Development of binary shaped pupil mask coronagraph for the observation of exoplanets

Direct observation of extra-solar planets (exoplanets) is essential to understand how planetary systems were born, how they evolve, and ultimately, to identify biological signatures on these planets. However, the enormous contrast in flux between the central star and associated planets is the primary difficulty in the direct observation. This has required stellar coronagraphs which can improve the contrast between the star and the planet to be developed. Of the various kinds of coronagraphs, we focused on a binary-shaped pupil mask coronagraph. The reasons for using this coronagraph are robust against pointing errors, essentially achromatic and relatively simple. We conducted a number of coronagraph experiments using a vacuum chamber and a checker-board mask, a kind of binary-shaped pupil mask, without active wavefront control. We demonstrated PSF subtraction is potentially beneficial for improving contrast of a binary-shaped pupil mask coronagraph, this coronagraph produces a significant improvement in contrast with multi-color/broadband light sources, and the new free-standing mask for practical use provides superior performance of improving contrast. We performed the tasks necessary to make the coronagraph fit for practical use. In conclusion, we carried out verification test for more real coronagraphic observations.