Precision form measurement of biconic surfaces using scanning Fizeau interferometry

Thomas Dresel

doi:10.1117/12.2673831

15 August 2023 Precision form measurement of biconic surfaces using scanning Fizeau interferometry

Thomas Dresel

Proceedings Volume 12618, Optical Measurement Systems for Industrial Inspection XIII; 1261817 (2023) https://doi.org/10.1117/12.2673831
Event: SPIE Optical Metrology, 2023, Munich, Germany

Abstract

Biconic surfaces are among the most fundamental freeform surfaces and have important applications in the ophthalmic industry. They are characterized by just four parameters, namely the two radii and two conical constants in the x- and y-direction, and they have even symmetry along x and y. As for many other optical surface types, the manufacturing of these surfaces requires form measurements with a precision of a tenth of a wave. We introduce an approach to measure the form of biconic surfaces using Fizeau interferometry. The approach builds on concepts we have used in the past for the measurement of aspheres and toric surfaces. A combination of sub-aperture data acquisition, fringe order tracking and distance function removal produces a series of sub-aperture deviation maps which can then be combined into a full field deviation map of the entire surface. This final map can be further analyzed for errors in the four design parameters as well as higher-order form errors. In addition, it is possible to determine the orientation of the principal curvatures of the test part with respect to its mount in the instrument. We discuss the details of the measurement procedure, show first measurement examples, and discuss how the method can be validated using toric and aspheric surfaces which can be measured as such but can also be measured as biconics allowing for comparisons.

Conference Presentation

Citation Download Citation

Thomas Dresel "Precision form measurement of biconic surfaces using scanning Fizeau interferometry", Proc. SPIE 12618, Optical Measurement Systems for Industrial Inspection XIII, 1261817 (15 August 2023); https://doi.org/10.1117/12.2673831

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