Study On Synthetic Aperture Focusing Technology In Ultrasonic Casing Imaging System

Ultrasonic imaging detecting technique plays a very important role in the field of non-destructive testing in modern industry and it has become an important method for quantitative detecting. Nowadays ultrasound imaging technique is developed to enhance resolution power.The resolution power in sound and image has become one of the important performance indexes in evaluating ultrasound imaging system.Synthetic aperture focusing technique is one of effective ways to widely improve space resolution power of images in digital imaging processing and is mainly used in the field of radar at present. Synthetic aperture ultrasound technique has been developed since the 1970's and is now at the stage of lab research and small-scale experiments. And its main advantage is that it can realize high resolution power of space to be used in the near area,through the application of small-scale transducer and lower performance frequency. Synthetic aperture focusing technique breaks the limits of classical theories, however, according to researches and applications home and abroad it is seldom applied in engineering.By the application of the general principles of synthetic aperture focusing technique, the main purpose of this paper is to explore the method of improving system performance and of easy digital realization in specific imaging. Based on the analysis of ultrasonic imaging theory, the paper puts forward a signal processing scheme in synthetic aperture focusing technique. Aiming at the application of shaft ultrasound imaging in cased well, the scheme improves imaging resolution power and gives the reasons why space resolution power is superior to conventional imaging.This paper discusses several algorithms of re-fabricating images in synthetic aperture focusing ultrasound imaging. On such a basis, it puts forward the digit quadrature processing method of synthetic aperture to lower sampling rate, reduce operation and storage quantities and presents emulational results. And last the systematic scheme of experimentations based on DSP data acquisition is given and both hardware and softwaredesigns are worked out.