Spatial heterodyning of the output signal from an acousto-optic correlator

In many practical applications of time-integrating acousto-optic correlators, constraints are placed both on the signal and on the devices used in the correlator. These constraints limit control of the spatial carrier frequency on which the output cross-correlation is formed. We examine the theory and present practical results of spatial heterodyning using a diffraction grating applied to a `joint collinear¿¿ interferometric correlator which overcomes this limitation.