Uncooled IR focal plane arrays: worldwide review and state-of-the-art at ULIS

Abstract

Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Developments are focused on improving the sensitivity to enable the possibility to manufacture high performance small pixel pitch detectors or radiometric detectors with internal "cold" shield. Commercial infrared is now a well-established business with several competitors. We review the state-of-art of the main competitors and we describe the work which is being done in France.After the development of an amorphous silicon based uncooled microbolometer technology, LETI and ULIS, a subsidiary of SOFRADIR and CEA, are now working to make easier IRFPA integration into equipment in order to address a very large market. Achievement of this goal needs the integration of advanced functions on the focal plane and the decrease of manufacturing cost of IRFPA by decreasing the pixel pitch and simplifying the vacuum package. We present the new design for readout circuits taking into account the user needs by introducing analog to digital converter on the chip to provide 12 bits video digital output. We present also the introduction and the characterization of radiometric device obtained from 320 x 240 uncooled microbolometer arrays with a f/1.4 limited field of view. Then, we present the new ceramics microbolometer package developed to decrease the package cost of versatile smaller devices like the 160 x 120 pixels with a pitch of 35 µm.

A Method of Measurement of Minimum Resolvable Temperature Difference as a Function of Magnification and Defocusing of a Thermal Camera

“…Standardowa procedura pomiaru parametru NETD polega na zarejestrowaniu promieniowania emitowanego z technicznego ciała czarnego dla dwóch różnych wartości temperatury (bądź częściej dwóch ciał czarnych o różnych wartościach temperatury promiennika). Parametr NETD najczęściej dotyczy średniej wartości wszystkich detektorów matrycy i wyznaczany jest wg zależności [1]:…”