I. Amidror, R.D. Hersch

Journal of Modern Optics, Vol. 44, No. 5, 1997, 883-899

In the present article we give a full quantitative analysis of the
multichromatic moiré effects in the superposition of coloured periodic
layers, which is based both on the Fourier theory and on the theory of
colorimetry and colour vision. This is done by introducing both into the image
domain and into the Fourier frequency domain a new dimension l, representing
the visible light wavelengths. In the image domain we represent each layer by
the chromatic reflectance (or transmittance) function r(x,y;l), which is a
generalization of the reflectance (or transmittance) function r(x,y) in the
monochromatic case. Consequently, in the Fourier spectral domain each impulse
amplitude becomes a function of l. All the results previously obtained by our
Fourier-based approach in the monochromatic case remain valid in the
multichromatic case, too, for every wavelength l separately. This enables us to
find, for every point (x,y) of any given moiré, the full colour spectrum
{r(x,y;l) | 380<=l<=750} which expresses the visible colour at the point (x,y)
of the moiré in question. We illustrate the discussion by several
multichromatic superpositions, some of which showing very spectacular,
colourful moiré effects.