Experimental Investigation Of Nodal Aberration Theory In Misaligned Reflective System

Nodal aberration theory(NAT)describes up to fifth-order wave aberration in optical system without symmetry,which has significant application value in engineering.For one aspect,NAT could quantify the wave aberration in perturbed coaxial optical system and guide its alignment.For another aspect,NAT could guide the optical design in off-axial optical system and optical system with freeform optics to prompt their development.However,NAT was fully described mathematically and investigated through real-ray tracing software,but an experimental investigation is yet to be realized.Aim at this blank area,an experimental investigation of NAT is developed with a customized Ritchey-Chrétien telescope in this dissertation.The main content includes:1.Based on the first-order property and third-order wave aberration theory in twomirror reflective system,the shifted aberration field center and third-order coma and astigmatism field in perturbed two-mirror reflective system was deduced by using NAT on the experimental object-Hilbert telescope which is a RitcheyChrétien system.Real-ray tracing was utilized to analyze the third-order aberration field in Hilbert telescope which is a preface to the experiment.Comafree pivot point was discussed and calculated by first-order property in twomirror reflective system,and the coma-free pivot point of Hilbert telescope was given.2.Based on experimental requirements of the investigation of aberration field in perturbed two-mirror reflective system,a hexapod was adopted to support the secondary mirror assembly in Hilbert telescope.The mechanical design and Finite Element Analysis was developed,the analysis shows the structure is stable and meets requirements.To the nodal property of third-order coma,an experimental setup which includes a field generator and a retro-reflector was designed,assembled and aligned.Several sampled field points were measured interferometrically without moving the telescope and the interferometer.The fringe pattern of third-order coma was simulated by using real-ray tracing and Fringe Zernike polynomials.The simulation conforms to the prediction of NAT.Measurement data was collected according to the experimental method.The accuracy of the Fringe Zernike fit and the statistics of the measurements were analyzed.In the tolerance of errors,the measurements conform to simulation.The experimental investigation of third-order coma in NAT was fully completed.3.A theoretical analysis on nodal property of third-order astigmatism in Hilbert telescope was developed.Based on the theoretical prediction,null testing was done to primary and secondary mirror.With testing results,simulation on the astigmatism nodes were given which indicated the experiment setup was not capable to investigate third-order astigmatism for Hilbert telescope.Suggestions were given on the improvement of the experiment.Experimental investigation of NAT on perturbed two-mirror reflective system was developed in this dissertation,which is significant to the development and completeness of NAT.