• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.14-21
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• 2006

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1356-1360
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• 2001

A number of calibration methods are described in ISO 16063 (revision of ISO 5347) and they may be used for special purposes. However, the use of a laser interferometer is recommended for primary calibration. This paper introduces the primary vibration calibration by measuring displacement amplitude and frequency using laser interferometry.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.102-110
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• 2006

We discuss two possibilities of using femtosecond pulse lasers as a new interferometric light source for enhanced precision surface-profile metrology. First, a train of ultra-fast laser pulses yields repeated low temporal coherence, which allows unequal-path scanning interferometry, which is not feasible with white light. Second, the high spatial coherence of femtosecond pulse lasers enables large-sized optics to be tested in nonsymmetric configurations with relatively small-sized reference surfaces. These two advantages are verified experimentally using Fizeau and Twyman-Green type scanning interferometers.

• Current Optics and Photonics
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• v.7 no.4
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• pp.387-397
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• 2023

Tooth surface shape error is an important parameter in gear accuracy evaluation. When tooth surface shape error is measured by laser interferometry, the gear interferogram is highly distorted and the gray level distribution is not uniform. Therefore, it is important for gear interferometry to extract the foreground region from the gear interference fringe image directly and accurately. This paper presents an approach for foreground extraction in gear interference images by leveraging the sinusoidal variation characteristics shown by the interference fringes. A gray level mask with an adaptive threshold is established to capture the relevant features, while a local variance evaluation function is employed to analyze the fluctuation state of the interference image and derive a repair mask. By combining these masks, the foreground region is directly extracted. Comparative evaluations using qualitative and quantitative assessment methods are performed to compare the proposed algorithm with both reference results and traditional approaches. The experimental findings reveal a remarkable degree of matching between the algorithm and the reference results. As a result, this method shows great potential for widespread application in the foreground extraction of gear interference images.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.85-89
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• 2002

This paper used the Laser Speckle Interferometry to present the strain analysis of Nd:YAG Laser welding zone. Previous TIG welding to sheet plate, which welds only high-skilled engineer, produces residual stress nearby welding zone due to thermal effect. However, Laser welding makes sheet pate welding easy and thermal effect minimum. Thermal effect zone is measured by strain analysis of the laser-welding zone by ESPI under tensile testing of sheet plate welded by Nd:YAG laser. The ESPI results, which compared with strain gage method, are agreed within error 3 %.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.260-263
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• 2003

Lasers are used as the source of the interferometers in the industrial field. These lasers need 2 requirements. The first is the narrow linewidth of laser for the long coherence length. The second is the stabilized frequency of laser for the precision measurement. Now HeNe lasers are mostly used and the frequency stability is about 10$^{-9}$ . In this paper, we construct the HeNe laser systems of frequency stabilization using typical 2 method, the beat frequency stabilization method and the intensity difference method. So, we get the frequency stabilities of 2.01$\times$10$^{-9}$ (0.1s), 3.4$\times$10$^{-9}$ (0.1s).

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.349-353
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• 2005

This paper describes the variations of resonance frequencies and vibration mode shapes of laser welded cold rolled carbon steel plate(SCP1) induced by thermal loading during laser welding processing. The characteristics of those are analyzed with stroboscopic ESPI. Electronic speckle pattern interferometry (ESPI) that the electronic processes were added to SPI is one of the very powerful method in the experimental vibration analysis field. Stroboscopic ESPI to make it reliable are compared with theory and experimental method: Finite Element Method(FEM) and Scanning Laser Doppler Vibrometer(SLDV). The results of stroboscopic ESPI are well agreed with SLDV and also the comparison with theory give good agrement within $5\%$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.673-674
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.869-870
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• 2011

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.113-119
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• 1998

Recently Electronic Speckle Pattern Interferometry(ESPI) has been studied because it has the advantages to be able to measure the whole-field surface deformations of engineering components and materials in industrial areas with noncontact. The speckle patterns to be formed with interference phenomena of scattering light from rough surfaces illuminated by laser light have phase informations of surface deformations. In this study we used this interference phenomena and the phase shifting method to measure the inplane deformations, together with the use of digital image equipment to process the informations contained in the speckle pattern and to display consequent interferograms on TV monitor. FEA was performed before experiments and we obtained good agreement between the experimental results and FEA.