Abstract

Rules for assigning cones to the two-wavelength sensitivity classes long (L) and medium (M) have been added to the close-packing model for foveolar cone positions. The packing model places each cone tightly against two other cones already in place, so it is natural to consider schemes which assign each cone on the basis of the assignments of the two cones with which it is being placed in contact. The simplest deterministic assignment with reasonable properties is to assign the new cone to the opposite class if the two are the same and to make the assignment L if they are different. This rule generates a proportion of ~62% L and 38% M, not exactly the 2 to 1 rule that has been proposed, but fairly close. The rule has the important feature that it does not depend on the assumption of exact hexagonal (triangular) packing for its implementation. The aliasing properties of retinas generated by this rule and by random assignment with corresponding proportions are demonstrated for chromatic gratings and for luminance gratings in the case that one class is desensitized.

© 1986 Optical Society of America