In the prior art, a scanning element used for
Lidar in the self-driving car technology employed a mirror or the like continuously rotated by MEMS, and due to the
inertia of the mirror or the like, the scanning element was suited for a
raster scan that scans a scene in one
stroke, but was incapable of discontinuous movement from one arbitrary point to another, and programmable scanning with an arbitrary frequency in an arbitrary pattern, as fast as the
raster scan. In the present invention, there was fabricated
Lidar, which is composed of a
polarization diversity scheme and a scanning element, wherein the
polarization diversity scheme uses two polarization gratings, each polarization
grating having a thickness such that it becomes a half-wave plate, wherein birefringent directors of each polarization
grating rotate with a period Λ, wherein these polarization gratings are disposed with a desired interval from each other, wherein a half-wave plate is inserted in either one of two paths of separated, exiting right-handed or left-handed circularly polarized
light beam, depending on a rotation direction of the circularly polarized light, to thereby enable conversion of light beams into parallel
proximate circularly polarized light beams with the same rotational direction, and wherein the scanning element has a multistage structure of polarization switch-polarization
grating sets connected in combination, with a polarization switch and a polarization grating being defined as one set.