An optical system is provided. The optical system includes a luminous system which comprises a plurality of light source devices and an image unit; and a projection system which receives light having an image through the luminous system, and enlarges and projects the light, wherein the plurality of light source devices comprise a reflection member which reflects light beam emitted from the light source devices, and are disposed so that the light beam emitted from the light source devices is reflected by the reflection member one time and enters to the image unit.