• Journal of the Optical Society of Korea
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• 제15권1호
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• pp.22-29
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• 2011

We analyze aberrations in an optical laser printer system in order to know how to determine an allowable non-uniformity of the movement of a light spot, how to determine allowed variation of spot sizes, and how to minimize the influence of these deviations on technological errors. In this paper, the correction and the tolerance of distortion are analyzed by using the concept of zonal and global distortions. The tolerance of field curvature is also obtained from Gaussian beam properties. In order to reduce the change of the entrance pupil position and to make a more compact laser printer system the minimum size of the rotator is exactly derived from the geometry with the introduction of the shift angle of the input beam.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1883-1886
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• 2005

In this paper, a decoupled dual servo (DDS) stage for ultra-precision scanning system with large working range is introduced. In general, dual servo systems consist of a fine stage for short range and a coarse stage for long range. The proposed DDS also consists of a $XY\theta$ fine stage for handling and carrying workpieces and one axis coarse stage. Its coarse stage consists of air bearing guide system and a coreless linear motor with force ripple. The fine has four voice coil motors(VCM) as its actuator. According to a VCM's nature, there are no mechanical connections between coils and magnetic circuits. Moreover, VCM doesn't have force ripples due to imperfections of commutation components of linear motor systems - currents and flux densities. However, due to the VCM's mechanical constraints the working range of the fine is about $25mm^2$. To break that hurdle, the coarse stage with linear motors is used to move the fine about 500mm. Because of the above reasons, the proposed DDS can achieve higher precision scanning than other stages with only one servo. With MATLAB's Sequential Quadratic Programming (SQP), the VCMs are optimally designed for the highest force under conditions and constraints such as thermal dissipations due to its coil, its size, and so on. And for their movements without any frictions, guide systems of the DDS are composed of air bearings. To get precisely their positions, a linear scale with 5nm resolution are used for the coarse stage's motion and three plane mirror laser interferometers with 5nm for the fine's $XY\theta$ motions. With them, on scanning the two stages have same trajectories. The control algorithm is named Parallel method. The embodied ultra-precision scanning system has sub 100nm following error and in-positioning stability.

• 대한환경공학회지
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• 제28권2호
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• pp.150-157
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• 2006

태양산란광을 광원으로 사용하고 DOAS(differential Optical Absorption Spectroscopy) 기술을 이용하여 분석 하여 대기 오염물질의 이차원 공간적 분포를 이미지화 할 수 있는 지상용 원격 모니터링 장비인 Imaging-DOAS 시스템을 소개한다. 인공적 램프를 광원으로 사용하는 능동형 DOAS와 마찬 가지로 수동형 DOAS 기술도 대기 가스상의 물질의 차등흡수 변화(narrow band absorption) 구조를 이용하여 $NO_2,\;SO_2,\;CH_2O$ 등의 다양한 물질을 높은 정밀도를 가지며 측정 할 수 있다. Imaging-DOAS는 스캐닝 거울, 집광 렌즈, 분광기와 CCD, 그리고 시스템을 통합 제어하는 소프트웨어로 이루어져 있으며, 스캐닝 거울로 여러 번 스캐닝을 연속적으로 하여 대기 가스물질의 공간적 이차원 분포를 이미지화 시킨다. 본 연구에서는 개발된 Imaging-DOAS 시스템 구조 및 수신된 신호를 이용한 분석 방법을 소개 하며 처음으로 국내 한 화력 발전소에서 발생되는 $NO_2$ 양의 공간적 분포를 Imaging-DOAS를 이용하여 원격 측정 하였다.

• 지질공학
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• 제12권4호
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• pp.405-419
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• 2002

새롭게 개발된 레이저 콘포컬 현미경을 이용해 암석 불연속면의 거칠기를 측정하였다. 레이저의 파장은 488 nm이며, 현미경은 두 개의 galvano-meter scanner mirror를 이용한 광 편광법에 의해 제어된다. 레이저 반사를 통한 자동 초점기능은 관찰대상을 빠르고 정확하게 측정할 수 있다. 이 현미경은 기존의 다른 콘포컬 현미경에 비해 광축방향의 해상도를 크게 개선하였고, 특수 제작한 현미경 스테이지를 이용해 최대 $10{\;}{\times}{\;}10{\;}cm$ 까지 크기의 시료를 측정할 수 있다. 측정간격은 x와 y 방향으로 $2.5{\;}\mu\textrm{m}$씩이며, z방향의 최대 측정해상도는 $10{\;}\mu\textrm{m}$로서, 다른 방범에 비해 훨씬 정확하다. 조립질과 세립질의 입도가 다른 화강암을 대상으로 인장시험(Brazilian test)를 통해 인공절리를 생성시켰고, 생성된 좌우의 절리면에 각각 3개씩의 측선을 설정하였다. 각 측선을 따라 측정한 높이는 1차원은 물론 거칠기의 세밀한 양상을 보여주는 2차원과 3차원의 디지털 이미지로 표현된다. 조립질 화강암의 1차원 단면은 세립질보다 불연속면의 기복이 더 심함을 잘 보여준다. 거칠기를 정량적으로 특성화하고 거칠기를 구성하는 성분 중 가장 큰 영향을 미치는 성분을 파악하기 위해 고속퓨리에 변환 (FFT)를 이용한 스펙트럼 분석을 실시하였다. 스펙트럼 분석결과 저주파 성분이 큰 시효의 경우 거칠기의 기복변화가 심하고 긴 파장을 나타내는 경향이 있음을 구명하였다.

• 센서학회지
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• 제16권2호
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• pp.85-90
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• 2007

This paper presents the growth conditions and characteristics of polycrystalline 3C-SiC (silicon carbide) thin films for M/NEMS applications related to harsh environments. The growth of the 3C-SiC thin film on the oxided Si wafers was carried out by APCVD using HMDS (hexamethyildisilane: $Si_{2}(CH_{3})_{6})$ precursor. Each samples were analyzed by XRD (X-ray diffraction), FT-IR (fourier transformation infrared spectroscopy), RHEED (reflection high energy electron diffraction), GDS (glow discharge spectrometer), XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope) and TEM (tunneling electro microscope). Moreover, the electrical properties of the grown 3C-SiC thin film were evaluated by Hall effect. From these results, the grown 3C-SiC thin film is very good crystalline quality, surface like mirror and low defect. Therefore, the 3C-SiC thin film is suitable for extreme environment, Bio and RF M/NEMS applications in conjunction with Si fabrication technology.

• Journal of the Optical Society of Korea
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• 제11권4호
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• pp.162-172
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• 2007

Scanning Laser Optical Tweezers(SLOT) is an optical instrument frequently employed on a microscope with laser being delivered through its various ports. In most SLOT systems, a mechanical tilt stage with a mirror on top is used to dynamically move the laser focal point in two-dimensions. The focal point acts as a tweezing spot, trapping nearby microscopic objects. By adding a mechanical translational stage with a lens, SLOT can be expanded to work in three-dimensions. When two mechanical stages operate together, the focal point can address a closed three-dimensional volume that we call a workspace. It would be advantageous to have a large workspace since it means one can trap and work on multiple objects without interruptions, such as translating the microscope stage. However, previous studies have paid less consideration of the volumetric size of the workspace. In this paper, we propose a new method for designing a SLOT such that its workspace is maximized through optimization. The proposed method utilizes a matrix based ray tracing method and genetic algorithm(GA). To demonstrate the performance of the proposed method, experimental results are shown.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1924-1926
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• 2001

A novel wet release process ($\mu$ CARP - Micro Channel Assisted Release Process) for releasing an extreme large-area plate structure without etching hole is proposed and experimented. Etching holes in conventional process reduce a effective area and degrade an optical characteristics by a diffraction. In addition, as the area of a released structure increases, the stietion becomes more serious. The proposed process resolves these problems by the introduction of a micro fluidic channel beneath the structure which will be released. In this paper, a 5 mm${\times}$5mm-single crystal silicon plate structure was released by the proposed $\mu$CARP without etch holes on the structure. The variation in etching time with respect to the of the introduced micro channel is also examined. This process is expected to be beneficial for the actuator of a nano-scale data storage and the scanning mirror.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.348-351
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• 1995

A modified silicon direct bonding method has been developed alloying an intimate contact between grooved and smooth mirror-polished oxide-free silicon wafers. A regular set of grooves was formed during preparation of heavily doped $p^+$-type grid network by oxide-masking und boron diffusion. Void-free bonded interfaces with filing of the grooves were observed by x-ray diffraction topography, infrared, optical. and scanning electron microscope techniques. The presence of regularly formed grooves in bending plane results in the substantial decrease of dislocation over large areas near the interface. Moreover two strongly misoriented waters could be successfully bonded by new technique. Diodes with bonded a pn-junction yielded a value of the ideality factor n about 1.5 and the uniform distribution of series resistance over the whole area of horded pn-structure. The suitability of the modified technique was confirmed by I - V characteristics of power diodes and reversly switched-on dynistor(RSD) with a working area about $12cm^2$. Both devices demonstrated breakdown voltages close to the calculation values.

• 대한기계학회논문집B
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• 제24권6호
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• pp.769-776
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• 2000

Visible spectral characteristics of cross-sectional emissions from a partially premixed methane/air and propane/air flames have been investigated. An optical train with a two-axis scanning mirror system was used to record line-of-sight emission spectra from 354nm to 618nm, and inversion technique was adapted to obtain cross-sectional emission spectra. By analyzing the reconstructed emission spectra, cross-sectional intensities of CH and $C_2$ radicals were separated from the background emissions. The blue flame edge and yellow flame edge were also obtained by image processing technique for edge detection with color photograph of flame. These edges were compared with radial distributions of CH, $C_2$ radicals and background emissions. The CH radicals were observed at blue flame edge. The background emissions were generated by soot precursor at upstream of flame and by soot at downstream of flame. The $C_2$ radicals in propane/air flame were observed more than those in methane/air flame.

• 한국전기전자재료학회논문지
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• 제19권8호
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• pp.732-736
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• 2006

This paper describes the physical characterizations of polycrystalline 3C-SiC thin films heteroepitaxially grown on Si wafers with thermal oxide, In this work, the 3C-SiC film was deposited by LPCVD (low pressure chemical vapor deposition) method using single precursor 1, 3-disilabutane $(DSB:\;H_3Si-CH_2-SiH_2-CH_3)\;at\;850^{\circ}C$. The crystallinity of the 3C-SiC thin film was analyzed by XPS (X-ray photoelectron spectroscopy), XRD (X-ray diffraction) and FT-IR (fourier transform-infrared spectometers), respectively. The surface morphology was also observed by AFM (atomic force microscopy) and voids or dislocations between SiC and $SiO_2$ were measured by SEM (scanning electron microscope). Finally, residual strain was investigated by Raman scattering and a peak of the energy level was less than other type SiC films, From these results, the grown poly 3C-SiC thin film is very good crystalline quality, surface like mirror, and low defect and strain. Therefore, the polycrystalline 3C-SiC is suitable for harsh environment MEMS (Micro-Electro-Mechanical-Systems) applications.