Controller Design Of Microposition System In The Large Diffraction Grating Ruling Engine And Research On Correction Diffraction Wavefront

Diffraction grating,which is nano-precision optical component with excellent optical functions such as polychromatic light dispersion,polarization,and phase matching,is important optical elements in many fields,such as,defense,military,aerospace,astronomy,civil use and so on.Manufacturing technology for the diffraction grating is one of the most sophisticated technologies.For the strict shape shape of the grating groove,the infrared gratings and most of the echelles are ruled by mechanical method in general.The positioning accuracy of the grating ruling engine is a prerequisite for the manufacture of high quality diffraction gratings.The wavefront quality of the grating is an important optical performance index of the grating,which affects the spectral imaging characteristics of the grating.In this case,the manuscript which is funded by National R&D Projects for Key Scientific Instruments and 973 project,that is focused on improving the quality of ruled gratings and explore the method to improve the positioning accuracy of the ruling engine and correct the diffraction wavefront in gratings.Analyze The structure and working principle of the mechanical system of the grating ruling engine is analyzed;The controller of microposition system is designed;The effects of the ruling line error caused by the measurement system and the uniformity of the grating coating on the influence of the basal surface shape on the wavefront of grating diffraction are studied.First,the groove error model is established,the groove error is distributed,locator positioning accuracy index is given.To demonstrate the rationality of the large diffraction grating design,the mechanical structure,mechanical precision and operation principle of the mechanical system of the large diffraction grating ruling engine are analyzed.Secondly,a mathematical model of the micro-positioning system is established using the "gray box" modeling method.Through the study of the characteristics of the mathematical model,a compound controller including PID control and feedforward control is designed.Through simulation and experimental research,it is verified that the designed controller satisfies the requirements of the nanometer positioning of the grating scribing machine.Thirdly,the relationship among groove error,surface error and diffraction wavefront under condition of cone diffraction is deduced.Fourthly,the measurement optical path of the large diffraction grating ruling engine is designed.The reason of the cosine error caused by the optical path structure of the existing measurement system is analyzed,and the method to reduce the cosine error of the measurement system is proposed.Fifthly,the causes of the Abbe error caused by the optical path structure of the existing measurement system are analyzed.The mathematical model of the Abbe error and diffraction wavefront quality of the measurement system is established and analyzed.The measurement and correction method of the Abbe error of the measurement system is proposed.The feasibility of the proposed Abbe error measurement and correction method was verified by experiments.Sixth,the influence of the air environment error of the large diffraction grating ruling engine on the refractive index of the measurement system is analyzed.The measurement method of the atmospheric refractive index is proposed.The mathematical model of the groove error caused by the refractive index of the air and diffraction wavefront quality is established.The feasibility of the proposed the refractive index of the air measurement and correction method was verified by simulation analysis and experiments.Seventh,combined with the working principle of the coating machine,the cause of the non-uniformity of the coating is analyzed,the film uniformity formula of the different coating areas is deduced,and the mathematical model between coating uniformity and grating diffraction wavefront is established.Through the theoretical analysis of the coating uniformity,the structural parameters of the coating machine are adjusted so that the uniformity of the coating layer meets the requirements of the index.The influence of coating homogeneity on the wavefront quality of the diffraction grating is simulated and analyzed.The grating ruling experiments demonstrate that the improvement of the plating uniformity of the film layer effectively improves the diffraction wavefront quality of the grating.