Automatic hue control circuit

Claim 2

In a color television receiver including signal processing circuitry for extracting and processing luminance information from a main carrier and color reference information from a modulated subcarrier, an automatic hue control arrangement for maintaining substantially true fleshtone hues, comprising in combination: circuit means for deriving from the color reference information a plurality of color control signals, one of which represents the blue component in the reproduced image; means for generating a correction control signal having given amplitude variation over a predetermined range and substantially zero amplitude at a reference location corresponding to nominal fleshtone hues; means for summing said correction control signal and said color control signal representing the blue component in the reproduced image whereby the resultant modified color control signal exhibits essentially uniform amplitude over said predetermined range about said nominal fleshtone reference location; and switch means for selectively activating said means for summing said correction control signal and said one color control signal.

Claim 3

An automatic hue control arrangement in accordance with claim 1 wherein said correction control signal has an essentially sinusoidal configuration and wherein said predetermined range over which said modified color control signal exhibits essentially uniform amplitude extends approximately 60* above and below said nominal fleshtone reference location.

Claim 4

An automatic hue control arrangement in accordance with claim 1 wherein said means for activating said summing means to modify said one color control signal comprises a viewer operated control switch.

Claim 5

An automatic hue control arrangement in accordance with claim 1 wherein said color control signals comprise respective (R-Y), (G-Y) and (B-Y) color-difference signals and wherein said means for generating said correction control signal includes means for selectively rectifying and amplifying a portion of said (R-Y) and (G-Y) color-difference signals, and means for summing said rectified and amplified (R-Y) and (G-Y) signal components.

Claim 6

An automatic hue control arrangement in accordance with claim 4 wherein the positive half cycle of the (R-Y) signal is rectified and the negative half cycle of the (G-Y) signal is rectified and wherein said rectified (R-Y) and (G-Y) signal components are selectively amplified to a level which upon being summed together results in a correction control signal having essentially zero amplitude at said nominal fleshtone reference location.

Claim 7

In a television receiver for reproducing color images and including signal processing circuitry for extracting and processing luminance information from a main carrier and color reference information from a modulated subcarrier, an automatic hue control arrangement for maintaining substantially true fleshtone hues, comprising in combination: circuit means for deriving from the color reference information a plurality of color control signals representative of primary red, blue and green color components in the reproduced image; amplifier means for amplifying respective red and green color control signals at a given level; rectifier means for rectifying the positive half cycle of said amplified red color control signal and for rectifying the negative half cycle of said amplified green color control signal; means for summing said rectified and amplified red and green color signal components to Form an essentially sinusoidal correction control signal having substantially zero amplitude occurring at a reference location corresponding to nominal fleshtone hues; and means for summing said correction control signal and said blue control signal to form a modified blue color control signal exhibiting essentially uniform response over a predetermined range encompassing said nominal fleshtone reference location.

Claim 8

In a television receiver for reproducing color images and including signal processing circuitry for extracting and processing luminance information from a main carrier and color reference information from a modulated subcarrier, an automatic hue control arrangement for maintaining substantially true fleshtone hues, comprising in combination: circuit means for deriving from the color reference information a plurality of color control signals representative of primary red, blue and green color components in the reproduced image; amplifier means for amplifying respective red and green color control signals at a given level; rectifier means for rectifying the positive half cycle of said amplified red color control signal and for rectifying the negative half cycle of said amplified green color control signal; means for summing said rectified and amplified red and green color signal components to Form an essentially sinusoidal correction control signal having substantially zero amplitude occurring at a reference location corresponding to nominal fleshtone hues; and means for summing said correction control signal and said blue control signal to form a modified blue color control signal exhibiting essentially uniform response over a predetermined range encompassing said nominal fleshtone reference location.

Claim 9

An automatic hue control arrangement in accordance with claim 6 wherein said amplifier means includes a pair of complementary transistors having input, output and common electrodes, and said rectifier means includes an additional pair of complementary transistors having input, output and common electrodes and biased at cut-off, said red and green color control signals being applied to said input electrodes of said amplifier transistors, said output electrodes of said amplifier transistors being connected to respective input electrodes of said rectifiers, and wherein said means for summing the rectified and amplified red signal components comprises a common junction terminal between said output electrodes of said rectifiers.

Claim 10

An automatic hue control arrangement in accordance with claim 7 wherein said amplifier, rectifier and summing is in integrated circuit form and wherein further means, including resistive matrix means, are provided for compensating for changes in the d-c output voltage level for said circuit means deriving said plurality of color control signals.

Claim 11

An automatic hue control arrangement in accordance with claim 7 wherein said amplifier for amplifying the red color control signal is a NPN transistor, said amplifier for amplifying the green color control signal is a PNP transistor, said rectifier for rectifying the amplified red signal component is a PNP transistor, and said rectifier for rectifying the amplified green signal component is a NPN transistor.