| 摘要 |
Phase is modulated in a grazing incidence interferometer by modulating the incidence angle and spacing the test surface far enough from the reference surface so that the incidence angle modulation changes the phase relationship between the interferring beam reflected from the test surface and the reference beam reflected from the reference surface substantially more than it changes the sensitivity of the interferometer to surface variations between the reference and test surfaces. The preferred way of accomplishing this is with tiltable mirror 15 modulating the incidence angle slightly relative to prism 11 with its reference surface 12 and test surface 13 spaced from reference surface 12 in interferometer 10. An electromagnetic element 16 such as a galvanometer is preferred for tilting mirror 15.
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