| 摘要 |
PROBLEM TO BE SOLVED: To provide a wide angle lens, which shortens back focus and includes a wide angle area, suitable for a miniaturized high-performance camera by making the various parameters of a lens system satisfy a specified conditional expression. SOLUTION: A first lens group G1 is provided with a positive lens L11 turning a sharp convex face toward the side of an object and a negative meniscus lens L12 (L13) arranged on the image side of that lens while turning a sharp convex face toward the side of the object. A second lens group G2 is provided with paired achromatic lenses L22 and L33 having a positive focal distance, and that pair is composed of joint or separate lenses composed of negative lens L22 and positive lens L23 successively from the side of the object. A third lens group G3 is provided with a negative lens L31 turning a concave face toward the object side and a positive lens L32 (L33) arranged on the image side of that lens. Such a lens system satisfies the conditions of Bf/f<1.45, Bf/y<2.5 and 9.5>TL/f>5. In the expressions, Bf is the back focus of the entire system, (f) is the focal distance of the entire system, TL is a distance from the most object side face of the wide angle lens to the image surface and (y) is a peak image height.
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