Optical, flat
A flat, transparent piece of glass, generally of fused quartz, with one or both principal surfaces polished to within a few millionths of an inch of a true plane. It is used in conjunction with a monochromatic light source to measure the flatness of precision finished surfaces, and to determine the distance and parallelism between precision finished surfaces by comparison with known standards. In operation the flat is superimposed, reference surface downward, on the parts under test and when illuminated by monochromatic light the rays reflected from the reference surface are either reinforced or neutralized by the rays reflected from the surface under test producing interference bands which reveal any variations in the thickness of the film of air between surface under test and the flat. Excludes optical parallels.
NSN 5960-01-489-1510
NSN 6320-01-136-8505
NSN 5920-01-462-1950
NSN 5998-01-517-4714
NSN 5935-01-329-9531
NSN 6150-01-439-2608
NSN 2925-01-314-7916
NSN 6620-01-610-5081
NSN 5925-00-767-0284
NSN 6135-01-026-9960
NSN 5990-01-517-7848
NSN 5935-01-442-8689