| 摘要 |
PROBLEM TO BE SOLVED: To obtain a compact large-aperture wide-angle lens which is compact and has a wide viewing angle, which is bright to such an extent that its F value is about 1.0 to 1.1 while maintaining excellent optical performance and which is suitable for a monitor camera by arraying a 1st negative lens group, a diaphragm and a 2nd positive lens group from an object side and constituting the 1st lens group of six lenses having specified shape. SOLUTION: The 1st lens group G1 having negative refractive power, the diaphragm 2 and the 2nd lens group G2 having positive refractive power are arrayed in order from the object side. A filter part 2 such as an infrared cut filter is arranged on the image side of the 2nd lens group G2, and luminous flux made incident along an optical axis X from the object side is formed into an image at an image-forming position on the image pickup surface of a CCD. Then, this lens satisfies following conditional expressions (1) and (2). (1) 2.0<DS/f<4.0 and (2) 3.3<R2/f<4.5. Provided that (f) means the focal distance of a lens entire system, DS means the thickness of a combined lens in the 1st lens group and R2 means the radius of curvature of the surface on the image side of the lens nearest to the object side in the 1st lens group.
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