Optical Correlator - Implementation

Implementation

According to Fresnel Diffraction theory a convex lens of focal length will produce the exact Fourier transform at a distance behind the lens of an object placed distance in front of the lens. So that complex amplitudes are multiplied the light source must be coherent and is typically from a laser. The input signal and filter are typically written onto a spatial light modulator or SLM.

A typical arrangement is the 4f correlator. The input signal is written to an SLM which is illuminated with a laser. This is Fourier transformed with a lens and this is then modulated with a second SLM containing the filter. The resultant is again Fourier transformed with a second lens and the correlation result is captured on a camera.