Research On Image Processing Technique For The Automatic Alignment System

Vision automatic alignment technique is one of the most important techniques in IC encapsulation. The vision automatic alignment system comprises optical lighting system, optical imaging system, CCD camera device, image processing software, control system and so on, in which the high precision image processing algorithms are the determinant part for the final accuracy of alignment.In this thesis, the correlative image processing algorithms are presented to realize rough pose estimation and exact pose estimation of high precision vision alignment, and the following parts are studied:(1)Based on the machine vision theory and automatic alignment technique,the truss of the automatic alignment system is built to realize the automatic grabbing image and alignment.(2)Some parameters are calibrated, such as, the dimension proportion of x axis and y axis, the optical center of the CCD camera and the pixel transform quantum of the imaging system, etc.(3)The alignment masks are partitioned to two groups, one group is rough pose estimation marks, and the other group is exact pose estimation marks. And then the marks were extracted from the image by a series of image processing algorithms, such as, histogram analyses, image filter, binarization, region of interest, edge detection and so on.(4)There are two steps to finish the alignment and obtain high precision. Firstly, feature pattern matching algorithm is proposed to finish rough pose estimation. And secondly, point pattern matching, whose speed is faster and matching precision is higher, is applied to exact pose estimation. Before exact pose estimation, the sub-pixel edge detection that uses the spatial moments of a gray level to determine the location of edge, and the SUSAN corner detector has been attached importance.(5)With the help of the simulated experiments, the precisions of the edge detector and the matching are studied. The results of experiments indicate that the system is provided with higher precision, stronger reliability and practicability.