Dominant color reversals and chromaticity cusps in interferometric color mixing

Abstract

White light was injected into a Michelson interferometer to obtain color fringes, which show a succession of dominant colors that we have analyzed quantitatively. For a given interferometric path length difference, ΔL, the resulting color fringe was sent to a diffraction grating spectrometer and light-sensitive detector, to record its spectral composition. This data enabled us to depict the color in the two-dimensional color space of the x–y C.I.E. chromaticity diagram. In this analysis, we show the dominant color in the progression of color fringes in interferometric color mixing to reverse the direction with which it sweeps through the visible spectrum, as ΔL is monotonically increased. This phenomenon is represented by spiraling with cusps and reversals of curvature in the C.I.E. x–y plane. Our measurements agree favorably with a theoretical model showing cusp behavior. We show the cusps to signify a transition from in- to out-of-phase behavior in the relative growth of x and y. This result is robust, persisting for many trial spectral power distributions (SPDs) of the incident ‘‘white light’’ illuminant.