Optical system, stereo optical system, stereo imaging apparatus, imaging apparatus, and image projection apparatus

An optical system having a reduction conjugate point on a reduction side and a magnification conjugate point on a magnification side that are optically conjugate with each other, the optical system comprising:

• a prism including a first transmission surface located on the magnification side, a second transmission surface located on the reduction side, and at least three reflection surfaces located on an optical path between the first transmission surface and the second transmission surface;
• wherein the prism has a meridional plane through which light rays reflected by the at least three reflection surfaces pass,
• wherein the at least three reflection surfaces include a first reflection surface and a second reflection surface in order from the magnification side to the reduction side, and a most reduction-side reflection surface located closest to the reduction side,
• wherein an intermediate imaging position having a conjugate relationship with both of the reduction conjugate point and the magnification conjugate point is positioned between the second reflection surface and the most reduction-side reflection surface inside the prism,
• wherein the second reflection surface is positioned between the intermediate imaging position and the first reflection surface, and
• wherein the first reflection surface is positioned in a region where a plurality of principal rays traveling inside the prism are converged on.