• Korean Journal of Construction Engineering and Management
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• v.24 no.4
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• pp.52-59
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• 2023

Flatness inspection of PC elements is normally conducted manually by inspectors at manufacturing sites. However, the manual inspection is error-prone and subjective, so it is necessary to develop a robust and efficient flatness measurement method. Recently, a few studies of laser scanner-based flatness inspection have been conducted. However, little attention on field applicability in terms of accuracy, time and cost has been paid. To tackle the limitation, this study aims to compare three sensing method including floor profiler, terrestrial laser scanner and total station for flatness inspection of PC elements. A series of experiments on two full-scale PC slabs were conducted and the results show that the laser scanning method is the most suitable for the PC elements flatness inspection in the aspects of accuracy, time and cost.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.484-493
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• 2004

A new lightwave locking technique which can be used in tuning the wavelength of a local laser diode to the reference wavelength is presented in this paper. The optical frequency from the reference laser source and the optical frequency from the local slave VCO laser are heterodyned on a optical receiver, resulting in the 1.5GHz RF signal corresponding to the difference frequency between two input optical signals. The difference frequency is locked to the reference 1.5GHz oscillator source in off-set frequency locking loop. Using the commercialized microwave components, frequency difference detector can be easily established to lock the lightwave. The optical frequency of 1.55um laser diode which keeps the frequency off-set of 1.5GHz is locked to the input reference optical signal with the locking range of 320MHz.

• Journal of the Korean Geosynthetics Society
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• v.16 no.1
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• pp.1-8
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• 2017

Displacement of dams by various instrumentations has been monitored for its safety management and analyzing the behavior after a dam collapse accident. However, unknown displacement of dam has frequently been occurred and it's difficult to analyze behavior of dams more accurately. In this study, improvement of reliabilities for displacement of dams measured by a total station was suggested by calibrating the monitoring system. The position of total station was initially measured through 2-3 given points and the coordinate of the total station was considered as an absolute value. Also, base horizontal and vertical angles had not been considered even if they are important factors when displacement was estimated. In this study, location of the total station and variations of base horizontal and vertical angles were investigated during measuring displacements of targeting points. From the results of this study, they are important factors which are affecting measurements of dam displacements. Before the calibrating, the displacement at 50 m from total station was ${\pm}20mm$. After the calibrating, the displacement was decreased by ${\pm}5mm$.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.148-149
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• 2000

파장분할다중(WDM) 광통신시스템에서 광원의 파장을 정확하게 측정하는 것은 매우 중요하다. 지금까지 광파장측정기는 격자나 Fabry-Perot 에탈론을 사용한 광대역 필터(optical bandpass filter) 및 파장에 따라 삽입손실이 다른 파장판별기(wavelength discriminator)등으로 구현되었지만 빛의 간섭 현상을 이용한 마이켈슨 간섭계가 가장 많이 사용되었다. 특히 푸리에 변환 마이켈슨 간섭계 파장측정기$^{(1)}$ 는 동시에 각각 다른 파장의 광원들이 입사되더라도 각각의 파장을 측정할 수 있는 장점이 있다. 즉 마이켈슨 간섭계에서 주기적인 간섭무늬에 의한 광검출기의 출력은 입력된 광파장에 따라 다른 주기를 가진다. 따라서 서로 다른 파장을 가진 빛이 입사했을 때 검출되는 각각의 광전력의 합을 표본화(sampling)한 뒤 FFT를 거치면 광파장과 광검출기로 수신한 신호의 중심 주파수의 관계를 알 수 있으므로, 서로 다른 파장을 가진 빛이 입사하더라도 각각의 파장을 측정할 수 있는 것이다. 본 논문에서는 푸리에 변환을 이용하되 마이켈슨 간섭계 대신 마하젠더 간섭계형 광변조기를 이용하여 광파장을 측정에 관한 실험적 구현과 개선 방안에 대해 제시한다. (중략)

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.11
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• pp.85-90
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• 1998

A 1 4 polymeric optical power divider based on the multimode interference effect is designed and fabricated. The two dimensional finite difference beam propagation method has been utilized in designing the device. Polymers used for the core layer and the cladding layer are Cyclotene-3022 and UV-15, respectively. The device is fabricated by the reactive ion etching method. The splitting ratio of the fabricated device is 0.93 : 1.00 : 0.93 : 0.90 for TE mode and 0.84 : 0.94 : 1.00 : 0.83 for TM mode. The advantages of this device are small size and low polarization-dependence.

• 한국IT서비스학회:학술대회논문집
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• 2010.05a
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• pp.162-165
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• 2010

우리나라 대형 건설시장의 하나인 터널 시공은 계획 대비 많은 물량과 자재의 소모로 인해 이들 정보의 지속적 관리를 통한 정확한 물량 및 자재 산출 정보 예측에 대한 관심이 꾸준히 요구되고 있는 실정이다. 대부분의 시공현장에서는 굴진의 정확도 검측을 위해 광파기를 사용하고 있다. 광파기는 공사 초기 시부터 유지된 원점으로부터의 정확한 좌표를 사용하고 있어 취득된 정보는 신뢰할 수 있으나, 몇 개의 기준점을 측량하여 굴진방향 및 공사의 진척도를 평가하는 방식이므로, 전체적인 면을 측정하지 못한다는 단점이 있다. 이에 반하여 3차원 스캐너는 제원에 따른 반경 내의 모든 점들을 계측하여 그 정보를 선이 아닌 면으로써 파악하지만 위치에 대한 정확도를 포함할 수 없다. 이러한 문제점을 보완하기 위하여, 광파기와 3차원 스캐너를 동시 활용하는 본 시스템은 현장에서 소모된 자원의 정확한 양을 체크하여 굴진정도를 파악하여 공사의 전반적인 진도를 관리할 수 있다. 또한 여굴의 발생 여부를 직접 확인하고 계획대비 소모된 물량정보를 통해 자재관리를 할 수 있게 된다. 마지막으로 추후 발생할 수 있는 하자에 대한 정확한 근거를 제시하여 균열 및 누수 등에 대한 정확한 원인 파악을 제공할 수 있다는 장점들을 제공한다.

• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.21-26
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• 2002

In the conventional star coupler, a certain amount of loss should be expected because lateral diffraction is used for the power distribution. In this paper, we propose a new design of a low loss star coupler which employs UV-written tapered waveguides and an AWG based on the low loss star couplers, and investigate their various characteristics. The loss of the UV-written star coupler is lower than that of the conventional star coupler, and the AWG device based on the UV-written star couplers shows low loss characteristics.

• Korean Journal of Optics and Photonics
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• v.11 no.6
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• pp.418-422
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• 2000

In this paper, we have modeled and fabricated a mutimode interference (MMI) $1\times4$ optical power splitter using finite-difference beam propagation method and $Ag^+-Na^+$ ion-exchanged method in BK7 glass. The power splitting ratio of the fabricated MMI $1\times4$ optical power splitter shows 0.46 dB..46 dB.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.3
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• pp.59-69
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• 2000

Three-dimensional total station system which integrated the instrument with Target Pin and TEMS 3D software developed by SKEC R&D center was applied to a tunnel excavation for monitoring of convergence and crown settlement. The efficiency of the system was proved as the result in the aspects of exact monitoring and prediction of rock conditions ahead of the face. To monitor the behavior of tunnel lining at the maintenance stage, DOCS system was applied to the subway tunnel section. Such many effects as the vibration of sensors, verification of the system efficiency, the effect of test trains operation, the variation of temperature and the effect of high voltage was checked. Thus the management scheme for tunnel maintenance was laid out as a proposal.

• Proceedings of the Optical Society of Korea Conference
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• 1997.08a
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• pp.47-47
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• 1997