| 摘要 |
The invention provides apparatus and methods for fast non-contact measuring distance between an optical head and an optically rough surface with improved accuracy. The technique involves spatial filtering of a speckle pattern formed when the surface is scanned by a focused laser beam with the predefined speed. In one embodiment, the apparatus includes several independent photo-receivers for receiving properly selected portions of the spatially filtered light and a signal processor for measuring the temporal frequency of electrical signals from these photo-receivers and further calculation of z- distance according to the predefined equations. In another embodiment, the apparatus provides multiple scanning of the surface by the focused laser beam with simultaneous displacement of the scan by the predefined distance.
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