Optimization of starshades: focal plane versus pupil plane

摘要: We search for the best possible transmission an external occulter coronagraph that is dedicated to direct observation of terrestrial exoplanets. show better conditions are obtained when flux in focal plane minimized zone which exoplanet observed, instead total received by telescope. describe as a sum basis functions. For each element basis, we numerically computed Fresnel diffraction at aperture telescope and complex amplitude its focus. The functions circular disks linearly apodized over few centimeters (truncated cones). complemented numerical calculation these comparison with pure discs (cylinder) analytical expression, based on decomposition Lommel series, available. technique deriving optimal given spectral bandwidth classical regularized quadratic minimization intensities, but linear optimizations can be used well. Minimizing integrated intensity or selected regions leads slightly different transmissions occulter. optimization, resulting residual concentrated behind geometrical image occulter, blind region exoplanet, level background starlight becomes very low outside this image. Finally, provide tolerance analysis alignment also favors optimization.This means offsets decimeters do not strongly reduce efficiency