• International Journal of Precision Engineering and Manufacturing
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• 제9권3호
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• pp.46-50
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• 2008

The present status and future prospects of the levitation mass method (LMM), a technique for precision mass and force measurement, are reviewed. In the LMM, the inertial force of a mass levitated using a pneumatic linear bearing is used as the reference force applied to the objects being tested, such as force transducers, materials, or structures. The inertial force of the levitated mass is measured using an optical interferometer. We have modified this technique for dynamic force calibration of impact, oscillation, and step loads. We have also applied the LMM to material testing, providing methods for evaluating material viscoelasticity under an oscillating or impact load, evaluating material friction, evaluating the biomechanics of a human hand, and generating and measuring micro-Newton-level forces.

• Journal of the Optical Society of Korea
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• 제6권1호
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• pp.5-12
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• 2002

A novel interrogation scheme to detect fine Bragg wavelength shift using a long period fiber grating pair with erbium-doped fiber inserted between the two gratings is reported. The technique is shown to feature high resolution and much more immunity to temperature perturbation compared to the conventioned Mach-Zehnder interferometer demodulation system. For quasi-static strain measurement, this approach provides high wavelength resolution of 0.05 pm that corresponds to 41.7 ne in strain and $3.8 $\times$ 10^{-3}$$^{\circ}C$ in temperature. This interrogation system is also employed in dynamic measurement to obtain the minimum detectable strain perturbation of ~ 8.76 ne/H $z^{{\frac}{1}{2}}$ at 100 Hz. Moreover, this interrogation system has prominent thermal stability. This thermal stability comes from the fact that two arms of the interferometer, the core and cladding in erbium-doped fiber, are exposed to nearly the same environment .

• 한국광학회지
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• 제5권2호
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• pp.198-203
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• 1994

구면의 긴 곡률반경을 측정하기 위하여 양방향 층밀리기 간섭계를 이용하는 새로운 방법을 제시하였다. 시준장치의 광원을 미세이동시켜 출사광선의 곡률중심과 시험구면의 초점을 일치시키는 비시준 조명방법을 사용하였으며 양방향 층밀리기 간섭계를 사용하여 시험구면에서 출사한 광선의 시준 여부를 정확히 확인하였다. 이 방법은 렌즈의 긴 초점길이도 측정할 수 있으며 여러가지 변수에 의한 측정정확도를 자세히 분석하였다.

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 하계학술발표회 논문집
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• pp.111-112
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• 2007

The spatial coherence function of laser beam was measured by using a Sagnac interferometer and self referencing technique. For laser beam passing through a narrow slit, absolute value of measured spatial coherence function becomes more symmetric as the slit size is reduced. For diverging beams, the spatial coherence function shows fast oscillations in its real and imaginary parts. We explain this by using a Gaussian Schell-model. One can use this measurement method to study and characterize the property of light field coming out of small sample.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.2-3
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• 2005

Air gap control method using a conventional actuator for near field recording technology has been reported. To achieve good performance in the air gap servo and further experiments, the assembling between OL and SIL is the critical procedure. A lens set with NA 1.45 at 405 m has been assembled and tested by using a Twyman-Green interferometer. The tolerance of assembling is very tight and the designing and adjusting procedure must be carefully controlled.

• Journal of the Optical Society of Korea
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• 제3권2호
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• pp.64-68
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• 1999

The performance of a fiber Bragg grating strain sensor constructed with 3$\times$3 coupler is investigated. A 3$\times$3 coupler Mach-Zehnder (M/Z) interferometer is used as wavelength discriminator, interrogating strain-induced Bragg wavelength shifts. Two quadrature-phase-shifted intensities are synthesized from the as-coupled interferometer outputs, and digital arctangent demodulation and phase unwrapping algorithm are applied to extract the phase information proportional to strain. Due to the linear relation between the input strain and the output of quadrature signal processing, signal-fading problems eliminated. In the experiment, a fiber grating that was surface adhered on an aluminum beam was strained in different ways, and the photodetector signals were transferred and processed in a computer-controlled processing unit. A phase recovery fo 7.8$\pi$ pk-pk excursion, which corresponds to ~650$\mu$strain pk-pk of applied strain, was demonstrated. The sensor system was stable over the environmental intensi쇼 perturbations because of the self-referencing effect in the demodulation process.

• Journal of the Optical Society of Korea
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• 제3권1호
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• pp.1-9
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• 1999

We have studied the sensitivity of four different phase shift measurement schemes with a Mach-Zehnder interferometer. The input light is considered to be in a coherent state and the detectors are assumed to be ideal with the quantum efficiency of unity. It is shown by direct calculation of the operators corresponding to the measurement schemes that the uncertainty of the phase-shift measurement is limited to the classical one $\frac{1}{\sqrt{m}}$(m is the average number of the photons in the input state) regardless of the phase-shift measurement schemes.

• Journal of the Optical Society of Korea
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• 제3권1호
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• pp.32-34
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• 1999

We successfully demonstrated a stabilized fiber-optic Mach­Zehnder interferometer filter with continuous tunability. The tunable scheme was achieved with fine wavelength control of an 1.3${\mu}{\textrm}{m}$ tunable laser diode used as a stabilization light source. The transmission wavelength of the tunable filter was shifted linearly with respect to the wavelength change of the stabilization light source.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.919-922
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• 2000

A robust optical security technique using ortho-gonally polarized lights in the interferometer is proposed. We use orthogonally polarized lights in order to minimize the noise generated by the refractive index change due to vibration, flow of air, change of temperature etc. To make orthogonally polarized lights the first beam splitter in the Mach-Zehnder interferometer is substituted by a polarizing beam splitter(PBS). Because of incoherence of orthogonally polarized lights, the noise generated by the change of refractive index is minimized. To encrypt an image we use the random partition and the diffusing of pixel. Finally we make Phase-only-filters of each image which is randomly partitioned and diffused pixel by pixel. Simulation results show the proposed system has the ability of encryption and decryption of an image.

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 하계학술발표회 논문집
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• pp.187-189
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• 2008

The spatial coherence function of multy-mode beam was measured by using a Sagnac interferometer and self referencing technique. For leaner polarization laser beam passing through a multy-mode fiber, its change value of spatial mode and polarization from stress of faber and input coupling angle. And each spatial mode have each polarizations, when we simulation Wigner distribution function and Spatial Correlation function of spatial multi-mode beam by using Hermit Gaussian modes leaner sum. We measured spatial coherence function of using by multy-mode fiber. One can use this measurement method to study and characterize the property of multy-mode light field coming out of GRIN multy-mode fiber.