Noncollinear acoustooptic tunable filters using TeO2 crystals are described. An anisotropic Bragg diffraction is studied applying simple design expressions to a tilt type in which an acoustic wave is launched a little off the  axis. Tuning property, filter bandwidth, angular aperture, required acoustic power, deflection angle, divergenceless configuration, and rapid spectrum scanning have been discussed. These filter properties have been confirmed with measurements using three kinds of filter devices: a basic type, an acoustically enhanced type, and a large angular aperture type. A 5-Å bandwidth at 4000 Å was obtained by slow scanning. A 32-Å separation at 4000 Å was observed by a rapid scanning of 0.5 msec throughout the visible region with an extremely low electric drive power.
T. Yano and A. Watanabe, "Acoustooptic TeO2 tunable filter using far-off-axis anisotropic Bragg diffraction," Appl. Opt. 15, 2250-2258 (1976)