• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.348-353
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• 1999

Ray-optics approach based on the rigorous coupled wave theory, called by the rigorous ray-optics method (RROM), is developed for the calculation of couling coefficients of waveguide grating devices. The coupling coefficients of several grating structures, such as rectangular, sinusoidal, triangle, and trapezoidal shapes, are determined by the RROM, and they are compared with those obtained by conventional methods of the ray-optics method (ROM) and the coupled mode method (CMM). In the case of rectangular gratings, the coupling coefficients is evaluated in detail by various depths and duty-cycles of the grating. We have found that the RROM gives more exact solutions for the coupling coefficients of even arbitrary shapes of diffractive waveguide grating devices than the other conventional methods.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.8-17
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• 1999

In this paper, a proposal for improving the performance of IF in-phase combiner is presented in view of simple hardware design and good performance for space diversity application. By adding the stable normalization circuit to the phase detector, better performances are obtained even for a severe notch depth of 30 dB. To check the validity of this proposal, various results based upon numerical simulation and laboratory test are presented here in conjunction with 64-QAM digital radio relay system.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1311-1316
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• 2021

In this paper, we present a bifocal stereo camera system combining two cameras with different focal length cameras to generate stereoscopic image and their corresponding depth map. In order to obtain the depth data using the bifocal stereo camera system, we perform camera calibration to extract internal and external camera parameters for each camera. We calculate a common image plane and perform a image rectification for generating the depth map using camera parameters of bifocal stereo camera. Finally we use a SGM(Semi-global matching) algorithm to generate the depth map in this paper. The proposed bifocal stereo camera system can performs not only their own functions but also generates distance information about vehicles, pedestrians, and obstacles in the current driving environment. This made it possible to design safer autonomous vehicles.

• Journal of Broadcast Engineering
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• v.17 no.2
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• pp.363-373
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• 2012

This paper proposes a method to generate a depth image at an arbitrary intermediate view-point, which is targeting a video service for free-view, auto-stereoscopy, holography, etc. It assumes that the leftmost and the rightmost depth images are given and they both have been camera-calibrated and image-rectified. This method calculates and uses a disparity increment per depth value. In this paper, it is obtained by stereo matching for the given two depth image by considering more general cases. The disparity increment is used to find the location in the intermediate view-point depth image (IVPD) for each depth in the given images. Thus, this paper finds two IVPDs, from left image and from right image. Noises are removed and holes are filled in each IVPDs and the two results are combined to get the final IVPD. The proposed method was implemented and applied to several test sequences. The results revealed that the quality of the generated IVPD corresponds to 33.84dB of PSNR in average and it takes about 1 second to generate a HD IVPD. We evaluate that this image quality is quite good by considering the low correspondency among the left images, intermediate images, and the right images in the test sequences. If the execution speed is improved, the proposed method can be a very useful method to generate an IVPD at an arbitrary view-point, we believe.

• Korean Journal of Materials Research
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• v.1 no.4
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• pp.214-220
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• 1991

The effects of $SiO_2$ reactive ion etching (RIE) in $CHF_{3/}C_2F_6$ on the surface properties of the underlying Si substrate were studied by X-ray photoelectron spectroscopy(XPS) and secondary ion mass spectrometry(SIMS) techniques. Angle-resolved XPS analysis was carried out as non-destructive depth profile one for investigating the chemical bonding states of silicion, carbon, oxygen and fluorine. The residue layer consists of C-F polymer. O-F bond was found on the top of the polymer layer and Si-O, Si-C and Si-F bonds were detected between Si substrate and polymer film. A 60nm thick damaged layer of silicon surface mainly contains carbon and fluorine.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.122.2-122.2
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• 2015

n-type 실리콘은 p-type과 비교하여 더 높은 소수캐리어 lifetime 으로 금속 불순물에 대하여 더 좋은 내성을 갖는다. 고효율 실리콘 태양전지를 위하여 p-type 웨이퍼를 n-type으로 교체하여 빛을 조사했을 때, 광전자들이 형성되어 p-type과 비교하여 더 좋은 lifetime 안정성을 갖는다. n-type 태양전지의 전면 전극은 AgAl paste로 형성하였다. AgAl 페이스트는 소성 온도와 밀접하게 관련되어 전극의 접합 깊이에 영향을 미친다. p+ emitter 층에 파고드는 금속 접촉의 최적화된 깊이는 접촉 저항에 영향을 미치는 중요한 요소이다. 본 연구에서는 소성 조건을 변화시킴으로써, 금속 깊이의 효과적인 형성을 위한 소성 조건을 최적화하였다. $670^{\circ}C$ 이하의 온도에서 소성을 진행 하였을 때, 충분한 접촉 깊이를 형성하지 못하여 높은 접촉저항을 갖는다. 소성 온도가 증가함에 따라, 접촉 저항은 감소하였다. 최적 소성 온도 $865^{\circ}C$에서 측정된 접촉저항은 $5.99mWcm^2$이다. $900^{\circ}C$ 이상에서 contact junction은 emitter를 통과하여 실리콘과 결합하였다. 그 결과로 접촉저항 shunt가 발생한다.

• The Transactions of the Korea Information Processing Society
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• v.3 no.4
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• pp.926-937
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• 1996

A graph traversal technique is a certain pattern of visiting nodes of a graph. Many special traversal techniques have been applied to solve graph related problems. For example, the depth first search technique has been used for finding strongly onnected components of a directed graph or biconnected components of a general graph. The distributed protocol to implement his depth first search technique on the distributed network can be divided into a fixed topology problem where there is no topological change and a dynamic topology problem which has some topological changes. Therefore, in this paper, we present a more efficient distributed depth first search protocol with fixed topology and a resilient distributed depth first search protocol where there are topological changes for the distributed network. Also, we analysed the message and time complexity of the presented protocols and showed the improved results than the complexities of the other distributed depth first search protocols.

• Journal of Broadcast Engineering
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• v.21 no.6
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• pp.957-964
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• 2016

Acquisition of reliable depth maps is a critical requirement in many applications such as 3D videos and free-viewpoint TV. Depth information can be obtained from the object directly using physical sensors, such as infrared ray (IR) sensors. Recently, Time-of-Flight (ToF) range camera including KINECT depth camera became popular alternatives for dense depth sensing. Although ToF cameras can capture depth information for object in real time, but are noisy and subject to low resolutions. Recently, filter-based depth up-sampling algorithms such as joint bilateral upsampling (JBU) and noise-aware filter for depth up-sampling (NAFDU) have been proposed to get high quality depth information. However, these methods often lead to texture copying in the upsampled depth map. To overcome this limitation, we formulate a convex optimization problem using higher order regularization for depth map upsampling. We decrease the texture copying problem of the upsampled depth map by using edge weighting term that chosen by the edge information. Experimental results have shown that our scheme produced more reliable depth maps compared with previous methods.

• Journal of Periodontal and Implant Science
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• v.34 no.1
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• pp.113-126
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• 2004

연구목적 : 이번 실험의 목적은 외과적으로 형성된 성견의 1면 골내낭에 새롭게 제조된, Ca/P 비율이 0.6인 비결정성 calcium phosphate를 적용하였을 때 치주조직의 재생에 미치는 영향을 평가하는 것이다. 연구방법 : 6마리 성견의 양측 하악 제2소구치의 원심면, 제4소구치의 근섬면에 외과적으로 1면 골내낭을 형성하여 치은박리소파술을 시행한 부위를 대조군으로, calcium phosphate만을 이식한 부위를 실험 1군, calcium phosphate와 GTR을 동반한 부위를 실험 2군으로 설정하고 실험하여 술 후 8주에 치유결과를 조직학적으로 관찰하였다. 결론 : 1. 접합상피의 치근단 이동은 대조군에서 결손부 깊이의 30.90 ${\pm}$ 9.92%, 실험 1군에서 결손부 깊이의 24.08 ${\pm}$ 9.12%, 실험 2군에서 결손부 깊이의 38.68 ${\pm}$ 12.22%로 나타났으며 대조군과 실험 1,2군간에 통계적 유의차는 없었다. 2. 결합조직 유착은 대조군에서 결손부 깊이의 36.38 ${\pm}$ 9.03%, 실험 1군에서 결손부 깊이의 26.96 ${\pm}$ 4.24%, 실험 2군에서 결손부 깊이의 27.87 ${\pm}$ 9.70%로 나타났으며 대조군과 실험 1,2군간에 통계적 유의차는 없었다. 3. 신생백악질 형성은 대조군에서 결손부 깊이의 32.92 ${\pm}$ 10.51%, 실험 1군에서 결손부 깊이의 49.16 ${\pm}$ 12.70%, 실험 2군에서 결손부 깊이의 39.62 ${\pm}$ 12.14%로 나타났으며 대조군과 실험 1군간에 통계적 유의차가 있었다. 4. 신생골 형성은 대조군에서 결손부 깊이의 27.24 ${\pm}$ 7.49%, 실험 1군에서 결손부 깊이의 43.51 ${\pm}$ 13.34%, 실험 2군에서 결손부 깊이의 36.47 ${\pm}$ 15.11%로 나타났으며 대조군과 실험 1, 2군간에 통계적 유의차는 없었다. 이상의 결과에서 볼 때, calcium phosphate glasses는 신생골 형성에는 통계적으로 유의차는 없었지만 상당히 증가된 양상을 보였고 신생백악질 형성에는 크게 기여함을 알수 있었다.

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.419-423
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• 1999

Optical filters utilizing the evanescent filed coupling between the side polished fiber and polymer planar waveguide were fabricated and optical properties of the devices were measured. A scheme for reducing polarization dependent properties of the device was proposed and demonstrated experimentally. Our measurement results showed that resonance wavelengths and filtering depth of the optical filters can be determined by adjusting thickness of planar waveguide and polishing depth of the fiber. The device fabrication procedure including fiber polishing steps and formation of polymer planar waveguide were described. The optical characteristics of fabricated optical filers were that 3 dB bandwidth was 15 nm, the resonance wavelength difference between the TE and TM polarized response was less then 2 nm, and insertion loss was less then 0.2 dB. The measured resonance wavelength drift dut to the variation of ambient temperature was -0.35 nm/$^{\circ}C$.