Holography Techniques In The Color Reproduction Of Two-Dimensional Images

Abstract

The two main problems in color holography have been the presence of cross talk images and the field of view reduction in the vertical direction of the holographic images. Techniques have been proposed in order to reduce these effects like recording of three holograms on the same holographic plate using diferents wavelengths, other make methods use of color masks and/or spatial filtering [1]. Other authors [2] reported a pseudocolor technique in which only one wavelength, has been used to record the hologram, the reference beams impinge the holographic plate at different angles, however in these methods the problem of a narrow field of view is still present. Tamura [3], using the two step rainbow hologram technique, recorded three holograms in the conventional way, using a rectangular slit. He uses this holograms as objects for a fourth holographic plate on which they are recorded using reference beams at three different angles. Tamura's technique requires only one wavelength and four holographic plates which give a good color image but it requires too much care and more than one holographic plate. In this paper we describe a holographic pseudocolor technique which is based on the recording of three image holograms on the same holographic plate, using a single wavelength He-Ne laser, and three reference beams at different angles. Fixing one of the angles of the reference beams the other two can be calculated in such a way that upon reconstruction with white light, each hologram is reconstructed in a primary color. Using a ground glass during the recording step, diffused laser light illuminates the object increasing this way the vertical vision angle. On the other side, the cross talk image problem is solved by coding the reference beams using diffusing screens. A hologram is obtained which gives a pseudocolor image, with colors very close to the real object's, but with loss in resolution.