Field diversity phase retrieval method for wavefront sensing in monolithic mirror space telescopes.

To guarantee the uniqueness of the solution for the wavefront phase, a series of intensity images with known phase diversities is usually needed in the current phase retrieval wavefront sensing methods. However, to obtain these intensity images with deliberately added diversity phases, some additional instruments (e.g., beam splitters) or operations (e.g., adjustment of the focus) are usually needed, which can pose a challenge for wavefront sensing in space telescopes. This paper proposes a new concept for retrieving the wavefront phase of monolithic mirror space telescopes with perturbations, where the intensity measurements with phase diversities are directly obtained from different field positions of one image, without the need for any additional instruments or operations. To realize this new concept, we present a modified phase diversity method to account for the unknown phase diversities between these intensity measurements based on an in-depth understanding of the net aberration fields induced by misalignments and figure errors. Relevant simulations for different cases are performed to demonstrate the feasibility and accuracy of the proposed method. Since in this method the phase diversities between different intensity measurements are mainly induced by the diversities in the field position, we call it the field diversity phase retrieval method. This work can present great facility for wavefront sensing in monolithic mirror space telescopes.