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Hara Y.,Nihon University | Kawada N.,Hitachi Ltd. | Shirai K.,Nihon University | Kobayashi Y.,Nihon University | And 3 more authors.
Journal of Japan Institute of Electronics Packaging | Year: 2011

A means of inspecting the height of minute balls using an optical system with two cameras and a lighting system is described. The two cameras detect the minute balls from a vertical direction and from an oblique direction. In the images produced, bright highlights can be observed on the balls. When the height of the minute balls is changed, the position of the bright spots in the oblique image shifts laterally. In order to measure the amount of shift in the image, it is necessary to match the two images to compare the position of the spots. In this study, a method of correcting the distortion of the images is proposed. The method uses a standard pattern in which black circle patterns are regularly arranged to measure distortion. The method can be applied to correcting the asymmetric curve distortion of images. Using this technique, the position error between the two images was corrected to within 0.027809 pixels. The result of an experiment using steel balls with a height change of 100mm is shown. The result shows that the height change can be detected as a spot shift of approximately 10 pixels.

Hara Y.,Nihon University | Tanaka H.,Nihon University | Takizawa S.,Visco Technologies Corporation | Sugano J.,Visco Technologies Corporation
Journal of Japan Institute of Electronics Packaging | Year: 2014

This paper describes an automated method of visually inspecting printed wiring board patterns. With existing inspection methods, a detected pattern is first binarized, and then out-of-rule features or unmatched portions between the detected pattern and the standard pattern are detected as defects. The proposed inspection method detects both deformation and discoloration of the pattern as defects. The conventional inspection method for this purpose subtracts a standard pattern from the pattern to be inspected in gray scale. If the sum of subtraction exceeds the criteria, it is judged that there is a defect in the pattern. This method often gives rise to false alarms, judging deformation within tolerance levels and misalignments as defects. The new inspection method takes account of the direction of the density change of the pattern edge for subtraction. Experimental results revealed the effectiveness of the proposed method to suppress false alarms compared with the conventional method.

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