INVESTIGATION OF A DIFFRACTION-GRATING INTERFEROMETER FOR USE IN AERODYNAMIC RESEARCH

A low-cost interferometer that is easy to adjust and has a large field of view is described. This instrument, which is based on a prin-ciple discovered by Kraushaar, uses small diffraction gratings to produce and recombine separate beams of light. The usual two-parabolic-mirror schlieren system can be converted inexpensively to a diffraction-grating interferometer. Experimental data are presented to verify the ability of the instru-ment to provide valid and reliable measurements of air density. Photo-graphs of the flow in a supersonic cascade tunnel are included to indi-cate the quality of the interferograms obtained