• Korean Journal of Optics and Photonics
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• v.30 no.3
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• pp.114-119
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• 2019

This paper discusses the development of a Raman lidar system for remote detection and measurement of hydrogen gas by using a photon counter. The Raman signal of the hydrogen gas is very weak and has a very low signal-to-noise ratio. The photon counter has the advantage of improving the signal-to-noise ratio, because it has a discriminator to eliminate the background noise from the Raman signal of the hydrogen gas. Therefore, a small and portable Raman lidar system was developed using a low-power pulsed laser and a photon-counter system to measure the hydrogen gas concentration remotely. To verify the capability of measuring hydrogen gas using the developed photon-counting Raman lidar system, experiments were carried out using a gas chamber in which it is possible to adjust the hydrogen gas concentration. As a result, our photon-counting Raman lidar system is seen to measure a minimum concentration of 0.65 vol.% hydrogen gas at a distance of 10 m.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.208-209
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• 2000

라이다 방법을 이용한 대기의 온도 측정은 크게 1) DIAL 방법을 이용하는 방법 2) 공기분자의 밀도를 측정하는 진동 라만 산란을 이용하는 방법 3)공기분자의 회전 라만 산란을 이용하는 방법 4) Rayleigh 산란의 선폭을 이용하는 방법 등으로 나누어진다. 이 중에서 대류권의 온도 측정에 적용가능한 방법은 3 번째의 방법으로 질소나 산소의 회전 라만 산란(RRS:Rotational Raman Scattering)이 가장 흔히 사용되는 기술이다. 질소와 산소의 회전 라만 신호를 이용한 온도 측정 기술은 Cohen$^1$ 등에 의하여 처음 시도되었으며, 그 후 많은 사람들에 의하여 검증되었다.$^2$ (중략)

• Korean Journal of Optics and Photonics
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• v.35 no.2
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• pp.71-80
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• 2024

We developed a Raman lidar system for remote measurement of carbon dioxide present in atmospheric space. An air-cooled laser with 355-nm wavelength and a 6-inch optical receiver was used to miniaturize the Raman lidar system, and a scanning Raman lidar system was developed using a two-axis scanning device and a photon counter. To verify the performance of the developed Raman lidar system, a gas chamber capable of maintaining a concentration was located at a distance of about 87 m, and the change in Raman signal according to the change in the concentration of carbon dioxide was measured. As a result, it was confirmed that the change in the Raman scattering signal of carbon dioxide that appeared for a change in carbon dioxide concentration from about 0.67 to 40 vol% was linear, and the coefficient of determination (R²) value, which indicates the correlation between the carbon dioxide concentration and Raman scattering signal, showed a high linearity of 0.9999.

• Korean Journal of Optics and Photonics
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• v.28 no.3
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• pp.116-121
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• 2017

In this paper, a Raman spectrometer is designed to detect chemicals contaminating the ground. The system is based on Raman spectroscopy, which is spectral analysis of scattered light from chemicals, induced by a laser. The system consists of a transmitting-optics module with a laser to induce Raman-scattered light from the sample, a receiving-optics module to collect the scattered light, and a spectrograph to separate the collected light into a wavelength spectrum. The telescope, a part of the receiving-optics module, is designed to produce a focal spot in the same position for variable measurement distances using the code V simulator, considering the distance change between the system and the road. The Raman spectra of 12 chemicals on a glass surface and on a concrete sample were measured. Intensity differences between the Raman spectra acquired on a glass surface and on a concrete sample were observed, but the characteristics of the spectra according to the chemicals on them were similar. Additionally, the Raman spectrum of PTFE (polytetrafluoroethylene) was measured at various distances. The measured and simulated optical throughputs were similar. In conclusion, it is confirmed that with this system the Raman spectrum can be measured, irrespective of the distance change.

• Korean Journal of Optics and Photonics
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• v.28 no.4
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• pp.166-171
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• 2017

Hydrogen gas is a green energy sources because it features no emission of pollutants during combustion. But hydrogen gas is very dangerous, being flammable and very explosive. Hydrogen gas detection is very important for the safety of a nuclear power plant. Hydrogen gas is generated by oxidation of nuclear fuel cladding during a critical accident, and leads to serious secondary damage in the containment building. This paper discusses the development of a Raman lidar system for remote detection and measurement of hydrogen gas. A small, portable Raman lidar system was designed, and a measurement algorithm was developed to quantitatively measure hydrogen gas concentration. To verify the capability of measuring hydrogen gas with the developed Raman lidar system, experiments were carried out under daytime outdoor conditions by using a gas chamber that can adjust the hydrogen gas density. As results, our Raman lidar system is able to measure a minimum density of 0.67 vol. % hydrogen gas at a distance of 20 m.

• Korean Journal of Optics and Photonics
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• v.29 no.3
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• pp.119-125
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• 2018

Hydrogen gas is an important and promising energy resource that has no emissions of pollutants during power generation. However, hydrogen gas is very dangerous because it is colorless, odorless, highly flammable, and explosive at low concentration. Conventional techniques for hydrogen gas detection are very difficult for measuring the hydrogen gas distribution at long distances, because they sample the gas to measure its concentration. Raman lidar is one of the techniques for remotely detecting hydrogen gas and measuring the range of the hydrogen gas distribution. A Raman lidar system with an on-axis optical receiver was developed to improve the range of hydrogen gas detection at long distance. To verify the accuracy and improvement in the range of detecting the hydrogen gas, experiments measuring the hydrogen gas concentration are carried out using the developed on-axis Raman lidar system and a gas chamber, to prevent explosion of the hydrogen gas. As a result, our developed on-axis Raman lidar system can measure a minimum hydrogen gas concentration of 0.66 volume percent at a distance of 50 m.

• Korean Journal of Remote Sensing
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• v.35 no.6_3
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• pp.1187-1195
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• 2019

We, for the first time, developed a Raman lidar system which can remotely detect surface CO₂ volume mixing ratio (VMR). The Raman lidar system consists of the Nd: YAG laser of wavelength 355 nm with 80 mJ, an optical receiver, and detectors. Indoor CO₂ cell measurements show that the accuracy of the Raman lidar system is calculated to be 99.89%. We carried out the field measurement using our Raman lidar at Pukyong National University over a seven-day period in October 2019. The results show good agreement between CO₂ VMRs measured by the Raman lidar (CO₂ Raman Lidar) and those measured by in situ instruments (CO₂ In situ) which located 300 m and 350 m away from the Raman lidar system. The correlation coefficient (R), mean absolute error (MAE), and root mean square error (RMSE) between CO₂ In situ and CO₂ Raman Lidar are 0.67, 2.78 ppm, and 3.26 ppm, respectively.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.202-204
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• 2005

• Korean Journal of Optics and Photonics
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• v.22 no.6
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• pp.283-290
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• 2011

A Raman LIDAR system has been designed and constructed for quantitative measurement of water vapor mixing ratio. The comparison with commercial microwave radiometer and global navigation satellite system(GNSS) was performed for the precipitable water vapor(PWV) profile and total PWV. The result shows that the total GNSS-PWV and LIDAR-PWV have good correlation with each other. But, there is small difference between the two methods because of maximum measurement height in LIDAR and the GNSS method. There are some significant differences between Raman and MWR when the water vapor concentration changes quickly near the boundary layer or at the edge of a cloud. Finally we have decided that MWR cannot detect spatial changes but LIDAR can measure spatial changes.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.453-454
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• 2009