• Current Optics and Photonics
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• 제1권6호
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• pp.618-625
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• 2017

In the present research, a new bending system using a segmented vacuum chuck for Stressed Mirror Polishing (SMP) is developed. SMP is a special fabrication method for thin aspheric mirrors, where simple flat or spherical fabrication is applied while a mirror blank is deflected. Since a mirror blank is usually glued to a bending fixture in the conventional SMP process, there are drawbacks such as long curing time, inconvenience of mirror replacement, risk of mirror breakage, and stress concentration near the glued area. To resolve the drawbacks, a new bending system is designed to effectively hold a mirror blank by vacuum. For the developed bending system, the optimal bending load to achieve the designated mirror deflection is found by finite element analysis and an optimization algorithm. With the measurement results of the deflected mirror surfaces with the optimal bending loads, the feasibility of the developed bending system is investigated. As a result, it is shown that the bending system is appropriate for the SMP process.

• 정보저장시스템학회논문집
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• 제8권1호
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• pp.33-38
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• 2012

To investigate of load/unload performance, FE (finite element) model of conventional suspension and HAMR suspension were made. The FE models were verified by modal analysis. In the loading simulation, the conventional system could stably load onto the disk without contact. On the other hand, the HAMR suspension which had an optical fiber and prism occurred slider - disk contact. In the unloading process, the conventional system was unloaded without contact. However, in the HAMR suspension, the contact between slider and disk was occurred at the moment that the dimple was separated during unload process. Therefore the load/unload performance of HAMR decrease with high stiffness, it is necessary that stiffness of HAMR suspension should reduced with design parameters of optical fiber and prism.

• 한국소음진동공학회논문집
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• 제15권2호
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• pp.156-160
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• 2005

We design a new actuator of 3-axis motion for high performance optical devices. The actuator makes it possible to control the tilting motion by using moving magnet and PCB-coil, which have benefits in price and manufacturing. To predict the characteristics of the actuator, especially the effect of moving magnet, finite element method and electro-magnetic analysis were used. By comparing simulation data with experimental results, we verified the accuracy of the simulation and the superiority of the present.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.792-798
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• 2012

This study shows the vibration characteristics of an actuator with six wire-suspensions, used in optical pickups of optical disc drives (ODDs). In this paper, the vibration characteristics of this beam structure is induced mathematically. To obtain vibration modes of focusing direction, the vibration analysis is achieved in lateral and longitudinal directions of the structure. The accuracy of induced vibration characteristics is proved by comparing mode frequencies with a finite element analysis. Finally, it is shown that mode shapes can be modified by changing design parameters in mathematical expressions.

• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1128-1136
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• 2012

This paper analyzes the vibration characteristics of an optical pickup actuator, which has six wire-suspensions and is used in optical disc drives(ODDs). The vibration characteristics of the actuator is mathematically described by analyzing its beam configuration and motion condition confined to lateral and longitudinal directions of the beams. The accuracy of the vibration characteristics is proved by comparing mode frequencies with a finite element analysis. Finally, it is shown that mode frequencies and shapes can be modified by changing design parameters in mathematical expressions.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.59-63
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• 2005

Nowadays, various approaches are performed to increase the storage capacity of optical storage device. One of the promising candidates is using the high NA lens. By using high NA lens, the beam spot size can be reduced which will lead to increase the storage density. This paper proposes a double cantilever beam type bimorph PZT actuator for fine motion that can control the gap between the flexible media and optical pickup which uses high NA lens. Mathematical model is derived by using Hamilton's principle and the model is verified by finite element analysis and experiment. Position controller is designed and its performance is evaluated by experiment.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 사면안정 학술발표회
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• pp.223-232
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• 2000

Optical fibre sensors have shown a potential to serve real time health monitoring of the structures. They can be easily embedded or attached to the structures and are not affected by the electro-magnetic field. Furthermore, they have the flexibility of the sensor size and very highly sensitive. In this study, we conducted several laboratory and field tests using a novel optical sensor based on Brillouin scattering. One of the advantages of this technique is that the bare fibre itself acts as sensing element without any special fibre processing or preparation. Test results have shown that BOTDR can be a great solution for sensor systems of Civil Engineering Smart Structures.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.575-585
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• 2015

Magnetic field in magnetic bearings is the physical medium to realize magnetic levitation, the distribution of the magnetic field determines the operating performance of magnetic bearings. In this paper, a thin-slice Fiber Bragg Grating-Giant Magnetostrictive Material magnetic sensor used for the air gap of magnetic bearings was proposed and tested in the condition of dynamic magnetic field. The static property of the sensor was calibrated and a polynomial curve was fitted to describe the performance of the sensor. Measurement of dynamic magnetic field with different frequencies in magnetic bearings was implemented. Comparing with the finite element simulations, the results showed the DC component of the magnetic field was detected by the sensor and error was less than 5.87%.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.453-458
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• 2014

A novel high birefringent polymer terahertz (THz) fiber with a suspended elliptical core is proposed in this paper. The introduction of an elliptical core can enhance asymmetry to realize high mode birefringence, and a large porous outer cladding effectively isolates the core-guided mode from interacting with the surrounding environment. A full-vector finite element method(FEM) is used to analyze the characteristics of the THz fiber. Simulation results show that the suspended elliptical fiber exhibits high mode birefringence on a level of $10^{-2}$ over a wide frequency range, and an extremely large mode birefringence(${\approx}0.06226$) is obtained when ellipticity is 0.2. Moreover, a suspended hollow elliptical core fiber is also discussed for the purpose of lower loss, however high mode birefringence and low relative absorption loss can not coexist in such a kind of fiber.

• 한국광학회지
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• 제16권2호
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• pp.128-132
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• 2005

주기적인 홀로그램을 제작하기 위한 일반적인 CGH(computer generated hologram)의 설계 프로그램은 회절각 공간에서 설정한 모델 방정식을 사용하고 있다. 따라서 비교적 큰 회절각을 사용하는 경우 평면에서 관찰되는 이미지는 설계와 큰 차이가 생기게 된다. 이를 보정하기 위하여 이러한 오차의 발생원인을 회절이론 분석을 통하여 모델 방정식을 만들었으며 이를 실험을 통하여 검증하였다. 또한 회절각 기반의 기존 프로그램을 교정하지 않으면서 이러한 오차를 보정하기 위한 설계 방법을 제시한다.