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Yeom, Jiwoon,Jeong, Jinsoo,Jang, Changwon,Li, Gang,Hong, Keehoon,Lee, Byoungho The Optical Society 2015 Applied Optics Vol.54 No.30
<P>We propose a 3D/2D convertible screen using a holographic optical element and angular multiplexing method of volume hologram. The proposed screen, named a multiplexed holographic optical element screen (MHOES), is composed of passive optical components, and displaying modes between 3D and 2D modes are converted according to projection directions. In a recording process, the angular multiplexing method by using two reference waves with different incidence angles enables the functions of 3D and 2D screens to be recorded in a single holographic material. Also, in order to avoid the bulky experimental setup due to adopting different projectors for the 3D and 2D modes, the projection part is realized based on a prism. The designed projection part enables the single projector to present 3D on 2D mode, where the 3D and 2D contents are simultaneously displayed in one scene, without active components. The optical characteristics of MHOES are experimentally analyzed, and displaying experiments with a full-color MHOES are presented in order to verify the 3D/2D convertibility and see-through properties. (C) 2015 Optical Society of America</P>
Yeom, Jiwoon,Hong, Keehoon,Jeong, Youngmo,Jang, Changwon,Lee, Byoungho Optical Society of America 2014 Optics express Vol.22 No.11
<P>We propose an optical pseudoscopic to orthoscopic conversion method for integral imaging using a lens-array holographic optical element (LAHOE), which solves the pseudoscopic problem. The LAHOE reconstructs an array of diverging spherical waves when a probe wave with the phase-conjugated condition is imposed on it, while an array of converging spherical waves is reconstructed in ordinary reconstruction. For given pseudoscopic elemental images, the array of the diverging spherical waves integrates the orthoscopic three-dimensional images without a distortion. The principle of the proposed method is verified by the experiments of displaying the integral imaging on the LAHOE using computer generated and optically acquired elemental images.</P>
Diagnosis and Clinical Course of Unexplained Dysphagia
Jiwoon Yeom,Young Seop Song,Won Kyung Lee,오병모,Tai Ryoon Han,서한길 대한재활의학회 2016 Annals of Rehabilitation Medicine Vol.40 No.1
Objective To investigate the final diagnosis of patients with unexplained dysphagia and the clinical and laboratory findings supporting the diagnosis.Methods We retrospectively analyzed 143 patients with dysphagia of unclear etiology who underwent a videofluoroscopic swallowing study (VFSS). The medical records were reviewed, and patients with a previous history of diseases that could affect swallowing were categorized into a missed group. The remaining patients were divided into an abnormal or normal VFSS group based on the VFSS findings. The clinical course and final diagnosis of each patient were examined.Results Among the 143 patients, 62 (43%) had a previous history of diseases that could affect swallowing. Of the remaining 81 patients, 58 (72.5%) had normal VFSS findings and 23 (27.5%) had abnormal VFSS findings. A clear cause of dysphagia was not identified in 9 of the 23 patients. In patients in whom a cause was determined, myopathy was the most common cause (n=6), followed by laryngeal neuropathy (n=4) and drug-induced dysphagia (n=3). The mean ages of the patients in the normal and abnormal VFSS groups differed significantly (62.52±15.00 vs. 76.83±10.24 years, respectively; p<0.001 by Student t-test).Conclusion Careful history taking and physical examination are the most important approaches for evaluating patients with unexplained swallowing difficulty. Even if VFSS findings are normal in the pharyngeal phase, some patients may need additional examinations. Electrodiagnostic studies and laboratory tests should be considered for patients with abnormal VFSS findings.
Hong, Keehoon,Yeom, Jiwoon,Jang, Changwon,Li, Gang,Hong, Jisoo,Lee, Byoungho Optical Society of America 2014 Optics express Vol.22 No.12
<P>Two-dimensional (2D) and three-dimensional (3D) transparent screens can be created using lens-array holographic optical elements (HOEs). Lens-array HOEs can be used to perform 2D and 3D imaging for Bragg matched images while maintaining the transparent properties of the images in the background scenes. 2D or 3D imaging on the proposed screen is determined by the relative size of an elemental-lens on the lens-array to a pixel on the projected image. The 2D and 3D displays on the lens-array HOEs are implemented by the diffusion of light on each elemental-lens and by taking advantage of reflection-type integral imaging, respectively. We constructed an HOE recording setup and recorded two lens-array HOEs having different optical specifications, permitting them to function as 2D and 3D transparent screens. Experiments regarding 2D and 3D imaging on the proposed transparent screens are carried out and the viewing characteristics in both cases are discussed. The experimental results show that the proposed screens are capable of providing 2D and 3D images properly while satisfying the see-through properties.</P>
Architecture Design of FPGA-SoC for Real-Time Tracking and Mapping in AR-Glasses
Yeseul Son,Jiwoon Yeom,Kwang-Soon Choi 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10
As Augmented Reality(AR) is applied to various industries, interest in AR is rapidly increasing. A key technology for displaying virtual objects in AR devices according to a user"s real environment is to grasp the user"s location and map the surrounding environment in real time. Localization and Mapping mainly uses a camera, so the amount of data to be processed is very large. Therefore, real-time tracking and mapping is possible when using a high-performance, high-clock, multi-threaded CPU on a PC. However, since the resources are limited in the embedded environment mounted on the AR glasses, it is difficult to perform real-time tracking and mapping using images. In this paper, we propose the FPGA-SoC architecture of Localization and Mapping IP, which can be manufactured with a small chip for mounting on AR glasses.
A frontal projection-type three-dimensional display.
Kim, Youngmin,Hong, Keehoon,Yeom, Jiwoon,Hong, Jisoo,Jung, Jae-Hyun,Lee, Yong Wook,Park, Jae-Hyeung,Lee, Byoungho Optical Society of America 2012 Optics express Vol.20 No.18
<P>In a typical auto-stereoscopic three-dimensional display, the parallax barrier or lenticular lens is located in front of the display device. However, in a projection-type auto-stereoscopic display, such optical components make it difficult to display elemental images on the screen or to reconstruct a three-dimensional image, even though a projection-type display has many advantages. Therefore, it is necessary to use a rear projection technique in a projection-type auto-stereoscopic display, despite the fact that this is an inefficient use of space. We propose here a frontal projection-type auto-stereoscopic display by using a polarizer and a quarter-wave retarding film. Since the proposed method uses a frontal projection scheme and passive polarizing components, it has the advantage of being both space saving and cost effective. This is the first report that describes a frontal projection-type auto-stereoscopic display based on a parallax barrier and integral imaging by using a projector. Experimental results that support the proposed method are provided.</P>
Li, Gang,Hong, Keehoon,Yeom, Jiwoon,Chen, Ni,Park, Jae-Hyeung,Kim, Nam,Lee, Byoungho Science in China Press 2014 Chinese optics letters Vol.12 No.6
Graphics processing unit (GPU) based fast calculation method for computer generated spherical hologram (CGSH) of a real-existing object is proposed. Three-dimensional (3D) point cloud is constructed by capturing a real-existing object from multiple directions using a depth camera. The GPU based calculation is used in both hologram generation part and numerical reconstruction part of the CGSH. The improved calculation efficiency is verified by comparing the computation speed between central processing unit (CPU) based and GPU based implementation.
Won Kyung Lee,Jiwoon Yeom,Woo Hyung Lee,서한길,Byung-Mo Oh,Tai Ryoon Han 대한재활의학회 2016 Annals of Rehabilitation Medicine Vol.40 No.3
Objective To compare the swallowing characteristics of dysphagic patients with traumatic brain injury (TBI) with those of dysphagic stroke patients.Methods Forty-one patients with TBI were selected from medical records (between December 2004 to March 2013) and matched to patients with stroke (n=41) based on age, sex, and disease duration. Patients’ swallowing characteristics were analyzed retrospectively using a videofluoroscopic swallowing study (VFSS) and compared between both groups. Following thorough review of medical records, patients who had a history of diseases that could affect swallowing function at the time of the study were excluded. Dysphagia characteristics and severity were evaluated using the American Speech-Language-Hearing Association National Outcome Measurement System swallowing scale, clinical dysphagia scale, and the videofluoroscopic dysphagia scale. Results There was a significant difference in radiological lesion location (p=0.024) between the two groups. The most common VFSS finding was aspiration or penetration, followed by decreased laryngeal elevation and reduced epiglottis inversion. Swallowing function, VFSS findings, or quantified dysphagia severity showed no significant differences between the groups. In a subgroup analysis of TBI patients, the incidence of tube feeding was higher in patients with surgical intervention than in those without (p=0.011). Conclusion The swallowing characteristics of dysphagic patients after TBI were comparable to those of dysphagic stroke patients. Common VFSS findings comprised aspiration or penetration, decreased laryngeal elevation, and reduced epiglottis inversion. Patients who underwent surgical intervention after TBI were at high risk of tube feeding requirement.