An optical system includes: a reflective imaging element; and a liquid crystal display panel disposed on a light-incident side of the reflective imaging element, the liquid crystal display panel having a display surface which is inclined with an angle of no less than 45° and no more than 75° relative to a plane defined by the reflective imaging element, a viewing angle dependence of a contrast ratio of the liquid crystal display panel taking a central value in a direction inclined by 10° or more in a direction of tilt of the display surface from a normal of the display surface, and causes an image displayed on the display surface of the liquid crystal display panel to form an image at a position of planar symmetry with respect to the reflective imaging element as a plane of symmetry.