Optical device

An optical device (100) is provided with: a display (110) that outputs image light (50) that forms an image; and an optical system (300) that enlarges an image and has a filter (320) (reflective polarizing plate (321)) and a lens (310) (semi-reflective mirror surface (311)) that are arranged on the eye point side and the display side, respectively, on the optical axis (L) of the display (110), the reflective polarizing plate (321) transmitting or reflecting at least a portion of the image light and the lens (310) transmitting or reflecting at least a portion of the image light. A semi-reflective mirror surface (311) that is an aspheric curved surface in which the amount of change in the curved surface angle continuously increases or decreases in accordance with the distance from the center, and that transmits or reflects at least a portion of the image light; and a movement device (410) that moves the filter (320) (reflective polarizing plate (321)) along the optical axis (L) with respect to the lens (310) (h