Abstract

We measured chromatic contrast sensitivity using red–green interference fringes. This allowed the production of chromatic gratings with high intensity, spatial frequency, and contrast, without blur ring by optical factors such as axial chromatic aberration and diffraction. One persistent problem in producing isoluminant gratings is the possibility of a luminance artifact due to a phase shift between the red and green components, which can be caused by transverse chromatic aberration or, in the Maxwellian view, movements of the head and eyes relative to the optical system. We intro duce a new psychophysical technique that avoids this problem. Isoluminant 632.8-nm and 514.5-nm fringes of equal spatial frequency and orientation were drifted slowly in opposite directions (0.25 Hz). This stimulus changes in time from a luminance to a chromatic grating in each temporal cycle, so that a purely chromatic stimulus will always occur at some point despite eye and head movements. The observer adjusted the contrast of the pattern until the chromatic component was just detectable. We find that foveal chromatic gratings can be seen at spatial frequencies up to 20-25 c/deg.

© 1991 Optical Society of America