Thermal Imaging
Infrared Detection Devices
The pyroelectric effect associated with ferroelectric materials has been used for a long time to detect thermal variations in sensors exposed to infrared radiation. Generally, these detectors rely upon sensing the changes in the charge that is stored on the ferroelectric capacitor, or pixel, a charge that changes with temperature due to incident infra-red radiation. “Passive” sensing of this charge typically requires a mechanical chopper and often cooling.
“Active” sensing of this charge is a development patented by Symetrix and Delphi Corporation. Active sensing of the pixel charge is enabled by cycling the device in voltage along its ferroelectric hysteresis and referencing this value to a “blind eye” pixel. This produces enhanced receptivity and eliminates the need for a chopper. Most importantly, producing the pixel array is much like the ferroelectric memory array: familiar materials, all planar processing and monolithic. Fundamental patents have issued.
A very low cost, high resolution infra-red detector will have a wide impact on thermal imaging applications such as medical diagnostics, night vision, remote temperature (fire) sensing, perimeter security, toxic gas detection and many others.
Pyroelectric Pixel for Active Sensing