Research On Direct Monitor And Correction Methods For Emitted Direction Of Multi-wavelength Laser Beam

State-of-the-art laser transmitter systems at home and abroad arecharacterized by fast structural response, accurate pointing, and strong resistanceand so on, further presently developing in the direction of high-energy andmulti-band. Compared with the predictable directions, the lasers emitted from thelaser transmitter systems have some certain deviations due to many factors likeexternal environments and internal structures for example. For the sureness ofalignment accuracy of laser transmitter systems the directions of laser beams arenecessary to be monitored and then the generated pointing errors are necessary tobe corrected.In the design of system scheme, the errors of which laser beams travels fromthe light outlet of lasers through before the monitor system are to be analyzed byemploying the homogeneous coordinate transformations. Furthermore, themathematical model and sensitivity matrix both established provide theories forconducting the monitor and correction of beam directions. In comparison of theshortcomings in previously indirect monitor approaches, a novel scheme of directmonitor is proposed and the research plan is designed.In the monitor of laser beams, the time division monitor, a scheme of directmonitor, is designed to realize the direct monitor of emitted directions of long andmiddle laser beam waves by the same monitor system. A set of optical lenses is devised, according to the collection requirements the four quadrant detector putson light spots, to make sure to image on the target surface in suitable dimensionsand positions after two sorts of infrared laser beams travel from the lenses. Also,based on ellipse light spot model a spot center positing algorithm is proposed. Thelong and short axes parameters of ellipse spots are obtained through employingthe orthogonal tiny motion algorithm.In the correction of laser beams, a new kind of fast steering mirror isdesigned to apply into the correction system. Upon the present structures it is thefirst time to use flexible hinges in two-axis fast steering mirror. After adopting thesequence of two quadratic programming methods, critical dimensions of hingesare optimized. Then, theoretical calculations and simulation analyses are carriedout in the transmission accuracy of system motions.With researching respectively on the monitor and correction of long andmiddle wavelength paths, the relations established between the center positions ofspots received by the four quadrant detector and the rotating angles of fast steeringmirror provide theoretical guidance for the closed-loop control of monitor andcorrection systems of laser beams.Through the pointing accuracy experiment in monitor system, the accuracy ofmonitoring laser beams is testified as2’’. And then, the feature experiment of faststeering mirror verifies the accuracy in which the correction system controls thedirections of emitted laser beams as0.95’’. The research work also gives theclosed-loop transfer function of fast steering mirror, making sure that the firstnatural frequency of system is out of the working frequency by experiment. Takethe experiment of the monitor and correction system of long wavelength laserbeam directions as the example, the experimental results show that the designedsystem can monitor and correct the accuracy of direction shift of laser beams to2’’.The synthesis of every experimental result validates the monitor and correctionsystems in which it combines the monitor of laser beam directions and the faststeering mirror is capable of achieving fast detections and adjustments of laser beam directions in the multi-band laser transmitter system. Finally the designedscheme is feasible and the correction accuracy is reliable.