| With the complex micro-structures on the surface,the continuous phase plate is able to realize the uniform distribution of far-field energy in the inertial restraint system,but also bears the risk of laser-induced damage.Therefore,it is necessary to periodically replace it to ensure the normal operation of the whole system.However,the characteristics such as deep removal and steep gradient make the fabrication of continuous phase plate a major technical problem in the field of optical manufacturing.The atmospheric plasma processing technology is based on chemical reactions to achieve high-efficiency processing without introducing subsurface damage with a low maintenance cost and no reduction in damage threshold of optical components.So far,it has been applied in continuous phase plate processing,yet the process and the error analysis are still not mature enough.Thus,this paper will carry out systematical analysis of parameter optimization and the error source during the atmospheric plasma process,which will lay a theoretical and experimental basis for the high-precision and high-efficiency manufacturing of continuous phase plates.Firstly,this paper explores the influence of different numerical control parameters on machining error through theoretical simulation.Based on the sampling theorem and spectrum analysis,the range of each numerical control parameter is clarified.Besides,the orthogonal test is designed to investigate the effects of the parameters on the surface shape error and the processing time.Finally,the combination of numerical control parameters is optimized considering the processing accuracy and time,which provides a clear and reliable procedure for the experimental and theoretical research of any given target surface.Error analysis has a high demand for the precise match between the processed surface and the target surface shape.The rough-fine matching method is investedgated in this chapter.First,the rough mathcing is realized through manually selecting the feature points.Then,the iterative nearest point algotithm is induced for the fine mathcing.By aligning the surface shapes with different frequency components before and after some random spacial transformations,such as the sinusoidal mesh surface and the continuous phase plate surface,the matching error is only the10-1510-14 magnitude of the ideal surface PV value,which verifies the accuracy of the matching algorithm.After that,a MATLAB-based surface matching software is developed to routinize the matching process and greatly improve the data processing efficiency.Finally,according to the above research,a series of experimental studies are systematically carried out and the effects of removal function on the maching error are analyzed.To be specific,the stability,nonlinearity and consistency of the removal function have an increasing effect on the surface shape error,which can reach 300 nm RMS at most.Through the optimization of numerical control parameters,perfect calibration experiments and algorithm compensation,two430mm×430mm×3mm continuous phase plates are fabricated within 13.6h,and the surface error is optimally 160nm RMS and 1?m PV.The error is believed to mainly come from the consistency variation of the removal function,which verifies the rationality and reliability of the error analysis in continuous phase plate processing based on atmospheric plasma technology and confirms the necessity of iteration process for improving the processing precision. |
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