• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.264-271
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• 2011

In this paper we examine and compare the computational speeds of three-dimensional (3D) object recognition by use of digital holography based on central unit processing (CPU) and graphic processing unit (GPU) computing. The holographic fringe pattern of a 3D object is obtained using an in-line interferometry setup. The Fourier matched filters are applied to the complex image reconstructed from the holographic fringe pattern using a GPU chip for real-time 3D object recognition. It is shown that the computational speed of the 3D object recognition using GPU computing is significantly faster than that of the CPU computing. To the best of our knowledge, this is the first report on comparisons of the calculation time of the 3D object recognition based on the digital holography with CPU vs GPU computing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.145-149
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• 1997

A laser mesurement system, a modified Michelson interferometer,which can accurately measure high speed length and position of servomechanisms by detecting a phase shift in the measurement beam using an optical interference was developed. A frequency stabilized laser source and a 20 fold frequency interpolation and digitizing circuit were applied to the system. The refractive index of the ambient air was calibrated through the Edlen's formula. The system achieved a resolution of .lambda./40,16nm, a maximum allowable measurement speed of 600 mm/sec, and a length measurement range of 1500mm. Performance of the system was evaluated on the machining center in short and long length measurements

• Journal of the Semiconductor & Display Technology
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• v.2 no.2
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• pp.9-15
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• 2003

This paper proposes a thickness measurement method of silicon-oxide and poly-silicon film deposited on 12" silicon wafer for spin etcher. Halogen lamp is used as a light source for generating a wide-band spectrum, which is guided and focused on the wafer surface through a optical fiber cable. Interference signal from the film is detected by optical sensor to determine the thickness of the film using spectrum analysis and several signal processing techniques including curve-fitting and adaptive filtering. Test wafers with three kinds of priori-known films, polysilicon(300 nm), silicon-oxide(500 nm) and silicon-oxide(600 nm), are measured while the wafer is spinning at 20 Hz and DI water flowing on the wafer surface. From experiment results the algorithm presented in the paper is proved to be effective with accuracy of maximum 0.8% error.rror.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.130-131
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• 2000

One of the more promising proposals for guiding and focusing neutral atoms involves dark hollow laser beams. When the frequency of the laser is detuned to the blue of resonance, the dipole force the atoms feel in the light confines them to the dark core where the atoms can be transported with minimal interaction with the light. The ability of the all-light atom guides to transport large number of ultracold atoms for long distances without physical walls leads to the possibility of a versatile tool for atom lithography, atom interferometry, atomic spectroscopy as well as for transporting and manipulating Bose-Einstein condensates. Furthermore since the atoms transported in all-light atom guides do not come into contact with matter, they can in principle be used to transport antimatter as well. The ability to vary the core size of the hollow beam makes the all-light atom guide potentially useful for focusing neutral atoms. The atoms could be focused as tight as the core size of the hollow beam at its waist. This new focusing scheme, called the atom funnel, would not show spherical and chromatic aberrations that conventional harmonic focusing suffers from. (omitted)

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.24-26
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• 2005

광 간섭계는 광을 이용한 다양한 계측분야에 사용된다. 일반적인 광 간섭계의 지연단은 기계적인 광지연에 의해 저속이며, 시스템 구성상 안정성이 떨어지게 된다. 본 논문에서는 기존의 광간섭계 지연단의 기계적 방식을 배제한 광위상 변조기를 이용한 지연단을 설계하고 그 특성을 분석하였다. 제안된 광 간섭계는 1310nm 10GHz의 반복율을 갖는 광원과 광위상변조기를 이용한 전(全) 광섬유 형태로 안정한 구성을 하였다. 구성된 광간섭계는 광위상 변조기의 변조 전압, 변조 주파수의 변화에 의해 광지연시간의 쉬운 변조가 가능하였으며 최대 20ps 의 광지연시간을 얻을 수 있었다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.515-518
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• 1994

Holographic interferometry is a useful whole-field nondestructive testing for measuring deformations and vibrations of engineering structure. A diverging beam is used as a light source int the most of holographic interferometer practically. For a relatively small object the optical arrangement using a collimated light source has no difficulty in use technically, but for a large object it is difficult to use a collimated beam. In this study we calculate the error of measured displacement from the sensitivity vector dominated by the geometry of optical arrangement for holographic interferometer and show the result obtained with 2-D plots. A Plane surface and a cylindrical surface were chosen as objects to be calculated and computer analysis was carried out for the cases of a diverging beam and a collimated one.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.250-251
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• 2001

There is a considerable interest in the generation of a cold atomic beam having a narrow velocity spread that can be used in various experiments in physics such as ultrahigh resolution atomic and molecular spectroscopy, atom optics, atom interferometry, study of solid surfaces, and low energy collision experiments. The invention of the techniques of laser cooling has stimulated developments in the production of cold and bright atomic beams. (omitted)

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1563-1565
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• 2000

This paper presents the preliminary results on the application of optical fiber sensor(OFS) for the diagnosis of degradation in the transformer oil. An OFS system using a Mach-Zehnder interferometry technique was built to detect attenuation of acoustic signal produced by discharging. With increasing the number of discharging in the insulation oil, the attenuation of acoustic signal became greater. A strong correlation between electrical and acoustic signal intensities from discharge generated in the transformer oil was confirmed by the results reported here.

• Journal of the Optical Society of Korea
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• v.19 no.2
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• pp.165-168
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• 2015

A simple method to determine the focal length of a lens using the Talbot image is presented. This method uses only one grating, requiring neither Moir$\acute{e}$ fringe analysis nor the angle between the gratings. The original Fourier transform was used to access the spectrum beyond the limitation set of the usual fast Fourier transform to determine the (de)magnification accurately enough to be used for the focal length. A set of Talbot images simulated numerically with the Fresnel diffraction integral was used to demonstrate the method. For focal lengths between 5550 mm and 5650 mm, the mean difference between the focal lengths determined from the Talbot images and the true values was 3.3 mm with the standard deviation of the difference being 3.8 mm. The true focal lengths can be recovered with an accuracy of 0.06%.

• Journal of the Optical Society of Korea
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• v.12 no.4
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• pp.281-287
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• 2008

An acousto-optic tunable filter based 3-D micro surface profile measurement using an equally spaced 5 spectral phase shifting is described. The 5-bucket spectral phase shifting method is compared with a Fourier-transform method in the spectral domain. It can provide a fast measurement capability while maintaining high accuracy since it needs only 5 pieces of spectrally phase shifted imaging data and a simple calculation in comparison with the Fourier transform method that requires full wavelength scanning data and relatively complicated computation. The 3-D profile data of micro objects can be obtained in a few seconds with an accuracy of ${\sim}10nm$. The 3-D profile method also has an inherent benefit in terms of being speckle-free in measuring diffuse micro objects by employing an incoherent light source. Those simplicity and practical applicability is expected to have diverse applications in 3-D micro profilometry such as semiconductors and micro-biology.