• 한국정밀공학회지
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• 제23권3호
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• pp.156-162
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• 2006

Direct fabrication of nano patterns has been studied employing a nano-stereolithography (NSL) process. The needs of nano patterning techniques have been intensively increased for diverse applications for nano/micro-devices; micro-fluidic channels, micro-molds. and other novel micro-objects. For fabrication of high-aspect-ratio (HAR) patterns, a thick spin coating of SU-8 process is generally used in the conventional photolithography, however, additional processes such as pre- and post-baking processes and expansive precise photomasks are inevitably required. In this work, direct fabrication of HAR patterns with a high spatial resolution is tried employing two-photon polymerization in the NSL process. The precision and aspect ratio of patterns can be controlled using process parameters of laser power, exposure time, and numerical aperture of objective lens. It is also feasible to control the aspect ratio of patterns by truncation amounts of patterns, and a layer-by-layer piling up technique is attempted to achieve HAR patterns. Through the fabrication of several patterns using the NSL process, the possibility of effective patterning technique fer various N/MEMS applications has been demonstrated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.490-495
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• 2009

An approach to 3D visualization of multiple sound sources has been developed with the application of a moving array technique. Frequency-domain beamforming algorithm is used to generate a beam power map and the sound source is modeled as a point source. When a conventional delay and sum beamformer is used, it is considered that 2D distribution of sensors leads to have deficiency in spatial resolution along a measurement distance. The goal of moving an array in this study is to form 3D array aperture surrounding multiple sound sources so that the improved spatial resolution in a virtual space can be expected. Numerical simulation was made to examine source localization capabilities of various shapes of array. The 3D beam power maps of hemispherical and spherical distribution are found to have very sharp resolution. For experiments, two sound sources were placed in the middle of defined virtual space and arc-shaped line array was rotated around the sources. It is observed that spherical array show the most accurate determination of multiple sources' positions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.678-681
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• 2003

In conventional optical data storage numerical aperture (NA) cannot be over 1 because of diffraction limit. To overcome this limitation. solid immersion lens(SIL) have produced a great interest in near-field optical data storage. In conventional optical recording method, the dual lens system using object lens and SIL had been studied generally. But the conventional SIL system has some critical problems that must be solved. The problems are heat, contamination. alignment of optical components and so on. To solve these problems. this work proposes enhanced SIL which has several advantages for mechanical and optical issues. This new SIL system named elliptic SIL(ESIL) can use evanescent energy in near-field more effectively. In addition. because of applying the inside recording unlike previous surface recording, ESIL can clear up the problems. The design and analysis of ESIL art executed by using CODE V. Also, in this paper we composed actual data recording system and achieved recording experiment by applying ESIL to magneto-optical recording. In conclusion. we analyze the improvement of aerial density and the reasonability of application to real data storage system.

• 한국생산제조학회지
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• 제21권5호
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• pp.773-777
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• 2012

Recently UV laser micromachining processes is widely introduced to meet the needs of advanced components of IT, BT and ET industries. Due to the characteristics of non-contact and high-speed laser processing, UV laser micromachining is applied to manufacture very thin substrate such as polymer, metals and composite. These minimum line width obtained by UV laser micromachining is generally determined from laser wavelength, optical lens and its numerical aperture. In this paper we will show the lens effect of water droplet on the surface of workpiece to reduce the line width when UV laser light is irradiated and focused through the water droplet. Because of the refraction effect generated by the semi-spherical or spherical shape of water droplet, we can find smaller line width. And water droplet could not only protect thermal deformation, but also carry away burr around micro dent. Firstly fundamental theory of minimum line width was derived from relationship between the geometry of water droplet and laser light trace, and then experimental and simulation results will be finally compared to verify the effectiveness of water droplet lens effect of UV laser micromachining process.

• 한국광학회지
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• 제18권4호
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• pp.286-291
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• 2007

높은 수치구경의 대물렌즈를 사용하는 간섭성 반스톡스 라만 산란 현미경(coherent anti-Stokes Raman scattering microscopy)에서 폴리스틸렌구에서 발생한 신호의 먼거리장 방사패턴에 대한 이론적 계산 연구를 수행하였다. 극초점 조건에서 입사 레이저 광의 전기장 분포를 계산하였고, CARS 신호 생성원인인 비선형 분극(헤르치안 쌍극자) 방사의 간섭성 합을 통하여 먼거리장 방사 패턴을 계산하였다. 폴리스틸렌구의 크기에 따른 후방 방사패턴을 계산하였고, 1100 nm 직경을 가진 폴리스틸렌구와 폴리스틸렌 구껍질의 방사패턴을 비교하였다. 또한, 극초점으로부터 폴리스틸렌구의 중심이 이동함에 따른 방사패턴의 변화를 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권7호
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• pp.3338-3355
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• 2018

Images acquired by Large Aperture Static Imaging Spectrometer (LASIS) exhibit obvious interference stripes, which are vertical and stationary due to the special imaging principle of interference hyperspectral image (IHI) data. As the special characteristics above will seriously affect the intrinsic structure and sparsity of IHI, decomposition of IHI has drawn considerable attentions of many scientists and lots of efforts have been made. Although some decomposition methods for interference hyperspectral data have been proposed to solve the above problem of interference stripes, too many times of iteration are necessary to get an optimal solution, which will severely affect the efficiency of application. A novel algorithm for decomposition of interference hyperspectral images based on split Bregman iteration is proposed in this paper, compared with other decomposition methods, numerical experiments have proved that the proposed method will be much more efficient and can reduce the times of iteration significantly.

• 한국소음진동공학회논문집
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• 제19권9호
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• pp.907-914
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• 2009

An approach to 3D visualization of multiple sound sources has been developed with the application of a moving array technique. Frequency domain beamforming algorithm is used to generate a beam power map and the sound source is modeled as a point source. When a conventional delay and sum beamformer is used, it is considered that 2D distribution of sensors leads to have deficiency in spatial resolution along a measurement distance. The goal of moving an array in this study is to form 3D array aperture surrounding multiple sound sources so that the improved spatial resolution in a virtual space can be expected. Numerical simulation was made to examine source localization capabilities of various shapes of array. The 3D beam power maps of hemispherical and spherical distribution are found to have very sharp resolution. For experiments, several sound sources were placed in the middle of defined virtual space and arc-shaped line array was rotated around the sources. It is observed that spherical array shows the most accurate determination of multiple sources' positions.

• 한국정밀공학회지
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• 제27권12호
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• pp.15-21
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• 2010

Recently, there is a demand for a thermal imaging microscope in the medical field as well as the semi-conductor industry Although the demand of the advanced thermal imaging microscope has been increased, it is very difficult to obtain the technology of developing a thermal camera, because it is used for defense industry. We developed the ${\times}5$ zoom microscope which has $3\;{\mu}m$ spatial resolution to research the design and fabrication of the IR (Infrared) optical system. The optical system of the IR microscope consists of four spherical lenses and four aspheric lenses. We verified individual sensitivity of each optical parameter as the first order approach to the analysis. And we also performed structure and vibration analysis. The optical elements are fabricated using Freeform 700A. The measurement results of surface roughness and form accuracy using NT 2000 and UA3P are Ra 2.36 nm and P-V $0.13\;{\mu}m$. Finally we ascertained resolution power of $3\;{\mu}m$ using USAF (United State Air Force) 1951 IR resolution test chart.

• 한국생산제조학회지
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• 제23권6호
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• pp.636-641
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• 2014

This paper discusses the fabrication process for a Nipkow disk using micro-lens and pinhole disks. The confocal measuring system that uses the Nipkow disk has the advantage in measuring speed, because the Nipkow disk can simultaneously provide confocal images of all pixels in a CCD camera without requiring a lateral scanning unit. A micro-lens configuration, which focuses illumination on a pinhole, overcomes the low optical efficiency of the Nipkow disk system and allows its use in practical applications. This paper describes how to design the Nipkow disk in terms of numerical aperture, particularly for measuring the height of solder bumps in packaging application and for hybrid processes combining mechanical and semiconductor processes.

• 한국생산제조학회지
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• 제26권2호
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• pp.185-192
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• 2017

In this paper, we reviewed major design parameters for a solid type of deployable antenna and its structural design. We performed modal analysis for a single reflector panel made of aluminum and CFRP (carbon fiber reinforced plastic) to confirm the appropriateness of selected materials. We then predicted the elastic modulus of CFRP using the principles of unidirectional composite elasticity stiffness predictions such as the ROM (Rule of Mixture) and HSR (Hart Smith 10% Rule). To optimize the shape of the antenna reflector, a structural stiffness analysis was performed using derived numerical optimization factors. Six structural stiffness analyses were performed using the constructed experimental design method. The resulting optimal shape conditions are proposed to meet the structural stiffness requirements while minimizing weight.