  We report a calculation reduction method for color computer-generated
holograms (CGHs) using color space conversion. Color CGHs are generally
calculated on RGB space. In this paper, we calculate color CGHs in other color
spaces: for example, YCbCr color space. In YCbCr color space, a RGB image is
converted to the luminance component (Y), blue-difference chroma (Cb) and
red-difference chroma (Cr) components. In terms of the human eye, although the
negligible difference of the luminance component is well-recognized, the
difference of the other components is not. In this method, the luminance
component is normal sampled and the chroma components are down-sampled. The
down-sampling allows us to accelerate the calculation of the color CGHs. We
compute diffraction calculations from the components, and then we convert the
diffracted results in YCbCr color space to RGB color space.
