Equations are obtained which describe the trajectory of light ray through the unhomogeneous atmospheric surface layer when the three-dimensional equation of ray is analyzed and simplified. The equations can be used as the base of optical measurement. Characteristics of temperature gradient in the surface layer are discussed. The integral which relates the refraction angle and its variable to the temperature gradient based on the geometry of ray curve and the weighting function of temperature gradient are discussed. It was shown that the area-averaged value can not be obtained by means of unilateral measurement of angle when the distribution of temperature gradient is unhomogeneous and symmetrical. A bidirectional optical system is necessary. It was shown that the area-averaged temperature profile also can not be obtained by means of a system with multi-laser sources in the unhomogeneous atmospheric surface layer.

Atmospheric effects including atmosphere absorption, scattering and turbulence in the process of laser ranging are studied, and atmospheric propagation characteristics of common 1.06 [EQUATION]m medium-range or short-range laser ranging close to ground are analyzed. It provides reference for design and application of laser rangefinders.

Based on the quadratic approximation of the Rytov’s phase structure function and the Huygens-Fresnel principle, propagation equation for the spatial degree of coherence of partially coherent flat-topped beams propagating in turbulence atmosphere is derived, and the properties of the spatial degree of coherence in turbulence atmosphere are investigated numerically. The result shows that properties of spatial degree of coherence of partially coherent flat-topped beams are determined by the refractive index structure constant of atmospheric turbulence, the beams’ relative length of the space-related, the order of flat-topped beams, transmission distance and location of the observation point in common. It also shows that the oscillatory behavior and phase singularities of the spatial degree of coherence may occur when partially coherent flat-topped beams propagates through atmosphere turbulence. But the oscillatory behavior becomes sweaker with atmosphere turbulence increasing, and the phenomena of the oscillatory behavior and phase singularities will disappear in the end.

It is important to monitor atmospheric parameters such as ozone concentration, relative humidity, aerosol backscattering coefficient, temperature, CO[EQUATION] concentration, and analyze the basic characteristics for building native atmospheric mode and establishing appropriate environment protection policy. These atmospheric parameters can be measured by L625 multifunction lidar. Data measured with L625 lidar and data from MLS, radiosonde, DWL lidar, Raman lidar are compared. Results indicate that the parameters measuremed by L625 multifunction lidar is feasible and reliable. The atmospheric parameters are analyzed, and the basic characteristics at summer over Hefei are obtained.

Based on the improved BP algorithm and Mie scattering theory, the nonlinear relation of wavelength, scattering coefficient, absorption coefficient and equivalent complex refractive index is developed. The BP neural network model of the equivalent refractive index of aerosol is also developed. The optical properties of aerosol obtained from inversion refractive index, such as scattering coefficient, absorption coefficient, are in good agreement with measurement results.

Based on tunable diode laser absorption spectroscopy (TDLAS) technology, combining a Herriot cell with optical length of 50 m, using a wave-length-meter to scale the positions of the lines, the positions and intensities of 71 ethane lines between 6039 cm[EQUATION] and 6054 cm[EQUATION] are precisely measured, and the minimum detection absorption intensity reaches 10[EQUATION] cm[EQUATION]/(molecule[EQUATION]cm[EQUATION]). Results and errors are analyzed in detail, which is very useful to carry on research of natural gas in further.

An infrared radiometric calibration method with high precision is put forward based on the parametric conversion technique. The infrared signal radiation is mixed with higher frequency laser pump radiation in a nonlinear crystal, and the effect of parametric amplification occurs. The infrared radiation is converted to visible radiation by using phase-matching technique. It is a method with absoluteness, so the higher infrared calibration precision could be reached. Blackbody is considered as model of infrared radiation, the feasibility of infrared radiation calibration by parametric conversion technique is analyzed theoretically. The new calibration technique will be widely used in the field of communication, night vision and remote sensing.

Influences of aperture size and hierarchical model of turbulence on weighting functions are discussed. Based on these, using singular value decomposition, vertical turbulence profiles for different aperture sizes and hierarchical models of turbulence are inversed and influences of hierarchical models of turbulence and aperture sizes on inversion results are discussed. The results indicate that vertical turbulence profiles are more reasonable based on weighting functions of smaller aperture ratio and geometric hierarchical model of turbulence.

The intra-pulse spectroscopy based on a room-temperature distributed-feedback pulsed quantum cascade (QC) laser is introduced. The thermal chirp during a long excitation pulse is applied to a quantum-cascade laser centered at 7.85 [EQUATION]m, which is used for fast wavelength scanning. The laser spectra under different working parameters are compared and analyzed, with the aim of finding out the optimal working parameters of laser. The N[EQUATION]O absorption spectra centered at 1273.7 cm[EQUATION] are also obtained.

A spectral data acquisition system is designed based on NMOS linear image sensor and micro controller unit (MCU) technology. The hardware and operating principle of this system are introduced, and the structure, principle and characteristics of S3924-512Q image sensor are analyzed in detail. Data acquisition of spectral signal is realized by A/D conversion controlled by PIC16F877A MCU, and flowchart of the program is given. Using this system, spectral acquisition of the specific band with high precision is achieved.

Wind profile radar is an effective tool for detecting atmospheric wind field and turbulence. Its echo is liable to be interfered by ground clutter and becomes complicated. To improve detection precision of radar, ground clutter suppression is an important part of radar signal and spectrum processing. Current method of ground clutter suppression is introduced and its deficiency is analyzed, and the characteristics of ground clutter and radar atmospheric echo spectrum in frequency domain are investigated. Combined with gradient analysis of atmospheric echo spectrum, the method for suppressing ground clutter is described based on Gaussian least square quadratic fitting to the uncontaminated atmospheric echo spectrum. Results show that it is feasible to suppress ground clutter.

The optimal wavelength detecting the height of cloud is analyzed. Profiles of molecule extinction coefficient and aerosol extinction coefficient, which is necessary for signal estimation, are presented. Calculation for the geometric overlap factor with the existing slit diaphragm in a co-axial lidar is also given. Based on the specific features and lidar equation, simulations of the backscattering power and impact on the signal to noise ratio are discussed when the emitting power, emitting pulse numbers and width of the filter change. Results are meaningful for discussing the ceilometer’s detecting capability, and it offers theoretical basis to determine technical parameters of a ceilometer.