Research on symmetry measurement of targets and impact of blade opening angle based on OAM spectrum

Abstract This paper presents a method for jointly measuring the number of blades and the opening angle of rotationally symmetric targets based on the orbital angular momentum (OAM) spectral missing effect. We use single-mode vortex beam to illuminate the fan-shaped target. The number of blades is determined by analyzing the intervals of dispersion peaks in the echo OAM spectrum. The single blade’s opening angle is determined by the suppression characteristic of specific OAM modes, enabling simultaneous estimation identification of geometric parameters. We also verified that this method combines rotational invariance and beam parameter robustness, providing a new idea for non-contact detection of structures such as aircraft blades and unmanned aerial vehicle rotors.