The convergent correlator is widely used but it presents the drawback of the alignment requirements: fine focusing of the input scene Fourier transform on the filter plane, filter centering, scaling the scene Fourier transform to match the filter size, and azimuth matching of the filter with the input scene. We propose a set of tests to obtain a precise alignment of the convergent correlator. These methods are based on frequency filtering properties and they are applicable either for amplitude input or for phase-encoded input. The tests we present allow us to fulfill all the alignment requirements. The theory on which these tests are based is explained. The experimental results obtained during the alignment procedure are presented. We show some additional verifications of the correct alignment of the convergent correlator.
© 2002 Optical Society of America
(070.2590) Fourier optics and signal processing : ABCD transforms
(070.4550) Fourier optics and signal processing : Correlators
(070.6110) Fourier optics and signal processing : Spatial filtering
(100.1160) Image processing : Analog optical image processing
(100.4550) Image processing : Correlators
Josep Nicolás, Juan Campos, Claudio Iemmi, Ignacio Moreno, and María J. Yzuel, "Convergent Optical Correlator Alignment Based on Frequency Filtering," Appl. Opt. 41, 1505-1514 (2002)