• 센서학회지
• /
• 제30권6호
• /
• pp.415-419
• /
• 2021

We developed a highly accurate, yet inexpensive, refractive index (RI)-based soil moisture sensor. To detect the RI, a light guide was set with a light-emitting diode and photodiode. When the air fills the space between the soil particles, most of the incident light is reflected at the interface between the waveguide and the air because of the large RI difference. As the moisture of the soil increases, the macroscopic soil RI increases. This allows incident light to pass through the interface. The intensity of the light reaching the photodiode was simulated according to the change in the soil RI. Using the simulation results, we designed and manufactured a curved glass waveguide. We evaluated the performance of the RI-based soil sensor by comparing it with a commercially available, high-cost and high-performance time-domain reflectometer (TDR). Our sensor was 96% accurate, surpassing the costly TDR sensor.

• Current Optics and Photonics
• /
• 제2권5호
• /
• pp.460-467
• /
• 2018

Three-dimensional (3D) refractive-index (RI) imaging and quantitative analyses of angiosperm pollen grains are presented. Using optical diffraction tomography, the 3D RI structures of individual angiosperm pollen grains were measured without using labeling or other preparation techniques. Various physical quantities including volume, surface area, exine volume, and sphericity were determined from the measured RI tomograms of pollen grains. Exine skeletons, the distinct internal structures of angiosperm pollen grains, were identified and systematically analyzed.

• 반도체디스플레이기술학회지
• /
• 제22권2호
• /
• pp.35-39
• /
• 2023

Silicon oxide thin films have been deposited by plasma-enhanced chemical vapor deposition in SiH4 and N2O plasma along the variation of the gas flow ratio. Optical emission spectroscopy was employed to monitor the plasma and ellipsometry was employed to obtain refractive index of the deposited thin film. The atomic ratio of Si, O, and N in the film was obtained using XPS depth profiling. Fourier Transform Infrared Spectroscopy was used to analyze structures of the films. RI decreased with the increase in N2O/SiH4 gas flow ratio. We noticed the increase in the Si-O-Si bond angles as the N2O/SiH4 gas flow ratio increased, according to the analysis of the Si-O-Si stretching peak between 950 and 1,150 cm-1 in the wavenumber. We observed a correlation between the optical emission intensity ratio of (ISi+ISiH)/IO. The OES intensity ratio is also related with the measured refractive index and chemical composition ratio of the deposited thin film. Therefore, we report the added value of OES data analysis from the plasma related to the thin film characteristics in the PECVD process.

• 한국산학기술학회논문지
• /
• 제21권6호
• /
• pp.411-416
• /
• 2020

본 연구는 적외선 광학재료의 중적외선 영역의 굴절률을 파악하기 위해 반사율을 측정하고 굴절률과 반사율의 관계로부터 굴절률을 추정하는 방법을 제안한다. 전반사 거울 4개를 일정한 간격으로 배열하고 적외선 광원으로부터 연속 파장의 평행광이 45°로 입사되도록 광 경로를 구성한다. 광 경로를 따라 4개의 전반사 거울에 반사되어 온 광강도 I_B를 측정한 후, 광 경로의 마지막에 놓이는 거울을 시편으로 교체하고 광강도 I_s를 측정한다. I_B와 I_s, 전반사 거울의 비를 이용하여 재료의 반사율을 계산한다. 계산된 반사율과 Fresnel의 굴절률과 반사율 관계식에 넣고 시행착오법으로 굴절률을 추정한다. 이 방법을 적용하여 사파이어(Al₂O₃), 게르마늄(Ge), 불화마그네슘(MgF₂), 황화아연(ZnS)재료를 대상으로 실험하고 굴절률을 추정하여 참고문헌자료들과의 비교를 통하여 모든 재료에 대해 파장범위 3 - 5㎛에서 최대 차이 2% 이하로 잘 일치하는 결과를 얻을 수 있었으며, 이를 통해 본 굴절률 측정방법의 타당성을 확인할 수 있다. 본 연구에서 제시된 방법은 연속 파장의 적외선 광원을 사용하기 때문에 한 번의 측정으로 여러 파장에 대한 굴절률을 추정 할 수 있는 장점이 있다.

• Mass Spectrometry Letters
• /
• 제12권3호
• /
• pp.81-84
• /
• 2021

Collagen, which accounts for one-third of human protein, is reduced due to human aging, and much attention is focused on making collagen into food to prevent such aging. Gel permeation chromatography with Reflective Index (RI) detection (GPC/RI) was chosen as the most suitable instrument to confirm molecular weight distribution, and we explored the use of this technique for analysis of collagen peptide molecular sizes and distributions. Data reliability was verified by matrix-assisted laser desorption/ionization coupled to time-of-flight (MALDI-TOF) mass spectrometric analysis. The data were considered meaningful for comparative analysis of molecular weight distribution patterns.

• 센서학회지
• /
• 제22권2호
• /
• pp.95-99
• /
• 2013

We proposed and demonstrated a fiber optic sensor for detecting the thermo-optic coefficient of a liquid, based on a cascade of two different FBGs. One of the two FBGs was etched, and its cladding was removed, for evanescent wave coupling with an external liquid. The Bragg wavelength of the non-etched FBG was used as a reference for the temperature of the surrounding liquid. The refractive index (RI) and thermo-optic (T-O) coefficient of a liquid can be detected from the difference between the Bragg wavelengths of the two FBGs, and the variation of the difference in accordance with temperature.

• 센서학회지
• /
• 제24권1호
• /
• pp.1-5
• /
• 2015

The V-grooved single-mode fiber in which a surface part of the core was removed was investigated as a quasi-distributed water detection sensor. In the normal state, the V-grooved region is filled and covered with a specific RI (Refractive Index)-matched medium, and the sensor experiences minimal optical loss. As water invades the V-grooved region, the material is dissolved and removed, and a considerable optical loss occurs owing to the large RI difference between the fiber core and water. The experimental results showed the feasibility of the device as a sensor element of the quasi-distributed water detection sensor system based on general optical time domain reflectometry (OTDR).

• Journal of Biosystems Engineering
• /
• 제34권1호
• /
• pp.50-56
• /
• 2009

Surface plasmon resonance (SPR) biosensor has been used to detect many biochemical reactions, because this label-free sensor has high sensitivity and rapid response. The reactions are monitored by refractive index changes of the SPR biosensor. Iprovalicarb is protective, curative, and eradicative systemic fungicide introduced by Bayer AG in 1999. It has potential far control of downy mildew infesting onion, cucumber, grape and melon, late blight infesting tomato and potato, and anthracnose infesting watermelon and pepper. It is strictly limited to the maximum residue limit. In this study, the applicability of a portable SPR biosensor (Spreeta, Texas instrument, TX, USA) to detect the iprovalicarb residue was examined. The sensor chip was adopted to detect the reaction of iprovalicarb to immobilized iprovalicarb-antibody. The binding of the iprovalicarb onto the biosensor surface was measured by change of the refractive index (RI). Characteristics of the sensor chip including specificity, sensitivity, stability, and reusability were analyzed. In calibration test for seven levels of iprovalicarb concentration (0.32 to 5,000 mg/L) with three replications, a Sigmoidal model with Hill function was obtained between relative RI value and the iprovalicarb concentration with R-square of 0.998. It took 30 minutes to complete a set of detecting assay with the SPR biosensor.

• Journal of Biosystems Engineering
• /
• 제36권1호
• /
• pp.23-32
• /
• 2011

In this work, the finite element method was used to investigate the shifts of resonance frequencies and quality factor of whispering-gallery-mode (WGM) for an opto-fluidic ring resonator (OFRR) biosensor. To describe the near-field radiation transfer, the time-domain Maxwell's equations were employed and solved by using the in-plane TE wave application mode of the COMSOL Multiphysics with RF module. The OFRR biosensor model under current study includes a glass capillary with a diameter of 100 mm and wall thickness of 3.0 mm. The resonance energy spectrum curves in the wavelength range from 1545 nm to 1560 nm were examined under different biosensing conditions. We mainly studied the sensitivity of resonance shifts affected by changes in the effective thickness of the sensor resonator ring with a 3.0 mm thick wall, as well as changes in the refractive index (RI) of the medium inside ring resonators with both 2.5 mm and 3.0 mm thick walls. In the bulk RI detection, a sensitivity of 23.1 nm/refractive index units (RIU) is achieved for a 2.5 mm thick ring. In small molecule detection, a sensitivity of 26.4 pm/nm is achieved with a maximum Q-factor of $6.3{\times}10^3$. These results compare favorably with those obtained by other researchers.

• 한국식품과학회지
• /
• 제22권2호
• /
• pp.162-167
• /
• 1990

RI 42, 43, 44, 45로 조정한 난황을 10% 가염처리 하여 이들을 $-15^{\circ}C$ 및 $-25^{\circ}C$에서 6개월간 냉동저장하며 점도, 유화력 변화를 측정하였다. 또, 이들 난황으로 마요네즈를 제조하여 점도, 입경, 유화 안정성을 측정하였다. 냉동저장 기간이 길수록 가염 난황의 점도는 점차 증가하였으며, 난백 혼입이 적을수록(RI가 클수록), $-15^{\circ}C$보다는 $-25^{\circ}C$에서 저장한 것이 저장중의 점도 증가가 큰 것으로 나타났으며, 유화력은 점차 감소하는 경향을 나타내었다. 난황의 법동저장 중, 이들 난황으로 제조한 마요네즈에 있어서 입경은 냉동저장 기간이 증가함에 따라 점차 작아졌으며, 점도는 저장기간 2개월까지는 감소하나 그 이후 증가하였다. 난백 혼입이 적을수록, $-15^{\circ}C$보다는 $-25^{\circ}C$에서 저장한 난황으로 만든 마요네즈가 입경이 더 작으며 점도는 높은 것으로 나타났다. 유화 안정성은 난황의 냉동저장 3-4개월까지 감소하여, 그 이후 증가하는 경향이었으며, RI 및 저장온도에 따른 차이는 인정되지 않았다.