Focal-Plane Analog Image Processing

Abstract

In this chapter, three systems for imaging and visual information processing at the focal plane are described: current-mode, voltage-mode and mixed-mode image processing. It is demonstrated how spatiotemporal image processing can be implemented in the current and voltage modes. A computation-on-readout (COR) scheme is highlighted; this scheme maximizes pixel density but still allows multiple processed images to be produced in parallel. COR requires little additional area and access time compared to a simple imager, and the ratio of imager to processor area increases drastically with scaling to smaller-feature-size CMOS technologies. In some cases, it is necessary to perform computations in a pixel-parallel manner while still retaining the imaging density and low-noise properties of an APS imager. Hence, an imager that uses both current-mode and voltage-mode imaging and processing is presented. The mixed-mode approach has some limitations, however, and these are described in detail. Three case studies are used to show the relative merits of the different approaches for focal-plane analog image processing.