Research On Techniques Of Coherent Laser Active Imaging And Tracking

With the constant changing of space situation, the need for the capabilities of imaging detection and identifying remote space objects is growing. Coherent laser active imaging technique can break through the traditional concept of imaging. By means of coherent laser active illumination and the reflected Fourier spectrum detection, the image resolution can be greatly improved and no longer restricted to the size of the receiver aperture. When reconstructing high-resolution images for various space moving objects, this imaging technique requires a high tracking precision even to a sub-arcsecond magnitude. However, the tracking system performance for distant objects will be reduced because of the effect of atmospheric turbulence. Precision tracking for space moving objects under turbulence become a key issue to be solved in coherent laser active imaging.Based on the study of coherent laser active imaging techniques, in this paper, the receiver detected energy formula of 3 beams imaging system was deduced. The spectrum information and spectrum distribution of objects, aperture position error, active tracking error which affect the laser active imaging quality were simulated and analyzed. In order to achieve the active tracking accuracy to meet the requirements of image quality, the outline of a ground-based laser active tracking system was proposed, the working principle of its APT(acquisition, pointing and tracking) system was described in details. The fine tracking unit was separated to research as a key technique. The relevant atmospheric theory and solutions of laser active tracking were elaborated. An indoor experiment platform of laser active fine tracking was designed and built. The tilted signal of wave-front which accords with the characteristic of atmospheric turbulence power spectrum was simulated. Adaptive optics technique was utilized for distortion detection and error correction. Experimental results show that application of fast moving mirror in fine tracking can effectively decrease the effects of turbulence and improve the tracking accuracy. Finally, the error of active tracking in actual system was analyzed.