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Proceedings Paper

Automated full-field range OPD and MTF measurement bench for automotive objective benchmark
Author(s): W. Boucher; M. Yonnet; D. Brahmi; A. Gascon; M. Deprez; B. Wattellier; O. Lavergne
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Paper Abstract

We present a metrology bench used to benchmark the optical quality of lenses used in automotive applications. These lenses have a wide field of view, typically larger than 180° and fast numerical apertures (F/2). Lenses are compared in terms of OPD and MTF. For this aim, interferometric solutions would require double-passing the lens. Between two field positions, it would be necessary to realign the reference sphere. This is not compatible with the requested high measurement throughput. Therefore wave front sensing is the best solution to this problem because it is able to characterize lenses in single pass configurations. We chose to measure the transmitted wave front with a QuadriWave Lateral Shearing Inferferometer wave front sensor placed directly after the focal plane. This technology is best suited in this case because it has the unique ability to measure fast diverging beams with high accuracy. It can also accept the large tilt angles due to the lens non telecentricity. Because the information needed for lens comparison is the OPD in the exit pupil, the wave front is then back-propagated to it thanks to an innovative ray-trace algorithm. This algorithm is also able to deduce the aperture transmission to take into account vignetting effects that appear at the field edges. Finally the MTF is simulated from the OPD and the pupil function. This bench is fully automated to rapidly benchmark a large number of lenses in their complete field of view. We characterized the bench according to the ISO 5725 standard. Its precision was tested with commercial lenses whereas trueness was assessed with calibrated lenses. The accuracy on MTF was found to be below 1% over the whole field of view.

Paper Details

Date Published: 12 October 2015
PDF: 9 pages
Proc. SPIE 9633, Optifab 2015, 96331U (12 October 2015); doi: 10.1117/12.2195805
Show Author Affiliations
W. Boucher, PHASICS S.A. (France)
M. Yonnet, PHASICS S.A. (France)
D. Brahmi, PHASICS S.A. (France)
A. Gascon, PHASICS S.A. (France)
M. Deprez, PHASICS S.A. (France)
B. Wattellier, PHASICS S.A. (France)
O. Lavergne, Renault Technocentre (France)

Published in SPIE Proceedings Vol. 9633:
Optifab 2015
Julie L. Bentley; Sebastian Stoebenau, Editor(s)

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