1 October 1990 Homogeneity testing of optical glass using holographic interferometry
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Abstract
The degree of spatial variations of refractive index within a melt or blank is evaluated considering two paranieters: optical homogeneity and striae. The variations called striae correspond to strong inhoinogeneities of a very local nature. They produce a change on the propagation direction of light that is detected using schlieren techniques. Optical homogeneity corresponds to smooth spatial variations of the refractive index that produce negligible variations on the direction of propagation of light through the glass sample. Optical homogeneity is tested by transmission using classical interferomnetry (Ref . 1 , 2 , 3) . The wavefront transmitted through the sample is compared interferometrically with a reference wavefront. Hence conditions imposed on the quality of the optics used in these instruments are strong. The sample itself must be well polished or convenientely tested to separate its surface deformations from the contribution due to optical homogeneity. In this work it is presented the analysis of an holographic technique applied to the assessment of the honogeneity of optical glass plates. It is used an inunersion device to avoid the need for separating surface contributions. Optical homogeneity can be determined from a single interferogran, against the two (Ref . 3) , or four (Ref . 1 , 2) needed when using classical interferometry. It is shown here that this holographic interferornetry method has a higher accuracy.
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Diana Tentori, Diana Tentori, } "Homogeneity testing of optical glass using holographic interferometry", Proc. SPIE 1327, Properties and Characteristics of Optical Glass II, (1 October 1990); doi: 10.1117/12.22517; https://doi.org/10.1117/12.22517
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