Signal processing circuit

Claim 2

A signal processing circuit for a color video camera, comprising: photoelectric conversion means for producing a luminance signal, a red color signal and a blue color signal from incoming light signal; first and second low-pass filters for allowing said red color signal and said blue color signal to pass therethrough, respectively; a first arithmetic operation circuit for combining the output signal from said first low-pass filter, the output signal from said second low-pass filter and said luminance signal to thereby produce a pseudo-green color signal having a low frequency component which corresponds to that of a green color signal; first, second and third gamma-correction circuits for processing said pseudo-green color signal, the output signal from said first low-pass filter and the output signal from said second low-pass filter, respectively; and a second arithmetic operation circuit for combining the output signals from said first, second and third gamma-correction circuits, respectively, thereby to produce a gamma-corrected luminance signal.

Claim 3

A signal processing circuit according to claim 1, further comprising first and second color difference circuits for subtracting the gamma-corrected luminance signal from said second arithmetic operation circuit from the output signals from said second and third gamma-correction circuits, respectively, to produce difference output signals.

Claim 4

A signal processing circuit according to claim 2, further comprising color encoder means for receiving the gamma-corrected luminance signal from said second arithmetic operation circuit and the difference output signals from said first and second color difference circuits for providing a gamma-corrected color output signal.

Claim 5

A signal processing circuit according to claim 3, wherein said first and second low-pass filters pass signals having frequencies lower than 500 KHz.

Claim 6

A signal processing circuit according to claim 1, wherein said first and second low-pass filters pass signals having frequencies lower than 500 KHz.

Claim 7

A signal processing circuit for a color video camera, comprising: photoelectric conversion means for producing a luminance signal, a red color signal and a blue signal from an incoming light signal; first, second and third low-pass filters for allowing said red color signal, said blue color signal and said luminance signal to pass therethrough, respectively; a high-pass filter for allowing said luminance signal to pass therethrough; a first arithmetic operation circuit for combining output signals from said first, second and third low-pass filters to thereby produce a low frequency green color signal of a low frequency band corresponding to that of a green color signal; first, second and third gamma correction circuits for processing said low frequency green color signal, the output signal from said first low-pass filter and the output signal from said second low-pass filter, respectively; a second arithmetic operation circuit for combining the output signals from said first, second and third gamma-correction circuits, respectively, to thereby produce a gamma-corrected low frequency luminance signal; and an adder circuit for adding the output signal from said second arithmetic operation circuit to the output signal from said high-pass filter to produce a gamma-corrected luminance signal.

Claim 8

A signal processing circuit for a color video camera, comprising: photoelectric conversion means for producing a luminance signal, a red color signal and a blue signal from an incoming light signal; first, second and third low-pass filters for allowing said red color signal, said blue color signal and said luminance signal to pass therethrough, respectively; a high-pass filter for allowing said luminance signal to pass therethrough; a first arithmetic operation circuit for combining output signals from said first, second and third low-pass filters to thereby produce a low frequency green color signal of a low frequency band corresponding to that of a green color signal; first, second and third gamma correction circuits for processing said low frequency green color signal, the output signal from said first low-pass filter and the output signal from said second low-pass filter, respectively; a second arithmetic operation circuit for combining the output signals from said first, second and third gamma-correction circuits, respectively, to thereby produce a gamma-corrected low frequency luminance signal; and an adder circuit for adding the output signal from said second arithmetic operation circuit to the output signal from said high-pass filter to produce a gamma-corrected luminance signal.

Claim 9

A signal processing circuit according to claim 6, further comprising first and second color difference circuits for subtracting the gamma-corrected low frequency luninance signal from said second arithmetic operation circuit from the output signals from said second and third gamma-correction circuits, respectively, to produce difference output signals.

Claim 10

A signal processing circuit according to claim 7, further comprising color encoder means for receiving the gamma-corrected luminance signal from said adder circuit and the difference output signals from said first and second color difference circuits for producing a gamma-corrected color output signal.

Claim 11

A signal processing circuit according to claim 8, wherein said first, second and third low-pass filters pass signals having a frequency lower than 500 KHz and said high-pass filter passes signals having a frequency higher than 500 KHz.

Claim 12

A signal processing circuit according to claim 6, wherein said first, second and third low-pass filters pass signals having a frequency lower than 500 KHz and said high-pass filter passes signals having a frequency higher than 500 KHz.