The zone plate interferometer

Thesis (M.S.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1971.This thesis develops the basic idea of a Fresnel zone plate two-beam interferometer, leading to a description of what is undoubtedly a very useful and practical instrument. In the introductory chapter, the elements of two-beam interference and partial coherence are presented. To add some perspective to later discussion, the main features of some well known two-beam interferometers are briefly reviewed and compared. Representative examples of the 'commonpath' class of designs - the scatter plate interferometer and a birefringent design - are also described. Murty's proposal for a Fresnel zone plate, common-path, interferometer is then discussed. The zone plate interferometer in its developed form is described in detail, and three basic configurations, or modes, of the interferometer are distinguished, associated with the real and virtual first order foci of the zone plate. These modes are treated systematically and analyzed, and their respective advantages and disadvantages given. Multiple diffraction orders give rise to multiple configurations - and multiple interference patterns. These possibilities are also discussed. The classical Fresnel zone plate and its modified forms are reviewed and their properties given. An interferometric method to prepare phase type zone plates, including a means to generate uniform amplitude wavefronts, is described. Moiré fringes allow the accuracy of the zone plates to be measured in a simple manner. A zone plate interferometer has been constructed and its description is given in detail. This includes component specifications, the method of alignment, and the location of fringes. The results obtained using a zone plate in different modes, and the phenomenon of compound interference patterns are discussed and interpreted particularly from the viewpoint of holography. A comparison has been made between the performance of this interferometer and a compact Twyman-Green interferometer. Interferograns which illustrate this test are included, revealing the high quality of the interference pattern (close to unit visibility) with the zone plate instrument. Possible errors intrinsic to the interferometer system are also examined. It is shown that self-compensation reduces most of these to a negligible value. The zone plate interferometer is simple to construct and to operate, and is a useful addition to the range of commonpath designs; perhaps, in many respects, the most useful