The exposure amounts of R, G, and B laser light emitted from a fabrication light source are so adjusted that the diffraction efficiency at R, G, and B wavelengths in an optical element is commensurate with the light intensity at the R, G, and B wavelengths in the light emitted from a reproduction light source. For example, when the light intensity of the light emitted from the reproduction light source is increasingly low at the B, G, and R wavelengths in this order, the exposure amounts of the R, G, B, laser light emitted from the fabrication light source are so adjusted that the diffraction efficiency in the optical element is increasingly high at the B, G, and R wavelengths in this order. In this way, the hue of the light (reproduction light) obtained from the reproduction light source via the optical element can be adjusted to the hue desired with every reproduction light source used, while the most use is made of the light emitted from the reproduction light source actually used.