Introduction
The correlator has an input signal which is multiplied by some filter in the Fourier domain. An example filter is the matched filter which uses the cross correlation of the two signals.
The cross correlation or correlation plane, of a 2D signal with is
This can be re-expressed in Fourier space as
where the capital letters denote the Fourier transform of the lower case letter. So the correlation can then be calculated by inverse Fourier transforming the result.
Read more about this topic: Optical Correlator
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