Using large aperture projection optics to monitor characteristic parameters of far field speckle

Abstract

In order to systematically evaluate the characteristic parameters of far field speckle in the real atmosphere condition and analyze the influence of laser atmospheric propagation on the optoelectronic system, a monitoring method is presented using large aperture projection optics. The projection optics is made of low cost and large aperture Fresnel lens, which can project the irradiance distribution of far field speckle on the CCD detector. The receiving power and scintillation index on a certain aperture can be evaluated through CCD imaging process. The beam wander and beam radius can also be evaluated under the condition that the receiving aperture is large enough and the speckle would not leave the Fresnel lens because of the beam wander effect. The error of CCD pixel response non-uniformity and its influence and the calibration of CCD irradiance response function and image geometric projection coefficient are discussed. The experiments show that this system is feasible for the monitoring of far field speckle characteristic parameters in the laser atmospheric propagation. Especially for the free space optical communication, it can prove experiment data support on the slow fading research of median level and optimal design of detection threshold under the complex influence of atmospheric extinction and various kinds of turbulence effects.