| 摘要 |
<p>PURPOSE:To realize a highly accurate shape measuring apparatus, by dividing laser beam into two by a beam splitter to form interference fringes different in a phase after the reference beam from a reference plane anda the beam to be referred to from a surface to be measured are superposed. CONSTITUTION:The laser beam emitted from He-Ne laser 30 are linear polarized beams inclined at an angle of 45 deg. to the optical axis of lambda/4 plates 21, 32. These laser beams pass through the lambda/4 plate 32 to be synthesized in to beam in phase relation in two directions crossing at a right angle and the synthesized beam is projected to a beam splitter 1 to be separated into reflected beams and transmitted beams. The transmitted beams impinge against a surface 3 to be measured to be reflected therefrom and the reflected beams are projected to the lambda/4 plate 21 but impinge against a reference plane 2 to be reflected therefrom and superposed by the beam splitter 1 to become interference beam. The interference fringe obtained by a circular polarizing plate 33 is condensed by an imaging lens 34 to be formed into an image on an area sensor 35 to generate an electric signal corresponding to the quantity of beams at every beam receiving element unit. Because the effect of the shape error of the lambda/4 plate in the beam path of reference beam is not generated in phase change, the measurement of a shape can be performed with high accuracy.</p> |
