| 摘要 |
PROBLEM TO BE SOLVED: To provide a transmission optical system guiding light emitted from a light source in a state of an approximately parallel luminous flux to an exposure device body and allowing the light to enter in the state of an approximately parallel luminous flux while reducing the number of optical components.SOLUTION: In a transmission optical system, light emitted from a light output port (1a) of a light source in a state of an approximately parallel luminous flux is guided to a light intake (3) of an exposure device body, and is allowed to enter the light intake in the state of an approximately parallel luminous flux. The transmission optical system includes, in order from an incidence side of light: a first mirror (21) having a first reflecting surface (21a) comprising a portion of a curved surface with rotational symmetry about a first axis (21b); and a second mirror (22) having a second reflecting surface (22a) comprising a portion of a curved surface with rotational symmetry about a second axis (22b). A line of intersection of a plane containing the first axis and the first reflecting surface is a conic curve, and a line of intersection of a plane containing the second axis and the second reflecting surface is a conic curve. |
