• Title/Summary/Keyword: 굴절율

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Long-Distance Plume Detection Simulation for a New MWIR Camera (장거리 화염 탐지용 적외선 카메라 성능 광선추적 수치모사)

  • Yoon, Jeeyeon;Ryu, Dongok;Kim, Sangmin;Seong, Sehyun;Yoon, Woongsup;Kim, Jieun;Kim, Sug-Whan
    • Korean Journal of Optics and Photonics
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    • v.25 no.5
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    • pp.245-253
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    • 2014
  • We report a realistic field-performance simulation for a new MWIR camera. It is designed for early detection of missile plumes over a distance range of a few hundred kilometers. Both imaging and radiometric performance of the camera are studied by using real-scale integrated ray tracing, including targets, atmosphere, and background scene models. The simulation results demonstrate that the camera would satisfy the imaging and radiometric performance requirements for field operation.

Tolerance analysis of Multi-Configurative Microscopic System for Inspecting the Wire-Bonding Status of Semiconductor Chips (반도체 와이어 본딩 검사용 다중배치 현미경 광학계에 대한 공차분석)

  • Ryu, Jae-Myung;Kim, Jae-Bum;Kang, Geon-Mo;Jung, Jin-Ho;Baek, Seung-Sun;Jo, Jae-Heung
    • Korean Journal of Optics and Photonics
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    • v.17 no.2
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    • pp.149-158
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    • 2006
  • We have analyzed various tolerances of the multi-configurative microscopic system for inspecting the wire-bonding of a reed frame by using the Gaussian bracket method and the equivalent lens method. The tolerances for the curvature and the thickness, which are axial symmetric tolerances, are given by varying the back focal length within a fecal depth under diffraction-limited conditions. Moreover, by using the trial and error method, the axial non-symmetric tolerances for decenter and tilt are established by assigning the 5% variation of MTF(modulation transfer function) at the spatial frequency of 50 lp/mm and at the field angle of 0.7 field. As the tolerances with the most probable distribution are distributed within the range of the decay rate of less than 5% independent of the probability distribution of tolerances, we can achieve completely the desired design performances of the multi-configurative microscopic system by using the various ranges of these tolerances.

Development of the continuous-wave $Cr^{4+}$: YAG laser with a broad tunability in the infrared region (적외선 영역에서 광대역으로 파장 가변되는 연속 발진 $Cr^{4+}$:YAG 레이저 개발)

  • 추한태;이봉연;양준묵;이동한;임기수;이치원
    • Korean Journal of Optics and Photonics
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    • v.10 no.3
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    • pp.226-232
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    • 1999
  • We have investigated the output power performance of a continuous-wave chromium-doped YAG laser ($Cr^{4+}$:YAG laser), pumped by a Nd: YAG laser. With an output coupler of 1% transmission, we obtained as much as 400 mW of the average output power at 1.450 ${\mu}{\textrm}{m}$. The power slope efficiency of 8%, when the gain medium was cooled to 2$0^{\circ}C$. We tuned the wavelength of the $Cr^{4+}$:YAG laser, at pump power of 6 W, by using birefringent filter. As a result, lasing wavelength was tuned from 1.399 ${\mu}{\textrm}{m}$ to 1.532 ${\mu}{\textrm}{m}$, with the maximum output power of 340 mW at 1.4903 ${\mu}{\textrm}{m}$ and the linewidth was 0.21 nm.

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Computation of Wave Height Distribution Inside a Harbor Using Time-Dependent Mild-Slope Equation (시간의존 완경사방정식을 이용한 항내 파고분포 계산)

  • 곽문수;홍길표;편종근
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.2 no.1
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    • pp.18-27
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    • 1990
  • The calmness inside a harbor plays an important role in the appropriate disposition of har-bor structures. However, it is not easy to get the accurate computational results because they are affected by many factors concerning with the wave transformation. Successful solution also depends on determining the boundary values appropriately. This paper presents the numerical model which is able to calculate wave heights inside a harbor It is based upon the time-dependent mild-slope equation involving wave refraction, diffraction, shoaling effect and reflection. In particular, the arbitrary reflectivity is used at the boundary in order to simulate the real harbor reflection condition. This numerical model is applied for Hupo-Harbor and its validities are investgated by comparing with experimental values from the hydraulic model test as well as computational results from Taka-yama's numerical model (1981). It is shown that the model results are in good agreement with results from hydraulic model and Takayama's.

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원자층증착법을 이용한 Y2O3 박막 형성 및 저항 스위칭 특성

  • Jeong, Yong-Chan;Seong, Se-Jong;Lee, Myeong-Wan;Park, In-Seong;An, Jin-Ho;Rao, Venkateswara P.;Dussarrat, Christian;Noh, Wontae
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.229.2-229.2
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    • 2013
  • Yttrium oxide (Y2O3)는 band gap이 5.5 eV 정도로 상대적으로 넓고, 굴절상수가 1.8, 유전율이 10~15, Silicon 과의 격자 불일치가 작은 특성을 가지고 있다. 또한 녹는점이 높아 열적으로 안정하기 때문에 전자소자 및 광학소자에 다양하게 응용되는 물질이다. Y2O3 박막은 다양한 방법으로 증착할 수 있는데, 그 방법에는 e-beam evaporation, laser ablation, sputtering, thermal oxidation, metal-organic chemical vapor deposition, and atomic layer deposition (ALD) 등이 있다. ALD는 기판 표면에 흡착된 원자들의 자기 제한적 반응에 의하여 박막이 증착되기 때문에 박막 두께조절이 용이하고 step coverage와 uniformity 측면에서 큰 장점이 있다. 이전에는 Y(thd)3 and Y(CH3Cp)3 와 같은 금속 전구체를 이용하여 ALD를 진행하여, 증착 속도가 낮고 defect이 많아 non-stoichiometric한 조성의 박막이 증착되는 문제점이 있었다. 이번 연구에서는, (iPrCp)2Y(iPr-amd)와 탈이온수를 사용하여 Y2O3 박막을 증착하였다. Y2O3 박막 증착에 사용한 Y 전구체는 상온에서 액체이고 $192^{\circ}C$ 에서 1 Torr의 높은 증기압을 갖는다. Y2O3 박막 증착을 위하여 Y 전구체는 $150^{\circ}C$ 로 가열하여 N2 gas를 이용하여 bubbling 방식으로 공정 챔버 내로 공급하였다. Y2O3 박막의 ALD window는 $250{\sim}350^{\circ}C$ 였으며, Y 전구체의 공급시간이 5초에 다다르자 더 이상 증착 두께가 증가하지 않는 자기 제한적 반응을 확인할 수 있었다. 그리고 증착된 Y2O3 박막의 특성 분석을 위해 Atomic force microscopy (AFM)과 X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) 를 진행하였다. 박막의 Surface morphology 는 매끄럽고 uniform 하였으며, 특히 고체 금속 전구체를 사용했을 때와 비교하여 수산화물이 거의 없는 박막을 얻을 수 있었다. 그리고 조성 분석을 통해 증착된 Y2O3 박막이 stoichiometric하다는 것을 알수 있었다. 또한 metal-insulator-metal (MIM) 구조 (Ru/Y2O3/Ru) 의 resistor 소자를 형성하여 저항 스위칭 특성을 확인하였다.

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A Study on the Analytical Method of Artificial Sweeteners in Foods (식품 중 인공감미료의 분석법에 관한 연구)

  • Kim, Hee-Yun;Yoon, Hae-Jung;Hong, Ki-Hyung;Lee, Chang-Hee;Park, Sung-Kwan;Choi, Jang-Duck;Choi, Woo-Jeong;Park, Sun-Young;Kim, Ji-Hye;Lee, Chul-Won
    • Korean Journal of Food Science and Technology
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    • v.36 no.1
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    • pp.14-18
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    • 2004
  • Analysis methods of artificial sweeteners, aspartame, acesulfame potassium, sodium saccharin, and sucralose isolated from foods were developed using high performance liquid chromatography, HPLC conditions for aspartame, acesulfame potassium, and sodium saccharin were: column, Symmetry $C_{18}(3.9mm\;i.d{\times}150mm,\;5{\mu}m)$; mobile phase, 0.05M sodium phosphate monobasic : acetonitrile (9 : 1, pH 3.5, containing 0.01M tetrapropylammonium hydroxide); detector, UV detector at 210 nm. HPLC condition for sucralose were : column, Symmetry $C_{18}(3.9mm\;i.d{\times}150mm,\;5{\mu}m)$; mobile phase, water:methanol (7 : 3); detector, refractive index detection (sensitivity = 16). Recoveries of artificial sweeteners in foods including soft drinks, fruit and vegetable beverages, alcoholic beverages, fermented milk beverages, soybean milk, ice cream, snacks, chewing gums, jam, honey, kimchi salted food, special dietary products, processed fish products, candies, food additive mixtures, chocolate and cocoa were 76.1-101.3%, 82.3-103.2%, 83.1-103.7%, and 80,6-99.5% for aspartame, acesulfame potassium, sodium saccharin, and sucralose, respectively.

Development of Quality Assurance Software for $PRESAGE^{REU}$ Gel Dosimetry ($PRESAGE^{REU}$ 겔 선량계의 분석 및 정도 관리 도구 개발)

  • Cho, Woong;Lee, Jaegi;Kim, Hyun Suk;Wu, Hong-Gyun
    • Progress in Medical Physics
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    • v.25 no.4
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    • pp.233-241
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    • 2014
  • The aim of this study is to develop a new software tool for 3D dose verification using $PRESAGE^{REU}$ Gel dosimeter. The tool included following functions: importing 3D doses from treatment planning systems (TPS), importing 3D optical density (OD), converting ODs to doses, 3D registration between two volumetric data by translational and rotational transformations, and evaluation with 3D gamma index. To acquire correlation between ODs and doses, CT images of a $PRESAGE^{REU}$ Gel with cylindrical shape was acquired, and a volumetric modulated arc therapy (VMAT) plan was designed to give radiation doses from 1 Gy to 6 Gy to six disk-shaped virtual targets along z-axis. After the VMAT plan was delivered to the targets, 3D OD data were reconstructed from 512 projection data from $Vista^{TM}$ optical CT scanner (Modus Medical Devices Inc, Canada) per every 2 hours after irradiation. A curve for converting ODs to doses was derived by comparing TPS dose profile to OD profile along z-axis, and the 3D OD data were converted to the absorbed doses using the curve. Supra-linearity was observed between doses and ODs, and the ODs were decayed about 60% per 24 hours depending on their magnitudes. Measured doses from the $PRESAGE^{REU}$ Gel were well agreed with the TPS doses at central region, but large under-doses were observed at peripheral region at the cylindrical geometry. Gamma passing rate for 3D doses was 70.36% under the gamma criteria of 3% of dose difference and 3 mm of distance to agreement. The low passing rate was resulted from the mismatching of the refractive index between the PRESAGE gel and oil bath in the optical CT scanner. In conclusion, the developed software was useful for 3D dose verification from PRESAGE gel dosimetry, but further improvement of the Gel dosimetry system were required.

Level Set based Topological Shape Optimization of Phononic Crystals (음향결정 구조의 레벨셋 기반 위상 및 형상 최적설계)

  • Kim, Min-Geun;Hashimoto, Hiroshi;Abe, Kazuhisa;Cho, Seonho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.6
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    • pp.549-558
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    • 2012
  • A topology optimization method for phononic crystals is developed for the design of sound barriers, using the level set approach. Given a frequency and an incident wave to the phononic crystals, an optimal shape of periodic inclusions is found by minimizing the norm of transmittance. In a sound field including scattering bodies, an acoustic wave can be refracted on the obstacle boundaries, which enables to control acoustic performance by taking the shape of inclusions as the design variables. In this research, we consider a layered structure which is composed of inclusions arranged periodically in horizontal direction while finite inclusions are distributed in vertical direction. Due to the periodicity of inclusions, a unit cell can be considered to analyze the wave propagation together with proper boundary conditions which are imposed on the left and right edges of the unit cell using the Bloch theorem. The boundary conditions for the lower and the upper boundaries of unit cell are described by impedance matrices, which represent the transmission of waves between the layered structure and the semi-infinite external media. A level set method is employed to describe the topology and the shape of inclusions. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in the level set function, which facilitates to handle complicated topological shape changes. Through several numerical examples, the applicability of the proposed method is demonstrated.

Improvement of the performance of SPPCM using mixed polarized beam and cylindrical lens (혼합 편광빔과 원주면렌즈를 사용한 SPPCM의 성능 개선)

  • Yi, Eun-Hyeong;Kim, Seong-Wan;Kim, Cheol-Su;Kim, Jong-Yun;Lee, Seung-Hee;Lee, Soo-Joong
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.36D no.9
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    • pp.56-63
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    • 1999
  • Conventional method to improve the response time of the Cat-SPPCM was to increase fanning beam using cylindrical lens. But, in this case the temporal instability of this SPPCM is increased, and fanning beam plays a role as noise, so that it decreases the reflectivity. Thus, fanning beam must be controlled to improve the properties of SPPCM. In this paper, we propose the method to increase the reflectivity of SPPCM and decrease the response time by focusing line-shaped input beam into photorefractive crystal using cylindrical lens and decrease the temporal instability of output beam by using mixed-polarized beam instead of simple extraordinary polarized beam. Optical experiments show that the reflectivity of proposed SPPCM is increased twice and the response time is reduced by 15 times. Also, we observed that the temporal instability of SPPCM is reduced when the polarization angle of the mixed-polarized beam is between $10^{\circ}$ and $30^{\circ}$ . We used a $45^{\circ}-cut\;BaTiO_3$ crystal which has high electro-optical coefficients in optical experiments.

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Optical, Structural and Photo-catalytic properties of TiO2 thin films prepared by using Ti-naphthenate (Ti-naphthenate를 이용하여 제조한 광감응성 TiO2 박막의 광학적 및 구조적 특성)

  • Lim, Yong-Moo;Jung, Ju-Hyun;Hwang, Kyu-Seog
    • Journal of Korean Ophthalmic Optics Society
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    • v.10 no.3
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    • pp.185-191
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    • 2005
  • Photo-reactive $TiO_2$ thin films on soda-lime-silica slide glass were prepared by spin coating technique with a Ti-naphthenate precursor. Optical, structural and photo-catalytic properties of the films after annealing at $500^{\circ}C{\sim}600^{\circ}C$ were evaluated. As increase with annealing temperature, absorption bands and total transmittance of the films showing an average transmittance (about 80%) at visible spectra range were shifted to UV spectra range and slightly decreased. Refractive index and thickness of the films were increased from 2.16 to 2.63 and decreased from 484 nm to 439 nm, respectively, with increase of annealing temperature. Anatase phase was visible at all annealing temperature. More rougher surface structure was obtained at $600^{\circ}C$ than those of films annealed at $500^{\circ}C$ and $550^{\circ}C$. The hydrophilic conversion was found within 45 min by UV stimulation and optical activation was UVC>UVA>UVB at the case of $500^{\circ}C{\sim}550^{\circ}C$ and UVA>UVC>UVB at the annealing temperature of $600^{\circ}C$. The lowest initial contact angle was obtained at $600^{\circ}C$.

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