Stereographic projection device with low throw ratio and high light effect and stereographic projection system

A stereographic projection device with a low throw ratio and a high light effect, comprising: a polarization and light-splitting assembly (302) which splits projected light beams into a transmitted light beam (201), a first reflected light beam (202) and a second reflected light beam (203); a polarization state conversion assembly (303, 304) which adjusts the polarization state of the transmitted light beam or the polarization states of the first reflected light beam and the second reflected light beam; a light path direction adjustment assembly (305, 306) which adjusts the propagation direction of the transmitted light beam or the propagation directions of the first reflected light beam and the second reflected light beam; a light beam size adjustment assembly (307) which adjusts the ranges of the sizes of the transmitted light beam, the first reflected light beam and the second reflected light beam; and a light modulator (309) which modulates the transmitted light beam, the first reflected light beam and the second reflected light beam which have been adjusted into left-hand circularly polarized light and right-hand circularly polarized light in accordance with a frame sequence. A stereographic projection device with a low throw ratio and a high light effect can effectively reduce an optical path difference between a reflected light beam and a transmitted light beam, so that the volume of the whole device is greatly reduced, and the superposition of various light beams becomes simpler.