The effect of the relief image in a coherent optical system was minimized by matching the average refractive index of the emulsion ne with that of a liquid of a known refractive index nl. A match of ne and nl was determined by minimizing the intensity of the first side order of the Fraunhofer diffraction pattern of a sine-wave image. A match of ne and nl can be made exactly only when the surface gelatin associated with the silver and the differential tanning effects of development are not present. Under other conditions ne is not homogeneous. The intensity of the Fraunhofer pattern was however reduced from 70% of the d.c. in air to only 0.25% of the d.c. in a liquid of nl, which approximates ne best.
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School of Photographic Arts and Sciences (CIAS)
Sklar, Edward, "Minimizing the effects of the relief image in a coherent system through index matching" (1967). Thesis. Rochester Institute of Technology. Accessed from
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