Interferometric measuring device for detecting shape, roughness of distance of object surface has beam from modulation interferometer fed to optical measuring probe with angled light output surface

摘要

The measuring device has a modulation inteferometer in which the light beam from a coherent light source is split into 2 partial beams, provided with a relative frequency shift or phase shift before re-combining and coupling to a measuring probe via an optical fibre. The measuring probe has a probe optical fibre (3.1,3.2) with an anti-reflective coating (3.22) adjacent its output end and an angled output surface (3.4), directing a measuring beam onto the object surface, the reflected measuring beam combined with a reflected reference beam after reflection from a reference plane, with evaluation of the phase difference between the detected optical signals. The angled output surface extends at an angle of at least 46 degrees to the normal to the measuring probe optical axis (3.5).