Exploring the Stiles-Crawford effect of the first kind with coherent light and dual Maxwellian sources

The visual impact of light obliquely incident on the retina is diminished due to the Stiles-Crawford effect of the first kind. It is normally analyzed by scanning a small Maxwellian source across the eye pupil while making subjective visibility comparisons to a static reference field that enters the eye near the pupil center. Here, we propose an alternative characterization method with two coherent Maxwellian point sources located at opposing sides of the pupil. This produces interference fringes at the retina with an underlying phase gradient. Altering the power ratio of the two point sources makes tuning of the wavefront inclination at the retina feasible. Thus, the Stiles-Crawford effect of the first kind can be examined without scanning the incident light across the pupil. In this paper, a spatial light modulator with holographic phase maps has been used to generate two Maxwellian point sources at the pupil that project a given phase variation onto the retina. We found that the effective obliqueness of light at the retina is determined by the weighted center-of-mass of the field amplitude at the pupil. Alternative techniques to generate the two secondary point sources may improve the accuracy of the method.