Optimal Design On Apertures Of Coronagraph And Analysis Of Influencing Factors

This paper focuses on a device for detecting exoplanets,the coronagraph,and innovatively proposes a two-step optimization that can optimize the two apertures called the entrance pupil and the Lyot stop in the coronagraph.The principle of optimization is to construct two optimization problems based on the order in which light reaches each plane,set appropriate constraints,and then solve the optimization problem step by step,and finally obtain the optimal transmittance of the entrance pupil and the Lyot stop.In this paper,this method is applied to the Lyot coronagraph and the Four-Quadrant Phase-Mask coronagraph,respectively,to explore the advantages and disadvantages of the two-step optimization method and its adaptability to different types of coronagraphs in multiple directions.When optimizing the design of the Lyot coronagraph with an amplitude mask,this paper finds that when the light from the telescope enters the optimized Lyot coronagraph,the results on the imaging plane show that both the stellar light and its diffracted light are strongly suppressed,and the contrast is also enhanced.The IWA(Inner Working Angle)of this coronagraph is 1.70?/D(which means it can eliminate 1e-10 of stellar light at 1.70?/D)in the case of light incidence with a central wavelength of 550 nm and a bandwidth of 10%,and it can detect planets with a light intensity of 1e-05 times that of the star near the diffraction limit(1.25?/D).In addition,in terms of solving speed,the optimization problem constructed by the two-step optimization method has relatively short solving time,which does not exceed 20 s at most.At the same time,in the production of the apertures,since the transmittance of the Lyot stop obtained by the two-step optimization is binary,compared with the gradual distribution of the Lyot stop transmission obtained by the joint optimization,the production process is reduced,so the requirements have greatly reduced costs.The Four-Quadrant Phase-Mask Coronagraph(FQPM Coronagraph)is a kind of exoplanet detection device that uses the principle of interference extinction to weaken stellar light.This thesis uses two-step optimization method carried out optimization work for its entrance pupil and Lyot stop,with stellar light and planetary light as incident light,and use contrast,Internal Working Angle(IWA)and other indicators to judge the optimized imaging quality.After setting appropriate optimization parameters,this paper obtained a FQPM coronograph with a contrast of 1e-06 at 1.25?/D and an average contrast of 1e-08 in the detectable region,and its throughput is kept at 40.01%.After that,on the premise of obtaining the optimal parameter setting scheme,this article changes the incident light to a bandwidth of 10% and a center wavelength of 550 nm to optimize the coronagraph.The results show that it can be achieved a contrast of 1e-06 at 1.25?/D,and the average contrast is 1e-08,but the throughput decreased slightly,being 29.04%.These data fully illustrate the efficiency of the two-step optimization method in designing the entrance pupil and the Lyot stop,and also prove that this optimization idea is a very important driving force for the development of the coronagraph.After the above simulation work,this paper found that the two-step optimization method is more suitable for the optimal design of the FQPM coronagraph.Based on the optimized FQPM coronagraph,the potential sources of error and the corresponding errors in the actual application process were explored.In the end,this article summarizes the research work done,and also raises some deficiencies,and gives a prospect of the future application of this method.