Signal processing system for chopper type pyroelectric camera

Abstract

A signal processing system is disclosed for a pyroelectric camera having a mechanical chopper in the optical path for causing information sensed by the camera to appear as dynamic information. The pyroelectric camera includes a pyroelectric vidicon tube which senses thermal energy emitted by a target and provides an electrical output signal indicative of the received thermal information. The output signal developed by the pyroelectric vidicon tube includes a relatively large pedestal signal component that is established during flyback due to secondary electron generation and a slightly wider but relatively small pedestal signal that is established due to differences in temperature sensed by the pyroelectric vidicon tube, which pedestal signal is timewise aligned with the relatively large pedestal signal generated due to secondary electron generation. Removal of the pedestal signals avoids saturation of the system amplifiers and limiting of the dynamic range of the camera by thus enabling processing of only the signal components indicative of sensed thermal energy from the target. Background flicker is also eliminated, or reduced, by adding signals of adjacent fields.