• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 동계학술발표회 논문집
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• pp.373-374
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• 2006

This paper physically demonstrates that our proposed method improves the Signal-to-Noise Ratio (SNR) of significantly increase the number of acceptable optical signals in PON(Passive Optical Network) systems. This method reduced Optical Beat Interference(OBI) by using CDMA.

• 한국전기전자재료학회논문지
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• 제25권3호
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• pp.209-212
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• 2012

In this paper, we have studied on the optimal design of the optical compensation film for the TN-LCDs. To have wide viewing angle panels, several methods such as multi-domain method, optical path method, and phase compensation method have been proposed. Among these methods, this paper focused on the phase compensation method. In the phase compensation method, the phase retardation generated from the optical birefringence for the off-axis incident is compensated by using optical films with refractive anisotropy. To compensate the phase retardation of the TN-LCDs, we have proposed design concept for the biaxial optical films and analyzed the optical performance for the proposed structures. The calculation of the dynamic motion of the liquid crystals was based on the Ericksen-Leslie theory and the optical performance of the TN-LCD was calculated from the Extended Jones Matrix Method. From the results, we have confirmed that the optical characteristics of the TN-LCDs with the biaxial films have been improved considerably compared with the TN-LCDs compensated by the combination of the uniaxial films.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.174-179
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• 2016

In this paper, a novel full-aperture reflective null measuring method is proposed to detect the transmission wavefront of a conformal dome surface. An aspheric compensator is designed and placed behind the dome to reflect the aspheric testing wave back to the same path. To ensure the feasibility of this method, tolerance analysis is conducted, and guidance to assembly is given accordingly. The accuracy of this method is verified to be λ/30 (λ =3.39 μm) by Monte Carlo algorithm. In addition, the influence of different error factors, including the thickness error and decenter error of the dome, on the testing wavefront is analyzed. Simulation and experiment indicate that this method is practical and simple, and can measure the conformal domes precisely and comprehensively.

• Journal of the Optical Society of Korea
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• 제16권4호
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• pp.354-364
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• 2012

In this paper, a new 2-step quadrature phase-shifting digital holographic optical encryption method using orthogonal polarization is proposed and tolerance errors for this method are analyzed. Unlike the conventional technique using a PZT mirror, the proposed optical setup comprises two input and output polarizers, and one ${\lambda}$/4-plate retarder. This method makes it easier to get a phase shift of ${\pi}$/2 without using a mechanically driven PZT device for phase-shifting and it simplifies the 2-step phase-shifting Mach-Zehnder interferometer setup for optical encryption. The decryption performance and tolerance error analysis for the proposed method are presented. Computer experiments show that the proposed method is an alternate candidate for 2-step quadrature phase-shifting digital holographic optical encryption applications.

• Journal of the Optical Society of Korea
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• 제17권1호
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• pp.38-43
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• 2013

In this study, we propose a simple and indirect method to determine the optical constants of Mo and ITO thin films in the extreme ultraviolet (EUV) wavelength region by using X-ray reflectometry (XRR) and Rutherford backscattering spectrometry (RBS). Mo and ITO films were deposited on silicon substrates by using an RF magnetron sputtering method. The density and the composition of the deposited films were evaluated from the XRR and RBS analysis, respectively and then the optical constants of the Mo and ITO films were determined by an indirect optical method. The results suggest that the indirect method by using the XRR and RBS analysis will be useful to search for suitable high absorbing EUVL mask material quickly.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.105-106
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• 2006

It is important to identify the exact target optical cable that a worker look for when he executes a cable construction work. Until now, An Optical cable identification work has been done by a manual pulling of an optical cable or by the method of using RF signals. But these methods not only consume much time and labor costs but also have a distance limit of the optical cable to identify. In this paper, we propose a method that uses the phase change signal of the optical interferometer to identify an optical cable. With the proposed method the field worker can have an efficient tool to prevent miscutting the optical cable and can also save operating costs.

• 한국광학회:학술대회논문집
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• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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• pp.174-175
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• 2001

This paper theoretically demonstrates that our proposed method improves the Signal-to-Noise Ratio (SNR) of significantly increase the number of acceptable optical signals in FDMA(SCMA) systems. This method reduced Optical Beat Interference(OBI) by using CDMA.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 하계학술발표회
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• pp.126-127
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• 2000

In this paper, we proposed an optical encryption method based in the concept of visual cryptography and interferometry. In our method a secret binary image was divided into two sub-images and they were encrypted by 'XOR' operation with a random key mask. Finally each encrypted image was changed into phase mask. By interference of these two phase masks the original image was obtained. Compared with general visual encryption method, this optical method had good signal-to-noise ratio due to no need to generate sub-pixels like visual encryption.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.477-484
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• 2014

In this paper, we propose a new optical secret key sharing method based on the Diffie-Hellman key exchange protocol required in cipher system. The proposed method is optically implemented by using a free-space interconnected optical logic gate technique in order to process XOR logic operations in parallel. Also, we present a compact type of optical module which can perform the modified Diffie-Hellman key exchange for a cryptographic system. Schematically, the proposed optical configuration has an advantage of producing an open public key and a shared secret key simultaneously. Another advantage is that our proposed key exchange system uses a similarity to double key encryption techniques to enhance security strength. This can provide a higher security cryptosystem than the conventional Diffie-Hellman key exchange protocol due to the complexity of the shared secret key. Results of numerical simulation are presented to verify the proposed method and show the effectiveness in the modified Diffie-Hellman key exchange system.

• 전자공학회논문지SC
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• 제47권5호
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• pp.24-32
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• 2010

본 연구에서는 Optical Flow Method의 추적 성능을 향상시키기 위한 전처리 알고리즘을 제안한다. 제안하는 알고리즘은 Median Filter, Binarization, Morphology, Canny Edge, Contour Detecting 및 Approximation Method를 기반으로 개발되었다. Optical Flow 추적 성능 향상 여부를 평가하기 위해 Lucas-Kanade Optical Flow 알고리즘에 개발된 전처리 알고리즘을 적용하고, 전처리 알고리즘이 적용되지 않은 Optical Flow 영상과 추적 결과를 비교 분석하였다. 또한, Median Filter와 Histogram Equalization으로 구성된 기존 전처리 알고리즘과의 결과 비교를 통해, 개발된 전처리 알고리즘의 추적 성능 향상여부를 평가하였다. 실험결과, 전처리 알고리즘을 적용하지 않은 영상과 기존 전처리 알고리즘을 적용한 영상은 특징영역의 분할이 이루어지지 않아, Optical Flow의 추적 정확도가 매우 낮게 나타났다. 반면, 개발된 전처리 알고리즘을 적용한 영상에서는 외곽선이 내외부로 세분화되고, 외곽선 트리가 구성됨에 따라 Optical Flow의 추적 성능이 매우 높게 나타났다.