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Abstract

A semiconductor wafer and magnetic disk edge detection system having a sensor unit comprising a dual beam light source spatially oriented so that the beams focus and converge at a single point external to the sensor unit, and dual light detectors spatially oriented to allow detection of light reflected from the edges of the wafers and disks even where the angle of incidence of the light onto the edge deviates significantly from the perpendicular. The sensor unit works in operative combination with a scanning motion means to move the sensor across the edges of the wafers or disks to be detected, typically by attachment of the sensor unit to a linear motor or a robotic arm, or alternately, by manually detecting the edges of the wafers and disks.

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First Claim