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Proceedings Paper

White-light measurement for high-performance liquid crystal spatial light modulators
Author(s): Matthew Richard Hart; David G. Vass; Mark L. Begbie
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Paper Abstract

Development of high-performance liquid crystal (LC) phase modulators requires accurate control of the thickness and uniformity of the LC cell. Consequently, precise measurement of spatial thickness variations in these cells, which may be tens of microns thick, is a key requirement for evaluating and improving device quality. However, ambiguity problems render single wavelength interferometric methods unsuitable for this task. A practical solution is white-light interferometry (WLI) which has an essentially infinite unambiguous measurement range. For cell measurement, the path difference between the two interfering beams is set by the cell thickness, thus ruling out the commonly used coherence scanning method of WLI. Instead, we use an optical scanning method: analyzing the spectral fringes formed when white light reflects from a cell's bounding surfaces in order to map its thickness with nanometer resolution. We describe a number of experimental configurations and data processing schemes which allow us to maximize vertical and lateral measurement resolution while keeping data acquisition time and storage requirements to a minimum. We also point out that the technique can be used to characterize the switched states of phase modulators and for high-resolution surface profiling. We demonstrate the latter, showing preliminary results from a noncontact profiler based on this principle.

Paper Details

Date Published: 11 April 1997
PDF: 11 pages
Proc. SPIE 3015, Liquid Crystal Materials, Devices, and Applications V, (11 April 1997); doi: 10.1117/12.271399
Show Author Affiliations
Matthew Richard Hart, Univ. of Edinburgh (United Kingdom)
David G. Vass, Univ. of Edinburgh (United Kingdom)
Mark L. Begbie, Univ. of Edinburgh (United Kingdom)

Published in SPIE Proceedings Vol. 3015:
Liquid Crystal Materials, Devices, and Applications V
Ranganathan Shashidhar, Editor(s)

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