OPTICAL DEVICE

An optical device includes a light receiving unit that receives reflected light reflected from an object by emitted light emitted from a light emitting unit, an optical element that guides incident light including the reflected light and ambient light from a region including the object to a position on the light receiving unit according to a component included in the incident light, and a detection device that detects the reflected light based on a distribution of received light intensity on the light receiving unit. A light receiving element of the light receiving unit is arranged in a second direction intersecting a first direction in which the incident light is dispersed by the optical element.