Description:
Researchers at the University of Virginia have developed a novel idea for IR sensor system design where the detector is suspended away from electrical and thermal connections. Sensitivity of such a system is expected to be an order of magnitude better than the current IR sensors.
Infrared sensors have become widely used in many detection systems, most notably for night vision applications. The sensitivity of an infrared sensor is limited, however, by thermal losses in the detector itself. Typically, an infrared sensor consists of a suspended platform coated with material sensitive to infrared radiation (IR). As IR strikes the platform, some physical change occurs in the coating, usually to the electrical resistance. Electrical contact to the detector requires a mechanical connection to the coating, allowing heat to flow out of the platform of the sensor during the measurement and subsequently lowering its sensitivity.
The present invention is a novel idea for making the thermal resistance of the mechanical suspension and electrical contacting used in IR sensors as high as possible. By levitating the IR sensitive platform so that it is completely isolated from the substrate during radiation absorption, the detector element is decoupled from the substrate, eliminating thermal conduction losses. As a result, the sensitivity of the sensor is greatly increased.
Readout of the levitated detector temperature is accomplished by changing the levitation control potentials to temporarily force the detector in contact with the readout circuit electrodes. The change in detector properties arising from the IR is quickly read before appreciable heat is lost from the detector. After remaining in the readout position for a short time, the detector is quenched to the substrate temperature, preparing the detector for a new absorption cycle with no "memory" of the previous cycle. This mode of operation offers significant benefits that reduce system overhead. Furthermore, the detector requires only gain correction to compensate for minor perturbations in the detector thermal coefficient thus lowering the overall system cost.
Suspension of IR sensors promises temperature measurements an order of magnitude more sensitive than current technology. This increased sensitivity is highly attractive to a variety of applications, including infrared cameras, night vision goggles and scientific instrumentation.
Issued U.S. patent 6,900,440
