Diffraction interferometer with coherent light source - has collimator, diffraction element, fringe detector and polarisation control device

摘要

The interferometer has a coherent light source (1) e.g. a CO2 laser, and a collimator (5) is placed in the path of the beam from the source which projects a parallel beam onto a diffraction system (7). A measurement beam and a reference beam are produced a sample to be controlled (9) being placed to receive the measurement beam and a means (8) being provided to reflect the measurement beam towards the diffraction beam. The interferometer has also a fringe detector (6) placed on the return path of both beams and the beam from the source is polarised by means of a device (10) such as a Dove prism which rotates the plane of polarisation.