• Proceedings of the Optical Society of Korea Conference
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• 2007.02a
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• pp.307-308
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2007.02a
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• pp.315-316
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• 2007

• Korean Journal of Optics and Photonics
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• v.2 no.2
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• pp.103-107
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• 1991

Nonlinearity of glass had not been remarkably large among all the available nonlinear materials. However, its superiority in optical and mechanical properties has attracted much attention for the practical application. To this goal the recent interests in this field have been shifting from the understanding of nonlinear mechanisms to the improvements of nonlinear properties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1649-1657
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• 2006

Fizeau interferometer is well known optical instrument for measuring the lens profile accurately. The object of this study is focused on the design and optical measuring techniques for large optical components, such as a reflection mirror for astronomical purpose. Measuring of large optical lens, the object could not be moved as small one but the measuring instrument must be moved for the alignment, because of the geometric conditions and the accuracy of the stage. Therefore, a five axis stage is designed to align the Interferometer instead of the measuring object. This instrument will be used for an on machine measuring system in polishing machine for large optical lens.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.89-93
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• 2006

We investigate a method to improve the extinction ratio of directional couplers by controlling the angle of approach to their input ports and controlling the error limit for improving the extinction ratio of the directional coupler. Although relatively large angle of approach to the input port usually causes an error in calculations made by mode propagation analysis(MPA), optimally designed angle of approach not only minimizes errors in MPA calculations but also can improve extinction ratio by precision control of coupling coefficients of optical modes. We show that abrupt changes in approaching angle, although not enough to cause modal leakage, give rise to field-profile overshooting, which degrades extinction ratio and other properties of the directional coupler. Using Beam Propagation Method (BPM) we calculate two types of input structures, linear and curved, for optimization of extinction ratio.

• Korean Journal of Optics and Photonics
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• v.26 no.4
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• pp.226-232
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• 2015

A double-layer LED array together with an illumination optical system is proposed as a possible light source for LC projection display systems for large screens, up to $8m{\times}6m$ (400 inches diagonal). The heat dissipation problem of the LED array is solved by arranging the LEDs in double layers, and thermal analysis shows its effectiveness. The light from the LEDs in the back layer can be transmitted through the front layer without significant loss by arranging the LEDs in non-overlapping positions in the two layers and inserting suitable microlenses between the two layers and holes in the first layer. Together with the double-layer LEDs, an illumination optical system is designed to illuminate liquid crystal panels with good uniformity and appropriate matching with the projection optics.

• Korean Journal of Optics and Photonics
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• v.28 no.6
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• pp.304-313
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• 2017

The finite element analysis for optimizing a mirror system consisting of a large-diameter mirror and flexures requires numerous, repetitive calculations and corrections of the actual model to satisfy the given design conditions. In general, modification of this real model is conducted by reconfiguring nodes of the elements. The reconfiguration is very time-consuming work, to fix the continuity of each of the newly formed component nodes at the interfaces. But the process is a very important factor in determining the analysis time. To save time in modeling and actual computation, and to attain faster convergence, we present a new opto-mechanical analysis using non-shared node connections at each of the interfaces of the optical components. By comparing the results between the new element model and a conventional element model with shared node connections, we found that the opto-mechanical performance was almost the same, but the time to reach the given condition was drastically reduced.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.791-796
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• 2009

A hybrid iterative physical optics-method of moments(IPO-MoM) technique is presented for the analysis of jet engine structures which are both electrically large and complex. In this technique, the IPO method is used to analyze smooth inlet region and the MoM method is used to analyze electrically complex region inclusive of blades and hub. It is efficient and accurate by virtue of combining the respective merits of both methods. Numerical results are presented and validated through comparison with Mode-FDTD and measured results.

• Journal of Electrical Engineering and information Science
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• v.3 no.2
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• pp.151-157
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• 1998

Free-space optical interconnection networks can be classified into two types, space variant and space invariant, according to the degree of space variance. In terms of physical implementations, the degree of space variance can be interpreted as the degree of sharing beam steering optics among the nodes of a given network. This implies that all nodes in a totally space-invariant network can share a single beam steering optics to realize the given network topology, whereas, in a totally space variant network, each node requires a distinct beam steering optics. However, space invariant networks require mechanisms for distinguishing the origins of incoming signals detected at the node since several signals may arrive at the same time if the node degree of the network is greater than one. This paper presents a signal source encoding scheme for distinguishing incoming signals efficiently, in terms of the number of detectors at each node or the number of unique wavelengths. The proposed scheme is solved by developing a new parallel genetic algorithm called distributed asynchronous genetic algorithm (DAGA). Using the DAGA, we solved signal distinction schemes for various network sizes of several topologies such as hypercube, the mesh, and the de Brujin.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.150-155
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• 2016

To evaluate the autofocusing performance of recent mobile phone cameras, it is necessary to determine the peak position of the center field MTF (Modulation Transfer Function), -known as the through focus MTF- of the module. However, the MTF peak position found by conventional methods deviates from the ideal position due to the focus scanning resolution of mobile phone cameras. This inaccurate peak position results in false judgements of the optical performance, leading to yield losses or customer complaints. An increase in the focus scanning resolution can address this problem, but the manufacturing UPH (Unit per Hour) level will also unfortunately increase as well, resulting in a loss of manufacturing capabilities. In this paper, several fitting models are studied to find an accurate MTF peak position within a short period of time. With an analysis of a large amount of manufacturing data, it is demonstrated that the fitting methods can reduce false judgements and simultaneously increase the capabilities of the manufacturing system.