Research On The Pyramid Wavefront Sensing Approach For Daylight Adaptive Optics

Adaptive optics is an optical technology that makes the optical system overcome the dynamic disturbance and provide diffraction-limited imaging by measuring and compensating the optical effects caused by optical media in real-time.After nearly 70 years of development,the application of adaptive optics has expanded from astronomical observation to many fields,such as human eye aberration detection,laser transmission,and space optical remote sensing.It has shown a very potential development prospect.As the "eye" of adaptive optics,the wavefront sensor uses the light of the target,or natural guide star or laser guide star in its iso-halo area to detect the dynamic wavefront aberration.Common wavefront sensors include the ShackHartmann wavefront sensor,pyramid wavefront sensor(Py WFS),and curvature wavefront sensor.Among them,Py WFS provides high sensitivity,high light energy utilization and real-time pupil sampling,which makes it more suitable for faint object detection.At present,Py WFS has been applied to many world-class ground-based telescopes.In this research,theoretical analysis and experimental research on pyramid wavefront sensing technology and its real-time application in daylight adaptive optics are carried out.The main research contents are as follows:1.The Py WFS is described theoretically and analyzed by numerical simulation.The performance of Py WFS in wavefront restoration and closed-loop correction is numerically analyzed to prove the feasibility of Py WFS in the adaptive optics system.2.An adaptive optical system based on Py WFS is designed and established.The dynamic range of Py WFS is found by experiments,and the closed-loop correction experiments are carried out.It is proved that the Py WFS can be applied to the adaptive optics system for high-precision wavefront detection.3.The principle analysis,optical modeling,and numerical simulation of the daytime-pyramid wavefront sensor(daytime-Py WFS)are carried out to verify its feasibility as a wavefront sensor.On this basis,the working performances of daytimePy WFS and other common wavefront sensors in real-time daylight object detection are compared.Daylight elimination algorithm is introduced in detail.The numerical simulation results prove that the daytime-Py approach can be applied for closed-loop correction in the daylight adaptive optics system.4.An daylight adaptive optics system based on the daytime-Py WFS is designed and built.The daytime detection ability of the daytime-Py WFS and usual Py WFS are compared.And the real-time closed-loop correction results using the daytime-Py approach and usual Py WFS under a low signal-to-noise ratio are compared and analyzed.The daylight real-time correction results using the daytime-Py approach with various pupil samplings and under various signal-to-noise ratios are presented,which illustrate the advantages of daytime-Py approach compared with the ShackHartmann wavefront sensor and usual Py WFS.Experimental results shows that the daytime-Py approach can be used as a new scheme for wavefront detection in the daylight adaptive optics system.In conclusion,pyramid wavefront sensing technology is comprehensively studied in this research.The working performance of Py WFS in the night adaptive optics system is deeply analyzed.And the application of Py WFS is extended to the field of daylight adaptive optics,which needs to be solved urgently.Daytime-Py approach is proposed,which means the Py WFS is firstly applied to the daylight natural guide star adaptive optics system for real-time detection in the visible.In addition,the working performance of the daytime-Py approach for daylight adaptive optics is comprehensively studied,and its advantages over the common wavefront sensors are analyzed.