Adjustable Responsivity Built into Microbolometers
In an air-bridge microbolometer, support beams hold the thermal infrared detector material away from the substrate, thus reducing its thermal conductance. An extremely large signal will cause the detector output to exceed the range of the readout CMOS or even damage the detector itself. However, researchers from the University of Minnesota in Minneapolis may have found a way to overcome these problems by reducing the overall responsivity of the thermal detectors when they are presented with a large signal.
They used MEMS technology to snap down the support beams to the substrate, effectively changing their thermal conductance when the detected signal exceeded certain limits. In the July 15 issue of Applied Physics Letters, they report a two-orders-of magnitude drop in responsivity, but predict that a drop as large as five orders of magnitude is possible with commercial manufacturing techniques.
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