Calibration of interferometer for testing surface profile of cylindrical sample

摘要

The calibration involves placing a plane mirror (5) in the optical chamber normally occupied by the sample cylinder during testing. The mirror plane occupies the focal line of the interferometer, about which it is checked and about which it can be tilted. The interferometer has a beam-splitter (2) and a reference mirror (3), with a cylinder objective occupying the test arm. Coherent light e.g. a from a laser (1) is incident on the focal line for at least two different tilt positions of the plane mirror and is returned at least partially by the mirror into the interferometer, and detected by a camera (6).The path difference of the light between the reference and the wavefront passing via the plane mirror is measured for each tilt position depending on the position within the wavefront existing after superimposition. The measured path difference and the plane mirror's linearity deviations along the focal line are combined mathematically to determine the interferometer errors.