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Tatsuo Shiina, Chiba University, Japan Inage coast at 20:25 in 24 th - - PowerPoint PPT Presentation
Tatsuo Shiina, Chiba University, Japan Inage coast at 20:25 in 24 th - - PowerPoint PPT Presentation
18-21th, June, 2018 CLRC 2018, OKINAWA, JAPAN Low Coherence Doppler Lidar with High-Power DFB-LD Tatsuo Shiina, Chiba University, Japan Inage coast at 20:25 in 24 th Sep. 2015. LED mini-lidar for sea wave motion monitoring at shallow angle
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Backgrounds
Current Doppler lidar Advantage Disadvantage Compact High-cost Maintenance free Blind area in near range Easy installation Low resolution Strong Demands Near range observation Follow the quick motion Low cost
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Low Coherence Doppler lidar
Purpose
Low Coherence Doppler Lidar Observation Range Off-set range = a few hundred m Coherence Length = Spatial Resolution ( < a few m ) Target Wind(Air cell) Speed 0.1 – 30 m/s
High-power Low Coherence DFB-LD
Current Coherence Doppler lidar
Reference path length can change the off-set distance
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High-Power DFB-LD
Low Coherence Doppler lidar Specification Observation Range = Off-set Range a few meter – a few hundred meter Output Power ＞ 1W Spatial Resolution a few meter Coherence Length 1m
Hamamatsu Photonics Model 976nm DFB-LD Wavelength 974nm Output power 2.7W [CW:max]@3A Spectral Width <14pm Coherence Length 0.1 m Specification of high-power DFB-LD
Output DFBLD
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- Current [A]
Spectral Width [nm]
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High-powered DFB-LD
Output Power Characteristics Coherence Length Characteristics Lidar Light Source Operation Forward Current 2A, Temperature 35℃ Optical Output Power 1.76W, Coherence Length 0.8m
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- Current [A]
Spectral Width [nm]
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Doppler Shift Observation
Fundamental setup of low coherence Doppler lidar
DFB-LD BS PD Target Rotation Speed 0.5 – 10 m/s
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Doppler Shift Observation
Heterodyne Detection Results Velocity estimation Deviation of velocity estimation +/-0.03 m/s
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Doppler Shift Observation
Diffuse Reflection Plate White Paper Deviation of velocity estimation +/-0.10 m/s
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Doppler Shift Observation
Compact Setup Target Flowing Mists Second setup of low coherence Doppler lidar
Wind Tunnel Fog Generator Fog
600mm x 450mm
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Doppler Shift Observation
Heterodyne Detection Results Wind Speed observation (Anemometer)
Average 0.72 m/s
Summation Wind Speed SNR 35s 0.64m/s (1.31MHz) 0.26dB
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Lidar Setup
Lidar setup Installation of Telescope Optical fiber interferometer Valance detector Third setup of low coherence Doppler lidar
90mmφ
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Doppler Shift Observation
Heterodyne Detection Results
0.7nW
Estimation of minimum detection = maximum distance of 360m
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Doppler Shift Observation
Heterodyne Detection Results
Change of reference optical fiber length = control of off-set distance 2m 6.5m
Ideally any distance can detect by switching the optical path length
Diffuse reflection plate
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