Study Of Laser Transmission Characteristics Of Atmospheric Trubulence And The Effect On The SAL

Synthetic aperture ladar (SAL) is a laser radar,which is through the movement ofsmall-aperture laser radar to synthesize a large aperture to achieve high-resolutionimaging, it has a broad application prospects. Because of the very short laserwavelength, the great influence of the atmospheric turbulence on the laser transmissionin the atmosphere, and the coherent optical heterodyne detection used in the SAL, thusthere is a serious influence of the atmospheric turbulence on the SAL imaging, andbecoming one of the main factors which restrict SAL towards the practical application.In this paper the transmission characteristics of the laser in atmospheric turbulenceis analyzed and studied, and the impact of atmospheric turbulence effects of the laser onthe SAL is calculated and analyzed. According to the theory and methods to wavepropagation and scattering in random media, by using the modified von Karman’turbulence spectrum model, the impact of atmospheric turbulence on the averageintensity of the laser transmission in the oblique double-passaging path is studied, andthe analytical expression of the average intensity of Gaussian beam on the optical axisin this spectrum is derived and a numerical analysis is carried. In this paper theangle-of-arrival fluctuation of the beam transmission in the oblique double-passagingpath and the beam wander in the oblique transmission is analyzed in the von Karman’spectrum; the phase fluctuation caused by the atmosphere turbulence in the obliquepath is calculated and analyzed.Finally, based on the heterodyne efficiency and the SAL echo signal model, theSAL heterodyne photocurrent at the straight Gaussian beam affected by atmosphericturbulence or not is smulated and calculated by using Matlab soft-ware, and the impactof atmospheric turbulence on the SAL is analyzed.The results of the computation showthat, under the influence of atmospheric turbulence at the consideration of the internaland external scale and the modified von Karman ’spectrum, for the SAL on the1kmhigh, the average intensity descending range is less than one order of magnitude, andthe impact on the heterodyne photocurrent is not too obvious; At this altitude, the beamwander caused by the atmospheric turbulence is microns, it is great the influence on theheterodyne photocurrent; The phase fluctuation is random, so the influence on theheterodyne photocurrent also is random.