Readout circuit with pixel-level analog-to-digital conversion

Wenxiang Gan; Ruijun Ding; Yunzhi Ni

doi:10.1117/12.572157

10 January 2005 Readout circuit with pixel-level analog-to-digital conversion

Wenxiang Gan, Ruijun Ding, Yunzhi Ni

Proceedings Volume 5640, Infrared Components and Their Applications; (2005) https://doi.org/10.1117/12.572157
Event: Photonics Asia, 2004, Beijing, China

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.

Citation Download Citation

Wenxiang Gan, Ruijun Ding, and Yunzhi Ni "Readout circuit with pixel-level analog-to-digital conversion", Proc. SPIE 5640, Infrared Components and Their Applications, (10 January 2005); https://doi.org/10.1117/12.572157

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