Photonics Scanning Pentaprism System for the Integrated Inspection of Large-Aperture Telescopes

Abstract

To improve their spatial resolution and detection capabilities, future ground-based optical telescopes will have a size of 30 m, and the aperture of space telescopes will be increased to 10 m. Such large optical systems necessitate the development of large integrated testing equipment. In this study, spectrum and system alignment measurements and wavefront quality checking were performed using the sub-aperture detection method and a fiber-connected Photonics Scanning Pentaprism (PSP). First, the system was aligned using an optical truss, ensuring that the optical axis was properly positioned. Second, using a sub-aperture light beam though the entrance pupil, light spots were formed on the focal plane and transmitted to the spectrometer via fibers to obtain the corresponding spectral components. Then, by taking measurements at different system positions, a full-aperture spectrum response could be reached. Lastly, by photon-integrated interference on the focal plane, intensity interference fringes could be projected at the entrance pupil of the system. And the wavefront quality of the system could be verified by observing the fringe deformation. The measurement accuracy of the optical axis of the system is better than 2 mrad. The spectral measurement accuracy was better than 5%, and the wavefront measurement accuracy surpassed 0.1 wavelengths (1 wavelength = 633 nm). This study effectively enhanced the detection and in situ calibration capabilities of large telescope systems, ensuring that the performance requirements can be met in the design of future telescopes.

Investigation into the Co-Phase Detection Methodology for Segmented Plane Mirrors Utilizing Grazing Incidence Interferometry

“…While the tilt error detection technique has achieved a certain degree of maturity, the predicament surrounding piston error detection remains unresolved, primarily attributable to issues such as 2π blurring and related challenges [5]. Various methodologies are available for the detection of segmented plane mirrors, including broad-and narrow-band Shack-Hartmann detection [6], dispersion fringe method [7], pentaprism scanning detection [8], dual-wavelength co-phase detection [9], and interference detection method [10]. Refer to Table 1 for an elucidation of their respective merits and demerits.…”