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Proceedings Paper

CMOS readout circuit design for infrared image sensors
Author(s): Libin Yao
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Paper Abstract

The infrared imaging system has been developed for more than 50 years, from the early stage the scanned imaging system using single unit detector to imaging system using focal plane detector arrays. For focal plane array detectors, the readout circuit is used to read the photon detector signal out. Charge coupled device had been used for the readout of the focal plane array detectors and currently CMOS technology is used. In this paper, readout circuit design using CMOS technology for infrared focal plane array detectors is reviewed. As an interface between the detector and the image signal processing circuits, readout circuit is a critical component in the infrared imaging system. With the development of the CMOS technology, the readout circuit is now moving into the CMOS technology. With the feature size scaling down, the readout cell size is reduced, which enable us to integrate more complex circuits into the readout cell. From the system point of view, different requirements and specifications for the CMOS readout circuit are analyzed and discussed. Different readout circuit parameters such as injection efficiency, dynamic range, noise, detector biasing control, power consumption, unit cell area, etc are discussed in details. Performance specifications of different readout cell structures are summarized and compared. Based on the current mirroring integration readout cell, a fully differential readout cell is proposed. The injection efficiency of this proposed readout cell is very close to unity and the detector biasing voltage is close to zero. Moreover, the dynamic range of the proposed readout cell is increased and the rejection on interference is improved because of the fully differential structure. All these are achieved without much power consumption increasing. Finally, a full digital readout circuit concept is introduced. By employing a current controlled oscillator, the photocurrent is converted to frequency and integrated in digital domain and the final output is digital signal.

Paper Details

Date Published: 6 August 2009
PDF: 10 pages
Proc. SPIE 7384, International Symposium on Photoelectronic Detection and Imaging 2009: Advances in Imaging Detectors and Applications, 73841B (6 August 2009); doi: 10.1117/12.835520
Show Author Affiliations
Libin Yao, National Univ. of Singapore (Singapore)

Published in SPIE Proceedings Vol. 7384:
International Symposium on Photoelectronic Detection and Imaging 2009: Advances in Imaging Detectors and Applications
Kun Zhang; Xiang-jun Wang; Guang-jun Zhang; Ke-cong Ai, Editor(s)

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