Principle And Feasibility Of Using A 3m Reflective Film Based Fold Pass Laser Speckle Imaging System For Measuring Atmospheric Optical Turbulence

The idea of projecting a laser beam onto a large area microcrystalline reflective film (3M film) for the visualization and measurement of atmospheric optical turbulence was proposed and investigated. The fold pass propagation of a laser beam by the reflection of a 3M film was theoretically analyzed and numerically simulated, which uncovers that the mechanism of bright dots, random in shape, brightness, and position, appears on the received laser speckle images. Experiments were performed to get the phenomena and explore the applications of the idea. An easy to implement laser speckle imaging system was set up for the qualitative experiments. As the result, the image of laser speckle patterns characterized by random dots and movable shadows were recorded, and the two-dimensional path averaged transverse wind field was retrieved. Also, a high-performance laser speckle imaging system cooperated with two professional optical turbulence monitoring instruments was set up for the qualitative experiments. Using the image data recorded in a clear sunny day, the probability distribution, spatial correlation coefficient, and scintillation index of the light intensity on the laser speckles were estimated. Meanwhile, the refractive index structure constant, aperture averaging factor, and inner scale of optical turbulence field were retrieved and compared with the monitored values and theoretical expectations. All the results are reasonable, which reveals the possibility and verifies the feasibility of using a fold pass laser speckle imaging system for optical turbulence research. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement