Phase-only filter solution based on fuzzy logic for reducing the defocus problem

Eran Gur*, Zeev Zalevsky, Dina Elkind, David Mendlovic

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review


One of the main problems in imaging systems is the difficulty in placing the output CCD exactly at the imaging plane. This causes the so-called defocus effect in which the optical transfer function in the output plane is worse than expected. This leads to loss of detail and possible contrast conversion. A good solution for solving the defocus problem in a specific plane would be to place a phase-only filter right after (or before) the lens of the imaging setup. This filter can be designed to cancel the defocusing effect in the specific plane. The design of a filter that will yield good images for a range of planes at different distances from the actual imaging plane requires a more complex approach. In this work the authors introduce a novel method for designing the filter using Fuzzy Logic principles. The Fuzzy Logic inference engine accepts as input data a set of filters; each designed for good results in a specific region, and collaborates them to produce a single phase-only filter. The optical transfer function of the combined filter in the various regions is presented to demonstrate the improvement in limiting defocus.

Original languageEnglish
Pages (from-to)250-258
Number of pages9
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 2002
EventApplications and Science of Neural Networks, Fuzzy Systems, and Evolutionary Computation V - Seattle, WA, United States
Duration: 9 Jul 200210 Jul 2002


  • Defocus
  • Fuzzy logic
  • Optical imaging
  • Phase only filters


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