Patent ID: 8139231

Claim:
A vision system for determining a positional relationship between a photovoltaic device wafer and a printing element, wherein the photovoltaic device wafer is on a platen that has an aperture there through with an edge of the photovoltaic device wafer extending across the aperture, and wherein the printing element is located on a remote side of the photovoltaic device wafer from the platen, said vision system comprising: a source of ultraviolet light; a diffuser assembly for diffusing the ultraviolet light from the source, and directing diffused light into the aperture in the platen and toward the photovoltaic device wafer; a camera for producing an electrical image from light received from the aperture in the platen, wherein some of the received light was reflected by the photovoltaic device wafer and some of the received light was reflected by the printing element.