Imaging with Fresnel zone pupil masks: extended depth of field.

Fresnel zone plates are used as pupil apertures to extend the depth of field of an incoherent imaging system. The defocused optical transfer function is evaluated approximately, and the results are confirmed by experiments and by subjective evaluations of the images of a test chart. With a pupil having four zones, for example, the resolution limit at four depths of field out of focus is improved by a factor of 10.