Research On Co-phasing Method Of Synthetic Aperture System Based On Pyramid Sensor

Theoretical research shows that the resolution of a telescope is determined by its aperture.With the continuous improvement of production and living needs and research levels,in order to carry out astronomical observation and research more clearly and efficiently,numerous scholars have gradually improved the structure and technology of telescopes,and the function of telescopes has been continuously improved.They are playing an increasingly important role in many fields such as science and technology,national defense,production and life.Limited by such factors as surface accuracy,processing and transportation,and manufacturing cost,8m diameter is the aperture limit of single mirror telescope at this stage.It is bound to become the development trend of large-scale optical telescope system in the future to adopt several small aperture sub-apertures equivalent to a large aperture synthetic aperture telescope imaging system.However,the structure of the synthetic aperture system also introduces a problem.There are some degree of misalignment errors among the sub-apertures,which must be aligned and phase adjusted by active control to obtain the same spatial resolution as the equivalent single mirror.The synthetic aperture telescope systems currently in operation are equipped with error compensation correction systems suitable for themselves to ensure that the telescope system can work efficiently according to the established technical specifications.This process is called co-phasing.Pyramid sensors have a wide application prospect due to their advantages in spatial sampling rate and light energy utilization.This paper focuses on the co-phasing method based on pyramid sensor,mainly in the following areas:1.Based on the limitation and bottleneck of telescope development,this paper introduces the solution of synthetic aperture system,summarizes the current development of synthetic aperture system,points out that the key to achieve the designed imaging index of synthetic aperture imaging system is to realize the co-phasing among all sub apertures,and enumerates and expounds several mature co-phasing methods at present.2.Starting with Fourier optics,the reason why synthetic aperture system can improve imaging resolution is analyzed mathematically,and the misalignment error that is critical to imaging quality in the solution of synthetic aperture imaging system is pointed out.The influence of co-phasing error on synthetic aperture system imaging is analyzed,and the influence of tip/tilt and translation error of sub-aperture on PSF and far-field spot is simulated by MATLAB,Seelight and other platforms.3.This paper introduces the working principle of the pyramid sensor in the wavefront detection of the single lens telescope,and proposes that the co-phasing error can be detected by a simple sinusoidal relationship between the signal and the error.The simulation verifies the change of the detection signal of the pyramid sensor when there is a co-phasing error and the curve relationship between the error and the signal,and proves the steps of the detection and correction of the co-phasing error of the pyramid sensor.These simulation analyses provide a theoretical basis for the design of the following experimental system.4.Based on the existing instruments and resources in the laboratory,the co-phasing experiment system of the pyramid sensor is designed and built.The signal error curve of the pyramid sensor is experimentally fitted,and the co-phasing experiment based on the pyramid method is carried out under the 2 sub-apertures and7 sub-apertures synthesis modes of the segmented mirror.The experimental results show that the co-phasing method based on the pyramid sensor can effectively reduce the misalignment error of each sub-aperture and significantly improve the imaging quality.The error in the experiment process is analyzed and considered,which provides support and foundation for future work.