Abstract: Three-zone phase-only transverse superresolution filters are designed by nonlinear optimisation at the special Strehl ratio S, which is the ratio of the maximum intensity of the central core of the superresolving pattern to the Airy pattern. The design model and several examples are presnted and compared with the superresolution filters of references with better resolving effects. To suppress the strong sidelobe intensity, these phase-only filters are used in the confocal scanning microscopy system and the sidelobe can be restrained greatly.

Key words: phase-only filters, superresolution, confocal scanning microscopy, nonlinear programming