Rotation-invariant color pattern recognition based on the joint fractional Fourier transform correlator

In this paper, a new system of multi-channel single-output rotation-invariant joint fractional Fourier transform correlator (JFRTC) for color pattern recognition is proposed. Due to the shift-variant property of fractional Fourier transform (FRT), we can obtain three correlation peaks at the output plane which show a pair of cross-correlation peaks that is desired and one autocorrelation peak, so the noise is greatly reduced. The Synthetic discriminate function (SDF) is quoted at the input plane to store the reference images to realize rotation-invariant recognition. To optimize the correlation peaks, the joint power spectrum is binarized to perform Fourier transform. The theoretical analysis and optical experiments are discussed in detail. Experimental results are presented to demonstrate the ability of this system.