Recent advances in color reflection holography

The fidelity of color reproduction achievable in reflection holograms is analyzed by an in- depth theoretical and experimental treatment. A theoretical model is described which incorporates color rendering analysis, effects of bandwidth, signal to noise for color holograms, and wavelength shifting; this analysis considers the effect on color by the holographic process which has been previously neglected. The model compares octagons formed by points on a CIE diagram corresponding to eight Munsell colored chips when reproduced by the holographic image and when lit by a standard light source. The theory is shown to compare well with experimental results obtained using both sandwiched Ilford films and a single panchromatic film. The model is then employed to predict holographic image color reproduction for all possible recording wavelengths. From this analysis optimum wavelength combinations are obtained. It is predicted that the color reproduction obtained by a practical set of recording wavelengths (458, 532, and 633 nm, for example) can actually be more accurate in a holographic image than under laser light, albeit with a reduced gamut area. A brief discussion explains why a short blue component with low diffraction efficiency achieves superior color reproduction.