PHASE PUPIL FUNCTIONS FOR FOCAL-DEPTH ENHANCEMENT DERIVED FROM A WIGNER DISTRIBUTION FUNCTION

A method for obtaining phase-retardation functions, which give rise to an increase of the image focal depth, is proposed. To this end, the W igner distribution function corresponding to a specific aperture that has an associated small depth of focus in image space is conveniently sheared in the phase-space domain to generate a new Wigner distributio n function. From this new function a more uniform on-axis image irradi ance can be accomplished. This approach is illustrated by comparison o f the imaging performance of both the derived phase function and a pre viously reported logarithmic phase distribution. (C) 1998 Optical Soci ety of America.