Ultra-sensitive displacement measurement method based on polarization grating

The invention relates to an ultra-sensitive displacement measurement method based on polarization gratings. The birefringence fast axes on the surfaces of the polarization gratings are periodically distributed in the single direction, after the two polarization gratings are placed face to face, after one polarization grating is slightly moved, the polarization direction of emergent light can greatly deflect, petal-shaped light spots are generated after the emergent light passes through the vortex half-wave plate and the polaroid, and the light spots can obviously rotate along with the polarization direction. And the micro transverse displacement of the polarization grating can be calculated according to the rotation angle. Different from a conventional displacement measurement method based on an interferometer, the method provided by the invention utilizes novel optical elements, namely a polarization grating and a vortex half-wave plate, to directly detect transverse infinitesimal displacement, and can theor