Television receiver circuit means for stabilizing black level on scenes of low average brightness and for suppressing black level on high brightness scenes

Claim 1

AN IMAGE-REPRODUCING SYSTEM IN A TELEVISION RECEIVER ADAPTED TO RECEIVE A TELEVISION SIGNAL INCLUDING AN IMAGE-REPRESENTATIVE SIGNAL HAVING ALTERNATING-CURRENT COMPONENTS REPRESENTATIVE OF VARIATIONS IN INSTANTANEOUS BRIGHTNESS AND A DIRECT-CURRENT COMPONENT REPRESENTATIVE OF AVERAGE SCENE BRIGHTNESS WHICH MAY VARY FROM SCENE TO SCENE, AND HAVING A LEVEL INTENDED TO CORRESPOND TO BLACK IN THE REPRODUCED IMAGE, COMPRISING: MEANS FOR SUPPLYING SAID IMAGE-REPRESENTATIVE SIGNAL; MEANS, INCLUDING A CATHODE-RAY TUBE, FOR REPRODUCING THE IMAGE; AND MEANS FOR COUPLING SAID IMAGE SIGNAL TO SAID CATHODE-RAY TUBE AND FOR CONTROLLING THE GRID-TO-CATHODE VOLTAGE OF SAID TUBE IN ACCORDANCE WITH VARIATIONS IN THE AVERAGE SCENE BRIGHTNESS OF SAID IMAGE-REPRESENTATIVE SIGNAL TO STABILIZE BLACKLEVEL IN THE REPRODUCED IMAGE ON SCENES OF LOW AVERAGE BRIGHTNESS AND TO SUPPRESS BLACK LEVEL IN THE REPRODUCED IMAGE ON SCENES OF HIGH AVERAGE BRIGHTNESS.