• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.191-198
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• 2003

In this study, aberration free aspherical lens design method named ray reverse tracing method is introduced. Differently from the traditional design method, the ray reverse tracing method traces the shape and location of a real object by use of its virtual image. From the result, especially spherical aberration free aspherical lens could be designed by use of the ray reverse tracing method. Furthermore, it could reduce the degree of dependence of optical characteristics on designer's ability, because deformation terms and optimization can be eliminated, which has been performed in conventional lens design process.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.844-846
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• 2005

본 논문에서는 3차원 모델을 검색하기 위한 형태 기반 기술자를 추출하는 알고리즘을 제안한다. 제안하는 알고리즘은 모델의 기하학적인 특성을 고려하여 레이 캐스팅 샘플링과 구면조화함수를 이용하는 방법이다. 레이 캐스팅 기법은 모델의 외형을 고려한 적응적인 방법으로 샘플링 하여 기술자에 포함되는 형태 정보를 증가시켜 기술자의 식별성을 높인다. 또한 구면조화함수 계수 추출에서는 기하학적인 주파수 특성을 고려하여 적응적인 계수를 추출한다. 이 방법은 검색 성능에 영향을 미치지 않고 기술자를 조밀하고 간결하게 만든다. 최종적으로 두 방법을 결합함으로써 검색 엔진에서 이용 가능한 기술자를 생성한다. 실험 결과에서는 제안된 알고리즘의 성능이 기존 방법에 비해 약 $12.5\%$ 향상 된 것을 확인 할 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.05a
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• pp.560-563
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• 2021

본 논문에서는 사각형 실내 공간에서 점군 데이터를 기반으로 빠르고 정확하게 바닥, 천장, 벽면에 대한 평면 정보를 획득할 수 있는 시스템을 제안한다. 기존의 방법은 관측되지 않은 공간에 대한 평면을 예측할 수 없으며, 노이즈에 취약하고, 모든 점에 대한 기저 정보를 알아야하기 때문에 많은 연산량을 요구한다. 제안 방법은 기존의 평면 검출 방식에서 벗어나 Bounding Box 형상을 예측하는 기술을 활용한다. 또한, 제안 시스템은 구면 파노라마 비디오를 기반으로 적은 수의 프레임으로도 빠르게 실시간 점군 데이터를 확장해나간다. 제안 방법은 실험을 통해 기존의 방법보다 월등히 빠르고, 노이즈 등 환경 제약 요소에 강건함을 보인다.

• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.212-213
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• 2001

본 논문에서는 마이크로디스플레이용 광학계의 렌즈 설계와 시뮬레이션으로 구면수차, 비점수차, 왜곡, 색수차를 보정하여 설계한 광학계의 성능 평가를 소개하고자 한다.

• 한국전자현미경학회:학술대회논문집
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• 2004.05a
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• pp.69-73
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• 2004

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.206-207
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• 2002

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.3
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• pp.275-280
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• 2006

For this study, we analysed the difference of values between noncycloplegic and cycloplegic autorefraction in primary school children. We classified the elementary school one, two, three grade (8~10age) 79children(158eyes) who did not have strabismus or amblyopia. They were examined by using the Autorefractor in domestic market before and after cycloplegic. Discrepancies beyond 0.50D in spherical and cylindrical power and 20 degree in cylindrical axis were regarded as significant. The percentages of discrepancy were greater in spherical power between noncydoplegic and cycloplegic autorefraction(p<0.05). The percentages of discrepancy were not greater in cylindrical power between noncycloplegic and cycloplegic autorefraction. The percentages of discrepancy were greater in cylindrical axis between noncydoplegic and cycloplegic autorefraction(p<0.05). In conclusion, for the primary school children who did not wear glasses, the prediction table of this study will be helpful to reduce the test error in visual acuity and refractive error tests.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.490-499
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• 2006

In this paper, we present the newly developed propagation toss model of a long range maritime communication channel, measured by a ground to air flight test, and discuss its validity compared with the predictive value based on the spherical earth reflection model. To measure the propagation loss, actual flight test was performed in the Yellow Sea and the measurement of receiving signal strength was made for overall test range. As far as the test condition is concerned, it is expected that the receiving signal strength must be interfered with the reflected wave by an island existing around the reflection point. Therefore we introduce some modifications on the conventional spherical earth reflection model by including the effect due to the reflected wave from the island. And then, we compare the path loss measured by flight test with that one analyzed by the spherical earth reflection model accounting for reflected wave of the island. As a result of the comparison, it is verified to predict the path loss accurately by the spherical earth reflection model including the effect due to the reflected wave from an island for a long range ground to air communication.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.439-446
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• 2004

Many studies have reported that retinal defocus cause and increase refractive error specially myopia. Uncorrected astigmatism may be one factor of retinal defocus factors. To understand the relationship between myopia and astigmatism 62 college students were participated in this study. Spherical refractive error and astigmatism were measured using N-vision 5001 autorefractor (Shinnippon). Co-relations between spherical refractive error and astigmatism were high both in the with-the-rule astigmatism group(r=0.53; ANOVA F=32.40, N=87, P<0.05) and oblique astigmatism group (r=0.53ANOVA F=5.14, N=15, P<0.001). However it was very low (r=0.09; ANOVA F=0.18, N=22, P<0.001)in the against-the-rule stigmatism group. In the total group co-relation was also high (r=0.56: ANOVA F=77.80, N=173, P<0.001). Uncorrected astigmatism may cause and increase spherical refractive error.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.3
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• pp.27-33
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• 2007

This research investigated the effects of spherical and aspherical R.G.P lenses which was performed by optometrists in In-Cheon and Kyung-Gi region. This research survey included various questions such as the fitting status, after-care method, preliminary test. Results of the survey revealed that the optometriests sold the asperical and spherical lenses with a ratio of 7:3, respectively, and most of them did not cheked Topography, Fluorescein test by slit lamp biomicroscope, Tear Break up time test, Schirmer test and so on. And, with fitted R.G.P lenses symptoms like light odd-feeling, congestion, eye-stimulus, dimness and dryness were frequently reported. The purposes of this study are to search for the ideal fitting check of R.G.P lens and remind the most important preliminary test for contact lens fitting.