Development of an Automated Optical Inspection System for Mobile Phone Panels

Smart mobile phone is the most popular consumer product nowadays. The quality of the mobile phone panel is important as it gives the first image to potential buyers. Many mobile phone glass panels have the black thin film coating surround the boundary. Some surface defects and uneven coating thickness will degrade the appearance quality of the mobile phone. This research aims to develop a multi-function automated optical inspection system for the mobile phone panels in the production line.Different from some commercial systems that can only identify the 2D surface defects or the 3D film thickness, the developed system is capable of detecting both the 2D defects on the whole panel and the uniformity of 3D film thickness of the glass coating. The 2D surface defects are inspected by the image processing system that can not only extract the defects through the technique of pattern recognition but also classify the defect types by the technique of morphology. The film thickness is measured by a focusing probe utilizing the DVD pickup head as a low cost sensor.Experimental results show that five types of surface defects, including the hole, oil stain, scratch, stripe and edge, can be classified with 100% success rate. The focus probe processed by normalized focus error signal (NFES) technique can achieve both the measurement accuracy and standard deviation less than 0.1 μm.