• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.96-97
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• 2000

Incoherent broadband optical sources have been applied in various areas such as a light source for optical device characterization, fiber-optic gyroscopes$^{(1)}$ , and spectrum sliced light source in wavelength division multiplexing (WDM) system$^{(2)}$ . To utilize the inherent low loss in silica optical fibers, various types of incoherent light sources are being developed. Among the light sources, the amplified spontaneous emission (ASE) from a rare earth doped fiber has benefits in temperature stability, high output power, low polarization dependence over semiconductor diodes$^{(3)}$ . Recently erbium doped fibers (EDF) have been intensively researched for ASE sources as well as optical amplifiers$^{(4)}$ . The spectrum of ASE from an EDF, however, is limited in the 1520~1560 nm range in conventional configurations. In this letter we described a new broadband ASE source which included both the conventional ASE band of Er$^{3+}$ ion, 1520nm~1560nm and ASE band from Tm$^{3+}$ ions that extends the bandwidth further. For the first time, to the best knowledge of authors, a fiber ASE source based on the energy transfer between Er$^{3+}$ and Tm$^{3+}$ ions in the range of 1460~1550 nm, has been demonstrated using a single 980nm pump laser diode. (omitted)omitted)

• Journal of the Optical Society of Korea
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• 제17권5호
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• pp.357-361
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• 2013

A regenerative Er-doped fiber amplifier system for a high-repetition-rate optical pulse train is investigated for the first time. A signal pulse train with a wavelength tuning range of 18 nm is produced by a passive mode-locked fiber laser based on a nonlinear polarization rotation technique. In order to realize the amplification, an optical delay-line is used to achieve time match between the pulses' interval and the period of pulse running through the regenerative amplifier. The 16 dB gain is obtained for an input pulse train with a launching power of -30.4 dBm, a center wavelength of 1563.4 nm and a repetition rate of 15.3 MHz. The output properties of signal pulses with different center wavelengths are also discussed. The pulse amplification is found to be different from the regenerative amplification system for CW signals.

• 한국정밀공학회지
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• 제21권11호
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• pp.117-124
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• 2004

Recently, nano-methodology is increasingly important as the ruler for measuring nano-technology, and we applied the linear encoder to nano-methodology. The quadrature output in the linear encoder has an effect on increasing the resolution in some techniques. Already, various interpolation techniques based on the quadrature signal have applied to the precision servo system. In this paper, we propose a new interpolation algorithm for ultra-precision positioning in the low speed with simulation by MATLAB SIMULINK. This method modified previous methods and was properly designed for some given control system. To verify, we first fulfilled the encoder signal test to find main parameters fer the signal transformation, then we proved the proposed interpolation algorithm by experiments, which show that the result of the interpolation algorithm corresponds with the measurement of the laser interferometer in 100 nm unit approximately. In addition, we can get more precise measurement by more accurate and noise-free signal. So we need to compensate imperfections in the encoder signal. After that, we will apply this algorithm to nano positioning system.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.589-596
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• 2008

Performance of a pulsed heat source high temperature inert gas plasma MHD electrical power generator, which can be one of the candidates of space-based laser-to-electrical power converter, is examined by a time dependent two dimensional numerical simulation. In the present MHD generator, the inert gas is assumed to be ideally heated to about $10^4K$ pulsed-likely within short time(${\sim}1{\mu}s$) in a stagnant energy input volume, and the energy of high temperature inert gas is converted to the electricity with the medium of pure inert gas plasma without seeding. The numerical simulation results show that an enthalpy extraction ratio(=electrical output energy/pulsed heat energy) of several tens of % can be achieved, which is the same level as the conventional seeded non-equilibrium plasma MHD generator. Although there still exist many phenomena to be clarified and many problems to be overcome in order to realize the system, the pulsed heat source high temperature inert gas MHD generator is surely worth examining in more detail.

• 센서학회지
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• 제28권5호
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• pp.305-310
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• 2019

The purpose of this study is to classify the concentration of HbA1c (glycosylated hemoglobin), which is an indicator in the management of accurate blood glucose level in diabetic patients, using a non-invasive optical property measurement method. To measure the optical properties of HbA1c, the optical source uses LEDs and laser diodes of 400 nm in the visible region and 1450 nm in the nearinfrared region using thermopile to detect the Raman scattering intensity. An HbA1c control solution was used. As a result, the optical properties of 5% (normal) and 9% (abnormal) HbA1c control solutions showed specificity in which the output values were reversed at 850 nm and 950 nm, respectively. This property was applied to distinguish between normal and abnormal values in diabetes. In addition, considering tissue penetration depths for non-invasive measurements, two wavelengths were determined to be effective in distinguishing the concentrations of HbA1c control solutions at 5%, 7%, and 9%.

• 로봇학회논문지
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• 제14권2호
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• pp.87-93
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• 2019

This paper presents a 6-DOF relocalization using a 3D laser scanner and a monocular camera. A relocalization problem in robotics is to estimate pose of sensor when a robot revisits the area. A deep convolutional neural network (CNN) is designed to regress 6-DOF sensor pose and trained using both RGB image and 3D point cloud information in end-to-end manner. We generate the new input that consists of RGB and range information. After training step, the relocalization system results in the pose of the sensor corresponding to each input when a new input is received. However, most of cases, mobile robot navigation system has successive sensor measurements. In order to improve the localization performance, the output of CNN is used for measurements of the particle filter that smooth the trajectory. We evaluate our relocalization method on real world datasets using a mobile robot platform.

• 대한조선학회논문집
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• 제57권6호
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• pp.373-380
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• 2020

We have developed the hybrid prototype load cell structures. These developed load cell structures may increase the reliability of the load sensing by deriving the load values through the double sensing method through the vertical maximum deflection and bending stress of the simple beams. For this purpose, the structure design was performed so that the load value, the deflection and stress value could be output to the same value through the optimal structure design. The structurally designed dimensions reaffirmed the accuracy of the design through the structural analysis program and the matching of the load value and the deflection value. Based on the designed structural dimension, the prototype form was constructed through laser cutting and production using hot rolled steel materials. The developed prototype load cell structure can be used as good educational material in various subjects such as material mechanics, steel structure design, measurement engineering, and mechatronics engineering. It is also believed that the measurement system ideas can inform the occurrence of errors in the event of a problem, and if a major accident caused by a sensing error is predicted, it will show good utilization to prevent accidents.

• Tribology and Lubricants
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• 제37권1호
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• pp.1-6
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• 2021

This paper presents the experimental results of hydrophobic surfaces developed using a stereolithography-based additive-manufacturing technique. The additive manufacturing technique can be used to manufacture objects with complex geometries from computer-aided design data. Several additive manufacturing methods, such as selective laser sintering, fused deposition modeling, stereolithography apparatus (SLA), and inkjet-based system, have been developed. The SLA is a form of three-dimensional printing technology used to create prototypes, patterns, and production parts in successive layers through photochemical processes. Light causes chemical monomers and oligomers to cross-link together to form objects composed of polymers. Moreover, this method is economical for fabricating surfaces with high output resolution and quality. Here, we fabricate various surfaces using different shapes using an SLA. The surfaces with micro-patterns are fabricated for 10 cases, including the biomimetic surface. The fabricated surfaces with various micro-patterns are evaluated for hydrophobicity performance based on the static contact angle. The contact angle is measured three times for each case, and the averaged value is used. The results indicate that the arrangements in a staggered structure have a larger contact angle than those in a line when the same micro-pattern is applied. Moreover, the mimetic surfaces exhibit more hydrophobic characteristics than those of artificial micro-patterns.

• 한국광학회지
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• 제29권6호
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• pp.241-246
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• 2018

본 논문에서는 광섬유 브래그 격자(FBG)를 이용한 광온도센서를 제작하였으며 광원은 출력 파장의 온도 의존성을 가지는 저가형 VCSEL이 사용되며 FBG에서 반사되는 빛의 파장을 분석하는 interrogator는 VCSEL에서 변화되는 출력 파장을 VCSEL의 내부 온도로 확인하는 방법을 적용하여 저가격의 광온도센서를 구현하였다. VCSEL의 내부온도를 $52.2^{\circ}C$에서 $14^{\circ}C$까지 조절하면서 출력 파장을 1519.90 nm에서 1524.25 nm까지 총 4.35 nm 파장을 변화시켰으며 온도 조절에 따른 파장 변화 반복도 오차는 ${\pm}0.003nm$이며 온도 측정 오차는 ${\pm}0.18^{\circ}C$로 측정되었다. 광온도센서를 사용하여 $22.3{\sim}194.2^{\circ}C$의 온도를 측정한 결과 인가한 온도 ${\Delta}T$에 따른 광원 내부 온도 변화 값은 $0.146^{\circ}C/{\Delta}T$이고 인가한 온도 ${\Delta}T$에 따른 온도 프로브 반사 파장 변화 값(${\Delta}{\lambda}_{\beta}T/{\Delta}T$)은 $16.64pm/^{\circ}C$로 측정되었으며 센서의 측정 오차는 ${\pm}1^{\circ}C$로 나타났다. VCSEL의 출력 파장은 온도에 의존성을 가지고 있어 좁은 범위의 출력 파장을 변화시키기 위한 광원으로 사용하기에 매우 적합하다.

• Journal of Periodontal and Implant Science
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• 제27권3호
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• pp.603-619
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• 1997

레이저를 이용한 연조직 수술은 출혈이 없어 시야를 좋게 하고 시술시간이 단축되며, 술후 종창이 최소화 되고, 통증이 감소화 최소화된 반흔 형성, 그리고 레이저가 조사되는 일부 부위의 멸균효과등이 장점이 있어 최근에 의학분야 및 치의학분야에서 많이 사용되는 추세에 있다. 이에 본 연구에서는 $CO_2$레이저를 이용한 백서의 치은절제술시의 치유과정과 레이저 출력을 달리 하였을때의 치유과정을 관찰하기 위해, 백서의 상악전치의 치은조직에서 치은절제술 효과를 얻을 수 있는 최소 출력인 4watts를 이용한 부위를 대조군으로, 6watts를 이용한 부위를 실험군으로 하여, 술후 2일, 3일, 1주, 3주후에 각각 실험동물을 희생시켜 치유결과를 조직학적으로 비교 관찰하여 다음과 같은 결과를 얻었다. 대조군과 실험군 모두에서 2일째에서만 작은 크기의 혈병이 관찰되었고, 그 이후에서는 관찰되지 않았다. 2. 염증세포 침윤지역 크기는 대조군과 실험군 모두에게 2일째 가장 컸으며, 그 크기는 시간이 경과될수록 줄어들어 2주째는 거의 소실되었으며, 실험군의 경우 대조군에 비해 2,3째까지 크기가 더 컸으나, 1주째부터는 크기의 차이가 관찰되지 않았다. 3. 육아조직은 대조군, 실험군 모두 시간의 경과에 따라 점점 성숙되어, 2주째부터는 거의 정상 치은 결합조직으로 대체되는 소견을 보였고, 3주째에서는 완전한 치유양상을 보였다. 실험군의 경우 대조군보다 3일째까지는 그 크기가 더 컸으나 1주째부터는 크기의 차이가 없다. 4. 대조군과 실험군 모두에게 치은의 상피화하는 2일째에서 시작되는 소견을 보였고, 1주부터 상피돌기와 부분적인 접합상피의 재생이 관찰되었으며, 2주째부터는 구강열구상피의 각화가 시작되어 3주째에는 각화의 완성이 관찰되었다.