Effect of the photographic gamma on hologram reconstructions

Abstract

Thesis (Ph.D.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1969. Author's M.S. thesis, Effect of the photographic process on the intensity of hologram reconstructions, is also scanned to the same file: Thesis (M.S.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1966.An expression derived for hologram exposures made along the straight line portion of the H&D curve of a photographic plate gives the first order transmission of a hologram made up of several object points exposed simultaneously and several object points exposed sequentially. This expression is simplified for the case of only object points exposed sequentially (synthetic holograms) and for the case of only object points exposed simultaneously (conventional holograms). Theory and experiments show the effect of the nonlinearity of the photographic process on the contrast of the reconstruction of both synthetic and conventional holograms. An experimental and theoretical study is given to determine how the total amount of light in the reconstructed image depends upon the number of object points if the total amount of light in the object is kept constant. It is shown both theoretically and experimentally that a conventional hologram contains more light in the reconstructed image than a synthetic hologram of the same number of object points. Also, an experimental and theoretical study is given for both synthetic and conventional holograms to determine the ratio of reference beam illuminance to object beam illuminance which maximizes the amount of light in the reconstructed image. It is shown experimentally that for reasonably small hologram exposures, pre-exposing Kodak 649-F plates to an AG-1 flashbulb increases the amount of light in the reconstructed image. It is also shown that for reasonable pre-exposed densities and observed values of gamma, the maximum amount of light is obtained in the reconstruction of a pre-exposed hologram when the hologram has an average density a little less than one. For holograms that are not pre-exposed, the maximum amount of light is obtained in the reconstruction when the average hologram density is about 0.5. Theory and experiment show that for a hologram object of two or more object points, the non-linearity of the holographic process causes reconstructed images in addition to the desired reconstructed image. These undesired reconstructed images are also in addition to the higher order images caused by the non-linearity of the photographic process. A study is made to determine under what conditions these undesired images are bright enough to degrade the desired reconstructed image