The Assembly Accuracy Analysis And Alignment Optimization Of Coaxial Optical System

Coaxial optical systems are the core components of many opto-mechanical systems.At present,high imaging quality of coaxial optical systems is required in aerospace and photolithography technologies.The optical axis consistency condition would be destroyed by optical centering errors caused by machining and assembling process.Optical centering errors should be controlled by optical alignment.Due to traditional alignment method's low precision and efficiency,it is gradually replaced by the computer aided alignment(CAA).However,coaxial optical system has many elements,complex assembly relationship,and are greatly influenced by joint surface error.What's more,the CAA technology in the narrow sense of the word which is suitable for simple off-axis optical system cannot solve the alignments of coaxial optical system.Therefore,researching alignment method for coaxial optical system is of great significance for improving the performance of imaging quality and shorting the alignment cycle.This research is mainly based on the optical centering errors,and by controlling the assembly accuracy of the typical coaxial optical system to optimize the assembly process.Firstly,in view of the typical structure of coaxial optical system,the definition of centering fiducial axis transfer path was proposed to be a carrier for analyzing how joint surface error affect optical axis tilt error,and the alignment thought based on global optimization alignment method for the compensation of optical axis tilt error was put forward.Secondly,method for describing surface error of part was analyzed.Least Square Method was conducted to fit the ring assembly plane of cylinder part as practical assembly plane and the error measuring method was analyzed.Based on the homogeneous coordinate transformation method,transformation matrixes were set up to describe machining error of a single part and assembling process error between adjacent parts,and the calculation model of the angle between optical axes,which was a function of relative load angles.Then,according to the transfer path type,the optimization models taking the minimum angle between optical axes as the objective function and their optimization algorithm like genetic algorithm was obtained.Using MTF to be the imaging quality evaluation standard,on the basis of sensitivity analysis method,sensitive optical axis tilt errors were determined,thus some sub-transfer paths were obtained by resolution and optimized order of angles between optical axes was designed,and then an appropriate set of relative load angles were obtained and the method of solving the error range of them were proposed.Finally,the detailed operation procedures of an alignment method of coaxial optical system were proposed.Through simulations of a projection objective to perform analysis and verification by the use of Zemax and MATLAB,it was verified that optical axis tilt errors could be compensated by global optimization alignment method using machining errors of parts,and the feasibility and practicability of this method and calculation model were verified.