| 摘要 |
PROBLEM TO BE SOLVED: To provide a reflective type super-wide angle lens that can be composed at a low cost even in the case where a horizontal view angle is 180°or more. SOLUTION: The mirror A of the front group that has an infinity focal distance includes: a rotation-symmetrical aspheric convex mirror 1 and a rotation-symmetrical spheric or aspheric concave mirror 2. The lens B of the rear group that has a positive focal distance is composed of four lenses, which are a meniscus convex spherical lens 3, a both-sided spherical lens 4, a meniscus convex spherical lens 5, and a meniscus convex spherical lens 6. In each of the spherical lenses 3 to 6, the ratio (r/R) of a lens effective radium (r) to a lens spheric radius (R) is 0.55 or less. In the meniscus convex spherical lens 3 and both-sided concave spherical lens 4, a refractive index (nd) on a line d is of 1.70 or higher, and one has an Abbe's number (υd) of 24 or less while the other has an Abbe's number (υd) of 54 or more. COPYRIGHT: (C)2007,JPO&INPIT
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