Image quality correction circuit

Claim 2

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; a slice circuit for slicing the outputted amplitude of said variable gain amplifier at a prescribed value; and means for combining an image quality correction signal outputted from said slice circuit with the luminance signal to be corrected and thereby outputting a corrected luminance signal.

Claim 3

An image quality correction circuit according to claim 1, wherein said high-frequency component extracting means comprises a low-pass filter for extracting a low-frequency component of the luminance signal, and a subtractor for obtaining the difference between the low-frequency component passed through said low-pass filter and the luminance signal.

Claim 4

An image quality correction circuit according to claim 1, wherein said high-frequency component extracting means comprises a first low-pass filter for extracting a low-frequency component of the luminance signal, a second low-pass filter, having a different cut-off frequency characteristic from that of said first low-pass filter, for extracting a low-frequency component of the luminance signal, and a subtractor for obtaining the difference between the low-frequency components respectively passed through said first and said second low-pass filters.

Claim 5

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; contour detecting means for detecting a contour signal from a luminance signal; a variable gain amplifier for amplifying the detected contour signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; a slice circuit for slicing the outputted amplitude of said variable gain amplifier at a prescribed value; and means for combining an image quality correction signal outputted from said slice circuit with the luminance signal to be corrected and thereby outputting a corrected luminance signal.

Claim 6

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; contour detecting means for detecting a contour signal from a luminance signal; a variable gain amplifier for amplifying the detected contour signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; a slice circuit for slicing the outputted amplitude of said variable gain amplifier at a prescribed value; and means for combining an image quality correction signal outputted from said slice circuit with the luminance signal to be corrected and thereby outputting a corrected luminance signal.

Claim 7

An image quality correction circuit according to claim 1, wherein said color density detecting means detects the color density by full-wave rectifying different color-difference signals arid then summing the results or by full-wave rectifying different chrominance signals and then summing the results.

Claim 8

An image quality correction circuit according to claim 1, wherein said color density detecting means detects the color density by rectifying a carrier chrominance signal or by full-wave rectifying different chrominance signals and then summing the results.

Claim 9

An image quality correction circuit according to claim 1, further comprising: a variable gain amplifier for amplifying the amplitude of a color density signal to be detected, by controlling the gain thereof on the basis of a preset voltage value, wherein the gain with which to amplify the high-frequency component of the luminance signal is controlled in accordance with an output signal from said variable gain amplifier.

Claim 10

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a slice circuit for slicing the outputted amplitude of said high-frequency component extracting means at a prescribed value; a variable gain amplifier for amplifying the output of said slice circuit by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal.

Claim 11

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a slice circuit for slicing the outputted amplitude of said high-frequency component extracting means at a prescribed value; a variable gain amplifier for amplifying the output of said slice circuit by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal.

Claim 12

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; a slice circuit for slicing the outputted amplitude of said variable gain amplifier at a prescribed value; and means for combining an image quality correction signal outputted from said slice circuit with the luminance signal to be corrected and thereby outputting a corrected luminance signal.

Claim 13

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; a slice circuit for slicing the outputted amplitude of said variable gain amplifier at a prescribed value; and means for combining an image quality correction signal outputted from said slice circuit with the luminance signal to be corrected and thereby outputting a corrected luminance signal.

Claim 14

An image quality correction circuit according to claim 9, wherein said color density detecting means comprises rectifiers for full-wave rectifying different color-difference signals or two kinds of chrominance signals, respectively, an adder for summing the two signals after rectification, and a multiplier for multiplying an output signal of said adder by an inverted version of the luminance signal, and the color density is detected from the output of said multiplier.

Claim 15

An image quality correction circuit according to claim 9, wherein said color density detecting means comprises a rectifier for rectifying a carrier chrominance signal, a multiplier for multiplying an inverted luminance signal and an output signal of said rectifier, and a low-pass filter for extracting a low-frequency component from an output signal of said multiplier, and the color density is detected from the output of said low-pass filter.

Claim 16

An image quality correction circuit according to claim 9, wherein said color density detecting means comprises a multiplier for multiplying different color-difference signals, a weighting circuit for assigning a weight to an output signal of said multiplier, and a maximum value detection circuit for detecting a maximum value among an output signal of said weighting circuit, one color-difference signal or a weighted version of the one color-difference signal, and the other color-difference signal or a weighted version of the other color-difference signal, and the color density is detected from the output of said maximum value detection circuit.

Claim 17

An image quality correction circuit according to claim 9, wherein said color density detecting means comprises a subtractor for subtracting a second chrominance signal from a first chrominance signal, and a maximum value detection circuit for detecting a maximum value among an output signal of said subtractor or a weighted version of the output signal, an inverted signal of the first chrominance signal or a weighted version of the inverted signal, and the second chrominance signal or a weighted version of the second chrominance signal, and the color density is detected from the output of said maximum value detection circuit.

Claim 18

An image quality correction circuit according to claim 9, wherein said color density detecting means comprises a half-wave rectifier for half-wave rectifying an inverted signal of a first chrominance signal, a multiplier for multiplying an output signal of said half-wave rectifier circuit by a second chrominance signal, and a maximum value detection circuit for detecting a maximum value among three kinds of signals having an output signal of said multiplier or a weighted version of the output signal, the first chrominance signal or a weighted version of the first chrominance signal, and an inverted signal of the second chrominance signal or a weighted version of the inverted signal, or among four kinds of signals having the three kinds of signals plus the second chrominance signal or a weighted version of the second chrominance signal, and the color density is detected from the output of said maximum value detection circuit.

Claim 19

An image quality correction circuit according to claim 9, wherein said color density detecting means comprises an adder for summing different color-difference signals or two kinds of chrominance signals after full-wave rectification, and a multiplier for multiplying an output signal of said adder by a binary version of the luminance signal, and the color density is detected from the output of said multiplier.

Claim 20

An image quality correction circuit according to claim 9, wherein said color density detecting means comprises a rectifier for rectifying a carrier chrominance signal, a multiplier for multiplying an output signal of said rectifier by a binary version of the luminance signal, and a low-pass filter for extracting a low-frequency component from an output signal of said multiplier, and the color density is detected from the output of said low-pass filter.

Claim 21

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a slice circuit for slicing the outputted amplitude of said high-frequency component extracting means at a prescribed value; a variable gain amplifier for amplifying the output of said slice circuit by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal.

Claim 22

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a slice circuit for slicing the outputted amplitude of said high-frequency component extracting means at a prescribed value; a variable gain amplifier for amplifying the output of said slice circuit by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal.

Claim 23

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; slice circuits, corresponding to the respective color-difference signals, for slicing the outputted amplitude of said variable gain amplifiers at a prescribed value; and means for combining an image quality correction signal outputted from said associated slice circuit with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal.

Claim 24

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; slice circuits, corresponding to the respective color-difference signals, for slicing the outputted amplitude of said variable gain amplifiers at a prescribed value; and means for combining an image quality correction signal outputted from said associated slice circuit with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal.

Claim 25

An image quality correction circuit according to claim 18, wherein said color density detecting means comprises a rectifier for rectifying the signal relating to color, a multiplier for multiplying an output signal of said rectifier by an inverted version of the luminance signal, and a low-pass filter for extracting a low-frequency component from an output signal of said multiplier, and the color density is detected from the output of said low-pass filter.

Claim 26

An image quality correction circuit according to claim 18, wherein said color density detecting means comprises a rectifier for rectifying the signal relating to color, and a multiplier for multiplying an output signal of said rectifier by a binary version of the luminance signal, and the color density is detected from the output of said multiplier.

Claim 27

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises rectifiers for full-wave rectifying different color-difference signals or two kinds of chrominance signals, respectively, an adder for summing the two signals after rectification, and a multiplier for multiplying an output signal of said adder by an inverted version of the luminance signal, and the color density is detected from the output of said multiplier.

Claim 28

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises rectifiers for full-wave rectifying different color-difference signals or two kinds of chrominance signals, respectively, an adder for summing the two signals after rectification, and a multiplier for multiplying an output signal of said adder by an inverted version of the luminance signal, and the color density is detected from the output of said multiplier.

Claim 29

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a rectifier for rectifying a carrier chrominance signal, a multiplier for multiplying an inverted luminance signal and an output signal of said rectifier, and a low-pass filter for extracting a low-frequency component from an output signal of said multiplier, and the color density is detected from the output of said low-pass filter.

Claim 30

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a rectifier for rectifying a carrier chrominance signal, a multiplier for multiplying an inverted luminance signal and an output signal of said rectifier, and a low-pass filter for extracting a low-frequency component from an output signal of said multiplier, and the color density is detected from the output of said low-pass filter.

Claim 31

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a multiplier for multiplying different color-difference signals, a weighting circuit for assigning a weight to an output signal of said multiplier, and a maximum value detection circuit for detecting a maximum value among an output signal of said weighting circuit, one color-difference signal or a weighted version of the one color-difference signal, and the other color-difference signal or a weighted version of the other color-difference signal, and the color density is detected from the output of said maximum value detection circuit.

Claim 32

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a multiplier for multiplying different color-difference signals, a weighting circuit for assigning a weight to an output signal of said multiplier, and a maximum value detection circuit for detecting a maximum value among an output signal of said weighting circuit, one color-difference signal or a weighted version of the one color-difference signal, and the other color-difference signal or a weighted version of the other color-difference signal, and the color density is detected from the output of said maximum value detection circuit.

Claim 33

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a subtractor for subtracting a second chrominance signal from a first chrominance signal, and a maximum value detection circuit for detecting a maximum value among an output signal of said subtractor or a weighted version of the output signal, an inverted signal of the first chrominance signal or a weighted version of the inverted signal, and the second chrominance signal or a weighted version of the second chrominance signal, and the color density is detected from the output of said maximum value detection circuit.

Claim 34

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a subtractor for subtracting a second chrominance signal from a first chrominance signal, and a maximum value detection circuit for detecting a maximum value among an output signal of said subtractor or a weighted version of the output signal, an inverted signal of the first chrominance signal or a weighted version of the inverted signal, and the second chrominance signal or a weighted version of the second chrominance signal, and the color density is detected from the output of said maximum value detection circuit.

Claim 35

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a half-wave rectifier for half-wave rectifying an inverted signal of a first chrominance signal, a multiplier for multiplying chrominance signal, and a maximum value detection circuit for detecting a maximum value among three kinds of signals having an output signal of said multiplier or a weighted version of the output signal, the first chrominance signal or a weighted version of the first chrominance signal, and an inverted signal of the second chrominance signal or a weighted version of the inverted signal, or among four kinds of signals having the three kinds of signals plus the second chrominance signal or a weighted version of the second chrominance signal, and the color density is detected from the output of said maximum value detection circuit.

Claim 36

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a half-wave rectifier for half-wave rectifying an inverted signal of a first chrominance signal, a multiplier for multiplying chrominance signal, and a maximum value detection circuit for detecting a maximum value among three kinds of signals having an output signal of said multiplier or a weighted version of the output signal, the first chrominance signal or a weighted version of the first chrominance signal, and an inverted signal of the second chrominance signal or a weighted version of the inverted signal, or among four kinds of signals having the three kinds of signals plus the second chrominance signal or a weighted version of the second chrominance signal, and the color density is detected from the output of said maximum value detection circuit.

Claim 37

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises an adder for summing different color-difference signals or two kinds of chrominance signals after full-wave rectification, and a multiplier for multiplying an output signal of said adder by a binary version of the luminance signal, and the color density is detected from the output of said multiplier.

Claim 38

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises an adder for summing different color-difference signals or two kinds of chrominance signals after full-wave rectification, and a multiplier for multiplying an output signal of said adder by a binary version of the luminance signal, and the color density is detected from the output of said multiplier.

Claim 39

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a rectifier for rectifying a carrier chrominance signal, a multiplier for multiplying an output signal of said rectifier by a binary version of the luminance signal, and a low-pass filter for extracting a low-frequency component from an output signal of said multiplier, and the color density is detected from the output of said low-pass filter.

Claim 40

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; and means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal, wherein said color density detecting means comprises a rectifier for rectifying a carrier chrominance signal, a multiplier for multiplying an output signal of said rectifier by a binary version of the luminance signal, and a low-pass filter for extracting a low-frequency component from an output signal of said multiplier, and the color density is detected from the output of said low-pass filter.

Claim 41

An image quality correction circuit according to claim 1, further comprising: a boundary reduction circuit for accepting a color density signal representing the color density detected by said color density detecting means, and for reducing the amplitude of the color density signal at portions near the boundary between no-color and color areas or near the boundary between different colors, wherein an output signal from said boundary reduction circuit is taken as a new color density signal for image quality correction.

Claim 42

An image quality correction circuit according to claim 9, further comprising: a boundary reduction circuit for accepting a color density signal representing the color density detected by said color density detecting means, and for reducing the amplitude of the color density signal at portions near the boundary between no-color and color areas or near the boundary between different colors, wherein an output signal from said boundary reduction circuit is taken as a new color density signal for image quality correction.

Claim 43

An image quality correction circuit according to claim 18, further comprising: a boundary reduction circuit for accepting a color density signal representing the color density detected by said color density detecting means, and for reducing the amplitude of the color density signal at portions near the boundary between no-color and color areas or near the boundary between different colors, wherein an output signal from said boundary reduction circuit is taken as a new color density signal for image quality correction.

Claim 44

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal; and a boundary reduction circuit for accepting a color density signal representing the color density detected by said color density detecting means, and for reducing the amplitude of the color density signal at portions near the boundary between no-color and color areas or near the boundary between different colors; wherein an output signal from said boundary reduction circuit is taken as a new color density signal for image quality correction.

Claim 45

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal; and a boundary reduction circuit for accepting a color density signal representing the color density detected by said color density detecting means, and for reducing the amplitude of the color density signal at portions near the boundary between no-color and color areas or near the boundary between different colors; wherein an output signal from said boundary reduction circuit is taken as a new color density signal for image quality correction.

Claim 46

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal; and a boundary reduction circuit for accepting a color density signal representing the color density detected by said color density detecting means, and for reducing the amplitude of the color density signal at portions near the boundary between no-color and color areas or near the boundary between different colors; wherein an output signal from said boundary reduction circuit is taken as a new color density signal for image quality correction.

Claim 47

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal; and a boundary reduction circuit for accepting a color density signal representing the color density detected by said color density detecting means, and for reducing the amplitude of the color density signal at portions near the boundary between no-color and color areas or near the boundary between different colors; wherein an output signal from said boundary reduction circuit is taken as a new color density signal for image quality correction.

Claim 48

An image quality correction circuit comprising: color density detecting means for detecting color density from a primary color signal and a luminance signal; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective primary color signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated primary color signal to be corrected and thereby outputting a corrected primary color signal; and a boundary reduction circuit for accepting a color density signal representing the color density detected by said color density detecting means, and for reducing the amplitude of the color density signal at portions near the boundary between no-color and color areas or near the boundary between different colors; wherein an output signal from said boundary reduction circuit is taken as a new color density signal for image quality correction.

Claim 49

An image quality correction circuit comprising: color density detecting means for detecting color density from a primary color signal and a luminance signal; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective primary color signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated primary color signal to be corrected and thereby outputting a corrected primary color signal; and a boundary reduction circuit for accepting a color density signal representing the color density detected by said color density detecting means, and for reducing the amplitude of the color density signal at portions near the boundary between no-color and color areas or near the boundary between different colors; wherein an output signal from said boundary reduction circuit is taken as a new color density signal for image quality correction.

Claim 50

An image quality correction circuit according to claim 31, wherein said boundary reduction circuit comprises a delay circuit for delaying the color density signal inputted thereto and a minimum value detection circuit for detecting a minimum value between an output signal from said delay circuit and the color density signal not passed through said delay circuit, and an output of said minimum value detection circuit is taken as a new color density signal for image quality correction.

Claim 51

An image quality correction circuit according to claim 31, wherein said boundary reduction circuit comprises: a first delay circuit for delaying the color density signal inputted thereto; a second delay circuit for delaying an output signal of said first delay circuit; a subtractor for subtracting the input color density signal from an output signal of said second delay circuit; an absolute value detection circuit for detecting the absolute value of an output of said subtractor; a comparator for comparing an output signal of said absolute value detection circuit with a specific voltage and for outputting the result as a binary signal; and a multiplier for multiplying an output signal of said comparator by the output signal of said first delay circuit, and an output signal of said multiplier is taken as a new color density signal for image quality correction.

Claim 52

An image quality correction circuit according to claim 1, further comprising: a small-amplitude removal circuit for removing small amplitude portions of a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said small-amplitude removal circuit is taken as a new color density signal for image quality correction so that no image correction may be applied to low color-density areas.

Claim 53

An image quality correction circuit according to claim 9, further comprising: a small-amplitude removal circuit for removing small amplitude portions of a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said small-amplitude removal circuit is taken as a new color density signal for image quality correction so that no image correction may be applied to low color-density areas.

Claim 54

An image quality correction circuit according to claim 18, further comprising: a small-amplitude removal circuit for removing small amplitude portions of a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said small-amplitude removal circuit is taken as a new color density signal for image quality correction so that no image correction may be applied to low color-density areas.

Claim 55

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal; and a small-amplitude removal circuit for removing small amplitude portions of a color density signal representing the color density detected by said color density detecting means; wherein an output signal from said small-amplitude removal circuit is taken as a new color density signal for image quality correction so that no image correction may be applied to low color-density areas.

Claim 56

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal; and a small-amplitude removal circuit for removing small amplitude portions of a color density signal representing the color density detected by said color density detecting means; wherein an output signal from said small-amplitude removal circuit is taken as a new color density signal for image quality correction so that no image correction may be applied to low color-density areas.

Claim 57

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal; and a small-amplitude removal circuit for removing small amplitude portions of a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said small-amplitude removal circuit is taken as a new color density signal for image quality correction so that no image correction may be applied to low color-density areas.

Claim 58

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal; and a small-amplitude removal circuit for removing small amplitude portions of a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said small-amplitude removal circuit is taken as a new color density signal for image quality correction so that no image correction may be applied to low color-density areas.

Claim 59

An image quality correction circuit comprising: color density detecting means for detecting color density from a primary color signal and a luminance signal; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective primary color signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated primary color signal to be corrected and thereby outputting a corrected primary color signal; and a small-amplitude removal circuit for removing small amplitude portions of a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said small-amplitude removal circuit is taken as a new color density signal for image quality correction so that no image correction may be applied to low color-density areas.

Claim 60

An image quality correction circuit comprising: color density detecting means for detecting color density from a primary color signal and a luminance signal; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective primary color signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated primary color signal to be corrected and thereby outputting a corrected primary color signal; and a small-amplitude removal circuit for removing small amplitude portions of a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said small-amplitude removal circuit is taken as a new color density signal for image quality correction so that no image correction may be applied to low color-density areas.

Claim 61

An image quality correction circuit according to claim 1, further comprising: offset addition means for adding a DC component to a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said offset addition means is taken as a new color density signal for image quality correction so that a certain degree of image quality correction effect can be obtained for no-color areas.

Claim 62

An image quality correction circuit according to claim 9, further comprising: offset addition means for adding a DC component to a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said offset addition means is taken as a new color density signal for image quality correction so that a certain degree of image quality correction effect can be obtained for no-color areas.

Claim 63

An image quality correction circuit according to claim 18, further comprising: offset addition means for adding a DC component to a color density signal representing the color density detected by said color density detecting means, wherein an output signal from said offset addition means is taken as a new color density signal for image quality correction so that a certain degree of image quality correction effect can be obtained for no-color areas.

Claim 64

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal; and offset addition means for adding a DC component to a color density signal representing the color density detected by said color density detecting means; wherein an output signal from said offset addition means is taken as a new color density signal for image quality correction so that a certain degree of image quality correction effect can be obtained for no-color areas.

Claim 65

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal; and offset addition means for adding a DC component to a color density signal representing the color density detected by said color density detecting means; wherein an output signal from said offset addition means is taken as a new color density signal for image quality correction so that a certain degree of image quality correction effect can be obtained for no-color areas.

Claim 66

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal; and offset addition means for adding a DC component to a color density signal representing the color density detected by said color density detecting means; wherein an output signal from said offset addition means is taken as a new color density signal for image quality correction so that a certain degree of image quality correction effect can be obtained for no-color areas.

Claim 67

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal; and offset addition means for adding a DC component to a color density signal representing the color density detected by said color density detecting means; wherein an output signal from said offset addition means is taken as a new color density signal for image quality correction so that a certain degree of image quality correction effect can be obtained for no-color areas.

Claim 68

An image quality correction circuit comprising: color density detecting means for detecting color density from a primary color signal and a luminance signal; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective primary color signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated primary color signal to be corrected and thereby outputting a corrected primary color signal; and offset addition means for adding a DC component to a color density signal representing the color density detected by said color density detecting means; wherein an output signal from said offset addition means is taken as a new color density signal for image quality correction so that a certain degree of image quality correction effect can be obtained for no-color areas.

Claim 69

An image quality correction circuit comprising: color density detecting means for detecting color density from a primary color signal and a luminance signal; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; variable gain amplifiers, corresponding to respective primary color signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated variable gain amplifier with the associated primary color signal to be corrected and thereby outputting a corrected primary color signal; and offset addition means for adding a DC component to a color density signal representing the color density detected by said color density detecting means; wherein an output signal from said offset addition means is taken as a new color density signal for image quality correction so that a certain degree of image quality correction effect can be obtained for no-color areas.

Claim 70

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a first variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said first variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal; and a second variable gain amplifier whose gain to amplify the amplitude of a signal representing the color density to be detected is controlled in accordance with a voltage value specified by a microcomputer or set by a variable resistor; wherein the gain to amplify the high-frequency component of the luminance signal is controlled in relation to an output signal of said second variable gain amplifier.

Claim 71

An image quality correction circuit comprising: color density detecting means for detecting color density from a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of a luminance signal; a first variable gain amplifier for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said first variable gain amplifier with the luminance signal to be corrected and thereby outputting a corrected luminance signal; and a second variable gain amplifier whose gain to amplify the amplitude of a signal representing the color density to be detected is controlled in accordance with a voltage value specified by a microcomputer or set by a variable resistor; wherein the gain to amplify the high-frequency component of the luminance signal is controlled in relation to an output signal of said second variable gain amplifier.

Claim 72

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; first variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated first variable gain amplifier with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal; and a second variable gain amplifier whose gain to amplify the amplitude of a signal representing the color density to be detected is controlled in accordance with a voltage value specified by a microcomputer or set by a variable resistor; wherein the gain to amplify the high-frequency component of the luminance signal is controlled in relation to an output signal of said second variable gain amplifier.

Claim 73

An image quality correction circuit comprising: color density detecting means for detecting color density from a luminance signal and a signal relating to color; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; first variable gain amplifiers, corresponding to respective color-difference signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated first variable gain amplifier with the associated chrominance signal to be corrected and thereby outputting a corrected chrominance signal; and a second variable gain amplifier whose gain to amplify the amplitude of a signal representing the color density to be detected is controlled in accordance with a voltage value specified by a microcomputer or set by a variable resistor; wherein the gain to amplify the high-frequency component of the luminance signal is controlled in relation to an output signal of said second variable gain amplifier.

Claim 74

An image quality correction circuit comprising: color density detecting means for detecting color density from a primary color signal and a luminance signal; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; first variable gain amplifiers, corresponding to respective primary color signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated first variable gain amplifier with the associated primary color signal to be corrected and thereby outputting a corrected primary color signal; and a second variable gain amplifier whose gain to amplify the amplitude of a signal representing the color density to be detected is controlled in accordance with a voltage value specified by a microcomputer or set by a variable resistor; wherein the gain to amplify the high-frequency component of the luminance signal is controlled in relation to an output signal of said second variable gain amplifier.

Claim 75

An image quality correction circuit comprising: color density detecting means for detecting color density from a primary color signal and a luminance signal; high-frequency component extracting means for extracting a high-frequency component of the luminance signal; first variable gain amplifiers, corresponding to respective primary color signals, for amplifying the extracted high-frequency component of the luminance signal by performing control in such a manner that the gain thereof is increased when the detected color density is high, and is reduced when the detected color density is low; means for combining an image quality correction signal outputted from said associated first variable gain amplifier with the associated primary color signal to be corrected and thereby outputting a corrected primary color signal; and a second variable gain amplifier whose gain to amplify the amplitude of a signal representing the color density to be detected is controlled in accordance with a voltage value specified by a microcomputer or set by a variable resistor; wherein the gain to amplify the high-frequency component of the luminance signal is controlled in relation to an output signal of said second variable gain amplifier.