Circuit arrangement for color point adjustment

Claim 2

A transmitting circuit for red, green, and blue color signals comprising means for producing from said color signals a luminance signal; means for modifying said luminance signal by applying adjustably equal amplitude and opposite polarity signals proportional to said red and blue signals to said luminance signal; and matrix means for forming red and blue color difference signals from said red, blue, and luminance signals; whereby the color of skin can be changed without changing the intensity of said green color signal or white point.

Claim 3

A circuit as claimed in claim 1 wherein said matrix means comprises amplifier means for producing a signal that is the difference between said red and blue color signals, said signal being adjustable in magnitude and sign and; means for applying said difference signal to said luminance signal.

Claim 4

A circuit for receiving luminance, and red and blue color difference signals comprising matrix means for producing from said signals a green color difference signal; means for modifying said green color difference signal by applying thereto equal amplitude and opposite polarity red and blue color difference signals, whereby the color of skin can be changed without changing the white point or the green color intensity.

Claim 5

A circuit for receiving luminance, and red and blue color difference signals comprising matrix means for producing from said signals a green color difference signal; means for modifying said green color difference signal by applying thereto equal amplitude and opposite polarity red and blue color difference signals, whereby the color of skin can be changed without changing the white point or the green color intensity.

Claim 6

A circuit as claimed in claim 3 wherein said matrix comprises a potential divider comprising a first resistor coupled to receive said red color difference signal, and a second resistor coupled to ground and to said first resistor; a second potential divider comprising a third fixed resistor coupled to receive said blue color difference signal, and a fourth resistor coupled to ground and to said third resistor; a third potential divider comprising a fifth variable resistor coupled to the junction of said first and second resistors, and a sixth resistor coupled to the junction of said third and fourth resistors and to said fifth resistor; and an output resistor means coupled to ground and to the junction of said fifth and sixth resistors for providing said green color difference signal; whereby for a given value of the third resistor and a nominal adjustment for the reproduction of the skin color and the green color intensity the normal values of the remaining potential divider and output resistors are proportioned as follows:

Claim 7

A circuit as claimed in claim 4 wherein said fifth resistor is variable between a value which is small relative to the normal value and a value which is at least equal to 10 times the normal value.

Claim 8

A circuit as claimed in claim 4 wherein said fifth resistor is logarithmically variable.

Claim 9

A circuit as claimed in claim 4 wherein the luminance of the green color signal comprises a fixed value and said second potential divider, said sixth resistor and said output resistor comprise an equivalent fixed potential divider.

Claim 10

A transmitting circuit for first, second, and third color signals comprising means for producing from said color signals a luminance signal; means for subtracting from said luminance signal an adjustable amplitude signal proportional to said third color signal; means for adding to said luminance signal different fractions of two signals that are proportional to said adjustable amplitude signal and to said first and second color signals respectively; and matrix means for producing first and second color difference signals from said luminance and said first and second color signals respectively; whereby the intensity of said third color can be varied without changing skin color or the white point.

Claim 11

A transmitting circuit for first, second, and third color signals comprising means for producing from said color signals a luminance signal; means for subtracting from said luminance signal an adjustable amplitude signal proportional to said third color signal; means for adding to said luminance signal different fractions of two signals that are proportional to said adjustable amplitude signal and to said first and second color signals respectively; and matrix means for producing first and second color difference signals from said luminance and said first and second color signals respectively; whereby the intensity of said third color can be varied without changing skin color or the white point.

Claim 12

A circuit as claimed in claim 8 wherein said fractions are computed from: wherein B1 + B2 are proportional to said fractions, SG 0.7997, and Sb 0.6387.

Claim 13

A circuit for receiving luminance and red and blue color difference signals comprising matrix means for producing a green color difference signal from said received signals; and means for adding to said green color difference signal different proportions of said red and blue color difference signals, whereby the green intensity can be reduced without changing skin color or the white point.

Claim 14

A circuit for receiving luminance and red and blue color difference signals comprising matrix means for producing a green color difference signal from said received signals; and means for adding to said green color difference signal different proportions of said red and blue color difference signals, whereby the green intensity can be reduced without changing skin color or the white point.