• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.134-139
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• 1989

레이저 도플러 효과를 써서 유체 또는 작은 입자의 속도를 잴수 있는 레이저 도플러 속도측정 장치를 만들었다. 광학계는 레이저 광속을 두 갈래로 나누어 다시 마주치게 하여 두 광속이 겹치는 곳에, 평행한 삼차원 간섭무늬가 생기도록 꾸몄다. 분무기로 작은 물방울을 만들어 두 광속이 겹치는 곳을 지나게 했더니 도플러 신호를 얻을 수 있었다.

• Progress in Medical Physics
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• v.5 no.1
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• pp.25-39
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• 1994

To measure the velocity of heart wall and local flow transctaneously in blood vessels, we have developed a single channel 3.1 MHz pulsed ultrasonic Doppler velocity meter. Ultrasound pluse width and repetition frequency (PRF) used in the velocity meter is 1 ${\mu}$sec 6kHz reapectively, and the Doppler shift of the backscattered echo signal is sensed in a phase detector by coherent demodulation method. From the output of the phase detector, the Doppler signal corresponding to the mean velocity of acoustic wave scatterers over a small region is obtained by using a range gate, sample holder and band-pass filter. Mean frequency of Doppler signal is estimated by zero-crossing counter and the instantaneous velocity of scatters is displayed as a function of time. It is possible to estimate velocity profile, volume flow and flow acceleration of vessels in man if the number of channels and range resolution in increased.

• 전기의세계
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• v.50 no.1
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• pp.11-16
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• 2001

• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.157-161
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• 1996

A simple laser Doppler velocimeter(LDV) using a $CO_2$ laser with its self-mixing effect has been developed. We measured the laser power which was modulated by Doppler frequency, when monochromatic laser light was focused to a moving target. The Doppler-shifted frequency was controlled by changing rotating speed of the turntable or the cosine of the angle between the direction of the laser beam and that of the rotating velocity.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.482-485
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• 1997

A new laser Doppler velocimeter employing a $CO_2$laser has been developed by using its optogalvanic effect. A change in the electric impedance of a discharge, induced by mixing of a returned wave with an originally existing wave inside the cavity, was employed to detect the Doppler frequency shift. A Doppler frequency shift as much as 60 KHz was detected, and also a good linear relationship between the velocity and the Doppler frequency shift was obtained.

• Korean Journal of Optics and Photonics
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• v.11 no.4
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• pp.250-254
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• 2000

We have constructed laser Doppler velocimetry system using self-mixing effect with a semiconductor laser. This technology is based on the frequency mixing phenomena which occurs when light scattered back from the moving object into the laser cavity interferes with light inside the laser. We have compared the value of Doppler shifted frequency with the velocity variation of the wheel. Frequency dependence on the angle between the moving direction of rotating aluminum wheel and the incident beam also have been proved. As an illustration of the performance of the velocimeter, velocity measurements of a rotating disk are described. Doppler signal shows a good linear relationship with velocity of rotating disk.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.367-371
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• 2005

본 논문에서는 수리실험을 통해 개수로의 바닥 조건에 따른 평균흐름 및 난류구조, 그리고 고유구조의 특성을 연구하였다. 레이저 도플러 유속계를 이용하여 2차원 순간속도를 측정하였다. 측정된 평균유속, 레이놀즈응력, 난류강도, 와점성계수, 혼합 길이 등의 난류량을 기존에 제시된 경험식과 비교하였으며 기존 연구 결과와 유사함을 확인하였다. 사분면 기법을 이용하여 개수로 흐름의 고유구조를 살펴본 결과, 분출 및 쓸기 현상의 발생 확률이 다른 상호작용에 비해 지배적임을 확인하였다. 고속 푸리에 변환을 통한 스펙트럼 분석을 통하여 에너지 폭포 현상 및 난류 와의 미시 및 거시 특성크기를 파악하였다.

• Korean Journal of Remote Sensing
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• v.29 no.1
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• pp.11-20
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• 2013

Space-borne Synthetic Aperture Radar(SAR) has been one of the most effective tools for monitoring quantitative oceanographic physical parameters. The Doppler information recorded in single-channel SAR raw data can be useful in estimating moving velocity of water mass in ocean. The Doppler shift is caused by the relative motion between SAR sensor and the water mass of ocean surface. Thus, the moving velocity can be extracted by measuring the Doppler anomaly between extracted Doppler centroid and predicted Doppler centroid. The predicted Doppler centroid, defined as the Doppler centroid assuming that the target is not moving, is calculated based on the geometric parameters of a satellite, such as the satellite's orbit, look angle, and attitude with regard to the rotating Earth. While the estimated Doppler shift, corresponding to the actual Doppler centroid in the situation of real SAR data acquisition, can be extracted directly from raw SAR signal data, which usually calculated by applying the Average Cross Correlation Coefficient(ACCC). The moving velocity was further refined to obtain ocean surface current by subtracting the phase velocity of Bragg-resonant capillary waves. These methods were applied to Envisat ASAR raw data acquired in the East Sea, and the extracted ocean surface currents were compared with the current measured by HF-radar.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.12
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• pp.1111-1118
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• 2010

Combustion measurements based on optical techniques have recently become of major interest as tools not only for clarifying the combustion mechanism but also for validating the computational results for the combustion fields. In this study, the particle behavior in turbulent pulverized coal flame are investigated using advanced optical diagnostics. A laboratory-scale pulverized coal combustion burner is specially fabricated as open type in order to apply various optical measurement techniques. The detailed particle behavior is performed by LDV (laser Doppler velocimetry) and SDPA (shadow Doppler particle analyzer). It is observed that the particle mean diameter increase as the distance from burner increases, and this is found to be caused by the decrease of small particles' diameter and increase of large particles' diameter. This is because of result in the char reaction and the particle swelling due to devolatilization, respectively. The size-classified streamwise velocities of pulverized coal particles in the central region of the jet show the same magnitude, whereas those in the outer region are different depending on the particle size. The results show that the velocity and size-classified diameter of the pulverized coal particles in the flame can be measured well by SDPA.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.226-227
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• 2000

Laser Doppler velocimeters: (LDV)$^{1)}$ 의 대부분의 기본원리는 호모다인(honodyne)방법을 사용한다. 호모다인 방법 중에서 많이 사용되는 방법으로는 마이켈슨 간섭계식과 되먹임식(self-mixing type)$^{2)}$ 이 있다. 마이켈슨 간섭계식은 구성하는데는 많은 광학부품과 정밀한 정렬 장치들을 필요로 한다. 반면에 되먹임식은 레이저 공진기의 고유 주파수와 도플러 이동된 산란광을 공진기 속에서 자체 혼합하여 발생한 차주파수를 레이저 공진기 내부에 있는 pin-photodiode로 측정하므로 마이켈슨 간섭계에 비하여 간단한 장치로 속도계를 구성할 수 있다. (중략)