is a display example of the LCD 18 when the defect detection area is the group G2, in which the area 50 corresponding to the group G2 is indicated by hatching and a warning message 51 is displayed.

  This defective image detection process is performed when a through image is displayed and when the release button 14 is half-pressed. If a defect is detected when the release button 14 is half-pressed, as shown in FIG. In addition, it is preferable to display on the LCD 18 an instruction message 52 for notifying the photographer that shooting is performed as it is when the release button 14 is fully pressed and that the shutter button 14 is released to return to the live view display. Further, instead of notification by the instruction message 52, notification may be performed by icon display or voice.

Next, the operation of the digital camera 10 to which the present invention is applied will be described using the flowchart of FIG. When the digital camera 10 is set to the shooting mode, the CCD 21 captures an image (step S20), and the image data generated as a result of the signal processing is displayed on the LCD 18 as a through image (step S21). At this time, multi-division photometry is performed by multi-division photometry unit 46 based on the Y signal of the image data (step S22). As a result, luminance integrated values SY _{1 to} SY of the respective blocks obtained by dividing the imaging surface 21a into 64 are obtained. ₆₄ is calculated.

  Next, the CPU 26 performs the above-described defective image detection process based on the flowchart shown in FIG. 6 (step S23). At this time, if a defective image is detected due to a finger hooking on the imaging lens 11, a warning is displayed to the photographer as shown in FIG. Steps S20 to S23 are repeatedly executed periodically until the release button 14 is half-pressed (while Step S24 is NO). During this period, the photographer confirms the shooting angle of view with the through image displayed on the LCD 18 and performs framing of the subject. The photographer can recognize the cause such as finger catching by the warning displayed on the LCD 18 and take action to avoid the cause.

When the release button 14 is half-pressed (YES in step S24), the shooting preparation process including the AE / AF control described above is executed (step S25). Multi-segment photometry is also performed during the photographing preparation process, and the luminance integrated values SY _{1 to} SY ₆₄ are calculated. Similarly, the above-described defective image detection process is performed (step S26). At this time, when a defective image is detected due to a finger hooking on the imaging lens 11, a warning is displayed to the photographer as shown in FIG. If there is no warning display or if there is no problem with the image even if there is a warning display, the photographer presses the release button 14 as it is (NO in step S27 and YES in step S28), thereby recording. Image data is captured and recorded in the memory card 16 (photographing / recording process) (step S29). On the other hand, when the photographer displays the warning, if the release button 14 is released (YES in step S27), the photographer returns to the live view display and can perform the framing of the subject again.

  Thus, since the digital camera 10 has a defective image detection processing function, the photographer can recognize the image defect in advance before the main photographing to avoid the defect, and the memory card 16 of the defective image can be avoided. Consumption can be prevented.

  The flowchart of FIG. 11 shows the operation of the digital camera 10 in the strobe light emission mode. In addition, the same code | symbol is attached | subjected about the step which performs the same process as the time of said strobe non-light emission mode. Only the parts different from the above will be described.

  In the flash emission mode, immediately after the release button 14 is half-pressed (YES in step S24), the flash emission unit 13 is driven to perform pre-flash toward the subject (step S30). The subsequent shooting preparation process (step S25) and defective image detection process (step S26) are performed based on the image data acquired under this pre-emission. Further, immediately after the release button 14 is fully pressed (YES in step S28), the flash light emitting unit 13 is driven to perform main light emission toward the subject (step S31), and the photographing / recording process (step S29) is performed. This is performed under the main light emission.

  As a result, the photographer can recognize an image defect due to a finger catching on the strobe light emitting unit 13 in advance before the actual photographing and avoid the defect even in the strobe light emission mode.

In the above embodiment, as shown in FIG. 5, the multi-division photometry unit 46 divides the imaging surface 21a into 64 blocks B _{1 to} B ₆₄ to perform photometry. The size of the block is not limited to this, and may be changed as appropriate.

Further, in the above embodiment, during the defective image detection process, as shown in FIG. 7, the CPU 26 groups the blocks B _{1 to} B ₆₄ so as to subdivide the peripheral portion where the finger is likely to be caught, and the imaging surface. Although nine groups G1 to G9 are set in 21a, the number of groupings and the size of each group (number of blocks) may be changed as appropriate.

In the above embodiment, during the defective image detection process, the CPU 26 obtains the average luminance values GY _{1 to} GY ₉ of each group, and then sets the group G9 located at the center of the imaging surface 21a as a reference group. The difference between the average luminance value GY ₉ of the group and the average luminance values GY _{1 to} GY ₈ of the neighboring adjacent groups G1 to G8 is calculated, but the reference group is not limited to this, and can be changed as appropriate. Good.

  In addition, in the defective image detection process of the above-described embodiment, there is a possibility that the detection operation cannot be accurately performed in a situation where there is a large luminance difference in the imaging surface 21a, such as during backlighting. Specifically, in the situation where the brightness value of the adjacent group in the peripheral part is larger than that of the reference group due to backlighting, if a finger is generated in the adjacent group, the relationship between the adjacent group in which the finger is generated and the reference group Since the luminance difference between them decreases, it is not detected as a defective image. Defect image detection processing for backlighting to solve this will be described below.

  12 and 13 are flowcharts showing a defective image detection process for backlight. The same steps as those in the defective image detection process in FIG. 6 are denoted by the same reference numerals. Only the parts different from the above will be described.

After calculating the inter-group luminance differences DY _{1 to} DY ₈ in step S13, the CPU 26 compares and determines whether all of the inter-group luminance differences DY _{1 to} DY ₈ are greater than 0 (step S40). In the case of YES determination in step 40, it is determined that the brightness of the neighboring groups G1 to G8 is larger than the brightness of the reference group G9 located at the center of the imaging surface 21a, and the backlight is in the backlit state, and the process proceeds to step S41. To do. On the other hand, in the case of NO determination in step 40, it is determined that the backlight is not in the backlit state, the process proceeds to step S14 and the same processing as described above is performed.

In step S41, it selects the top two adjacent large group of average luminance, by dividing by the average luminance value of the adjacent group selected average luminance value GY ₉ of the reference group G9, for correcting the brightness gradient due to backlight A correction coefficient γ is calculated. For example, when the top two adjacent groups with the highest average luminance are groups G1 and G5, the correction coefficient γ is calculated according to the following equation. That is, the correction coefficient γ is a ratio of average luminance between the upper two adjacent groups and the reference group.

γ = GY ₉ / {(GY ₁ + GY ₅ ) / 2}

Reduced In step S42, as shown in the following equation, from the mean luminance value GY ₉ of the reference group G9, a value obtained by respectively multiplying the correction coefficient γ in each average luminance value _GY 1 _{~GY 8} adjacent groups G1~G8 respectively Thus, the inter-group luminance differences CY _{1 to} CY ₈ are calculated after subtracting the luminance gradient due to backlight.

CY _n = GY ₉ −γ · GY _n (n = 1, 2,..., 8)

In step S43, it is determined whether each of the calculated inter-group luminance differences CY _{1 to} CY ₈ is greater than a predetermined threshold value α (α ≧ 0). If the inter-group luminance differences CY _{1 to} CY ₈ are all smaller than the threshold value α (NO in step S43), it is determined that there is no abnormality (decrease in luminance) due to fingering or the like on the areas of the groups G1 to G8. finish. On the other hand, if any of the inter-group luminance differences CY _{1 to} CY ₈ is larger than the threshold value α (YES in step S43), it is determined that there is an abnormality (decrease in luminance) due to finger catching or the like, and the photographer is warned. (Step S44). The aspect of step S44 is the same as that of step S15.

  In step S41, the top two adjacent groups having the highest average luminance are selected, but the number of groups selected may be three or more. Increasing the number of selected blocks increases the accuracy of correcting the brightness gradient, but decreases the processing time for one. For this reason, an optimal number may be determined based on the balance between the processing time and the correction accuracy.

  Next, FIG. 14 is an example in which a thinning processing unit 60 is provided before the multi-division photometry unit 46 in the digital signal processing unit 25. The thinning processing unit 60 thins out the Y signal output from the YC signal generation circuit 45 in the vertical or horizontal direction, or the vertical and horizontal directions of the image data, and transfers the thinned image to the multi-division photometry unit 46. Thereby, the integration processing time of the Y signal by the multi-division photometry unit 46 is reduced, so that the detection process can be speeded up.

  In the above-described embodiment, the multi-division photometry unit 46 is shared for the AE control and the defective image detection process. It may be provided. In this case, the thinning-out processing unit 60 is provided in the previous stage of the multi-division photometry unit for detecting a defective image.

Next, the digital camera 70 shown in FIG. 15 includes a bent optical zoom lens mechanism 71 inside. The bendable zoom lens mechanism 71 is obtained by bending an optical system from the imaging lens 73 to the imaging surface 21a of the CCD 21 by 90 ° with a prism 72, and the lens barrel 74 is not movable and is fixed to the front surface of the digital camera 70. Has been. As described above, in the case of a digital camera having a bent optical zoom lens mechanism, it is preferable to apply the present invention because the image pickup lens is almost flush with the front surface of the main body and thus finger catching is likely to occur. .

  Similarly, in the case of a digital camera including a zoom lens mechanism constituted by a so-called liquid lens, since the lens barrel does not move, finger catching is unlikely to occur, and it is preferable to apply the present invention. A liquid lens is a lens that converges or diverges light by an interface between an aqueous solution and an oil, and a desired refractive power can be obtained by changing the shape of the interface. Optical zoom can be realized without moving.

  The present invention is not limited to a digital camera, and can be applied to any imaging device that generates image data using a solid-state imaging device, such as a digital video camera or a mobile phone with a camera. . As the solid-state imaging device, a CMOS image sensor or the like can be used in addition to the CCD image sensor.

It is a front side external appearance perspective view of a digital camera. 1 is a rear perspective view of a digital camera. It is a block diagram which shows the electric constitution of a digital camera. It is a block diagram which shows the AF calculating part and multi-division photometry part contained in a digital signal processing part. It is a figure which shows the mode of the block division of the imaging surface at the time of multi-segment photometry. It is a flowchart explaining a defective image detection process. It is a figure which shows the mode of grouping of the block of an imaging surface. It is a figure which shows the example of a warning display to LCD. It is a figure which shows the example of a warning display to LCD. It is a flowchart explaining the effect | action of a digital camera at the time of flash non-light emission mode. It is a flowchart explaining the effect | action of the digital camera at the time of flash emission mode. It is a flowchart which shows the example of improvement of a defect image detection process. It is a flowchart which shows the example of improvement of a defect image detection process. It is a block diagram which shows the example which provided the thinning-out process part in the front | former stage of the multi-division photometry part. 1 is a front perspective view of a digital camera equipped with a bent optical zoom lens mechanism. FIG.

Explanation of symbols

10 Digital camera (photographing device)
11 Image pickup lens 13 Strobe light emitting unit 14 Release button 18 LCD (display means, warning means)
21 CCD (solid-state image sensor)
21a Imaging surface 23 Analog signal processing unit 24 A / D converter 26 CPU (grouping means, average luminance calculating means, inter-group luminance calculating means, comparison determining means, backlight determining means, correction coefficient calculating means, between backlight groups Luminance calculation means, backlit comparison judgment means)
25 Digital signal processing unit 28 Memory 40 AF calculation unit 45 YC signal generation circuit 46 Multi-division photometry unit (multi-division photometry unit)
60 Thinning processing unit (thinning processing means)
71 Bending zoom lens mechanism 72 Prism

Claims (11)

In an imaging device that converts an imaging signal obtained by imaging subject light with a solid-state imaging device into digital image data and records the image data on a recording medium.
Dividing photometric means for dividing the image data into a plurality of blocks, and integrating a luminance signal for each of the divided blocks;
Grouping means for grouping the plurality of blocks divided by the divided photometry means into a plurality of groups smaller than the total number of blocks;
Average luminance value calculation means for calculating an average luminance value for each group using the luminance integrated value of each block calculated by the divided photometry means,
One group of the plurality of groups is set as a reference group, and the difference between groups is calculated by subtracting the average luminance value of each group adjacent to the reference group from the average luminance value of the reference group. Means,
A comparison determination means for comparing and determining the inter-group luminance difference calculated by the inter-group luminance difference calculation means with a predetermined value;
An imaging device comprising: warning means for warning the photographer that the image data is a defective image when the comparison and determination means determines that the luminance difference between groups is greater than a predetermined value. apparatus.   The photographing apparatus according to claim 1, wherein the inter-group luminance difference calculating unit sets a group located in a central portion of the image data as a reference group. A backlight determination unit that determines that the backlight is in a backlight state when an average brightness value of a neighboring adjacent group is larger than an average brightness value of the reference group;
When it is determined that the backlight is in the backlight state by the backlight determination means, the top two or more groups having the largest average brightness value are selected from the adjacent groups, and the average brightness value of the reference group is selected as the average brightness value of the selected group. A correction coefficient calculation means for calculating a correction coefficient for correcting the luminance gradient due to backlight,
Backlighting group for calculating a luminance difference between groups in which a luminance gradient is corrected by subtracting a value obtained by multiplying the average luminance value of each adjacent group adjacent to the reference group by the correction coefficient from the average luminance value of the reference group Brightness difference calculating means,
A backlight comparison comparison determining unit that compares the luminance difference between groups calculated by the backlight luminance difference calculating unit with a predetermined value;
The warning means warns the photographer that the image data is a defective image when the backlight comparison comparison determination means determines that the inter-group luminance difference is greater than a predetermined value. The imaging device according to claim 2.   4. The photographing apparatus according to claim 1, wherein the division photometry unit divides the image data into eight equal parts in the vertical and horizontal directions to form 64 blocks. 5.   5. The grouping unit according to claim 1, wherein the grouping unit groups the plurality of blocks so that a central portion of the image data is large and a peripheral portion is small. 6. Shooting device.   The warning means is a display means for displaying the image data, and shows on the screen a group for which the luminance difference between groups is determined to be larger than a predetermined value by the comparison determination means or the backlight comparison comparison means. The imaging apparatus according to claim 1, wherein a warning is given by:   The photographing apparatus according to any one of claims 1 to 6, further comprising: a thinning-out processing unit that performs a thinning-out process of a luminance signal in a stage preceding the multi-segment photometry unit.   8. The photographing apparatus according to claim 1, further comprising a strobe light emitting unit that emits strobe light toward a subject when performing imaging with the solid-state image sensor. 9.   9. The photographing apparatus according to claim 1, wherein the optical system that guides subject light to the solid-state imaging device includes a bending optical zoom lens mechanism.   9. The photographing apparatus according to claim 1, wherein the optical system that guides subject light to the solid-state imaging device includes a zoom lens mechanism that includes a liquid lens. In an imaging method for converting an imaging signal obtained by imaging subject light with a solid-state imaging device into digital image data and recording the image data on a recording medium,
Dividing the image data into a plurality of blocks, and integrating a luminance signal for each of the divided blocks;
Grouping the plurality of blocks divided by the divided photometry means into a plurality of groups less than the total number of blocks;
Calculating an average luminance value for each group using the luminance integrated value of each block calculated by the divided photometry means;
Calculating a luminance difference between groups by setting one group of the plurality of groups as a reference group, and subtracting the average luminance value of each group adjacent to the reference group from the average luminance value of the reference group;
A step of comparing and determining the inter-group luminance difference calculated by the inter-group luminance difference calculating means with a predetermined value;
And a step of warning the photographer that the image data is a defective image when the comparison / determination means determines that the luminance difference between groups is greater than a predetermined value. .

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