Calibration of a Multiwavelength Co-Phase Measurement System for a Segmented Solar Telescope

The segmented solar telescope described in this study employs a simultaneous dual-wavelength measurement technique to achieve co-phase alignment. To meet the measurement requirements of 20 μm range, 5 nm root mean square precision, and edge jump rates of <10⁻⁶, this study focused on calibrating the dual-wavelength measurement system for the segmented-mirror solar telescope. Analysis of the relative error in the measurement system revealed that assembly-induced errors such as defocus, translation, scaling, and rotation markedly degrade measurement accuracy. To address these issues, we propose a defocus error compensation algorithm, based on the light intensity distribution of the point spread function and an affine transformation model, to calibrate spatial pose deviations across the two measurement channels. A dual-wavelength measurement system was implemented on a segmented-mirror experimental platform for calibration. Experimental results demonstrated that the mean relative error decreased from −0.6423 to −0.0345 nm after calibration, reflecting improved reliability and stability of the co-phase measurements.