• Journal of Korean Ophthalmic Optics Society
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• v.10 no.1
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• pp.53-61
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• 2005

In this study, we measured Near Point of Convergence(N.P.C) tests, Phoria tests using Von Grafe method and relative convergence tests on 138 men and 162 women, so a total of 300 subjects aged between 8~45 to examine the improvement of the fusion vergence through visual training and obtained as follows. 1. According to the results, the near point of convergence of 57 (19%) subjects were shorter than 7cm, and 243 (81%) were 7cm or longer, having a problem in convergence. After visual training, the number of subjects have the value shorter than 7 cm increased from 57 to 111 (37%), and the number of those have the value 7cm or longer decreased significantly form 243 to 189 (63%). 2. The results of the measure of lateral Phoria at far distance by Von Grafe method showed orthophoria 18 (6%), exophoria 198 (66%), esophoria 84 (28%). After phoria test, we examined the N.R.C and P.R.C test. The results showed that the hope finger was improved after V.T using B.l, B.O card. 3. The results of the measure of lateral Phoria at near distance by Von Grafe method showed orthophoria 6 (2%), exophoria 222 (74%), esophoria 72 (24%). After phoria test, we examine the N.R.C and P.R.C test. The results showed that the hope finger was improved after V.T using B.I, B.O card.

• Journal of applied mathematics & informatics
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• v.25 no.1_2
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• pp.315-327
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• 2007

Mathematical aspects of the electromagnetic surface-wave propagation are examined for the dielectric core consisting of multiple sub-layers, which are embedded in the gap between the two bounding cladding metals. For this purpose, the linear problem with a partial differential wave equation is formulated into a nonlinear eigenvalue problem. The resulting eigenvalue is found to exist only for a certain combination of the material densities and the number of the multiple sub-layers. The implications of several limiting cases are discussed in terms of electromagnetic characteristics.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.956-961
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• 2004

This paper proposes a study on the spherical lens manufacturing by simultaneous 3 axis for NC lathe. We use friction drive system for moving system in experimental diamond turing machine. The diamond turning machine use manufacturing for high quality lens, mirror and many optics products. Especially, the high tech industry require a lot of lens. For example, optical engineering. medical science, space engineering and material engineering etc. The friction drive system is very simple and quiet, compared to ball screw system. We find a problem at the simultaneous 3 axis and suggest a solution. Also, when we manufactured a micro lens. find a problem and solution.

• Current Optics and Photonics
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• v.2 no.1
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• pp.39-46
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• 2018

Visible-light communication (VLC) combined with advanced illumination can be expected to become an integral part of next-generation communication networks. One of the major concerns in VLC implementation is developing resource-allocation schemes in a multi-user scenario. However, the scheduling for heterogeneous quality of service (QoS) traffic has not been studied so far, for the indoor VLC downlink system. In this paper, we creatively introduce effective-bandwidth and effective-capacity theory into the multi-user scheduling (MUS) problem, to guarantee the user's statistical delay QoS. We also take account of the aggregate interference (AI) in the indoor VLC downlink system, and analyze its impact on the user-centric MUS problem for the first time. Simulations show that the AI has a nonnegligible influence on the scheduling result, and that the proposed scheduling scheme could guarantee the user's QoS requirement under the premise of ensuring sum capacity.

• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.439-444
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• 1994

When diffraction by arbitrary two-dimensional surface-relief dielectric gratings is analyzed using the rigorous three-dimensional vector coupled-wave analysis, it is found that the matrix eigenvalue problem pertaining to the analysis can always be simplified to that for a matrix which has the dimension of a quarter of the original, so that computing time and memory requirements for computer may be greatly reduced. However this kind of simplification can not be obtained in the case of volume diffraction gratings. tings.

• Current Optics and Photonics
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• v.1 no.6
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• pp.626-630
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• 2017

GaN-based green light-emitting diode (LED) structures suffer from low internal quantum efficiency (IQE), known as the "green gap" problem. The IQE of LED structures is expected to be improved to some extent by exploiting the Purcell effect. In this study, the Purcell effect on the IQE of green LED structures is investigated numerically using a finite-difference time-domain simulation. The Purcell factor of flip-chip LED structures is found to be more than three times as high as that of epi-up LED structures, which is attributed to the high-reflectance mirror near the active region in the flip-chip LED structures. When the unmodified IQE is 20%, the relative enhancement of IQE can be greater than 50%, without utilizing the surface-plasmon coupling effect. Based on the simulation results, the "green gap" problem of GaN-based green LEDs is expected to be mitigated significantly by optimizing flip-chip LED structures to maximize the Purcell effect.

• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.112-119
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• 1996

TM polarized photon tunneling time and the position where TM photons appear after two-dimensional tunneling in a frustrated total internal reflection (FTIR) structure are calculated. This is done by converting the FTIR tunneling problem of TM photons to an electron tunneling problem with a position-dependent effective mass for a heterostructure potential barrier. Derived results are compared with TE photon cases.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.06a
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• pp.15-18
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• 2003

Most numerical techniques such as FEM, BEM, and MOM are able to analize electromagnetic scattering problems from arbitrary shapes. Although these methods could be applied to compute electromagnetic scattering problems in frequency domain, it was limited for electrodynamic problem in time domain. In this paper, electromagnetic scattering problem from Fresnel zone plate lens are considered. Some numerical results computed by TLM are compared with Kirchhoff's approximation and PO method.

• Current Optics and Photonics
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• v.2 no.5
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• pp.436-442
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• 2018

In a spatially interlaced stereoscopic (SIS) three-dimensional (3D) display to be realized by providing the observer a part of left-eye/right-eye images, a loss of information can be perceived due to the un-shown part of each image. In order to resolve that problem, an improved SIS 3D display is proposed to deliver the images without loss of information to the observer using a time-multiplexing scheme. However, that time-multiplexing SIS also has a problem of luminance distortion when the desired luminance is not shown due to an insufficient response of the liquid crystal cell. In this paper, we propose a new method by optimizing the image data to show correct luminance with minimum distortion.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.105-115
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• 2004

In developed and industrialized countries life expectancy has increased significantly over the past century. As a consequence, the proportion of elderly individuals in these countries has also enlarged with the resulting increased burden on health care providers. In many developing countries the problem of age related and other eye disorders has far outstripped the ability to manage them. Accordingly, the World Health Organization (WHO) has introduced an initiative: Vision 2020 - The Right to Sight, with the objective of eliminating preventable blindness by the year 2020. This paper reviews the broad range of conditions involving external and internal structures of the eye and also the effects of aging on visual functions. It is hoped that this will provide a stimulus for increased study of these disorders, improved clinical diagnosis, and an enhanced interest and role in contributing to the objectives of the WHO and the World Council of Optometry with respect to early diagnosis, prevention and management of the diseases and disorders of the eye that are more prevalent in old age.