【作者】 陈雯柏；

【导师】 潘明海；

【作者基本信息】 燕山大学 ， 电路与系统， 2004， 硕士

【摘要】 超声成像检测技术在现代工业无损检测中具有重要地位，已成为定量检测的重要手段。提高分辨率是目前超声成像的发展方向，声像分辨率是评价超声成像系统的最重要的性能指标之一。 合成孔径技术是数字成像处理中用于大幅度改善图像空间分辨率的一种有效手段。目前，合成孔径技术的最主要应用是在雷达领域。合成孔径超声成像自70年代开始发展起来，现在还处于实验室研究及小规模试验阶段。其优点是可以应用小尺度换能器及比较低的工作频率，来获得方位的高分辨率，可以在近场区(菲涅尔区)工作。合成孔径技术突破了经典理论的限制，但从国内外的研究和应用状况来看，工程实际应用还不多见。 本文的主要目的是应用合成孔径技术的一般原理，对应特定的成像问题，寻求提高系统性能，易于数字实现的方法。本文首先介绍了超声成像的理论基础，分析了脉冲回波系统分辨率不高的原因及一般改进措施。在此基础上，针对井壁超声成像在套管井检测的应用实际，建立了提高成像分辨率的合成孔径聚焦成像模型，并对此进行了论证。 本文讨论了合成孔径聚焦超声成像中重构图像的几种算法，在此基础上提出能够降低采样率、减少运算量和存储量的数字正交处理的合成孔径方法，并完成了仿真结果、模拟成像和DSP的实现。最后给出了基于DSP的数据采集处理的成像系统方案和相应的软硬件设计。更多还原

【Abstract】 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.更多还原