Abstract: The background and meaning of developing the technique of fold pass laser imaging and detection for atmospheric optical turbulence are analyzed, and the physical processes and mathematic models of fold pass laser transmission are represented. Using the constructed experimental system, the echoed dynamic laser speckle images for man-made air flow and natural turbulence flow are obtained. The typical characteristics of the images are described. Calculation of the images with the algorithm of low pass filtering show that the images can be decomposed into low frequency shadows and high frequency bright dots. The mutual correlation of the adjacent shadows can produce the two dimensional vector winds and then visualize the vortexes in the turbulence field. Meanwhile, the anisotropy in the turbulence field can be disclosed. Some scientific problems such as how to extract turbulence scalar parameters from the vector wind, and how to retrieve the structure of optical turbulence from the bright dots in the speckles combined with the principle of background oriented schlieren are proposed, which would be investigated in the next step.

Key words: atmospheric optical turbulence, fold pass laser transmission, 3M reflective film, laser speclcle, turbulence visualization