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EP0613294A1
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Gradation correction device and image sensing device therewith
Assignee: Panasonic Holdings Corp
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Filing: 1994-02-23
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Granted: —
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Expires: 2014-02-23
Abstract
Abstract A gradation correction device with a feature quantity extraction means (1105) for extracting feature quantities from input digital picture signals of a picture, which feature quantities reflecting luminace level distribution of the input digital picture signals; a gradation correction characteristic determination means (1106) for determining a gradation correction characteristic based on the feature quantities received from the feature quantity extraction means, which gradation correction characteristic defining an output signal for an input signal; and a correction means for correcting each of the input digital picture signals by using the gradation correction characteristic determined by the gradation correction characteristic determination means; whereby the gradation correction characteristic for the input picture digital signals is varied according to features thereof.
Inventors
- 👤 Akihiro Tamura
- 👤 Shigeo Sakaue
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 21:59
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/20; H04N23/00; H04N23/80; H04N23/84; H04N23/86
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
115 words
A gradation correction device comprising: a feature quantity extraction means for extracting feature quantities from input digital picture signals of a picture, which feature quantities reflecting luminance level distribution of the input digital picture signals; a gradation correction characteristic determination means for determining a gradation correction characteristic based on the feature quantities received from the feature quantity extraction means, which gradation correction characteristic defining an output signal for an input signal; and a correction means for correcting each of the input digital picture signals by using the gradation correction characteristic determined by the gradation correction characteristic determination means; whereby the gradation correction characteristic for the input picture digital signals is varied according to features thereof.
Claim 2
Dependent Claim
21 words
The gradation correction device according to Claim 1, wherein said input picture signals comprise a luminance signal and color difference signals.
Claim 3
Dependent Claim
28 words
The gradation correction device according to Claim 1, further comprising a luminance signal generation means for separating or synthesizing the luminance signal from the input digital picture signals.
Claim 4
Dependent Claim
29 words
The gradation correction device according to Claim 3, wherein said luminance signal generation means comprises a matrix circuit for generating the luminance signal from R, G and B signals.
Claim 5
Dependent Claim
51 words
The gradation correction device according to Claim 1, wherein said feature quantity extraction means determines the luminance level distribution by calculating a histogram of the luminance signals of the picture, the luminance signals being classified into a plurality of sections, frequency values of the sections being used as said feature quantities.
Claim 6
Dependent Claim
16 words
The gradation correction device according to Claim 5, wherein a number of said sections is three.
Claim 7
Dependent Claim
43 words
The gradation correction device according to Claim 1, wherein sad gradation correction characteristic determination means determines a gradation correction characteristic by averaging two prescribed gradation correction characteristic with a weight determined according to the feature quantities received from said feature quantity extraction means.
Claim 8
Dependent Claim
60 words
The gradation correction device according to Claim 1, said gradation correction characteristic determination means comprising a correction coefficient determination means comprising: a quantization means for quantizing the feature quantities received from said feature quantity extraction means; and a table means for providing a correction coefficient to determine the gradation correction characteristic according to quantized values quantized by the quantization means.
Claim 9
Dependent Claim
90 words
The gradation correction circuit according to Claim 8, said correction coefficient determination means further comprising: a memory means for storing a correction coefficient in a previous picture a counting means for counting a number of successive pictures where the correction coefficient received from said table means is successively greater than or successively less than the correction coefficient stored in the memory means; and an updating means for determining the correction coefficient to be sent to said correction means according to the number of successive pictures received from said counting means.
Claim 10
Dependent Claim
65 words
The gradation correction circuit according to Claim 8, said correction coefficient determination means further comprising: a memory means for storing a correction coefficient in a previous picture; and an updating means for determining the correction coefficient to be sent to said correction means according to a difference of the correction coefficient received from said table means with the correction coefficient stored in the memory means.
Claim 11
Dependent Claim
69 words
The gradation correction device according to Claim 1, said correction means comprising: a correction gain generation means for generating a correction gain for the input digital picture signals according to the input digital picture signals and the correction coefficient determined by said gradation correction characteristic determination means; and a multiplication means for multiplying the input digital picture signals with the correction gain received from the correction gain generation means.
Claim 12
Dependent Claim
103 words
The gradation correction device according to Claim 11, said correction gain generation means comprising: a first means for generating a first output value of a first gradation correction characteristic for an input digital picture signal; a second means for generating a second output value of a second gradation correction characteristic for the input digital picture signal; an adder means for adding the input digital picture signal and the correction coefficient determined by said gradation correction characteristic determination means to provide a weight; and a weighted average means for determining the correction gain by averaging the first and second output values with the weight.
Claim 13
Dependent Claim
122 words
The gradation correction device according to Claim 11, said correction gain generation means comprising: a first means for generating an output value of a first gradation correction characteristic for an input digital picture signal; a second means for generating an output value of a second gradation correction characteristic for the input digital picture signal; an average means for obtaining an average of input digital picture signals including the input digital picture signal and those thereabout; an adder means for adding the average received from the average means and the correction coefficient determined by said gradation correction characteristic determination means to provide a weight; and a weighted average means for determining the correction gain by averaging the two output values with the weight.
Claim 14
Dependent Claim
62 words
The gradation correction circuit according to Claim 12, wherein said first gradation characteristic Y1 of the input picture signal Y changes according to a following cubic equation: Y1 = {(1/a² * (Y-a)³ + a}, wherein "a" is a constant, and said second gradation characteristic Y2 changes according to a following linear equation: Y2 = b * Y, wherein "b" is a constant.
Claim 15
Dependent Claim
68 words
The gradation correction circuit according to Claim 13, wherein said first gradation characteristic Y1 changes with the input picture signal Y according to a following cubic equation: Y1 = {(1/a² * (Y-a)³ + a}, wherein "a" is a constant, and said second gradation characteristic Y2 changes with the input picture signal Y according to a following linear equation: Y2 = b * Y, wherein "b" is a constant.
Claim 16
Dependent Claim
203 words
The gradation correction circuit according to Claim 11, said correction gain generation means comprising: an average detection circuit for obtaining an average Ya of an input picture signal Y and input digital picture signals thereabout; a first adder for adding the average Ya with said correction coefficient; a clip circuit for clipping an output signal of the first adder with a value "0" and a maximum level of the input picture signal Y; a second adder for adding the input picture signal Y to provide 3Y; a first multiplier for multiplying the input picture signal Y two times to provide Y²; a third adder for adding an output signal of the first multiplier to a constant; a first subtractor for subtracting an output signal of the second adder from an output signal of the third adder; a second subtractor for subtracting an output signal of the clip circuit from the maximum level of the input picture signal; a second multiplier for multiplying an output signal of the first subtractor with an output signal of the second subtractor; and a fourth adder for adding an output signal of the clip circuit with an output signal of the second multiplier to provide the correction gain.
Claim 17
Dependent Claim
78 words
The gradation correction device according to Claim 1, said correction means comprising: a correction difference generation means for generating a correction difference of a corrected signal from the input digital picture signals, which corrected signal being calculated according to the input digital picture signals and the correction coefficient determined by said gradation correction characteristic determination means; and an adder means for adding the input digital picture signals with the correction difference received from the correction difference generation means.
Claim 18
Dependent Claim
125 words
An image sensing device comprising: an image sensor means for detecting input picture signals of a picture and for providing input digital picture signals; a feature quantity extraction means for extracting feature quantities from the input digital picture signals of a picture, which feature quantities reflecting luminance level distribution of the input picture digital signals; a gradation correction characteristic determination means for determining a gradation correction characteristic based on the feature quantities received from the feature quantity extraction means, which gradation correction characteristic defining an output signal for an input signal; and a correction means for correcting each of the input picture signals by using the gradation correction characteristic determined by the gradation correction characteristic determination means to provide corrected picture signals of the picture.
Claim 19
Dependent Claim
22 words
The image sensing device, further comprising a means for recording the corrected picture signals of the picture in an external recording medium.
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