Abstract

Over a narrow range of spatial frequencies higher than the parafoveal resolution limit, interference fringes can appear as striated patterns whose predominant orientation is perpendicular to the actual fringe orientation. This finding has been confirmed with a forced-choice orientation identification procedure. Aliasing by the parafoveal cone mosaic may explain this orientation reversal at high spatial frequencies. In these conditions, the power spectra of fringes sampled by the irregular cone mosaic contain low frequencies whose overall orientation is perpendicular to the fringe orientation. This happens only when the fringe period equals the average spacing of cones. In our measurements at various retinal eccentricities, the fringe period that produces the orientation reversal agrees with the anatomical measures of cone spacing of Osterberg¹ which suggests that the alias arises in cones.

© 1986 Optical Society of America