Abstract

Deliberate variations of emulsion thickness between holographic exposures and reconstruction produce a range of output wavelengths from a fixed exposure wavelength, a technique known as pseudocolor multicolor reflection holography. The usual methods require the removal of the film or plate from the holographic setup between exposures for imbibition of a swelling agent, followed by drying and replacement, so that retention of the swelling agent forces a physical increase in the thickness of the emulsion. However, the density (and hence the thickness) of the gelatin binder can also be varied by changing its electrolytic environment. By immersing the holographic emulsion in a suitable solution, allowing it to come to a new equilibrium thickness, and exposing it with a long-wavelength laser, shorter wavelength reconstructions can be obtained without removing the film or plate from the setup. Careful changes of solution can make a precise sequence of swellings possible, producing multiple reconstruction colors from a set of constant-wavelength recordings. Here we describe pretreatments of the emulsion that make rapid and stable equilibria possible and swelling bath sequences that produce color primaries suitable for full-color computer-graphic holographic imagery.

© 1988 Optical Society of America