  We present the results of the first laboratory experiment of checkerboard
shaped pupil binary mask coronagraphs using visible light, in the context of
the R&D activities for future mid-infrared space missions such as the 3.5 m
SPICA telescope. The primary aim of this work is to demonstrate the
coronagraphic performance of checkerboard masks down to a $10^{-6}$
peak-to-peak contrast, which is required to detect self-luminous extra-solar
planets in the mid-infrared region. Two masks, consisting of aluminum films on
a glass substrates, were manufactured using nano-fabrication techniques with
electron beam lithography: one mask was optimized for a pupil with a 30%
central obstruction and the other was for a pupil without obstruction. The
theoretical contrast for both masks was $10^{-7}$ and no adaptive optics system
was employed. For both masks, the observed point spread functions were quite
consistent with the theoretical ones. The average contrast measured within the
dark regions was $2.7 {\times} 10^{-7}$ and $1.1 {\times} 10^{-7}$. The
coronagraphic performance significantly outperformed the $10^{-6}$ requirement
and almost reached the theoretical limit determined by the mask designs. We
discuss the potential application of checkerboard masks for mid-infrared
coronagraphy, and conclude that binary masks are promising for future
high-contrast space telescopes.
