Transparent wafer center finder

A method and apparatus for locating the center of a substrate are provided. The substrate-positioning system uses an array of visible light sources to illuminate the substrate and its edges. The light sources are non-laser in nature and typically emit in the visible spectrum. The light sources are typically LEDs so that the individual elements may be switched-on or switched-off extremely rapidly, which allows for multiple images to be taken using different light sources at any given substrate rotation position. The substrate-positioning system further includes an image sensor array with the ability to process data rapidly, which allows for the digitization (quantization) of each pixel being viewed. Algorithms analyze the values for patterns and determine the true edge position at each rotational angle of the substrate. The systems and methods described herein are able to locate the center of various types of substrates composed of different materials and/or edge types.