The applicability of the digital holography to grinded surfaces shape measurements is experimentally examined with regard to the surface micro-roughness of brittle materials (optical glass). Multi-wavelength phase shifted digital holographic interferometry (holographic contouring) is used and its performance is analyzed. Holographic contouring is a great candidate for the precise shape measurement technique, which can be applied to the iterative manufacture process of optical elements. Optical surface artifacts with different radii of the spherical (convex and concave) shapes were prepared with different micro-roughness. Their optical surfaces were then holographically recorded using a designed setup. Two different measures were selected to estimate the quality of the holographic recording: first, the intensity profile of the reconstructed surface deviation as a consequence of the micro-roughness decrease, where the shape of the intensity profile develops as the surface is altering from strongly diffusive to almost specular; second, the correlation of the phase fields (surfaces shapes), which were holographically recorded using two light beams of different wavelengths. In this situation, the correlation function decreases with an increase in the noise amount in data. The presented preliminary results indicate that the multi- wavelength holographic contouring can be used for surface measurements of high-quality polished and nearly specular surfaces. On the other hand, the application of holographic contouring to polished surface measurement still represents a challenging task and remains unresolved even with the multidirection illumination.

Date Published: 7 January 2015
PDF: 7 pages
Proc. SPIE 9442, Optics and Measurement Conference 2014, 94420Q (7 January 2015); doi: 10.1117/12.2176006

Published in SPIE Proceedings Vol. 9442:
Optics and Measurement Conference 2014
Jana Kovačičinová; Tomáš Vít, Editor(s)