Photogrammetric flatness test for reflecting surfaces

A simplified photogrammetric technique for determining the shape of reflecting surfaces such as optical components, film supports, and photographic emulsions has been adapted to the testing of plane surfaces. The twenty-five by twenty-five cm surface of the grid plate of the Zeiss precision stereocomparator is used as a reflecting test object surface. Other objects may be tested, but they must be reflective; large surfaces can be examined by the method; the photograph is taken in a short interval of time, and many image recordings can be made in succession.