• Nuclear Engineering and Technology
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• v.33 no.5
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• pp.514-525
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• 2001

Optimum characteristics of digital X-ray sensor components were analyzed to develop intra- oral dental digital X-ray image sensor using indirect method. Parametric analysis was carried out to optimize the phosphor thickness and the fiber optic plate (FOP) coupling to charge coupled device (CCD). X-ray absorption and light diffusion in the phosphor layer were analyzed by the Monte Carlo method. Real time X-ray image was obtained with prototype X- ray image sensor using general CCD camera with 1∼10 Ip/mm resolution. It has been previously shown that large resolution degradation in X-ray images was caused by miss alignment of FOP to CCD and optical adhesive selection. In this study, we reported that X-ray image quality was greatly improved by using optimized characteristics of alignment device and phosphor thickness.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.163-169
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• 2007

In this paper, we propose a method of trigger pulse generation to capture the image on time by making a synchronization between the x-ray generator and digital x-ray image acquisition system. we designed a wireless trigger pulse generation circuit to make a synchronization between x-ray generator and digital image acquisition system and analysis its performance. When it starts to detect a certain level of x-ray radiation or above from the air, this method starts to generate a ACQ_START signal to indicate the timing for image acquisition starting from digital image acquisition system. Hence, when it starts to detect under certain level of x-ray signal from the air, this method starts to generate a ACC_END signal to indicate the timing for image acquisition stop from digital image acquisition system. Image acquisition is activated only this time between ACQ_START and ACQ_END signal. By doing this wireless detecting of x-ray signal from remote, we can get more accurate timing for capturing the x-ray image and any type of x-ray generator can be connected to digital image acquisition system, regards of wired protocol. This makes easy installation. We could get 3.5 line pair / mm resolution at 20 mAs of x-ray level with resolution chart. This is same or better image comparing to conventional wired result.

• Electronics and Telecommunications Trends
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• v.34 no.5
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• pp.1-13
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• 2019

In modern times, X-ray imaging has become a necessary tool for early diagnosis, quality control, nondestructive testing, and security screening. X-ray imaging equipment generally comprises an X-ray generator and an image sensor. Most commercially available X-ray generators employ filament-thermionic electron-based X-ray tubes, thus demonstrating typical analog behavior, such as slow response and large stray X-rays. Furthermore, digital X-ray sources, which have been studied extensively using field electron emitters manufactured from nanometer-scale materials, provide fast and accurately controlled ultra-shot X-rays. This could usher in a new era of X-ray imaging in medical diagnosis and nondestructive inspections. Specifically, digital X-ray sources, with reduced X-ray dose, can significantly improve the temporal and spatial resolution of fluoroscopy and computed tomography. Recently, digital X-ray tube technologies based on carbon nanotubes, developed by Electronics and Telecommunications Research Institute, have been transferred to several companies and commercialized for dental imaging for the first time.

• Journal of Biomedical Engineering Research
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• v.29 no.5
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• pp.364-370
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• 2008

Recent development in large area flat-panel x-ray detector technology enables clinical application of digital tomosyntesis. Unlike conventional motion tomography using x-ray films, flat-panel x-ray detectors provide projection images in digital formats so that tomographic images can be synthesized in a more flexible way. For the digital tomosynthesis, precise movements of the x-ray source and the x-ray detector with respect to a fulcrum point are necessary. In this study, we apply the digital tomosynthesis technique to the flat-panel detector based micro-CT in which the flat-panel detector and the x-ray source rotate together on a circular arc. The experimental results suggest that flat-panel detector based 3D CTs can be used for digital tomosynthesis in the clinical environment.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.1
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• pp.19-22
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• 2007

We developed a low cost digital X-Ray image capturing system using a CCD camera, instead of using the high cost image plate and image intensifier. In order to reduce the system volume, we directly made the dark box shorter than the previous model. Using the graphic language, we developed a program in order for post-processing the images captured by the CCD camera. This program improves the image resolving power.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.572-576
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• 1997

X-ray laminography and DT(digital tomosynthesis) that can form a cross-sectional image of 3-D objects promise to be good solutions for inspecting interior defects of industrial products. The major factors of the digital tomosynthesis that influence on the quality of x-ray cross-sectional images are also discussed. The quality of images acquired from the DT system varies according to image synthesizing methods, the number of images used in image synthesizing, and X-ray projection angles. In this paper, a new image synthesizing method named 'log-root method' is proposed to get clear and accurate cross-sectional images, which can reduce both artifact and blurring generated by materials out of focal plane. To evaluate the quality of cross-sectional images, two evaluating criteria: (1) shape accuracy and (2) clearness in the cross-sectional image are defined. Based on this criteria, a series of simulations were performed, and the results show the superiority of the new synthesizing method over the existing ones such as averaging and minimum method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.31-34
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• 2002

In this paper, the electric properties of amophous selenium multilayer samples has been investigated. In order to develop the hybrid flat-panel digital· X-ray image detector, we measured and analyzed their performance parameters such as the X -ray sensitivity and dark-current for a amophous selenium multilayers X-ray detector with a phosphor layer, The hybrid digital X-ray image detector can be constructed by integrating a phosphor layer (or a scintillative layer) that convert X-ray to a light on a-Se photoconduction mulilayers that convert a light to electrical signal. As results, the dielectric materials such as parylene between the phosphor layer and the top electrode may reduce the dark-current of the samples. Amorphous selenium multilayers having dielectric layer(parylene) has characteristics of low dark-current, high X-ray sensitivity. So we can acquired a enhanced signal to noise ratio. In this paper offer the method can reduce the dark-current in the hybrid X-ray detector.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.395-398
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• 2002

Many research group started study to develope x-ray detector using thin film transistor from 1970. But realization of TFT based x-ray detector development was caused by progress of thin film transistor liquid crystal display(TFTLCD) device technology in 1990. The main current of TFT technology is display device. Research results expend TFT technology field from display device to sensor manufacture technology. These days many research group in the world realize various digital x-ray detector. In this study, We compare discharge erasing method to visible light erasing method in a-Se based digital x-ray detector. Visible light erasing method is known reset process in direct conversion x-ray detector. Digital x-ray detector using visible light erasing method is not adaptive for conventional x-ray device, because of its thickness. And it is not avaliable for real-time imaging for digital fluoroscopy, because of its long reset time. In this study we overcome these limitations and show new idea for real-time imaging method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.32-32
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• 2008

X-ray detector는 의료용, 산업용 등 다양한 분야에서 사용되어지고 있으며 기존의 Analog X-ray 방식의 환경오염, 저장공간 부족, 실시간 분석의 어려움 등의 문제점들을 해결하기 위하여 Digital X-ray로의 전환과 연구가 활발하며 이에 따른 관심도 높아지고 있는 살점이다. Digital X-ray detector는 p-영역과 n-영역 사이에 아무런 불순물을 도핑하지 않은 진성반도체(intrinsic semiconductor) 층을 접합시킨 이종접합 PIN 구조의 photodiode 이다. 이 소자는 역바이어스를 가해주면 p영역과 n영역 사이에서 캐리어 (carrier)가 존재하지 않는 공핍 영역이 발생하게 된다. 이런 공핍 영역에서 광흡수가 일어나면, 전자-정공 쌍이 발생한다. 그리고, 발생한 전자-정공 쌍에 전압이 역방향으로 인가되는 경우, 전자는 양의 전극으로 이동하고, 정공은 음의 전극으로 이동한다. 이와 같이, 발생한 캐리어들을 검출하여 전기적인 신호로 변환 시킨다. 고해상도의 Digital X-ray detector를 만들기 위해서는 누설전류에 의한 noise 감소와 소자의 높은 안정성과 내구성을 위한 높은 breakdown voltage를 가져야 한다. 본 연구에서는 Digital X-ray detector의 leakage current 감소와 breakdown voltage를 높이기 위하여 guradring과 gettering technology를 사용하여 전기적 특성을 분석하였다. 기판으로는 $10k\Omega{\cdot}cm$ resistivity를 갖으며, n-type <111>인 1mm 두께의 4인치 Si wafer를 사용하였다. 그리고 pixel pitch는 $100{\mu}m$이며 active area는 $80{\mu}m{\times}80{\mu}m$인 $32\times32$ array를 형성하여 X-ray를 조사하여 소자의 특성을 평가 하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.366-369
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• 2002

At present, the study of direct digital X-ray detector and indirect digital X-ray detector proceed actively. But it needs high thickness and high voltage in selenium for high ionization rate. Therefore, we carried out the study of electric characteristics of a-Se with additive ratio of Iodine in drafting study for developing Hybrid X -ray Sensor for complementing direct digital X -ray detector and indirect digital X-ray detector in this paper. On this, there are formed Amorphous selenium multi-layers by sticking phosphor layer$(Gd_{2}O_{2}S(Eu^{2+}))$ using optical adhesives of EFIRON Co. Amorphous selenium multi-layers having dielectric layer(parylene) has characteristics of low dark-current, high X-ray sensitivity. So we can acquired a enhanced signal to noise ratio. We make Amorphous selenium multi-layers with $30{\mu}m$ thickness on glass.