Date of Award
Doctor of Engineering Science in Electrical Engineering
Andrew Ulrich Meyer
Joseph J. Padalino
The theory of two-beam holography is generalized to include quasi-monochromatic radiation of any degree of spatial coherence. It is shown that a clear, undistorted reconstruction can be obtained provided the reference beam is highly coherent. The effect of the partial coherence of the illumination is only to make the reconstructed image darker. Specifically, the amplitude of the radiation at any point of the image is proportional to the amplitude of the radiation leaving the corresponding point on the object during the exposure, times the magnitude of the coherence between the latter radiation and the reference beam. Holograms made using either a plane or a spherical reference beam are discussed in detail.
A technique is developed for measuring the magnitude of the degree of coherence of the radiation at every point on the object surface, with respect to the reference beam, by measuring the irradiance at the real image reconstruction of the object. As an example, the coherence of radiation reaching a plane object from a small, circular, spatially incoherent source is measured. The data are in good agreement with the calculations made using the van Cittert-Zernike Theorem.
Motion of the object during the hologram exposure is shown to affect a quantity analogous to coherence. Such a quantity is introduced and it is shown that it affects the reconstruction in a way that is almost identical to that of partial coherence. The technique for measuring coherence is then extended to the measurement of displacements of the object. In particular, the relationship between the object displacement and the appearance of the reconstructed image is analyzed in detail for objects moving with constant or sinusoidal velocity. Several examples are given of measurements of the total displacement of objects moving with constant velocity throughout the exposure time. Displacements of one-third wavelength are easily detected.
Lurie, Michael Jay, "Effects of partial coherence on holography" (1967). Dissertations. 1331.