| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a lens system with a long focal length in which a focusing group has a small size and is lightweight and the size of the lens including its driving mechanism is also small and which is easily manufactured such that the sensitivity in eccentricity of the focusing group is small. <P>SOLUTION: A catadioptric lens system includes, in order of light travel: a first lens group that includes a concave mirror and a convex mirror and has a positive refractive power; a second lens group that is more closely positioned to an image side than the concave mirror and has a negative refractive power; and a third lens group that has a positive refractive power. A close-range object is brought into focus by moving the second lens group in a direction parallel with the optical axis. A conditional expression (0), namely, 0<f/f12, is satisfied, where f is a focal length of the whole system in a state where the focus is at infinity, and f12 is a composite focal length of the first lens group and the second lens group in a state where the focus is at infinity. <P>COPYRIGHT: (C)2013,JPO&INPIT |
