A simple system geometry using a low power laser has been designed to measure the surface curvature of a lens or a mirror or the refractive index of a slab of a transparent material by using the Fresnel reflection from its surfaces. By comparing our measurements of the surface curvature to those using a precision spherometer, we found this method accurate to ±0.1 mm for curvatures from 25 to 75 mm. If the thickness of a parallel plate can be measured, this technique can determine the refractive index of the plate without resorting to demounting or cutting a sample to be measured. Measurements of fused and crystalline quartz flats determined the refractive indices of the samples to ±0.001. The application of this technique to in situ measurements of optical systems and its limitations will be discussed.

Date Published: 29 January 1989
PDF: 5 pages
Proc. SPIE 0966, Advances in Fabrication and Metrology for Optics and Large Optics, (29 January 1989); doi: 10.1117/12.948062

Published in SPIE Proceedings Vol. 0966:
Advances in Fabrication and Metrology for Optics and Large Optics
Jones B. Arnold; Robert E. Parks, Editor(s)