Browsing by Subject "Diffusers"
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Item Computer Generated Multiplex Holography(Texas Tech University, 1980-05) Irby, Carl ArthurNot Available.Item Correlation properties of diffusers for multiplex holography(Texas Tech University, 1979-08) Kral, Edward LeeA promising method of representing two-dimensional space-variant optical systems is through multiplex holography. The multiplexing operation requires the use of diffusers in the reference beam path to provide a unique code for each object wave. In this thesis, various types of diffusers are analyzed and compared within the framework of multiplex holography. A simple model is initially developed which can accommodate a wide range of diffuser families, including pure phase, pure amplitude, and combined amplitude and phase diffusers. Crosscorrelation and autocorrelation calculations are then presented for both spherical wave (chirp) illumination and plane wave illumination, and a signal-to-noise analysis based on these calculations is included. Finally, the implications of the analysis are thoroughly discussed, and recommendations for further research are given.Item Fabrication of binary phase diffusers for space-variant processing(Texas Tech University, 1983-12) Chase, Scott BTechniques have previously been described for holographically representing space-variant systems. By spatially sampling the input plane and using phase mask diffusers to encode the multiple reference beams, one can sequentially record holograms exhibiting a minimal amount of crosstalk. Gold-coded binary phase masks have been shown to have good correlation properties with known cross-correlation bounds. This thesis describes a technique which generates phase masks using a laser scanner computer generated hologram (CGH) writing f a c i l i t y at a wavelength of 4579A. Methods for determining the proper resist thickness to achieve the necessary 180 degree phase shift between adjacent cells in a mask include analyzing the data taken by an interference microscope and quantitative analysis of the dc component present in the Fourier spectrum of the mask. Comparisons of the effectiveness of the phase masks with that of ground-glass were obtained using two different tests. First, the phase masks were used in a space-variant processor, and the results of the multiplexed holograms were compared to those obtained earlier using a ground-glass diff user. Secondly, computer-generated holograms were made using the phase masks as diffusers and the results were compared with those previously obtained using amplitude masks.Item Multiplex holography for space-variant optical processing(Texas Tech University, 1979-08) Jones, Mike IvorThis thesis describes extensive experimental implementations of multiplex holography for use in representing two-dimensional spacevariant optical systems. Diffusers are used to encode the reference beams for effective crosstalk suppression. The problem of hologramto-hologram crosstalk is both analytically and experimentally examined, and various methods for its suppression are discussed. The merits of using ground glass diffusers for crosstalk suppression are experimentally investigated, and the superiority of chirped-wave diffuser illumination over plane-wave illumination in crosstalk suppression is demonstrated. The first implementations of binary-coded diffuser masks for crosstalk suppression in multiplex holography are shown. The experimental proof of coherent addition in overlapping holographic outputs is presented, and the first holographic representation of an extremely space-variant optical system is shown. The holographic representation of an optical system using a large (10 x 10) array of input sampling points is also shown. With a working 2-D space-variant holographic processor thus available, a variety of space-variant processing operations for future investigations are suggested.Item Space-variant processing using phase codes and Fourier-plane sampling techniques(Texas Tech University, 1980-05) Kasturi, RangacharAny slowly varying linear space-variant system can, in principle, be represented holographically by spatially sampling the input plane and multiplexing the respective system transfer functions. A scheme reported earlier for implementing this technique makes use of phase diffusers in the reference beam paths to encode sequentially recorded holograms. However to minimize the cross talk between the holograms upon playback the diffusers should have good correlation properties, In this thesis extensive computer simulations to evaluate the correlation properties of a family of binary phase codes are conducted. An alternative multiplexing technique in which the transfer functions are sampled in the Fourier plane to generate a composite hologram is also described. In this technique the samples of the transfer functions are placed in non-overlapping regions and hence there will be no crosstalk upon playback. However multiple copies of the input function are required during the playback step. The results of preliminary experiments conducted to evaluate this approach for space-variant system representation are presented including the verification of coherent addition using computer multiplexed holograms.