Circuit for detecting the ratio of intensities of the color components of light

Claim 2

A color component ratio detection circuit comprising: means for generating a current proportional to the intensity of a first color component of light; and a voltage generating means including a photoconductive element which detects the intensity of a second color component of the light and electrically connected such that the current generated by said current generating means flows therethrough, said voltage generating means generating, across said photoconductive element, a voltage proportional to the ratio between the intensities of said first and second color components.

Claim 3

A color component ratio detection circuit as defined in claim 1, wherein said current generating means includes a photoelectric element which detects the intensity of said first color component, and said voltage generating means further includes an operational amplifier having inverting and non-inverting input terminals and an output terminal and a first constant voltage source connected to said non-inverting input terminal, said photoconductive element being connected between said output terminal and said inverting input terminal as a negative feedback resistor with said photoelectric element being connected to said inverting input terminal such that said current flows into said photoconductive element, whereby said voltage across said photoconductive element appears at said output terminal.

Claim 4

A color component ratio detection circuit as defined in claim 2, wherein said current generating means further includes a second constant voltage source and said photoelectric element consists of a photoconductive element connected in series with said second constant voltage source.

Claim 5

A color component ratio detection circuit as defined in claim 3, wherein the voltage generated by said second constant voltage source is higher than that generated by said first constant voltage source and both said voltages are set to be positive.

Claim 6

A color component ratio detection circuit as defined in claim 1, wherein said photoconductive element constitutes said voltage generating means to which said current generating means feeds said current directly.

Claim 7

A color component ratio detection circuit as defined in claim 5, wherein said current generating means includes a constant current source for generating a substantially constant current proportional to the intensity of said first color component.

Claim 8

A color component ratio detection circuit as defined in claim 6, wherein said constant current source includes a photovoltalic element connected in series with said photoconductive element.

Claim 9

A color component ratio detection circuit as defined in claim 6, wherein said constant current source includes a photoconductive element for detecting the intensity of said first color component, a first transistor whose base and collector are connected with each other to form a diode and whose collector is connected with said photoconductive element for detecting the intensity of said first color component, and a second transistor whose base and emitter are connected with the base and emitter of said first transistor respectively and whose collector is connected with said photoconductive element for detecting the intensity of said second color component.

Claim 10

A color component ratio detection device as defined in claim 6, wherein said constant current source includes a photoconductive element for detecting the intensity of said first color component, a first transistor whose collector is connected with said photoconductive element for detecting the intensity of said first color component, a constant voltage source, an operational amplifier having an input terminal connected to a junction between the collector of said first transistor and said photoconductive element for detecting the intensity of said first color component, another input terminal connected to said constant voltage source and an output terminal connected to the base of said first transistor, and a circuit means for producing a substantially constant current commensurate with the voltage across the base and emitter of said transistor as said current proportional to the intensity of said first color component, said circuit means being connected with said current into said photoconductive element for detecting the intensity of said second color component.

Claim 11

In a video camera which includes an image or pickup tube for generating an image signal, a color separation circuit for separating first and second color component signals from said image signal, a first gain-adjustable amplifier which amplifies said first color component signal, a second gain adjustable amplifier for amplifying said second color component signal and an encoder for converting said first and second color component signals fed from said first and second gain-adjustable amplifiers into video signals, an automatic color temperature adjusting device comprising: means for generating a current proportional to the intensity of said first color component; and a voltage generating means including a photoconductive element which detects the intensity of said second color component and electrically connected such that the current generated by said current generating means flows therethrough, said voltage generating means generates, across said photoconductive element, a voltage proportional to the ratio between intensities of said first and second color components and being connected with said first and second gain adjustable amplifiers such that the gains of said first and second gain adjustable amplifiers are adjusted in accordance with said voltage to achieve automatic white balance.

Claim 12

In a video camera which includes an image or pickup tube for generating an image signal, a color separation circuit for separating first and second color component signals from said image signal, a first gain-adjustable amplifier which amplifies said first color component signal, a second gain adjustable amplifier for amplifying said second color component signal and an encoder for converting said first and second color component signals fed from said first and second gain-adjustable amplifiers into video signals, an automatic color temperature adjusting device comprising: means for generating a current proportional to the intensity of said first color component; and a voltage generating means including a photoconductive element which detects the intensity of said second color component and electrically connected such that the current generated by said current generating means flows therethrough, said voltage generating means generates, across said photoconductive element, a voltage proportional to the ratio between intensities of said first and second color components and being connected with said first and second gain adjustable amplifiers such that the gains of said first and second gain adjustable amplifiers are adjusted in accordance with said voltage to achieve automatic white balance.