Double-Resolution Interferometer for Rough or Reflecting Surfaces
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
A telecentric system is arranged in the interferometer between the object and a flat mirror to bring polarized beams to interference that have experienced multiple reflections at the same object point; two fringe patterns with g/2 and g/4 separation, respectively, are thus obtained. Testing rough surfaces by known interferometric methods requires oblique beam incidence that reduces the measurement resolution and leads to undesired shadow regions. An interferometer set-up without these drawbacks is shown in Fig. 1; the exit beam of a laser is expanded by lens combination EX, passes beam splitter SP1, polarizer P1 and is deflected partly by beam splitter SP2 through lenses L1 and L2 to the surface of object 0.