Research On Transmission And Pointing Control Of Laser Beam In Vibration Environment

The optical axis of the optical systems which are excited by the vibration of environments would deviate from the ideal direction. This phenomenon causes misaligned optical systems and the decrease of the light beam pointing stability. As in the classical optical systems, the vibration is small and the optical lens have small volume and high stiffness, the rigid body displacement of optical lens is considered to be the only reason for the optical axis deviating in beam transmission classical method of calculation. However, the influence of optical axis deviation caused by the elastic deformation of optical lens on the beam pointing could not be ignored, when the vibration excitation is large or the stiffness of the optical lens is low. In order to improve the beam pointing stability of the precise optical systems in vibration, the method of beam transmission calculation and beam pointing control should be investigated considering elastic deformation of optical lens. Three aspects including theory, simulation and experiment, have been used to study the method of beam transmission calculation and the problem of beam pointing control in vibration. The main work is shown below.1. The novel direct vector analysis method for beam transmission has been proposed in vibration.(1) The novel direct vector method for ray tracing has been proposed. The position and direction of arbitrary beam are described by this method. The equations of optics laws are gained by this method.(2) The vector calculation method for reflection and refraction has been built. The beam transmission calculation method for coaxial and misaligned optical systems has been proposed.(3) Beam transmission calculation method considering the elastic deformation of optical lens has been proposed. The results of beam transmission calculation with the elastic and rigid optical lens have been compared with each other. Beam transmission calculation method considering the elastic deformation of optical lens is tested to be effective.2. The beam pointing control method based on active optical stages in vibration has been proposed.(1) The linking relation of a type of optical stage has been analyzed. The continuous contact force model of the thread pair has been deduced basing on the contact theory of Hertz and the nonlinear model of Hunt&Crossley. What’s more, the dynamic model of the optical stage is improved by introducing the continuous contact force model into the dynamic model.(2) An active optical stage for beam pointing control is designed basing on a type of optical stage. A generalized Prandtl-Ishlinskii model for modeling asymmetric and rate-dependent or rate-independent hysteresis of a piezoceramic actuator is presented. The results show that the hysteresis model of this paper can fit the hysteresis curves at different frequencies well.3. An active controller for beam pointing has been designed in vibration.(1) A four-input fuzzy control method is proposed. Basing on the classic fuzzy control method, the integral of the system error and the second-order differential of the system error are introduced into the input of the fuzzy controller. The integral of the system error is conducive to eliminating the static error, while the second-order differential could decrease the overshoot and keep the control speed fast. The fuzzy inference which is fit for the four-input fuzzy control method is proposed. What’s more, the four-input fuzzy control proved to be the general condition of the classic fuzzy control.(2) The controller of the active optical stage and the controller of the FSM have been designed. The control method of two level control with the active thread pair actuators and the FSM has been proposed.(3) A controller with four-input fuzzy control with variable structure is built up with the active thread pair actuators and the FSM in the optical stage system.(4) The controller of the active optical stage and FSM has been designed. It is proved that two level control with the active thread pair actuators and the FSM is conducive to the development of the control effect.4. The experiment system of beam pointing control has been built in vibration.(1) An experiment platform for optical measuring and control has been built. The experiment platform can achieve the simulation with hardware in loop and position measure of the light beam. An immaculate laboratory for optical vibration control is built.(2) The simulation results of the optical stage dynamic model is proved to be agreed with the experiment results.(3) By the experiment of beam pointing control, the active control effect of the thread pair actuators is proved to be effective. It is verified that the vibration control combining the thread pair actuators and the FSM could gain more precise results.The novel direct vector analysis method for beam transmission has been proposed in vibration. A set of methods for coaxial and misaligned optical system calculation has been proposed. The methods are theoretical. What’s more, an active control system for beam pointing has been designed in vibration. The beam pointing control method based on active optical stages in vibration has been proposed. Then the control method is tested by an experiment and the results show that the effect of the beam pointing control is well. The research findings of this paper have construction values on laser communication and large telescope.