Research On Flat-Field Calibration Of Large-Aperture Astronomical Telescope Based On Subaperture Scanning

At present,astronomy and astronomical instruments have made tremendous progress.Large-diameter astronomical telescopes are increasing.The larger the telescope diameter,the stronger the light collection ability,and the weaker celestial bodies can be observed.The telescope has a higher spatial resolution and can be observed.To more details of celestial bodies.The precise calibration of large-diameter astronomical telescopes and terminal instruments is an important part in the development and operation.Improving the calibration accuracy is of great significance for the future development of super-large-diameter astronomical telescopes.In order to improve the accuracy of data acquisition,related ground calibration experiments are generally carried out,of which the most concerned is the flat field calibration,the purpose is to solve the non-uniformity of the image surface response.In this paper,a flat-field calibration method for large-aperture astronomical telescopes based on sub-aperture scanning is proposed.That is,at the entrance pupil of a large-aperture astronomical telescope,multiple sub-aperture scans are stitched together to construct a full-aperture illuminance data method.Field response non-uniformity calibration.Based on the theoretical analysis,this paper carried out the planning of sub-aperture and scanning path,selected and determined the illumination source form and radiance parameters of the collimated light source system,carried out the initial design of the collimating optical system parameters for calibration,and analyzed the sub-aperture stitching scan The influence of various errors on the uncertainty of the flat field calibration in the process,corresponding correction methods are proposed.The simulation model and experiment are used to verify the feasibility of the sub-aperture scanning flat-field calibration method,and to discuss the related technical issues of sub-aperture scanning method engineering.The main work of this paper includes the following parts:(1)Analyze the development status and flat field calibration methods of large-diameter astronomical telescopes at home and abroad,and propose a flat-field calibration method for large-diameter astronomical telescopes based on sub-aperture scanning.(2)Establish a mathematical model of sub-aperture flat field calibration to demonstrate the feasibility of the scheme.According to the comprehensive factors such as the technical parameters of the astronomical telescope and the exposure time,the sub-aperture scanning path with the number of scanning sub-apertures of 64 and the aperture size of 250 mm is planned,and the calibration efficiency of the scanning method is analyzed by the theoretical model and the calibration of the sub-aperture overlapping areas of different fields of view The impact of uncertainty.(3)According to the detection capabilities of the astronomical telescope and the planned sub-aperture parameters,complete the design of the calibration collimation system parameters.A double-glue collimating system is designed as a collimating optical system for flat-field calibration light source.Under the premise of meeting the aperture requirements,the field of view of the calibration collimating optical system is 2.2mm × 2.2mm,and the uniformity of its exiting beam Achieving 99.68%,the collimating optical system can provide a uniform light source for flat field calibration of large-diameter astronomical telescopes.(4)Analyze the sub-aperture scanning method to calibrate other error sources during the implementation of the flat field project,including the influence of the calibration light source stability on the image surface illuminance,and the detector noise,etc.,and propose corresponding correction or control methods.Secondly,in-depth analysis of the various error sources that affect the uncertainty of the flat field calibration,the synthesis uncertainty based on the sub-aperture scanning flat field calibration method is about 0.8%.(5)Completing the simulation analysis of the image field illuminance in the flat field calibration,importing the designed collimation system into the optical simulation software,the total illuminance at the entrance pupil of the full-aperture calibration system to be tested is 0.999999999999,and the sub-aperture scanning calibration is to splice the optical system to be tested The illuminance is 0.9999999999836,the illuminance is different.The off-axis 0.5 ° field-of-view sub-aperture one-by-one scanning and full-aperture scanning are different from the image surface illuminance of the system under test.The simulation data shows that the sub-aperture one-by-one scanning and the full-aperture scanning system image illuminance are basically equal.Caliber illumination information.(6)Under laboratory conditions,design shrinkage experiments to verify the feasibility of the proposed flat-field calibration scheme based on sub-aperture scanning.The sub-aperture size is selected as,the aperture of the optical system to be measured is,the number of sub-apertures is 9,and the sub-aperture scanning path is planned for flat field calibration experiment verification.Through simulation analysis,the difference between the image surface illuminance of the optical system to be tested and the sub-aperture stitching calibration optical system to be tested is 0.005,and the experimental verification results show that: using the sub-aperture to scan the image energy of the system to be tested and compare the full aperture The image surface illuminance restores the full-aperture illuminance information.The full-aperture image surface gray value is 231.085,the single sub-aperture gray value is 233.350,and the relative error is 0.75%.The sub-aperture scanning method can be used for flat field calibration of large-diameter astronomical telescopes.In summary,this paper builds an experimental platform through theoretical analysis and simulation modeling methods to study the content of more large-field astronomical telescope flat-field calibration,and solve the non-uniformity of the image surface response is important for the development of sky survey The significance of this provides a basis for future related research work.