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Tilt-Angle Detection of Rotating Objects Using Elliptical Optical Vortices
An elliptical optical vortex, whose orbital-angular-momentum spectrum broadens under oblique illumination, encodes the tilt angle of a rotation axis: the rotational Doppler beat frequencies scale jointly with the vortex ellipticity and the tilt angle, so a beam with periodically varying ellipticity measures the oblique-axis orientation while compensating the Doppler broadening caused by oblique incidence.