Abstract

Foveal aliasing causes high-frequency interference fringes to look like bright and dark (achromatic) zebra stripes. Some observers also report chromatic zebra stripes composed of desaturated red and green stripes. Two observers adjusted fringe spatial frequency and orientation to find the coarsest chromatic and achromatic zebra stripes. The coarsest chromatic zebra stripes occurred near the cone Nyquist frequency (57-64 cycles/ deg), half of the frequency producing the coarsest achromatic zebra stripes. The same fringe orientations, separated by ~60 deg, produced the coarsest chromatic and achromatic zebra stripes. Chromatic zebra stripes may be produced by a contrast-dependent color effect.¹ At any instant, Nyquist frequency fringes produce local regions of high contrast (when cones are centered on fringe peaks and troughs) alternating with regions of low contrast (when cones lie between peaks and troughs). This could form red and green zebra stripes with hue determined by local contrast. An alternative hypothesis is aliasing by the M and L cone submosaics. If this hypothesis were correct, the data would constrain the packing arrangement of M and L cones. At least a subset of M cones would have to be packed in a triangular arrangement with the same orientation as the whole mosaic and with twice the spacing between rows of cones.

© 1988 Optical Society of America