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Proceedings Paper

Effect of pixel active area shape on imaging quality of CMOS active pixel sensor
Author(s): Hong Fan; Wujun Xu; Chengliang Wang
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Paper Abstract

The CMOS active pixel sensor (APS) technology is of interest for space-borne instruments, such as low power imagers for micro-spacecraft, star trackers and machine vision for space micro-rovers. It is significant to evaluate image quality after the performance parameters of imaging system using CMOS APS are validated. The most fundamental of evaluating imaging quality is modulation transfer function (MTF). The system MTF is the multiplication of optics transfer function, detector transfer function and electronics transfer function. In CMOS APS arrays, the pixel area is constructed of two functional parts. The first part, which has a certain geometrical shape, is the sensing element itself: the active area that absorbs the illumination energy within it and turns that energy into charge carriers. The second part is the control circuitry required for readout of this charge. The ratio between the active area and the total pixel area is referred to as the fill factor (FF), which in APS is less than 100% (in contrast to CCDs where the FF can approach 100%). The preferred shape of the pixel active area is a square. However, designing the active area as a square can reduce the FF. Since the FF influences the signal and signal-to-noise ratio (SNR), it is preferred to keep it as high as possible. Theoretical analysis of the MTF for the active area shape is performed for an L shaped active area (most commonly used). And the effects of pixel active area shapes on imaging quality of CMOS active pixel sensor are analyzed.

Paper Details

Date Published: 24 January 2008
PDF: 6 pages
Proc. SPIE 6829, Advanced Materials and Devices for Sensing and Imaging III, 68291S (24 January 2008); doi: 10.1117/12.757477
Show Author Affiliations
Hong Fan, Donghua Univ. (China)
Wujun Xu, Donghua Univ. (China)
Chengliang Wang, Shanghai Institute of Technical Physics (China)

Published in SPIE Proceedings Vol. 6829:
Advanced Materials and Devices for Sensing and Imaging III
Anbo Wang; Yimo Zhang; Yukihiro Ishii, Editor(s)

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