• Journal of the Korean Society of Radiology
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• v.16 no.7
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• pp.969-974
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• 2022

In order to maximize dynamic range and to minimize image lag in digital X-ray imaging, diminishing residual parasitic capacitance in photodiode in pixels is critically necessary. These requirements are more specifically requested in dynamic X-ray imaging with high frame rate and low image lag for industrial 2D/3D automated X-ray inspection and medical CT imaging. This study proposes duoPIX^TM X-ray imaging sensor for the first time that is composed of reset thin film transistor, readout thin film transistor and photodiode in a pixel. To verify duoPIX^TM X-ray imaging sensor, designing duoPIX^TM pixel and imaging sensor was executed first then X-ray imaging sensor with 105 ㎛ pixel pitch, 347 mm × 430 mm imaging area and 3300 × 4096 pixels (13.5M pixels) was fabricated and evaluated by using module tester and image viewer specifically for duoPIX^TM imaging sensor.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.359-365
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• 2023

In order to satisfy the requirements of dynamic X-ray imaging with high frame rate and low image lag, minimizing parasitic capacitance in photodiode and overlapped electrodes in pixels is critically required. This study presents duoPIX^TM dynamic X-ray imaging sensor composing of readout thin film transistor, reset thin film transistor and photodiode in a pixel. Furthermore, dynamic X-ray detector using duoPIX^TM imaging sensor was manufactured and evaluated its X-ray imaging performances such as frame rate, sensitivity, noise, MTF and image lag. duoPIX^TM dynamic X-ray detector has 150 × 150 mm² imaging area, 73 um pixel pitch, 2048 × 2048 matrix resolution(4.2M pixels) and maximum 50 frames per second. By means of comparison with conventional dynamic X-ray detector, duoPIX^TM dynamic X-ray detector showed overall better performances than conventional dynamic X-ray detector as shown in the previous study.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.10
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• pp.97-107
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• 2015

The initial X-ray images obtained from a digital X-ray machine have a wide data range and uneven brightness level than normal images. In particular, in Chest X-ray images, it is necessary to improve naturally all of the parts such as ribs, spine, tissue, etc. These X-ray images can not be improved enough from conventional image quality enhancement algorithms because their characteristics are different from ordinary images'. This paper proposes to eliminate unnecessary background from an input image and expand the histogram range of the image. Then, we adjust the weight per frequency band of the image for improvement of contrast and sharpness. Finally, jointly taking the advantages of global contrast enhancement and local contrast enhancement methods we obtain an improved X-ray image suitable for effective diagnosis in comparison with the existing methods. Experimental results show quantitatively that the proposed algorithm provides better X-ray images in terms of the discrete entropy and saturation than the previous works.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.3
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• pp.141-148
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• 2023

Accurate overlay metrology is essential to achieve high yields of semiconductor products. Overlay metrology performance is greatly affected by overlay target design and measurement method. Therefore, in order to improve the performance of the overlay target, measurement methods applicable to various targets are required. In this study, we propose a new algorithm that can measure image-based overlay. The proposed measurement algorithm can estimate the sub-pixel position by using a motion vector. The motion vector may estimate the position of the sub-pixel unit by applying a quadratic equation model through polynomial expansion using pixels in the selected region. The measurement method using the motion vector can calculate the stacking error in all directions at once, unlike the existing correlation coefficient-based measurement method that calculates the stacking error on the X-axis and the Y-axis, respectively. Therefore, more accurate overlay measurement is possible by reflecting the relationship between the X-axis and the Y-axis. However, since the amount of computation is increased compared to the existing correlation coefficient-based algorithm, more computation time may be required. The purpose of this study is not to present an algorithm improved over the existing method, but to suggest a direction for a new measurement method. Through the experimental results, it was confirmed that measurement results similar to those of the existing method could be obtained.

• Journal of Intelligence and Information Systems
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• v.28 no.4
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• pp.27-40
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• 2022

Medical AI, which has lately made significant advances, is playing a vital role, such as assisting clinicians with diagnosis and decision-making. The field of chest X-rays, in particular, is attracting a lot of attention since it is important for accessibility and identification of chest diseases, as well as the current COVID-19 pandemic. However, despite the vast amount of data, there remains a limit to developing an effective AI model due to a lack of labeled data. A research that used federated learning on chest X-ray data to lessen this difficulty has emerged, although it still has the following limitations. 1) It does not consider the problems that may occur in the Non-IID environment. 2) Even in the federated learning environment, there is still a shortage of labeled data of clients. We propose a method to solve the above problems by using the self-supervised learning model as a global model of federated learning. To that aim, we investigate a self-supervised learning methods suited for federated learning using chest X-ray data and demonstrate the benefits of adopting the self-supervised learning model for federated learning.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.761-766
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• 2004

Rayleigh fading due to multi-path degrades the mobile service quality, especially high data rate mobile services such as 1xEVDO and W-CDMA. The field test showed that down load date rate of 1xEVDO is seriously affected by Rayleigh fading. To reduce the effect of Rayleigh fading, transmit diversity was implemented in RF repeater. In field test, transmit diversity function increased the data rate about twice comparing with no transmit diversity repeater. Recently high data rate service is getting more important, so transmit diverstiy function will be an important function in repeater.

• Proceedings of the Korean Society of Computer Information Conference
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• 2021.07a
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• pp.73-74
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• 2021

코로나로 인해 X-ray, CT, MRI와 같은 의료영상 분야에서 딥러닝을 많이 접목시키고 있다. 간단히 접할 수 있는 X-ray 영상으로 코로나 진단을 위해 CNN, R-CNN 등과 같은 영상 딥러닝 분야에서 많은 연구가 진행되고 있다. 의료영상 기반 딥러닝 학습은 바이오마커를 정확히 찾아내고, 최소한의 손실률과 높은 정확도를 필요로한다, 따라서 본 논문에서는 높은 정확도를 위한 학습 모델을 선정하고 실험을 진행하였다.

• Tunnel and Underground Space
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• v.29 no.6
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• pp.542-557
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• 2019

The behavior of rock mass is influenced by its microscopic feature of internal structure generating from forming and metamorphic process. This study investigated a new methodology for characterization of rock based on the X-ray CT (computed tomography) images reflecting the spatial distribution characteristics of internal constituent materials. The X-ray image based analysis is capable of quantification of heterogeneity and anisotropy of rock fabric, size distribution and shape parameter analysis of rock mineral grains, fluid flow simulation based on pore geometry image and roughness evaluation of unexposed joint surface which are hardly acquired by conventional rock testing methods.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.129-133
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• 2009

Considerable attention has been focused on digital X-ray systems with transmission. However, only a few attempts have been made using X-ray backscatter systems. This study developed a Data Acquisition System (DAS) for backscattered X-rays. The imaging system used X-ray backscatter at low energy levels, which has unique advantages in terms of acquiring information that cannot be obtained using the transmission system. Such systems are of potential benefit in the medical, industrial, security and military fields because of its practical benefits and the low doses used. The developed system is a similar body scan system. Experiments were carried out using a several metal materials and a fish, which produces results similar to those obtained using the human body during X-ray testing.

• Journal of Internet Computing and Services
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• v.11 no.1
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• pp.21-26
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• 2010

In this paper, film uniformity is improved by the bolt-mapping of convolutional image processing between bolts and a film using soft X-ray based in-line LCD TV film thickness controls. The automatic film thickness analysis of 3 inter-bolt's convolution function is proposed for the reduction of offset error from the X-ray changing of line scan in film profiles.