• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.307-308
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• 2007

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.03a
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• pp.85-90
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• 1996

In the word, there is varied types of vibration, and these affect the mechanical industry. In this paper is plates with two parallel sides fixed. Electronic speckle pattern interferometry (ESPI) is one of the optical nondestructive testing technique. By using the ESPI, vibration modes for excitation point, a/b(ratio of longuitudinal and lateral length), and kind of specimen are measured and compared qualitatively with theoritical analysis that Warburton proposed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.239-244
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• 1998

ESP(Electronic Speckle Pattern Interferometry) is an optical technique to measure deforamtion of engineering components and materials in industrial areas. ESPI, a non-contact and non-destructive measuring method, is capable of providing full-field results with high spatial resolution and high speed. One of important application aspects using electronic speckle pattern interferometry is to generate contours of a diffuse object in order to provide data for 3-D shape analysis and topography measurement. The electronic speckle contouring is suitable for providing measurement range from millimeters to several centimeters. In this study, we introduce the contouring method by modified dual-beam speckle pattern interferometer and a shift of the two illumination beams through optical fiber in order to obtain the contour fringe patterns. Before the experiments, we performed the geometric analysis for dual-beam-shifted ESPI contouring. And by this geometric analysis, we performed the electronic speckle contouring experiment. We used 4-frame phase shifting method with PZT for quantitative analysis of contour fringes. Finally, we showed good agreements between the geometric analysis and experimental results.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.1
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• pp.33-42
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• 1996

The high coherence of laser beam has made it possible to observe interference effects even in the light scattered from rough surfaces. That's why, when object with a scattering surface is illuminated with laser light, we do see a speckled appearance due to random interference. This sort of unique property of laser speckle has bruht into existence the new noncontaciting techniques such as speckle metrology method of measuring deformation, displacement, and vibration etc of objects with high optical sensitivity. The measurable range of speckle metrology especially used to measure in -plane information, however, is limited by some factors, the so-called strain, rotation tilt of surface and out of displacement perpendicular to the plane of analysis This restrictions severly limits the measurable range of speckle metrology by causing the decorrelation of speckle patterns. It is the purpose of this paper to give a survey on the measurable limitation of speckle photography method that is one of speckle metrology. Namely we will discuss the mutual relationships and problems of each limitations adding the restriction on the largest and smallest displacement measurable with speckle methods.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.4
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• pp.40-46
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• 2003

In this research, we accomplished the interpreting about the vibration of the object, which is the out of plane displacement in the Electronic Speckle Pattern Interferometry(ESPI), one of the optical measuring technique. The vibrating object has a inherent nodal line, therefore we can get the information about the vibration of the object by interpreting it. we used a speaker and a cantilever plate for a measurement object, and interpreted it qualitatively by using the Time-Average ESPI. In this experimental result, the speaker has the lower mode of fringe at 550Hz, 570mV, and the higher mode of fringe at 950Hz, 570mV This ESPI is a non-destructive test, and because of using the laser at measuring, it has a high resolution. The ESPI can test vibration mode regardless of the test object size, because the area which illuminated laser is the test area.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.217-224
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• 2002

It is very important to measure and visualize the changes in the physical properties of fluid flow because this is the foundation of measurement techniques used in aerodynamics, heat transfer, plasma diagnostics, and stress analysis of transparent models. The optical methods are advantageous over probe-based techniques in the optical methods are of high speed, non-contact and are capable of providing full-field results with high spatial resolution. Therefore we propose the electronic speckle pattern interferometry(ESPI) that gives us a solution to overcome those limitations. In this paper the experimental results show qualitative and quantitative visualization of changes in the physical properties of the candle and alcohol lamp with 3D plotting. And we obtained the refractive index, mass density and temperature distribution of fluids. The results clearly show the process of flow phenomena and give the feasibility of quantitative interpretation of gasdynamics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.556-560
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• 2005

The measurement method by Laser Speckle Interferometry which uses the interference law which will grow precedes and with it explains a resolution measurement ability and together the change of place arrowhead and general measurement, at real-time measurement sensitivity it has application boat song from candle precise measurement field it is increasing. But, currently the domestic application technique to sleeps and optical science military merit by optical science interferometer and directness it composes purchases to the level which it applies the expensive commercial business equipment the outside and in spite of the technical ripple effect is deficient even in many strong point. The hazard which complements like this problem point form technical development it leads from the research which it sees and an application degree and to sleep as the measurement equipment which tries to develop the small-sized optical science interference sensor and an interpretation program it raises it does.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.101-108
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• 2008

Residual stress is one of the causes which make defects in engineering components and materials. Many methods have been developing to measure the residual stress. Though these methods provide the information of the residual stress, they also have disadvantage like a little damage, time consumption, etc. In this paper, we devised a new experimental technique to measure residual stress in materials with a combination of laser speckle pattern interferometry and spot heating. The speckle pattern interferometer measures in-plane deformation during the heat provides for much localized stress relief. 3-D shape is used for determining heat temperature and other parameters. The residual stresses are determined by the amount of strain that is measured subsequent to the heat and cool-down of the region being interrogated. A simple model is presented to provide a description of the method. In this paper, we could experimentally confirm that residual stress can be measured by using laser interferometry and spot heating method.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.53-58
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• 1999

Even I the Electronic Speckle Pattern Interferometry(ESPI) method that measure the strain of object within wavelength of light is less visibility than Holographic Interferometry(HI) method, the merits of application, convenience and time-save have made the method practical in industry. However, the existing ESPI methods that are based on dual-exposure, real-time and time-average method have difficulties for accurate measurement, due to irregular intensity and shake of phase. Recently, in order to solve this problem, phase shifting method have been proposed. In this method, the path of reference light in interference is shifted to make improvement in distinction and precision. But this method includes too many noise, caused by the problem of relationship between object and phase. Therefore, a method to reduce noise muse be introduced. In this paper, least square fitting method is proposed. As results, the phase-map is influenced by precise phase shifting and current of notes and speckle pattern obtained by phase shifting method is improved on the existing method driven from time-average method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.91-95
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• 1997

ESPI(Electronic Speckle Pattern Interferometry) is new optical measuring method to be able to measure the surface deformations of engineering components and materials in industrial areas. Conventional measuring method of surface deformation such as the strain gauge have many demerits because it is contact and point-to-point measuring one. But ESPI that is non-contact, whole field measuring method can overcome previous disadvantages. The speckle pattern to be formed with interference phenomena of scattering light from rough surfaces illuminated by laser light have phase information of surface In this study we used this interference phenomena and the phase shifting method to measure the in- plane deformation, together with the use of digital equipment to process the information contained in the speckle pattern and to display consequent inter ferograms. Finally we obtained good agreement between the experimenta results and those of FEM..