Interferometric testing of soft contact lenses

Gregory A. Williby; Daniel G. Smith; Richard B. Brumfield; John E. Greivenkamp

doi:10.1117/12.505854

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22 December 2003 Interferometric testing of soft contact lenses

Gregory A. Williby; Daniel G. Smith; Richard B. Brumfield; John E. Greivenkamp

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Proceedings Volume 5180, Optical Manufacturing and Testing V; (2003) https://doi.org/10.1117/12.505854
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

Abstract

Rapid growth in the contact lens industry towards higher levels of customization has precipitated the need for advances in the metrology techniques and instrumentation used to evaluate soft contact lenses. By measuring the transmitted wavefront, the information needed to evaluate a wide range of lens types (spherical, toric, bifocal) is obtained. A Mach-Zehnder interferometer is used with the lenses tested in saline solution. The lenses must be tested in saline solution to prevent dehydration of the lens, which results in an index change. The lenses are mounted in a cuvette, or water cell, that circulates fresh saline. Calibration of the instrument is complicated by the aspheric wavefronts produced by the lenses and the inherent aberrations picked up by the wavefront as it is imaged from immediately behind the lens to the detector. Simply removing a baseline, no test optic measurement from the measured wavefront does not satisfactorily remove the induced aberrations. Instead, removal of the induced aberrations is achieved by reverse raytracing. In reverse raytracing, the wavefront at the detector is traced back through the system to immediately behind the lens. The use of raytracing code enables theoretical wavefronts to be generated and expected-to-calculated performance evaluations to be made at the transmitted wavefront level.

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Gregory A. Williby, Daniel G. Smith, Richard B. Brumfield, and John E. Greivenkamp "Interferometric testing of soft contact lenses", Proc. SPIE 5180, Optical Manufacturing and Testing V, (22 December 2003); https://doi.org/10.1117/12.505854

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