• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.299-302
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• 1995

Recently, we proposed a 3-D range-image measuring system for a slowly moving object by mechanically scanning a laser light beam emitted from a self mixing laser diode. In this paper, we introduced that every object moves along a straight line course, which is set diagonally against the semiconductor laser beam so that we can recognize each shape and size parameters of objects separately from the acquired 3-D range-image. We measured a square mesa on a square plane as an object. The measured velocity was 4.44mm/s and 4.63mm/s with an error of 0.56mm/s to 0.37mm/s. And thickness error of the mesa was 0.5mm to 0.6mm, which was obtained from the 3-D range-image of the standstill or moving object with thickness of 17.Omm.

• 대한방사선치료학회지
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• 제6권1호
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• pp.89-93
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• 1994

Authors have measured virtual source distance of electron beam from CL/1800 medical linear accelerator, with newly designed method. Beam scanning was performed with the direction of beam axis in the air. Compared results between this study and well established in phantom measurement shows good agreement with in experimental error. And we have found that build-up cap plays very important role in air measurement because of charge build up. The method of in-air measurement of virtual source distance is very easy to set-up and generate accurate results.

• Imaging Science in Dentistry
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• 제36권3호
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• pp.123-129
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• 2006

The use of computed tomography for dental procedures has increased recently. Cone beam computed tomography (CBCT) systems have been designed for imaging hard tissues of the dentomaxillofacial region. CBCT is capable of providing high resolution in images of high diagnostic quality. This technology allows for 3-dimensional representation of the dentomaxillofacial skeleton with minimal distortion, but at lower equipment cost, simpler image acquisition and lower patient dose. Because this technology produces images with isotropic sub-millimeter spatial resolution, it is ideally suited for dedicated dentomaxillofacial imaging. In this paper, we provide a brief overview of cone beam scanning technology and compare it with the fan beam scanning used in conventional CT and the basic principles of currently available CBCT systems.

• 한국의학물리학회지:의학물리
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• 제18권4호
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• pp.226-232
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• 2007

국립암센터에 설치된 양성자 치료기의 빔 전달 시스템에 대하여 Geant4 코드를 이용하여 몬테카를로 전산모사를 수행하였고, 선량검증 도구로써의 이용 가능성에 대하여 연구하였다. 몬테카를로 기술을 기반으로 하는 선량계산은 물질내의 선량분포를 이해하는 데 가장 정확한 방법으로 알려져 있다 외부조사 방사선치료에 있어서 이 방법의 장점을 극대화 하기 위해서는, 빔이 지나가는 곳에 놓여진 노즐 구성요소들의 정확한 모델링과 더불어 초기빔 특성파악은 무엇보다 중요하다. 국립암센터에 설치된 양성자 치료기는 총 3가지 형태-double/single scattering, uniform scanning and pencil-beam scanning-로 치료빔을 조사할 수 있으며, 본 연구진은 Geant4.8.2 코드를 기반으로 double/single scattering 모드를 구성하는 모든 노즐구성요소들에 대하여 모델링 하였다. 특정 치료감이에 대하여 실험치와 일치하는 전산모사의 결과를 얻었다 본 기관에 설치된 양성자치료기에 대한 몬테카를로 전산모사에 대한 기반을 성공적으로 구축하였고, 치료빔에 대하여 정밀한 선량측정에 이용할 수 있다. 치료빔의 전 에너지 영역에 걸쳐 추가적인 커미셔닝을 수행할 것이다.

• 방사선산업학회지
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• 제5권1호
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• pp.41-46
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• 2011

Polyacrylonitrile (PAN) fibers are the most widely used precursor of the materials for carbon fibers. The conventional process of carbon fibers from PAN precursor fiber includes two step; stabilization at low temperature and carbonization at high temperature. Compared to thermal stabilization, the stabilization process by electron beam (E-beam) irradiation is a advanced and brief method. However, a stabilization by E-beam irradiation was required a high dose (over 5,000 kGy) and spend over 1.5 hr (1.14 MeV, 1 mA). In the present work the main goal is exploring a quick stabilization process by cotrolling E-beam currents. The effect of various E-beam currents on stabilization of PAN precursor fiber was studied by gel fraction test, thermo gravimertic analysis (TGA), differential scanning calorimetry (DSC), tensile strength, and scanning electron microscopy (SEM) images.

• 한국의학물리학회지:의학물리
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• 제27권3호
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• pp.162-168
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• 2016

Proton therapy is increasingly being actively used in the treatment of cancer. In contrast to photons, protons have the potential advantage of delivering higher doses to the cancerous tissue and lower doses to the surrounding normal tissue. However, a range shifter is needed to degrade the beam energy in order to apply the pencil beam scanning technique to tumors located close to the minimum range. The secondary neutrons are produced in the beam path including within the patient's body as a result of nuclear interactions. Therefore, unintended side effects may possibly occur. The research related to the secondary neutrons generated during proton therapy has been presented in a variety of studies worldwide, since 2007. In this study, we measured the magnitude of the secondary neutron dose depending on the location of the detector and the use of a range shifter at the beam nozzle of the proton scanning mode, which was recently installed. In addition, the production of secondary neutrons was measured and estimated as a function of the distance between the isocenter and detector. The neutron dose was measured using WENDI-II (Wide Energy Neutron Detection Instruments) and a Plastic Water phantom; a Zebra dosimeter and 4-cm-thick range shifter were also employed as a phantom. In conclusion, we need to consider the secondary neutron dose at proton scanning facilities to employ the range shifter reasonably and effectively.

• 한국광학회지
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• 제19권2호
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• pp.132-139
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• 2008

주사 레이저 광집게에서 대물렌즈에 의해 집속된 레이저 초점을 제어하기 위해 사용되는 고속 구동기는 입력 신호의 주파수가 증가함에 따라 출력이 감소한다. 이러한 입출력의 괴리는 CCD 카메라를 통해 관찰이 어려우며 사용자는 희미하게 보이는 레이저 주사 형상을 보고 물체를 조작하여 물체를 포획할 수 없거나 포획하더라도 안정된 제어를 할 수 없다. 본 연구에서는 이러한 문제를 해결하기 위해 사용된 고속 구동기의 주파수 특성을 분석하고, 이를 바탕으로 입력 주파수에 따른 실제 주사 경로를 측정하여 시각화해주는 방법과 입출력 데이터의 차이를 계산하여 입력 데이터를 보상하는 방법을 제안한다.

• Imaging Science in Dentistry
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• 제48권2호
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• pp.111-119
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• 2018

Purpose: This study was conducted to evaluate the accuracy of linear measurements of 3-dimensional (3D) images generated by cone-beam computed tomography (CBCT) and facial scanning systems, and to assess the effect of scanning parameters, such as CBCT exposure settings, on image quality. Materials and Methods: CBCT and facial scanning images of an anthropomorphic phantom showing 13 soft-tissue anatomical landmarks were used in the study. The distances between the anatomical landmarks on the phantom were measured to obtain a reference for evaluating the accuracy of the 3D facial soft-tissue images. The distances between the 3D image landmarks were measured using a 3D distance measurement tool. The effect of scanning parameters on CBCT image quality was evaluated by visually comparing images acquired under different exposure conditions, but at a constant threshold. Results: Comparison of the repeated direct phantom and image-based measurements revealed good reproducibility. There were no significant differences between the direct phantom and image-based measurements of the CBCT surface volume-rendered images. Five of the 15 measurements of the 3D facial scans were found to be significantly different from their corresponding direct phantom measurements(P<.05). The quality of the CBCT surface volume-rendered images acquired at a constant threshold varied across different exposure conditions. Conclusion: These results proved that existing 3D imaging techniques were satisfactorily accurate for clinical applications, and that optimizing the variables that affected image quality, such as the exposure parameters, was critical for image acquisition.

• Journal of the Optical Society of Korea
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• 제5권3호
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• pp.99-109
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• 2001

This paper presents a phase-only modulation scheme for a three-dimensional (3-D) image matching system to improve optical efficiency of the system. The 3-D image matching system is based on the two mask heterodyne scanning. A hologram of the 3-D reference object is first created and then the phase of the hologram is extracted. The phase of the hologram is represented as one mask with the other mask being a plane wave. The superposition of each beam modulated by the two masks generated a scanning beam pattern. This beam pattern scans the 3-D target object to be recognized. The output of the scanning system gives out the correlation of the phase-only hologram of the reference object and the complex hologram of the target object. Since a hologram contains 3-D information of an object as a form of fringe pattern, the correlation of holograms matches whole 3-D aspect of the objects. Computer simulations are performed with additive gaussian noise and without noise for the complex hologram modulation scheme and the phase-only hologram modulation scheme. The computer simulation results show that the phase-only hologram modulation scheme improves the optical efficiency. Thus the system with the phase-only hologram modulation scheme is more robust than the system with the complex hologram modulation scheme.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.1085-1088
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• 2001

The process of styrofoam pattern that has been used for material of press die pattern depends chiefly on handwork. Laser manufacturing system developed to increase precision and efficiency of process that is also able to convert the design easily. Applying the RP(rapid prototyping) concept reversely, the unnecessary part of section is vapored away by heat source of laser beam after converting 3-D CAD model into cross-sectional shape information. Laser beam is line-scanned in plane specimens to measure the depth and width of cut, surface roughness, cross-sectional shape as converting laser power, scanning speed, cutting gas pressure. With these basic data, plane surface, inclined surface, hole, outer contour trimming process is experimented and optimum condition are obtained. In plane and inclined surface experiments, 15W laser power and 50mm/s scanning speed make superior processing property and 30W, 10mm/s make processing efficiency increase in trimming process. With these results, simple patterns were manufactured and the possibility of applying laser manufacturing system to styrofoam pattern was convinced.