Digital camera system on a chip

of activity in the area of CMOS image sensors has taken place. Up until recently, the dominant, and nearly the only, solid-state image sensor technology was the charge-coupled device (CCD). However, most microprocessors, logic circuits, ASICs, and memory circuits are based on CMOS technology. Now CMOS can 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 to 20 years ago. The primary factor consists of recent demand 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, 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, new circuit techniques that have been invented or adopted from CCD signal processing, permits both low noise and high dynamic-range imaging that is competitive with the best CCDs. This includes the development of active pixel sensor technology and column-parallel, signal-processing circuits for temporal and fixed-pattern noise reduction. Using technology originally developed at NASA Jet Propulsion Laboratory, we formed Photobit to further develop and commercialize CMOS-technology systems on a chip. The digital camera on a chip has applications not only in aerospace but also in a large array of commercial products like cameras. To get a better handle on digital camera systems on a chip, let’s review CMOS image sensor technology basics, look at the state of the art, and try to determine where the technology may be leading us.