Methods of operating pyroelectric camera tubes

The method of operating a pyroelectric camera tube having an electron beam emitting cathode, a target, scanning mechanism causing the electron beam repetitively to scan the target, a control grid controlling the electron beam and a gas in the interior space of the tube, which comprises the steps of:

• a. periodically applying line blanking pulses to the cathode to ensure that the cathode is positive with respect to the target so that the electron beam does not land on the target during line flyback;
• and b. applying a positive-going pulse to the grid during each line flyback whereby an increased pedestal potential is produced at the scanning side of said target due to increased electron beam current and consequent increased gas ionization.

A circuit arrangement including a pyroelectric camera tube having an envelope, an electron beam emitting cathode, a target, scanning means for causing the electron beam repetitively to scan said target, a control grid controlling the electron beam, and a quantity of ionizable gas in said envelope;

• means for maintaining the target at near the electron beam emitting cathode potential applied during forward scanning;
• means for periodically applying a positive line blanking pulse to said cathode to ensure that the cathode is positive with respect to the target so that the electron beam does not land on the target during line flyback;
• and pulse generating means for applying a positive-going pulse to said grid during each line flyback, which positive-going pulse is of an amplitude greater than the positive pulse applied to the cathode so as to increase the electron beam current during flyback, thereby increasing gas ionization to produce an increased pedestal potential.