Co-phasing method for sparse aperture optical systems based on multichannel fringe tracking

To realize effective co-phasing adjustment in large-aperture sparse-aperture telescopes, a multichannel stripe tracking approach is employed, allowing simultaneous interferometric measurements of multiple optical paths and circumventing the need for pairwise measurements along the mirror boundaries in traditional interferometric methods. This approach enhances detection efficiency and reduces system complexity. Here, the principles of the multibeam interference process and construction of a co-phasing detection module based on direct optical fiber connections were analyzed using wavefront optics theory. Error analysis was conducted on the system surface obtained through multipath interference. Potential applications of the interferometric method were explored. Finally, the principles of the multipath interference process were experimentally revealed. Evidently, flat-field calibration and incoherent digital synthesis enhanced the fringe contrast to more than 0.4, with the dynamic range exceeding 10 times the working center wavelength (1550 nm). Moreover, a resolution better than one-tenth of the working center wavelength (1550 nm) was achieved. Simultaneous three-beam interference can be achieved, leading to a 50% improvement in detection efficiency. This method can effectively enhance the efficiency of sparse aperture telescope co-phasing, meeting the requirements for observations of 8–10 m telescopes. This study provides a technological foundation for observing distant and faint celestial objects.