An improved ultrasonic light deflection system

An ultrasonic light deflection system is described which employs Bragg reflection to varythe direction of a laser beam, producing a linear scan at the horizontal TV rate. About 200 elements can be resolved, a three-fold improvement over a similar system recently reported in the literature. This paper describes the steps which had to be taken to achieve the improvement. Ultrasound in water, in the 30-40 Mc range, is used to obtain Bragg reflection; to change the angle at a linear rate, the frequency is modulated with a sawtooth wave. In the earlier system, the peak-to-peak frequency change was 5 Mc, well within the bandwidth capability of quartz transducers working into water. In the present system, the frequency change is 15 Mc. Ceramic transducers are capable of providing this bandwidth, but their acoustic match to water is poor. An intermediate acoustic section, not involving critical dimensions, flattens the response and improves the match.