Optical transfer function of a diffraction-limited system for polychromatic illumination

A closed-form expression is derived for the optical transfer function of a diffraction-limited system under polychromatic illumination. The expression is useful in a method for the accurate and efficient computation of the optical transfer function of an optical system. The expression is also useful in the theoretical analyses of the optical system. This method is illustrated with an example where the optical transfer function of the human eye is computed.