Method of adjusting the current intensity of an electron beam in a pickup tube and television camera system suitable therefor

A television camera system comprising:

• a television pickup tube having a target, said tube producing a picture signal;
• means for generating an electron beam in the pickup tube, said electron beam having a beam current;
• means for repeatedly scanning the electron beam across the target at a fixed scanning rate, each complete scan of the target being a scan cycle;
• a beam current blanking circuit, said beam current blanking circuit when in a first state suppressing the electron beam current as the electron beam is scanned across a selected area of the target over a selected number of one or more consecutive scan cycles in order to integrate charge generation at the selected area of the target, said beam current blanking circuit when in a second state allowing the beam current to remain at its nonsuppressed setting when scanning the selected area of the target over one scan cycle so as to read out the charge inegrated at the selected area of the target;
• means for alternately switching the beam current blanking circuit between its first and second states;
• means for adjusting the nonsuppressed beam current setting;
• and
• a picture signal peak detector for determining the lowest beam current which produces the maximum picture signal from the selected area of the target.

A method of adjusting the beam current of the scanning electron beam in a television pickup tube having a target, said tube producing a picture signal, said method comprising the steps of:

• repeatedly scanning the electron beam across the target at a fixed scanning rate, each complete scan of the target being a scan cycle;
• suppressing the electron beam current as the electron beam is scaned across a selected area of the target over a selected number of one or more consecutive scan cycles in order to integrate charge generation at the selected area of the target, said selected area of the target being less than the entire area of the target;
• reading out the charge integrated at the selected area of the target by scanning the selected area of the target over one scan cycle with the beam current at its nonsuppressed setting;
• repeating the steps of suppressing and reading out;
• and
• adjusting the nonsuppressed beam current setting to the lowest nonsuppressed beam current which produces the maximum picture signal from the selected area of the target.