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Issue No. 03 - May/June (1998 vol. 18)
ISSN: 0272-1732
pp: 8-15
Since the early 1990s, there has been an explosion of activity in the area of CMOS image sensors. Up until recently, the dominant and nearly only solid-state image sensor technology was the charge-coupled device (CCD). However, most microprocessors, logic circuits, ASICs (application-specific integrated circuits) and memory circuits are based on CMOS technology. Now it appears that CMOS will be used for image sensors in a rapidly expanding sphere of applications. Several important factors have contributed to the emergence of CMOS image sensors at this time rather than 10-20 years ago. The primary factor is a recent demand by customers for portable, low power, miniaturized digital imaging systems. A second important factor is that present-day CMOS offers submicron feature sizes and low defect and contamination levels, respectively permitting cost-effective pixel sizes and low junction leakage (or dark) current. In addition, threshold voltage control and uniformity is stable and reproducible. The third important factor is that new circuit techniques have been invented or have been adopted from CCD signal processing that permit both low noise and high-dynamic-range imaging that is competitive with the best CCDs. This includes the development of the active pixel sensor technology and column-parallel signal processing circuits for temporal and fixed-pattern noise reduction. In this article, we review CMOS image sensor technology basics, look at the state of the art, and try to examine where the technology may be leading us.
charge-coupled devices, signal processing, image sensors, CMOS, digital cameras

E. R. Fossum, "Digital Camera System on a Chip," in IEEE Micro, vol. 18, no. , pp. 8-15, 1998.
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