CIRCULARL POLARIZATION-TYPE POLARIZATION DIVERSITY ELEMENT, SCANNING ELEMENT USING SAME, AND LIDAR

摘要

In the prior art, a scanning element used in the autonomous driving car technology of Lidar has inertia due to continuously rotating a mirror or the like by MEMS, and thus is for a raster scan that scans a scene all at once. Such a scanning element was not capable of moving discontinuously from an arbitrary point to another arbitrary point, and performing a high-speed scan that is programmable to an arbitrary frequency and an arbitrary pattern and equivalent to the raster scan. According to the present invention, a Lidar is manufactured comprising a scanning element in which: two polarization gratings, which have a double refraction director with a thickness corresponding to a half-wavelength plate and rotate with a period Λ, are used spaced apart at a desired interval; and a polarization diversity method, in which the half-wavelength plate is inserted in the path of one among two light beams, that is, a clockwise-circularly polarized light beam and a counterclockwise-circularly polarized light beam, separately emitted according to the rotation direction of the circularly polarized light, is adopted to achieve a conversion into parallel and proximate circularly polarized light beams having the same rotation direction, wherein the scanning element combines structures in which pairs of a polarization switch and the polarization grating are connected in multiple stages.