| 摘要 |
The apparatus can be constructed by modifying the design of a conventional optical disc player to accept the increased size and weight of the glass master over that of an optical disc. A heliumneon laser beam is directed by a focussing system to a spot on the under surface of the glass master and, if the surface is perfect, the narrow reflected beam is blocked and obsorbed by the mask. If there is a defect in the glass master surface, then scattering of the reflected light occurs and is collected by the lens and focused onto a photodetector.
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