• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.4 s.193
• /
• pp.7-14
• /
• 2007

• Proceedings of the Safety Management and Science Conference
• /
• 2004.05a
• /
• pp.283-289
• /
• 2004

The number of pixel defects including bright and black dots on a panel is one of the critical factors determining the quality of TFT-LCD. Since pixel defects on the TFT-LCD panels are sometimes unavoidable, manufacturers have to inspect the panels so that any panel with an unacceptable number of defects will not be delivered to the buyers. However, the buyers demand for the manufacturers to meet different pixel defects tolerances (acceptable number of pixel defects on a TFT-LCD panel) around central(tight) and peripheral(loose) inspection zones. The disagreement in quality standard among different buyers also cause confusions in screening non-confirmative products and unstable yield of production. Few research has focused on the effects of defect locations on a TFT-LCD panel on their detection probabilities and the rational division of defect inspection zones. In this research, experiments were conducted to find the detection probabilities of black dot defects with respect to their varying locations on a TFT-LCD. It is proposed a rational division of inspection zone on a TFT-LCD panel on the basis of detection probabilities of the defects. With these division of inspection zones and the mean defect detection probability within each zone, it is expected to establish a more reasonable pixel defects tolerances.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.946-949
• /
• 2005

This paper deals with the algorithm development that inspects defects such as Bright Defect Dots, Dark Defect Dots, and Line Defect caused by the process of LCD(Liquid Crystal Display). While most of LCD production process is automated, the inspection of LCD panel and its appearance depends on manual process. So, the quality of the inspection is affected by the condition of worker. Especially, the more LCD size increases, the more the worker feels fatigued, which causes the probability of miss judgement. So, the automated inspection is required to manage the consistent quality of the product and reduce the production costs. In this paper, to solve these problems, we developed the imaging processing algorithm to inspect the defects in captured image of LCD. Experimental results reveal that we can recognize various types of defect of LCD with good accuracy and high speed.

• Journal of Broadcast Engineering
• /
• v.18 no.4
• /
• pp.525-534
• /
• 2013

Recently, mura defect inspection techniques are receiving attention in LCD production procedure since demands of TFT-LCD are growing. In this paper, we propose an automatic mura defect inspection method using gabor wavelet transform and DCT. First, we generate a reference panel image using DCT based method. For original panel image and generated reference panel image, we apply a gabor wavelet transform to eliminate texture information in images. Then, we extract mura defect regions from the difference image between gabor wavelet transform image of original panel and generated reference panel image. Finally, all mura defect regions are quantified to detect accurate mura defects. Experimental results show that our method is more accurate and efficient than previous methods.

• Proceedings of the IEEK Conference
• /
• 2003.07e
• /
• pp.1783-1786
• /
• 2003

In this paper, an automated line-defect detection method for TFT-LCD panel is presented. A DFB(Directional Filter Bank) and line-projection method are used to find line-defect which is one of the major defects occurred in TFT-LCD panel. The experimental results show that the proposed algorithm gave promising results for applying automated inspection technique for TFT-LCD panel.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.59-60
• /
• 2006

It is bringing out the importance of automated LCD testing equipment that satisfy a definite quality, confidence and testing speed, as LCD enterprises are recently expanding the production and facility investment in proportion to the sudden increase of LCD demand. So far, LCD inspection is however conducted by manual, or the confidence of existing testing equipment falls short of LCD enterprises's standard. It is therefore important to develop the testing equipment that determines the quality of product for production of an excellent LCD.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.787-790
• /
• 2004

The large size and high brightness backlight system for LCD panel inspection equipment was designed, fabricated, and evaluated. The cold cathode fluorescent lamp (CCFL) instead of the hot cathode fluorescent lamp (HCFL) were used as the light source. The inverters for driving multi-lamp CCFL backlight systems were also designed and fabricated. The measured luminance of the fabricated CCFL backlight system was 20,000 cd/$m^2$ and the uniformity of the backlight was 85%. The fabricated backlight system was successfully applied to the LCD panel inspection equipment.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.7
• /
• pp.1295-1297
• /
• 2008

Large-sized flat-panel displays are widely used for PC monitors and TV displays. In this paper, frequency domain pre-filter algorithms are presented for detection of defects in large-sized Thin Film Transistor-Liquid Crystal Display(TFT-LCD) panel surfaces. Frequency analysis with 1-D, 2-D FFT methods for extract the periodic patterns of lattice structures in TFT-LCD is performed. To remove this patterns, frequency domain band-stop filters were used for eliminating specific frequency components. In order to acquire only defected images, 2-D inverse FFT methods to inverse transform of frequency domain images were used.

• Journal of the Semiconductor & Display Technology
• /
• v.9 no.3
• /
• pp.59-63
• /
• 2010

This paper proposes computer visual inspection algorithms for various LCD defects which are found in a manufacturing process. Modular vision processing steps are required in order to detect different types of LCD defects. Those key modules include RGB filtering for pixel defects, gray-scale morphological processing and Hough transform for line defects, and adaptive threshold for spot defects. The proposed algorithms can give users detailed information on the type of defects in the LCD panel, the size of defect, and its location. The machine vision inspection system is implemented using C language in an embedded Linux system for a high-speed real-time image processing. Experiment results show that the proposed algorithms are quite successful.

• Journal of Korea Multimedia Society
• /
• v.15 no.2
• /
• pp.204-214
• /
• 2012

This paper proposes an image segmentation for a vision-based automated defect inspection system on surface image of TFT-LCD(Thin Film Transistor Liquid Crystal Display) panels. TFT-LCD images have non-uniform brightness, which is hard to finding defective regions. Although there are several methods or proposed algorithms, it is difficult to divide the defect with high reliability because of non-uniform properties in the image. Kamel and Zhao disclosed a method which based on logical stage algorithm for segmentation of graphics and character. This method is a one of the local segmentation method that has a advantage. It is that characters and graphics are well segmented in an image which has non-uniform property. As TFT-LCD panel image has a same property, so this paper proposes new algorithm to segment regions of defects based on Kamel and Zhao's algorithm. Our algorithm has an advantage that there are a few ghost objects around the defects. We had experiments to prove performance in real TFT-LCD panel images, and comparing with the FFT(Fast Fourier Transform) method which is used a bandpass filter.