DOMINANT COLOR REVERSALS AND CHROMATICITY CUSPS IN INTERFEROMETRIC COLOR MIXING

White light was injected into a Michelson interferometer to obtain col or fringes, which show a succession of dominant colors that we have an alyzed quantitatively. For a given interferometric path length differe nce, Delta L, the resulting color fringe was sent to a diffraction gra ting spectrometer and light-sensitive detector, to record its spectral composition. This data enabled us to depict the color in the two-dime nsional color space of the x-y C.I.E. chromaticity diagram. In this an alysis, we show the dominant color in the progression of color fringes in interferometric color mixing to reverse the direction with which i t sweeps through the visible spectrum, as Delta L is monotonically inc reased. This phenomenon is represented by spiraling with cusps and rev ersals of curvature in the C.I.E. x-y plane. Our measurements agree fa vorably with a theoretical model showing cusp behavior. We show the cu sps to signify a transition from in- to out-of-phase behavior in the r elative growth of x and y. This result is robust, persisting for many trial spectral power distributions (SPDs) of the incident ''white ligh t'' illuminant. (C) 1995 American Association of Physics Teachers.