The report presents the results of experiments to compensate for the mismatch of the optical axes of the transmitter and receiver based on backscattering of the focused beam radiation. The matching error does not exceed 2.5 arc seconds.
The report considers the possibility of estimation of the profile along the optical path of the transverse wind velocity component from fluctuations in the image of a diffuse target illuminated by a laser beam. An algorithm for processing video images based on the construction of a spatiotemporal correlation function of fluctuations in the intensity of radiation scattered from a target is proposed. The results of testing the proposed technique by means of numerical simulation and in experiments at the IOA SB RAS test site are presented.
The results of an experiment on adaptive correction of random initial distortions of the wavefront of a collimated laser beam based on the signal of atmospheric backscattering are presented. The backscattered signal was recorded by a receiver with a limited field of view from an additional source at a different wavelength. A coaxial transmitter receiving scheme with a large transmitting and small receiving apertures was used. The quality of the correction was assessed using the Shack-Hartmann sensor, as well as by the two-dimensional distribution of the intensity on the remote screen. It is shown that after adaptive operation, the divergence of the distorted beam decreases.
The results of an experiment on compensation of random initial distortions of the wave front of an atmospheric backscattering signal from an additional laser source using the aperture sensing method are presented. The quality control of the correction was evaluated using a Shack-Hartmann sensor, as well as the intensity distribution at the end of the propagation path. It was shown that during the operation of the setup, the level of artificially introduced aberrations of the main beam decreased, the focusing quality increased, and the signal at the radiation receiver from an additional source increased.
The report considers the possibility of determining the average transverse component of the wind velocity integral along the optical path from image fluctuations of a diffuse target illuminated by a laser beam. An algorithm for processing video images based on the construction of a spatio-temporal correlation function of fluctuations in the intensity of radiation scattered by a target is proposed. The results of experimental verification of the proposed method are presented.
The paper presents the results of an experiment on the formation of vortex optical fields propagating in a convective turbulent medium. The formation of vortex optical fields is carried out with the help of a micromirror modulator.
Calculations are presented for the atmospheric attenuation of HF/DF laser radiation propagating from a height of 0 and 10 km at angles of 0 and 35 degrees relative to the zenith. The results of numerical simulation of the influence of the turbulent atmosphere using the phase screen method and the position of the radiation detector at altitudes of 200 and 600 km are also presented.
The results of an experiment using the Shack-Hartmann sensor to control aberrations inside an adaptive transmissive optical system are presented in this article. The correction was made using the signal of reverse atmospheric scattering with different parameters of the transceiver. It is shown that with the optimal parameters of the receiving transmitter, the level of artificially introduced spherical aberrations is reduced by 10-15 times.
Data are presented about the variations in the average power of lidar echo signals with coherent and incoherent receiving over wide range of variations of the refractive turbulence strength in the atmosphere. It is established that in the case of incoherent receiving the backscatter amplification coefficient first increases with increase of the turbulence strength, then saturates at a certain level in the regime of strong turbulence on the probing path and decreases with further refractive turbulence strength increase. The maximum value of the amplification coefficient achievable at a given distance depends on the refractive turbulence strength at the moment of measurement. The time course of the backscattering amplification coefficient is in a good agreement with the temporal changes of the structural constant of turbulent fluctuations of the air refractive index, determined from independent measurements.
In this paper, an optical model of a shock wave is constructed, which is formed by the supersonic flow of air in the flowing of an ogival-shaped body. The average values of the gas flow parameters were calculated from the Navier- Stokes equations using the Fluent 6.0 package taking into account the compressibility of the gas. The results of numerical simulation of the propagation of a laser beam through a shock wave formed during supersonic flow around an ogival-shaped body are presented.
The quality of adaptive suppression of initial aberrations of the wave front of a main laser beam with the use of the method of aperture sensing by the signal of atmospheric backscattering of the additional (sensing) laser radiation at a different wavelength has been studied experimentally. It is shown that wavefront distortions of the main laser beam were decreased significantly during the setup operation.
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