The Transport of Intensity Equation (TIE) offers an effective method for wavefront sensing,utilizing the variations in near-field defocused intensity distribution patterns across multiple propagation distances to reconstruct the phase aberrations introduced by turbulent media,such as the atmosphere. YANG Huizhe et al have explored TIE-based wavefront sensing for satellite-ground laser communication systems,addressing challenges related to the Point-Ahead Angle (PAA). Their simulations and bench experiments,using a Zernike-based linear reconstruction method,demonstrated effectiveness under high Signal-to-Noise Ratio (SNR) conditions. However,linear wavefront reconstruction faces significant nonlinear errors,rendering it ineffective in low SNR environments,which are common in low laser power scenarios typical of laser communication systems.To address these challenges,this paper proposes a Deep Neural Network (DNN) training model. The model utilizes the differences in intensity distributions observed at two distinct propagation distances as the input data. The outputs of the model are the first 4 to 79 orders of the Zernike coefficients corresponding to the phase aberrations. The input and output data used for DNN training are simulated through two processes based on the actual satellite-ground laser communication systems. The first process is the uplink propagation of a collimated laser beam through the atmospheric turbulence,while the second process is the reimaging of the backscattered patterns from these different altitudes. To generate a diverse set of datasets,three variable parameter sets are employed: the atmospheric coherence lengths of 0.05,0.10,and 0.15 meters; the turbulence layer heights of 0,5,and 10 kilometers; and the laser powers of 5,10,20,50,100,200,and 300 watts. This results in 63 unique combinations. Each combination contains 10,000 random phase screens,yielding a total of 630,000 training data. By comparing the Wavefront Errors (WFE) between the original and reconstructed phases,different model architectures,loss functions,and optimizers are evaluated. Ultimately,ResNet34 is chosen as the backbone network. A linear weight pooling method is proposed for the neck network,along with the Weighted Mean Absolute Error (WMAE) function and the SophiaG optimizer.Simulation results provide compelling evidence that the DNN approach significantly outperforms the traditional linear reconstruction methods. Notably,it substantially reduces the laser power requirements essential for effective wavefront sensing. For instance,at a laser power level of 5 W,the reconstruction accuracy achieved by the DNN model matches that of linear methods operating at a substantially higher power of 200 W. Furthermore,as the laser power exceeds 20 W,the detection error for the DNN approach stabilizes at approximately 200 nm RMS,reaching the accuracy limits of the 79th order Zernike polynomial. Moreover,the execution time is also a crucial indicator of its practicality,especially in real-time adaptive optics systems. Testing one thousand datasets on a single PC with an NVIDIA A 5 000 GPU yielded a total processing time of 0.52 seconds for the DNN,resulting in an average processing time of approximately 0.52 milliseconds per dataset,thereby meeting the real-time requirements of adaptive optics systems with a KHz sampling frequency. In contrast,under the same hardware conditions the linear reconstruction method needs approximately 27.31 milliseconds per dataset. The DNN method is about 52 times faster than the linear reconstruction method,highlighting the significant advantages of DNNs in practical applications.Although the DNN method demonstrates excellent performance in wavefront sensing accuracy and execution efficiency,it still has some shortcomings. First,the reliance on training data is a common issue for DNNs. The performance of DNNs is highly dependent on the quality and diversity of the training data. If the actual turbulent conditions differ significantly from the training data,the model's performance can decline sharply. Therefore,it is necessary to further enhance the diversity of the training data to cover a broader range of turbulent conditions and noise levels. Second,the model's interpretability is limited. DNNs are often regarded as black boxes,making their internal decision-making processes difficult to explain using physical laws. In this paper,we designed the linear weight pooling and a weighted mean absolute error loss function based on the physical context of the task. However,further efforts are required to integrate DNNs with the physical models to improve the model's interpretability and robustness.

Underwater imaging plays an increasingly important role in marine military, marine engineering, marine resource development,marine environmental protection, and so on, with the advantage of providing rich information, high resolution and high visibility underwater images. However, a large number of plankton and suspended particles in water environment, especially in the marine environment, causing strong scattering and absorption effects and resulting in image degradation problems such as blurring, short imaging distance, color distortion, low contrast, etc. Therefore, a series of underwater imaging methods have been proposed to solve the above problems.The underwater image enhancement technology can be used for image denoising, contrastimprovement and color distortioncorrection. The underwater image restoration uses the physical model of water degradation to restore the real image. The underwater polarization imaging uses the polarization difference between background and target to remove noise. The underwater ghost imaging and underwater compressed sensing imaging are used for imaging in scattering media. The underwater spectral imaging is used for color restoration. The underwater laser imaging is used for long-range and three-dimensional imaging. The underwater holographic imaging is used for water microorganism imaging, and so on. However, the above methods can only solve some image degradation problems, and there are some drawbacks, such as the subjectivity of underwater image enhancement technology, the dependence of underwater image recovery technology on prior information, and the computational load of underwater image correlation.The development of deep learning together with the development of hardware technology provides new solutions to the above problems, which makes the combination of deep learning and underwater imaging technology more and more widely used. As a powerful tool, neural network can extract similar features of different images using a wide range of datasets and convert them into high-level features, which can be used to process new input data, and completes a variety of complex tasks implicitly. It performs excellently in the field of image processing, and has made some achievements in the application of underwater imaging.Deep learning-basedimage restoration uses neural network to establish image-parameter mapping to estimate model parameters, avoiding human-dominant influence. Deep learning-based polarization imaging uses a neural network to map polarized images to clear images for image denoising. Deep learning-based spectral underwater imaging technology uses neural network to fuse multispectral images and hyperspectral images to obtain images with both high spatial resolution and hyperspectral resolution. However, some problems such as lack of datasets, poor generalization, and insufficient network interpretabilitystill exist, which need to be further solved.In this review, we discuss the characteristics of water environment and the various problems existing in underwater imaging, such as image blurring, short imaging distance, severe color distortion, and so on. The causes of the problem are analyzed and the underwater IFM model proposed by Jaffe-McGlamey is introduced. The latest application progress of various classic underwater imaging methods is systematically reviewed, including underwater image enhancement, underwater image restoration, underwater polarization imaging, underwater correlation imaging, underwater spectral imaging, underwater compression sensing imaging, underwater laser imaging and underwater holographic imaging. In addition, the basic concepts of deep learning, the composition of neural network and the structure of classical CNN network are introduced, and the latest application in combination with the above underwater imaging technology is systematically reviewed. At the same time, the application characteristics, deficiencies of traditional underwater imaging and the improvement by deep learning are analyzed and compared, and the applications of deep learning in various imaging methods are summarized. CNN network structure and MSE loss function are most commonly used due to its simplicity and efficiency. Finally, the future direction of underwater imaging technology based on deep learning is prospected.

In response to the measurement requirements of turbulence in the study of cloud precipitation physics， a turbulence parameter characterization method based on digital holographic interferometry to measure the microphysical fluctuation of liquid cloud is proposed. Since there is no need to assume the distribution function of the cloud droplet spectrum and adjust related parameters， digital holographic interferometry can obtain the microphysical fluctuations of the liquid phase cloud affected by the actual turbulence. The fog droplets affected by steady turbulence are used to simulate liquid phase cloud droplets， and the droplet spectrum is recorded by a camera with a pixel size of 1.67 μm， and then the fluctuations of the water content and the average radius of the droplets are obtained. According to the theory of turbulence， the variance， time correlation coefficient， covariance and cross-correlation coefficient of turbulence are obtained. Finally， by analyzing the time correlation coefficients of water content at different intervals， the time scale of the turbulent field is 100 ms. Under the condition of a fixed sampling interval of 71 ms， the time correlation coefficient of water content at different initial times is analyzed， and the maximum deviation of the fluctuation from the average value is 23%， which proves that the flow field in the measurement area is steady turbulence. This method can provide an effective measurement method for studying the characteristics of liquid cloud microphysics and turbulence and the mechanism of their mutual influence.

Atmospheric temperature is the basic parameter for the detection of atmospheric fine structure， and obtaining high-precision atmospheric temperature profile is crucial for weather forecast and climate research. In this paper， the self-developed polarization high-spectral-resolution lidar is used to realize the all-day and high signal-to-noise ratio measurement of atmospheric temperature. The algorithm by combining polarization high-spectral-resolution lidar and microwave radiometer are proposed by linear splicing method， and the complementary advantages of the two are realized. The results show that the polarization high-spectral-resolution lidar can realize the effective detection of atmospheric temperature at a distance of 4 km， and the error is mainly within ±2 K. The detection error of microwave radiometer is relatively low within 3 km， and the error is between -4 K and -2 K above 3 km. After splicing， the error is ±1 K within 3.5 km， and the correlation increases from 0.95 to 0.97. The results show that the lidar can effectively detect the atmospheric temperature in the boundary layer. Through the integration with the microwave radiometer， the blind area problem of the lidar can be solved， and the detection accuracy of the microwave radiometer can be improved.

Because the measurement accuracy of the diffuse radiation photoelectric sensor in the photoelectric insolation meter seriously affects the accuracy of the solar irradiance measurement， in order to reduce the scattering error，more accurate simulation of the diffuse radiation is needed for indoor calibration. Through the linear correlation analysis between the radiation attenuation rate and each meteorological factor in the day-by-day time scale， the daily horizontal solar scattering radiation model in Changchun area is obtained after multivariate linear regression fitting. The radiation attenuation caused by the scattering of water vapor and dust is simulated in the indoor verification system， and the indoor scattering environment simulation chamber is designed. The results show that the fitted values of the daily scattered radiation in the horizontal plane are well matched with the measured values. The measured values and fitted values are evenly distributed on both sides of the fitted line， and the correlation coefficient （R2） is above 0.8， indicating that the scattered radiation model has a good effect.

Based on the requirement of wind velocity measurement， an all-fiber doppler coherent wind lidar system is built with continuous wave laser source at band 1 550 nm. It is analyzed theoretically for the Carrier-to-noise ratio function of the continuous wave coherent lidar and the weighing function of the wind velocity at different focusing distance on the basis of the lidar equation. A vari-focusing optical antenna with the focusing distance range from 5 m to 200 m is designed and fabricated according to the requirement of wind detection. The optical beam expanding module adopts the Galilean refractive structure with the beam expanding ratio as 23 and the optical quality is close to the diffraction limit. The calibration test is executed by using a rotating motor disk. The rotation speed range of the disk is from －3 000 r/min to +3 000 r/min. The diameter of the disk is 26 cm. While the doppler frequency shift of the line of sight velocity is positive and negative， the correlation coefficients between the velocity measurement data of the lidar system and the theoretical calculation result are 0.998 and 0.993. At the same time the standard deviations of velocity are 0.151 m/s and 0.229 m/s， respectively. The wind lidar is then used to measure the atmospheric wind speed. It works correctly to apply the wind lidar to measure the atmospheric wind velocity.

The optical signal is distorted in the atmospheric turbulence， after passing through the defective optical antenna and the space optical hybrid， there are problems of low hybrid efficiency and jitter. According to the influence of 90° space optical hybrid with space output and single-mode output， the hybrid efficiency model of space optical hybrid with primary aberration is derived. Then the influence of aberration and turbulence on hybrid efficiency is studied. The simulation results show that for the space output 90° space optical hybrid with a target radius of 50 μm of the detector， the tilt， spherical aberration， defocus，coma，and astigmatism with aberration of 0.2λ cause the hybrid efficiency to decrease by 9.8%， 0.6%， 0.36%， 0.02% and 0.01%， respectively. Astigmatism and coma have no effect on the hybrid efficiency. For the single-mode output hybrid， the tilt， astigmatism， defocus， coma， and spherical aberration with aberration of 0.2λ cause the hybrid efficiency to decrease by 14.11%， 8.39%， 6.35%， 2.63% and 1.13%， respectively. When the turbulence intensity Cn2-17 m-2/3， the hybrid efficiency of the spatial output type is more than 0.19 higher than that of the single-mode output 90° space optical hybrid， and when the turbulence intensity Cn2>6.4×10-16 m-2/3 ， the hybrid efficiency of the two is close to zero. Finally， the space output and single-mode output optical hybrid are designed and processed， and the performance test platform is built. For the space output hybrid with a detector target surface radius of 50 μm， the tilt， spherical aberration， and defocus of 0.2λ cause the hybrid efficiency to decrease by 52%， 10%， and 6%； for the single-mode output hybrid， the tilt， astigmatism and defocus with aberration of 0.2λ cause the hybrid efficiency to decrease by 65%， 24% and 11%. Other aberrations have no effect on the hybrid efficiency.The experimental results of turbulence on the hybrid performance show that the standard deviation of the intermediate frequency signal value of the space output optical hybrid is 21.388， which is much lower than that of single-mode output standard deviation 247.442.

In order to measure the ozone concentration， a 3.3 μm laser heterodyne spectrometer for field observation was built and the spectral resolution was measured to be 0.004 cm-1. The ozone spectrum was measured at Golmud in Qinghai Province by the 3.3 μm laser heterodyne spectrometer， and the ozone concentration was inversed by using the optimal estimation algorithm. During the field observation， the average column concentration of ozone was inversed to be 241.7 DU， the column concentration increased about 4 DU/h. The results show that the laser heterodyne spectrometer combines with the optimal estimation algorithm is capable of measuring the ozone concentration of the whole atmosphere at the plateau， and has important applications for the environment， meteorology and laser atmospheric transmission assessment.

The pulsed lidar system and continuous lidar system are improved by redesigning the parameters considering more details of the systems and choosing the more appropriate equipment according to limitations of the systems. After the simulation of the return signals， these two kinds of lidar systems are compared in SNR and difficulty of implementation. The results show that the pulsed lidar is more suitable for measuring the metastable Helium density of thermosphere and exosphere.

A ground-based Multi-Axis Differential Optical Absorption Spectroscopy （MAX-DOAS） with the characteristics of simple operation， wide range and high sensitivity was constructed， and the time series of HCHO in Huaibei area from October 2019 to May 2020 were obtained continuously. In order to reduce the interference of other gases， different bands are used to retrieve the differential slant column density of HCHO. Through comparison， it was found that when the band of 324~342 nm was selected， the inversion error fluctuation is the minimum， and the concentration of HCHO gas can be obtained precisely. According to the results of HCHO monthly mean values， compared with the before and after COVIN-9 epidemic ，the concentration of HCHO in the COVIN-9 epidemic were decreased by 35% and 23% respectively. The results of daily and weekly variations respectively showed that HCHO concentration in Huaibei area have daily variation characteristics of high in the morning and evening and low in noon， and there is no obvious weekend effect. Combined with Hysplit wind field backward trajectory model， the wind field of high value weather was studied. It was found that during January 12~14 and 18~21， 2020， under the influence of northwest wind field， the pollution transport from Dangshan and other places in Huaibei area will be affected， which will lead to the increase of HCHO concentration. The result of MAX-DOAS measurement of HCHO vertical column density were compared with the OMI satellite data， and it was found that the two methods had good consistency （R2 = 0.87）.

The Monte Carlo model of laser scattering in turbid media was established with the help of scattering angle from the cumulative probability density interpolating of the Mie scattering phase function. With the model， the laser multiple scattering in uniform monodisperse polystyrene turbid medium was studied， the influence of turbid media with different optical depths and scattering phase function on laser multiple scattering was explored. By controlling the concentration of 5 μm and 10 μm size polystyrene particles， changing the optical depths of the turbid medium as 2， 5 and 8， the theoretical simulation and experimental side scattering images were obtained and compared. The percentage difference of scattering light intensity attenuation between the simulation and experiment is measured less than 16% under the same medium condition， and the trend of them is basically the same. The simulation can also provide the distribution of light intensity of different scattering orders， and accurately analyze the influence of multiple scattering.

Based on the extended Huygens-Fresnel integral and the theory of ghost imaging, the reflective lensless ghost imaging through Kolmogorov oceanic turbulence is investigated. The theoretical expressions for the impulse response function and the visibility of reflective ghost imaging in oceanic turbulence are obtained. The results show that the quality of reflective ghost imaging could be maintained at a relatively small incident reflective angle, whereas the quality is degraded dramatically at a relatively long distance with a relatively big incident reflective angle. The visibility of reflective ghost imaging is analyzed under various turbulence conditions and over different propagation distances by numerical calculation. It is a guidance for the realization of adaptive underwater optical ghost imaging over different length scales under the effect of oceanic turbulence.

A real-time correction method based on Global Navigation Satellite System difference is proposed for the atmospheric phase disturbance of the antenna array. The atomic clock with high stability is used as the external frequency standard, the single difference of the carrier phase and the double difference on the epoch between the two stations are utilized, and the phase change caused by the satellite movement is deducted through the ephemeris. After the cycle slip detection and correction, the satellite orbit and the coordinate error of the station are eliminated through the long period fitting. Finally, the real-time measurement of ionospheric and tropospheric disturbances in two places is realized by dual frequency or multi frequency signals. A set of Global Navigation Satellite System receiving equipment was deployed at Miyun Observing Station and Kunming Observing Station of the National Astronomical Observatory of the Chinese Academy of Sciences, to verify the real-time correction method of atmospheric phase disturbance. The results show that the root-mean-square of the corrected atmospheric phase disturbance reaches 1.9 mm, modified by using the dual frequency carrier phase, under different weather conditions. The results indicate that the method can be used for the correction of the atmospheric phase disturbance of the antenna array in radio astronomy and deep space exploration.

In order to distinguish the non-spherical haze particles with different physical characteristics, the haze detection model of "solar-blind" ultraviolet backscatter is established to simulate the process of UV backscatter under the condition of non-spherical haze, based on T-matrix theory and Monte Carlo method. The peak power and the full width at half maximum of UV pulse with different widths are analyzed. The simulation results show that when the haze concentration is less than 500 μg/m3, the peak power of backscatter echo of UV pulse increases with the increase of haze concentration, and there is a linear relationship between the peak power of pulse echo of different concentrations of haze, and the full width at half maximum of pulse echo decrease with the increase of haze concentration. For ellipsoidal and cylindrical haze particles, under the same concentration, the smaller the shape variable of particles is, the larger the peak power and the full width at half maximum of pulse echo are. For chebyshev haze particles, under the same concentration, the larger the deformation parameters and ripple parameters are, the larger the peak power and the full width at half maximum of pulse echo are. The results of this study can provide a basis for the detection of haze concentration and the discrimination of non-spherical haze particles by ultraviolet light.

For accurately reflecting the practical features of turbulence, the modified atmospheric spectrum model should be applyed in the simulation of optical wave propagation. To do this, the method of generating high precision turbulent phase screen is proposed for the modified atmospheric spectrum, which is on the bases of optimized phase screen model. By extending the low frequency region and changing the sampling Settings of the model, the maximum relative error in low frequency region was reduced to 1%. As a comparison, the maximum relative error in low frequency region was 6.75% for Optimization-based method before improvement, 22.99% for original FFT method and 16.81% for subharmonic method. By using this method, the simulation of Gaussian beam propagating in turbulence has been done and the second-order statistical properties include beam spread and beam wander have been estimated. The results show that, in the case of weak fluctuation level, the degree of compliance with the analytical approximations is good. However, under the condition of strong fluctuation level, the deviation between the simulation results and the theoretical results is increasing with distance. The deviation of beam spread is up to 6 cm, while the deviation of beam wander is up to 1 cm, which can be explained by the fact that the theoretical model cannot predict the beam wander saturation. In comparison with the simulation results of the Von-Karman spectrum, the beam spread estimated by modified atmospheric spectrum is slightly larger than that estimated by Von-Karman spectrum, and beam wander predicted by modified atmospheric spectrum shows a faster rate to reach saturation than that predicted by the Von Karman spectrum, it is precisely induced by the "bump" of the modified atmosphere spectrum. So we conclude that the phase screen generated by the method presented here can characterize the refractive index perturbation of the actual atmosphere effectively.

The severe backscattering of the shallow seawater hinders the application of laser detection in the offshore. The backscattering of the echo signal restricts the depth, resolution and contrast of underwater target detection. Two novel ocean lidar with high scattering suppression radio, chaotic lidar and coherent dual frequency lidar, are studied. The two kinds of lidar signal owns the inherent intensity modulation characteristics, and then the backscattering owns the low frequency characteristics. Therefore, the backscattering of seawater can be removed by the band-pass or high pass filtering when the intensity of the object signal and the backscattering light are the approximate same magnitude, so as to improve the signal-to-noise ratio of the ocean lidar system.

The echo signals of the CCD side-scattering lidar under different wind speed conditions were analyzed. According to Mie scattering theory and CCD side-scattering LiDAR principle, the correlation between aerosol concentration and its side-scattering light intensity is determined. By considering the relationship between aerosol concentration and wind speed, the echo signals of side scatter lidar under different wind speed conditions are analyzed. By comparing the experiments under two conditions of axial fan wind and natural wind, it can be found that when the wind speed is in the range of 1~4.5 m/s, the aerosol concentration increases with the increasing of wind speed; otherwise when the wind speed is in the range of 4.5~6 m/s, the aerosol concentration decreases with the increasing of wind speed.Normalizing the results, conclusions are drawn that when the wind speed are in the range of 1~4.5 m/s, the side-scattering light intensity increase by 3.7% and 3.9% with the wind speeds increase by 1 m/s in the conditions of axial fan and natural wind. When the wind speedsare in the range of 4.5~ 6.0 m/s, the light intensity decreased by 3.1% and 3.8% with wind speeds increases by 1 m/s in the two conditions, and the trend exists in all wind coming directions of natural wind.

PM2.5 concentration distribution measurement in space at different heights is difficult, this paper uses lidar and atmospheric transmission meter and particle spectrometer for joint detection, through three kinds of instrument data with the vertical distribution of PM2.5 concentration inversion. The function relationship between mass concentration of ground PM2.5 and atmospheric transmissivity is established by data of atmospheric transmittance and particle size spectrometer. Based on the ground atmospheric transmittance measured by the atmospheric transmission meter, the boundary value of the lidar atmospheric transmittance at high altitude is determined through an iterative algorithm, and the vertical distribution of the atmospheric transmittance is retrieved in combination with Fernald integral method. The vertical distribution of PM2.5 mass concentration is obtained by the atmospheric transmittance height profile detected by lidar. The results showed that the accuracy of the vertical distribution of atmospheric transmittance has been improved by the revised atmospheric transmittance. The profile of PM2.5 mass concentration well reflects the microphysical variation of the vertical distribution of aerosols.

Observation of the total columns of H2O, CO2, CH4, and CO in Hefei is presented based on ground-based Fourier transform infrared spectrometer (EM27/SUN). The results show that, the XH2O and XCO2 vary greatly during the measurement period while the XCH4 and XCO vary slightly. The range of H2O and CO2 are 1 353.17~5 289.43 ppm and 409.22~415.05 ppm, at the same time, the standard deviation of XCH4 and XCO are in the order of 10-2. The average values of XH2O, XCO2, XCH4 and XCO are 2 109.10 ppm, 411.59 ppm, 1.87 ppm and 0.13 ppm respectively. The measured XCO2 and XCH4 are compared with the WACCM model and GOSAT satellite data, respectively. The comparison results show that the XCO2 and XCH4 calculated by WACCM model are relatively stable, with only slight changes near the average value. The GOSAT observations are slightly lower than those of EM27/SUN observations, with the relative deviations of XCO2 and XCH4 are 0.45% and 0.34%, respectively. The time series of the total column of XCO2 and XCH4 from 2010 to 2018 are analyzed by the GOSAT satellite data. It is found that the value of XCO2 increases from 390.83 ppm to 410.30 ppm, with a relative growth rate of 4.9%; the value of XCH4 increases from 1.802 ppm to 1.869 ppm, with a relative growth rate of 3.7%. The results may provide the theoretical basis for tracking the sources and sinks of greenhouse gases in Hefei and its surrounding areas.

Aiming at the problem that the light spot in underwater wireless laser communication is easily deformed， susceptible to turbulence and to be blocked， firstly， the tracking light spot algorithm of Mean Shift combined with unscented Kalman filter and threshold judgment is used to obtain the real-time position coordinates of the tracking light spot. The analysis results show that when the light spot is blocked， deformed or affected by turbulence， the error between actual movement trajectory and tracking movement trajectory are about 2.1%， 4%， and 1.2%， respectively， which verifies the feasibility of the algorithm. A receiver alignment system is built to track the real-time position of the light spot. The real-time alignment of the receiver and transmitter is controlled based on the relationship of the real-time position and the center position. The alignment accuracy of the system is reflected by the deviation between the actual center coordinates and the center coordinates of the light spot obtained by comparing the alignment system. The experiment results show that the greater the angular velocity of the receiver's motion， the smaller the alignment accuracy.

In order to solve the problem of deviation in the calculation method of traditional lidar geometric factors， the full field and half field of view functions in the telescope are derived through geometric optics， and the geometric factor is obtained by the ratio of the double integral of the field of view function of the uniformly emitted laser beam area to the cross-sectional area of the laser beam. Considering the effect of the laser optical axis tilt misalignment， the geometric factor calculation equation for the atmospheric detection coaxial lidar is derived. According to the proposed calculation equation， the geometric factor of the typical atmospheric detection coaxial lidar is calculated and compared with the traditional method result. The result shows that the minimum full overlap distance is consistent. Finally， the effects of laser beam diameter， divergence angle， and laser optical axis tilt angle related to excitation-emission on geometric factors are analyzed. The results show that the influence of the laser divergence angle is greater than that of the beam diameter. The method is suitable for the rapid calculation of the lidar geometric factor of the uniformly distributed laser emission beam and can provide a reference for the design of the lidar.

The imaging characteristics of CCD were analyzed,a geometric calibration experiment on side-scatter lidar was designed,the each CCD pixel angle was achieved,and the relation between CCD pixels and the position of scattered light was established.Two experimental signals were calibrated using this method.The calibrated results are compared with POM02 in aerosol phase function,and with the backscattering lidar in signal,respectively.The comparison results indicate that the profiles of aerosol phase function from this method and from POM02 are same,and the signal from side-scatter lidar has the same tendency with the range-corrected signal from backscatter lidar above 650 m.Moreover,side-scatter lidar overcomes the shortcoming that the backscatter lidar can not detect the full signals in near range.This calibration method is reliable and useful for further studying the spatial-temporal aerosol profile in near surface by side-scatter lidar.

Based on Rytov approximation and extended Huygens-Fresnel principle, the analytical expressions for average intensity and scintillation index on target plane in non-Kolmogorov weak turbulence along slant paths were derived, the system efficiency of heterodyne lidar wass given. The system efficiency of heterodyne lidar is examined and the effects of exponent parameter, zenith angle, structure constant, system configurations and telescope aperture on system efficiency are also analyzed.It is shown that when the generalized index is less than 3.2 or greater than 3.8, the system efficiency decreases fast as the index increases. System efficiency decreases with the increase of zenith angle. System efficiency of bistatic configurations is smaller than that of monostatic configurations. With the increase of the telescope aperture, the system efficiency arrives the minimum, and eventually flattens out. In near field, the system efficiency of collimated beam is larger than the other two forms, but in far field the system efficiency of divergent beam is the largestone.

To achieve small residual wavefront gradient tilt corrected by the adaptive optics system and good robust stability of the system, a mixed H2/H∞ control method for the adaptive optics system was proposed. In order to verify the control performance, the atmospheric turbulence wavefront gradient tilt was simulated, and the residual wavefront gradient tilt corrected by the adaptive optics wavefront gradient tilt correction test platform with the mixed H2/H∞ controller and by the one with the classic integral controller was compared. The robust stability of the two systems was compared as well. The result demonstrated that the test platform with the mixed H2/H∞ controller achieved not only smaller residual wavefront gradient tilt but also better robust stability compared to the one with the classic integral controller, and proved the efficiency of the mixed H2/H∞ control method for the adaptive optics system.

In order to satisfy the requirement from the polarization navigation for the spatial position of feature points in the sky,a method is introduced to calculate the solar spatial position with the Rayleigh atmosphere polarization pattern.First,the distribution pattern of the polarized sky light is established on the basis of the Rayleigh scattering theory of the atmosphere optics.Then a method using nonlinear least square optimization is introduced to solve the matter of finding the solar spatial position with finite sampling information from the atmosphere polarization pattern.The Gauss-Newton method couple with global search for initial value guarantee less steady residual error.Experimental simulation results indicate that the error of the solar zenith angle and azimuth angle is respectively less than 10-5 degree and less than 10-6 degree with sampling the degree of polarization,and the errors of the two angles are all less than 10-6 with sampling the angle of the degree.And the method has shown good precision under different sampling types.As a result,the method is proved to be precise and adapt various sampling types,the polarization pattern can be efficiently processed into the solar spatial position.

Differential image motion monitor is widely used to obtain real-time seeing. Differential image motion was numerical simulated by random phase screen and optical defocus aberration, and the measurement accuracy of differential image motion monitor was analyzed, which showed that differential image motion monitor can reliably measure the near-ground turbulence. Comparision of experiment of two differential image motion monitors with the same hardwares was carried out at Xinglong Station of National Astronomical Observatory of China. The correlation between exposure time and measuring results was analyzed. The results show that the limited exposue time will reduce differential image motion and underestimate seeing value, and the trends over time and statistics of measurement results have good consistency.

Based on the extended Huygens-Fresnel principle and the quadratic approximation of phase structure function, the theoretical modal of optical intensity distribution on the focal plane for focused hollow vortex beams with a Gaussian background propagating in turbulent atmosphere was investigated and obtained.The effects of atmospheric index structure constant C2n, topological charge, focal length and beam wavelength on optical intensity distribution on the focal plane were analyzed. The results indicate that with the increase of focal length, the intensity distribution on the focal plane varies from central-dip form to Gaussian distribution. The effects of weak turbulence on intensity distribution are negligible. The maintenance of singularity of vortex beams with larger topological charge in turbulent atmosphere is better than that for vortex beams with smaller topological charge. The central-dip form of the intensity distribution becomes shallow and the intensity distribution becomes smooth with the turbulence outer scale increasing.

Computational analysis was carried out regarding the aero-optical effect induced by the turbulence field surrounding the hyper-speed aircraft.The transport equation of the variance of the index of refraction fluctuations was derived based on the scalar transport governing equations of the turbulence model. The refraction fluctuation variances and the fluctuations correlation and phase covariance function along the line-of sight were obtained. Using statistical methods, the turbulent modulation transfer function(MTF) and the refraction correlation function induced in the transmission direction for the refraction fluctuation was computed, which characterized the aero-optical effect in different aspects. Experimental results show that the amplitude response of the transmission function of the aero-optical effect can be characterized as a low-pass filter, which results blurring in the obtained image; while its irregular phase response results nonlinear shifts of the target in the image.And, the higher the Mach number, the more severe the distortion in the image. The correctness of the theoretical MTF was evaluated by wind tunnel experiment.

Using two-channel detection,influences on laser radar cross section measure accuracy caused by atmosphere condition changing were studied.The new formula of comparing measure was deduced.An experiment was carried out on the new formula,and its using qualification was discussed.Through measuring the diffuse reflection board′s LRCS in the outfield,the result indicates that the new formula can correct the measure error because of the atmosphere condition changing and help to improve measure accuracy,and its calculation is very brief and carried out easily.

Under Rytov approximation and geometrical optics approximation, a formula of the variance of the log-amplitude derivative was deduced for the case of a plane wave propagating through turbulence. It was clarified that the main factors, which determined the variance, were the Rytov variance, the turbulence inner scale and the Fresnel size. And, based on the formulae deduced by Voitsekhovich, the expression for density of phase branch points was modified. The relationship between the density and the above mentioned parameters was analyzed thoroughly, which indicates that the density increases with Rytov variance increasing and decreases with turbulence inner scale and Fresnel size increasing under the condition of Rytov variance less than 1.

BP decoding of LDPC code for weak atmospheric turbulent optical PPM systems was studied, and corresponding decoding algorithm was introduced according to the system model. Through theoretical analysis and extensive computer simulations, the result shows that the LDPC coded weak atmospheric turbulent optical PPM system has better BER than the uncoded weak atmospheric turbulent optical PPM system, but the BER performance of the system increases with the increase of slot.

A new method was proposed to retrieve imaginary part of aerosol refractive index by using two kinds of particle counters.One measured the optical size of aerosol particle,which was greatly effected by the refractive imaginary part,and the other one measured aerodynamic of aerosol particle size,which was not effected by refractive imaginary part.The aerosol refractive index was retrieved by combining the measurement of these two kinds of particle counters.

Based on the analysis of random errors and characteristic of lidar data,a new method of estimating random errors is introduced,which is called noise scale factor method.Using background signals in far range in one measurement,the noise scale factor is obtained,and the uncertainty of lidar signals at any distances can be estimated.The experiment results show that this method is reliable and feasible.

The causes of fog,the relevant mathematical models and its influence on atmospheric laser communication system are analyzed.In order to overcome the influence of fog on wireless optical communication link,the LDPC codes as channel coding are applied into atmospheric laser communication system,and it is simulated in the foggy atmospheric channel with combination of BP iterative decoding algorithm and sub-carrier PSK intensity modulation.The simulation results show that LDPC codes have excellent error correction capabilities and access to a larger coding gain,and the proposed scheme can satisfy the need of atmospheric laser communication system.

Based on the theory of multi-aperture scintillation sensor,the contribution of aperture filter function and spectral response function to weighting function are discussed,respectively.According to simulation results of scintillation with Hufnagel-Valley 5/7 model included bounding layer,vertical turbulence profile is inversed with the method of singular value decomposition.The magnitudes of the vertical inversion results are between and ，and decreases with height increased,which are all in accord with academic model.Using the measuring results of Shack-Hartman,horizontal turbulence profile is inversed,the transmission distance of which is 1 km.The magnitudes of horizontal inversion results are between 10-14 and 10-15，and the tendency accords the practice condition of experimental site depending on propagation distance,and accords the ensemble average depending on time.