| 摘要 |
PURPOSE:To obtain a compact zoom lens with an image plane covering range by allowing an optical system consisting of four lens groups which have a focusing function with positive refracting power, power varying function with negative refracting power, image plane compensating function, and image forming function with positive refracting power successively from the object side to meet specific requirements. CONSTITUTION:The 1st lens group 1 consists of a negative meniscus aspherical lens 1a made of plastic having the convex surface on the object side, a positive aspherical biconvex lens 1b made of plastic, and a positive lens 1c made of glass successively from the object side. Then, this zoom lens using plastic lenses meets various requirements showsn by inequalities I -V. In the inequalities, fw is the shortest focal length of the whole system, f1 the focal length of the 1st lens group 1, fa, fb, and fc the focal lengths of the lenses 1a, 1b, and 1c, R3 the radius of curvature of the object-side surface of the lens 1b, and nu3 the Abbe number of the lens 1c. |
