Phase apodization coronagraphs are implemented in a pupil plane to create a dark hole in the science camera focal plane. They are successfully created as "Apodizing Phase Plates" (APPs) using classical optical manufacturing, and as "vector-APPs" using liquid-crystal patterning with essentially achromatic performance. This type of coronagraph currently delivers excellent broadband contrast ($\sim$10$^{ -5}$) at small angular separations (few $\lambda/D$) at ground-based telescopes, owing to their insensitivity to tip/tilt errors.
Categories: astro-ph.IM