激光扫描声学显微镜层析成像算法分析-analysis of tomography algorithm of laser scanning acoustic microscope.docxVIP

ABSTRACTABSTRACTIn recent years, many new kinds of materials have been widely used in many military and electronic fields. Because of the material’s complexity in processing or in using, there are many types of defects that may affect its performance and safety seriously. In order to detect the flaw situation in the sample accurately, before detecting their two-dimensional flaws, it is very important to obtain the clear three-dimensional picture of the flaws.SLAM (Scanning Laser Acoustic Microscope) is a type of acoustic microscopy, as a new-type of high-efficient NDT( non-destructive testing) instrument, it is an useful method to study the internal structure of new materials or devices. Using SLAM image system, we can not only get the amplitude image of the internal of the detected object, but also can get its phase image. Therefore through a certain times of projecting, we can obtain the effective reconstruction data, using thecorresponding tomography algorithms and the correction algorithms, we can obtain clear threedimensional tomography picture of the sample which provides the reliable basis for the accurate detecting.The background of this theme, the status of application and the development at home and abroad has been introduced in chapter one. The SLAM system studied in this theme has beenexplained in chapter two, on the SLAM system foundation，the methods to realize the STAM systemhave been introduced. Many kinds of tomography algorithm in the ultrasonic field have been introduced in chapter three. Through analysis of the STAM system, the non-linear diffraction tomography theoretical model has been established, and also the truncated total least squares method has been introduced. In order to realize the algorithm in the STAM system, it has been suitably approximated to the algorithm. The non-linear diffraction theory has been translated into the procedure code in chapter five. Using the multi-frequencies projection picture, the clear tomography pictures of