• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.95-101
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• 2015

To accurately extract absolute distance information from a self-mixing interferometry (SMI) signal, in this paper we propose an approach based on a particle swarm optimization (PSO) algorithm instead of frequency estimation for absolute distance. The algorithm is utilized to search for the global minimum of the fitness function that is established from the self-mixing signal to find out the actual distance. A resolution superior to $25{\mu}m$ in the range from 3 to 20 cm is obtained by experimental measurement, and the results demonstrate the superiority of the proposed approach in comparison with interpolated FFT. The influence of different external feedback strength parameters and different inertia weights in the algorithm is discussed as well.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.569-572
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• 2005

Technological feasibility of using recently-available femtosecond ultra short pulse lasers for advanced precision length metrology is investigated with emphasis on absolute distance measurements with $10{\mu}m$ ??resolution over extensive ranges. The idea of using femtosecond lasers for the measurement of absolute distances is based on the fact that a short pulse train is a mode-locked combination of discrete monochromatic light components spanning a wide spectral bandwidth. The synthetic wavelength is created from the repetition frequency, $f_r$ of the femtosecond laser and for more precise resolution, higher-order harmonics of the repetition frequency may be selected as the synthetic wavelength by using appropriate electronic filters.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.39-40
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• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.589-590
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• 2010

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.91-96
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• 2006

We use near-infrared observations of eight selected Galactic globular clusters to estimate their distances by comparing the observed and theoretically predicted K magnitudes of the red giant branch bumps and tips. The K magnitude levels of the RGB bump and tip have been measured from the luminosity function of the selected RGB stars in the clusters. Theoretical absolute $M_k$ magnitudes of the RGB bump and tip are taken from the Yonsei-Yale isochrones. Comparing the observed apparent K magnitude with the derived absolute $M_k$ magnitude, we calculate the distance moduli of the clusters. We discuss the dependency of the derived distance modulus on the cluster age and the uncertainty of the distance measurement from the near-infrared photometry of the RGB bump and tip.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.839-840
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• 2011

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.651-653
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• 2000

In this study, a distance-measurement system was proposed by using principle of the Michelson Interferometer and a fundamental research was carried out. In case of the rnichelson interferometer, relativity distance was measured by relativity-difference of two course of light. But wavelength of light source were changed in this system in order to use interference phenomenon of michelson interferometer in measuring absolutely distance. Wavelength of input signal were changed periodically and were interfered electrically. So absolute distance can be calculated by using $\Delta\lambda$ and measuring $\eta\Delta$ in electric interference. Nose by a external factor was small in this system because a absolutely distance was measured by phase difference. And a dispersion of noise was small in pulse-echo response because a error was occurred in range of phase difference of signal. Also very wide range can be measured by only single system because informations of distance were acquisited in wavelength level.

• Journal of KIISE:Software and Applications
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• v.29 no.9
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• pp.631-644
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• 2002

In this paper efficient algorithms for content-based video retrieval using motion information are proposed, including temporal scale-invariant retrieval and temporal scale-absolute retrieval. In temporal scale-invariant video retrieval, the distance transformation is performed on each trail image in database. Then, from a given que교 trail the pixel values along the query trail are added in each distance image to compute the average distance between the trails of query image and database image, since the intensity of each pixel in distance image represents the distance from that pixel to the nearest edge pixel. For temporal scale-absolute retrieval, a new coding scheme referred to as Motion Retrieval Code is proposed. This code is designed to represent object motions in the human visual sense so that the retrieval performance can be improved. The proposed coding scheme can also achieve a fast matching, since the similarity between two motion vectors can be computed by simple bit operations. The efficiencies of the proposed methods are shown by experimental results.

• International Journal of Control, Automation, and Systems
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• v.6 no.6
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• pp.800-808
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• 2008

A fingerprint verification system based on a set of invariant moment features and a nonlinear Back Propagation Neural Network(BPNN) verifier is proposed. An image-based method with invariant moment features for fingerprint verification is used to overcome the demerits of traditional minutiae-based methods and other image-based methods. The proposed system contains two stages: an off-line stage for template processing and an on-line stage for testing with input fingerprints. The system preprocesses fingerprints and reliably detects a unique reference point to determine a Region-of-Interest(ROI). A total of four sets of seven invariant moment features are extracted from four partitioned sub-images of an ROI. Matching between the feature vectors of a test fingerprint and those of a template fingerprint in the database is evaluated by a nonlinear BPNN and its performance is compared with other methods in terms of absolute distance as a similarity measure. The experimental results show that the proposed method with BPNN matching has a higher matching accuracy, while the method with absolute distance has a faster matching speed. Comparison results with other famous methods also show that the proposed method outperforms them in verification accuracy.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.4
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• pp.22-26
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• 2007

We describe a new way of implementing absolute displacement measurements by exploiting the optical comb of a femtosecond pulse laser as a wavelength ruler, The optical comb is stabilized by locking both the repetition rate and the carrier offset frequency to an Rb clock of frequency standard. Multiwavelength interferometry is then performed using the quasi-monochromatic beams of well-defined generated wavelengths by tuning an external cavity laser diode consecutively to preselected light modes of the optical comb. This scheme of wavelength synthesizing allows the measurement of absolute distances with a high precision that is traceable to the definition of time. The achievable wavelength uncertainty is $1.9{\times}10^{-10}$, which allows the absolute heights of gauge blocks to be determined with an overall calibration uncertainty of 15 nm (k = 1). These results demonstrate a successful industrial application of an optical frequency synthesis employing a femtosecond laser, a technique that offers many possibilities for performing precision length metrology that is traceable to the well-defined international definition of time.