Infrared Light Absorbance: a New Method for Temperature Compensation in Nondispersive Infrared CO2 Gas Sensor

( Seung Hwan Yi ) 한국센서학회 2020 센서학회지 Vol.29 No.5

Nondispersive infrared CO₂ gas sensor was developed after the simulation of optical cavity structure and assembling the optical components: IR source, concave reflectors, Fresnel lens, a hollow disk, and IR detectors. By placing a hollow disk in front of reference IR detector, the output voltages are almost constant value, near to 70.2 mV. The absorbance of IR light, F_a, shows the second order of polynomial according to ambient temperatures at 1,500 ppm. The differential output voltages and the absorbance of IR light give a higher accuracy in estimations of CO₂ concentrations with less than ± 1.5 % errors. After implementing the parameters that are dependent upon the ambient temperatures in microcontroller unit (MCU), the measured CO₂ concentrations show high accuracies (less than ± 1.0 %) from 281 K to 308 K and the time constant of developed sensor is about 58 sec at 301 K. Even though the estimation errors are relatively high at low concentration, the developed sensor is competitive to the commercial product with a high accuracy and the stability.

Morphological design of optical cavities for frequency-selective black absorbers

김다솜,조진우,박금환,김영석,김선경 한국물리학회 2017 Current Applied Physics Vol.17 No.8

We study various morphological effects due to optical cavities that are formed into metal substrates for the implementation of frequency-selective black absorbers. The absorption spectra (l ¼ 500e3000 nm) of patterned metal substrates are investigated by conducting full-vectorial electromagnetic simulations. The diameter of optical cavities determines a cut-off wavelength at which absorption begins to drop off exponentially. The cut-off wavelength is gradually redshifted by increasing the diameter of the optical cavities, which is associated with the tuning of the fundamental transverse mode. The height of optical cavities determines the number and amplitude of absorption peaks, which originate from Fabry-Perot modes with different longitudinal orders. Also, the absorption features depend strongly on the refractive index of the material within optical cavities; optical cavities filled with a dielectric yield improved absorption, even with a relatively shallow height. With an integration of patterned tantalum (Ta) and tungsten (W) thermal emitters, the power conversion efficiencies of thermophotovoltaics are predicted, accounting a body temperature of 1300 K and the quantum efficiency of a typical infrared photovoltaic cell. Tailored optical cavities lead to a dramatic enhancement in the power conversion efficiency up to 11.6 and 2.1 fold compared to planar structures, for Ta and W thermal emitters, respectively. These numerical findings and underlying physics will provide valuable design strategies to thermal radiation engineered applications such as solar absorbers, radiative coolers, as well as thermophotovoltaics.

Morphological design of optical cavities for frequency-selective black absorbers

Kim, D.S.,Cho, J.W.,Park, K.,Kim, Y.S.,Kim, S.K. Elsevier 2017 Current Applied Physics Vol.17 No.8

<P>We study various morphological effects due to optical cavities that are formed into metal substrates for the implementation of frequency-selective black absorbers. The absorption spectra (lambda = 500-3000 nm) of patterned metal substrates are investigated by conducting full-vectorial electromagnetic simulations. The diameter of optical cavities determines a cut-off wavelength at which absorption begins to drop off exponentially. The cut-off wavelength is gradually redshifted by increasing the diameter of the optical cavities, which is associated with the tuning of the fundamental transverse mode. The height of optical cavities determines the number and amplitude of absorption peaks, which originate from Fabry-Perot modes with different longitudinal orders. Also, the absorption features depend strongly on the refractive index of the material within optical cavities; optical cavities filled with a dielectric yield improved absorption, even with a relatively shallow height. With an integration of patterned tantalum (Ta) and tungsten (W) thermal emitters, the power conversion efficiencies of thermophotovoltaics are predicted, accounting a body temperature of 1300 K and the quantum efficiency of a typical infrared photovoltaic cell. Tailored optical cavities lead to a dramatic enhancement in the power conversion efficiency up to 11.6 and 2.1 fold compared to planar structures, for Ta and.,W thermal emitters, respectively. These numerical findings and underlying physics will provide valuable design strategies to thermal radiation engineered applications such as solar absorbers, radiative coolers, as well as thermophotovoltaics. (C) 2017 Elsevier B.V. All rights reserved.</P>

금 나노입자의 크기에 따른 광학적 특성변화

입팔 유샤프,이일수,배홍섭,김정수,장준혁,권문호,홍성욱 한국물리학회 2014 새물리 Vol.64 No.3

Three different-sized gold nanoparticles were synthesized to investigate the size dependence of the optical absorbance in aqueous solutions of nanoparticles. The particles were spherical in shape on the TEM images and had average diameters of 14.49 ± 1.12 nm, 16.11 ± 1.32 nm, 24.77 ± 1.76 nm, respectively. The resonance wavelength of the surface plasma was red-shifted in the UV-VIS spectra with increasing diameter of the particles. The spectra also showed that the optical absorbance increased as the particle size increased, which is as expected. Also, the concentration dependence of the absorbance showed that the absorbance increased with increasing particles size. 금 나노입자 수용액에서 광학적 특성이 입자의 크기에 따라 어떻게 변하는지를 관찰하기 위해 크기가 다른 금 나노입자를 형성하였다. TEM (투과전자현미경)으로 관찰한 금 나노입자의 모양은 구형이고 그 직경은 각각 14.49 ± 1.12 nm, 16.11 ± 1.32 nm, 24.77± 1.76 nm이었다. UV-VIS(적외선-가시광선) 스펙트럼에서 표면 플라즈마 공명의 파장은 입자의 크기가 증가함에 따라 적색편이 됨이 관찰되었다. 또한 흡수력 (absorbance)도 입자의 크기가 증가함에 따라 증가함이 관찰되었다. 나노입자의 농도에 따른 흡수력의 변화를 관찰하기 위해 여러 농도의 나노입자 수용액을 만들었다. UV-VIS 스펙트럼을 통해 농도가 커짐에 따라 흡수력의 피크는 증가함이 관찰되었고, 이 피크의 증가는 입자의 크기에 비례함을 볼 수 있었다.

메타표면 기반 평면 광학 부품: 홀로그램, 완전흡수체 및 소용돌이 빔 생성 메타렌즈

김인기(Inki Kim),정헌영(Heonyeong Jeong),노준석(Junsuk Rho) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12

Metasurfaces, two dimensional (2D) metamaterials comprised of subwavelength features, can be used to tailor the amplitude, phase and polarization of an incident electromagnetic wave propagating at an interface. The planar and surface-based optical components enabled by metasurfaces are believed to be a promising technology to replace or supplement existing bulk optical components. In this work, we demonstrate three distinctive flat optical components, which are meta-hologram, perfect absorber and vortex beam generating metasurfaces. From the point of practical use of the metasurfaces, we develop functionalized flat optical components. In detail, our meta-hologram can generate vivid holographic images under unpolarized natural light (e.g. sunlight, flash light of cellphone). For the case of perfect absorber composed of chromium ring-shaped structures, they can absorber over 96% visible light with high heat resistance, which can endure 600˚C temperature. Finally, we propose polarization-insensitive multifunctional metasurfaces for generating highly focused optical vortex beam at a desired focal point.

복수 개의 광파장에 대한 상대적 흡광 특성을 이용한 글루코스 농도 측정

김기도,손근식,임성수,이상신,Kim, Ki-Do,Son, Geun-Sik,Lim, Seong-Soo,Lee, Sang-Shin 한국광학회 2008 한국광학회지 Vol.19 No.6

본 논문에서는 복수 개의 측정 광파장 대역에서의 글루코스 수용액의 상대적인 흡광 특성을 이용한 글루코스 농도 예측 방법을 제안하고 검증하였다. 각 측정 파장에서의 상대적인 흡광도는 기준 파장에서의 흡광도를 기준하여 얻어진다. 선정된 기준 파장(1310 nm)과 네 개의 측정 파장(1064, 1550, 1685, 1798 nm) 대역에서는 글루코스에 대한 흡광도가 서로 반대의 부호를 갖도록 하였으며, 이 특성은 측정 정확도를 높이는데 도움이 된다. 최종적인 글루코스 수용액의 예측 농도는 각 측정 파장에서 얻어진 예측 값의 평균으로 결정된다. 5 mm의 광경로와 $0{\sim}1000mg/dL$ 농도 범위에서 실제로 측정된 글루코스의 흡광도를 살펴보면, 기준 파장 1310 nm에서는 $-1.42{\times}10^{-6}\;AU$/(mg/dL), 측정 파장 1685 nm에서는 $+8.12{\times}10^{-6}\;AU$/(mg/dL)로 최대였다. 그리고 제안된 방법을 이용하여 글루코스 용액의 농도를 예측할 경우 얻어진 표준예측오차(SEP: standard error of prediction)는 ${\sim}28\;mg/dL$였다. 또한, 온도와 지방층이 글루코스 농도 측정에 미치는 영향을 조사하였다. 먼저 $26{\sim}40^{\circ}C$ 온도 범위에서 측정된 흡수량 변화율은 기준 파장 1310 nm에서 $-9.1{\times}10^{-5}\;AU/^{\circ}C$였고, 측정 파장 1550 nm에서 $-2.08{\times}10^{-2}\;AU/^{\circ}C$였다. 그리고 글루코스 수용액에 존재하는 지방층 두께에 따른 흡수량 변화율은 1685 nm 파장 대역에서 +1.093 AU/mm로 측정되었다. A scheme for predicting the concentration of a glucose solution based on its relative optical absorbance at multiple probe wavelengths was proposed and verified. The relative absorbance at each of the probe wavelength was obtained with respect to the absorbance at a reference wavelength. The single reference wavelength (1310 nm) and a group of four different probe wavelengths (1064, 1550, 1685, 1798 nm) were selected to exhibit the glucose absorbance with opposite signs, thereby enhancing the accuracy of the prediction. The final glucose concentration was estimated by taking the average of the predicted values provided by the four probe wavelengths. The absorbance of the glucose solution for the path length of 5 mm was $-1.42{\times}10^{-6}\;AU$/(mg/dL) at the reference wavelength of 1310 nm and peaked at $+8.12{\times}10^{-6}\;AU$/(mg/dL) at 1685 nm. The concentration of the glucose solution was decently predicted by means of the proposed scheme with the standard error of prediction of ${\sim}28\;mg/dL$. In addition, the influence of the ambient temperature and the fat thickness upon the prediction of the glucose concentration was examined. The absorption change with the temperature was $-9.1{\times}10^{-5}\;AU/^{\circ}C$ in the temperature range of $26{\sim}40^{\circ}C$ at the reference wavelength, and $-2.08{\times}10^{-2}\;AU/^{\circ}C$ at 1550 nm. And the absorption change with respect to the fat thickness was +1.093 AU/mm at the probe wavelength of 1685 nm.

전이금속원소들이 첨가된 나노 티타니아 졸 및 코팅막 제조

이강,이남희,신승한,이희균,김선재,Lee K.,Lee N. H.,Shin S. H.,Lee H. G.,Kim S. J. 한국재료학회 2004 한국재료학회지 Vol.14 No.9

The photocatalytic performance of $TiO_2$ thin films coated on porous alumina balls using various aqueous $TiOCl_2$ solutions as starting precursors, to which 1.0 $mol\%$ transition metal ($Ni^{2+},\;Cr^{3+},\;Fe^{3+},\;Nb^{3+},\;and\;V^{5+}$) chlorides had been already added, has been investigated, together with characterizations for $TiO_2$ sols synthesized simultaneously in the same autoclave through hydrothermal method. The synthesized $TiO_2$ sols were all formed with an anatase phase, and their particle size was between several nm and 30 nm showing ${\zeta}-potential$ of $-25{\sim}-35$ mV, being maintained stable for over 6 months. However, the $TiO_2$ sol added with Cr had a much lower value of -potential and larger particle sizes. The coated $TiO_2$ thin films had almost the same shape and size as those of the sol. The pure $TiO_2$ sol showed the highest optical absorption in the ultraviolet light region, and other $TiO_2$ sols containing $Cr^{3+},\;Fe^{3+}\;and\;Ni^{2+}$ showed higher optical absorption than pure sol in the visible light region. According to the experiments for removal of a gas-phase benzene, the pure $TiO_2$ film showed the highest photo dissociation rate in the ultraviolet light region, but in artificial sunlight the photo dissociation rate of $TiO_2$ coated films containing $Cr^{3+},\;Fe^{3+}\;and\;Ni^{2+}$ was measured higher together with the increase of optical absorption by doping.

회전축 정렬불량 광디스크 드라이브의 진동 저감에 관한 연구

강봉진(Bong Jin Kang),정태은(Tae Eun Chung),신효철(Hyo Chol Sin),오주환(Ju Hwan Oh) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.5

In a high-speed and wide operating field optical disk drive, the vibration problem is one of the most important factors to be considered for reliable performance. And a disk misaligned with axis of rotation is a major source of vibration in optical disk drive. Furthermore, this vibration disturbance of the disk spindle system causes failure in the reading and writing process. So to solve this vibration problem, the vibration absorber using rubber mount has been introduced in recent years. In this paper, we have analyzed the simple optical disk drive model with dynamic vibration absorber through dynamic analysis of 12-dof by Recurdyn program and obtained optimal mass and frequency ratios of dynamic vibration absorber of dynamic vibration absorber and the optimal frequency ratio.

투명 전도성 코팅체의 전자기적, 광학적 성능 설계 및 분석에 관한 연구

조성실,윤영준,황민제,홍익표 한국군사과학기술학회 2024 한국군사과학기술학회지 Vol.27 No.1

. In order to avoid the high observability due to the cavity resonance or electromagnetic wave leakages from the bridge of a battleship or the cockpit of an aircraft, this paper presents a transparent conductive oxide coated structure to prevent the incoming/outgoing electromagnetic waves. Currently, most of the RCS reduction technologies were focused on radar absorbing material such as paints based on conductive or magnetic materials in the fuselage, and there is not much research on countermeasures for achieving the low observability of materials that required optical transparency in actual weapon systems. In this study, the transmission/reflection and absorption performance of the ITO coated structure according to the change of the surface resistance of the transparent conductor were analyzed. Finally, the relationship between the electromagnetic and optical characteristics was established through fabrication and measurement.

뉴트럴레드가 고정화된 다공성 졸-겔 필름을 이용한 고감도 광섬유 pH 센서의 특성

전다영 ( Da Yeong Jeon ),유욱재 ( Wook Jae Yoo ),신상훈 ( Sang Hun Shin ),한기택 ( Ki Tek Han ),박장연 ( Jang Yeon Park ),박병기 ( Byung Gi Park ),조승현 ( Seung Hyun Cho ),이봉수 ( Bong Soo Lee ) 한국센서학회 2012 센서학회지 Vol.21 No.3

In this study, a fiber-optic pH sensor based on a pH sol-gel film is fabricated. The sol-gel film is made by co-polymerizing tetramethoxysilane, trimethoxymethylsilane, ethanol and distilled water. As a pH indicator, a neutral red is immobilized in a thin porous film formed by the sol-gel process. The pH change in a sensing probe gives rise to a change in the color of the pH sol-gel film, and the absorbance of reflected light through the pH sol-gel film is also changed. By using a spectrometer, therefore, the spectra of reflected lights in the sensing probe with different pH values are measured. Also, the relationships between the pH values and the absorbance are analyzed on the basis of the color variations of the pH sol-gel films. In repeated experiments, the fiber-optic pH sensor shows that it has reversibility, a high reproducibility and a wide absorbance change in a pH range from pH 5 to 9. Also, we confirmed that the fabricated pH sol-gel film exhibits a fast response time, little or no pH indicator leaching and a dynamic range of 2.04 dB from pH 5 to 9. Based on the results of this study, a fiber-optic pH sensor can be developed for the pH monitoring in the harsh environments.