• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.25-31
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• 1999

A real-time holography system using LCD with CCD camera is proposed. In this system, the rainbow hologram is used since it can be reconstructed by white light source. And to record on CCD camera, a kind of in-line holography method is used to widen the width of the fringe pattern. The interference fringe pattern by proposed system is detected with CCD camera and transferred to the LCD. A 3-dimensional image is reconstructed when the white light source illuminates the LCD. If the position of the input image is changed, that of the reconstructed image is also changed. So it can represent 3-dimensional moving images at real-time. In this paper, to confirm the usefulness of the proposed method, the reconstructed image by holographic film is compared to the same reconstructed image by LCD. In the recording process, the optimal ratio of the reference and object beam intensity is also investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1208-1217
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• 1993

The simple and effective optical technique synthesizing holographic interferometry and speckle photography is presented. The optical system used in this experiment is based on image holography. A cantilever beam located on the precision translator is used to evaluate this measurement system. Experimental results agree well with the actual displacements within the error of 2.8%. As an its application, three dimensional contact deformation in the ball indentation is measured by using this optical system and compared with the numerical analysis by finite element method.

• The korean journal of orthodontics
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• v.24 no.2
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• pp.447-476
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• 1994

This study was performed to evaluate the initial reaction of maxillofacial complex to the Class II intermaxillary and the anterior vertical elastic forces on the six types of archwires including multiloop edgewise arch wires(MEAW). A human dry skull was used for this purpose and this investigation was done by holographic interferometry. Based on such investigation, the fringe pattern and the number of fringes of each condition were compared and analyzed. The findings of this study were as follows: 1. As the orthodontic forces increased, the amount of displacement increased. 2. As the orthodontic forces were applied, the fringes were shown not only in the teeth and the maxilla but also in the adjacent bones, i.e., temporal bone, zygomatic bone, nasal bone, frontal bone and sphenoid bone. And the direction of fringe pattern and the number of fringes were different from each other by the sutures. 3. As the long Class II elastic forces were applied, the backward-downward displacements of the anterior teeth and the maxilla were shown, and backward displacement of the former were grater than those of the latter. And backward displacements were greater by the long Class II elastic forces than by the short Class II elastic forces. 4. As the anterior vertical elastic forces were applied, downward displacements of the anterior teeth and the maxilla were shown, and the downward displacements of the former were greater than those of the latter relatively. 5. The downward displacements of the anterior area to the anterior vertical elastic forces of the MEAW were greater than those of other archwires. In addition, the more tip-back bend was applied, the more displacement was seen. 6. As the Class II intermaxillary forces and the enough anterior vertical elastic forces were applied on the MEAW with tip-back bend, there was an intrusive effect of the posterior teeth.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.3
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• pp.188-194
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• 2016

We propose an acousto-optic technique for the nondestructive evaluation of adhesion properties of a Pt/Ti thin-film interface. Since there are some problems encountered when using prevailing techniques to nondestructively evaluate the interfacial properties of micro/nano-scale thin-films, we applied an interferometer that combined the acoustic and optical methods. This technique is based on the Michelson interferometer but the resultant surface of the thin film specimen makes interference instead of the mirror when the interface is excited from the acoustic transducer at the driving frequency. The thin film shows resonance-like behavior at a certain frequency range, resulting in a low-contrast fringe pattern. Therefore, we represented quantitatively the change in fringe pattern as a frequency spectrum and discovered the possibility that the interfacial adhesion properties of a thin film can be evaluated using the newly proposed technique.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.80-86
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• 2005

Optical performance evaluation results and an interference fringe pattern analysis of alignment errors for an optical head of a near-field receding (NFR) system are presented. The focusing unit is an optical head of a NFR system and is composed of a solid immersion lens (SIL) and an objective lens (OL). Generally, the size of the focusing unit is smaller than that of the conventional optical recording head. Hence there are difficulties to assemble the small focusing unit precisely. We composed an evaluation system with an interferometer and evaluated some focusing unit samples aligned and assembled by manual and present the obtained results. Using the conventional optical tool, Code V, a tolerance analysis of the alignment error between the SIL and the objective lens and an interference pattern analysis for the assembly error are executed. Then, through an analysis of the simulation results, the conceptual auto-alignment methodology using a neural network approach is considered.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.330-333
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• 2002

This study Presents improvement of Precision in the non-contacted laser application measuring techniques. The phase map of deformation obtained by phase shifting method in Electronic Speckle Pattern Interferometry displays the wrapped image by the arctangent function, which is a characteristic of 4-step phase shifting method. To obtain deformation distribution from the results, the wrapped phase map is processed by an unwrapping method. But a previous method cannot apply discontinuous object as like plate with a circular hole to obtain precious deformation distribution To solve this problem, new algorithm is developed and the result is compared with previous method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.271-274
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• 2002

The 3-D measurement using interference pattern projection is very attractive because of its high measuring speed and high sensitivity. When a sinusoidal amplitude grating was projected on an object, the surface-height distribution of the object is translated into a phase distribution of the deformed grating image. The patters was generated by a interferometer, and a PZT was used to shift the fringes on the target surface. The phase-acquisition algorithms are so sufficiently simple that high-resolution phase maps using a CCD camera can be generated in a short time. A working system requires a interferometer, a PZT, and a detector array interfaced to a microcomputer. Results of measurements on the diffused test objects are described.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.3
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• pp.187-192
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• 2002

In-plane ESPI(Electronic Speckle Patten Interferometry)was devised to measure in~plane defamation and rotation of a specimen with laser in this study. The conventional measuring methods of surface deformations such as the strain gauge have many demerits because they are contact and point-to-point measuring ones. But that ESPI is noncontact, nondestructive and whole field measuring method can overcome previous disadvantages. We used ESPI which is sensitive to in-plane displacement for measuring in-plane deformations of a disk. First of all, the system calibration was done due to an in-plane rotation before getting deformations of a disk. Finally we showed good agreement between theexperiment results and those of the FEA(Finit Element Analysis).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.140-143
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• 2001

Digital shearography, a speckle pattern method is based on the superposition of two laterally sheared images. Therefore, object points which are positioned in some distance from each other are superposed in the image plane. This shearography, one of NDT methods without contact, is able to inspect defects in pipelines and pressure vessels that are used in nuclear power plants. This is can inspect whole fields and has a low sensitivity to environmental noise. Because optical setting is very simple, it has a little exhaustion of time, cost and man power. And also it can find a defect position through real time monitoring of a part. This paper, finds out the relationship among shearing quantity image quality and defect size with this method.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.682-687
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• 2003

The variations of temperature and velocity fields in a Hele-Shaw convection cell (HSC) were investigated using a holographic interferometry and 2-D PIV system with varying Rayleigh number. To measure quasisteady changes of temperature field, two different measurement methods of holographic interferometry; double-exposure method and real-time method, were employed. In the double-exposure method, unwanted waves can be eliminated effectively using digital image processing technique and the reconstruction images are clear, but transient flow structure cannot be reconstructed clearly. On the other hand, transient convective flow can be reconstructed well using the real-time method. However, the fringe patterns reconstructed by the real-time method contain more noises, compared with the double-exposure method. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow structure at high Rayleigh numbers. The periodic flow pattern at high Rayleigh numbers obtained by the real-time holographic interferometer method is in a good agreement with the PIV results.