Research On Fast Scanning Technology Of Rotating Double Prism

Beam scanning technology based on rotational double prisms(RDP)is a technology of precise control and positioning of beam pointing through a pair of wedge-shaped prisms coaxially and independently rotating,with the characteristics of large scanning range,high pointing accuracy,and high response frequency.It is widely used in laser radars,infrared countermeasures,industrial measurement and other fields.The major premise for the application of the rotational double prism is to calculate the mathematical relationship between the target direction and the rotation angle between the two prisms.During the entire scanning process,the RDP does not need to turn around,adjusting the speed ratio and angle difference and rotating the prism group in the same direction can realize the scanning of different patterns.However,the complex optical characteristics of the prism make the process of accurately calculating the relationship complex and time-consuming.For the contradiction between the efficiency and accuracy of the accurate solution process,a prism solution optimization technology based on error fitting is proposed,which is suitable for the forward and reverse solution problems of rotational double prisms.While ensuring accurate solutions,significantly improve the efficiency of the calculation.The simulation results show that the accuracy of the optimization method based on error fitting is equivalent to that of the non-paraxial ray tracing method,reaching the order of 10^-3?,but the time-consuming is only 1/20 of non-paraxial ray tracing method.By controlling the two prisms to rotate in the same direction,the reciprocating spiral scanning mode can be realized,which can meet the indicators of controllable field of view,controllable coverage,controllable period,and stable speed.Experimental results show that this scanning method takes into account the above indicators.During the entire scanning process,the DRP does not need to turn its head,but continuously rotates in one direction,and the servo error is controlled within 3".However,due to the limitation of the scan track setting and the maximum speed and acceleration of the motor,there is still a certain sudden change in the speed of the prism,causing excessive servo control errors near the maximum opening angle and the minimum opening angle.To solve this problem,the method of combining filter and interpolation is used to optimize the scanning trajectory.This method has a good effect in suppressing the sudden change of prism speed.It reduces the servo control error caused by the sudden change of speed,from about 1100"to 350",reducing to t1/3 of the original.In this paper,the beam pointing model of the RDP is established,which is based on the solution error in the approximate solution and the accurate solution method.By means of error-fitting,the approximate solution method is compensated,which simplifies the prism solution process.In the follow-up work,it can be combined with the fast high precision servo control system to improve the research on fast scanning technology of DRP.