Date of Award

1-1-2000

Thesis Type

Masters

Document Type

Thesis

Divisions

Faculty of Science

Department

Department of Physics

Institution

Universiti Malaya

Abstract

A digital holography system has been developed in this study. The object is recorded and the hologram is stored electronically with a charged-couple-device (CCD) camera without any focusing optics. The reconstruction of the digitally sampled hologram is done numerically with a computer. The algorithm and software for numerical reconstruction, which consists in a numerical realization of the Fresnel-Kirchhoff diffraction integral, are designed and implemented with two­dimensional and three-dimensional simple objects. The characteristics of the system have been studied. For the CCD camera (768x494 pixels) been used with spatial resolution of about I 00 lines/mm, the angle between reference and object waves is limited to a few degrees. This limits the size of the objects to be recorded to a few centimeters and the distance between object and CCD-target to about a meter. The system is also implemented in holographic interferometry. Two or more Fresnel holograms, which represent different loading states of the objects, are generated directly on a CCD-target and stored electronically. There are two approaches to calculate the interference phase resulting from the two states of the object in the reconstruction process. Firstly, it is determined from the interference pattern. which is generated by the superposition of the calculated intensity of the object waves. Secondly, it is directly calculated from the phases of the waves of both states. This second approach allows direct calculation of interference phase from the holograms without generating an interference pattern. Finally, an accurate. simple and direct measurement system for coefficient of linear thermal expansion of materials based on the principle of digital holographic interferometry is designed. This system is tested for three different common materials. namely aluminium. brass and stainless steel. The results obtained are compares favorably with the standard values. The major drawback of the method is the low spatial resolution of CCD arrays. Consequently only small objects at large distance from the CCD-target can be resolved. However, with the present CCD camera, the quality of the reconstructed image is good especially when used in holographic interferometry and is comparable to that of conventional holographic techniques using photographic films.

Initial

snms

Additional Information

Dissertation (M.A) -- Faculty of Science, Universiti Malaya, 2000.

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