| 摘要 |
PURPOSE:To raise a measuring accuracy by providing a radiation light source for generating rediation light by which two frequencies of measuring light and reference light are stabilized, and an optical system for converting this radiation light to rediation light having a prescribed spot size and a spreading angle. CONSTITUTION:In case when a frequency of measuring light and a frequency of reference light are denoted as f1 and f2, respectively, light emitted from a Zeeman laser 1 of oscillation frequencies f1, f2 is divided into two polarizing directions, namely, the light of f2 by which an electric field is polarized in the direction vertical to the paper surface, and the light of f1 by which it is polarized in the direction parallel to the paper surface, by a lambda/4 plate 2. Subsequently, a part of the light is separated by a beam splitter 3, and a beat frequency (f1-f2) is detected by a photodetector 4. According to such a method, an almost aspherical shape can be measured by non-contact and with a very high accuracy.
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