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Title: Optical characterization and enhancement of liquid-crystal spatial light modulators
Author: Hart, Matthew
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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Liquid crystal spatial light modulators (LC SLMs) are used in a variety of applications including information display, optical computing and information processing, holographic data storage and adaptive optics. Only in displays, however, have they achieved widespread use outside the research laboratory. Part of the reason for this is the comparatively low optical quality of most LC modulators currently available. This thesis explores methods which can be used to characterize and enhance these devices: particularly those intended for use in non-display applications where output wavefront quality, and spatial device uniformity, can be critical. One key device parameter to be determined is the value and uniformity of the cell gap which defines the thickness of the LC layer. Surface profile measurement is also important for assessing, for example, the optical quality of reflective VLSI pixel arrays. In addition, characterization of LC response for a given input drive signal is often needed to allow prediction of SLM performance in a particular optical system. The development of methods for accurate determination of LC cell gaps is described. Broadband and multiple-wavelength interferometry are used to provide the large unambiguous measurement range necessary for absolute measurement of these micron-scale distances. One method is based on the technique of phase-shifting interferometry and allows the spatial variations to be mapped relatively quickly from a small number of interferograms acquired at different wavelengths. Techniques for reducing systematic measurement errors are discussed and demonstrated both through numerical simulation and experiment. A novel white-light interferometer configuration is also described, based on spectral analysis of white light interferograms using an imaging stationary Fourier transform spectrometer. It is shown that this configuration permits real-time visualization of spatial variations in interferometer path difference, as well as giving unambiguous depth measurements with nanometre resolution. Applications to surface profiling and to cell gap determination are discussed and experimental surface measurement results given.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available