JP2006345359A - Electronic camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic camera capable of more effectively preventing the appearance of a boundary line of images. <P>SOLUTION: A CCD imager 14 has an imaging face having a plurality of partial imaging areas formed therein and channels CH1 and CH2 corresponding to the plurality of partial imaging areas respectively. A gain difference between two partial images output from channels CH1 and CH2 is suppressed by LUTs 28r, 28g, and 28b. Two partial images having the suppressed gain difference are coupled together by a memory control circuit 38. A CPU 30 detects the gain difference between two partial images subjected to suppression processing, with respect to a low luminance range and subjects the detected gain difference to interpolating operation processing to correct low luminance set values of the LUTs 28r, 28g, and 28b. The CPU 30 detects respective gains of two partial images subjected to suppression processing, with respect to a high luminance range and subjects the detected gains to extrapolating operation processing to correct high luminance set values of LUTs 28r, 28g, and 28b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electronic camera, and more particularly, to an electronic camera that creates a single image by combining a plurality of partial images generated in a plurality of imaging regions.

An example of a conventional electronic camera of this type is disclosed in Patent Document 1. According to this prior art, the image sensor has a right channel and a left channel. Image information generated in the right region of the imaging surface is output from the right channel, and image information generated in the left region of the imaging surface is output from the left channel. The output image information is subjected to black level correction processing for each channel, and gain correction processing is performed so as to eliminate the gain difference between channels. In particular, the gain correction value is determined by paying attention to several pixels straddling the boundary between the right region and the left region. Thereby, it is possible to prevent the boundary line between the right region and the left region from appearing in the reproduced image.
JP 2002-252808 A [H04N 5/335, 5/16, G06T 1/00, H01L 27/148]

  However, in the prior art, when determining the gain correction value, changes in luminance and color in one frame of interest are not taken into consideration. For this reason, if an edge appears around the boundary between the right region and the left region, the gain correction value may deviate from the optimum value, and the appearance of the boundary line may not be effectively prevented.

  Therefore, a main object of the present invention is to provide an electronic camera that can more effectively prevent the appearance of image boundary lines.

  An electronic camera (10) according to the invention of claim 1 includes an imaging means (14) having an imaging surface on which a plurality of partial imaging regions are formed and a plurality of output paths respectively corresponding to the plurality of partial imaging regions, and a plurality of outputs. Suppressing means (28r, 28g, 28b) for suppressing a gain difference between a plurality of partial images respectively output from the path, and a combining means (38 for combining a plurality of partial images having a gain difference suppressed by the suppressing means with each other ), First detection means (60, 62, 64, S43, S65, S87) for detecting the gain difference between the plurality of partial images subjected to the suppression processing by the suppression means for the first brightness range, the first detection First correction means (S21) for performing interpolation calculation processing on the gain difference detected by the means to correct the operating characteristic of the suppression means for the first brightness range, and for a plurality of partial images subjected to the suppression processing by the suppression means. Each gain for the second brightness range The second detection means (S27, S31, S51, S55, S73, S77) to be output and the gain detected by the second detection means are subjected to extrapolation calculation processing, and the operating characteristics of the suppression means are set for the second brightness range. Second correcting means for correcting (S29, S33, S35, S41, S53, S57, S59, S63, S75, S79, S81, S85) is provided.

  The imaging means has an imaging surface on which a plurality of partial imaging areas are formed, and a plurality of output paths respectively corresponding to the plurality of partial imaging areas. The gain difference between the plurality of partial images respectively output from the plurality of output paths is suppressed by the suppression unit. A plurality of partial images having suppressed gain differences are combined with each other by the combining means.

  The first detection unit detects a gain difference between the plurality of partial images subjected to the suppression process by the suppression unit for the first brightness range. The first correction unit performs an interpolation calculation process on the gain difference detected by the first detection unit, and corrects the operation characteristic of the suppression unit for the first brightness range.

  On the other hand, a 2nd detection means detects the gain of each of the some partial image to which the suppression process is performed by the suppression means about the 2nd brightness range. The second correction unit corrects the operating characteristic of the suppression unit for the second brightness range by performing extrapolation calculation processing on the gain detected by the second detection unit.

  As described above, if the focused brightness range is the first brightness range, a gain difference between the plurality of partial images is detected. If the focused brightness range is the second brightness range, the plurality of partial images are detected. Each gain is detected. In addition, the operation characteristic of the suppression unit relating to the first brightness range is corrected by an interpolation calculation process for the detected gain difference, and the operation characteristic of the suppression unit relating to the second brightness range is corrected by an extrapolation calculation process for the detected gain. Is done.

  That is, in the first aspect of the invention, taking into consideration that the variation mode of the gain is different between the first brightness range and the second brightness range, the detection target (gain difference, gain) and the correction method (interpolation calculation process, The extrapolation calculation process is made different between the first brightness range and the second brightness range. Thereby, the appearance of the boundary line of the image can be more effectively prevented.

  An electronic camera according to a second aspect of the invention is dependent on the first aspect, wherein the second correction means specifies a relational expression indicating a change in gain with respect to the amount of incident light for each of the plurality of partial images (S29, S33, S53, S57, S75, S79) and extrapolation of the difference between the gain defined by one of the plurality of relational expressions specified by the specifying means and the gain specified by the other one of the plurality of relational expressions Gain difference detection means (S35, S59, S81) for detecting by processing is included.

  The electronic camera according to the invention of claim 3 is dependent on claim 2, and the specifying means specifies the relational expression using the least square method.

  An electronic camera according to a fourth aspect of the invention is dependent on any one of the first to third aspects, and is a discriminating unit that discriminates whether or not a plurality of partial images subjected to suppression processing by the suppression unit satisfy a flatness condition. (S23, S47, S69), and each of the first detection means and the second detection means performs a detection operation when the determination result of the determination means is affirmative. By paying attention to the gain when the flatness condition is satisfied, the operation characteristic of the suppressing means can be accurately corrected.

  An electronic camera according to a fifth aspect of the present invention is dependent on any one of the first to fourth aspects, wherein the plurality of partial images have color information of a plurality of colors, and the suppression means has a plurality of operation characteristics corresponding to the plurality of colors, respectively. Have. As a result, the gain difference between the plurality of partial images is suppressed for each color, and the appearance of the boundary line can be effectively prevented.

  An electronic camera according to a sixth aspect of the invention is dependent on the fifth aspect, and each of the first correction means and the second correction means performs a correction operation for each color of the plurality of partial images.

  The electronic camera according to the invention of claim 7 is dependent on any one of claims 1 to 6, and further comprises extraction means (46) for extracting a plurality of small images respectively forming a plurality of partial images, and the first detection means. Each of the second detection means pays attention to a plurality of small images extracted by the extraction means.

  An electronic camera according to the invention of claim 8 is dependent on claim 7, and the first detection means calculates an average value calculation means (60, 60) for calculating an average value of each component of the plurality of small images extracted by the extraction means. 62, 64), and difference value calculation means (S43, S65, S87) for calculating a difference value between a plurality of average values obtained by the average value calculation means as a gain difference.

  The electronic camera according to the invention of claim 9 is dependent on claim 7 or 8, and the plurality of small images extracted by the extracting means are present in the vicinity of the boundaries of the plurality of partial images.

  An electronic camera according to a tenth aspect of the invention is dependent on any one of the first to ninth aspects, and further includes adjusting means (22a, 22b) for matching the reference levels of the plurality of partial images with each other.

  The electronic camera according to the invention of claim 11 is dependent on claim 10, and the adjusting means performs level adjustment prior to the suppressing operation of the suppressing means.

  The electronic camera according to the invention of claim 12 is dependent on any one of claims 1 to 11, and the first brightness range is a darker range than the second brightness range.

  According to the present invention, the detection target (gain difference, gain) and the correction method (interpolation calculation processing, extrapolation calculation processing) are made different between the first brightness range and the second brightness range. The appearance of the boundary line can be prevented more effectively.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

  Referring to FIG. 1, a digital camera (electronic camera) 10 of this embodiment includes an optical lens 12. The optical image of the object scene is irradiated onto the imaging surface of the CCD imager 14 via the optical lens 12. The imaging surface is covered with a color filter 14f in which R (Red), G (Green), or B (Blue) filter elements are arranged in a Bayer manner.

  Therefore, the charge having R color information is generated by the R pixel, which is a light receiving element covered by the R filter element, and the charge having G color information is G, which is the light receiving element covered by the G filter element. A charge generated in the pixel and having B color information is generated in the B pixel which is a light receiving element covered by the B filter element.

  When a photographing operation is performed by the key input device 32, a TG (Timing Generator) 18 is activated by the CPU 30. The TG 18 generates a plurality of timing signals including a horizontal synchronization signal Hsync and a vertical synchronization signal Vsync. Each of the drivers 16a and 16b drives the CCD imager 14 in response to the timing signal. As a result, a charge corresponding to one frame, that is, a raw image signal is output from the CCD imager 14 every time the vertical synchronization signal Vsync is generated.

  Referring to FIG. 2, the imaging surface of CCD imager 14 has a left imaging area IML and a right imaging area IMR. The left imaging region IML is formed on the left side of the boundary line BL extending in the vertical direction from the center of the imaging surface, and the right imaging region IMR is formed on the right side of the same boundary line BL. That is, the left imaging area IML and the right imaging area IMR are in contact with each other at the boundary line BL.

  A plurality of vertical transfer registers (not shown) are assigned to each of the left imaging area IML and the right imaging area IMR. Further, a horizontal transfer register HL is assigned to the left imaging area IML, and a horizontal transfer register HR is assigned to the right imaging area IMR. Further, an amplifier APL is provided at the output end of the horizontal transfer register HL, and an amplifier APR is provided at the output end of the horizontal transfer register HR.

  Therefore, the charges generated by the plurality of light receiving elements on the left imaging region IML are output from the channel CH1 via the vertical transfer register, the horizontal transfer register HL, and the amplifier APL (not shown). Similarly, the charges generated by the plurality of light receiving elements on the right imaging region IMR are also output from the channel CH2 via a vertical transfer register, a horizontal transfer register HR, and an amplifier APR (not shown).

  That is, the driver 16a performs raster scanning on the left imaging region IML based on the timing signal from the TG 18, and outputs a left half frame raw image signal from the channel CH1. Similarly, the driver 16b performs raster scanning on the right imaging region IMR based on the timing signal from the TG 18, and outputs the raw image signal of the right half frame from the channel CH2.

  However, the transfer direction of the horizontal transfer register HR is opposite to the transfer direction of the horizontal transfer register HL. For this reason, the raster scanning direction is also reversed between the left imaging area IML and the right imaging area IMR.

  The CDS / AGC / AD circuit 20a performs a series of processes of correlated double sampling, automatic gain adjustment, and A / D conversion on the raw image signal of the channel CH1. Similarly, the CDS / AGC / AD circuit 20b performs a series of processes of correlated double sampling, automatic gain adjustment, and A / D conversion on the raw image signal of the channel CH2. Note that the CDS / AGC / AD circuits 20a and 20b also perform the above-described processing in synchronization with the timing signal output from the TG 18.

  The clamp circuit 22 a matches the reference level of the raw image data output from the CDS / AGC / AD circuit 20 a with the black level set by the level adjustment circuit 24. Similarly, the clamp circuit 22 b adjusts the reference level of the raw image data output from the CDS / AGC / AD circuit 20 b to the black level set by the level adjustment circuit 24.

  The raw image data output from the clamp circuit 22 a is written into the SDRAM 36 by the memory control circuit 38. The raw image data output from the clamp circuit 22b undergoes R component gain adjustment by a LUT (Look Up Table) 28r, G component gain adjustment by the LUT 28g, and B component gain adjustment by the LUT 28b, and then the memory control circuit 38. Is written in the SDRAM 36.

  As shown in FIG. 3, the SDRAM 36 includes a raw image area 36a, a YUV image area 36b, and a compressed image area 36c. The memory control circuit 38 stores the raw image data of the channel CH1 on the left side of the raw image region 36a, and stores the raw image data of the channel CH2 on the right side of the raw image region 36a. The raw image data stored in the raw image area 36a in this way represents a captured one-field scene image. Further, the gain adjustment by the LUTs 28r, 28g, and 28b eliminates the gain difference of the raw image data between the channels CH1 and CH2, and prevents the appearance of the boundary line.

  The raw image data output from each of the clamp circuits 22a and 22b is represented by 12 bits. Therefore, each of the LUTs 28r, 28g, and 28b has 4096 set values.

  The post-processing circuit 40 reads out such raw image data from the SDRAM 36 through the memory control circuit 38, performs processing such as color separation and YUV conversion on the read raw image data, and performs memory control on the YUV format image data. The YUV image area 36b is written through the circuit 38. The JPEG codec 42 reads the image data stored in the YUV image area 36b through the memory control circuit 38, performs JPEG compression on the read image data, and passes the compressed image data to the compressed image area 36c through the memory control circuit 38. Write. Such a compression operation is executed every time the vertical synchronization signal Vsync is generated.

  The CPU 30 reads the compressed image data stored in the compressed image area 36 c through the memory control circuit 38 and records the read compressed image data on the recording medium 46 through the I / F 44. Thus, a moving image file containing a plurality of frames of compressed image data is formed on the recording medium 46.

  Referring to FIG. 4, when the R component, G component, and B component of the raw image data of channel CH1 input to clamp circuit 22a draw curves C1rin, C1gin, and C1bin with respect to the incident light amount, respectively, from clamp circuit 22a The R component, G component, and B component of the output raw image data of the channel CH1 draw curves C1rout, C1gout, and C1bout with respect to the incident light amount, respectively. Further, when the R component, G component, and B component of the raw image data of the channel CH2 input to the clamp circuit 22b draw curves C2rin, C2gin, and C2bin with respect to the incident light amount, the channel CH2 output from the clamp circuit 22b. The R component, G component, and B component of the raw image data of FIG.

  Due to the difference in amplification characteristics of the amplifiers APL and APR, the black level and gain of the raw image data also differ between the channels CH1 and CH2. Of these, the black level shift is eliminated by the clamp circuits 22 a and 22 b and the level adjustment circuit 24.

  According to FIG. 4, a plurality of level ranges LV1 to LV10 are assigned to the dynamic range of the raw image data. Among these, the level areas LV1 to LV4 form a low luminance range (first brightness range), and the level areas LV5 to LV10 form a high luminance range (second brightness range).

  The gain shift between the channels CH1 and CH2 is eliminated in the following manner. The raw image data output from the clamp circuit 22a is applied to the block arithmetic circuit 26a, and the raw image data output from the clamp circuit 22b is applied to the block arithmetic circuit 26b. Referring to FIG. 5, the block arithmetic circuit 26 a performs, for each small image belonging to each of the boundary blocks B <b> 1 </ b> L, B <b> 2 </ b> L,. And an average value for each color of the image level. For the small images belonging to each of the boundary blocks B1R, B2R,... BnR assigned to the right imaging region IMR so as to be close to the boundary line BL, the block arithmetic circuit 26b determines the integration value and image level of the high-frequency component for each color. Find the average value for each color.

  Specifically, each of the block arithmetic circuits 26a and 26b is configured as shown in FIG. The raw image data output from the clamp circuit 22a or 22b is given to the block extraction circuit 46. The block extraction circuit 46 extracts raw image data belonging to each of the boundary blocks B1L to BnL or each of the boundary blocks B1R to BnR.

  The R difference value calculation circuit 48 calculates an R difference value that is a difference value between adjacent R pixels in the extracted raw image data. The G difference value calculation circuit 50 calculates a G difference value that is a difference value between adjacent G pixels in the extracted raw image data. A B difference value that is a difference value between adjacent B pixels in the extracted raw image data is calculated.

  The integration circuit 54 integrates the absolute value of the calculated R difference value for each boundary block, the integration circuit 56 integrates the absolute value of the calculated G difference value for each boundary block, and the integration circuit 58 is calculated. The absolute value of the B difference value is integrated for each boundary block. Thereby, integrated values Rh, Gh and Bh corresponding to the same boundary block are output from the integrating circuits 54, 56 and 58, respectively.

  The R average value calculating circuit 60 averages the R pixel levels in the raw image data from the block extracting circuit 46 for each boundary block, and the G average value calculating circuit 62 is included in the raw image data from the block extracting circuit 46. The level of the G pixel is averaged for each boundary block, and the B average value calculation circuit 64 averages the level of the B pixel in the raw image data from the block extraction circuit 46 for each boundary block. As a result, average values Rav, Gav, and Bav corresponding to the same boundary block are output from the R average value calculation circuit 60, the G average value calculation circuit 62, and the B average value calculation circuit 64, respectively.

  Returning to FIG. 1, each of the block arithmetic circuits 26 a and 26 b gives the integrated values Rh, Gh, Bh and average values Rav, Gav, Bav thus calculated to the CPU 30. First, the CPU 30 determines whether or not the small images of the two boundary blocks BKL and BKR (K: 1 to n) adjacent to each other are flat.

  If the integrated value Rh obtained in each of the two boundary blocks of interest is less than the threshold value TH, it is determined that the R component of the small image belonging to these boundary blocks is flat. If the integrated value Gh obtained in each of the two boundary blocks of interest is less than the threshold value TH, it is determined that the G component of the small image belonging to these boundary blocks is flat. If the integrated value Bh obtained in each of the two boundary blocks of interest is less than the threshold value TH, it is determined that the B component of the small image belonging to these boundary blocks is flat.

  The CPU 30 compares the integrated value Rh obtained by the boundary block BKR out of the two boundary blocks determined to have the R component flat, and compares the threshold value THr with the two boundary blocks determined to have the G component flat. The integral value Gh obtained by the boundary block BKR is compared with the threshold value THg, and the integral value Bh obtained by the boundary block BKR among the two boundary blocks determined to have a flat B component is compared with the threshold value THb. Compare. Note that the threshold values THr, THg, and THb indicate the maximum values in the low luminance range shown in FIG.

  When the integral value Rh is lower than the threshold value THr, the image reproduced by the R component is determined to be dark, and when the integral value Rh is equal to or greater than the threshold value THr, the image reproduced by the R component is determined to be bright. Similarly, when the integral value Gh is lower than the threshold value THg, the image reproduced by the G component is determined to be dark, and when the integral value Gh is equal to or greater than the threshold value THg, the image reproduced by the G component is determined to be bright. Further, when the integral value Bh is less than the threshold value THb, the image reproduced by the B component is determined to be dark, and when the integral value Bh is equal to or greater than the threshold value THb, the image reproduced by the B component is determined to be bright.

  When it is determined that the image based on the R component is dark, the CPU 30 calculates the difference value ΔRav based on the two average values Rav obtained from the two boundary blocks of interest. When it is determined that the image based on the G component is dark, the CPU 30 calculates the difference value ΔGav based on the two average values Gav respectively obtained from the two boundary blocks of interest. Further, when it is determined that the image based on the B component is dark, the CPU 30 calculates the difference value ΔBav based on the two average values Bav respectively obtained from the two boundary blocks of interest.

  The difference value ΔRav is obtained by subtracting the average value Rav of the boundary block BKR from the average value Rav of the boundary block BKL, and the difference value ΔGav is obtained by subtracting the average value Gav of the boundary block BKR from the average value Gav of the boundary block BKL. The difference value ΔBav is obtained by subtracting the average value Bav of the boundary block BKR from the average value Bav of the boundary block BKL.

  The difference values ΔRav, ΔGav, ΔBav obtained in this way and the average values Rav, Gav, Bav obtained from the boundary book BKR are written in the low luminance register 34a shown in FIG. According to FIG. 7, five columns are assigned to each of the level areas LV1 to LV4. Each of the average values Rav, Gav, and Bav is written in the level area column to which the average value belongs in order from the smallest numerical value. The difference values ΔRav, ΔGav, ΔBav are assigned to the associated average values Rav, Gav, Bav, respectively.

  For example, when the average values Rav, Gav, and Bav of the boundary block BKR belong to the level areas LV3, LV4, and LV1, respectively, the average value Rav and the difference value ΔRav related thereto are stored in the level area LV3 column of the low luminance register 34a. The average value Gav and the difference value ΔGav related thereto are written to the column of the level area LV4 of the low luminance register 34a, and the average value Bav and the difference value ΔBav related thereto are the levels of the low luminance register 34a. It is written in the field LV1.

  When all the columns of the low luminance register 34a are filled with numerical values, the low luminance register 34a is completed. The CPU 30 interpolates 20 difference values ΔRav written in the low brightness register 34a to create low brightness R correction data, and interpolates 20 difference values ΔGav written in the low brightness register 34a. To generate G correction data for low luminance, and perform interpolation calculation on the 20 difference values ΔBav written in the low luminance register 34a to generate B correction data for low luminance.

  The R, G, and B components of the raw image data of the channel CH1 output from the clamp circuit 22a draw the curves C1rout, C1gout, and C1bout shown in FIG. 4, and the raw image data of the channel CH2 output from the clamp circuit 22b When the curves C2rout, C2gout and C2bout shown in FIG. 4 are drawn, the low luminance R correction data, the low luminance G correction data and the low luminance B correction data draw the curves Cr, Cg and Cb shown in FIG. 8, respectively.

  Each of the curves Cr, Cb, and Cg shows how the difference image data obtained by subtracting the raw image data of the channel CH2 from the raw image data of the channel CH1 changes with respect to the raw image data of the channel CH2. Equal to the characteristic curve shown.

  The CPU 30 adds the value of the low-luminance R correction data to the low-luminance default setting value of the LUT 28r, adds the value of the low-luminance G correction data to the low-luminance default setting value of the LUT 28g, and low-luminance B correction data Is added to the low brightness default setting value of the LUT 28b.

  When it is determined that the image based on the R component is bright, the CPU 30 writes two average values Rav respectively obtained from the two boundary blocks of interest into the high luminance register 34b. Similarly, when it is determined that the image based on the G component is bright, the CPU 30 writes two average values Gav respectively obtained from the two boundary blocks of interest into the high luminance register 34b. Further, when it is determined that the image based on the B component is bright, the CPU 30 writes the two average values Bav respectively obtained from the two boundary blocks of interest into the high luminance register 34b.

  The average values Rav, Gav or Bav of the boundary blocks belonging to the left imaging area IML are written in the left area column of the high brightness register 34b shown in FIG. 9, and the average values Rav, Gav or of the boundary blocks belonging to the right imaging area IMR are written. Bav is written in the right area column of the high luminance register 34b. The high luminance register 34b has a ring buffer function, and the write destinations of the average values Rav, Gav and Bav are updated cyclically.

  Subsequently, the CPU 30 performs an arithmetic operation according to the least square method on each of the average values Rav, Gav and Bav set in the left area column of the high brightness register 34b, thereby obtaining an R gain characteristic, G in the raw image data of the channel CH1. Three linear functions F1r, F1g, and F1b that respectively indicate the gain characteristic and the B gain characteristic are specified.

  The CPU 30 also performs an operation according to the least square method on each of the average values Rav, Gav, and Bav set in the right area column of the high luminance register 34b, thereby obtaining an R gain characteristic and a G gain in the raw image data of the channel CH2. Three linear functions F2r, F2g, and F2b respectively indicating the characteristics and the B gain characteristics are specified.

  For example, when each of the R pixel level, the G pixel level, and the B pixel level changes as shown in FIG. 10A in the horizontal direction of the left imaging region IML, the linear functions F1r, F1g, or F1b are the same as in FIG. Draw a straight line shown in A). Further, when each of the R pixel level, the G pixel level, and the B pixel level is changed as shown in FIG. 10B in the horizontal direction of the right imaging region IMR, the linear functions F2r, F2g, or F2b are the same as those in FIG. Draw a straight line as shown in B).

  The CPU 30 has a plurality of R gains, a plurality of G gains, and a plurality of G values belonging to the high luminance range of the raw image data that will be obtained when a series of processing in the channel CH1 is performed on the charges generated in the right imaging region IMR. B gain is estimated by extrapolation according to the linear functions F1r, F1g and F1b. The CPU 30 also estimates a plurality of R gains, a plurality of G gains, and a plurality of B gains belonging to the high luminance range of the raw image data of the channel CH1 by extrapolation calculation according to the linear function F2r, F2g, or F2b. The R pixel, the G pixel, and the B pixel having the gain thus estimated are distributed as shown in FIG. 10C in the horizontal direction of the right imaging region IMR.

  Thereafter, the CPU 30 subtracts a plurality of R gains based on the linear function F2r from a plurality of R gains based on the linear function F1r to create high-luminance R correction data represented by a plurality of R gain differences. The CPU 30 also subtracts a plurality of G gains based on the primary function F2g from a plurality of G gains based on the linear function F1g to create high-luminance G correction data represented by a plurality of G gain differences. Further, the CPU 30 subtracts a plurality of B gains based on the primary function F2b from a plurality of B gains based on the linear function F1b to create B correction data for high luminance formed by a plurality of B gain differences. The created high luminance R correction data, high luminance G correction data, and high luminance B correction data span the high luminance range shown in FIG.

  The CPU 30 adds the value of the high luminance R correction data to the high luminance default setting value of the LUT 28r, adds the value of the high luminance G correction data to the high luminance default setting value of the LUT 28g, and then adds the high luminance B correction data. Is added to the high brightness default setting value of the LUT 28b.

  When the default setting value of the LUT 28r, the default setting value of the LUT 28g, and the default setting value of the LUT 28b draw the curves TSr, TSg and TSb shown in FIG. 11 with respect to the output of the clamp circuit 22b, respectively, When the low luminance G correction data, the low luminance B correction data, the high luminance R correction data, the high luminance G correction data, and the high luminance B correction data are added, the setting value of the LUT 28r, the setting value of the LUT 28g, and The set values of the LUT 28b draw curves TMr, TMg and TMb shown in FIG. As a result, the gains of the raw image data are substantially the same between the channels CH1 and CH2.

  When adjusting the set values of the LUTs 28r, 28g, and 28b, the CPU 30 executes processing according to the flowcharts shown in FIGS. A control program corresponding to this flowchart is stored in the flash memory 48.

  First, in steps S1 and S3, the high luminance register 34b and the low luminance register 34a are cleared, and in step S5, the variable K is set to "0". In step S7, it is determined whether or not the vertical synchronization signal Vsync is generated. If YES, the variable K is incremented in step S9. In step S11, it is determined whether or not the variable K exceeds a predetermined value n. If “NO” here, the process proceeds to a step S11, and if “YES”, the process proceeds to the step S17.

  In step S13, the integrated values Rh, Gh, Bh and average values Rav, Gav, Bav of the boundary block BKL are fetched from the block arithmetic circuit 26a. In step S15, the integrated values Rh, Gh, Bh and average values Rav, Gav of the boundary block BKR are acquired. , Bav are fetched from the block arithmetic circuit 26b.

  In step S23, it is determined whether or not the two integrated values Rh that have been taken in satisfy the flatness condition. Specifically, it is determined whether or not both of the two integrated values Rh that have been taken are less than the threshold value TH. If this flatness condition is not satisfied, it is assumed that at least one of the small image reproduced by the R component belonging to the boundary block BKL and the small image reproduced by the R component belonging to the boundary block BKR is not a flat image, step S47. Proceed to On the other hand, if this condition is satisfied, the small image reproduced by the R component belonging to each of the boundary blocks BKL and BKR is regarded as a flat image, and the process proceeds to step S25.

  In step S25, it is determined whether or not the average value Rav of the boundary block BKR exceeds a threshold value THr. If “NO” here, the process proceeds to a step S43 to subtract the average value Rav of the boundary block BKR from the average value Rav of the boundary block BKL. Thereby, the difference value ΔRav is obtained. In step S45, the calculated difference value ΔRav and the average value Rav of the boundary block BKR are written in the low luminance register 34a shown in FIG. When the writing is completed, the process proceeds to step S47.

  If “YES” in the step S25, the process proceeds to a step S27, and the average value Rav of the boundary block BKL is written in the left area column of the high luminance register 34b shown in FIG. In step S29, a calculation according to the least square method is performed on the plurality of average values Rav written in the left area column of the high luminance register 34b, and a linear function F1r indicating the R gain characteristics of the raw image data of the channel CH1 is obtained. Identify.

  In step S31, the average value Rav of the boundary block BKR is written in the right area column of the high luminance register 34b shown in FIG. In step S33, a calculation according to the least square method is performed on the plurality of average values Rav written in the right area column of the high luminance register 34b, and a linear function F2r indicating the R gain characteristics of the raw image data of the channel CH2 is obtained. Identify.

  In step S35, extrapolation calculation processing based on the two linear functions F1r and F2r thus obtained is executed to create R correction data for high luminance. In step S39, it is determined whether or not the created high-intensity R correction data has changed significantly from the previously created high-intensity R correction data. When the fluctuation amount is large, the process proceeds to step S41, and the created high luminance R correction data is added to the high luminance default setting value of the LUT 28r. When the process of step S41 is completed, the process proceeds to step S47. If NO is determined in step S39, the process proceeds to step S47 as it is.

  Note that it is impossible to specify the linear function F1r in the first step S29, and it is impossible to specify the primary function F2r in the first step S33. For this reason, in this embodiment, NO is forcibly determined in the first step S39.

  Steps S47 to S67 are the same as steps S23 to S45 described above except that attention is paid to the G component instead of the R component. The processes in steps S69 to S89 shown in FIG. 14 are the same as steps S23 to S45 described above except that attention is paid to the B component instead of the R component. Therefore, duplicate description is omitted.

  In step S53, the linear function F1g indicating the R gain characteristic of the raw image data of the channel CH1 is specified, and in step S57, the linear function F2g indicating the R gain characteristic of the raw image data of the channel CH2 is specified. When NO is determined in step S47 or S61, or when the process of step S63 or S67 is completed, the process proceeds to step S69.

  In step S75, the linear function F1b indicating the R gain characteristic of the raw image data of the channel CH1 is specified, and in step S79, the linear function F2b indicating the R gain characteristic of the raw image data of the channel CH2 is specified. When NO is determined in step S69 or S83, or when the process of step S85 or S89 is completed, the process returns to step S9.

  Returning to FIG. 10, if “YES” in the step S11, it is determined whether or not the low luminance register 34a is completed in a step S17. The low luminance register 34a is completed when numerical values are written in all the columns. If NO is determined here, the process returns to step S7. If YES is determined, the process proceeds to step S19.

  In step S19, low luminance R correction data is created by interpolation calculation of the difference value ΔRav set in the low luminance register 34a, and low luminance G is calculated by interpolation of the difference value ΔGav set in the low luminance register 34a. Correction data is created, and low-luminance B correction data is created by interpolation calculation of the difference value ΔBav set in the low-luminance register 34a.

  In step S21, the created low brightness R correction data is added to the low brightness default setting value of the LUT 28r, and the created low brightness G correction data is added to the low brightness default setting value of the LUT 28g. The B correction data for low luminance is added to the low luminance default setting value of the LUT 28b. When the process of step S21 is completed, the process returns to step S1.

  The extrapolation calculation process in step S35 is executed according to a subroutine shown in FIG. In step S351, a plurality of R gains that belong to the high luminance range of the raw image data that will be obtained when a series of processing in the channel CH1 is performed on the charge generated in the right imaging region IMR follows the linear function F1r. Estimated by extrapolation. In step S353, a plurality of R gains belonging to the high luminance range of the raw image data of channel CH1 are estimated by extrapolation according to the linear function F2r. In step S355, the R correction data for high luminance is calculated by subtracting the plurality of R gains obtained in step S353 from the plurality of R gains obtained in step S351. When the process of step S355 is completed, the process returns to the upper-level routine.

  The extrapolation calculation process of step S59 shown in FIG. 14 is executed according to the subroutine shown in FIG. 17, and the extrapolation calculation process of step S81 shown in FIG. 15 is executed according to the subroutine shown in FIG. However, the processing in steps S591 to S595 shown in FIG. 17 is the same as the processing in steps S351 to S355 shown in FIG. 16 except that attention is paid to the G component instead of the R component. 18 is the same as the process of steps S351 to S355 shown in FIG. 16 except that the process pays attention to the B component instead of the R component. Therefore, duplicate description is omitted.

  As can be seen from the above description, the CCD imager 14 has an imaging surface on which the left imaging area IML and the right imaging area IMR are formed, and channels CH1 and CH2 corresponding to the left imaging area IML and the right imaging area IMR, respectively. . The gain difference between the two partial images output from the channels CH1 and CH2 is suppressed by the LUTs 28r, 28g, and 28b. Two partial images with suppressed gain differences are combined with each other by the memory control circuit 38.

  The CPU 30 detects the gain difference between the two partial images to be subjected to the suppression process for the low luminance range (S43, S65, S87), performs the interpolation calculation process on the detected gain difference, and performs the LUTs 28r, 28g, and 28b. The low brightness setting value is corrected (S21).

  The CPU 30 also detects the gain of each of the two partial images subjected to the suppression process for the high luminance range (S27, S31, S51, S55, S73, S77), and performs extrapolation calculation processing on the detected gain. Thus, the high brightness setting values of the LUTs 28r, 28g and 28b are corrected (S29, S33, S35, S41, S53, S57, S59, S63, S75, S79, S81, S85).

  As described above, if the focused luminance range is the low luminance range, the gain difference between the two partial images is detected, and if the focused luminance range is the high luminance range, the gains of the two partial images are detected. The In addition, the operation characteristics of the LUTs 28r, 28g, and 28b related to the low luminance range are corrected by interpolation calculation processing for the detected gain difference, and the operation characteristics of the LUTs 28r, 28g, and 28b related to the high luminance range are extrapolated to the detected gain. It is corrected by arithmetic processing.

  That is, in this embodiment, taking into account that the variation mode of the gain differs between the low luminance range and the high luminance range, the detection target (gain difference, gain) and the correction method (interpolation calculation processing, extrapolation calculation processing) are set. The low luminance range and the high luminance range are made different. Thereby, the appearance of the boundary line of the image can be more effectively prevented.

  In this embodiment, the clamp process is performed prior to the gain adjustment process by the LUTs 28r, 28g, and 28b. However, the clamp process may be executed after the gain adjustment process. In this embodiment, the number of partial imaging areas formed on the imaging surface is two, but the number of partial imaging areas may be three or more.

It is a block diagram which shows the structure of one Example of this invention. It is an illustration figure which shows an example of a structure of the image sensor applied to FIG. 1 Example. It is an illustration figure which shows an example of the mapping state of SDRAM applied to FIG. 1 Example. It is a graph which shows a part of operation | movement of the clamp circuit applied to FIG. 1 Example. It is an illustration figure which shows a part of operation | movement of FIG. 1 Example. It is a block diagram which shows an example of a structure of the block arithmetic circuit applied to the FIG. 1 Example. FIG. 3 is an illustrative view showing one example of a configuration of a low luminance register applied to the embodiment in FIG. 1; It is a graph which shows another part of operation | movement of FIG. 1 Example. FIG. 3 is an illustrative view showing one example of a configuration of a high luminance register applied to the embodiment in FIG. 1; (A) is an illustration figure which shows a part of operation | movement when performing the calculation according to the least squares method to the high-intensity image corresponding to the left side imaging area, (B) is minimum 2 to the high-intensity image corresponding to the right side imaging area. It is an illustration figure which shows a part of operation | movement when performing the calculation according to a multiplication, (C) is an illustration figure which shows a part of operation | movement when performing an extrapolation calculation about the right side imaging region. It is a graph which shows a part of other operation | movement of FIG. 1 Example. It is a flowchart which shows a part of operation | movement of CPU applied to the FIG. 1 Example. It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 1 Example. It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 1 Example. FIG. 12 is a flowchart showing yet another portion of behavior of the CPU applied to the embodiment in FIG. 1. It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 1 Example. It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 1 Example. FIG. 12 is a flowchart showing yet another portion of behavior of the CPU applied to the embodiment in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Digital camera 14 ... Image sensor 22a, 22b ... Clamp circuit 26a, 26b ... Block arithmetic circuit 28r, 28g, 28b ... LUT
30 ... CPU
34a: low luminance register 34b: high luminance register

Claims (12)

An imaging means having an imaging surface on which a plurality of partial imaging areas are formed and a plurality of output paths respectively corresponding to the plurality of partial imaging areas;
Suppression means for suppressing a gain difference between the plurality of partial images respectively output from the plurality of output paths;
Combining means for combining a plurality of partial images having gain differences suppressed by the suppressing means;
First detection means for detecting a gain difference between a plurality of partial images subjected to suppression processing by the suppression means for a first brightness range;
First correction means for performing interpolation calculation processing on the gain difference detected by the first detection means to correct the operating characteristic of the suppression means for the first brightness range;
Second detection means for detecting a gain of each of the plurality of partial images subjected to suppression processing by the suppression means for a second brightness range; and extrapolation calculation processing is performed on the gain detected by the second detection means. An electronic camera comprising second correction means for correcting the operating characteristic of the suppression means for the second brightness range.   The second correction unit is defined by a specifying unit that specifies a relational expression indicating a gain change with respect to an incident light amount for each of the plurality of partial images, and one of a plurality of relational expressions specified by the specifying unit. The electronic camera according to claim 1, further comprising: a gain difference detection unit that detects a difference between a gain and a gain defined by another one of the plurality of relational expressions by the extrapolation calculation process.   The electronic camera according to claim 2, wherein the specifying unit specifies the relational expression using a least square method. A discriminating unit for discriminating whether or not the plurality of partial images subjected to the suppression process by the suppression unit satisfy a flatness condition;
4. The electronic camera according to claim 1, wherein each of the first detection unit and the second detection unit performs a detection operation when a determination result of the determination unit is positive. The plurality of partial images have color information of a plurality of colors,
The electronic camera according to claim 1, wherein the suppression unit has a plurality of operating characteristics corresponding to the plurality of colors.   6. The electronic camera according to claim 5, wherein each of the first correction unit and the second correction unit performs a correction operation for each color of the plurality of partial images. An extraction means for extracting a plurality of small images that respectively form the plurality of partial images;
The electronic camera according to claim 1, wherein each of the first detection unit and the second detection unit focuses on a plurality of small images extracted by the extraction unit.   The first detecting means includes an average value calculating means for calculating an average value of each component of the plurality of small images extracted by the extracting means, and a plurality of average values obtained by the average value calculating means. The electronic camera according to claim 7, further comprising difference value calculation means for calculating a difference value as the gain difference.   The electronic camera according to claim 7 or 8, wherein the plurality of small images extracted by the extraction unit are present in the vicinity of boundaries of the plurality of partial images.   The electronic camera according to claim 1, further comprising an adjusting unit that matches reference levels of the plurality of partial images with each other.   The electronic camera according to claim 10, wherein the adjustment unit performs level adjustment prior to the suppression operation of the suppression unit.   The electronic camera according to claim 1, wherein the first brightness range is a darker range than the second brightness range.

Images