We describe theoretically the function of a nonlinear optical element based
on photoanisotropy in azo-dye-doped polymers for optical correlation. This
element allows the realization of a matched filter with two incoherent lig
ht beams. The described technique involves the insertion of a photoanisotro
pic polymer sample in the Fourier plane of the optical element. Due to the
specific features of photoanisotropic materials the output is characterized
by the convolution of the first wave with the autocorrelation function of
the second wave.