Source: http://www.google.com/patents/US20020101516?ie=ISO-8859-1
Timestamp: 2014-07-28 06:49:20
Document Index: 159164905

Matched Legal Cases: ['art 10', 'art 13', 'art 14', 'art 10', 'art 10', 'art 10', 'art 10', 'art 13', 'art 13', 'art 10', 'art 13', 'art 14', 'art 10', 'art 14', 'art 14', 'art 13', 'application No. 2001']

Patent US20020101516 - White balance control apparatus and method, and image pickup apparatus - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsA white balance control apparatus includes an evaluation value calculation circuit calculating and outputting evaluation values of color components of each of a plurality of regions of digital image data, a luminance conversion part converting the evaluation values of each of the regions into a luminance...http://www.google.com/patents/US20020101516?utm_source=gb-gplus-sharePatent US20020101516 - White balance control apparatus and method, and image pickup apparatusAdvanced Patent SearchPublication numberUS20020101516 A1Publication typeApplicationApplication numberUS 10/055,964Publication dateAug 1, 2002Filing dateJan 28, 2002Priority dateJan 31, 2001Also published asUS7030913Publication number055964, 10055964, US 2002/0101516 A1, US 2002/101516 A1, US 20020101516 A1, US 20020101516A1, US 2002101516 A1, US 2002101516A1, US-A1-20020101516, US-A1-2002101516, US2002/0101516A1, US2002/101516A1, US20020101516 A1, US20020101516A1, US2002101516 A1, US2002101516A1InventorsJunichi IkedaOriginal AssigneeJunichi IkedaExport CitationBiBTeX, EndNote, RefManReferenced by (13), Classifications (7), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetWhite balance control apparatus and method, and image pickup apparatusUS 20020101516 A1Abstract A white balance control apparatus includes an evaluation value calculation circuit calculating and outputting evaluation values of color components of each of a plurality of regions of digital image data, a luminance conversion part converting the evaluation values of each of the regions into a luminance value, and a high-luminance weighting part converting the evaluation values of each of the regions into a base white balance control amount, calculating a non-weighted white balance control amount from the base white balance control amount and a weighted white balance control amount by performing weighting processing on the base white balance control amount by using the luminance value of each of the regions so that a region of higher luminance has a greater weight, and calculating a white balance control amount to be applied to the image data at a time of image recording by using the weighted and non-weighted white balance control amounts. Images(6) Claims(27)
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0027] A description will be given, with reference to the accompanying drawings, of the configuration and operation of a white balance control apparatus of the present invention. [0028]FIG. 2 is a block diagram showing a digital camera including an embodiment of the white balance control apparatus of the present invention. [0029] The digital camera includes a lens barrel 1, an image pickup element 2, an analog-to-digital (A/D) converter 3, an RGB separation circuit 4, a gain adjustment circuit 5 for white balance, a signal processing circuit 6, a gamma (λ) correction circuit 7, and an image output apparatus 8. [0030] The lens barrel 1 is composed of an optical lens, an aperture, and a mechanical shutter, which are driven in accordance with respective control signals supplied from outside so as to adjust the focal length and an amount of exposure. [0031] The image pickup element 2, which is composed of a color CCD and a correlated double sampling circuit (CDS), receives light traveling through the lens barrel 1 and converts the received light into an electrical signal with reduced noise. [0032] The A/D converter 3 converts the electrical signal supplied from the image pickup element 2 into a digital image signal. [0033] The RGB separation circuit 4 separates the digital image signal by color component in accordance with an arrangement of the color filters of the CCD. In this embodiment, three color components of red (R), green (G), and blue (B) are used as the color filters of the CCD. That is, the RGB separation circuit 4 separates the digital image signal into the three color components of R, G, and B. [0034] The gain adjustment circuit 5 adjusts white balance by increasing or decreasing the magnitude of the image signals of the R and B components by digital calculation in accordance with R-gain and B-gain control signals input from outside. [0035] The signal processing circuit 6, if the CCD of the image pickup element 2 is of a single-plate type, performs color interpolation to supplement a lack of color information with the color signals of neighboring pixels and calculates full color data of a recorded image size, and further performs aperture correction to emphasize the outline of an image blurred by the interpolation. [0036] The gamma correction circuit 7 performs λ correction of a gradation characteristic matching a display device. [0037] The image output apparatus 8 is composed of an image display device or a memory recording image data. The light reflected from an object is subjected to the above-described operations and is finally output to the image output apparatus 8 as image data formatted to be viewed, for instance, as a photograph. [0038] The digital camera further includes an evaluation value calculation circuit 9, a control part 10, an adjustment memory 11, a parameter setting part 13, and a high-luminance weighting part 14, which form the image pickup control system of the digital camera. [0039] The evaluation value calculation-circuit 9 divides the image data separated in accordance with the R, G, and B filters in the RGB separation circuit 4 into a plurality of fine regions on a screen as shown in FIG. 3. Then, the evaluation value calculation-circuit 9 calculates the R, G, and B summation values of each region and outputs the summation values as evaluation values for white balance control. In FIG. 3, the screen is divided into 8�16 regions so that 128 (=8�16) summation values are output for each of R, G, and B, that is, 384 evaluation values are output in total. [0040] The RGB separation circuit 4, the gain adjustment circuit 5, the signal processing circuit 6, the gamma correction circuit 7, and the evaluation value calculation circuit 9 form a digital signal processing block 12 indicated by a dotted-line rectangle in FIG. 2. The digital signal processing block 12, which is a part that performs repetitive high-speed digital calculations, preferably has its circuit formed of a special LSI of logic circuits. [0041] Processing inside the digital signal processing block 12 is synchronized and controlled in accordance with a timing control signal input from outside. [0042] The control part 10 controls the entire digital camera and calculates an amount of image pickup control of white balance. In capturing an image, the control part 10 outputs the drive control signals to the lens, the aperture, and the mechanical shutter in the lens barrel 1, the timing control signal for synchronizing image data transfer therewith to the digital signal processing block 12, and the R-gain and B-gain control signals as gain adjustment values of white balance to the gain adjustment circuit 5. Further, the control part 10 outputs an image display control signal or an image recording control signal to the image output apparatus 8. [0043] The adjustment memory 11 retains a variety of adjustment data. The control part 10 refers to the data in the adjustment memory 11 and uses the data for processing such as white balance control. [0044] The parameter setting part 13 is used by a digital camera operator to set a weight parameter of white balance to a desired value depending on the condition of an object. A simple potentiometer or a changeover switch can be employed as the parameter setting part 13. The control part 10 reads out from the adjustment memory 11 a parameter for calculation corresponding to the value of the weight parameter set by the parameter setting part 13, and performs white balance weighting as described later. [0045] The high-luminance weighting part 14, based on an instruction from the control part 10, temporarily converts the evaluation values of the color components of each region of the divided screen, which evaluation values have been output from the evaluation value calculation circuit 9, into base amounts of white balance control (base white balance control amounts). Further, based on values (luminance values) obtained by also converting the evaluation values of given regions into luminance, the high-luminance weighting part 14 performs (high-luminance) weighting or weighting processing so that a region is assigned a greater weight as its luminance becomes higher, and as a result of weighting, the region obtains weighted (weighting-processed) white balance control amounts. Then, the high-luminance weighting part 14 calculates white balance control amounts applied to image data at the time of image recording from both weighted white balance control amounts and non-weighted white balance control amounts, which are obtained by averaging each of the white balance control amounts. Here, the luminance value of each region may be calculated in the evaluation value calculation circuit 9. [0046] A description will be given, with reference to the flowchart of FIG. 4, of a white balance adjustment operation in the digital camera of FIG. 2. [0047] First, in step S1, preliminary exposure control is performed to generate evaluation values for white balance calculation. [0048] In step S2, the evaluation values of image data obtained as a result of the exposure are calculated by the evaluation value calculation circuit 9 and are read. [0049] In step S3, an r-gain and a b-gain, which are white balance control amounts, are calculated for each region of the image data based on the read evaluation values thereof. Processing in a case where an R or B summation value is zero is performed in this step. [0050] Next, in step S4, the evaluation values of each region calculated in the evaluation value calculation circuit 9 are converted into a luminance value Y in accordance with the following equation: Y=0.3*R summation value+0.6*G summation value+0.1*B summation value [0051] That is, 8�16=128 luminance values Y are obtained in total from as many regions. [0052] In step S5, white detection is performed on all the regions of the image data by determining whether the calculated r-gains and b-gains are included in a color region along the blackbody radiation characteristic curve. [0053] The white detection of white balance is performed in the following manner, for instance. First, only regions along the blackbody radiation characteristic curve with color temperatures that appear white to human eyes are selected based on the color information of the screen output from the evaluation value calculation circuit 9. Then, an amount of color shift in the present condition of white balance control is calculated from the evaluation values of colors of each selected region. [0054] The output of the evaluation value calculation circuit 9 is the R, G, and B summation values. Unless the R or B summation value is zero, these summation values of the 128 (=8�16) regions are converted into as many r-gain and b-gain values in accordance with the following equations: r-gain=G summation value/R summation value b-gain=G summation value/B summation value [0055] The obtained r-gain and b-gain values are placed in corresponding positions on an r-gain-b-gain coordinate plane as shown in FIG. 5. If at least one of the R and B summation values of a region is zero, obviously, it is inappropriate to use data on the region for white balance control. Therefore, the data on the region is excluded from the calculation and the region is treated as nonexistent. [0056] On the other hand, a hatched region in FIG. 5 shows the region of the color temperatures that appear white to human eyes along the blackbody radiation characteristic curve on the r-gain-b-gain coordinate plane. Determination as to whether a region of the image data is white is accomplished by determining whether a position determined by the r-gain and b-gain of the region is included in the hatched region on the r-gain-b-gain coordinate plane. That is, in FIG. 5, a region corresponding to a coordinate position (indicated by a black circle) included in the hatched region is determined to be white. [0057] For instance, if a region has an R summation value of 5, a G summation value of 10, and a B summation value of 20, the r-gain and b-gain of the region are given as follows: r-gain=10/5=2.0 b-gain=10/20=0.5 [0058] When R and B input signals (the R and B summation values) are multiplied by these calculation results as white balance gain coefficients, an output R summation value R_out and an output B summation value B out on the output side are given as follows: R � out=R summation value�r-gain=5�2.0=10.0 B � out=B summation value�b-gain=20�0.5=10.0 [0059] Thus, the region is corrected to an achromatic color of R summation value=G summation value=B summation value=10, that is, R:G:B=1:1:1. [0060] In step S6, the sums of the r-gains and the b-gains of regions determined to be white in step S5 (white regions) are calculated. [0061] In step S7, the sum of the luminance values Y of the-white regions is calculated. [0062] In step S8, the sum of values obtained by multiplying the r-gain values of the white regions by the corresponding luminance values Y (or the sum of (r-gain * Y)s) and the sum of values obtained by multiplying the b-gain values of the white regions by the corresponding luminance values Y (or the sum of (b-gain * Y)s) are calculated by using the r-gain and b-gain values of each region calculated in step S3 and the luminance value of each region calculated in step S4. [0063] In step S9, an R-gain_Auto and a B-gain_Auto, which are average values of the r-gains and the b-gains of the white regions without high-luminance weighting processing, are calculated from the sums of the r-gains and b-gains of the white regions obtained in step S6 and the number of the white regions determined in step S5. [0064] In step S10, an R-gain_hi and a B-gain_hi, which are weighted amounts of white balance control by high-luminance weighting processing, are calculated by using the sums of the (r-gain * Y) values and the (b-gain * Y) values of the white regions calculated in step S8, and the sum of the luminance values Y of the white regions calculated in step S7. [0065] An example calculation of the R-gain_Auto, the B-gain_Auto, the R-gain_hi, and the B-gain_hi is given below. [0066] Suppose that the white regions are a region x and a region y, and that the region x has an R summation value R_x of 10, a G summation value G_x of 20, and a B summation value B_x of 40 and the region y has an R summation value R_y of 10, a G summation value G_y of 40, and a B summation value B_y of 50, the r-gain and the b-gain of each of the regions x and y are given as follows: [0067] Region x: r-gain � x=G � x/R � x=20/10=2.0 b-gain � x=G � x/B � x=20/40=0.5 [0068] Region y: r-gain � y=G � y/R � y=40/10=4.0 b-gain � y=G � y/B � y=40/50=0.8 [0069] Since the R-gain_Auto and the B-gain_Auto, which are white balance control amounts without high-luminance weighting, or non-weighted white balance control amounts, are the average values of the r-gain values and the b-gain values of the regions x and y, the R-gain_Auto and the B-gain_Auto are given as follows: R-gain � Auto=(r-gain � x+r-gain � y)/number of white regions=(2.0+4.0)/2=3.0 B-gain � Auto=(b-gain � x+b-gain � y)/number of white regions=(0.5+0.8)/2=0.65 [0070] The luminance value Y of each of the regions x and y is given as follows: [0071] Region x: Y � x=0.3*R � x+0.6*G � x+0.1*B � x=0.3*10+0.6*20+0.1*40=19 [0072] Region y: Y � y=0.3*R � y+0.6*G � y+0.1*B � y=0.3*10+0.6*40+0.1*50=32 [0073] Next, the R-gain_hi and the B-gain_hi, which are values obtained by dividing the sums of the (r-gain * Y)s and the (b-gain * Y)s of the regions x and y by the sum of the luminance values Y of the regions x and y, are given as follows: R-gain � hi=(r-gain � x*Y � x+r-gain � y* Y � y)/(Y � x+Y � y)=(2.0*19+4.0*32)/(19+32)=3.25 B-gain � hi=(b-gain � x*Y � x+b-gain � y* Y � y)/(Y � x+Y � y)=(0.5*19+0.8*32)/(19+32)=0.69 [0074] Next, in step S11, a weight parameter for calculation corresponding to a parameter set to a desired value in the parameter setting part 13 is read out from the adjustment memory 11. [0075] In step S12, an R-gain and a B-gain, which are white balance control amounts used finally at the time of image recording, are obtained by calculating, using the weight parameter read in step S11, the weighted average of the R-gain_Auto calculated in step S9 and the R-gain_hi calculated in step S10 and the weighted average of the B-gain_Auto calculated in step S9 and the B-gain_hi calculated in step S10. [0076] In this weighted average obtaining processing, letting the weight parameter read out from the adjustment memory 11 be any value k between one and ten, the R-gain and B-gain for recording are calculated by the following equations: R-gain=(R-gain � Auto*k+R-gain � hi*(10 −k))/10 B-gain=(B-gain � Auto*k+B-gain =13 hi*(10 −k))/10 [0077] Here, if the value k of the weight parameter is 5, that is, if the ratio of the weight of the high-luminance weighting result (the R-gain_hi and Bgain_hi) to the weight of the result without high-luminance weighting (the R-gain_Auto and B-gain_Auto) is 5:5=1:1, the R-gain and the B-gain are given as follows: R-gain=(R-gain � Auto*k+R-gain � hi*(10 −k))/10=(3.0*5+3.25*(10−5))/10=3.125 B-gain=(B-gain � Auto*k+B-gain � hi*(10 −k))/10=(0.65*5+0.69*(10−5))/10=0.67 [0078] In step S13, white balance control is performed by using the R-gain and the B-gain obtained as a result of the above-described calculation as the final amounts of white balance control for image recording. [0079] In step S14, an image subjected to this white balance control is output. [0080] As a variation of the above-described embodiment, the white balance control apparatus of the present invention may be configured so that white balance control-is performed by simply performing high-luminance weighting processing on each region. [0081] In this case, the white determination processing of step S5 of FIG. 4 is unnecessary, and the following steps to be performed on the white regions are performed on all the regions. This case is equal in the other points to the above-described case of the embodiment, and accordingly, a description thereof will be omitted. [0082] The following effects may be produced by the above-described configuration of the present invention. [0083] Influence of an error caused by the color components of an object of low luminance, which color components show proximity to a white light source on a screen, can be reduced by (a) dividing an image into a plurality of regions, (b) calculating white balance control amounts for each region, and (c) performing weighting processing so that the weight of the white balance control amounts of a region becomes greater as its luminance becomes higher. [0084] With respect to each high-luminance region, both of the weighted and non-weighted amounts of white balance control can be used, and the ratio of the former to the latter can be adjusted by a parameter that can be set to any value. Therefore, in the case of capturing an image of a special object whose high-luminance regions on the screen are not white, high-luminance weighting processing can be performed to have its effects properly adjusted in magnitude. [0085] White balance control with reduced errors can be realized by not only depending on the fact that a high-luminance region has a higher probability of being white but also regarding a region close to the characteristic of blackbody radiation as a white region. [0086] As described above, according to the present invention, errors caused when a screen simultaneously includes a white or an achromatic-colored object and an object of chromatic color having color components along the blackbody radiation characteristic curve, such as a flesh color, can be reduced by taking advantage of the fact that a region of higher luminance on a screen statistically has a higher probability of being included in a white or achromatic-colored object. [0087] The present invention is not limited to the specifically disclosed embodiment, but variations and modifications may be made without departing from the scope of the present invention. [0088] The present application is based on Japanese priority application No. 2001-024636 filed on Jan. 31, 2001, the entire contents of which are hereby incorporated by reference. Referenced byCiting PatentFiling datePublication dateApplicantTitleUS7126644 *Jul 7, 2003Oct 24, 2006Destiny Technology CorporationRapid white balance method for color digital imagesUS7355611 *Nov 26, 2002Apr 8, 2008Hewlett-Packard Development Company, L.P.Method and arrangement for improving image quality on a display of an imaging deviceUS7486819 *Dec 23, 2003Feb 3, 2009Aptina Imaging CorporationSampling images for color balance informationUS7551208 *Oct 11, 2005Jun 23, 2009Hoya CorporationDevice for adjusting white balance based on a selected part field of a displayed imageUS7746386 *Oct 1, 2004Jun 29, 2010Sony CorporationImage pickup device and methodUS8036427 *May 18, 2006Oct 11, 2011Honda Motor Co., Ltd.Vehicle and road sign recognition deviceUS8049789 *Dec 15, 2006Nov 1, 2011ON Semiconductor Trading, LtdWhite balance correction using illuminant estimationUS8144212 *Jul 30, 2009Mar 27, 2012Olympus CorporationWhite balance adjustment apparatus and white balance coefficient calculation methodUS8164649Mar 14, 2008Apr 24, 2012Nikon CorporationWhite balance adjusting device, imaging apparatus, and recording medium storing white balance adjusting programUS20100033595 *Jul 30, 2009Feb 11, 2010Olympus CorporationWhite balance adjustment apparatus and white balance coefficient calculation methodUS20130242130 *Jul 17, 2012Sep 19, 2013Altek CorporationWhite Balance Method and Apparatus ThereofEP1887521A1 *May 18, 2006Feb 13, 2008HONDA MOTOR CO., Ltd.Vehicle and road sign recognition deviceWO2007027516A1 *Aug 25, 2006Mar 8, 2007Micron Technology IncImproved chrominance filter for white balance statistics* Cited by examinerClassifications U.S. Classification348/223.1, 348/E09.052, 348/655International ClassificationH04N9/04, H04N9/73Cooperative ClassificationH04N9/735European ClassificationH04N9/73BLegal EventsDateCodeEventDescriptionOct 10, 2013FPAYFee paymentYear of fee payment: 8Sep 16, 2009FPAYFee paymentYear of fee payment: 4Jan 28, 2002ASAssignmentOwner name: RICOH COMPANY, LTD., JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:IKEDA, JUNICHI;REEL/FRAME:012523/0490Effective date: 20020110RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google