Chroma tracking circuit

Abstract

Abstract A FEEDBACK CIRCUIT TO PREVENT LOSS OF RELATIVE COLOR SATURATION AT INCREASED ILLUMINATION LEVELS IN A ONE TUBE COLOR CAMERA TELEVISION SYSTEM IS DISCLOSED COMPRISING MEANS FOR SENSING VARIATIONS IN THE ABSOLUTE MAGNITUDE OF THE LUMINANCE SIGNAL, AND MEANS RESPONSIVE THERETO FOR VARYING THE GAIN IMPARTED TO THE LUMINANCE SIGNAL OR TO THE CHROMINANCE SIGNAL RELATIVE TO THE OTHER SIGNAL. IN ONE PREFERRED EMBODIMENT THE VARIABLE GAIN IS ACHIEVED BY PROVIDING A VARIABLE IMPEDANCE COMPRISING FIRST AND SECOND PARALLEL BRANCHES, THE FIRST OF WHICH PRESENTS A RELATIVELY LOW IMPEDANCE TO THE CHROMINANCE SIGNAL FREQUENCY RANGE AND A RELATIVELY HIGH IMPEDANCE TO THE LUMINANCE SIGNAL FREQUENCY RANGE AND THE OTHER OF WHICH HAS AN IMPEDANCE WHICH IS SUBSTANTIALLY FREQUENCY IMDEPENDENT AND IS INTERMEDIATE THE RELATIVELY LOW AND RELATIVELY HIGH IMPEDANCES CHARACTERISTIC OF THE FIRST BRANCH. A SHUNT MEANS IN THE FORM OF A FIELD EFFECT TRANSISTOR IS IN PARALLEL WITH THESE BRANCHES AND IS GATED BY A CONTROL SIGNAL INDICATIVE OF THE LUMINANCE SIGNAL MAGNITUDE SO THAT WHEN THE FIELD EFFECT TRANSISTOR CONDUCTS, THE OVER-ALL IMPEDANCE OF THE PARALLEL COMBINATION DECREASED MORE RAPIDLY FOR SIGNALS IN THE LUMINANCE SIGNAL FREQUENCY RANGE THAN FOR SIGNALS IN THE CHROMINANCE SIGNAL FREQUENCY RANGE THEREBY VARYING THE RELATIVE GAIN OF THE LUMINANCE SIGNALS TO THE CHROMINANCE SIGNALS.

Inventors

• 👤 J Durbin
• 👤 Aiuto J D

Bibliographic Details