Source: http://www.google.com/patents/US7359573?dq=6,418,462
Timestamp: 2013-12-09 09:48:15
Document Index: 371046612

Matched Legal Cases: ['Application No. 2002', 'art 210', 'art 220', 'art 220', 'art 210', 'art 210']

Patent US7359573 - Contrast compensation apparatus and method thereof - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Advanced Patent Search | Sign inAdvanced Patent SearchPatentsA contrast compensation apparatus and a method thereof utilize a simplified hardware structure and a low contrast distortion. The contrast compensation apparatus includes a pixel value detection unit to detect a distribution of pixel values of respective pixels of an input image signal, a pixel value...http://www.google.com/patents/US7359573?utm_source=gb-gplus-sharePatent US7359573 - Contrast compensation apparatus and method thereofPublication numberUS7359573 B2Publication typeGrantApplication numberUS 10/699,658Publication dateApr 15, 2008Filing dateNov 4, 2003Priority dateNov 7, 2002Fee statusLapsedAlso published asCN1302436C, CN1499441A, DE60320735D1, EP1418543A2, EP1418543A3, EP1418543B1, US20040091169Publication number10699658, 699658, US 7359573 B2, US 7359573B2, US-B2-7359573, US7359573 B2, US7359573B2InventorsYung-Jun Park, Jae-hwan Oh, Hyun Kang, Seung-Joon YangOriginal AssigneeSamsung Electronics Co., Ltd.Patent Citations (26), Non-Patent Citations (1), Referenced by (5), Classifications (17), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetContrast compensation apparatus and method thereofUS 7359573 B2Abstract A contrast compensation apparatus and a method thereof utilize a simplified hardware structure and a low contrast distortion. The contrast compensation apparatus includes a pixel value detection unit to detect a distribution of pixel values of respective pixels of an input image signal, a pixel value limit unit having pre-set luminance limit values and re-configuring the distribution of the pixel values of the respective pixels based on the pre-set luminance limit values, and a mapping unit to set luminance for the respective pixels based on a cumulative distribution function with respect to the re-configured pixel values. When certain portions of an image are rendered very bright or dark, the phenomenon in which the entire image becomes abruptly bright or dark is reduced. Further, the contrast compensation apparatus uses the minimum number of multipliers, adders, and subtractors only, thus having an advantage of simplified structure and using less electric power.
CDF ⁡ ( K ) = CDF ⁡ ( K ) - CDF ⁡ ( N ) N � K + K , wherein N is a highest pixel value displayable when the image signal forms an image, and K denotes a pixel value.
CDF ⁡ ( K ) = CDF ⁡ ( K ) - CDF ⁡ ( N ) N � K + K where N is a highest pixel value displayable when the image signal forms an image, and K denotes a pixel value.
CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of Korean Application No. 2002-68898, filed Nov. 7, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
CDF = ∑ i = 0 n ⁢ ⁢ PDF ⁡ ( i ) ⁢ ⁢ wherein ⁢ ⁢ i = 0 , 1 , 2 , 3 ⁢ ⁢ � Formula ⁢ ⁢ 1 ] The mapping unit 30 tends to map low luminance values of pixels into high luminance values based on a cumulative distribution function obtained by Formula 1 when the overall luminance of an input image is high.
SUMMARY OF THE INVENTION The present invention has been devised to solve the above problem. Thus, an aspect of the present invention is to provide a contrast compensation apparatus having less contrast distortion than conventional hardware and having a simplified hardware structure, and a method thereof.
CDF ⁡ ( K ) = CDF ⁡ ( K ) - CDF ⁡ ( N ) N � K + K , wherein N is the highest pixel value displayable when the image signal forms an image, and K denotes a pixel value.
The BUBO unit 200 contains a first setting value to set over-threshold values (or values over an upper limit value) of the detected luminance value and a second setting value to set under-threshold values (or values under a lower limit value) of the detected luminance value, and maps luminance values over the first setting value or under the second setting value, out of the luminance values detected from the PDF calculation unit 100, into the first setting value or the second setting value. For example, when the first and second setting values are set to a 20-level gray scale and a 200-level gray scale, respectively, for an input image having 256 gray levels (0�255 gray levels), the BUBO unit 200 outputs a 20- to 200-level image as is to the CDF calculation unit 300, whereas the BUBO unit 200 maps the luminance values under 20-level gray scale (for example, 15) into the 20-level gray scale, and luminance values over 200-level gray scale (for example, 210) into the 200-level gray scale, before outputting to the CDF calculation unit 300. By setting the gray scale and luminance values thusly, even though certain image portions have excessively high or low luminance values, the luminance of an entire image may be prevented from being excessively high or low when an image is displayed.
Generally, the first comparison part 210 has a first setting value storage (first storage) 211, a first comparator 212, and a first buffer 213. The first setting value storage (first storage) 211 stores a first setting value, and is enabled when logic �high� is outputted from the first comparator 212. The first comparator 212 compares a luminance value detected from the PDF calculation unit 100 with the first setting value stored in the first setting value storage (first storage) 211. If the detected luminance value does not exceed the first setting value as a result of the comparison, the first comparator 212 outputs logic �low�. Accordingly, the first buffer 213 is enabled so that the detected luminance value is outputted to the second comparison part 220. If the detected luminance value exceeds the first setting value as a result of the comparison, logic �high� is outputted to enable the first setting value storage (first storage) 211, and the first setting value stored in the first setting value storage (first storage) 211 is outputted to the second comparison unit 220.
The second comparison part 220 has a second setting value storage (second storage) 221, a second comparator 222, and a second buffer 223. The second setting value storage (second storage) 221 stores a second setting value, and is enabled when the second comparator 222 outputs logic �high�. The second comparator 222 compares the second setting value with a luminance value outputted from the first comparison part 210. If the applied luminance value is smaller than the second setting value as a result of the comparison, the second comparator 222 outputs logic �low�, and, if the applied luminance value is larger than the second setting value, outputs logic �high�. Accordingly, if an output value of the second comparator 222 is logic �low�, an output value of the first comparison part 210 is outputted from the CDF calculation unit 300, and, if the output value of the second comparator 222 is logic �high�, the second setting value is outputted to the CDF calculation unit 300.
X={1,1,2,2,2,2,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,3,3,3,3,2,2,2,2,1,1} Herein, a lowest value of a luminance signal is �1�, and the highest value is �4�. The luminance values are limited to, for example, 4 kinds for simplicity but, actually, the luminance signal has a 256-level (0�255) luminance.
PDF{1}=4 PDF{2}=8 PDF{3}=8 PDF{4}=13 The above values indicate that the number of pixels having a luminance value of �1� is 4, the number of pixels having a luminance value of �2� is 8, the number of pixels having a luminance value of �3� is 8, and the number of pixels having a luminance value of �4� is 13. Further, when the probability density functions are inputted to the CDF calculation unit 200, the cumulative distribution functions below are obtained.
CDF ⁡ ( K ) = CDF ⁡ ( K ) - CDF ⁡ ( N ) N � K + K Formula ⁢ ⁢ 2 ] Herein, N is the highest luminance value displayable when the image signal forms an image, that is, for the luminance value of N=4, K denotes a luminance value ranging from 1 to 4 in this example.
CDF{1}=(4−33/(4�1))+1=−3.25 CDF{2}=(12−33/(4�2))+2=−2.50 CDF{3}=(20−33/(4�3))+3=−1.75 CDF{4}=(33−33/(4�4))+4=+4.00
Herein, under the assumption that negative numbers (−3.25, −2.50, −1.75) are respectively mapped into a positive number �1�, re-configured cumulative distribution functions (hereinafter, referred to as Look Up Table (LUT)) are as follows:
LUT{1}=1 LUT{2}=1 LUT{3}=1 LUT{4}=4 The cumulative distribution functions re-configured as above are stored in the mapping unit 500 as a look-up table Then, the contrast compensation apparatus maps and outputs luminance values of an image signal according to the reconfigured cumulative distribution functions. For example, if the luminance values of an image signal are 1, 2, and 3, the values are mapped to a luminance value �1� for outputs, and a luminance value �4� is outputted only when the luminance value of an image signal is �4�. Accordingly, when an image signal is converted into an image, the entire image does not become bright even though the image mainly has the high luminance value �4�, which would degrade its contrast ratio.
In the meantime, the implementation of Formula 2 in hardware requires an adder, a subtractor, a multiplier, and a divider, but the barrel shifter 430 is used as the divider in implementing the contrast compensation apparatus, so that the hardware structure is greatly reduced. A shift amount in the barrel shifter 430 is decided based on a displayable maximum luminance value �N�, and, upon general contrast compensation, the value �N� becomes �255�.
Next, an over-threshold value and an under-threshold value are set to remove luminance values such as �0� or �255� that greatly affect the luminance values of an entire image compared to a portion occupied on the image, that is, luminance values rendering the image excessively dark or bright (S200). The over-threshold values and the under-threshold values may be set to 10% from the highest luminance value and 10% from the lowest luminance value, respectively, but such values are not fixed, but vary when an image is rendered dark or bright. Herein, when luminance values of an image signal exceed the upper limit value, the values are mapped to the upper limit value, and, when luminance values of an image signal are smaller than the lower limit value, the luminance values are mapped to the lower limit value (S300). Accordingly, the image luminance does not become dominated by a specific luminance value. Next, probability density functions having luminance limited by the upper limit value and the lower limit value are sequentially added, and a probability distribution function is obtained (S400). Thereafter, the obtained probability distribution function is converted into a gray scale (S500). Last, the luminance of an image signal is mapped based on a gray scale probability distribution function (hereinafter, referred to as LUT) for outputs. The conversion method into a gray scale and the mapping method based on the probability distribution function (LUT) are well-known technologies, so descriptions will be omitted. Accordingly, when certain portions of an image are rendered very bright or dark, the phenomenon in which the entire image becomes bright or dark may be reduced by the upper limit value and the lower limit value.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS5289282May 22, 1992Feb 22, 1994Matsushita Electric Industrial Co., Ltd.Video signal gradation correctorUS5294986May 22, 1992Mar 15, 1994Matsushita Electric Industrial Co., Ltd.Video signal gradation corrector which prevents excessive extension of the dynamic rangeUS5315389Jun 25, 1992May 24, 1994Matsushita Electric Industrial Co., Ltd.Intensity correction device for providing a correction signal for automatically correcting an intensity of a video signalUS5339368 *Nov 21, 1991Aug 16, 1994Unisys CorporationDocument image compression system and methodUS5414538 *Oct 7, 1993May 9, 1995Xerox CorporationImage-dependent exposure enhancementUS5434931Apr 20, 1994Jul 18, 1995Educational Testing ServiceSystem and method for picture image processing employing transformation of picture dataUS5502776Jan 27, 1995Mar 26, 1996Canon Kabushiki KaishaMethod and apparatus selectively setting an image processing conditionUS5808697 *Jun 14, 1996Sep 15, 1998Mitsubishi Denki Kabushiki KaishaVideo contrast enhancerUS5862234 *Nov 12, 1993Jan 19, 1999Todter; ChrisActive noise cancellation systemUS5949918 *Aug 18, 1997Sep 7, 1999Sarnoff CorporationMethod and apparatus for performing image enhancementUS5982926 *Jan 17, 1995Nov 9, 1999At & T Ipm Corp.Real-time image enhancement techniquesUS6130724 *Nov 23, 1998Oct 10, 2000Samsung Electronics Co., Ltd.Image processing apparatus and method for magnifying dynamic rangeUS6259472Jun 17, 1997Jul 10, 2001Samsung Electronics Co., Ltd.Histogram equalization apparatus for contrast enhancement of moving image and method thereforUS6463173Oct 30, 1995Oct 8, 2002Hewlett-Packard CompanySystem and method for histogram-based image contrast enhancementUS6504954 *Feb 5, 1999Jan 7, 2003Raytheon CompanyClosed loop piecewise-linear histogram specification method and apparatusUS6549239 *May 6, 1997Apr 15, 2003CimatrixSmart progressive-scan charge-coupled device cameraUS6658165 *Dec 28, 1999Dec 2, 2003Lg Electronics Inc.Contrast enhancing apparatus for video signalUS7012625 *Mar 27, 2000Mar 14, 2006Fujitsu General LimitedImage quality correcting circuitUS7167597 *Oct 15, 2002Jan 23, 2007Ricoh Company, Ltd.Image processing apparatus, image processing method, computer program and storage mediumUS20020136464 *Nov 13, 2001Sep 26, 2002Markus SchuMethod and circuit arrangement for enhancing the contrast of an imageUS20030099407 *Oct 15, 2002May 29, 2003Yuki MatsushimaImage processing apparatus, image processing method, computer program and storage mediumEP0798919A2Nov 19, 1992Oct 1, 1997Unisys CorporationDocument image compression system and methodEP0801360A2 *Mar 6, 1997Oct 15, 1997Samsung Electronics Co., Ltd.Image quality enhancing method using mean-matching histogram equalization and a circuit thereforJP2002247393A Title not availableJPH0695632A Title not availableJPH04349783A Title not available* Cited by examinerNon-Patent CitationsReference1Chinese Office Action for corresponding application 200310114817.3, dated Jul. 1, 2005.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS7733390 *Dec 15, 2006Jun 8, 2010Nikon CorporationImage-processing devices, methods, and programs, and electronic cameras and the like comprising sameUS7885462 *Nov 22, 2006Feb 8, 2011Samsung Electronics Co. Ltd.Image processing method and system using gain controllable clipped histogram equalizationUS7956932 *Jan 13, 2010Jun 7, 2011Kabushiki Kaisha ToshibaImage signal processing apparatus, method of controlling the same, and television signal receiving apparatusUS20100073395 *Sep 17, 2009Mar 25, 2010Omron CorporationImage processing device and image processing methodUS20100177062 *May 12, 2009Jul 15, 2010Quanta Computer Inc.Light compensation method* Cited by examinerClassifications U.S. Classification382/274, 382/254, 382/169, 382/168, 345/617International ClassificationH04N1/407, G09G5/00, G06K9/40, H04N5/20, G06K9/00, G06T5/40, G06T5/00, H04N5/57Cooperative ClassificationG06T5/40, G06T5/009European ClassificationG06T5/00M2, G06T5/40Legal EventsDateCodeEventDescriptionJun 5, 2012FPExpired due to failure to pay maintenance feeEffective date: 20120415Apr 15, 2012LAPSLapse for failure to pay maintenance feesNov 28, 2011REMIMaintenance fee reminder mailedSep 29, 2009CCCertificate of correctionJun 22, 2004ASAssignmentOwner name: SAMSUNG ELECTRONICS CO., LTD., KOREA, REPUBLIC OFFree format text: CORRECTIVE COVERSHEET TO CORRECT THE NAME OF THE CONVEYING PARTY PREVIOUSLY RECORDED ON REEL 014682, FRAME 0295.;ASSIGNORS:PARK, YUNG-JUN;OH, JAE-HWAN;KANG, HYUN;AND OTHERS;REEL/FRAME:015489/0725Effective date: 20031018Nov 4, 2003ASAssignmentOwner name: SAMSUNG ELECTRONICS CO., LTD., KOREA, REPUBLIC OFFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:PARK, YUNG-JUN;OH, SAE-HWAN;KANG, HYUN;AND OTHERS;REEL/FRAME:014682/0295Effective date: 20031018RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google