| 摘要 |
<p>[Objective] To obtain a scanning optical system capable of being configured to be compact and of sufficiently decreasing the beam diameter of light on a scanning target surface. [Constitution] A scanning optical system includes: a galvanometer mirror (illustrated as mirror 4a in the drawings) (4) that reflects and deflects a light beam (2) emitted from a light source, and an f¸ lens (5) that focuses the deflected light beam (2) on a scanning target surface. The f¸ lens (5) is constituted by a first lens (L1), which is a spherical lens having a positive refractive power, a second lens (L2), which is a spherical lens having a negative refractive power, a third lens (L3), which is a spherical lens having a negative refractive power, a fourth lens (L4), which is a spherical lens having one of a positive refractive power and a negative refractive power, and a fifth lens (L5), which is a spherical lens having a positive refractive power, provided in this order from the side of the galvanometer mirror (4). The scanning optical system satisfies Conditional Formula (1) below:
wherein f is the focal length of the entire f¸ lens (5), and f4 is the focal length of the fourth lens (L4).</p> |
