Interaction between longitudinal and lateral chromatic aberrations

Abstract

Human eyes exhibit both longitudinal and lateral chromatic aberration. Achromatizing lenses have been designed to correct longitudinal chromatic aberration. However, these lenses are not designed to correct for the lateral chromatic aberration of the eye. Based on optical models of human eyes and two different achromatizing lenses,1,2 we have evaluated the relative effects on retinal image quality of longitudinal and lateral chromatic aberrations separately and in combination. The eye’s 2 diopters of longitudinal chromatic aberration may seem large, but with a 5-mm pupil its effect in the retinal image quality for a white p4 phosphor is comparable with that for a monochromatic source with only 0.1-0.2 diopters of blur. Although correction of longitudinal chromatic aberration improves paraxial image quality, it can degrade off-axis image quality. This is because longitudinal chromatic aberration can protect the eye from the contrast degradation effect of lateral chromatic aberration. Also, special care is required when using achromatizing lenses to prevent the introduction of more lateral chromatic aberration in the retinal image than is normally present in the unaided eye.