High contrast optical system design for exoplanets imaging

Abstract

In this paper, a stellar coronagraph system with wavefront correct instrument is proposed, the optical design and image quality evaluation of the system are carried out, including the optical design of the front telescope system, the collimator instrument, wavefront correcting system in coronagraph and the optical design of the imaging lens. The front system used a structure of off-axis double-mirror telescope, with a diameter of 2.4m, 16 for F, and a FoV of 10 ×10 , The design requirements of the coronagraph instrument is: wavelength band is 450nm to 950nm, the detector is a EMCCD with the resolution of 1k×1k, pixel size of 13μm, the diameter of deformable mirror is 10mm. The design requirements of the imaging lens is: the optical aperture D is 5mm, F# is 15, the magnification of beam expander is 12.6 X. In this article, the coronagraph instrument system adopts the phase plate and the Lyot aperture and add the combination of the design and a deformable mirror is used to correct wavefront while a Lyot aperture is used for blocking the remnants of the star light, the introduction of the deformable mirror system can better eliminate both speckle noise and fixed optical surface error influences on imaging quality, also can correct the dynamic error.The design results show that: on the image plane, at the wavelength of requirement, the wavefront RMS value was less than 0.02λ, the result show that the wavefront error of the system reached the diffraction limit, it also means that the optical design of the whole system meet the design standard of coronagraph.