Amplitude modulated phase-only filter
Abdul Ahad S. Awwal, Mohammad A. Karim, Syeda R. Jahan · Annual Meeting Optical Society of America · 1989
Amplitude information, if properly incorporated along with the phase, can be utilized to improve the discrimination efficiency. In this work, we introduce a novel amplitude modulated phase-only filter (AMPOF) that effectively utilizes both amplitude and phase information and, at the same time, avoids the operational difficulty of the inverse filters. To counter excessive energy absorption and, at the same time, to achieve a significantly uniform filter plane spectrum, one can formulate an AMPOF characterized by D{exp[−jϕ(u, v)]}/[|F(u, v)| + a], where 0 D, and F(u, v) is the object spectrum with phase ϕ(u, v). Parameter a is useful in (i) overcoming the indeterminate condition, (ii) ensuring that the gain is less than unity, and (iii) suppressing noise or bandlimit the filter or both. To discriminate between the object and the filter, the correlation peak energy is normalized with respect to the total output energy. An AMPOF based correlator produces autocorrelation peaks, narrower as well as larger than those of the POF based correlator. Furthermore, it provides a larger value for the ratio of auto- and crosscorrelation powers. A computer-controlled LCTV and MOSLM can be used to store the appropriate filter. A binary AMPOF amplitude mask can be designed using a scheme1 used for fabricating a binary inverse Gaussian filter.