CMOS active pixel sensors (APS) have performance competitive with charge-coupled device (CCD) technology, and offer advantages in on-chip functionality, system power reduction, cost, and miniaturization. This paper discusses the requirements for CMOS image sensors and their historical development, CMOS devices and circuits for pixels, analog signal chain, and on-chip analog-to-digital conversion are reviewed and discussed.

CMOS image sensors: electronic camera-on-a-chip

In this article, we provide a basic introduction to CMOS image-sensor technology, design and performance limits and present recent developments and future directions in this area. We also discuss image-sensor operation and describe the most popular CMOS image-sensor architectures. We note the main non-idealities that limit CMOS image sensor performance, and specify several key performance measures. One of the most important advantages of CMOS image sensors over CCDs is the ability to integrate sensing with analog and digital processing down to the pixel level. Finally, we focus on recent developments and future research directions that are enabled by pixel-level processing, the applications of which promise to further improve CMOS image sensor performance and broaden their applicability beyond current markets.

CMOS image sensors

An imaging device formed as a monolithic complementary metal oxide semiconductor integrated circuit in an industry standard complementary metal oxide semiconductor process, the integrated circuit including a focal plane array of pixel cells, each one of the cells including a photogate overlying the substrate for accumulating photo-generated charge in an underlying portion of the substrate, a readout circuit including at least an output field effect transistor formed in the substrate, and a charge coupled device section formed on the substrate adjacent the photogate having a sensing node connected to the output transistor and at least one charge coupled device stage for transferring charge from the underlying portion of the substrate to the sensing node.

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Active pixel sensor with intra-pixel charge transfer

CMOS image sensors: Electronic camera-on-a-chip

Single substrate device is formed to have an image acquistition device and a controller. The controller on the substrate controls the system operation.

/pdf/cmos-active-pixel-sensor-type-imaging-system-on-a-chip-1pw7w4xxhm.pdf

CMOS active pixel sensor type imaging system on a chip

The basic principle of operation of each bit in a matrix of image detectors is described, together with the derivation of appropriate operating formulas. The necessary circuitry to make a functional two-dimensional array is also described, including the scanning circuitry integrally constructed with the photodetector matrix. The necessary design considerations for operation of the matrix are discussed in the context of the currently operating 10-by-10 array. Extension of the principles to larger arrays is outlined in the two modes of array scanning considered, with special reference to spatial noise problems. The paper concludes with reference to other applications of the basic principle, such as card reading.

P.J.W. Noble

Papers

Self-scanned silicon image detector arrays