• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.6
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• pp.400-407
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• 2003

In this paper an optical encryption system, which can decrypt the original image by using the autocorrelation terms of a JTC, is proposed. Unlike the classical JTC, the joint input plane of the proposed system is composed in a frequency domain not a spatial domain, thus it needs only one Fourier transformation. To use like this, the phase component appeared in the output plane of JTC should be considered. We presents the effect of phase and provides the solution. An original image is encrypted to a complex-valued random image. The original image is reconstructed using the autocorrelation terms which is the main drawback of JTC, therefore the proposed system is more suitable for JTC and real time processing. By computer simulation and optical experiment, the analysis for the phase effect and the performance of the proposed system are confirmed.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.1319-1324
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• 2006

최근 다양한 분야(건축, 디자인, 영화관)에서 활용되는 디스플레이 기술들은 대체로 평면에 투영하는 프로젝션 기술을 사용하고 있다. 예외적으로 평면이 아닌 곡면에 투영하는 경우도 있었으나, 기술적인 제약으로 왜곡된 영상을 보정하여 사용하는 경우는 드문 상태이다. 그리고 상호작용의 경우는 기계적 장치에 의존한 초보적 형태가 주류를 이루고 있다. 본 논문에서는 프로젝션 기술 중에서 원통형 곡면상으로의 투영 기법과 모션인식을 반영한 상호작용 기법에 대해서 논하고자 한다. 3D 영상을 곡면에 왜곡 없이 투영하기 위하여, 본 논문에서는 '2-pass 렌더링' 기법을 이용하였다. 이 기법에서는 현재 렌더링 된 영상을 텍스쳐로 저장한 다음 원통형 물체에 매핑시켜 곡면에 적합한 영상으로 보정한다. 그리고 기계적 장치에 의존하지 않는 상호작용을 위해, 카메라를 통하여 실시간으로 사용자 정보(위치, 방향 값)를 입력 받아 원통형 스크린과 매칭되는 좌표 값을 계산한다. 위와 같은 기법들을 구현하기 위한 실험으로 미디어 아트 작품을 제작하였으며, 투영과 상호작용에 관한 알고리즘을 작품에 적용하였다. 이 작품은 하나의 프로젝터를 사용하여 1/4 원통형 곡면으로의 투영과 상호작용을 수행하였다. 본 연구의 결과는 미디어 아트 작품의 프로젝션 모듈로 사용 될 수 있으며, 공연장 건축, 실내디자인, 체감형 인터랙티브 게임, 가상현실 영화관 등 다양한 분야에 적용 될 수 있다.

• Journal of the Korea Computer Industry Society
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• v.2 no.12
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• pp.1609-1616
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• 2001

We present an autostereoscopic 3D display system using volume hologram. In this proposed system, the interference pattern of angular multiplexed plane reference and object beams are recorded into a volume hologram, which plays a role of guiding object beams of multi-view images into the desired perspective directions. For reconstruction, object beams containing the desired multi-view image information, which satisfy Bragg matching condition, are illuminated in the time-division multiplexed manner onto the crystal. Then multiple stereoscopic images are projected to the display plane for autostereoscopic 3D viewing. It is possible to make a high resolution multiview 3D display system independent upon the viewpoint.

• Radiation Oncology Journal
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• v.17 no.3
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• pp.249-255
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• 1999

Purpose : The purpose of this study is to investigate fundamental aspects of the dose response of fluorescent screen-based electronic portal imaging devices (EPIDS). Materials and Methods : We acquired scanned signal across portal planes as we varied the radiation that entered the EPID by changing the thickness and anatomy of the phantom as well as the air gap between the phantom and the EPID. In addition, we simulated the relative contribution of the scintillation light signal in the EPID system. Results : We have shown that the dose profile across portal planes is a function of the air gap and phantom thickness. We have also found that depending on the density change within the phantom geometry, errors associated with dose response based on the EPID scan can be as high as $7\%$. We also found that scintillation light scattering within the EPID system is an important source of error. Conclusion : This study revealed and demonstrated fundamental characteristics of dose response of EPID, as relative to that of ion chambers. This study showed that EPID based on fluorescent screen cannot be an accurate dosimetry system.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.176-183
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• 2013

We propose a rolled fingerprint merging algorithm that effectively merges plain fingerprints in consecutive frame units that are fed through rolling and detects more fingerprint minutiae in order to increase the fingerprint recognition rate. The proposed rolled fingerprint merging algorithm uses a adaptive projection mask; it contains a detector that separates plain fingerprints from the background and a projection mask generator that sequentially projects the detect ed images. In addition, in the merging unit, the pyramid-shaped projection method is used to detect merged rolled fingerprints from the generated variable projective mask, starting from the main images. Simulations show that the extracted minutia e are 46.79% more than those from plain fingerprints, and the proposed algorithm exhibits excellent performance by detecting 52.0% more good fingerprint minutiae that are needed for matching.

• Journal of Korea Society of Industrial Information Systems
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• v.9 no.2
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• pp.59-64
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• 2004

Most features of nature and phenomena we encounter in many branches of science are inherently very irregular and have fractal aspects. Thus the analysis of them with the traditional methods such as a differential operator may result in their ill-posed problems. To settle these problems, one may use several type of mean filters which smooth the input signal. However when a given function or data are complex in their nature, there may be loss of some original information during these process. In this paper, we utilized the tangent plane method instead of mean filters for the purpose of less loss of information and more smoothness. After then we attempt to take more accurate edges for the irregular image on the basis of the Otzu threshold. Finally we introduce the effective edge extracting method which use the fractal dimension representing the complexity of the given image.

• Journal of Internet Computing and Services
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• v.11 no.2
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• pp.99-107
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• 2010

In this paper a blind watermarking algorithm for digital image is presented. The proposed method operates in wavelet domain. The watermark is decomposed into 2D-IMFs using BEMD which is the 2-dimensional extension of 1 dimensional empirical mode decomposition. The CDMA based on SS technique is applied to watermark embedding and detection process. In the watermark embedding process, each IMF of watermark is embedded into middle frequency subimages in wavelet domain, so subimages just include partial information about embedded watermark. By characteristics of BEMD, when the partial information of watermark is synthesized, the original watermark is reconstructed. The experimental results show that the proposed watermarking algorithm is imperceptible and moreover is robust against JPEG compression, common image processing distortions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3C
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• pp.398-407
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• 2004

In this paper, a blind watermarking method which is suitable to the video compression using 2-D discrete wavelet transform was proposed and implemented into the hardware using VHDL(VHSIC Hardware Description Language). The goal of the proposed watermarking algorithm is the authentication about the manipulation of the watermark embedded image and the detection of the error positions. Considering the compressed video image, the proposed watermarking scheme is unrelated to the quantization and is able to concurrently embed or extract the watermark. We experimentally verified that the lowest frequency subband(LL4) is not sensitive to the change in the spatial domain, so LL4 subband was selected for the mark space. And the combination of the bitplanes which has the properties of both the minimum degradation of the image and the robustness was chosen as the embedded Point in the mark space in LL4 subband. Since we know the watermark embedded positions and the watermark is embedded by not varying the value but changing the value, the watermark can be extracted without the original image. Also, for the security when exposing the watermark embedded position, we embed the encrypted watermark by the block cipher. The proposed watermark algorithm shows the robustness against the general image manipulation and is easily transplanted into the image or video compressor with the minimal changing in the structure. The designed hardware has 4037 LABs(24％) and 85 ESBs(3％) in APEX20KC EP20K400CF672C7 FPGA of Altera and stably operates in 82MHz clock frequency.

• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.361-367
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• 2024

Ultrasound in the air is widely used in industry as a measurement technique to prevent abnormalities in the machinery. Recently, the use of airborne ultrasound imaging techniques, which can find the location of abnormalities using an array transducers, is increasing. A beamforming method that uses the phase difference for each sensor is used to visualize the location of the ultrasonic sound source. We exploit a random sparse ultrasonic array and obtain beamforming power distribution on the source in a certain distance away from the array. Conventional beamforming methods inevitably have limited spatial resolution depending on the number of sensors used and the aperture size. A high-resolution ultrasound imaging technique was implemented by applying functional beamforming as a method to overcome the geometric constraints of the array. The functional beamforming method can be expressed as a generalized beam forming method mathematically, and has the advantage of being able to obtain high-resolution imaging by reducing main-lobe width and side lobes. As a result of observation through computer simulation, it was verified that the resolution of the ultrasonic source in the air was successfully increased by functional beamforming using the ultrasonic sparse array.

• The Korean Journal of Nuclear Medicine Technology
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• v.22 no.1
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• pp.90-97
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• 2018

Purpose The lung segment ratio which is obtained through quantitative analyses of lung perfusion scan images is calculated to evaluate the lung function pre and post surgery. In this Study, the planar image production methods by using Q-Metrix (GE Healthcare, USA) program capable of not only quantitative analysis but also computation of the segment ratio after having performed SPECT/CT are comparatively evaluated. Materials and Methods Lung perfusion scan and SPECT/CT were performed on 50 lung cancer patients prior to surgery who visited our hospital from May 1, 2015 to September 13, 2016 by using Discovery 670(GE Healthcare, USA) equipment. AP(Anterior Posterior)method that uses planar image divided the frontal and rear images into three rectangular portions by means of ROI tool while PO(Posterior Oblique)method computed the segment ratio by dividing the right lobe into three parts and the left lobe into two parts on the oblique image. Segment ratio was computed by setting the ROI and VOI in the CT image by using Q-Metrix program and statistically analysis was performed with SPSS Ver. 23. Results Regarding the correlation concordance rate of Q-Metrix and AP methods, RUL(Right upper lobe), RML(Right middle lobe) and RLL(Right lower lobe) were 0.224, 0.035 and 0.447. LUL(Left upper lobe) and LLL(Left lower lobe) were found to be 0.643 and 0.456, respectively. In the PO method, the right lobe were 0.663, 0.623 and 0.702, respectively, while the left lobe were 0.754 and 0.823. When comparison was made by using the Paired sample T-test, Right lobe were $11.6{\pm}4.5$, $26.9{\pm}6.2$ and $17.8{\pm}4.2$, respectively in the AP method. Left lobe were $28.4{\pm}4.8$ and $15.4{\pm}5.6$. The right lobe of PO had values of $17.4{\pm}5.0$, $10.5{\pm}3.6$ and $27.3{\pm}6.0$, while the left lobe had values of $21.6{\pm}4.8$ and $23.1{\pm}6.6$, thereby having statistically significant difference in comparison to the Q-Metrix method for each of the lobes (P<0.05). However, there was no statistically significant difference in Right middle lobe (P>0.05). Conclusion The AP method showed low concordance rate in correlation with the Q-Metrix method. However, PO method displayed high concordance rate overall. although AP method had significant differences in all lobes, there was no significant difference in Right middle lobe of PO method. Therefore, at the time of production of lung perfusion scan results, utilization of Q-Metrix method of SPECT/CT would be useful in computation of accurate resultant values. Moreover, it is deemed possible to expect obtain more practical sectional computation result values by using PO method at the time of planar image acquisition.