• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.1076-1085
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• 2009

In this paper, a new method for efficient computation of CGH patterns for 3-D video images is proposed by combined use of temporal redundancy and look-up table techniques. In the conventional N-LT method, fringe patterns for other object points on that image plane can be obtained by simply shifting these pre-calculated PFP (Principle Fringe Patterns). But there have been many practical limitations in real-time generation of 3-D video holograms because the computation time required for the generation of 3-D video holograms must be massively increased compared to that of the static holograms. On the other hand, as ordinary 3-D moving pictures have numerous similarities between video frames, called by temporal redundancy, and this redundancy is used to compress the video image. Therefore, in this paper, we proposed the efficient hologram generation method using the temporal redundancy of 3-D video image and N-LT method. To confirm the feasibility of the proposed method, some experiments with test 3-D videos are carried out, and the results are comparatively discussed with the conventional methods in terms of the number of object points and computation time.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.3
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• pp.213-220
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• 2000

The method of photoelasticity allows one to obtain principal stress differences and principal stress directions in a photoelastic model. In the classical approach, the photoelastic parameters are measured manually point by point. The previous methods require much time and skill in the identification and measurement of photoelastic data. Fringe phase shifting method has been recently developed and widely used to measure and analyze fringe data in photo-mechanics. This paper presents the test results of photoelastic fringe phase shifting technique for the stress analysis of a circular disk under compression and an edge-cracked plate subjected to tensile load. The technique used here requires four phase stepped photoelastic images obtained from a circular polariscope by rotating the analyzer at $0^{\circ}$, $45^{\circ}$, $90^{\circ}$ and $135^{\circ}$. Experimental results are compared with those or FEM. Good agreement between the results can be observed. However, some error may be included if the technique is used to general direction which is not parallel to isoclinic fringe.

• Journal of The Korean Astronomical Society
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• v.52 no.2
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• pp.49-55
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• 2019

The New Vacuum Solar Telescope (NVST) is the largest solar telescope in China. When using CCDs for imaging, equal-thickness fringes caused by thin-film interference can occur. Such fringes reduce the quality of NVST data but cannot be removed using standard flat fielding. In this paper, a correction method based on multi-scale decomposition and adaptive partitioning is proposed. The original image is decomposed into several sub-scales by multi-scale decomposition. The region containing fringes is found and divided by an adaptive partitioning method. The interference fringes are then filtered by a frequency-domain Gaussian filter on every partitioned image. Our analysis shows that this method can effectively remove the interference fringes from a solar image while preserving useful information.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2535-2540
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• 2002

ESPI is a noncontact, nondestructive and relatively fast inspection method. For these reasons ESPI is being applied as a valuable tool in the nondestructive evaluation of structural components. Phase shifting ESPI is used more effectively than the traditional ESPI because spatial resolution of small object displacements are improved and numerical phase values are obtained for all pixels in the image. Consequently the quantitative measurement of deformation is possible. ESPI fringe patterns are contaminated with high levels of speckle noise. Therefore the phase image is to be smoothed to remove the noise and obtain a better signal-to-noise ratio. In this study, smoothing is done by phase shifting convolution to avoid smoothing errors close to the 2$\pi$ phase ambiguities in the deformation phase image, and median filter is used as a smoothing filter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.92-96
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• 1993

Modern NC machine tools require a more and more exact monitoring and control of cutting process. A very important parameter is tool wear used to optimize cutting data and to change tools at the right time. In this study, a real-time multi-tool fracture method is proposed for measuring crater from fringe patterns generated by uni-shadow-moire. An optical technique using laser for non-contact measurement of tool fracture is presented. The technology in which the tool is illuminated by a beam of He-Ne laser and then the image of tool fracture CCD camera.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.170-175
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• 1999

Noncontact measuring methodology of 3-dimensional profile using CCD camera are very attractive because of it's high measuring speed and its's high sensitivity. Especially, when projecting a grid pattern over the object the captured image have 3 dimensional information of the object. Projection moire extract 3-D information with another grid pattern in front of CCD camera. However phase measuring profilometry(PMP) obtain similar results without additional grid pattern. In this paper, new method for grid pattern generation system by polygonal mirror and Laser Diode. This system is applied the projection moire and the PMP.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.413-414
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• 2006

In this paper, we propose an efficient coding method of digital hologram (or fringe pattern) using multi-view prediction technique based on video and image coding standard such as MPEG. The proposed algorithm illustrates that it has better properties for reconstruction and higher compression rate than the previous researches.

• Journal of the Korean Ceramic Society
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• v.30 no.11
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• pp.919-924
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• 1993

Domain structure and the spatial arrangement of tetragonal and rhombohedral phases in PZT ceramics at MPB composition were investigated with a transmission electron microscope. Fringe Contrast and doublet spot splitting were observed in the image mode and the selected area diffraction pattern, respectively. Besides, triplet spot splitting was also observed in the other part of the specimen. These observations indicate that both the single phase regions and the regions which are comosed of alternatively arranged tetragonal and rhombohedral domains coexist in a PZT ceramics at the MPB composition.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.5 s.305
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• pp.29-40
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• 2005

According as base of digital hologram has been magnified, discussion of compression technology is expected as a international standard which defines the compression technique of 3D image and video has been progressed in form of 3DAV which is a part of MPEG. As we can identify in case of 3DAV, the coding technique has high possibility to be formed into the hybrid type which is a merged, refined, or mixid with the various previous technique. Therefore, we wish to present the relationship between various image/video coding techniques and digital hologram In this paper, we propose an efficient coding method of digital hologram using standard compression tools for video and image. At first, we convert fringe patterns into video data using a principle of CGH(Computer Generated Hologram), and then encode it. In this research, we propose a compression algorithm is made up of various method such as pre-processing for transform, local segmentation with global information of object image, frequency transform for coding, scanning to make fringe to video stream, classification of coefficients, and hybrid video coding. Finally the proposed hybrid compression algorithm is all of these methods. The tool for still image coding is JPEG2000, and the toots for video coding include various international compression algorithm such as MPEG-2, MPEG-4, and H.264 and various lossless compression algorithm. The proposed algorithm illustrated that it have better properties for reconstruction than the previous researches on far greater compression rate above from four times to eight times as much. Therefore we expect that the proposed technique for digital hologram coding is to be a good preceding research.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.310-311
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• 2008

We have studied electro-optical characteristics of fringe-field switching (FFS) mode with high $d{\Delta}n$ according to the electrode position. In this device, the fringe-electric field drives the LCs to rotate so that the dielectric torque is electrode-positional dependent, which results in electrode-position dependency in the LC's rotating angle. We confirmed polarization microscope image and chromaticity diagram at the different electrode position with LC that have high $d{\Delta}n$. Since the FFS mode is influenced by horizontal and vertical electric field, the FFS mode modulates light using both phase retardation and polarization rotation effect, which had already been verified with previous studies. However, from another point of view, tight modulation of FFS mode has been demonstrated by performing experiment and calculated simulation at the high $d{\Delta}n$ LC cell.