Nulling stellar coronagraph with an adaptive phase mask

2015 Fiscal Year Final Research Report

• Project/Area Number: 25610038
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Astronomy
• Research Institution: Hokkaido University
• Principal Investigator: BABA Naoshi 北海道大学, ―, 名誉教授 (70143261)
• Co-Investigator(Renkei-kenkyūsha): TAMURA Motohide 東京大学, 大学院理学研究科, 教授 (00260018) ; MURAKAMI Naoshi 北海道大学, 大学院工学研究院, 助教 (80450188) ; MIURA Noriaki 北見工業大学, 工学部, 教授 (30209720)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 光学赤外線天文学 / 系外惑星 / ステラコロナグラフ / ナル干渉

Outline of Final Research Achievements

Phase-mask coronagraph holds the ability to directly detect exoplanets. The problem here is that ordinary telescopes do not have perfect circular apertures but shades of a secondary mirror and spiders. It is known that shades of a secondary mirror and spiders deteriorate significantly the performance of phase-mask coronagraph. There have been proposed several ideas to overcome the deterioration. However, these ideas are based on using theoretically established phase-masks.
We developed a new kind of phase mask that would perform the contrast ratio of more than the tenth power of 10 for a circular aperture with shades of a secondary mirror and spiders. The phase distribution of the phase mask is numerically obtained by letting the leaked light outside the transparent part of the pupil. We applied the hybrid input-output algorithm, one of phase retrieval methods, to find the phase distribution of the phase mask. We showed the characteristics of thus obtained phase mask.

Free Research Field

天文光学