scholarly journals Atmospheric Aerosols Detection Research with a Dual Field of View Lidar

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Lv Lihui ◽  
Zhang Tianshu ◽  
Liu Cheng ◽  
Dong Yunsheng ◽  
Chen Zhenyi ◽  
...  
Keyword(s):  
Laser Beam ◽  
Atmospheric Aerosols ◽  
Near Field ◽  
Ccd Camera ◽  
Field Of View ◽  
Detection Accuracy ◽  
Aerosol Extinction ◽  
Lidar System ◽  
Field Range ◽  
Aerosol Extinction Coefficient

A dual field of view lidar system with two independent receivers is described to realize the detection of atmospheric aerosols. A CCD camera is attached to a backscatter lidar as a receiver to complement the data in the near-field range affected by the incomplete overlap between the laser beam and the receiver field of view. The signal detected by the CCD camera is corrected and finally glued with the signal of the backscatter lidar to retrieve the aerosol extinction coefficient with Fernald algorithm. The aerosol extinction profile and visibilities measured by the dual field of lidar had been compared with the results measured by another general backscatter lidar and a surface aerosol instrument, respectively. The results suggested that the dual field of view lidar based on a CCD camera is feasible and reliable. It could obtain the data both in the near and in the far range simultaneously, improving the detection accuracy of the lidar system effectively.

scholarly journals PROCESSING JUMP POINT OF LIDAR DETECTION DATA AND INVERSING THE AEROSOL EXTINCTION COEFFICIENT

2019 ◽  
Vol XLII-3/W9 ◽  
pp. 227-232
Author(s):  
H. L. Zhang ◽  
H. Zhao ◽  
Y. P. Liu ◽  
X. K. Wang ◽  
C. Shu
Keyword(s):  
Atmospheric Aerosols ◽  
Extinction Coefficient ◽  
Interpolation Method ◽  
Linear Interpolation ◽  
Mie Scattering ◽  
Inversion Method ◽  
Aerosol Extinction ◽  
Detection Range ◽  
Long Time ◽  
Aerosol Extinction Coefficient

Abstract. For a long time, the research of the optical properties of atmospheric aerosols has aroused a wide concern in the field of atmospheric and environmental. Many scholars commonly use the Klett method to invert the lidar return signal of Mie scattering. However, there are always some negative values in the detection data of lidar, which have no actual meaning，and which are jump points. The jump points are also called wild value points and abnormal points. The jump points are refered to the detecting points that are significantly different from the surrounding detection points, and which are not consistent with the actual situation. As a result, when the far end point is selected as the boundary value, the inversion error is too large to successfully invert the extinction coefficient profile. These negative points are jump points, which must be removed in the inversion process. In order to solve the problem, a method of processing jump points of detection data of lidar and the inversion method of aerosol extinction coefficient is proposed in this paper. In this method, when there are few jump points, the linear interpolation method is used to process the jump points. When the number of continuous jump points is large, the function fitting method is used to process the jump points. The feasibility and reliability of this method are verified by using actual lidar data. The results show that the extinction coefficient profile can be successfully inverted when different remote boundary values are chosen. The extinction coefficient profile inverted by this method is more continuous and smoother. The effective detection range of lidar is greatly increased using this method. The extinction coefficient profile is more realistic. The extinction coefficient profile inverted by this method is more favorable to further analysis of the properties of atmospheric aerosol. Therefore, this method has great practical application and popularization value.

scholarly journals Lidar Overlap Function Determination Using the Raman Lidar Signals

2020 ◽  
Vol 237 ◽  
pp. 07018
Author(s):  
Jaswant ◽  
Shishir Kumar Singh ◽  
Radhakrishnan S.R. ◽  
Devesh Shukla ◽  
Chhemendra Sharma
Keyword(s):  
Optical Properties ◽  
Simple Technique ◽  
Near Field ◽  
Lower Atmosphere ◽  
Raman Lidar ◽  
Lidar System ◽  
Field Range ◽  
The Mean ◽  
Overlap Factor

The determination of vertical distribution of optical properties of clouds and aerosols using the lidar system is affected by the incomplete overlap between the field of view of transmitter i.e. laser beam & the receiver in the near‐field range. Thus, the study of vertical profiles of aerosol optical properties in the lower atmosphere is erroneous without the correction of lidar overlap function. Here we have analysed the effect of overlap using a simple technique proposed by Ansmann and Wandinger to determine overlap function. We have determined the overlap factor for 5 different days of June 2016 and then calculated the mean overlap profile and determined the relative deviation of each day with respect to mean overlap factor. Results reveal that the complete overlap was achieved beyond 300 meters.

scholarly journals Polarization lidar for atmospheric monitoring

2018 ◽  
Vol 176 ◽  
pp. 05052
Author(s):  
Qiaojun Liu ◽  
Chengxuan Wu ◽  
Andrew Yuk Sun Cheng ◽  
Zhangjun Wang ◽  
Xiangqian Meng ◽  
...  
Keyword(s):  
Extinction Coefficient ◽  
Atmospheric Aerosol ◽  
Global Climate ◽  
Aerosol Extinction ◽  
Depolarization Ratio ◽  
Backscattering Coefficient ◽  
Lidar System ◽  
Weather Changes ◽  
And Inversion ◽  
Aerosol Extinction Coefficient

Aerosol plays an important role in global climate and weather changes. Polarization lidar captures parallel and perpendicular signals from atmosphere to research aerosols. The lidar system we used has three emission wavelengths and could obtain the atmospheric aerosol extinction coefficient, backscattering coefficient and depolarization ratio. In this paper, the design of the lidar is described. The methods of data acquisition and inversion are given. Some recent results are presented.

scholarly journals Feasibility Studies of the Three-Wavelength Mie-Scattering Polarization Scheimpflug Lidar Technique

2020 ◽  
Vol 237 ◽  
pp. 02013
Author(s):  
Zheng Kong ◽  
Teng Ma ◽  
Zhenfeng Gong ◽  
Kun Liu ◽  
Liang Mei
Keyword(s):  
Extinction Coefficient ◽  
Mie Scattering ◽  
Light Sources ◽  
Aerosol Extinction ◽  
Lidar System ◽  
Multimode Laser ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Aerosol Extinction Coefficient ◽  
Ångstrom Exponent

A three-wavelength Mie-scattering polarization Scheimpflug lidar system, utilizing 808-nm, 520-nm and 405-nm multimode laser diodes as light sources and two CMOS sensors as detectors, is developed for the studies of the aerosol extinction coefficient, depolarization ratio and the Ångström exponent. Atmospheric monitoring has been carried out on a near horizontal path from 23:00 January 14th to 06:00 January 15th, 2019 at Dalian, which is a coast city in Northern China. By studying the depolarization, aerosol extinction coefficient and Ångström exponent, it has been found out that a strong north wind blew away local spherical haze particles and brought external non-spherical large-size particles. The measurement results indicated a promising future of employing the present three-wavelength polarization Scheimpflug lidar system in the applications of atmospheric remote sensing.

Electron holography of p-n junctions

1996 ◽  
Vol 54 ◽  
pp. 974-975
Author(s):  
B.G. Frost ◽  
D.C. Joy ◽  
L.F. Allard ◽  
E. Voelkl
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Field Emission ◽  
Ccd Camera ◽  
Image Plane ◽  
Reference Wave ◽  
Field Of View ◽  
Control Mode ◽  
Objective Lens ◽  
Electron Holography

A wide holographic field of view (up to 15 μm in the Hitachi-HF2000) is achieved in a TEM by switching off the objective lens and imaging the sample by the first intermediate lens. Fig.1 shows the corresponding ray diagram for low magnification image plane off-axis holography. A coherent electron beam modulated by the sample in its amplitude and its phase is superimposed on a plane reference wave by a negatively biased Möllenstedt-type biprism.Our holograms are acquired utilizing a Hitachi HF-2000 field emission electron microscope at 200 kV. Essential for holography are a field emission gun and an electron biprism. At low magnification, the excitation of each lens must be appropriately adjusted by the free lens control mode of the microscope. The holograms are acquired by a 1024 by 1024 slow-scan CCD-camera and processed by the “Holoworks” software. The hologram fringes indicate positively and negatively charged areas in a sample by the direction of the fringe bending (Fig.2).

Study and Realization of Camera Wafer Image Fusion Algorithm

2014 ◽  
Vol 484-485 ◽  
pp. 540-546
Author(s):  
Yi Xu
Keyword(s):  
Image Fusion ◽  
Ccd Camera ◽  
Inspection System ◽  
Defect Inspection ◽  
Fusion Algorithm ◽  
Field Range ◽  
Mosaic Image

Image mosaics not only can make the collected several original images regenerate a complete image, but also can correct the error caused by imaging distortion of the original images, which can achieve the objective of rapid and correct mosaic image. The program studies the image mosaics of wafer defect inspection system. For the problem that the field range taken by CCD camera under resolution of wafer defect inspection system is small, which cant get the whole wafer image once and influences the extraction of subsequent defect features, the study demands to add image mosaics to the system.

Sign in / Sign up

Export Citation Format

Share Document