• Korean Journal of Optics and Photonics
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• v.29 no.5
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• pp.204-214
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• 2018

Since LIDAR is advantageous for accurate information acquisition and realization of a high-resolution 3D image based on characteristics that can be precisely measured, it is essential to autonomous navigation systems that require acquisition and judgment of accurate peripheral information without user intervention. Recently, as an autonomous navigation system applying LIDAR has been utilized in human living space, it is necessary to solve the eye-safety problem, and to make reliable judgment through accurate obstacle recognition in various environments. In this paper, we construct a single-shot LIDAR system (SSLs) using a 1550-nm eye-safe light source, and report the analysis method and results of LIDAR signals for various measurement environments, reflective materials, and material angles. We analyze the signals of materials with different reflectance in each measurement environment by using a 5% Al reflector and a building wall located at a distance of 25 m, under indoor, daytime, and nighttime conditions. In addition, signal analysis of the angle change of the material is carried out, considering actual obstacles at various angles. This signal analysis has the merit of possibly confirming the correlation between measurement environment, reflection conditions, and LIDAR signal, by using the SNR to determine the reliability of the received information, and the timing jitter, which is an index of the accuracy of the distance information.

• Journal of IKEEE
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• v.27 no.4
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• pp.512-517
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• 2023

In this study, we propose a liquid crystal-based polarization control technology that can control polarization by adjusting the voltage applied to the liquid crystal, and apply it to a Closed-circuit Television (CCTV) to transmit only the desired angle of polarized light. CCTV with conventional polarizing films cannot control polarization because they focus on backlight compensation, so light reflected from the water surface or highlights reflected from vehicles interfere with subject identification. However, the Vertical Alignment mode allows the polarization to be adjusted electrically, so that only the polarized light at the user's desired angle is transmitted, eliminating reflected highlights. The images obtained using this technique are optimized by computer software. Liquid crystal polarization panels, which can electrically control the polarization angle, transmittance, and polarization rate, have been applied to polarized image monitoring device to improve subject identification in conventional CCTV.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.4
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• pp.91-97
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• 2014

In this research, we would try to evaluate the applicability in cadastral resurvey surveying by analysing the accuracy of building boundary surveying using the reflective sheet total station surveying. When we analyse it, we refer the reflective sheet which can supplement not only the difficulties of total station surveying and GPS surveying caused by the diversity of the building structure but also the errors of non prism total station caused by material of the object. Each reflected angles $90^{\circ}$ and $60^{\circ}$, $30^{\circ}$ of RMSE results were analyzed by RMSE between 1.2mm~2.8mm and 2.2mm~4.0mm, 2.5mm~4.4mm for each distance. The result of X RMSE was analyzed to be 0.0043m in a boundary surveying for existing building between prism surveying and reflective sheet surveying, and also Y RMSE was 0.038m. The source of error is estimated that the body of the prism can not be exactly attached to the edge of a building. Therefore, it will be very helpful to use a reflective sheet surveying with a prism in both the limit of collimation and error reductions as a building boundary measurement in cadastral resurvey surveying.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1271-1281
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• 2000

본 논문에서는 모드 매칭법과 일반 산란계수법을 이용하여 경사진 금속봉이 도파란내에 놓여 있을 때 반사 특성과 투과 특성을 구하였으면, 이 결과를 이용하여 동축선로와 도파관과의 접합에 응용할 수 있도록 최적의 조건을 도출하였다. 여기서 반사특성은 기울기사 클수록 뚜렷아세 개선되어서 최소-40dB까지 감소하였고, 투과특성은 최적의 각도 45$^{\circ}$에서 최대의 특성을 얻을 수 있었다. 또한, 이를 HFSS의 결과와 비교하였을 때 잘일치하는 결과를 얻을 수 있었다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.268-269
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• 2003

삼성전자는 LCD 방식에 이은 3세대 프로젝션 모델로 평가받는 DMD (Digital Micromirror Device) 기술을 채용한 43‘’, 50‘’, 61‘’ DLP (Digital Light Processing) 프로젝션 TV를 개발 시판하고 있다. DMD 기술이란 921,600개의 미세한 거울들이 신호에 따라 반사각도를 조절하며 이미지를 구현하는 기술이다. 삼판식 프로젝션 시스템의 단점을 개선, 경박단소와 저가격화를 위하여 단판식을 이용하는 DLP 프로젝션 TV 의 경우 Red, Green, Blue 로 이뤄진 칼라휠을 회전시킴으로서 DMD 위에 연속적으로 삼색의 영상을 재생하여 색을 분리 합성한다. (중략)

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.538-542
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• 2005

본 연구에서는 Penney와 Price(1952)의 해석 해를 사용하여 반무한방파제, 양익방파제등에서 발생하는 회절현상에 대한 해석 해를 구하였다. 양익방파제가 경사지게 위치한 경우에도 중첩을 통하여 해석 해를 구할 수 있었으며, 이를 바탕으로 방파제의 위치와 입사파랑의 각도에 따른 각각의 경우에 대하여 해석 해를 구할 수 있다. 또한, 구조물에 입사된 파랑성분과 구조물의 폭만큼의 개구부를 갖는 양익방파제를 통과하는 회절파성분과 같게 표현될 수 있는 반사파성분을 서로 중첩시켜 구조물 전면부에서 발생되는 완전반사 및 부분반사현상에 대한 해석 해를 제시하였다. 국내의 실무에서 해안 및 항만 구조물 설계에 사용되는 수치프로그램들의 정확도를 간단히 판단할 수 있는 비교 대상으로 이러한 해석해가 이용될 수 있으리라 판단된다.

• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.46-52
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• 2010

A theory of bidirectional reflectance-distribution function (BRDF), a newly developed BRDF measurement system, and a method for evaluating the uncertainty of BRDF measurements are presented. The BRDF measurement system which measures BRDF in a wavelength range of (380~1500) nm with an angle range of $(-75{\sim}75)^{\circ}$ was installed. The measurement uncertainties, consisting of correlated terms and uncorrelated terms, were evaluated for the BRDF measurement system, resulting in the relative expanded uncertainty less than 3% (k=2).

• Journal of IKEEE
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• v.23 no.3
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• pp.1077-1081
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• 2019

Lights that enter the surface of a solar cell cannot be absorbed inside all of the solar cells, and some of it is reflected off the surface of the substrate, resulting in loss. Because of this, many studies are underway to reduce reflective losses on the surface of substrates or to steam the generated charge inside the solar cell. In this paper, surface treatment for forming a rough surface by wet etching the surface of a glass substrate is advanced, and structural characteristics of the rough surface are analyzed. Then, spectral characteristics by changing the angle of the glass substrate to which light enters the company are analyzed. When the light entering the company is investigated on a etched surface, it is confirmed that the probability of re-absorbing the light inside the glass substrate by multiple reflection is increased. When entering the light while changing the angle of the glass substrate, the transmission and reflection performance of the light are not changed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.3
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• pp.311-317
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• 2019

We first numerically analyzed the characteristics of a silicon-based grating structure for beam steering. The analysis includes the basic principle of the grating structure according to the wavelength, peak radiation angle, radiation efficiency, and full-width at the half maximum(FWHM) of the radiation angle. Based on the analysis, we propose a silicon-based grating structure integrated with distributed Bragg reflector(DBR) to obtain a high radiation efficiency and narrow beam width simultaneously. We performed the numerical optimization of the radiation efficiency and FWHM of the radiation angle according to the DBR position. By the design optimization using the proposed grating structure compatible with the complementary metal-oxide semiconductor(CMOS) process, we achieved a maximum radiation efficiency of 87.1% and minimum FWHM of radiation angle of $4.68^{\circ}$.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.749-759
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• 2012

A field experiment was conducted to selection of ground-based remote sensor and reflectance indices to estimate rice production, estimation of suitable season for ground-based remote sensor and N top dressing fertilizer application rate in 2010. Fertilizer application was determined by "Fertilizer management standard for crops" (National Academy of Agricultural Science, 2006). Four levels of N-fertilizer were applied as 0%, 70%, 100% and 130% by base N-fertilizer application and were fertilized as 70% of basal dressing and 30% as top dressing. Rice (Oryza sativa L.) of Chucheong and Joonam (Korean cultivar) were planted on May 22, 2010 in sandy loam soil and harvested on October 6, 2010. Reflectance indices were measured 7 times from July 5 to August 23 by Crop circle-amber and red version and GreenSeeker-green and red version. Remote sensing angle from the sensor head to the canopy of rice was adjusted to $45^{\circ}$, $70^{\circ}$ and $90^{\circ}$ degree because of difference in the density of plant and the sensing angle. The reflectance indices obtained ground-based remote sensor were correlated with the biomass of rice at the early growth stage and at the harvest with $70^{\circ}$ and $90^{\circ}$ degree of sensor angle. The reflectance indices at the 52th Day After Transplanting (DAT) and the 59th DAT, critical season, were positively correlated with dry weight and nitrogen uptake. Specially NDVI at the 59th was significantly correlated with the mentioned parameters. Based on the result of this study, rNDVI by GreenSeeker on $70^{\circ}$ degree of angle at the 59th DAT in Chucheong and rNDVI by Crop Circle on $70^{\circ}$ degree of angle and gNDVI by GreenSeeker on $70^{\circ}$ degree of angle at the 59th DAT in Joonam can be useful for estimation of dry weight and nitrogen uptake. Moreover, sufficiency index estimated by reflectance index at the 59th DAT can be useful for the estimation of N-fertilizer level application and can be used as a model for N-top dressing fertilizer management.