Abstract
A system for inspecting flat panel displays (FPDs) acquires scanning images using multiline charge-coupled device (CCD) cameras and industrial machine vision. Optical filters are currently installed in front of these inspection systems to obtain high-quality images. However, the combination of optical filters required is determined manually and by using empirical methods; this is referred to as passive color control. In this study, active color control is proposed for inspecting FPDs. This inspection scheme requires the scanning of images, which is achieved using a mixed color light source and a mixing algorithm. The light source utilizes high-power light emitting diodes (LEDs) of multiple colors and a communication port to dim their level. Mixed light illuminates an active-matrix organic light-emitting diode (AMOLED) panel after passing through a beam expander and after being shaped into a line beam. The image quality is then evaluated using the Tenenbaum gradient after intensity calibration of the scanning images. The dimming levels are determined using the simplex search method which maximizes the image quality. The color of the light was varied after every scan of an AMOLED panel, and the variation was iterated until the image quality approached a local maximization. The number of scans performed was less than 225, while the number of dimming level combinations was 20484. The proposed method can reduce manual tasks in setting-up inspection machines, and hence is useful for the inspection machines in FPD processes.
Highlights
Flat panel displays (FPDs) have become an essential component in consumer electronics, and their market is expected to expand at a compound annual growth rate (CAGR) of 5.8% by 2020
A scanning stage was installed on an optical table that was isolated from floor vibrations
As initial simplex size increased in small ranges, the Tenenbaum gradient became higher at termination
Summary
Flat panel displays (FPDs) have become an essential component in consumer electronics, and their market is expected to expand at a compound annual growth rate (CAGR) of 5.8% by 2020. Previous studies on FPD inspection focused on defect detection based on acquired images, but little attention has been paid to the determination of the light color and intensity with the aim of maximizing image quality. The algorithm controls the activation of the mixed light source, the acquisition of scanning images, correction of non-uniform luminance, calculation of image quality index (IQI), and the adjustment of the dimming level of the light source. Automatic color lighting was proposed in our previous studies; the focus was on non-repetitive patterns in a small area [17] As such, they are not suitable for these FPD inspection processes.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call