Development of an inspection system using an UV wavelength for defects on the thin electrode in a multilayer pattern

Kee Namgung, Sanghee Lim, Jaewan Kim, Jaisoon Kim, Wonshik Choi, James Jungho Pak

Research output: Contribution to journalArticlepeer-review


Generally, the Organic Light-Emitting Diode (OLED), Light-Emitting Diode (LCD), Touch Screen Panel (TSP) glass and Thin Film Transistor (TFT) pattern consists of multiple layers of electrodes separated by thin insulating films. In multilayered devices, when using visible light to inspect the electrode pattern and the defect, the critical shapes of a specific layer are difficult to define. To increase the image contrast between the materials and the layers, this study uses a UV wavelength, which has larger selective differences in reflectance than a visible wavelength. The newly-developed optical system and image analysis units are made to focus on a specific UV range to precisely define a top electrode layer. Two types of magnification systems are developed. Direct side illumination is available in a magnification 1.2 (1.2x) system with a large back focal length (BFL). However, in a magnification 3 (3x) system, on-axis line beam illumination is needed. A multi-point LED source (custom-made) and an anamorphic optical system is used to increase the light efficiency and decrease the noise. Electric units and an algorithm for high-speed image processing and data transfer are also developed. The final images have good selective contrast between the layers despite the high-depth condition decided by the required NA for the target resolution. This system can be used for the inspection of general display panels, Printed Circuit Board (PCB) patterns, and mobile glasses that are composed of multilayered films.

Original languageEnglish
Pages (from-to)631-639
Number of pages9
JournalJournal of the Korean Physical Society
Issue number5
Publication statusPublished - 2014 Sept 1


  • Inspection
  • Line illumination
  • Linear CCD
  • TFT multilayer
  • UV lens

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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