Pyroelectric sensor sensitivity enhanced by active hysteresis excitation

摘要

A ferroelectric/pyroelectric sensor that employs a technique for determining a charge output of a pyroelectric element of the sensor by measuring the hysteresis loop output of the element several times during a particular time frame for the same temperature. An external AC signal is applied to the pyroelectric element to cause the hysteresis loop output from the element to switch polarization. The frequency of the external AC signal is greater than the frequency of a chopper selectively applying a reference temperature and a scene temperature alternately to the pyroelectric element. Each time the chopper provides the reference temperature or the scene temperature to the element, the alternating external source covers multiple cycles so that the hysteresis loop output is switched multiple times for increased signal averaging. Because the shape and size of the loop is different for the reference temperature and the scene temperature, a comparison between the measured charge for both time periods can be provided to give a signal having an increased signal-to-noise ratio.