The Establishment Of Dome Based On Simulated Star Sky And Fisheye Camera Calibration

With a large field of vision the fish-eye camera has been applied to astronomical navigation and positioning.Shooting to the ground target in the same time,it has the characteristics of imaging the starry sky information,which can solve the ground target astronomical azimuth.The accuracy of astronomical navigation and positioning depends on that of the parameters of the fish-eye camera.At present,the calibration of the fish-eye camera is mainly divided into indoor calibration method and star calibration method.Indoor calibration has small vision field.Star method has large vision field,but is vulnerable to the weather and atmospheric refraction.In view of the above shortcomings,this paper proposes to establish a 180 degree vision field of the indoor starry dome instead of outdoor star calibration field.Dome simulation star point direction accuracy is better than 5 angle seconds.The paper presents two kinds of fish-eye camera calibration model,with the azimuth angle calibration accuracy being less than 20 angle seconds,half-field angle accuracy being about 50 angle seconds,and the effective field of view being 165 degrees.The main work of the paper is as follows:(1)Introduced the basic knowledge of fish-eye camera calibration,such as fish-eye camera working principle,image processing and the existing two high-precision fish-eye camera calibration model-star calibration model based on the half-field angle constraints and vector calibration model.In addition,in order to apply to astronomical navigation,the paper also proposed a method of camera exposure time measurement,and the exposure time delay accuracy is better than sub-millisecond,with the difference of two measured exposure delay being about 3 ms.(2)The establishment of the field of view 180 degrees,10 meters in diameter hemispherical sky simulation dome,can provide the fisheye camera with indoor calibration field.In this paper,the Leica TS50 I telescope camera is calibrated to determine the relationship to telescope.Internal accord accuracy is about 0.5".(3)The TS50 I is used to capture the simulated star point image which angle and distance are measured to obtain the image positioning data.Calculate the location of the simulated star point,and finally all the stars compiled into a simulated star map.External accord accuracy is about 3".(4)In this paper,the coordinate transformation of the star map measured in different periods is carried out to maintain the accuracy of the star map,and the two-step coordinate transformation model based on the angle observation is proposed to improve coordinate transformation.(5)The Quaternion calibration method and the improved star calibration model are presented.The results of the two models are compared with that of the vector method.