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10 October 2001 Progress toward high-performance thermopile imaging arrays
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Thermopiles are uncooled, broadband detectors that require no chopper or temperature stabilizer. Their wide operating- temperature range, lack of temperature stabilization, and radiometric accuracy make thermopiles well suited for some space-based scientific imaging applications. These detectors may also offer advantages over bolometers for night vision. Previous work at JPL has produced thermopile linear arrays with D* values over 109 cmHz1/2/W by combining high- performance thermoelectric materials Bi-Te and Bi-Sb-Te with bulk micromachining processes. To date, however, 2-D thermopile arrays have demonstrated only moderate performance. The purpose of the present work is to improve thermopile 2-D arrays substantially by combining Bi-Te and Bi-Sb-Te thermoelectric materials with a unique pixel structure and low-noise readout circuitry. The initial goal is a 128 X 128 array with a single multiplexed analog output stream, with system D* values (including readout noise) of 109 cmHz1/2/W, and with a focal-plane power dissipation of 20 mW. 100 micrometers square detectors have been demonstrated with D* values of 2 X 108 cmHz1/2/W and response times of 4 ms. Models predict D* values well over 109 cmHz1/2/W for optimized detectors. Modeling of a preliminary readout design shows that, for the expected detector resistance of 100 kΩ, the total noise will be 50% higher than the detector Johnson noise. CMOS test chips containing front-end circuits presently display a noise about 2.5 times higher than modeled and a power dissipation of 0.6 μW per pixel.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Marc C. Foote and Stephen D. Gaalema "Progress toward high-performance thermopile imaging arrays", Proc. SPIE 4369, Infrared Technology and Applications XXVII, (10 October 2001);

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