| 摘要 |
A semiconductor processing workpiece support which includes a detection subsystem that detects whether a wafer or other workpiece is present. The preferred arrangement uses an optical beam emitter and an optical beam detector mounted along the back side of a rotor which acts as a workpiece holder. The emitted beam passes through the workpiece holder and is reflected by any workpiece present in the workpiece holder. The preferred units include both an optical emitter and pair of detectors. The detection is preferably able to discriminate on the basis of the angle of the reflected beam, so that a portion of the beam reflected by the workpiece holder is not considered or minimized.
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