Techniques for measuring the spectra of the statistical distribution of scintillation, spread, or spot dancing, and their applications in remote sensing

We propose a technique for measuring the statistical distribution spectrums of scintillation, beam spread, and spot dancing. The intensity of the laser beam is directly converted into the amplitude of photoelectronic pulse and fed to a multichannel analyzer. And by using the beam width (or displacement)-time- amplitude conversion technique, the statistical spectrums are determined rapidly. In the system the spectrums of scintillation, spread, and spot dancing may be simultaneously measured in a sampling rate of 3,000/s. The measurement precisions predicted are of 0.5% to amplitude, of 3 micrometers to width and of 5 micrometers to spot dancing in the laboratory static air. When a laser beam passes through the turbulent atmosphere, several effects induced by the turbulence would be met. They are intensity fluctuation (scintillation), intensity distribution (speckle), beam spread, spot dancing, and phase fluctuation. But in view of the physical measurement, the measurements of the intensity fluctuation and distribution depend on the detection of light intensity and on the position of beam. And beam spread or spot dancing will be determined by a beam cross-section and a displacement respectively. However, the measurement of phase fluctuation is essentially related to the wave propagation time varied along the path in the turbulent atmosphere. Therefore it only needs three physical parameters to be measured, which are amplitude, length, and time.