JP2008283364A - Imaging apparatus, and white balance correcting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of efficiently reducing color tone irregularity on a specific position in an image, which occurs correspondingly to a photographing distance, and to provide a white balance correcting method in the imaging apparatus. <P>SOLUTION: About image data obtained by photography wherein a white LED light source 117 is emitted, an in-face irregularity correction value for correcting color tone irregularity generated on a specific position is previously calculated for every photographing distance and stored in a flash ROM 103. In the case of white balance correction, white balance correction is applied to the image data obtained by the photography wherein the white LED light source 117 is emitted by correcting a white balance correction value about a block in which the in-face correction value is set, and about a block in which the in-face correction value is not set, white balance correction is applied to the image data without correcting the white balance correction value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging device including an LED that projects white light and a white balance correction method in such an imaging device, and in particular, imaging capable of reducing color unevenness in an image when white light is projected. The present invention relates to an apparatus and a white balance correction method in such an imaging apparatus.

  Generally, a flash light emitting device using a xenon tube (hereinafter referred to as a flash device) is used for photographing in a dark place. The light emitted from the flash device using the xenon tube is flash light emission for a very short time. Therefore, in close-up photography, there is a problem that the light emission amount control cannot catch up and the light emission amount increases, and the whole becomes whitish (this phenomenon is called overexposure). In view of such a background, in recent years, a camera having a flash device using a white light emitting diode (hereinafter, white LED) has been developed.

  By using the white LED, it is possible to continuously project flash light, and it has become possible to shoot at an appropriate brightness by an automatic exposure function (hereinafter referred to as AE) at the time of close-up shooting. As a proposal regarding correction of color in an image obtained by photographing using such a white LED, for example, in Patent Document 1, white balance (hereinafter referred to as a white balance) according to the color temperature of light actually emitted from a flash device is described. WB)) and correction information for reducing the variation of each white LED that constitutes each flash device for each product to calculate more accurate white balance correction information. A method for absorbing individual differences in color has been proposed.

Further, in Patent Document 2, WB correction information for white LEDs at a reference distance is provided, and WB correction information corresponding to a distance to a subject (hereinafter referred to as a shooting distance) is estimated based on the WB correction information at the reference distance. Thus, a technique for absorbing a difference in color for each shooting distance has been proposed.
JP 2004-228723 A JP 2006-108970 A

  Here, a general white LED is roughly divided into a combination of a red, blue, and green color LED to obtain white light, a blue light emitting LED, and a fluorescent light for converting the wavelength of the blue light from the blue LED. There are two types, one that obtains white light by combining with the body. In particular, with respect to a white LED that obtains white light using a blue LED and a phosphor, flash photography is performed due to the arrangement of a plurality of blue LED elements constituting the white LED and the light emission ratio of each blue LED element. In such a case, color unevenness (hereinafter referred to as in-plane unevenness) occurs at a specific position in the image corresponding to the shooting distance.

  Since both Patent Documents 1 and 2 are not countermeasures for in-plane unevenness in an image for each LED element constituting a white LED, even if in-plane unevenness in the image as described above occurs, the influence thereof is affected. It cannot be corrected.

  The present invention has been made in view of the above circumstances, and an imaging apparatus capable of efficiently reducing unevenness in color at a specific position in an image, which occurs in response to a shooting distance, and the imaging apparatus An object of the present invention is to provide a white balance correction method in such an imaging apparatus.

  In order to achieve the above object, an imaging device according to a first aspect of the present invention is an imaging device including an LED that projects white light, and an imaging unit that obtains an imaging signal by imaging using the LED. The correction information includes the generation position of the color unevenness in the image generated from the imaging signal for each shooting distance and the correction value for correcting the white balance correction value for performing the white balance correction of the image at the generation position. As a storage unit, a distance measuring unit for obtaining a shooting distance at the time of shooting, and correction information corresponding to the obtained shooting distance is read from the storage unit, and the white correction value is corrected using the correction information. And a white balance correction unit that performs white balance correction of the image using the corrected white balance correction value.

  In order to achieve the above object, the white balance correction method according to the second aspect of the present invention is a white balance correction that performs white balance correction of an image obtained by an imaging device including an LED that projects white light. A method of obtaining an imaging signal by photographing with the LED emitting light, obtaining a photographing distance at the time of photographing, and occurrence position of uneven coloring in an image generated from the imaging signal for each photographing distance And a correction value for correcting the white balance correction value for correcting the white balance of the image at the generation position are calculated and stored in the storage unit, and the correction information corresponding to the shooting distance is stored in the storage unit. The white balance correction value is corrected using the correction information, and the white of the image is corrected using the corrected white balance correction value. And performing Balance correction.

  It is possible to provide an imaging apparatus capable of efficiently reducing unevenness in color at a specific position in an image, which occurs in accordance with the shooting distance, and a white balance correction method in such an imaging apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the configuration of an internal circuit of a digital camera as an example of the imaging apparatus of the present embodiment will be described. FIG. 1 is a block diagram showing an internal configuration of the digital camera according to the present embodiment. A digital camera shown in FIG. 1 includes a microcomputer 101, an operation unit 102, a flash memory 103, a lens 104, an image sensor 105, a CDS / AGC circuit 106, an A / D conversion circuit 107, and a bus 108. SDRAM 109, image signal processing circuit 110, JPEG processing unit 111, memory interface (I / F) 112, recording medium 113, LCD driver 114, LCD 115, LED light emitting circuit 116, and white LED light source 117. And is configured.

  The microcomputer 101 comprehensively controls various sequences of the digital camera. An operation unit 102 and a flash memory 103 are connected to the microcomputer 101. The operation unit 102 is an operation member such as a power button, a release button, and various input keys. When the operation unit 102 is operated by the user, the microcomputer 101 executes various sequences according to the operation of the operation unit 102. The flash memory 103 has a function as a storage unit that stores various parameters such as correction information used in white balance correction and various information for obtaining the correction information. The microcomputer 101 reads parameters necessary for various sequences from the flash memory 103 and issues instructions to each unit in FIG.

  The lens 104 is configured to include an optical system for condensing an optical image from a subject (not shown) so as to be incident on the image sensor 105, and a diaphragm for adjusting the amount of light incident on the image sensor 105. ing. Each part of the lens 104 is driven by an aperture driving mechanism and a lens driving mechanism (not shown) according to instructions from the microcomputer 101.

  The image sensor 105 having the function of the image capturing unit is an image sensor in which a Bayer array color filter is disposed in front of a photodiode constituting a pixel, and the light collected by the lens 104 is converted into each pixel. Light is received by a constituent photodiode and subjected to photoelectric conversion, whereby the amount of light is output to the CDS / AGC circuit 106 as a charge amount. Here, in the Bayer array, lines in which R pixels and G pixels are alternately arranged in the horizontal direction and lines in which G pixels and B pixels are alternately arranged in the horizontal direction are alternately arranged in the vertical direction. This is a pixel array. Note that the image sensor 105 may be a CMOS method or a CCD method.

  A CDS (correlated double sampling) / AGC (auto gain control) circuit 106 performs waveform shaping on an electric signal (analog image signal) read from the image sensor 105 while reducing reset noise and the like, and further performs image shaping. Gain is increased so that the brightness becomes the target brightness. The A / D conversion circuit 107 converts the analog imaging signal preprocessed by the CDS / AGC circuit 106 into a digital imaging signal (hereinafter referred to as RAW image data).

  A bus 108 is a transfer path for transferring various data generated inside the digital camera to each unit in the camera. The microcomputer 101, the A / D conversion circuit 107, the SDRAM 109, the image signal processing circuit 110, The JPEG processing unit 111, the memory I / F 112, and the LCD driver 114 are connected. The image data obtained by the A / D conversion circuit 107 is temporarily stored in the SDRAM 109 via the bus 108. The SDRAM 109 temporarily stores various data such as RAW image data obtained by the A / D conversion circuit 107 and image data processed by the image signal processing circuit 110 and the JPEG processing unit 111.

  The image signal processing circuit 110 reads out RAW image data stored in the SDRAM 109 and performs image processing. The image signal processing circuit 110 includes a white balance (WB) correction circuit 110a, a synchronization circuit 110b, a color conversion circuit 110c, a gamma conversion circuit 110d, and an automatic focusing (AF) processing circuit 110e. Yes.

  The WB correction circuit 110a having a function as a white balance correction unit is a white instruction designated by the microcomputer 101 having a function as a correction unit for R data and B data in the RAW image data read from the SDRAM 109. White balance correction is performed by multiplying the balance correction value. The synchronization circuit 110b generates image data having the three colors R, G, and B as one pixel component from the image data output from the WB correction circuit 110a. The color conversion circuit 110c corrects the color of the image data by performing a linear conversion by multiplying the image data output from the synchronization circuit 110b by the color matrix specified by the microcomputer 101, and also instructs the image data from the microcomputer 101. The color of the image is changed by calculation using the saturation and hue coefficients. The gamma conversion circuit 110d performs gamma conversion (gradation conversion) processing on the image data output from the color conversion circuit 110c, and corrects the gradation of the image data so as to be suitable for display and printing.

  The AF processing circuit 110e having a function as a distance measuring unit generates a luminance signal for each predetermined area of the image data stored in the SDRAM 109, and accumulates the luminance signals generated for each predetermined area to obtain an AF evaluation value. The obtained AF evaluation value is sent to the microcomputer 101. The microcomputer 101 performs AF adjustment of the lens 104 based on the AF evaluation value obtained by the AF processing circuit 110e. The AF processing circuit 110e also obtains the distance (shooting distance) from the position of the lens 104 at the time of focusing to the subject at the time of shooting.

  Image data that has been subjected to image processing in the gamma conversion circuit 110d of the image signal processing circuit 110 is stored in the SDRAM 109 again.

  The JPEG processing unit 111 reads out image data that has been subjected to image processing from the SDRAM 109, and performs compression according to the JPEG method or the like. The JPEG processing unit 111 also has a function of reading JPEG compressed image data recorded on the recording medium 113 and performing expansion processing. The image data compressed by the JPEG processing unit 111 is stored in the SDRAM 109 and then recorded on the recording medium 113 via the memory I / F 112. Here, the recording medium 113 is, for example, a recording medium including a memory card that can be attached to and detached from the digital camera body, but is not particularly limited.

  The LCD driver 114 displays an image on the LCD 115. When displaying the JPEG compressed image data recorded on the recording medium 113, the JPEG processing unit 111 reads out the JPEG compressed image data recorded on the recording medium 113, and after performing decompression processing, Stored in the SDRAM 109. The LCD driver 114 reads the image data from the SDRAM 109, converts it into a video signal, and then displays an image on the LCD 115 based on the video signal.

  The LED light emitting circuit 116 drives each blue LED element constituting the white LED light source 117 to emit light. As shown in FIG. 2, the white LED light source 117 includes a blue LED element 117a that emits blue light, and a phosphor 117b that emits yellow light when the blue light strikes, and the blue light emitted by the blue LED element 117a and White light is irradiated by mixing yellow light emitted from the phosphor 117b. The white LED light source 117 can be used as a flash device, for example.

  Here, at the time of flash photographing using the white LED light source 117 as a flash device, the microcomputer 101 reads the correction information stored in the flash memory 103 based on the photographing distance obtained from the AF processing circuit 110e, The white balance correction value used in white balance correction is corrected, and the corrected white balance correction value is output to the WB correction circuit 110a. Here, the correction information stored in the flash memory 103 is an in-plane unevenness correction value (details will be described later) corresponding to the shooting distance.

  In general, in-plane unevenness of a white LED light source that obtains white light using a blue LED element and a phosphor as shown in FIG. 2 occurs at a specific position in the image corresponding to the shooting distance. In addition, the in-plane unevenness takes a yellowish color (R = G> B) with respect to white color (R = G = B). In this embodiment, in order to correct the in-plane unevenness, the position where the in-plane unevenness is generated and the correction value of the in-plane unevenness at that position are measured in advance for each shooting distance, and are stored in the flash memory 103. Let me.

Hereinafter, a method for calculating the in-plane unevenness correction value as correction information will be described.
The in-plane unevenness correction value is calculated for each divided block obtained by dividing the image into (m × n) blocks. FIG. 3 shows an example in which an image at a certain shooting distance is divided into 10 × 10 blocks. In each block divided in this way, an average value of each component of R, G, B is obtained, and a G / B value (first ratio) is calculated for R, G, B of the obtained average value. To do. Then, the smallest G / B value in all blocks is detected as the reference value G / B_ij. Further, a ratio (second ratio) between the G / B value G / B_mn and the reference value G / B_ij in each block is obtained, and it is determined whether or not the second ratio is equal to or greater than a predetermined threshold value. Thus, when the threshold value is equal to or greater than the predetermined threshold value, the in-plane unevenness correction value for the block is set to the second ratio (G / B_mn) / (G / B_ij). In-plane unevenness of a white LED light source that obtains white light using a blue LED element and a phosphor has a deep color in a narrow range when the shooting distance is short, and a wide range when the shooting distance is long. Tend to have a light color. Therefore, in consideration of the difference in color intensity at each shooting distance, the size of a predetermined threshold value for determining whether or not to set an in-plane unevenness correction value for the block is changed. That is, when the shooting distance is short, the threshold value is changed to a larger threshold value than when the shooting distance is long. As a result, the in-plane unevenness correction value W_mn is set only for a block at a specific position corresponding to the shooting distance, as shown in FIGS. 4 (a) and 4 (b). FIG. 4A shows the in-plane unevenness correction value at a short shooting distance 1 (for example, 10 cm), and FIG. 4B shows the in-plane unevenness correction at a long distance shooting distance 2 (for example, 20 cm). Indicates the value. The in-plane unevenness varies depending on the arrangement of the blue LED elements constituting the white LED, but in FIGS. 4A and 4B, the arrangement of the blue LED elements is the same and only the distance is changed. Is shown. As can be seen from FIG. 4A and FIG. 4B, the threshold value is small in the case of a long-distance shooting distance, so that the number of blocks for which in-plane unevenness correction values are set is short-distance shooting. Increase with distance.

  FIG. 5 is a flowchart showing a flow of correction value calculation processing for in-plane unevenness as correction information. This processing is performed at the time of manufacturing or adjusting the digital camera. Note that the example in FIG. 5 assumes a case where image data is obtained by shooting an achromatic subject (for example, a white or gray chart) while the white LED light source 117 is illuminated.

  First, at the time of adjustment, when the digital camera is installed on an adjusting machine (not shown) and the distance between the digital camera and the subject is set to a certain shooting distance (Dk = D1) (step S501), shooting is performed in that state. (Step S502). By executing the shooting, RAW image data obtained through the image sensor 105, the CDS / AGC circuit 106, and the A / D conversion circuit 107 is stored in the SDRAM 109 (step S503).

  Next, initial values of various parameters used for calculating in-plane unevenness correction values are set by the microcomputer 101 (step S504). Specifically, the parameter i indicating the number of rows of the block serving as a reference for the G / B value is 0, the parameter j indicating the number of columns is 0, and the parameter G / B_min indicating the minimum G / B value is 0. Set to Thereafter, the number of divided blocks (m × n) stored in the flash memory 103 is read by the microcomputer 101, and the number of divided blocks is set (step S505). For example, in the example of FIG. 2, (m × n) = 10 × 10. After the division block number is set, the microcomputer 101 reads out the RAW image data stored in the SDRAM 109 and divides the read out RAW image data into (m × n) blocks (step S506). ). After the RAW image data is divided into (m × n) blocks, an average value of the G component and the B component is calculated for each of the divided blocks, and a G / B value G / is calculated with respect to the calculated average value. B_mn is calculated (step S507).

  After G / B_mn for each block is calculated, an in-plane unevenness correction reference value calculation operation for detecting the reference value G / B_ij of G / B_mn from all blocks is performed. In this in-plane unevenness correction reference value calculation calculation, first, the parameter m indicating the number of rows in the block is set to 1, the parameter n indicating the number of columns is set to 1, and G / B_min is set to G / B_11 (step S508). . Here, in the example of FIG. 2, (m, n) = (1, 1) indicates the upper left block in the screen which is the first row and the first column.

  Next, it is determined whether G / B_mn is larger than G / B_min (step S509). If it is determined in step S509 that G / B_mn is equal to or smaller than G / B_min, i is set to m, j is set to n, and G / B_min is set to G / B_mn (step S510). Since G / B_mn and G / B_min are both G / B_11 for the first time, G / B_mn and G / B_min are equal, and the process of step S510 is always performed. On the other hand, if it is determined in step S509 that G / B_mn is larger than G / B_min, the process in step S510 is not performed.

  Next, it is determined whether n is less than 10 (step S511). If n is less than 10 in the determination in step S511, 1 is added to n (step S512), and then the determination in step S509 is performed again for the block in the next column. On the other hand, if n is 10 in the determination in step S511, it is determined whether or not m is less than 10 assuming that the detection of the minimum value for the block for one row is completed (step S513). . In the determination in step S513, when m is less than 10, 1 is added to m, and after n is set to 1 (step S514), the block of the first column in the next row is set in step S509. The determination is made again. On the other hand, if m is 10 in the determination in step S513, it is determined that the detection of the minimum value for all blocks in the image has been completed, and the next in-plane unevenness correction value calculation process is performed. That is, G / B_min at that time becomes the reference value G / B_ij. The block of the reference value G / B_ij is the block closest to white in the image.

  In the calculation for calculating the in-plane unevenness correction value, the threshold value G / B_TH_Dk corresponding to the shooting distance Dk is first read from the flash memory 103 (step S515). Next, m is set to 1 and n is set to 1 (step S516). Thereafter, the threshold value G / B_TH_Dk corresponding to the shooting distance is compared with the ratio (G / B_mn) / (G / B_ij) between the G / B value G / B_mn and the reference value G / B_ij in each block. It is determined whether or not the ratio (second ratio) exceeds the threshold value (step S517). If it is determined in step S517 that (G / B_mn) / (G / B_ij) exceeds the threshold value, the color of the block is different from the reference block (specifically, the reference The in-plane unevenness correction value W_mn in the block (m, n) is the second ratio calculated in step S517 (G / B_mn) / (G / B_ij). (Step S518). On the other hand, if it is determined in step S517 that (G / B_mn) / (G / B_ij) is less than or equal to the threshold value, the process in step S518 is not performed. In this case, for example, W_mn is set to 0.

  Next, it is determined whether n is less than 10 (step S519). If n is less than 10 in the determination in step S519, 1 is added to n (step S520), and then the determination in step S517 is performed again on the next column block. On the other hand, if n is 10 in the determination in step S519, it is determined whether or not m is less than 10 assuming that the calculation of the in-plane unevenness correction value for the block for one row is completed. Step S521). In the determination in step S521, when m is less than 10, 1 is added to m, and after n is set to 1 (step S522), the block of the first column in the next row is set in step S517. The determination is made again. On the other hand, if it is determined in step S521 that m is 10, the calculation shifts to step S523, assuming that the calculation of in-plane unevenness correction values for all blocks in the image is completed.

  After the calculation of the in-plane unevenness correction value for a certain shooting distance Dk is completed, it is determined whether or not the shooting distance Dk is closer than a predetermined distance De (for example, a value corresponding to the closest distance) (step S523). If it is determined in step S523 that Dk exceeds De, 1 is added to Dk (step S524), and then the processing from step S501 is performed on another shooting distance. In the example of FIG. 5, when 1 is added to Dk, the shooting distance is set to a short distance by one step from the previous shooting distance. In this way, in the example of FIG. 5, the in-plane unevenness correction value is calculated from the far side. Of course, the in-plane unevenness correction value may be calculated from the short distance side.

  Further, in the determination of step S523, when Dk reaches De, calculation of in-plane unevenness correction values corresponding to all shooting distances is completed, and the processing in FIG. 5 ends.

  Next, white balance correction using the in-plane unevenness correction value calculated as shown in FIG. 5 will be described. FIG. 6 is a flowchart showing a flow from the start of photographing to WB correction.

  A through image is displayed before the digital camera starts shooting. In the through image display, the image sensor 105 is continuously operated, and RAW image data obtained through the image sensor 105 by this continuous operation is processed by the image signal processing circuit 110 and then displayed on the LCD 115 sequentially. If the 1st release switch is turned on by the user operating the release button of the operation unit 102 while the through image is being displayed, AE processing and AF processing are performed (step S601). In the AE process, for example, RAW image data obtained via the image sensor 105 during live view display is accumulated for each predetermined area to obtain an AE evaluation value, and the brightness in the screen is evaluated based on the obtained AE evaluation value. This is done by calculating the exposure amount (aperture amount and exposure time) at the time of photographing. The AF process is performed by driving the lens 104 by the microcomputer 101 based on the AF evaluation value obtained by the AF processing circuit 110e. When AF adjustment is performed, a distance (shooting distance) D from the position of the lens 104 at the time of focusing to the subject at the time of shooting is calculated, and this shooting distance D is held in a register or the like (not shown) of the microcomputer 101. .

  Thereafter, when the 2nd release switch is turned on by the user operating the release button of the operation unit 102, a shooting operation is performed (step S602). In the shooting operation, the aperture amount and the exposure time are adjusted so that the imaging device 105 is exposed with the exposure amount calculated by the AE process in step S601, and the imaging operation by the imaging device 105 is performed. Raw image data obtained via the image sensor 105 is stored in the SDRAM 109.

  After the photographing operation, the RAW image data stored in the SDRAM 109 is read by the WB correction circuit 110a of the image signal processing circuit 110 (step S603). Subsequently, the microcomputer 101 determines whether or not the white balance setting is an auto white balance (AWB) mode (step S604). Here, the auto white balance mode is a mode in which a white balance correction value is calculated from image data (RAW image data) obtained at the time of shooting, and white balance correction is performed based on the calculated white balance correction value. In addition to this, as a white balance setting, for example, a white balance correction value for a typical light source is calculated in advance and stored in the flash memory 103, and manual white is performed in which white balance is performed in accordance with the stored white balance correction value. There is a balance (MWB) mode. Such white balance setting can be performed by the photographer operating the operation unit 102.

  If it is determined in step S604 that the white balance setting is set to the auto white balance mode, the microcomputer 101 calculates the white balance correction value Wa for auto white balance from the RAW image data stored in the SDRAM 109. Then, the white balance correction value Wa is set to the white balance correction value W1 that serves as a reference for white balance correction at the time of shooting (step S606). In addition, as a method for calculating the white balance correction value Wa, a conventionally known method can be applied as it is, and therefore, detailed description thereof is omitted here. If the white balance setting is set to the manual white balance mode instead of the auto white balance mode in the determination in step S604, the white balance correction value Wm corresponding to the light source selected by the photographer is microscopic. The computer 101 reads the data from the flash memory 103 (step S607), and the white balance correction value Wm is set to the reference white balance correction value W1 (step S608). The white balance correction value W1 set in step S606 or step S608 is held in a register (not shown) of the microcomputer 101.

  After the white balance correction value W1 is set, the shooting distance D held in a register (not shown) of the microcomputer 101 is read (step S609). Then, the in-plane unevenness correction value corresponding to the read photographing distance D is read from the flash memory 103 (step S610). Next, a corrected white balance correction value calculation process is performed (step S611). In step S611, for the block in which the in-plane unevenness correction value W_mn is set, the white balance correction value W1 corrected by using the in-plane unevenness correction value W_mn is used as the final white balance correction value. Is set. On the other hand, the white balance correction value W1 is set as the final white balance correction value for the blocks for which the in-plane unevenness correction value W_mn is not set. Details of the processing in step S611 will be described later.

  After the correction of the white balance correction value in step S611, the white balance correction value is sent to the WB correction circuit 110a, and the white balance correction is performed in the WB correction circuit 110a (step S612).

  Hereinafter, the corrected white balance correction value calculation process in step S611 in FIG. 6 will be described. FIG. 7 is a flowchart showing the flow of the corrected white balance correction value calculation process.

  In the process of FIG. 7, first, the white balance correction value W1 set in step S606 or step S608 of FIG. 6 is read from the register or the like of the microcomputer 101 (step S701). Subsequently, the block division number (m × n) of the image data stored in the flash memory 103 is read (step S702). Next, m is set to 1 and n is set to 1 (step S703).

  Thereafter, among the in-plane unevenness correction values read out from the flash memory 103, the in-plane unevenness correction value W_mn corresponding to the block (m, n) is read out (step S704). Subsequently, it is determined whether W_mn is set for the block (m, n), that is, whether the read W_mn is not 0 (step S705). If it is determined in step S705 that W_mn is not set, the corrected white balance correction value W_MN is set to W1 (step S706). On the other hand, if it is determined in step S705 that W_mn is set, the corrected white balance correction value W_MN is set to a value obtained by multiplying W1 by W_mn (step S707).

  After step S706 or step S707, it is determined whether n is less than 10 (step S708). If n is less than 10 in the determination in step S708, 1 is added to n (step S710), and then the processing in step S704 and subsequent steps is performed again on the next column block. On the other hand, if n is 10 in the determination in step S708, it is determined whether m is less than 10 on the assumption that the correction of the white balance correction value for the block for one row is completed (step S708). S709). In the determination in step S709, if m is less than 10, 1 is added to m, and after n is set to 1 (step S711), step S704 and subsequent steps are performed for the first column block in the next row. The process is performed again. On the other hand, if m is 10 in the determination in step S709, it is determined that the correction of the white balance correction value for all the blocks in the image has been completed, and the processing in FIG. The white balance correction value finally obtained by such processing is as shown in FIG. Here, FIG. 8 is an example of the corrected white balance correction value when the in-plane unevenness correction value is stored as shown in FIG. As shown in FIG. 8, the correction is performed only on the block in which the in-plane unevenness correction value is set. In step S705, it is determined whether or not the white balance correction value is to be corrected by determining whether or not W_mn is set, but the in-plane unevenness correction value W_mn in the block that is not corrected is set to 1. As described above, the calculation in step S707 may be performed for all blocks.

  As described above, according to the present embodiment, when adjusting the camera or the like, the block in which the image is projected with the white LED light source and the color is most appropriately reproduced in the image obtained by this shooting. Is detected as a reference, and the coefficient for correcting the difference in color of the other blocks with respect to the detected reference block is obtained, so that the arrangement of the plurality of blue LED elements constituting the white LED and the light emission ratio of each blue LED element are determined. As a result, it is possible to efficiently correct unevenness in color that occurs at a specific position corresponding to the shooting distance during flash shooting, and to make the color of the image uniform. Here, the in-plane unevenness caused by the arrangement of the plurality of blue LED elements constituting the white LED and the light emission ratio of each blue LED element is not affected by the light source at the time of shooting, the type of subject, etc. It is not necessary to obtain the in-plane unevenness correction value every time, and can be obtained in advance. For this reason, the processing time for white balance correction at the time of shooting is almost the same as when correction is not performed, and efficient in-plane unevenness correction can be performed.

  In addition, when a blue LED element and a phosphor are used as the white LED, it is not necessary to consider the influence of the R component when calculating the in-plane unevenness correction value. Is simplified.

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention. For example, in the above-described embodiment, the G / B value is calculated when calculating the in-plane unevenness correction value. However, the in-plane unevenness correction value may be calculated by calculating the B / G value. . However, in this case, the reference block is the block with the maximum B / G value, and the relationship of inequality signs in various determinations is also reversed.

  Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some configuration requirements are deleted from all the configuration requirements shown in the embodiment, the above-described problem can be solved, and this configuration requirement is deleted when the above-described effects can be obtained. The configuration can also be extracted as an invention.

It is a block diagram which shows the internal structure of the digital camera which concerns on embodiment of this invention. It is a figure which shows the structural example of a white LED light source. It is a figure showing the example at the time of dividing | segmenting the image data of a Bayer arrangement | sequence obtained with respect to a certain imaging distance into a 10x10 block. It is a figure which shows the example of an in-plane nonuniformity correction value. It is a flowchart shown about the flow of the correction value calculation process of an in-plane nonuniformity. It is the flowchart which showed the flow from imaging | photography start to WB correction | amendment. It is a flowchart shown about the flow of a correction white balance correction value calculation process. It is a figure which shows the example of the white balance correction value after correction | amendment was made.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Microcomputer, 102 ... Operation part, 103 ... Flash memory, 104 ... Lens, 105 ... Imaging device, 106 ... CDS / ADC circuit, 107 ... A / D conversion circuit, 108 ... Bus, 109 ... SDRAM, 110 ... Image Signal processing circuit, 110a ... white balance (WB) correction circuit, 110b ... synchronization circuit, 110c ... color conversion circuit, 110d ... gamma conversion circuit, 110e ... automatic focus (AF) processing circuit correction circuit, 111 ... JPEG processing unit 112 ... Memory interface (I / F), 113 ... Recording medium, 114 ... LCD driver, 115 ... LCD, 116 ... LED light emitting circuit, 117 ... White LED light source

Claims (9)

In an imaging device including an LED that projects white light,
An imaging unit that obtains an imaging signal by photographing with the LED emitting light;
Correction information including the generation position of the unevenness of color in the image generated from the imaging signal for each shooting distance and the correction value for correcting the white balance correction value for correcting the white balance of the image at the generation position A storage unit for storing as,
A distance measuring unit for obtaining a shooting distance at the time of shooting;
A correction unit that reads correction information corresponding to the obtained shooting distance from the storage unit, and corrects the white balance correction value using the correction information;
A white balance correction unit that performs white balance correction of the image using the corrected white balance correction value;
An imaging apparatus comprising:   The imaging apparatus according to claim 1, wherein the correction information is calculated for each block obtained by dividing the image into a plurality of blocks.   The imaging apparatus according to claim 2, wherein the correction information is calculated using a G component and a B component for each block.   The correction information calculates a first ratio that is a ratio of the B component to the G component for each block, and is a ratio between the first ratio for each block and the minimum value of the first ratio. The imaging apparatus according to claim 3, wherein a certain second ratio is calculated and calculated based on the second ratio.   As a result of comparing the second ratio and the threshold value set according to the shooting distance for each block, the correction information indicates the correction value for the block in which the second ratio is larger than the threshold value. The imaging apparatus according to claim 4, wherein the imaging apparatus is set to the second ratio, and the second ratio is calculated by setting the correction value for a block equal to or less than the threshold value to zero.   The imaging apparatus according to claim 5, wherein the correction unit performs the correction only on a block in which the correction value is set to the second ratio.   The image pickup apparatus according to claim 1, wherein the white balance correction value is obtained by calculating from an image pickup signal obtained by the image pickup unit in an auto white balance mode.   The imaging according to claim 1, wherein the white balance correction value is obtained by reading data stored in advance in a storage unit for each specific light source in the manual white balance mode. apparatus. A white balance correction method for correcting white balance of an image obtained by an imaging device including an LED that projects white light,
An imaging signal is obtained by shooting with the LED emitting light,
Get the shooting distance at the time of shooting,
Correction information including a generation position of unevenness of color in the image generated from the imaging signal at each shooting distance and a correction value for correcting a white balance correction value for performing white balance correction of the image at the generation position Is calculated and stored in the storage unit,
Read correction information corresponding to the shooting distance from the storage unit, correct the white balance correction value using the correction information,
The image is subjected to white balance correction using the corrected white balance correction value.
A white balance correction method characterized by the above.

Images