| dc.description.abstract | Recently, the inspection of manufactured products is an important industrial activity. The inspection of solar cells is not widespread and the advanced techniques are still pursued. In this paper, the studies automatic optical inspection methods for detecting defects and scale measurement on the solar cells are proposed.
The proposed system includes several inspection items: scale measurement, V-shape defect detection, and line defect detection of printed solar cells. In scale measurement, we use subpixel edge detection, Hough transform, and LSM to detect and accurately allocate edges on solar cells. The detected edges are also used for detecting the V-shape defect on the solar cell boundaries. We proposed a subpixel edge detection method based on the Catmull-Rom spline to accurately locate the edges. In line defect detection, there are two types of lines: busbars and fingers. We use a tracking method to inspect the defects on busbars and use a template matching method to inspect the defects on fingers. The detector can extract four-type defects on busbars: concave, convex, pinhole, and interruption and extract three-type defects on fingers: concave, convex, and interruption.
In the experiments, the solar images of size 2048×2048 are evaluated. We measure the real size of solar cells by a 3D CCD for comparison with the measured scales to test the accuracy of the proposed measurement methods. Three pieces of solar cells are taken to evaluate the repeatability of the measurement. Almost 100 percentage defects can be detected by the proposed methods; moreover, the average inspection time is only 1.86 seconds for all defect types run on a PC with Intel Pentium 4 2.4GHz CPU. The experimental results show that the proposed approaches almost reach the practical stage. | en_US |