• ETRI Journal
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• v.40 no.3
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• pp.366-375
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• 2018

Recently, techniques involving head-mounted displays (HMDs) have attracted much attention from academia and industry owing to the increased demand for virtual reality and augmented reality applications. Because HMDs are positioned near to users' eyes, it is important to solve the accommodation-vergence conflict problem to prevent dizziness. Therefore, holography is considered ideal for implementing HMDs. However, within the Nyquist region, the accommodation effect is limited by the space-bandwidth-product of the signal, which is determined by the sampling number of spatial light modulators. In addition, information about the angular spectrum is duplicated over the Fourier domain, and it is necessary to filter out the redundancy. The size of the exit-pupil of the HMD is limited by the Nyquist sampling theory. We newly propose a holographic HMD with an expanded exit-pupil over the Nyquist region by using the time-multiplexing method, and the accommodation effect is enhanced. We realize time-multiplexing by synchronizing a high-speed digital micromirror device and a liquid-crystal shutter array. We also demonstrate the accommodation effect experimentally.

• Journal of Korea Multimedia Society
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• v.12 no.7
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• pp.941-946
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• 2009

As supplying of automatic surveillance or patrol systems based on image processing, the needs on object extraction technology from images increases. The extraction is more difficult when the lighting condition is changed from time to time. There are many approaches to extract objects from images excluding shadow. They have a common problem something like loss of object region according with shadow removal. In this paper a restoration method using color information of objects to complement the problem is presented. The usefulness of the method is verified using images taken from different lighting conditions and selected from well-known DB.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2468-2478
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• 2018

We propose the Sparse Feature Convolutional Neural Network (SFCNN) to reduce the volume of convolutional neural networks (CNNs). Despite the superior classification performance of CNNs, their enormous network volume requires high computational cost and long processing time, making real-time applications such as online-training difficult. We propose an advanced network that reduces the volume of conventional CNNs by producing a region-based sparse feature map. To produce the sparse feature map, two complementary region-based value extraction methods, cluster max extraction and local value extraction, are proposed. Cluster max is selected as the main function based on experimental results. To evaluate SFCNN, we conduct an experiment with two conventional CNNs. The network trains 59 times faster and tests 81 times faster than the VGG network, with a 1.2% loss of accuracy in multi-class classification using the Caltech101 dataset. In vehicle classification using the GTI Vehicle Image Database, the network trains 88 times faster and tests 94 times faster than the conventional CNNs, with a 0.1% loss of accuracy.

• The Journal of the Korea Contents Association
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• v.2 no.2
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• pp.64-72
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• 2002

In this paper, the aims are to develop convenient and safe system-solutions, looking for missing-child, which is one of the increasing social problems, on the basis of World Wide Web. Finger-print cognition has been researching from long time before, as well as Bio-cognition technology, which is adapted for private-cognition in the field of human-cognition. By the fingerprint cognition, which discern finger print, which is generally used in Bio-cognition and is characterized each by using image-processing, missing-child protection system on the basis of Word Wide Web is designed and implemented in this paper. Additionally, indicates plans for revitalization method of this system.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.2
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• pp.133-138
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• 2005

As Aspheric lenses have producted to development for disadvantage of spherical lenses, the purpose of use on aspheric lenses is in improvement of the imaging quality and decrement of the number of lenses used, they are used for lessen the mass and volume in optical science. The skills to produce optical data and the aspheric are seen as high technology today. The optical science which is composed of aspheric provides broadening view of things and high efficiency. In addition, it provides many advantages such as providing image and reducing the weight. Now, I study with techniques of processing and measuring aspheric to satisfy the necessity of increasing in aspheric data. Furthermore. I emphasize that the techniques of producing, measuring, and evaluating in the aspheric lenses have constantly developing today.

• Journal of Advanced Navigation Technology
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• v.13 no.1
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• pp.142-150
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• 2009

It is very important to generate a simplified model from a complex 3D character in computer game. We propose a new method of extracting feature lines from a 3D game character. Given an unstructured 3D character model containing texture information, we use model feature map (MFM), which is a 2D map that abstracts the variation of texture and curvature in the 3D character model. The MFM is created from both a texture map and a curvature map, which are produced separately by edge-detection to locate line features. The MFM can be edited interactively using standard image-processing tools. We demonstrate the technique on several data sets, including, but not limited to facial character.

• The KIPS Transactions:PartB
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• v.9B no.4
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• pp.459-464
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• 2002

In this paper, we propose a private digital watermarking method based on a wavelet transform to protect digital contents copyrights. We find out the optimal watermark insertion region and the optimal amount of watermark in order to satisfy robustness and imperceptibility against various attacks such as noise, compression, collusion, clipping, scaling to transfer the contents safely. Through this experiment, we could find out the adequate location of watermark insertion and proper amount of watermark, and transfer the watermarked image safely.

• Journal of radiological science and technology
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• v.1 no.1
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• pp.25-29
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• 1978

This study was done for the purpose of graphing rather improved technique through reviewing conventional technigue of the thoracic vertebrae lateral projection. The roentgenographic images which were taken at Korea University Hospital from January, 1976 to December, 1977 were observed for this study. The results were as belows: 1. The quality of diagnostic radiograph turned out that good is 21.4%, intermediate is 40.7% and poor is 37.9%. 2. The poor quality of images the caused by overlapping shadows(59.6%), incorrect position of patients(15.0%), motion of patients(7.5%), over-exposure(8.3%), under-exposure(6.7%) and processing faults(2.9%). The images were taken by following four methods of experiments were campared and researched in order to improve the problems of conventional technigues which were came out on the poor radiographes. 1. (Method 1) Low mA-long time exposure during normal respiration 2. (Method 2) Short time exposure during normal respiration 3. (Method 3) After deep inspiration, short time exposure during expiration 4. (Method 4) After full expiration, short time exposure during inspiration. In a result of the above experiments, it was found that the improved image could be got from the method 3.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1213-1221
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• 2020

Chromium-nickel alloy 42XNM (XHM-1, Bochvalloy) is considered as a promising material for future generations of nuclear reactors, primarily as a material for the fuel elements shells in the development of accident tolerant fuel. However, as with most nickel-based alloys, 42ХNМ is characterized by a sharp decrease in plastic properties in the temperature range of (500-900)℃. This effect is enhanced by neutron irradiation. Preliminary tests of ring samples of 42XNM alloy (after irradiation as a part of the VVER-1000 control system) in the temperature range of ductility failure showed that the standard technique for processing tensile diagrams does not allow to evaluate the plastic properties correctly at low strains. Therefore, in this work, the alternative method for testing ring samples from materials with low plastic characteristics was developed. It was shown that the minimum value of the permanent strain of the irradiated 42XNM alloy in the temperature range of (500-1100)℃, determined by the alternative method, was ~1.6% at 750 ℃.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.132-137
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• 2009

This study has regard to classification by using multi-temporal SAR data. Multi-temporal JERS-1 SAR images are used for extract the land cover information and possibility. So far, land cover information extracted by high resolution aerial photo, satellite images, and field survey. This study developed on multi-temporal land cover status monitoring and coherence information mapping can be processing by L band SAR image. From July, 1997 to October, 1998 JERS SAR images (9 scenes) coherence values are analyzed and then extracted land cover information factors, so on. This technique which forms the basis of what is called SAR Interferometry or InSAR for short has also been employed in spaceborne systems. In such systems the separation of the antennas, called the baseline is obtained by utilizing a single antenna in a repeat pass.