中国科学院南京天文光学技术研究所机构知识库

We present the latest laboratory test of a new coronagraph using one step-transmission filter at the visible wavelength. The primary goal of this work is to test the feasibility and stability of the coronagraph, which is designed for the ground-based telescope especially with a central obstruction and spider structures. The transmission filter is circular symmetrically coated with inconel film on one surface and manufactured with a precisely position-controlled physical mask during the coating procedure. At first, the transmission tolerance of the filter is controlled within 5% for each circular step. The target contrast of the coronagraph is set to be 10^-5~10^-7at an inner working angle around 5λ/D. Based

on the high-contrast imaging test-bed in the laboratory, the point spread function image of the coronagraph is obtained and it has delivered a contrast better than 10^-6at 5λ/D. As a follow-up effort, the transmission error should be controlled in 2% and the transmission for such filter will be optimized in the near infrared wavelength, which should deliver better performances. Finally, it is shown that the transmission-filter coronagraph is a promising technique to be used for the direct imaging of exoplanets from the ground.