Hybrid wedge plate-grating interferometer for collimation testing

A new type of collimation testing technique using a single wedge plate in conjunction with a dual-field grating has been described. Interference pattern produced by a wedge plate illuminated by the test beam is superposed on a grating to get moiré fringes. By using two different types of dual-field gratings, two testing configurations are obtained. These dual-field moiré patterns provide self-referencing and improved sensitivity in collimation testing. The principle of the proposed techniques and experimental results are presented. © 1993 Society of Photo-Optical Instrumentation Engineers.