A laser interferometric displacement-measuring system was made operational for measuring roundness and waviness amplitude on highly reflective spherical surfaces. The laser interferometer was interfaced with a computer to provide semi-automated measure¬ments and data plots. The resolution of the interferometer is ±0.025 µm (±1.0 µin.) for waviness amplitude; however, the degree of temperature control of the overall system and the mechanical stability of the mechanism holding the sphere limit the resolution of the present system to ±0.13 µm (±5 µin.). The resolution of arc length along the surface over which this change in amplitude can be measured is approximately 16 µm (625 µin.), which is the diameter of the illuminated spot of laser light on the spherical surface. The non-contact interferometric measurements of roundness are in excellent agreement with conventional, stylus contact measurements on spheres as round as 0.33 µm (13 µin.) and as out-of-round as 10.2 µm (400 pin.).
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