Abstract

Interferometric testing of spherical parts is limited in accuracy by the reference surface quality; λ/20 PV is typical. Certification of spherical surfaces to high accuracy is typically achieved using a technique that involves multiple measurements of the surface (two sphere test)^1,2. This test is time intensive and requires very precise alignment of the part under test, particularly for fast surfaces. In addition, long radius surfaces may be impossible to test using the two sphere test from a practical standpoint, simply because of the length of cavity required. In order to circumvent these issues, we have examined the accuracy of storing surface maps of the reference surface for a transmission sphere and subtracting this from subsequent measurements using that sphere. The reference map is obtained by absolute certification of the reference.

© 1992 Optical Society of America