| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming optical system concurrently satisfying the reduction of cost, high performance and miniaturization. SOLUTION: As for the image forming optical system, a 1st lens L11 having positive refractive power, a 2nd lens L12 turning its concave surface to an object side and having negative refractive power, a 3rd lens L13 turning its convex surface to an image side and having positive refractive power, and a 4th lens L14 having negative refractive power are arranged in such order from the object side in an optical system having a brightness diaphragm S, and the 2nd and the 3rd lenses L12 and L13 are bonded. By such constitution, an angle formed by an incident light beam on a doublet with an emitted light beam therefrom is kept small, and the occurrence of aberration on a refractive surface and performance variation at the relative eccentric time of the lens are made as small as possible. COPYRIGHT: (C)2005,JPO&NCIPI
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