Automatic Defect Detection for TFT-LCD Array Process Using Quasiconformal Kernel Support Vector Data Description

Defect detection has been considered an efficient way to increase the yield rate of panels in thin film transistor liquid crystal display (TFT-LCD) manufacturing. In this study we focus on the array process since it is the first and key process in TFT-LCD manufacturing. Various defects occur in the array process, and some of them could cause great damage to the LCD panels. Thus, how to design a method that can robustly detect defects from the images captured from the surface of LCD panels has become crucial. Previously, support vector data description (SVDD) has been successfully applied to LCD defect detection. However, its generalization performance is limited. In this paper, we propose a novel one-class machine learning method, called quasiconformal kernel SVDD (QK-SVDD) to address this issue. The QK-SVDD can significantly improve generalization performance of the traditional SVDD by introducing the quasiconformal transformation into a predefined kernel. Experimental results, carried out on real LCD images provided by an LCD manufacturer in Taiwan, indicate that the proposed QK-SVDD not only obtains a high defect detection rate of 96%, but also greatly improves generalization performance of SVDD. The improvement has shown to be over 30%. In addition, results also show that the QK-SVDD defect detector is able to accomplish the task of defect detection on an LCD image within 60 ms

A Review and Analysis of Automatic Optical Inspection and Quality Monitoring Methods in Electronics Industry

Electronics industry is one of the fastest evolving, innovative, and most competitive industries. In order to meet the high consumption demands on electronics components, quality standards of the products must be well-maintained. Automatic optical inspection (AOI) is one of the non-destructive techniques used in quality inspection of various products. This technique is considered robust and can replace human inspectors who are subjected to dull and fatigue in performing inspection tasks. A fully automated optical inspection system consists of hardware and software setups. Hardware setup include image sensor and illumination settings and is responsible to acquire the digital image, while the software part implements an inspection algorithm to extract the features of the acquired images and classify them into defected and non-defected based on the user requirements. A sorting mechanism can be used to separate the defective products from the good ones. This article provides a comprehensive review of the various AOI systems used in electronics, micro-electronics, and opto-electronics industries. In this review the defects of the commonly inspected electronic components, such as semiconductor wafers, flat panel displays, printed circuit boards and light emitting diodes, are first explained. Hardware setups used in acquiring images are then discussed in terms of the camera and lighting source selection and configuration. The inspection algorithms used for detecting the defects in the electronic components are discussed in terms of the preprocessing, feature extraction and classification tools used for this purpose. Recent articles that used deep learning algorithms are also reviewed. The article concludes by highlighting the current trends and possible future research directions.Framework of the IQONIC Project; European Union’s Horizon 2020 Research and Innovation Program

Mathematical modelling and analysis of industrial manufacturing of liquid crystal displays

This thesis considers the mathematical modelling and analysis of the widely used One Drop Filling (ODF) method for the industrial manufacturing of liquid crystal displays. In the first part of the thesis, we consider three problems relating to the fluid dynamics of nematic liquid crystals (nematics) in the ODF method. In particular, we formulate and analyse a simple model for the squeezed coalescence of several nematic droplets, a squeeze-film model for a single nematic droplet, and a model for pressure-driven channel flow of nematic. Our results give significant insight into nematic flow effects in the ODF method and indicate that these effects could play an essential role in forming unwanted optical effects, known as ODF mura. In the second part of the thesis, we consider a static ridge of nematic resting on an ideal solid substrate surrounded by passive fluid. The analysis of this system gives insight into the initial stage of the ODF method and more general situations involving nematic free surfaces and three-phase contact lines. Specifically, we derive the governing equations for a static ridge, which include nematic Young and Young–Laplace equations, and then use these governing equations to study two related problems. Firstly, we consider the situation in which the ridge is thin and has pinned contact lines. Secondly, we use the nematic Young equations to determine the continuous and discontinuous transitions between the equilibrium states of complete wetting, partial wetting, and complete dewetting that can occur.This thesis considers the mathematical modelling and analysis of the widely used One Drop Filling (ODF) method for the industrial manufacturing of liquid crystal displays. In the first part of the thesis, we consider three problems relating to the fluid dynamics of nematic liquid crystals (nematics) in the ODF method. In particular, we formulate and analyse a simple model for the squeezed coalescence of several nematic droplets, a squeeze-film model for a single nematic droplet, and a model for pressure-driven channel flow of nematic. Our results give significant insight into nematic flow effects in the ODF method and indicate that these effects could play an essential role in forming unwanted optical effects, known as ODF mura. In the second part of the thesis, we consider a static ridge of nematic resting on an ideal solid substrate surrounded by passive fluid. The analysis of this system gives insight into the initial stage of the ODF method and more general situations involving nematic free surfaces and three-phase contact lines. Specifically, we derive the governing equations for a static ridge, which include nematic Young and Young–Laplace equations, and then use these governing equations to study two related problems. Firstly, we consider the situation in which the ridge is thin and has pinned contact lines. Secondly, we use the nematic Young equations to determine the continuous and discontinuous transitions between the equilibrium states of complete wetting, partial wetting, and complete dewetting that can occur

Testing of displays of protection and control relays with machine vision

Human-machine interface is the link between a user and a device. In protection and control relays the local human machine interface consist of a display, buttons, light-emitted diode indicators and communication ports. Human-machine interfaces are tested before assembly with visual inspection to ensure quality of LCDs and LEDs. The visual inspection test system of HMIs consists of a camera and lens, a light emitted diode analyser, software and a computer. Machine vision operations, such as corner detection and template matching, are used to process and analyse captured images. Original camera and measurement device set-up have been used several years, and it should be upgraded. New camera and lens were installed in the system, and the aim of the thesis was to evaluate and improve the testing set-up and software to support each other, to get better images, and further, to improve the first pass yield. Camera position and settings were adjusted to capture images with good quality. Features of upgraded set-up and software were tested, and development ideas are given for further improvement. Changes in the set-up and software show promising results by giving more accurate test results from production.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Calibration Methods of Characterization Lens for Head Mounted Displays

This thesis concerns the calibration, characterization and utilization of the HMD Eye, OptoFidelity’s eye-mimicking optical camera system designed for the HMD IQ, a complete test station for near eye displays which are implemented in virtual and augmented reality systems. Its optical architecture provides a 120 degree field of view with high imaging performance and linear radial distortion, ideal for analysis of all possible object fields. HMD Eye has an external, mechanical entrance pupil that is of the same size as the human entrance pupil. Spatial frequency response (the modulation transfer function) has been used to develop sensor focus calibration methods and automation system plans. Geometrical distortion and its relation to the angular mapping function and imaging quality of the system are also considered. The nature of the user interface for human eyes, called the eyebox, and the optical properties of head mounted displays are reviewed. Head mounted displays consist usually of two near eye displays amongst other components, such as position tracking units. The HMD Eye enables looking inside the device from the eyebox and collecting optical signals (i.e. the virtual image) from the complete field of view of the device under test with a single image. The HMD Eye under inspection in this thesis is one of the ’zero’ batch, i.e. a test unit. The outcome of the calibration was that the HMD Eye unit in this thesis is focused to 1.6 m with an approximate error margin of ±10 cm. The drop of contrast reaches 50% approximately at angular frequency of 11 cycles/degree which is about 40% of the simulated values, prompting improvements in the mechanical design. Geometrical distortion results show that radial distortion is very linear (maximum error of 1%) and that tangential distortion has a diminishable effect (0.04 degrees of azimuth deviation at most) within the measurement region

Amorphous In-Ga-Zn-O Thin-Film Transistors for Next Generation Ultra-High Definition Active-Matrix Liquid Crystal Displays.

Next generation ultra-high definition (UHD) active-matrix flat-panel displays have resolutions of 3840x2160 (4K) or 7680x4320 (8K) pixels shown at 120 Hz. The UHD display is expected to bring about immersive viewing experiences and perceived realness. The amorphous In-Ga-Zn-O (a-IGZO) thin-film transistor (TFT) is a prime candidate to be the backplane technology for UHD active-matrix liquid crystal displays (AM-LCDs) because it simultaneously fulfills two critical requirements: (i) sufficiently high field-effect mobility and (ii) uniform deposition in the amorphous phase over a large area. We have developed a robust a-IGZO density of states (DOS) model based on a combination of experimental results and information available in the literature. The impact of oxygen partial pressure during a-IGZO deposition on TFT electrical properties/instability is studied. Photoluminescence (PL) spectra are measured for a IGZO thin films of different processing conditions to identify the most likely electron-hole recombination. For the first time, we report the PL spectra measured within the a IGZO TFT channel region, and differences before/after bias-temperature stress (BTS) are compared. To evaluate the reliability of a-IGZO TFTs for UHD AM-LCD backplane, we have studied its ac BTS instability using a comprehensive set of conditions including unipolar/bipolar pulses, frequency, duty cycle, and drain biases. The TFT dynamic response, including charging characteristics and feedthrough voltage, are studied within the context of 4K and 8K UHD AM-LCD and are compared with hydrogenated amorphous silicon technology. We show that the a-IGZO TFT is fully capable of supporting 8K UHD at 480 Hz. In addition, it is feasible to reduce a-IGZO TFT feedthrough voltage by controlling for non-abrupt TFT switch-off.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111526/1/ekyu_1.pd

Promocijas darbs

Elektroniskā versija nesatur pielikumusŠajā darbā ir izklāstīti šķidro kristālu difuzoru projektēšanas un optimizācijas laikā iegūtie rezultāti, to ražošanas tehnoloģija un pielietojums uz galvas nēsājamos paplašinātās realitātes displejos. Šķidro kristālu difuzori tiek pielietoti liela izmēra displejiem, taču to pielietojums tuvu lietotāja acīm izvirza jaunas prasības attiecībā uz ļoti maziem izmēriem un augstu kontrastu, kā arī caurspīdīgumu. Piemērotas modelēšanas izmantošana šķidro kristālu sastāva projektēšanai un zināmo materiālu izmantošanas un tehnoloģijas optimizēšanai ļauj izpildīt augstāk minētās prasības ar samazinātu eksperimentālā darba apjomu. Gadījumos, kad tradicionālos displeju materiālus nevarēja izmantot, tika izstrādāti citi materiāli, proti, silīcija oksinitrīda plānās kārtiņas ar maināmu laušanas koeficientu.This thesis presents the results obtained during design and optimization of liquid crystal diffusers, their production technology and application in augmented reality head mounted displays. Liquid crystal diffusers have been proven for large form factor displays but their application for near eye distances provide new requirements in terms of very small dimensions, and high contrast and transparency. Using appropriate physical modelling to designing liquid crystal composition and for optimizing employment and technology of known materials, allows to fulfil above mentioned requirements with reduced volume of experimental work. In cases when traditional display technology materials could not be applied, other materials were developed, namely silicon oxy nitride thin films with variable index of refraction

Economic impact failure mode and effects analysis

Failure mode and effects analysis (FMEA) is a method for reducing or eliminating failure modes in a system. A failure mode occurs when a system does not meet its specification. While FMEA is widely used in different industries, its multiple limitations can cause the method to be ineffective. One major limitation is the ambiguity of the risk priority number (RPN), which is used for risk prioritization and is the product of three ordinal variables: severity of effect, probability of occurrence, and likelihood of detection. There have been multiple attempts to address the RPN's ambiguity, but more work is still needed. Any new risk prioritization method needs to have a decision-support system to determine when to implement a corrective action or improvement.This research addresses some of the shortcomings of traditional FMEA through the creation of a new method called Economic Impact FMEA (EI-FMEA). EI-FMEA replaces the three ordinal values used in the RPN calculation with a new set of variables focusing on the expected cost of a failure occurring. A detailed decision-support system allows for the evaluation of corrective actions based on implementation cost, recurring cost, and adjusted failure cost. The RPN risk prioritization metric is replaced by the economic impact value (EIV) risk prioritization metric which ranks risks based on the impact of the corrective action through the largest reduction in potential failure cost. To help with resource allocation, the EIV only ranks risks where the corrective actions are economically sustainable.A comparison of three FMEA methods is performed on a product, and the risk prioritization metrics for each method are used to determine corrective action implementation. An evaluation of the FMEA methods are shown, based on the expected failure cost reduction, using the decision-support criteria of each method.The EI-FMEA method contributes to the body of knowledge by addressing the ambiguity of the RPN in FMEA by creating the EIV risk prioritization metric. This allows the EI-FMEA method to reduce failure cost by providing a decision-support system to determine when to implement a corrective action when both finite and infinite resources are available