Optical viewing system for simultaneously viewing indicia located on top and bottom surfaces of a substrate

摘要

An optical system is disclosed that permits the viewing and reading of indicia, such as OCR scribes and/or barcodes, disposed on either side of a substrate, such as a semiconductor wafer, with a single camera. In one embodiment of the invention, optical elements are selectively positioned such that images of indicia fields disposed on either side of a substrate can be viewed (at the same magnification) whenever the substrate is in a given orientation, or such that images of indicia fields disposed on both sides of the substrate may be viewed at the same magnification, simultaneously. Optical paths may be folded to reduce the overall size of the optical viewing system.