| 摘要 |
<p>In order to investigate the flatness of a surface an optical flat is positioned upon a surface under investigation, and substantially monochromatic light is projected in a direction substantially perpendicular to the plane of the optical flat so as to set up an observable interface pattern. The interference pattern set up is viewed from a viewing position opposed to the upper face of the optical flat and in close juxtaposition to the location of projection of the substantially monochromatic light. The illumination source from which the light is projected is preferably in annular configuration, the interference pattern being viewed through an axial aperture. The apparatus is typically provided with a support arrangement and means for traversing above the surface under investigation.</p> |
