Polarization Aberrations in an Unobscured Off-Axis Astronomical Telescope and Their Effects on Optics Ellipticity

Because of the continuously increasing detection ability in astronomy, polarization aberrations arc playing increasingly important roles in the performance of astronomical telescopes. In this paper, the polarization aberrations of an unobscured off-axis astronomical telescope used to detect weak gravitational lensing effect arc analyzed using polarization ray tracing. The diattenuation map and retardance map of each mirror for the telescope arc obtained, and both its Jones pupil and amplitude response matrix arc determined. It is found that the polarization aberrations of the telescope have an impact on both the imaging contrast and the spatial distribution of the point spread function (PSF). The optics ellipticity of the telescope is analyzed. The variations of optics ellipticity, which arc dependent on the field of view ( FOV), arc induced by polarization aberrations. The maximum and mean variations of the optics ellipticity in all FOVs arc 7. 5 X 10(-3) and 2.7 X 10(-3), respectively. At the FOV [ O. 0187, 0.155], the maximum ellipticity interpolation error increases from 1. 2 X 10x to 1. 1 X 10(-3). Our analyses reveal that polarization aberrations should not be ignored and should be optimized in telescopes that require ultrahigh imaging performance, such as those used for detecting weak gravitational lensing effect.