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Optical Engineering

Metrology of thin transparent optics using Shack-Hartmann wavefront sensing
Author(s): Craig R. Forest; Claude R. Canizares; Daniel R. Neal; Michael McGuirk; Mark Lee Schattenburg
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Paper Abstract

The surface topography of thin, transparent materials is of interest in many areas. Some examples include glass substrates for computer hard disks, photomasks in the semiconductor industry, flat panel displays, and x-ray telescope optics. Some of these applications require individual foils to be manufactured with figure errors that are a small fraction of a micron over 10- to 200-mm lengths. Accurate surface metrology is essential to confirm the efficacy of manufacturing and substrate flattening processes. Assembly of these floppy optics is also facilitated by such a metrology tool. We report on the design and performance of a novel deep-ultraviolet (deep-UV) Shack-Hartmann surface metrology tool developed for this purpose. The use of deep-UV wavelengths is particularly advantageous for studying transparent substrates such as glass, which are virtually opaque to wavelengths below 260 nm. The system has a 143×143-mm2 field of view at the object plane. Performance specifications include 350-µrad angular dynamic range and 0.5-µrad angular sensitivity. Surface maps over a 100 mm diam are accurate to <17-nm rms and repeatable to 5 nm rms.

Paper Details

Date Published: 1 March 2004
PDF: 12 pages
Opt. Eng. 43(3) doi: 10.1117/1.1645256
Published in: Optical Engineering Volume 43, Issue 3
Show Author Affiliations
Craig R. Forest, Massachusetts Institute of Technology (United States)
Claude R. Canizares, Massachusetts Institute of Technology (United States)
Daniel R. Neal, WaveFront Sciences, Inc. (United States)
Michael McGuirk, Massachusetts Institute of Technology (United States)
Mark Lee Schattenburg, Massachusetts Institute of Technology (United States)


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