Optimization Analysis of Large-Area Full-Field Thickness Measurement Interferometry in Thin Glass Plates

摘要

With the market requirements, glass plates used in flat panel display must be large and thin. In thin glass plates, thickness uniformity has been a key standard in quality identification. To response the requests of industries and manufacturers to large-size glass plate in on-line real-time inspection, the authors recently developed a large-area full-field thickness measurement method named angular incidence interferometry (AII). AII is based on thin film interferometry and uses the point-expanded laser light to illuminate the specimen with an incident angle to generate the particular interference fringes. Due to the regular correlation between the interference fringes, the full-field thickness distribution can be obtained from only one interference fringe pattern (IFP). However, to the thinner glass plates, the thickness non-uniformity may be more serious. In the measurement of AII, modulating the incident angle can effectively eliminate the influence of the serious thickness non-uniformity to the regular correlation between the interference fringes. Therefore, in this paper, the optimization of the incident angle and distance parameters in AII setup was analyzed. The commercially available glass plates with 0.70, 0.55, and 0.33 mm nominal thicknesses were employed to verify the optimization analysis and confirm the measurement feasibility of All in thinner glass plates.