INTERFERENCE METHOD AND INTERFERROMETER FOR MEASURING SURFACE SHAPE OF PARABOLIC MIRROR

摘要

PURPOSE:To easily, surely and inexpensively measure the surface shape of a parabolic mirror by reflecting illumination light by the parabolic mirror to be measured and observing the interference fringe of the parallel reflected light reflected therefrom and standard light. CONSTITUTION:The beam from a laser light source 3 is split by a beam splitter BS1 to measure the surface shape of the parabolic mirror TM to be measured. One of the split beams is conducted to a divergent spherical wave generating optical system 4. The luminous flux is made into the divergent spherical wave by a microscopic objective lens Mo1 and a pinhole P1 and is reflected by the TM. The reflected flux arrives as the parallel reflected light at an observation lens OL. The other luminous flux is conducted to a parallel light forming optical system 5 and is made by a collimator lens CL to parallel light. The parallel light is reflected by a flat mirror FM and arrives at the lens OL. The parallel light and the parallel reflected light reflected from the TM overlap on each other but the light reflected from the TM deviates from the parallel light which is standard by receiving the influence of the ruggedness at the specular surface of the TM and therefore the interference fringe is generated. The surface shape of the TM is measured from the pitch of the interference fringe and the deviation quantity.