29 January 1989 Non-Contact Measurements Of Refractive Index And Surface Curvature
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Abstract
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.
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Donald C O'Shea, Shawn A. Tilstra, "Non-Contact Measurements Of Refractive Index And Surface Curvature", Proc. SPIE 0966, Advances in Fabrication and Metrology for Optics and Large Optics, (29 January 1989); doi: 10.1117/12.948062; https://doi.org/10.1117/12.948062
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KEYWORDS
Sensors

Refractive index

Reticles

Beam splitters

Reflection

Microscopes

Spatial filters

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