| 摘要 |
A scanning laser beam is directed in a circular scanning pattern, perpendicular to the surface of a part that moves across the scan pattern. Reflected light received solely from part edges or other surface discontinuities is compared with a number of preselected threshold levels. When reflection intensity attains any one of the selected threshold levels, an event is triggered, and the beam position at the time of the event, together with the intensity level triggering the event, are recorded, so as to provide information limited to the part edges and other surface discontinuities.
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