An Image-Superposition Technique for Measuring Time Between Ultrasonic Echoes

摘要

An image-superposition technique has been developed for accurately measuring the time interval between two ultrasonic echoes. The measurement is made by alternately shifting displayed images of the echoes so that the images are superposed. The amount of shifting is controlled by digital circuitry in such a way that the time interval is the inverse of the frequency of a recurrent square wave. This frequency is measured very accurately by a frequency counter. The accuracy of the final results is limited mainly by the properties of the specimen and ultrasonic apparatus, and by the characteristics of ultrasonic pulses. Including the effects of these factors, measurements are accurate to within a few tenths of a percent. (Author)