Optical test bench for high precision metrology and alignment of zoom sub-assembly components

F. Leprêtre; E. Levillain; B. Wattellier; P. Delage; D. Brahmi; A. Gascon

doi:10.1117/12.2031635

15 October 2013 Optical test bench for high precision metrology and alignment of zoom sub-assembly components

F. Leprêtre, E. Levillain, B. Wattellier, P. Delage, D. Brahmi, A. Gascon

Proceedings Volume 8884, Optifab 2013; 88841M (2013) https://doi.org/10.1117/12.2031635
Event: SPIE Optifab, 2013, Rochester, New York, United States

Abstract

Thales Angénieux (TAGX) designs and manufactures zoom lens assemblies for cinema applications. These objectives are made of mobile lens assemblies. These need to be precisely characterized to detect alignment, polishing or glass index homogeneity errors, which amplitude may range to a few hundreds of nanometers. However these assemblies are highly aberrated with mainly spherical aberration (>30 μm PV). PHASICS and TAGX developed a solution based on the use of a PHASICS SID4HR wave front sensor. This is based on quadri-wave lateral shearing interferometry, a technology known for its high dynamic range. A 100-mm diameter He:Ne source illuminates the lens assembly entrance pupil. The transmitted wave front is then directly measured by the SID4- HR. The measured wave front (WF_meas) is then compared to a simulation from the lens sub-assembly optical design (WF_design). We obtain a residual wave front error (WF_manufactured), which reveals lens imperfections due to its manufacturing. WF_meas=WF_design+(WFE_radius+WFE_glass+WFE_polish)=WF _design + WF_manufactured The optical test bench was designed so that this residual wave front is measured with a precision below 100 nm PV. The measurement of fast F-Number lenses (F/2) with aberrations up to 30 μm, with a precision of 100 nm PV was demonstrated. This bench detects mismatches in sub-assemblies before the final integration step in the zoom. Pre-alignment is also performed in order to overpass the mechanical tolerances. This facilitates the completed zoom alignment. In final, productivity gains are expected due to alignment and mounting time savings.

Citation Download Citation

F. Leprêtre, E. Levillain, B. Wattellier, P. Delage, D. Brahmi, and A. Gascon "Optical test bench for high precision metrology and alignment of zoom sub-assembly components", Proc. SPIE 8884, Optifab 2013, 88841M (15 October 2013); https://doi.org/10.1117/12.2031635

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