푸리에 광학의 디스플레이 기판 결함 검출에의 활용
Application of Fourier Optics to Defect Inspection of Display Substrates
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초록
본 연구에서는 디스플레이 기판의 결함 검출을 위해 푸리에 광학을 이용하는 방법에 대하여 제안하였다. 제안하는 방법은 고배율의 광학계를 사용하지 않기 때문에 비용적 부담이 적은 결함 검출 시스템을 구현하는데 사용될 수 있다. 그리고, 제안하는방법은 고배율 광학계의 짧은 피사계 심도에 기인하는 기판과 카메라 간의 거리 변화에 대한 엄격한 허용오차를 피할 수 있다. 또한, 카메라와 기판의 가까운 거리로 생기는 접촉으로 인한 손상의 가능성을 피할 수 있다. 푸리에 변환의 특성에 의해 규칙적패턴인 기판의 위치변화는 회절된 빛의 세기분포에는 영향을 미치지 않기 때문에 검출 알고리즘을 기존의 방식보다 더 간단하게구현할 수 있다. 제안하는 결함 검출 방법을 전산모사와 함께 설명하고 액정디스플레이의 컬러필터 기판을 예로 실험을 통해검증하였다.
Abstract
A method for inspecting defects in display substrates utilizing Fourier optics is proposed in this paper. A cost-effective inspectionsystem can be realized with the proposed method, because it does not require a high-magnification microscope. Also, the proposedmethod can avoid tight tolerance for variations in displacement between substrate and camera, which is stems from shallow depthof field of the high-magnification microscope. In addition, possible damage caused by collisions between substrate and the inspectionequipment can be avoided. The decision algorithm can be simpler than for a conventional inspection system, because spatial shiftof periodic substrate patterns does not affect the intensity distribution of the diffracted light, by the Fourier transform property. The proposed method is explained with numerical studies, and experiments are carried out to check its feasibility for color-filtersubstrates of a liquid-crystal display.
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