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Proceedings Paper

Photon-to-digital photodiode imaging array
Author(s): William J. Mandl
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Paper Abstract

MOSAD©, Multiplexed OverSample Analog to Digital conversion, is a low power on focal plane analog to digital, A/D, process that places an oversample A/D at each pixel site. Two designs for a visible light staring array were developed with this approach. One used a silicon photo diode and the other used a photo gate for detection. The array was designed with a 320 X 240 format with the pixels placed on 16 micron centers. There are a total of 76,800 A/D's on the chip. The device is a monolithic integrated circuit that includes the sensors, A/D's and readout circuitry. A production 1.2 micron CCD/CMOS process was used in it construction. The A/D uses charge well switching at the pixel to convert the accumulated analog signal to digital data. There was negligible impact on the pixel area due to the A/D such that a fill factor of 73% was achieved with front side illumination for both approaches. At 400 samples per second, measured on chip power consumption is under 10 milliwatts. Noise measurements at sample rates from 400 samples per second to 1,600 samples per second were taken for both parts. It was found that the photo gate noise performance was four times better than the photo diode. At a nominal 28 times oversample, the photo diode obtained 8 to 9 bits performance and the photo gate achieved 10 to 11 bits. Nonuniformity variation was below the noise floor. No explanation for the difference in noise performance has yet been determined. This development was sponsored by NASA under a SBIR program.

Paper Details

Date Published: 10 October 2001
PDF: 12 pages
Proc. SPIE 4369, Infrared Technology and Applications XXVII, (10 October 2001); doi: 10.1117/12.445323
Show Author Affiliations
William J. Mandl, Amain Electronics Co. Inc. (United States)

Published in SPIE Proceedings Vol. 4369:
Infrared Technology and Applications XXVII
Bjorn F. Andresen; Gabor F. Fulop; Marija Strojnik, Editor(s)

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