Design of Acousto-Optic Modulators

This chapter discusses the approaches for maximizing the performance of a laser scanning system using an acousto-optic modulator. The temporal response limits of an acousto-optic modulator have been expressed in terms of the acoustic transit time needed for a sound wave front to travel through the incident laser beam, and various mechanisms which practically limit the degree of focus of the incident light have been listed. Acousto-optic component technologies have evolved naturally out of fundamental scientific research into ultrasonics. Among the most powerful tools for studying ultrasonic propagation, absorption, scattering, and reflection phenomena are optimal imaging techniques, especially schlieren imaging. One of the earliest uses of an acousto-optic modulator in an electrooptic system was for large screen projection of television images in theaters, developed in the late 1930s by the Scophony Laboratory in London. A powerful method for analyzing scanner performance is the modulation transfer function, i.e., the contrast ratio response to a sinusoidal video signal.