Interferometric measuring device for measuring e.g. surface roughness, of object, has reference interferometer coupled with modulation interferometer, where mechanical coupling is provided between interferometers with backlash on reversal

摘要

The device (1) has a radiation source (30) and an arrangement formed from a modulation interferometer (10) and a reference interferometer (20) coupled with the modulation interferometer. A mechanical coupling is provided between the reference interferometer and the modulation interferometer with a backlash on reversal (40). A beam input to the modulation interferometer is split into two partial beams by a beam splitter. A measuring interferometer measures a form and/or roughness of a surface downstream to the modulation interferometer at a beam delivery. An independent claim is also included for a method for comparing an optical path difference in an interferometric measuring device.