Testing of a high-contrast imaging coronagraph based on an active liquid crystal array

Abstract

Liquid crystal modulator is an active optical component that is promising to replace traditional passive optical components. For high-contrast imaging coronagraphs that are used for direct imaging of extra-solar planets, passive coronagraph optical components are often adopted. It is impossible to actively optimize such a coronagraph system to achieve its best performance. Thus we’ve proposed a novel high-contrast imaging coronagraph which uses a liquid crystal array (LCA) for pupil apodizing. In our test, the LCA is well calibrated for amplitude errors and amplitude nonuniformity with the entire coronagraph optics. Close-loop compensations are applied according to the amplitude calibration results. By doing so, a contrast of 10 -4 or 10 -5 can be achieved in an angular distance down to 3~5λ/D, which can be used for the direct imaging for young and Jupiter-like planets. The contrast can be further improved if a deformable mirror (DM) is deployed to correct wave-front errors induced by the LCA and the coronagraph optics.