Instrumentation, Techniques, and Measurement

Low-coherence interferometer for contact lens surface metrology

[+] Author Affiliations
Kyle C. Heideman

Raytheon Space and Airborne Systems, 2000 East El Segundo Boulevard, El Segundo, California 90245, United States

John E. Greivenkamp

University of Arizona, College of Optical Sciences, 1630 East University Boulevard, Tucson, Arizona 85721, United States

Opt. Eng. 55(3), 034106 (Mar 29, 2016). doi:10.1117/1.OE.55.3.034106
History: Received November 14, 2015; Accepted January 28, 2016
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Abstract.  Contact lens performance depends on a number of lens properties. Many metrology systems have been developed to measure different aspects of a contact lens, but none test the surface figure in reflection to subwavelength accuracy. Interferometric surface metrology of immersed contact lenses is complicated by the close proximity of the surfaces, low surface reflectivity, and instability of the lens. An interferometer to address these issues was developed and is described here. The accuracy of the system is verified by comparison of glass reference sample measurements against a calibrated commercial interferometer. The described interferometer can accurately reconstruct large surface departures from spherical with reverse raytracing. The system is shown to have residual errors better than 0.05% of the measured surface departure for high slope regions. Measurements made near null are accurate to λ/20. Spherical, toric, and bifocal soft contact lenses have been measured by this system and show characteristics of contact lenses not seen in transmission testing. The measurements were used to simulate a transmission map that matches an actual transmission test of the contact lens to λ/18.

© 2016 Society of Photo-Optical Instrumentation Engineers

Citation

Kyle C. Heideman and John E. Greivenkamp
"Low-coherence interferometer for contact lens surface metrology", Opt. Eng. 55(3), 034106 (Mar 29, 2016). ; http://dx.doi.org/10.1117/1.OE.55.3.034106


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