CMOS digital cameras need new figures of merit

C omplementary-metal-oxide-semiconductor (CMOS), active-pixel-sensor (APS), digital camera-on-a-chip technology has progressed rapidly in the six or so years since it was invented by scientists at the NASA Jet Propulsion Laboratory (Pasadena, CA; see Fig. 1). While performing the same general image-capture function as its predecessor, the charge-coupled device (CCD), this highly integrated "syst~m on a chip" produces new types of figures of merit for comparing performance. Some of these figures of merit can be compared to CCD imaging systems by tracing a path from the photons in a scene to the bits coming out of the camera on a chip.