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Proceedings Paper

Readout circuit with pixel-level analog-to-digital conversion
Author(s): Wenxiang Gan; Ruijun Ding; Yunzhi Ni
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Paper Abstract

Pixel level on-focal-plane analog to digital conversion(ADC) promises many advantages including high performance and low power consumption. In this paper we argue that CMOS technology scaling will make pixel level ADC increasingly popular. Then we introduce four existing techniques for pixel level ADC. The first is an over sampling technique which uses a one bit first order sigma delta modulator for each pixel to directly convert photo charge to bits, consists of an integrator, a one bit DAC and a clocked comparator. The second technique is Nyquist rate multi-channel-bit-serial(MCBS) ADC. The technique uses special successive comparisons to convert the pixel voltage to bits. The third technique bases on a simple and robust pulse frequency modulation(PFM) scheme that can convert the photocurrent of photodetectors to proportional pulse frequency. The fourth is a software-controlled ADC, which utilize a algorithm, takes a desired photocurrent quantization scale to output bits. Each pixel contains a programmable digital processing element which directly controls the behavior of the photo detector with software. These four techniques are analyzed and compared according to their advantages, disadvantages and suitable application area. Finally we mention our current and future works with one of these techniques.

Paper Details

Date Published: 10 January 2005
PDF: 12 pages
Proc. SPIE 5640, Infrared Components and Their Applications, (10 January 2005); doi: 10.1117/12.572157
Show Author Affiliations
Wenxiang Gan, Shanghai Institute of Technical Physics (China)
Ruijun Ding, Shanghai Institute of Technical Physics (China)
Yunzhi Ni, Shanghai Institute of Technical Physics (China)

Published in SPIE Proceedings Vol. 5640:
Infrared Components and Their Applications
Haimei Gong; Yi Cai; Jean-Pierre Chatard, Editor(s)

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