The pyroelectric vidicon: Pyroelectric materials for operation at cathode potential in a "Hard" tube

Summary form only given, as follows. Pyroelectric vidicon camera tubes have been developed and their performance has been reported for thermal imaging in the 8-14 micron band. Present tubes operate with a triglycine sulphate (TGS) sensing layer. These tubes possess some undesirable characteristics partly due to the incompatibility of TGS with the vacuum environment and partly due to the method of generating the positive pedestal current required for cathode potential operation. The pedestal is generated either as an ion current in a soft tube or by secondary electrons produced on publishing the beam to anode potential. Both methods may result in a tube of limited lifetime with cathode or target deterioration. This work reports an alternative method of pedestal generation and surveys suitable materials. The pedestal is leaked through the pyroelectric target itself. The conductivity must satisfy both charge storage and pedestal generation. Such materials have been run in a hard vacuum where the magnitude of the pedestal is simply set with the signal plate bias. Thus these materials operate in such a way as to overcome lifetime problems and in addition to provide a direct "plug-in" replacement tube for the photoconductive tube in a standard camera.