Abstract
The electron beam employed to scan the conversion plate of an ultrasonic image converter serves as a switching device, which momentarily connects individual elements of the plate to the termination. If sufficient time has lapsed since their previous interrogation, these elements possess a considerable amount of stored energy due to resonant vibration. With continuous-wave illumination of uniform intensity, and with constant sweep velocity, the energy flowing to the termination consists of a constant-amplitude component of the same frequency as the driving source, and transient components due to switching from one element to the next. The constant-amplitude component may be associated with the impinging ultrasonic signal and the others associated with release of energy stored in the plate. Calculations show that the signal due to release of stored energy increases with beam sweep velocity, and may exceed the amplitude of the steady-state signal obtained by holding the beam in a stationary position.
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