Incorporation of Polar Mellin Transform in a Hybrid Optoelectronic Correlator for Scale & Rotation Invariant Target Recognition

In this paper, we show that our proposed hybrid optoelectronic correlator (HOC), which correlates images using spatial light modulators (SLM), detectors and field programmable gate arrays (FPGAs), is capable of detecting objects in a scale and rotation invariant manner, along with the shift invariance feature, by incorporating polar mellin transform (PMT). We also illustrate a key limitation of the ideas presented in previous papers on performing PMT and present a solution to circumvent this limitation by cutting out a small circle at the center of the Fourier Transform which precedes PMT. Furthermore, we show how to carry out shift, rotation and scale invariant detection of multiple matching objects simultaneously, a process previously thought to be incompatible with PMT based correlators. We present results of numerical simulations to validate the concepts.