JP5807378B2 - Imaging apparatus, imaging method, and imaging program - Google Patents

Description

  The present invention relates to an imaging apparatus, an imaging method, and an imaging program. More specifically, the present invention relates to an imaging apparatus, an imaging method, and an imaging program suitable for white balance correction.

  In an imaging device using a CCD (Charge Coupled Device) image sensor or the like as an imaging device, the color change of the output signal of the CCD due to the color temperature of the light source is corrected so as not to feel unnatural to the human eye. White balance correction is one of the essential functions.

  In white balance correction, the shooting condition (ie, light source) such as outdoors (clear weather), cloudy weather (shade), incandescent light, fluorescent light, etc. is judged, and the optimal white balance gain is determined according to the shooting condition. Although a technique for performing correction is known, for example, a scene with a cloudy day (shade) and green and a scene under a fluorescent lamp in a room are similar because the brightness (illuminance) and color distribution are similar. It is known that it is difficult, and there are cases where it is impossible to make an appropriate correction by misjudging the shooting situation.

  This is due to the fact that when threshold processing is performed based only on the brightness and color distribution, there is a portion where the distribution of indoor light and outdoor light overlaps and cannot be correctly identified. There was a problem that the green part of the scene was corrected to white and the entire image became magenta.

  To deal with such a problem, for example, Patent Document 1 discloses a white balance correction apparatus that estimates a light source based on a frequency component, an edge amount component, and brightness information and performs white balance correction. Patent Document 2 discloses an image processing apparatus that performs white balance correction based on a plurality of pieces of feature information such as hue and saturation information.

  However, the technique described in the above-mentioned patent document has a problem in that a large amount of information needs to be handled when determining the white balance gain, leading to an increase in processing amount and an increase in memory capacity.

  In addition, when hue is used as a criterion, there is a problem that it is difficult to discriminate between a white fluorescent lamp and a green plant, and it is difficult to discriminate because saturation information can be the same value depending on the exposure of the imaging device. .

  Accordingly, the present invention provides an imaging apparatus and an imaging method capable of easily performing good white balance correction without color misregistration by performing white balance correction using a green block in which a green scene is captured in an image area. And an imaging program.

In order to achieve such an object, an imaging apparatus according to the present invention divides light incident from an optical system into an electrical signal and outputs it as an imaging signal, and an image area corresponding to the imaging element is divided into a plurality of blocks. A block dividing unit that performs a white balance evaluation value acquisition unit that calculates a white balance evaluation value based on an imaging signal for each block, and a green block determination unit that determines whether the block is a green block based on the white balance evaluation value And a green block variance calculating means for calculating a variance value based on the white balance evaluation value for the block determined to be a green block by the green block determining means, a white balance evaluation value and a preset white extraction range. a white extraction means for extracting a white block on the basis of the white balance evaluation of variance and the white block Based on includes a white balance correction coefficient calculation means for calculating a white balance correction coefficient, a, and performs white balance control on the basis of the white balance correction coefficient.

An imaging method according to the present invention is an imaging method in an imaging apparatus including an imaging device that converts light incident from an optical system into an electrical signal and outputs the electrical signal, and an image region corresponding to the imaging device is obtained. Block division processing that divides into multiple blocks, white balance evaluation value acquisition processing that calculates a white balance evaluation value based on the imaging signal for each block, and whether or not the block is a green block based on the white balance evaluation value Green block determination processing, green block dispersion calculation processing for calculating a dispersion value based on a white balance evaluation value, a white balance evaluation value, and a preset value for a block determined to be a green block by the green block determination processing a white extraction process of extracting a white block on the basis of the white extraction ranges, ho dispersion values and the white block Based on the site balance evaluation value, and to perform the white balance correction coefficient calculation processing of calculating the white balance correction coefficient, and white balance processing on the basis of the white balance correction coefficients, the.

In addition, an imaging program according to the present invention divides an image area corresponding to an imaging device into a plurality of blocks in an imaging device including an imaging device that converts light incident from an optical system into an electrical signal and outputs the electrical signal. Block division processing, white balance evaluation value acquisition processing for calculating a white balance evaluation value based on an imaging signal for each block, and green block determination processing for determining whether the block is a green block based on the white balance evaluation value And a green block variance calculation process for calculating a variance value based on a white balance evaluation value for a block that is determined to be a green block by the green block determination process, a white balance evaluation value, and a preset white extraction range. a white extraction process of extracting a white block on the basis of the dispersion value and a white balance Review of the white block Based on the value, but to execute the white balance correction coefficient calculation processing of calculating the white balance correction coefficient, and white balance processing on the basis of the white balance correction coefficients, the.

  According to the present invention, it is possible to easily perform good white balance correction without color misregistration.

BRIEF DESCRIPTION OF THE DRAWINGS It is an example of the external view of the digital camera which is one Embodiment of the imaging device which concerns on this invention, (a) is a top view, (b) is a front view, (c) shows a back view. It is an example of the functional block diagram of the imaging device which concerns on this embodiment. It is a schematic diagram of the control block of CPU which concerns on white balance control. It is a flowchart (1st Embodiment) of a white balance process. It is explanatory drawing of the green block and white block extraction in the two-dimensional color coordinate which makes G / R the x-axis and G / B is the y-axis. It is an example of the graph which shows the outdoor weighting rate with respect to a dispersion value. It is a flowchart (2nd Embodiment) of a white balance process. It is an example of the graph which shows the outdoor weighting rate suppression coefficient with respect to brightness.

  Hereinafter, the configuration according to the present invention will be described in detail based on the embodiment shown in FIGS.

  The image pickup apparatus (digital camera) according to the present embodiment converts an incident light from an optical system into an electric signal and outputs it as an image pickup signal (CCD 121), and an image area corresponding to the image pickup element into a plurality of blocks. Block dividing means (101) for dividing, white balance evaluation value acquiring means (103) for calculating a white balance evaluation value based on the imaging signal for each block, and whether or not the block is a green block based on the white balance evaluation value A green block determination means (104) for determining a dispersion value for a block determined to be a green block by the green block determination means based on a white balance evaluation value; White extraction to extract white blocks based on white balance evaluation value and preset white extraction range And a white balance correction coefficient calculating means (107) for calculating a white balance correction coefficient based on the variance value and the white block, and performing white balance control based on the white balance correction coefficient. is there.

[First Embodiment]
(Configuration of imaging device)
In the present embodiment, a digital camera will be described as an example of an imaging apparatus. FIG. 1 shows an external view of a digital camera, (a) shows a top view of the camera, (b) shows a front view of the camera, and (c) shows a rear view of the camera. Note that the imaging apparatus is not limited to a digital camera, and may be any imaging apparatus having a white balance correction function.

  As shown in FIG. 1A, the digital camera has a sub LCD 1, a release shutter 2 (SW1), and a mode dial 4 (SW2) on the upper surface.

  As shown in FIG. 1B, the digital camera has a strobe light emitting unit 3, a distance measuring unit 5, a remote control light receiving unit 6, a lens unit 7, and an optical viewfinder (front) 11 on the front. Have. A memory card throttle 23 indicates a throttle for inserting a memory card 34 such as an SD card, and is provided on the side of the camera.

  As shown in FIG. 1C, the digital camera has an AFLED (autofocus LED) 8, a strobe LED 9, an LCD monitor (display means) 10, an optical viewfinder (back surface) 11, and a zoom on the back surface. It has a button (zoom lever) TELE12 (SW4), a power switch 13 (SW13), a zoom button (zoom lever) WIDE14 (SW3), and a self-timer / deletion switch 15 (SW6).

  Furthermore, the menu switch 16 (SW5), the OK switch 17 (SW12), the left / image confirmation switch 18 (SW11), the down / macro switch 19 (SW10), the up / strobe switch 20 (SW7), the right A switch 21 (SW8) and a display switch 22 (SW9) for displaying an image are provided.

  FIG. 2 is a functional block diagram of a control system of the digital camera shown in FIG. The system configuration inside the digital camera will be described below.

  As shown in FIG. 2, in this digital camera, a CCD 121 serving as a solid-state imaging device, on which a subject image incident through a photographing lens system installed in the lens unit 7 forms an image on a light receiving surface, is output from the CCD 121. Front-end IC (F / E) 120 that processes signals (analog RGB image signals) into digital signals, signal-processing IC 110 that processes digital signals output from front-end IC (F / E) 120, and data temporarily An SDRAM 33 to be stored, a ROM 30 in which a control program and the like are stored, a motor driver 32 and the like are provided.

  The lens unit 7 includes a zoom lens, a focus lens, a mechanical shutter, and the like, and is driven by a motor driver 32. The motor driver 32 is controlled by a microcomputer (CPU, control unit) 111 included in the signal processing IC 110.

  The CCD 121 is a solid-state imaging device for photoelectrically converting an optical image, and an RGB primary color filter as a color separation filter is arranged on a plurality of pixels constituting the CCD, and an electrical signal (analogue) corresponding to RGB three primary colors. RGB image signal) is output.

  A front-end IC (F / E) 120 is a CDS 122 that performs sampling hold (correlated double sampling) on the CCD output electrical signal (analog image data), and an AGC (Auto Gain Control) 123 that adjusts the gain of the sampled data. A vertical synchronization signal (VD) and a horizontal synchronization signal (HD) are supplied from an A / D converter (A / D) 124 that performs digital signal conversion and a CCD I / F 112, and drive timing signals for the CCD 121 and the F / E 120 are supplied. A TG (timing generator: control signal generator) 125 is generated.

  The oscillator (clock generator) supplies a clock to the system clock of the signal processing IC 110 including the CPU 111, the TG 125, and the like. The TG 125 receives the oscillator clock and supplies a pixel clock for pixel synchronization to the CCD I / F 112 in the signal processing IC 110.

  A digital signal input from the F / E 120 to the signal processing IC 110 is temporarily stored as RGB data (RAW-RGB) in the SDRAM 33 by the memory controller 115 via the CCD I / F 112.

  The signal processing IC 110 includes a CPU 111 that performs system control, a CCD I / F 112, a resizing processing unit 113, a memory controller 115, a display output control unit 116, a compression / expansion unit 117, a media I / F unit 118, a YUV conversion unit 119, and the like. ing.

  The CCD I / F 112 outputs a vertical synchronizing signal (VD) and a horizontal synchronizing signal (HD), takes in a digital (RGB) signal input from the A / D 124 in accordance with the synchronizing signal, and passes through the memory controller 115. RGB data is written to the SDRAM 33.

  The display output control unit 116 sends the display data written in the SDRAM 33 to the display unit, and displays the captured image. The display output control unit 116 can display on the LCD monitor 10 built in the digital camera, or output it as a TV video signal and display it on an external device.

  The display data here is OSD (on-screen display) data for displaying a natural image YCbCr, a shooting mode icon, etc., and the memory controller 115 reads and displays the data placed on the SDRAM 33. The data is sent to the output control unit 116, and the data synthesized by the display output control unit 116 is output as video data.

  The compression / decompression unit 117 compresses the YCbCr data written in the SDRAM 33 during recording and outputs JPEG-encoded data. During reproduction, the compression / decompression unit 117 decompresses the read JPEG-encoded data into YCbCr data and outputs the YCbCr data.

  The media I / F 118 reads data in the memory card 34 to the SDRAM 33 or writes data on the SDRAM 33 to the memory card 34 in accordance with an instruction from the CPU 111.

  The YUV conversion unit 119 converts the RGB data temporarily stored in the SDRAM 33 into luminance Y and color difference CbCr data (YUV data) based on the image development processing parameters set by the CPU 111, and writes back to the SDRAM 33.

  The resizing processing unit 113 reads out YUV data and performs size conversion to a size necessary for recording, size conversion to a thumbnail image, size conversion to a size suitable for display, and the like.

  In addition, the CPU 111 which is a control unit that controls the overall operation loads a control program and control data for controlling the camera stored in the ROM 30 at the time of startup into, for example, the SDRAM 33, and performs the overall operation based on the program code. Control.

  The CPU 111 performs imaging operation control, setting of image development processing parameters, in accordance with an instruction by a button key of the operation unit 31, an external operation instruction from a remote controller (not shown), or a communication operation instruction by communication from an external terminal such as a personal computer. Performs memory control and display control.

  The operation unit 31 is used by the photographer to instruct the operation of the digital camera, and a predetermined operation instruction signal is input to the control unit by the operation of the photographer. For example, as shown in FIG. 1, various button keys such as a two-stage (half-pressed and fully-pressed) release shutter 2 for instructing shooting, zoom buttons 12 and 14 for setting an optical zoom and an electronic zoom magnification are provided.

  When the operation unit 31 detects that the power key of the digital camera is turned on, the CPU 111 performs a predetermined setting for each block. With this setting, an image received by the CCD 121 via the lens unit 7 is converted into a digital video signal and input to the signal processing IC 110.

  The digital signal input to the signal processing IC 110 is input to the CCD I / F 112. The CCD I / F 112 performs processing such as black level adjustment on the photoelectrically converted analog signal and temporarily stores it in the SDRAM 33. The RAW-RGB image data stored in the SDRAM 33 is read by the YUV conversion unit 119, and subjected to gamma conversion processing, white balance processing, edge enhancement processing, and YUV conversion processing, and is written back to the SDRAM 33 as YUV image data. .

  The YUV image data is read by the display output control unit 116. For example, if the output destination is an NTSC system TV, the resizing processing unit 113 performs horizontal / vertical scaling processing according to the system, and Is output. By performing this process for each VD, monitoring which is a display for confirmation before still photographing is performed.

(Operation of imaging device)
Next, the monitoring operation and still image shooting operation of the digital camera will be described. This digital camera performs a still image shooting operation while performing a monitoring operation as described below in the still image shooting mode.

  First, when the photographer turns on the power switch 13 and sets the mode dial 4 to the photographing mode (still image photographing mode), the digital camera is activated in the recording mode. When the CPU 111 detects this, the CPU 111 outputs a control signal to the motor driver 32 to move the lens unit 7 to a photographing position, and the CCD 121, F / E 120, signal processing IC 110, SDRAM 33, ROM 30, LCD monitor 10 And so on.

  Then, by directing the photographic lens system of the lens unit 7 toward the subject, a subject image incident through the photographic lens system is formed on the light receiving surface of each pixel of the CCD 121. An electrical signal (analog RGB image signal) corresponding to the subject image output from the CCD 121 is input to the A / D 124 via the CDS 122 and AGC 123, and converted into 12-bit RAW-RGB data by the A / D 124.

  This RAW-RGB data is taken into the CCD I / F 112 of the signal processing IC 110 and stored in the SDRAM 33 via the memory controller 115. The RAW-RGB data read from the SDRAM 33 is input to the YUV conversion unit 119 and converted into YUV data that can be displayed, and then the YUV data is stored in the SDRAM 33 via the memory controller 115. .

  The YUV data read from the SDRAM 33 via the memory controller 115 is sent to the LCD monitor 10 via the display output control unit 116, and a captured image (moving image) is displayed. At the time of monitoring in which a photographed image is displayed on the LCD monitor 10, one frame is read out in a time of 1/30 seconds by thinning out the number of pixels by the CCD I / F 112.

  In this monitoring operation, the photographed image (moving image) is only displayed on the LCD monitor 10 functioning as an electronic viewfinder, and the release button 2 is not yet pressed (including half-pressed).

  By displaying the photographed image on the LCD monitor 10, the composition for photographing a still image can be confirmed. In addition, it can output as a TV video signal from the display output control part 116, and can display a picked-up image (moving image) on external TV (television) via a video cable.

  Then, the CCD I / F 112 of the signal processing IC 110 determines an AF (automatic focus) evaluation value, an AE (automatic exposure) evaluation value, an AWB (auto white balance) evaluation value (WB evaluation value) from the captured RAW-RGB data. (Also referred to as AWB evaluation value).

  The AF evaluation value is calculated by, for example, the output integrated value of the high frequency component extraction filter or the integrated value of the luminance difference between adjacent pixels. When in the in-focus state, the edge portion of the subject is clear, so the high frequency component is the highest. By using this, at the time of AF operation (focus detection operation), AF evaluation values at each focus lens position in the photographing lens system are acquired, and AF operation is performed with the maximum point as the focus detection position. Is executed.

  The AE evaluation value and the WB evaluation value are calculated from the integrated values of the RGB values in the RAW-RGB data. For example, the screen (image area) corresponding to the light receiving surface of all the pixels of the CCD 121 is equally divided into 256 blocks (areas) (horizontal 16 divisions and vertical 16 divisions), and the RGB integration of each block is calculated.

  Then, the control unit reads the calculated RGB integrated value, and in the AE process, calculates the luminance of each area (block) of the screen and determines an appropriate exposure amount from the luminance distribution. Based on the determined exposure amount, exposure conditions (the number of electronic shutters of the CCD 121, the aperture value of the aperture unit, the insertion and removal of the ND filter, etc.) are set. In the AWB process, an AWB control value that matches the color of the light source of the subject is determined from the RGB distribution. By this AWB process, white balance is adjusted when the YUV conversion unit 119 performs conversion processing to YUV data. Note that the AE process and the AWB process are continuously performed during monitoring.

  Then, when a still image shooting operation in which the release button is pressed (half-pressed to fully pressed) is started during the monitoring operation, an AF operation that is a focus position detection operation and a still image recording process are performed.

  That is, when the release button is pressed (half to full), the focus lens of the photographing lens system is moved by a drive command from the control unit to the motor driver 32. For example, contrast evaluation called so-called hill-climbing AF is performed. The AF operation of the method is executed.

  When the AF (focusing) target range is the entire region from infinity to close, the focus lens of the taking lens system moves to each focus position from close to infinity or from infinity to close, and the CCD I / F 112 The control unit reads the AF evaluation value at each focus position calculated in step (1). Then, the focus lens is moved to the in-focus position with the point where the AF evaluation value at each focus position is maximized as the in-focus position, and in-focus.

  Then, AE processing is performed, and when the exposure is completed, the mechanical shutter unit is closed by a drive command from the control unit to the motor driver 32, and an analog RGB image signal for a still image is output from the CCD 121. Then, as in the monitoring, the data is converted into RAW-RGB data by the A / D 124 of the F / E 120.

  The RAW-RGB data is taken into the CCD I / F 112 of the signal processing IC 110, converted into YUV data by the YUV conversion unit 119, and stored in the SDRAM 33 via the memory controller 115. The YUV data is read from the SDRAM 33, converted into a size corresponding to the number of recording pixels by the resizing processing unit 113, and compressed to image data in the JPEG format or the like by the compression / decompression unit 117. The compressed image data such as JPEG format is written back to the SDRAM 33, read from the SDRAM 33 via the memory controller 115, and stored in the memory card 34 via the media I / F 118.

(White balance control)
FIG. 3 is an explanatory diagram of a control block of the CPU 111 related to white balance control. The white balance control executed by each control block of the CPU 111 will be described with reference to the processing flowchart shown in FIG. Note that each of the block dividing unit 101, the RGB integrating unit 102, the white balance evaluation value acquiring unit 103, the green block determining unit 104, the green block variance calculating unit 105, the white extracting unit 106, and the white balance coefficient calculating unit 107 includes a CPU 111. The software (imaging program) executed in (1) is executed by the imaging device, and data necessary for the execution is loaded into the SDRAM 33, for example.

  First, as described above, the RGB integrating means 102 corresponds to the image area (the light receiving surface of all the pixels of the CCD 121) that is divided into 256 blocks by the block dividing means 101 after RAW-RGB is taken into the CCD I / F 112. Screen) for each block, R values, G values, and B values (also simply referred to as R, G, and B, collectively referred to as RGB), integrated values (R integrated values, G integrated values, and B integrated values). (S101: RGB integrated value acquisition process). The R value, the G value, and the B value are expressed by, for example, 8 bits, but the quantification method is not particularly limited.

Next, the white balance evaluation value acquisition unit 103 obtains an average value of RGB for each pixel (also referred to as an R average value, a G average value, or a B average value from the acquired RGB integrated values of each block, and is collectively referred to as an RGB average value. Is calculated), and the WB evaluation value (G / R, G / B) and the AE evaluation value (Y) are calculated (S102: WB evaluation value, AE evaluation value generation process). Here, the calculation of the WB evaluation value (G / R, G / B) and the AE evaluation value (Y) can be calculated by, for example, the following equations (1) to (3).
G / R = (G average value × 100) / R average value (1)
G / B = (G average value × 100) / B average value (2)
Y = (R average value × 3 + G average value × 6 + B average value) / 10 (3)
Note that the calculation method of the WB evaluation value (G / R, G / B) and the AE evaluation value (Y) is not limited to the above example, but may be other known or new calculation methods. good.

  Next, the green block determination means 104 determines a green block (green evaluation value) based on the WB evaluation values (G / R, G / B) (S103: green block determination processing). In the green block determination process, a predetermined threshold is provided for each of WB evaluation values G / R and G / B, and a block in which both exceed the threshold is determined to be a green block. For example, as shown in FIG. 5, both G / R and G / B values are large (exceeding a predetermined threshold value) on a two-dimensional color coordinate having G / R as the x axis and G / B as the y axis. ) A block of the WB evaluation value in the area (filled portion in FIG. 5) is determined as a green block.

Next, the green block variance calculation unit 105 calculates a variance value using, for example, Equation 1 based on the WB evaluation values (G / R, G / B) of the green block (S104: variance value calculation process).

  On the other hand, based on the WB evaluation values (G / R, G / B), the white extraction means 106 stores a white extraction block (white block) within the preset white extraction range (S105: white). Extraction process). The specific processing method of the white extraction processing is not particularly limited, and a known or new white block extraction method may be used. For example, as shown in FIG. White detection is performed on a plurality of ellipse or rectangular frames along a blackbody radiation characteristic curve (blackbody radiation curve) (indicated by symbol c in FIG. 5) on two-dimensional color coordinates with G / B as the y-axis. It may be set as a frame, and when the WB evaluation value is included in the white detection frame, it may be detected as a white extraction block.

  Note that the processing by the green block determination unit 104 and the green block variance calculation unit 105 (S103 to S104) and the processing by the white detection unit 106 (S105) are not limited to the above example. Alternatively, it may be processed in parallel.

Next, the white balance correction coefficient calculation unit 107 determines whether or not the number of white extraction blocks extracted in the white extraction process (S105) is equal to or greater than a predetermined number. The WB evaluation value (G / R, G / B) of the white extraction block is weighted by the average luminance (Y) of the corresponding block and then integrated to calculate G / R and G / B per pixel. (S106: High luminance weighting process).

  On the other hand, when there are no more than a certain number of white extraction blocks, the WB evaluation values (G / R, G / B) of all the blocks are integrated to calculate G / R, G / B per pixel. The average values of G / R and G / B per pixel obtained are defined as WB correction coefficients Rgain and Bgain.

  Next, the white balance correction coefficient calculation unit 107 uses the outdoor weighting rate according to the dispersion value calculated in the dispersion value calculation process (S104) based on the relationship between the dispersion value and the outdoor weighting rate as shown in FIG. Is calculated (S107: outdoor weighting rate calculation process).

  Furthermore, based on the calculated outdoor weighting rate, a weighted average of the calculated G / R and G / B per pixel and the outdoor white balance (referring to a white balance setting suitable for shooting outdoors on a sunny day) is calculated. Thus, white balance correction coefficients Rgain and Bgain are obtained (S108: outdoor weighting process).

  Finally, white balance correction is performed by multiplying the R and B pixels of the entire screen by WB correction coefficients Rgain and Bgain (S109: white balance correction coefficient multiplication process).

  Since the above processing (S107 to S109) is statistically known that the variance of the white balance evaluation value is higher in the outdoor green scene than under the fluorescent lamp, the number of green blocks is increased and the variance value is increased. As the value increases, the outdoor weighting factor is increased to bring the white balance correction coefficient closer to a predetermined white balance setting condition (a white balance setting condition suitable for shooting outdoors in fine weather). With the above processing, according to the imaging apparatus according to the present embodiment, it is possible to perform good white balance control without color shift even in an outdoor green scene with a simple configuration.

[Second Embodiment]
Hereinafter, other embodiments of the imaging apparatus according to the present embodiment will be described. Note that the description of the same points as in the first embodiment will be omitted as appropriate.

  In the first embodiment, the outdoor weighting rate is calculated based on the number of green blocks and the variance value (S107: outdoor weighting rate calculation processing), but the evaluation value distributions of the green scenes under the mercury lamp and outdoors are similar. It has been found that green fogging may occur as a result of approaching outdoor white balance when subjected to outdoor weighting under a mercury lamp.

  Therefore, it is preferable to further suppress the calculated outdoor weighting rate based on the brightness information. Hereinafter, the processing will be described with reference to a processing flowchart shown in FIG.

  First, a series of processing from RGB integrated value acquisition processing (S201) to outdoor weighting factor calculation processing (S207) is performed in the same manner as in the first embodiment (S101 to S107).

  Next, in the present embodiment, the outdoor weighting rate is suppressed using the outdoor weighting rate suppression coefficient corresponding to the brightness information (S208: outdoor weighting rate correction process). Specifically, when the brightness is below a predetermined threshold, outdoor weighting is not applied (outdoor weighting rate suppression coefficient = 100), and the suppression coefficient is lowered as the brightness exceeds the predetermined threshold and becomes brighter. Thus, the correction is performed close to the calculated outdoor weighting factor.

  Hereinafter, the outdoor weighting process (S209) and the white balance correction coefficient calculation process (S210) are performed in the same manner as in the first embodiment (S108 to S109).

  As described above, according to the imaging apparatus according to the second embodiment, it is further possible to generate a green fog under a mercury lamp by preventing an outdoor load from being applied when the brightness is equal to or less than a predetermined threshold value. More preferably, it is possible to perform good white balance control without color shift even in an outdoor green scene.

  The white balance control by the imaging apparatus described above can also be executed by a program (imaging program). The present invention is also applied to a recording medium in which the imaging program is recorded so as to be executable by the imaging apparatus.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

1 Sub LCD
2 Release shutter (SW1)
3 Flash unit 4 Mode dial (SW2)
5 Distance measuring unit 6 Remote control light receiving unit 7 Lens unit 8 AFLED
9 Strobe LED
10 LCD Monitor 11 Optical Finder 12 Zoom Button TELE (SW4)
13 Power switch (SW13)
14 Zoom button WIDE (SW3)
15 Self-timer / deletion switch (SW5)
16 Menu switch (SW6)
17 OK switch (SW12)
18 Left / image confirmation switch (SW11)
19 Lower / Macro switch (SW10)
20 Up / Strobe switch (SW7)
21 Right switch (SW8)
22 Display switch (SW9)
23 Memory card throttle 30 ROM
31 Operation unit 32 Motor driver 33 SDRAM
34 Memory card 101 Block dividing means 102 RGB integrating means 103 White balance evaluation value acquiring means 104 Green block determining means 105 Green block variance calculating means 106 White extracting means 107 White balance coefficient calculating means 110 Signal processing IC
111 CPU
112 CCD I / F
113 Resize processing unit 115 Memory controller 116 Display output control unit 117 Compression / decompression unit 118 Media I / F
119 YUV converter 120 F / E
121 CCD
122 CDS
123 AGC
124 A / D converter 125 Timing generator c Black body radiation curve

JP 2008-301279 A JP 2006-174281 A

Claims (7)

An image sensor that converts light incident from the optical system into an electrical signal and outputs the signal as an image signal;
Block dividing means for dividing an image region corresponding to the image sensor into a plurality of blocks;
White balance evaluation value acquisition means for calculating a white balance evaluation value based on the imaging signal for each block;
Green block determination means for determining whether the block is a green block based on the white balance evaluation value;
Green block variance calculating means for calculating a variance value based on the white balance evaluation value for the block determined to be a green block by the green block determining means;
White extraction means for extracting a white block based on the white balance evaluation value and a preset white extraction range;
A white balance correction coefficient calculating means for calculating a white balance correction coefficient based on the dispersion value and a white balance evaluation value of the white block;
An image pickup apparatus that performs white balance control based on the white balance correction coefficient.   The imaging apparatus according to claim 1, wherein the white balance correction coefficient calculation unit brings the white balance correction coefficient closer to a predetermined white balance setting condition as the variance value increases.   2. The white balance correction coefficient calculating means, when the brightness is equal to or higher than a predetermined value, causes the white balance correction coefficient to approach a predetermined white balance setting condition as the variance value increases. Imaging device.   The imaging apparatus according to claim 2, wherein the predetermined white balance setting condition is a white balance setting condition suitable for shooting outdoors on a sunny day. The white balance evaluation value acquisition means calculates the white balance evaluation value by using the average values of RGB for each block according to the following expressions (1) and (2):
G / R = (G average value × 100) / R average value (1)
G / B = (G average value × 100) / B average value (2)
The said green block determination means determines as a green block, when the said G / R and the said G / B exceed the predetermined threshold value set to each, The green block is characterized by the above-mentioned. Imaging device. An imaging method in an imaging apparatus including an imaging element that converts light incident from an optical system into an electrical signal and outputs the electrical signal,
Block division processing for dividing an image region corresponding to the image sensor into a plurality of blocks;
A white balance evaluation value acquisition process for calculating a white balance evaluation value based on the imaging signal for each block;
A green block determination process for determining whether the block is a green block based on the white balance evaluation value;
Green block variance calculation processing for calculating a variance value based on the white balance evaluation value for a block determined to be a green block by the green block determination processing;
A white extraction process for extracting a white block based on the white balance evaluation value and a preset white extraction range;
A white balance correction coefficient calculation process for calculating a white balance correction coefficient based on the dispersion value and the white balance evaluation value of the white block;
An imaging method comprising: performing white balance processing based on the white balance correction coefficient. In an imaging device provided with an imaging device that converts light incident from an optical system into an electrical signal and outputs it as an imaging signal,
Block division processing for dividing an image region corresponding to the image sensor into a plurality of blocks;
A white balance evaluation value acquisition process for calculating a white balance evaluation value based on the imaging signal for each block;
A green block determination process for determining whether the block is a green block based on the white balance evaluation value;
Green block variance calculation processing for calculating a variance value based on the white balance evaluation value for a block determined to be a green block by the green block determination processing;
A white extraction process for extracting a white block based on the white balance evaluation value and a preset white extraction range;
A white balance correction coefficient calculation process for calculating a white balance correction coefficient based on the dispersion value and the white balance evaluation value of the white block;
An imaging program that executes white balance processing based on the white balance correction coefficient.