Formation of two-dimensional image contours in zero and plus second diffraction orders in the process of double Bragg diffraction

We examine a possibility of double Bragg diffraction for two-dimensional image edge enhancement simultaneously in two Bragg orders. Transfer functions of the Bragg orders of double diffraction are obtained taking into account the ellipticity of optical beams and the curvature of the surfaces of the crystal wave vectors. Conditions are found when an image contour is obtained simultaneously in zero and plus second diffraction orders, which is confirmed experimentally using an example of Fourier processing of an image transmitted by radiation at a light wavelength of 0.63 μm. Double Bragg diffraction is implemented on the basis of an acousto-optic cell made of a uniaxial gyrotropic paratellurite crystal operating at a sound frequency of 20.3 MHz.