| 摘要 |
Optical apparatus for measuring the topographic properties of a surface uses a beam of coherent radiation which is split by a beam splitter (2) into a reference beam and a probe beam. The probe beam at is modulated by a Bragg cell which is switched at two frequencies ( omega 1, omega 2). A detector (6) recombines the components of the probe beam after reflection to produce a plurality of tone bursts the phase differences of which correspond to variations in the surface topography.
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