Active pixel sensors (APS) 
are in fact imagers in which
each pixel incorporates some minimum circuitry to improve the image
acquisition characteristics. CMOS based APS have been studied since
1980's by Japanese electronic industries, as an alternative for CCD
cameras. Recently, the new market for multimedia cameras has created
an atmosphere of struggle toward re-establishing the same concepts.
Unlike vision chips where some high level image processing is performed at the pixel level, APS only try to capture the image with a focus toward improving the image quality using standard processes. In this regard APS can be regarded as less smart sensors.
APS have extensive applications for astronomical and space exploration applications, in addition to recent interest in multimedia applications, for video and still-image imaging. APS can achieve low noise, large dynamic range, high speed, random access to pixels, and so on. Most of the circuits used in APS can well be used in vision chips, because the size and complexity of the circuits that are used in APS are less than those used for smart vision sensors. Also, the higher dynamic range, lower noise, or higher speed brought by additional circuits in APSs are as essential for vision chips. Some of techniques used for enhancing the performance of APS can also be applied to vision chips.