Adjustable gamma controller

A controllable video signal gamma corrector for a video signal comprising:

• first and second serially coupled amplifying stages, each amplifying stage having respective signal inputs and outputs, said video signal being applied to said signal input of said first amplifying stage;
• a signal translating stage having a nonlinear signal input/output characteristic coupled between said signal output of said first amplifying stage and said signal input of said second amplifying stages for imparting a gamma characteristic to the video signal applied to it from said signal output of said first amplifying stage;
• a gain control feedback path coupled between the output of said second amplifying stage and a gain-control input of said first amplifying stage to control the gain of said first amplifying stage;
• and
• black level control means associated with each of said first and second amplifying stages for maintaining the level of blanking portions of said video signal at a predetermined black level;
• and
• a source of a gamma control signal for supplying a gamma control signal to the black level control means associated with said first amplifying stage to control the amount of gamma correction provided by said signal translating stage.

An adjustable gamma controller for a video signal comprising:

• signal combining means for adding a pulse having a level representative of the white level of said video signal to said video signal during a blanking interval thereof;
• first and second serially-coupled amplifying means, each having respective signal inputs and outputs, said video signal including said pulse being applied to said input of said first amplifying means;
• nonlinear signal translating means coupled between said signal output of said first amplifying means and said signal input of said second amplifying means for imparting a gamma characteristic to the video signal applied to it from the signal output of said first amplifying means;
• feedback means coupled to the signal output of said second amplifying means for sampling the video signal supplied from its output during the occurrence of said pulse for generating a gain-control signal which is applied to control the gain of said first amplifying means for maintaining said predetermined level of the video signal provided at said signal output of said second amplifier means at a given amplitude;
• black level control means associated with each of said first and second amplifying means for imparting respective blanking levels to said video signal during said blanking interval;
• gamma control signal generating means for applying a gamma control signal to the black level clamp associated with said first amplifying means for controlling its blanking level, variation of said gamma control signal changing the amount of gamma correction provided by said nonlinear signal translating means.

An adjustable gamma controller for a video signal comprising:

• first and second serially-coupled amplifying means, each having respective signal inputs and outputs, said video signal being applied to said input of said first amplifying means, said first and second amplifying means each comprising respective signal multiplying means;
• nonlinear signal translating means coupled between said signal output of said first amplifying means and said signal input of said second amplifying means for imparting a gamma characteristic to the video signal applied to it from the signal output of said first amplifying means;
• feedback means coupled to the signal output of said second amplifying means for sampling the video signal supplied from its output when said video signal is at a predetermined level for generating a gain-control signal which is applied to control the gain of said first amplifying means for maintaining said predetermined level of the video signal provided at the signal output of said second amplifier means at a given amplitude;
• and
• gamma control signal generating means for applying a gamma control signal to said second amplifying means for controlling its gain, variation of said gamma control signal changing the amount of gamma correction provided by said nonlinear signal translating means.