| 摘要 |
PROBLEM TO BE SOLVED: To provide a bright projecting wide-angle lens that has brightness the F-number of which is approximately 2.0 and that has a projection angle≥90°. SOLUTION: A first lens group G<SB>1</SB>is composed of three negative lenses and has negative power. The second lens group G<SB>2</SB>is composed of: one negative lens; three positive lenses; two cemented lenses, each of which is composed of one negative lens and one positive lens cemented together; and one cemented lens having positive power and composed of two positive lenses and one negative lens cemented together. The first lens group G<SB>1</SB>includes at least one aspherical lens. Further, this lens satisfies conditional formula (1) given below. 0.2≤¾F<SB>1</SB>/F<SB>2</SB>¾≤0.8, wherein F<SB>1</SB>is the composite focal length of the first lens group, and F<SB>2</SB>is the composite focal distance of the second lens group. COPYRIGHT: (C)2009,JPO&INPIT
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