| 摘要 |
PROBLEM TO BE SOLVED: To obtain excellent image forming performance with a small f-number by correcting spherical aberration by the action of a 1st lens having positive refractive power, a 2nd lens being a meniscus lens having convex surface facing an object side, and a 3rd lens being the meniscus lens having concave surface facing the object side, and satisfying a specified condition. SOLUTION: The lens is provided with the 1st lens L1 having positive refractive power, the 2nd lens L2 consisting of the meniscus lens whose convex surface faces the object side, the 3rd lens L3 consisting of the meniscus lens whose concave surface faces the object side, and a concave mirror M whose concave surface faces the object side in order from the object side. In an image pick-up state, light from the object forms an object image between the lens L3 and mirror M through the lenses L1, L2 and L3 and the mirror M. Assuming that the synthetic focal distance of the lenses L1, L2 and L3 is f123 and the focal distance is (f), the expression 10<|f123|/f is satisfied.
|
