Extending the depth-of-focus using fuzzy logic and an intensity mask

A limited depth of focus is one of the main problems in optical sensing devices. Throughout the years many static and dynamic solutions have been suggested to extend the focal depth of an optical imaging system. In this work the author suggests a novel approach for generating a single intensity filter to extend the depth of focus of an existing imaging setup. The main concept is that different out of focus planes require different attention, thus it is important to assign different weights to different out-of-focus planes and design a filter for each plane, then generate a weighted combining of the filters. A fuzzy logic inference engine determines the weights of the different planes, as planes further away from the focal plane generally receive bigger weights. The fuzzy logic inference engine grades the different weighing sets according to the average width of the optical transfer functions and according to the deviation between function's widths. First, separate phase only filters are generated to ensure high efficiency of the imaging setup. Later, these masks are converted to a single intensity mask which is much easier to construct and, as will be shown, yields far better depth of focus than the original setup.