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안전한 IPTV 서비스를 위한 멀티캐스트 DRM 시스템의 인증 기법에 관한 연구
장승재(Seungjae Jang),전상엽(Sangyeob Jeon),이영구(Younggu Lee),전문석(Moonseog Jun) 한국정보과학회 2009 한국정보과학회 학술발표논문집 Vol.36 No.2D
IPTV 서비스를 위한 멀티 캐스트 DRM 시스템은 악의적인 사용자에 의하여 그룹키나 채널키가 유출될 경우 불법적인 방송시청을 방지하는 기법이 요구된다. 본 논문에서 제안하는 멀티캐스트 DRM 시스템에서 악의적인 사용자에 의하여 키가 유출될 경우 사용자 아이디와 디바이스의 MAC(Media Access Control)을 이용하여 사용자에 대한 디바이스를 인증하고 현재 채널번호에서 얻은 그룹 번호와 사용자가 가입된 그룹 번호를 비교하여 채널에 대한 인증을 제안함으로써 기존 CAS의 문제점인 단방향 통신을 해결, IPTV의 잠정인 쌍방향 통신이 가능하게 하였고, 사용자의 디바이스와 채널을 이용한 두 가지 요소 인증으로 안전성을 향상 시켰다.
Retinal 3D : augmented reality near-eye display via pupil-tracked light field projection on retina
Jang, Changwon,Bang, Kiseung,Moon, Seokil,Kim, Jonghyun,Lee, Seungjae,Lee, Byoungho Association for Computing Machinery 2017 ACM transactions on graphics Vol. No.
<P>We introduce an augmented reality near-eye display dubbed 'Retinal 3D.' Key features of the proposed display system are as follows: Focus cues are provided by generating the pupil-tracked light field that can be directly projected onto the retina. Generated focus cues are valid over a large depth range since laser beams are shaped for a large depth of field (DOF). Pupil-tracked light field generation significantly reduces the needed information/computation load. Also, it provides 'dynamic eye-box' which can be a break-through that overcome the drawbacks of retinal projection-type displays. For implementation, we utilized a holographic optical element (HOE) as an image combiner, which allowed high transparency with a thin structure. Compared with current augmented reality displays, the proposed system shows competitive performances of a large field of view (FOV), high transparency, high contrast, high resolution, as well as focus cues in a large depth range. Two prototypes are presented along with experimental results and assessments. Analysis on the DOF of light rays and validity of focus cue generation are presented as well. Combination of pupil tracking and advanced near-eye display technique opens new possibilities of the future augmented reality.</P>
Holographic fluorescence microscopy with incoherent digital holographic adaptive optics
Jang, Changwon,Kim, Jonghyun,Clark, David C.,Lee, Seungjae,Lee, Byoungho,Kim, Myung K. SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS 2015 JOURNAL OF BIOMEDICAL OPTICS Vol.20 No.11
<P>Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: selfinterference incoherent digital holography (SIDH). The SIDH generates a complex?i.e., amplitude plus phase?hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.</P>
Jang, Changwon,Lee, Chang-Kun,Jeong, Jinsoo,Li, Gang,Lee, Seungjae,Yeom, Jiwoon,Hong, Keehoon,Lee, Byoungho The Optical Society 2016 Applied Optics Vol.55 No.3
<P>The principles and characteristics of see-through 3D displays are presented. We especially focus on the integral-imaging display system using a holographic optical element (IDHOE), which is able to display 3D images and satisfy the see-through property at the same time. The technique has the advantage of the high transparency and capability of displaying autostereoscopic 3D images. We have analyzed optical properties of IDHOE for both recording and displaying stages. Furthermore, various studies of new applications and system improvements for IDHOE are introduced. Thanks to the characteristics of holographic volume grating, it is possible to implement a full-color lens-array holographic optical element and conjugated reconstruction as well as 2D/3D convertible IDHOE. Studies on the improvements of viewing characteristics including a viewing angle, fill factor, and resolution are also presented. Lastly, essential issues and their possible solutions are discussed as future work. (C) 2015 Optical Society of America</P>
The Effects of Silica Nanoparticles in Macrophage Cells
Kim, Seungjae,Jang, Jiyoung,Kim, Hyojin,Choi, Hoon,Lee, Kangtaek,Choi, In-Hong The Korean Association of Immunobiologists 2012 Immune Network Vol.12 No.6
Silica nanoparticles, which are applicable in many industrial fields, have been reported to induce cellular changes such as cytotoxicity in various cells and fibrosis in lungs. Because the immune system is the primary targeting organ reacting to internalized exogenous nanoparticles, we tried to figure out the immunostimulatory effect of silica nanoparticles in macrophages using differently sized silica nanoparticles. Using U937 cells we assessed cytotoxicity by CCK-8 assay, ROS generation by CM-$H_2DCFDA$, intracellular $Ca^{{+}{+}}$ levels by staining with Fluo4-AM and IL-8 production by ELISA. At non-toxic concentration, the intracellular $Ca^{{+}{+}}$ level has increased immediately after exposure to 15 nm particles, not to larger particles. ROS generation was detected significantly in response to 15 nm particles. However, all three different sizes of silica nanoparticles induced IL-8 production. 15 nm silica nanoparticles are more stimulatory than larger particles in cytotoxicity, intracellular $Ca^{{+}{+}}$ increase and ROS generation. But IL-8 production was induced to same levels with 50 or 100 nm particles. Therefore, IL-8 production induced by silica nanoparticles may be dependent on other mechanisms rather than intracellular $Ca^{{+}{+}}$ increase and ROS generation.
Additive light field displays : realization of augmented reality with holographic optical elements
Lee, Seungjae,Jang, Changwon,Moon, Seokil,Cho, Jaebum,Lee, Byoungho Association for Computing Machinery 2016 ACM transactions on graphics Vol.35 No.4
<P>We propose a see-through additive light field display as a novel type of compressive light field display. We utilize holographic optical elements (HOEs) as transparent additive layers. The HOE layers are almost free from diffraction unlike spatial light modulator layers, which makes this additive light field display more advantageous when modifying the number of layers, thickness, and pixel density compared with conventional compressive displays. Meanwhile, the additive light field display maintains advantages of compressive light field displays. The proposed additive light field display shows bright and full-color volumetric images in high definition. In addition, users can view real-world scenes beyond the displays. Hence, we expect that our method can contribute to the realization of augmented reality. Here, we describe implementation of a prototype additive light field display with two additive layers, evaluate the performance of transparent HOE layers, describe several results of display experiments, discuss the diffraction effect of spatial light modulators, and analyze the ability of the additive light field display to express uncorrelated light fields.</P>
Analysis and Implementation of Hologram Lenses for See-Through Head-Mounted Display
Lee, Seungjae,Lee, Byounghyo,Cho, Jaebum,Jang, Changwon,Kim, Jonghyun,Lee, Byoungho IEEE 2017 IEEE Photonics Technology Letters Vol.29 No.1
<P>We introduce an approach to implementation of see-through head-mounted displays using hologram lenses, which are categorized by holographic optical elements. The hologram lenses magnify displayed images and superimpose the magnified images on the real-world simultaneously, which allows system configuration to be compact. Here, we investigate imaging properties and optical issues of hologram lenses using the spectral analysis of light field. Also, the astigmatism of hologram lenses is analyzed and its compensation method is proposed and verified. We conclude by describing display results and a practical application of the proposed method.</P>