Large Viewing Field Wavefront Sensing By Using A Lightfield System

The terrestrial atmosphere degrades the telescope images due to the refractive index changes caused by atmospheric turbulence. To take advantages of the large-diameter telescope for high-resolution imaging of extended targets, it is nece ssary to detect and compensate atmospheric turbulence induced wavefront distortion. Shack-Hartmann wavefront sensor is currently the most widely used wavefront measuring method in adaptive optical system, which enforces the size of the region in the aperture directly by placing a lenslet array in the aperture plane. To overcome the shortcomings of Shack-Hartmann wavefront sensor, we developed a lightfield wavefront detection system, which is able to complete the large field of view by multi-perspective wavefront detection in a single photographic exposure. It is a new method for large viewing wavefront detection and correction, despite that the requirement of system’s alinementThis paper begins with the the background and meaning of large viewing field wavefront detection, and introduces the current development of wavefront detection. Then summarizes the tasks should be resolved in wavefront detection, introduces the characteristics of lightfield camera and demonstrates the principle of the configuration. By comparing the Shack-Hartmann wavefront sensor with the lightfield wavefront detection system, we clarify the advantages of the newly developed system for large viewing wavefront detection of extended target, as well as the method for realization. Then a wavefront detection theoretical model is bult up, the program is compiled independently, and numerical simulation is performed to judge the validity of wavefront restoration arithmetic.In the last, experiments are carried out to validate the system. A lightfield camera system is designed and built up based on the conditions in lab. The wavefront detection system is set up and the system’s initialized collation is performed. The primary experiment on feasibility on wavefront correction is accomplished, and t he software on wavefront slope extraction is composed for the following system. The wavefront detection is simulated in lab employing two pararrel light passed through phase plane, the wavefront detection is performed using the self- made wavefront detectio n system. The results show that the dectection is effective and thus approve the feasibility of this syetem in wavefront detection. The system can be improved in configuraion to have the same effects obtained via Shack-Hartmann wavefront sensor. Meanwhile, since this syetem detects the space frequency at separate areas and has no requirement on the beaconing, point beaconing and extended beaconing can both be detected effectively, and different perspective wavefront informations can be obtained through only one image collecting, which are unable to achieve by Shack-Hartmann wavefront sensor.This wavefront measurement method can realize the multi-perspective wavefront measurement, which is expected to solve the problem of large viewing field wavefront detection, and can be used for adaptive optics in giant telescopes.