Higher-Order Aberration Measurement And Compensation Of 1.8-Meter Telescope

In the process of high resolution imaging of celestial objects,adaptive optics system plays an important role in the correction of atmospheric turbulence and the improvement of imaging quality.However,the adaptive optics system is in a certain condition between the two extreme situations,which are totally uncompensated and ful y compensated,belongs to partially compensated optical system.Adaptive optics can achieve almost full compensation for low order aberrations,but the compensation ability for higher order aberration is limited,higher order aberration that cannot be compensated using adaptive optical system is the main emphasis of this context.The research background of this context is a 127 elements adaptive optical system based on 1.8 meter telescope at Lijiang Observatory.Through measuring the higher order aberration of the original system,the influence factor of original 127 elements adaptive optical compensation system for far-field image quality is analyzed,such as the higher order aberration introduced by the deformable mirror,the static higher order aberrations in the main telescope optical path and the adaptive optical system.Finally through the method of image processing,we accurately compensate the static higher order aberration,so as to improve the quality of the far field imaging.At the same time,a systematic analysis of the various factors which could not be corrected by the under construction 4 meter telescope is presented.Specific work as follows:1.the analysis of the aberration sources in astronomical telescope impacting the performance of the telescope is presented,including the telescope system aberrations and the aberrations of adaptive optics system.The structure of the far-field image in adaptive optics and the imaging characteristics of the adaptive optics compensation are mainly analyzed,as well as the influence of higher order aberrations on the far-field image.2.The current performance and the existing far field image quality of the 1.8 meter telescope's adaptive optics system are systematically analyzed.For the demand analysis of the higher-order aberration measurement,we analysis the factors of impacting the aberration measurement accuracy in Hartmann wavefront sensor,design a Hartmann wavefront sensor for measuring the higher order aberrations of 1.8 m telescope.The higher order aberrations measurement scheme of the 1.8 meter telescope is determined.Due to the low order aberration and higher-order aberration measurement optical paths are not the same path,so the non common path aberration calibration is proposed,to accurately measuring the higher order aberration of the telescope system.The scheme of low order aberration and higher-order aberration measurement,and the higher order aberration measurement scheme of the system dynamic closed loop are presented.3.We build a higher order aberration measurement system of the 1.8 meter telescope.Through measuring the higher order aberration that cannot be compensated with the original 127 elements adaptive optical system,the static higher order aberrations of telescope optical path and adaptive optics system of the 1.8 m telescope is analyzed,as well as the higher order aberration introduced by the deformable mirror.The existing coverage of the 1.8 m telescope adaptive optics compensation is divided,and the far field image of higher-order aberrations with adaptive optics system compensation is simulated.Finally,we design the compensation system for higher order aberration of the 1.8 m telescope,through the image processing method to compensate the static higher order aberration,to improve the quality of the far field imaging.4.According to the requirements of the error budget of the 4 meter telescope,the aberration optimization control of the 4 meter telescope is designed.Simulation analysis of adaptive optics system layout of the 4 meter telescope is presented,the deformable mirror fitting error and the correction stroke of the deformable mirror are estimated.The ability for compensating aberrations of the adaptive optics system of 4 meter telescope is analyzed,including optical processing aberration,honeycomb mirror impression,alignment aberration requirements,the secondary mirror support bars,etc..and the whole system of adaptive optics is the residual static estimation.And the static residual aberration of the adaptive optical system in 4 meter telescope after compensating is estimated.