A novel three-dimensional visual inspection scheme for defect detection of transparent materials based on the digital holographic microscopy

Abstract

In the conventional visual inspection system with naked eyes, a camera has been mostly employed for detection of scratches or glass dust, so that it may be difficult to discriminate between the high-grade and the low-grade mass components. Therefore, herewe propose a novel three-dimensional (3-D) visual inspection scheme for effective detection of defects of the transparent materials based on a digital holographic microscopy, which is optically implemented as a form of transmission-typed shearing interferometer. In the proposed method, quantitative data are obtained by converting the phase information of the transparent touch panel or the substrate glass into its depth or thickness information. Then, by using 3-D data extracted from the depth or thickness information of transparent touch panel or substrate glass, we can accurately discriminate between the high-grade and the low-grade mass components. Experiments with test objects confirm the feasibility of the proposed method in the practical applications. Based on these experimental results, the proposed method expects to improve the production yield rate of the original mother glass of the transparent touch panel or the substrate glass used in the LCM.