Influence of partially coherent illumination on the performance of non-airy pupil functions in microscopic systems.

The influence of partially coherent illumination on the performance of a few non-Airy pupil functions (Sonine, phase-step, annular, Straubel, and Lansraux-Boivin pupil functions) is studied in the context of microscopic imagery. The imaging properties of these pupil functions are investigated in terms of the two-point image contrast and resolution. It is seen that by adjusting the state of coherence of illumination of the object structure and a suitable choice of the pupil function, a resolution higher than that due to the Airy pupil function may be obtained. It is also possible, in a similar way, to increase the image contrast without unduly reducing the image resolution.