EP0654943A2
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EP
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Image enhancement method and circuit
Assignee: Samsung Electronics Co Ltd
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Filing: 1994-11-23
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Granted: —
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Expires: 2014-11-23
Abstract
Abstract The present invention relates to an image enhancement method and circuit adaptive to a scene which adaptively controls the brightness and contrast of a video input signal according to its average brightness level. The circuit comprises calculating means (20) for calculating the average brightness level during a predetermined period with respect to a video signal to be input through an input terminal; and controlling means (30) for controlling the brightness and contrast of the video input signal according to brightness correction characteristics corresponding to the calculated average brightness level, in which the range of the average brightness level in the video input signal is divided into a plurality of areas, and a plurality of input-output characteristic curves are provided so that the brightness and contrast of the video input signal is differently corrected for respective areas. The present invention has effects that naturally display even a dimly-lit picture by preventing an abrupt variation in brightness, and provide advanced pictures in brightness and contrast by adjusting only the contrast at a particular nAPL range.
Inventors
- 👤 Myeong-Hwan 104-712 Wonchon Jukong Apt. Lee
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 05:57
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/57; H04N5/14; H04N5/20
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
98 words
An image enhancement method adaptive to a scene which controls brightness and contrast of a video signal using an average brightness level, the method comprising the steps: dividing a range of the average brightness level in a video input signal into a plurality of areas; setting an individually different brightness correction characteristic to each of said divided areas; calculating the average brightness level during a predetermined period with respect to the video input signal; and controlling the brightness and contrast of the video input signal according to the brightness correction characteristic corresponding to said calculated average brightness level.
Claim 2
Dependent Claim
40 words
The image enhancement method as claimed in claim 1, wherein said area dividing step comprises the step of dividing the average brightness level range of the video input signal into a plurality of areas according to efficiency of contrast enhancement.
Claim 3
Dependent Claim
112 words
The image enhancement method as claimed in claim 1 or 2, wherein said areas are composed of a first area in which the average brightness level corresponds to a dark scene, a second area of an intermediate average brightness level, a third area with an average brightness level between that of said first and second areas and a fourth area with an average brightness level above that of said second area, in the case that the range of average brightness level in the video input signal is between 0 and 1, said first area has average brightness level around "0" and said second area has average brightness level at or near "0.5".
Claim 4
Dependent Claim
47 words
The image enhancement method as claimed in any of claims 1, 2 or 3, wherein said brightness and contrast controlling step comprises the step of outputting the video input signal as it is, in the case that the calculated average brightness level is within said first area.
Claim 5
Dependent Claim
79 words
The image enhancement method as claimed in claim 3 or claim 4 as dependant upon claim 3, wherein said brightness and contrast controlling step comprises the step of correcting said level x of the video input signal by the following expression for contrast enhancement, in the case that the calculated average brightness level is within said second area: OUT=y3(x) y3(x)=pow(xL,2), y3(x)=pow(xH,0.5) where, OUT is a corrected video signal, xL is a 0∼0.5 period and xH is a 0.5∼1 period.
Claim 6
Dependent Claim
108 words
The image enhancement method as claimed in claim 3 or claims 4 or 5 as dependent upon claim 3, wherein said brightness and contrast controlling step comprises the step of correcting said level x of the video input signal by the following expression for contrast enhancement, in the case that the calculated average brightness level is within said second area: OUT=amp X abs[m-abs(nAPL-m)] X y3(x) y3(x)=pow(xL,2), y3(x)=pow(xH,0.5) where, said OUT is a corrected video signal, amp is an amplification ratio, abs is an absolute value, nAPL is a normalized average picture level value, m is usually 0.5, xL is a 0∼0.5 period, and xH is a 0.5∼1 period.
Claim 7
Dependent Claim
133 words
The image enhancement method as claimed in claim 3 or any of claims 4 to 6 as dependent upon claim 3, wherein said brightness and contrast controlling step comprises the step of correcting said level x of the video input signal by the following expression for contrast enhancement, in the case that the calculated average brightness level is within said second area: OUT=amp1 X abs(m-abs(m-nAPL(l))) X y3l(x) +amp2 X abs(m-abs(nAPL(h)-m)) X y3h(x) y3l(x)=pow(xL,2), y3h(x)=pow(xH,0.5) where, said OUT is a corrected video signal, m is usually 0.5, amp1 and amp2 are amplification ratios above and below "m", abs is an absolute value, nAPL(l) and nAPL(h) are normalized average picture level values obtained by respectively calculating the video input signal above and below "m", xL is a 0∼0.5 period, and xH is a 0.5∼1 period.
Claim 8
Dependent Claim
103 words
The image enhancement method as claimed in claim 3 or any of claims 4 to 7 as dependent upon claim 3, wherein said brightness and contrast controlling step comprises the step of correcting said level x of the video input signal by the following expression for contrast enhancement, in the case that the calculated average brightness level is within said third area: OUT=abs(abs(p-q)/p) X y1(x), y1(x)=pow(x,0.5) p=a_area-period/2, q=abs(a_area_center-nAPL) where, OUT is a corrected video signal, abs is an absolute value, a_area-period represents a period of an area "a", a_area_center is a central value of the "a" area, nAPL is a normalized APL value.
Claim 9
Dependent Claim
85 words
The image enhancement method as claimed in claim 3 or any of claims 4 to 8 as dependent upon claim 3, wherein said brightness and contrast controlling step comprises the step of correcting said level x of the video input signal by the following expression for contrast enhancement, in the case that the calculated average brightness level is within said first area or said third area: OUT=(0.5-nAPL) X y1(x), y1(x)=pow(x,0.5) where, said OUT is a corrected video signal, and nAPL is a normalized APL value.
Claim 10
Dependent Claim
96 words
The image enhancement method as claimed in claim 3 or any of claims 4 to 9 as dependent upon claim 3, wherein said brightness and contrast controlling step comprises the step of correcting said level x of the video input signal by the following expression for contrast enhancement, in the case that the calculated average brightness level is within said fourth area: OUT=amp X abs(nAPL-m) X y2(x), y2(x)=pow(x,2) where, said OUT is a corrected video signal, m is commonly 0.5, amp is an amplification ratio, abs is an absolute value, nAPL is a normalized APL value.
Claim 11
Dependent Claim
128 words
An image enhancement circuit adaptive to a scene which controls and outputs the brightness and contrast of a video signal using an average brightness level, the circuit comprising: calculating means (20) for calculating the average brightness level during a predetermined period with respect to a video signal to be input through an input terminal; and controlling means (30) for controlling the brightness and contrast of the video input signal according to brightness correction characteristics corresponding to said calculated average brightness level, in which the range of said average brightness level in said video input signal is divided into a plurality of areas, and a plurality of input-output characteristic curves are provided so that the brightness and contrast of said video input signal is differently corrected for respective areas.
Claim 12
Dependent Claim
49 words
The image enhancement circuit as claimed in claim 11, wherein said brightness and contrast controlling means (30) stores each of brightness correction characteristics corresponding to said average brightness level as format of a look-up table which is composed of a video output signal corresponding to a video input signal.
Claim 13
Dependent Claim
46 words
The image enhancement circuit as claimed in claim 11 or 12, wherein said brightness and contrast controlling means (30) corrects the brightness and contrast of a video signal to be input following the video input signal which is used in calculating of the average brightness level.
Claim 14
Dependent Claim
60 words
The image enhancement circuit as claimed in claim 11, 12 or 13, further comprising a delay unit, located before said brightness and contrast controlling means (30), for delaying and outputting the video input signal supplied through an input so that the brightness and contrast of the video input signal used in calculating of the average brightness level can be controlled.
Claim 15
Dependent Claim
59 words
The image enhancement circuit as claimed in any of claims 11 to 14, further comprising an amplifier (50) which amplifies said video input signal with an amplification ratio which is varied according to the average brightness level calculated by said average brightness level calculating means (20), and outputs the amplified signal to said brightness and contrast controlling means (30).
Claim 16
Dependent Claim
78 words
The image enhancement circuit as claimed in claim 15, wherein said amplifier (50) amplifies said video input signal so that the slope of an input-output characteristic curve becomes low, in the case that the calculated value of said average brightness level is near "1", while it amplifies said video input signal so that the slope of an input-output characteristic curve becomes high, in the case that the calculated value of said average brightness level is close to "0".
Claim 17
Dependent Claim
78 words
The image enhancement circuit as claimed in any of claims 11 to 16, wherein said average brightness level calculating means (20) comprises a low-pass filter (60) for counting a value of the average brightness level by passing through only low components of the video input signal, and then for outputting corresponding voltage; and a decoder (70) for outputting a control signal to control said brightness and contrast controlling means according to said voltage supplied from said low-pass filter.
References Cited (Backward Citations)
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