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Proceedings Paper

Ray-trace simulation of the random ball test to improve microlens metrology
Author(s): Neil W. Gardner; Angela D. Davies
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Paper Abstract

Interferometer wavefront bias is a complicated function of the optics imperfections in the instrument. An interferometric measurement of the figure error on a micro-refractive lens requires careful calibration to separate instrument bias from errors on the part. A self-calibration method such as the random ball test is effective in accomplishing this task without the need for a high-quality calibration artifact. The test, an averaging technique applied to a series of sphere surface patches, allows for calibration of the interferometric wavefront bias. Recent studies of the random ball test have shown that the calibration is affected by ray-trace errors that depend on the curvature of the ball used for the test and becomes significant in the micro-optic range (radius less than 1 millimeter). A comprehensive ray-trace simulation of the random ball test with modifiable variables was created using MATLAB® and ZEMAX® to allow for further investigation into the relationship between test lens misalignment, curvature, numerical aperture, ball figure error, and interferometer bias. The basis for the model hinges on defining a sphere in terms of a set of spherical harmonic functions, and varying the amplitudes and the number of functions to adjust the figure error on the sphere. The flexible simulation can be fine-tuned and used to model a variety of interferometers with different specifications. Our ultimate goal is to confirm the validity of the RBT, determine an efficient method of implementation, and understand the aspects impacting calibration uncertainty.

Paper Details

Date Published: 14 August 2006
PDF: 8 pages
Proc. SPIE 6292, Interferometry XIII: Techniques and Analysis, 629204 (14 August 2006); doi: 10.1117/12.681421
Show Author Affiliations
Neil W. Gardner, Univ. of North Carolina at Charlotte (United States)
Angela D. Davies, Univ. of North Carolina at Charlotte (United States)

Published in SPIE Proceedings Vol. 6292:
Interferometry XIII: Techniques and Analysis
Katherine Creath; Joanna Schmit, Editor(s)

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