Method and arrangement for the operation of pick-up tubes, preferably of the image-orthicon type

Claim 1

A METHOD OF OPERATING TELEVISION PICK-UP TUBES, PARTICULARLY TUBES OF THE IMAGE-ORTHICON TYPE, HAVING A STORAGE ELECTRODE AND WHEREIN A CHARGE PATTERN APPLIED TO SAID STORAGE ELECTRODE IS SCANNED BY A SCANNING BEAM OF SLOW ELECTRONS AND THE PICTURE SIGNAL IS PRODUCED BY THE BEAM CURRENT PROVIDED BY THE BEAM RETURNING FROM THE STORAGE ELECTRODE, COMPRISING, IN COMBINATION, THE STEPS OF: CONTROLLING THE INTENSITY OF THE SCANNING BEAM CURRENT DURING ONE PART OF ITS RETRACE TIME PERIODS IN SUCH A MANNER THAT SAID BEAM CURRENT INTENSITY ASSUMES A MEANS CONSTANT FIRST REFERENCE VALUE DIFFERENT FROM ZERO BUT SUBJECT TO HIGH FREQUENCY STATISTICAL FLUCTUATIONS RESULTING FROM DISCONTINUITIES OF SAID SCANNING BEAM CURRENT; INSERTING INTO THE PICTURE SIGNAL DURING SAID ONE PART OF SAID RETRACE TIME PERIODS A DIRECT CURRENT COMPONENT CORRESPONDING TO SAID MEAN CONSTANT FIRST REFERENCE VALUE UNDER THE CONTROL OF A FIRST CONTROL CIRCUIT HAVING A TIME CONSTANT LARGE ENOUGH SO THAT SAID HIGH-FREQUENCY STATISTICAL FLUCTUATIONS OF SAID FIRST REFERENCE VALUE ARE INTEGRATED; INSERTING DURING A DIFFERENT PART OF SAID RETRACE TIME PERIODS IN THE PICTURE SIGNAL PRODUCED BY SAID PICK-UP TUBE A NOISE-FREE SECOND REFERENCE VALUE OF CONSTANT LEVEL; AND RESTORING IN SAID PICTURE SIGNAL DURING SAID DIFFERENT PART OF SAID RETRACE TIME PERIODS A CONSTANT LEVEL BY SAID NOISE-FREE SECOND REFERENCE VALUE UNDER THE CONTROL OF A SECOND CONTROL CIRCUIT HAVING A TIME CONSTANT SMALL ENOUGH SO THAT LOWFREQUENCY NOISE SUPERIMPOSED ON THE PICTURE SIGNAL IS SUBSTANTIALLY COMPENSATED.

Claim 2

A METHOD OF OPERATING TELEVISION PICK-UP TUBES, PARTICULARLY TUBES OF THE IMAGE-ORTHICON TYPE, HAVING A STORAGE ELECTRODE AND WHEREIN A CHARGE PATTERN APPLIED TO SAID STORAGE ELECTRODE IS SCANNED BY A SCANNING BEAM OF SLOW ELECTRONS AND THE PICTURE SIGNAL IS PRODUCED BY THE BEAM CURRENT PROVIDED BY THE BEAM RETURNING FROM THE STORAGE ELECTRODE, COMPRISING, IN COMBINATION, THE STEPS OF: CONTROLLING THE INTENSITY OF THE SCANNING BEAM CURRENT DURING ONE PART OF ITS RETRACE TIME PERIODS IN SUCH A MANNER THAT SAID BEAM CURRENT INTENSITY ASSUMES A MEANS CONSTANT FIRST REFERENCE VALUE DIFFERENT FROM ZERO BUT SUBJECT TO HIGH FREQUENCY STATISTICAL FLUCTUATIONS RESULTING FROM DISCONTINUITIES OF SAID SCANNING BEAM CURRENT; INSERTING INTO THE PICTURE SIGNAL DURING SAID ONE PART OF SAID RETRACE TIME PERIODS A DIRECT CURRENT COMPONENT CORRESPONDING TO SAID MEAN CONSTANT FIRST REFERENCE VALUE UNDER THE CONTROL OF A FIRST CONTROL CIRCUIT HAVING A TIME CONSTANT LARGE ENOUGH SO THAT SAID HIGH-FREQUENCY STATISTICAL FLUCTUATIONS OF SAID FIRST REFERENCE VALUE ARE INTEGRATED; INSERTING DURING A DIFFERENT PART OF SAID RETRACE TIME PERIODS IN THE PICTURE SIGNAL PRODUCED BY SAID PICK-UP TUBE A NOISE-FREE SECOND REFERENCE VALUE OF CONSTANT LEVEL; AND RESTORING IN SAID PICTURE SIGNAL DURING SAID DIFFERENT PART OF SAID RETRACE TIME PERIODS A CONSTANT LEVEL BY SAID NOISE-FREE SECOND REFERENCE VALUE UNDER THE CONTROL OF A SECOND CONTROL CIRCUIT HAVING A TIME CONSTANT SMALL ENOUGH SO THAT LOWFREQUENCY NOISE SUPERIMPOSED ON THE PICTURE SIGNAL IS SUBSTANTIALLY COMPENSATED.