  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.
