• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.1117-1123
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• 2009

Head fixed type multi-focus display system using Galvano-scanner and DMD(Digital Micro-mirror Device), which is able to perfectly accommodate, can solve eye fatigue due to conflict between convergence eye movement and accommodation action in stereoscopic display. This system is able to accommodate through making convergence point about each view point and offering it in front of observer's pupil by using laser scanning method. In this paper, we analyzed laser scanning method of this multi-focus display system. And multi-focus display system based on this analysis was made, which showed that focus adjustment was possible through video camera. As a result, formation principle of view point of multi-focus system by laser scanning method was verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.6 s.249
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• pp.713-721
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• 2006

Micro-drill wear deteriorates accuracy and productivity of the micro components. In order to improve productivity and qualify of micro components, it is required to investigate micro-drill wear exactly. In this study, a machine vision system is proposed to measure the wear of micro-drills using a precision servo stage. Calibration experiments are conducted to compensate for the machine vision system. In this paper, worn volume, area and length are defined as wear amounts. Micro-drill wear is reconstructed as the 3D topography and the quantized wear amount by using the shape from focus (SFF) method and wear parameters. Experiments have been conducted with HSS twist micro-drills and SM45C carbon steel workpieces. Validity of the proposed machine vision system is confirmed through experiments.

• Journal of the Korean Vacuum Society
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• v.20 no.6
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• pp.403-408
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• 2011

To develop the MFX (Micro-Focus X-ray) tube, the trajectories of electrons emitted from the field emission cathode was simulated using SIMION program. Regardless of starting position of the electron in emitter, we found out the fact that there is the optimum extractor voltage Ve, which can focus the electron beam on one place. Extractor voltage Ve varies depending on the source voltage Vs, but the ratio of two voltages (Ve/Vs) is always constant, its value was 99.4%. When the ratio of two voltages (Ve/Vs) was 99.4%, the beam diameter in the cross-over point was $1.2{\mu}m$. Because the focal spot size in MFXG (Micro-Focus X-ray Generator) can not be less than the cross-over diameter within MFX tube, it is important to find out the conditions that can make a smaller beam diameter. Therefore, the above results is considered to be a very important ones in the development of the MFXG.

• Current Optics and Photonics
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• v.8 no.2
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• pp.170-182
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• 2024

The dimensional accuracy and consistency of a dual oil circuit centrifugal fuel nozzle are important for fuel distribution and combustion efficiency in an engine combustion chamber. A point cloud measurement method was proposed to solve the geometric accuracy detection problem for the fuel nozzle. An improved variance focus measure operator was used to extract the depth point cloud. Compared with other traditional sharpness evaluation functions, the improved operator can generate the best evaluation curve, and has the least noise and the shortest calculation time. The experimental results of point cloud slicing measurement show that the best window size is 24 × 24 pixels. In the height measurement experiment of the standard sample block, the relative error is 2.32%, and in the fuel nozzle cone angle measurement experiment, the relative error is 2.46%, which can meet the high precision requirements of a dual oil circuit centrifugal fuel nozzle.

• The Journal of Engineering Geology
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• v.24 no.2
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• pp.179-189
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• 2014

We analyzed the three-dimensional distribution of micropores and internal structures in both fresh and weathered granite using micro-focus X-ray computed tomography (micro-CT). Results show that the pore radius in fresh granite is mostly in the range of $17-50{\mu}m$, the throat radius is in the range of $5-25{\mu}m$, and the coordination number (CN) of pores is less than 10. In contrast, the pore radius in weathered granite is mostly in the range of $20-80{\mu}m$, the throat radius is in the range of $8-30{\mu}m$, and the CN is less than 12. In general, a positive linear relationship exists between pore radius and CN. In addition, both the size and the density of pores increase with an increasing degree of rock weathering. The size of the throats that connect the pores also increases with an increasing degree of weathering, which induces fracture propagation in rocks. Micro-CT is a powerful and versatile approach for investigating the three-dimensional distributions of pores and fracture structures in rocks, and for quantitatively assessing the degree of pore connectivity.

• Journal of Welding and Joining
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• v.19 no.1
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• pp.88-94
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• 2001

DUPIC (Direct use of spent PWR fuel in CANDU reactors) nuclear fuel is a CANDU fuel fabricated remotely from spent PWR fuel materials in a hot cell. The soundness of the end closure welds of nuclear fuel elements is an important factor for the safety and performance of nuclear fuel. To evaluate the soundness of the end closure welds of DUPIC fuel element, a precise X-ray inspection system is developed using a micro-focus X-ray generator with an image intensifier and a real time camera system. The fuel elements made of Zircaloy-4 and stainless steel by an Nd:YAG laser welding and a TIG welding aye inspected by the developed inspection system. The soundness of the welds of the fuel elements was confirmed by the X-ray inspection process, and the irradiation test of DUPIC fuel elements has been successfully completed at the HANARO research reactor.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.2
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• pp.69-76
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• 2006

TRISO(tri-isotropic)-coated fuel particle technology is utilized owing to its higher stability at a high temperature and Its efficient retention capability for fission products In the HTGR(high temperature gas-reeled reactor). The typical spherical TRISO fuel panicle with a diameter of about 1mm is composed of a nuclear fuel kernel and outer coating layers. The outer coating layers consist of a buffer PyC(pyrolytic carbon) layer, Inner PyC(1-PyC) layer, SiC layer, and outer PyC(O-PyC) layer Most of the Inspection Items for the TRTSO-coated fuel particle depend on destructive methods. The coating thickness of the TRISO fuel particle can be nondestructively measured by the X-ray radiography without generating radioactive wastel. In this study, the coaling thickness for the simulated TRISO-coated fuel particle with $ZrO_2$ kernel Instead of $%UO_2$ kernel was measured by using micro-focus X-ray radiography with micro-focus X-ray generator and flat panel detector The radiographic image was also enhanced by image processing technique to acquire clear boundary lines between coating layers. The coaling thickness wat effectively measured by applying the micro-focus X-ray radiography The inspection process for the TRISO-coated fuel particles will be improved by the developed micro-focus X-ray radiography and digital image processing technology.

• Journal of Biomedical Engineering Research
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• v.28 no.1
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• pp.95-101
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• 2007

Recently, small-animal imaging technology has been rapidly developed for longitudinal screening of laboratory animals such as mice and rats. One of newly developed imaging modalities for small animals is an x-ray micro-CT (computed tomography). We have developed two types of x-ray micro-CT systems for small animal imaging. Both systems use flat-panel x-ray detectors and micro-focus x-ray sources to obtain high spatial resolution of $10{\mu}m$. In spite of the relatively large field-of-view (FOV) of flat-panel detectors, the spatial resolution in the whole-body imaging of rats should be sacrificed down to the order of $100{\mu}m$ due to the limited number of x-ray detector pixels. Though the spatial resolution of cone-beam CTs can be improved by moving an object toward an x-ray source, the FOV should be reduced and the object size is also limited. To overcome the limitation of the object size and resolution, we introduce zoom-in micro-tomography for high-resolution imaging of a local region-of-interest (ROI) inside a large object. For zoom-in imaging, we use two kinds of projection data in combination, one from a full FOV scan of the whole object and the other from a limited FOV scan of the ROI. Both of our micro-CT systems have zoom-in micro-tomography capability. One of both is a micro-CT system with a fixed gantry mounted with an x-ray source and a detector. An imaged object is laid on a rotating table between a source and a detector. The other micro-CT system has a rotating gantry with a fixed object table, which makes whole scans without rotating an object. In this paper, we report the results of in vivo small animal study using the developed micro-CTs.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.97-102
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• 2004

We developed an x-ray cone-beam micro computed tomography (micro-CT) system for small-animal imaging. The micro-CT system consists of a 2-D flat-panel x-ray detector with a field-of-view (FOV) of 120${\times}$120 mm2, a micro-focus x-ray source, a scan controller and a parallel image reconstruction system. Imaging performances of the micro-CT system have been evaluated in terms of contrast and spatial resolution. The minimum resolvable contrast has been found to be less than 36 CT numbers at the dose of 95 mGy and the spatial resolution about 14 lp/mm. As small animal imaging results, we present high resolution 3-D images of rat organs including a femur, a heart and vessels. We expected that the developed micro-CT system can be greatly used in biomedical studies using small animals.

• Transactions of Materials Processing
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• v.13 no.3
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• pp.216-224
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• 2004

In this study, we have developed a new UV$({\lambda}=355nm)$ laser micromachining technology by direct ablation method without masks. This technology allows that 3D micro parts can be fabricated rapidly and efficiently with a low price. And it has a benefit of reducing fabricating process simply. Due to micro parts' fabrication, such technologies need the control of XYZ stages with high precision, the design of optical devices to maintain micron spot sizes of laser beam and the control technology of laser focus. The developed laser manufacturing process for laser micromachining is that, after extracting coordinates of shape data from CAD model data, a beam path considering manufacturing features of laser beam is created by using genetic algorithm. This generated manufacturing process is sent to stage controller. In order to improve the surface quality of micro parts, we have carried out experiments on iteration manufacturing and beam step-over by using a minimum focus size. Moreover, we have fabricated a micro-channel through the developed laser micromachining technology and verified it through the results.