| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive lens system constituted of a small number of lenses and adopting plastic for all the lenses or adopting a glass spherical lens for one part of the lenses by satisfying specified conditions in a two-group type zoom lens. SOLUTION: A 1st group is composed of a 1st lens L1 having negative power, a 2nd lens L2 being a convex lens bearing all the positive power of the 1st group, and a 3rd lens L3 having negative power in order from an object side. A 2nd group is composed of a 4th lens L4 having positive power, a 5th lens L5 being a concave lens bearing all the negative power of the 2nd group and a 6th lens L6 having positive power. This lens satisfies the conditions d9<0.7×F2, f4<F2/0.3,ν5<40 andν4>40. Then, d9 is space between the lenses L4 and L5. F2 is the focal distance of the 2nd group and f4 is the focal distance of the lens L4. Andν5 is the Abbe number of the lens L5 andν4 is the Abbe number of the lens L4. One surface of the lenses L2, L3, L5 and L6 consists of an aspherical surface.
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