<title>Wavelength selection for color holography</title>

Abstract

Color holography is typically achieved through the use of three wavelengths during the imaging. However, three-color holography is sufficient only when one has the freedom to select locally the proportions of the primaries during reconstruction. This freedom exists in some, but not all, holographic techniques; we discuss wavelength selection in light of this distinction. For holograms that do not allow for local control of color, such as display holography, the color contributions depend on the surface reflectances in the scene; the monochromatic sources point sample these reflectances. From this sampling, we show that the problem of wavelength selection is equivalent to that of finding efficient approximations to the tristimulus integrals. We conclude that three sources are often insufficient for accurate color reproduction, and we suggest wavelengths for holography with three, four, or more wavelengths. For holograms that do allow for local color control, the color science involved is similar to that of raster displays. Therefore, only three primaries are necessary. However, we describe situations where only two primaries are sufficient. This conclusion follows from the dichromatic theory of color reflection, which postulates that often the reflection of light from a surface contains only two color components.