This book starts with a detailed presentation of the basic concepts of
photo transduction, modeling, evaluation, and optimization of Active Pixel
Sensors (APS). It continues with the description of APS design issues using
a bottom-up strategy, starting from pixels and finishing with image
processing systems. Various focal-plane image processing alternatives either
to improve imaging or to extract visual information are presented. The book
closes with a discussion of a completely non-traditional method for image
noise suppression that utilizes floating-gate learning techniques. The final
three chapters in fact provide a glimpse into a potential future of CMOS
imaging and image processing, where concepts gleaned from other
disciplines, such biological vision, are combined with alternative mixedsignal
computation circuits to perform complex visual information
processing and feature extraction at the focal plane. This benefit of CMOS
imaging and image processing is still largely unexploited by the commercial
sector.
The first chapter reviews the background knowledge and concepts of
silicon-based photo transduction, and introduces relevant concepts from
semiconductor physics. Several silicon-based photo detectors are examined,
including the photodiode and the photogate. This chapter also describes the
operation of the charge-coupled device (CCD) imager, the predominant
technology available for digital imaging. CCD technology is compared with
a promising alternate technology, the APS imager. In addition, the functional
performances of several basic pixel structures are compared by considering
them as communication channels and determining their ability to convey
information about an incident optical signal. At 30 frames per second,
information rates are similar for charge-, voltage-, and current-mode pixels.