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 5975-01-653-1724
NSN 6145-00-604-6916
NSN 6610-00-454-6635
NSN 6150-00-520-5510
NSN 5965-01-154-4524
NSN 6150-01-328-2651
NSN 5999-01-238-7778
NSN 6240-01-591-1357
NSN 6105-01-047-7566
NSN 5910-01-183-3370
NSN 6135-00-461-3590
NSN 5935-01-255-3203