Devices and methods that reduce or eliminate chromatic or comatic variations in the location of the excitation or emission in an optical system such as a confocal microscope, by enhancing parfocality are provided. Such devices include an optical collimator comprising a parabolic reflector and a convex aspheric reflector, wherein the aspheric reflector and the parabolic reflector are positioned such that light is incident at an off-axis angle relative to the axis of symmetry of the reflectors to extend the useable field of view.