PMAC: A Polygon Matching Chip

The recognition of polygons in 3-D space is an important task in robot vision. Advances in VLSI technology have now made it possible to implement inexpensive, efficient and very fast custom designs. The authors have earlier proposed a class of VLSI architectures for this computationally intensive task, which makes use of a set of local shape descriptors for polygons which are invariant under affine transformations, i.e. translation, scaling, rotation and orthographic projection from 3-D to any 2-D plane. This paper discusses the design and implementation of PMAC, a prototype for polygon matching, as a custom CMOS VLSI chip. The recognition procedure is based on the matching of edge-length ratios using a simplified version of the dynamic programming procedure commonly employed for string matching. The matching procedure also copes with partial occlusions of polygons. The implemented architecture is systolic and fully utilizes the principles of pipelining and parallelism in order to obtain high speed and throughput.