In this article, we present a bifrequency acousto-optic beam splitter used to select independently the two polarization states of an arbitrary polarized input beam with two acoustic carriers. We make use of a dual frequency anisotropic interaction in the crystal, two acoustic waves diffract the optical beam, each frequency being tuned for interaction with only one of the beam polarizations. We explain how this double interaction is made possible by a proper cut of the paratellurite crystal and for a chosen launching angle of the input beam. In the first part we derive the theory underlying the acousto-optic interaction and the design of the paratellurite device. Then we describe our experimental setup, show some experimental results, and discuss them.

We present a bifrequency acousto-optic tunable filter (AOTF) for applications using polychromatic laser beams. The acousto-optic device is based on two successive anisotropic interactions in paratellurite: the first takes place with an acoustic shear wave tilted at 10 degrees from the [110] axis, while the latter is provided by the acoustic shear wave propagating collinear to the [110] axis. It is then demonstrated that the sidelobes of the impulse response to optical wavelengths of such a bifrequency AOTF are greatly reduced. General expressions of operating frequencies, spectral bandwidths, and acoustic powers are derived. Numerical computations have been drawn for paratellurite. The bifrequency AOTF has been tested using a multiline beam radiated by an argon laser. According to the spectral power distribution of this polychromatic laser beam, the most critical configurations of wavelength filtration have been considered. Experimental results confirm the theoretical predictions.

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The stereoscopic videoprojector developed at our laboratory is based on the simultaneous projection of the left and right images of a stereo-pair along two orthogonal polarization directions of a laser beam. The horizontal scanning system, which deflects four lines simultaneously, led to the design of a specific acoustoelectro-optical modulation device using three independent command variables to control four pixel intensities. This introduces a degradation of the perceived images that we strive to minimize using the information redundancy in the images. In this paper, we first present the principle of operation and the optical modulation device. Then, an optimal solution for the computation of the command variables from the original stereo-pair pixel intensities is proposed and developed. The chosen mathematical criterion is the minimization of the quadratic error between the perceived and original pixel intensities. The study of the visual degradation introduced in the images by the proposed stereo-pair processing leads to the distinction of two kinds of phenomena: the mixing of the pixel intensities in the same image and the mixing of the pixel intensities between the left and right views. The simulations realized with reference images allow a quantitative evaluation of their relative proportions and of the final image quality. © 1998 SPIE and IS&T. [S1017-9909(98) 02203-X]