Automated Defect Inspection Algorithm Incorporated Spectral-Domain Optical Coherence Tomography for Optical Polarizing Thin Films

Department Of Nuclear Energy Convergence, Kyungil University, Gyeongsan-Si, Gyeongbuk, Korea, ,Byeonggyu Jeon,Ruchire Eranga Wijesinghe,Youngmin Han, ,Mansik Jeon,Jeehyun Kim

doi:10.35940/ijeat.c5515.029320

Department Of Nuclear Energy Convergence, Kyungil University, Gyeongsan-Si, Gyeongbuk, Korea, , Byeonggyu Jeon + Show 5 more

Open Access

https://doi.org/10.35940/ijeat.c5515.029320

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Abstract

Optical polarizing thin film is an optical filter enables light waves of a specific polarization pass through while blocking light waves of other polarizations. Optical polarizing thin films control the brightness of back-light unit for LCD (liquid crystal display) panel, which is essential to produce LCD modules. Defect inspection of polarizing thin films is an important feature during the manufacturing process that is helpful to improve the product quality. In the current study, an automated defect inspection algorithm is introduced and incorporated with a well-known non-destructive and non-contact optical inspection method called spectral domain optical coherence tomography (SD-OCT) to pre-identify defective sub-surface as well as top-surface locations of optical polarizing thin films Polarizing thin films employed in this study consist of 6 layers. The tomographic information, layer information, and defective locations were sufficiently identified through the SD-OCT system owing high-axial resolution. The acquired results indicate the possible application of the proposed system in optical polarizing thin films for the quality assurance.

Highlights

Liquid crystal displays (LCDs) are broadly used in electronic products such as computers and smartphones
Machine vision with a charge-coupled device (CCD) camera–based inspection or electronic inspection have been frequently employed for the quality inspection in optical thin film industry [3, 4]
Since optical polarizing thin films based products are composed of several optical thin films, an optical inspection method with high depth-resolved resolution can be an ideal solution

Summary

INTRODUCTION

Liquid crystal displays (LCDs) are broadly used in electronic products such as computers and smartphones. Machine vision with a charge-coupled device (CCD) camera–based inspection or electronic inspection have been frequently employed for the quality inspection in optical thin film industry [3, 4]. Since these techniques provide information of top surface information, highly penetrating X-ray and computed tomographic techniques were considered for sub-surface, but none of them provides depth resolution at the micro-meter scale [5, 6]. Since optical polarizing thin films based products are composed of several optical thin films, an optical inspection method with high depth-resolved resolution can be an ideal solution. The developed algorithm incorporated OCT provides cross-sectional information with high accuracy, and this study describes how OCT can be beneficial to enhance fault detection in the manufacturing process of LCD panels

MATERIALS AND METHODS

Defect inspection algorithm

OCT cross-sectional and volumetric image assessments

CONCLUSION