Contrast control based on mean and deviation values

Claim 2

A level control circuit in a digital-video-signal processing circuit which processes a digital video signal which includes a digital luminance signal and a digital chrominance signal, the level control circuit comprising: mean value detection means for detecting a mean value of the digital luminance signal; subtraction means for subtracting the mean value detected by said mean value detection means from the digital luminance signal to provide a difference signal; restricting means for restricting the difference signal produced by said subtraction means to a range defined by predetermined upper and lower limits, to thereby output a luminance signal having a level varying in a certain range with the mean value detected by said mean value detection means as the median value; and liquid-crystal display panel driving means for driving a liquid-crystal display panel with the output luminance signal outputted by said restriction means.

Claim 3

A level control circuit in a digital-video-signal processing circuit comprising: amplifier means for amplifying a digital luminance signal; mean-value calculation means for calculating a mean value of a predetermined period of the digital luminance signal; luminance deviation-value calculation means for calculating deviation values of the predetermined period of the digital luminance signal from the mean value calculated by said mean-value calculation means; addition means for summing the deviation values of the predetermined period of the digital luminance signal calculated by said luminance deviation-value calculation means, thereby obtaining and outputting a contrast value; and gain control means for controlling gain of said amplifier means on the basis of the contrast value output from said addition means.

Claim 4

A level control circuit in a digital-video-signal processing circuit comprising: amplifier means for amplifying a digital luminance signal; mean-value calculation means for calculating a mean value of a predetermined period of the digital luminance signal; luminance deviation-value calculation means for calculating deviation values of the predetermined period of the digital luminance signal from the mean value calculated by said mean-value calculation means; addition means for summing the deviation values of the predetermined period of the digital luminance signal calculated by said luminance deviation-value calculation means, thereby obtaining and outputting a contrast value; and gain control means for controlling gain of said amplifier means on the basis of the contrast value output from said addition means.

Claim 5

A level control circuit according to claim 2, wherein said mean-value calculation means calculates a mean value of one-field period of the digital luminance signal amplified by said amplifier means.

Claim 6

A level control circuit in a digital-video-signal processing circuit which processes a digital video signal which includes a digital luminance signal and a digital chrominance signal, the level control circuit comprising: amplifier means for amplifying the digital luminance signal; mean-value calculation means for calculating a mean value of a predetermined period of the digital luminance signal amplified by said amplifier means; luminance deviation-value calculation means for calculating deviation values of the predetermined period of the digital luminance signal form the mean value calculated by said mean-value calculation means; addition means for summing the deviation values of the predetermined period of the digital luminance signal calculated by said luminance deviation-value calculation means with the mean value calculated by said means-value calculation means, thereby obtaining and outputting a contrast value; and gain control means for controlling gain of said amplifier means on the basis of the contrast value output from said addition means.

Claim 7

A level control circuit in a digital-video-signal processing circuit which processes a digital video signal which includes a digital luminance signal and a digital chrominance signal, the level control circuit comprising: amplifier means for amplifying the digital luminance signal; mean-value calculation means for calculating a mean value of a predetermined period of the digital luminance signal amplified by said amplifier means; luminance deviation-value calculation means for calculating deviation values of the predetermined period of the digital luminance signal form the mean value calculated by said mean-value calculation means; addition means for summing the deviation values of the predetermined period of the digital luminance signal calculated by said luminance deviation-value calculation means with the mean value calculated by said means-value calculation means, thereby obtaining and outputting a contrast value; and gain control means for controlling gain of said amplifier means on the basis of the contrast value output from said addition means.

Claim 8

A level control circuit according to claim 4, wherein said means-value calculation means calculates a mean value of one-field period of the digital luminance signal amplified by said amplifier means.

Claim 9

A liquid-crystal display device comprising: luminance/chrominance signal separation means for obtaining a digital luminance signal and a digital chrominance signal from a video signal; mean-value detection means for detecting a mean value of the digital luminance signal obtained by said luminance/chrominance signal separation means; subtraction means for subtracting the mean value of the luminance signal detected by said mean value detection means from the digital luminance signal to produce a difference signal; restriction means for restricting the difference signal produced by said subtraction means to a range defined by predetermined upper and lower limits, to thereby output a luminance signal having a level varying in a certain range with the mean value detected by said mean value detection means as the median value; driving-signal developing means for producing a liquid-crystal-driving signal from the output luminance signal outputted by said restriction means and the digital chrominance signal obtained by said luminance/chrominance signal separation means; and a liquid-crystal display panel means driven by the liquid-crystal-driving signal produced by said driving-signal developing means.

Claim 10

A liquid-crystal display device comprising: luminance/chrominance signal separation means for obtaining a digital luminance signal and a digital chrominance signal from a video signal; mean-value detection means for detecting a mean value of the digital luminance signal obtained by said luminance/chrominance signal separation means; subtraction means for subtracting the mean value of the luminance signal detected by said mean value detection means from the digital luminance signal to produce a difference signal; restriction means for restricting the difference signal produced by said subtraction means to a range defined by predetermined upper and lower limits, to thereby output a luminance signal having a level varying in a certain range with the mean value detected by said mean value detection means as the median value; driving-signal developing means for producing a liquid-crystal-driving signal from the output luminance signal outputted by said restriction means and the digital chrominance signal obtained by said luminance/chrominance signal separation means; and a liquid-crystal display panel means driven by the liquid-crystal-driving signal produced by said driving-signal developing means.

Claim 11

A liquid crystal display device comprising: luminance/chrominance signal separation means for obtaining and outputting a digital luminance signal and a digital chrominance signal form a digital video signal; amplifier means for amplifying the digital luminance signal output from said luminance/chrominance signal separation means; mean-value calculation means for calculating a mean value of a predetermined period of the digital luminance signal obtained and output by said luminance/chrominance signal separation means; luminance deviation-value calculation means for calculating deviation values of the predetermined period of the digital luminance signal from the mean value of the digital luminance signal calculated by said mean-value calculation means; addition means for summing the deviation values of the predetermined period of the digital luminance signal calculated by said luminance deviation calculation means, thereby obtaining and outputting a contrast value; gain control means for controlling gain of said amplifier means on the basis of the contrast value output from said addition means; drive means for producing a liquid-crystal drive signal from an output signal supplied by said gain control means and the digital chrominance signal output by said luminance/chrominance signal separation means; and a liquid-crystal display panel driven by said liquid-crystal drive signal from said drive means.

Claim 12

A liquid crystal display device comprising: luminance/chrominance signal separation means for obtaining and outputting a digital luminance signal and a digital chrominance signal form a digital video signal; amplifier means for amplifying the digital luminance signal output from said luminance/chrominance signal separation means; mean-value calculation means for calculating a mean value of a predetermined period of the digital luminance signal obtained and output by said luminance/chrominance signal separation means; luminance deviation-value calculation means for calculating deviation values of the predetermined period of the digital luminance signal from the mean value of the digital luminance signal calculated by said mean-value calculation means; addition means for summing the deviation values of the predetermined period of the digital luminance signal calculated by said luminance deviation calculation means, thereby obtaining and outputting a contrast value; gain control means for controlling gain of said amplifier means on the basis of the contrast value output from said addition means; drive means for producing a liquid-crystal drive signal from an output signal supplied by said gain control means and the digital chrominance signal output by said luminance/chrominance signal separation means; and a liquid-crystal display panel driven by said liquid-crystal drive signal from said drive means.

Claim 13

A level control circuit according to claim 1, wherein said mean value detection means comprises: addition means for receiving the digital luminance signal, and for developing an output signal; delay means connected to said addition means for delaying the output signal of said addition means; comparison means for comparing the delayed output signal with the digital luminance signal to produce a remainder signal; and multiplication means for multiplying the produced remainder signal by a constant, and for supplying the result of the multiplication to said addition means; and wherein said addition means adds a result of the multiplication to the received digital luminance signal to develop the output signal of said addition means.

Claim 14

A level control circuit according to claim 1, wherein said mean value detection means includes means for calculating a mean value of the digital luminance signal of one field period.

Claim 15

A liquid-crystal display device according to claim 6, wherein said mean-value detection means comprises: addition means for receiving the digital luminance signal, and for developing an output signal; delay means connected to said addition means for delaying the output signal of said addition means; comparison means for comparing the delayed output signal with the digital luminance signal to produce a remainder signal; and multiplication means for multiplying the produced remainder signal by a constant, and for supplying the result of the multiplication to said addition means; and wherein said addition means adds a result of the multiplication to the received digital luminance signal to develop the output signal of said addition means.

Claim 16

A liquid-crystal display device according to claim 6, wherein said mean-value detection means includes means for calculating a mean value for the digital luminance signal of one field period.

Claim 17

A digital video signal processing circuit for processing a digital video signal which includes a digital luminance signal and a digital chrominance signal, the processing circuit comprising: amplifier means for amplifying the digital luminance signal; means-value calculation means for calculating a mean value of the digital luminance signal of a predetermined number of fields; deviation-value calculation means for calculating a deviation value of the digital luminance signal for the predetermined number of fields, using the mean value calculated by said mean-value calculation means; addition means for adding deviation values of several digital luminance signals of the predetermined number of fields to obtain a contrast value; and gain control means for controlling a gain of said amplifier means on the basis of the contrast value obtained by said addition means.

Claim 18

A digital video signal processing circuit for processing a digital video signal which includes a digital luminance signal and a digital chrominance signal, the processing circuit comprising: amplifier means for amplifying the digital luminance signal; means-value calculation means for calculating a mean value of the digital luminance signal of a predetermined number of fields; deviation-value calculation means for calculating a deviation value of the digital luminance signal for the predetermined number of fields, using the mean value calculated by said mean-value calculation means; addition means for adding deviation values of several digital luminance signals of the predetermined number of fields to obtain a contrast value; and gain control means for controlling a gain of said amplifier means on the basis of the contrast value obtained by said addition means.

Claim 19

A digital video signal processing circuit according to claim 12, wherein said mean-value calculation means calculates said mean-value of the digital luminance signal of a predetermined number of fields, as amplified by said amplifier means; and wherein said addition means adds deviation values of several luminance signals of the predetermined number of fields to obtain the contrast value.