Square telescope and apodized coronagraph for imaging nonsolar planets and the like

摘要

A new coronagraph sufficiently increases the contrast ratio between the infrared image of a nonsolar star and a possible orbiting nonsolar planet to make imaging of such a planet possible. The coronagraph is used with an infrared telescope system having a square objective or aperture. Unwanted stellar irradiance is diffracted orthogonally by the square telescope aperture or objective so that a coronagraph apodizer in the first focal plane in the shape of crossed arms, and a coronagraph Lyot stop in the pupil plane with a square opening, stop most of the on-axis direct and diffracted stellar energy while allowing most of the planet irradiance to pass through the coronagraph. The discarded light reflected from the back of the apodizer can be used to provide information concerning piston and tilt errors of individual segments of a segmented telescope so that an array of correcting piston-tilt mirrors can be controlled to align the telescope.