Offline assembly of the lobster-eye x-ray telescope based on optical reference transfer

To address the difficulty of focal alignment and optical axis calibration of lobster-eye x-ray telescopes in the absence of an x-ray vacuum environment, an offline visible-light alignment method based on optical reference transfer under atmospheric conditions is proposed. The detector assembly consists of four complementary metal oxide semiconductor (CMOS) sensors assembled into a quasi-spherical focal surface. By monitoring the optical markers, the position and orientation of each CMOS sensor are finely adjusted to achieve precise matching between the imaging surface and the focal plane. Cube mirrors are mounted on both the detector and optical assemblies, enabling accurate optical axis and focal plane alignment using theodolites and a laser tracker. Test results show that after alignment, the angular resolution of the system exhibits less than 5.36% variation compared to component-level tests, and the field-of-view shows less than 0.1% change. These results verify the high precision and feasibility of the proposed alignment method, providing an effective technical approach for ground-based integration of wide-field x-ray telescopes.