| 摘要 |
At least two laser beams (11, 12, 13) with different wavelengths are focussed on a rough surface (10) from different directions. The scattered light is separated by filters into the different wavelengths and the patterns are observed separately by detectors, e.g. by camera. They are analyzed to allow the velocity gradients of the surface in different directions to be deduced. The incident light beams converge through a lens system (7, 8, 9) in the immediate vicinity of the surface (10). Separation of the scattered light into different wavelengths can be carried out by mirrors, or metallic or dielectric layers with appropriate reflection or transmission properties. Separation can take after beam splitters feeding separate cameras or at different regions on the detector surface of a single camera.
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