| 摘要 |
PROBLEM TO BE SOLVED: To provide a retro-focus lens that has a simple constitution, is bright, has a good balance between spherical aberration and image plane, corresponds to a digital imaging device, and is suitably usable for a wide-angle lens for image acquisition where the movement of the focal position is small with respect to temperature change. SOLUTION: The lens for image acquisition is a lens of three-group constitution as a whole where a group (front group) in front of a diaphragm includes, in order from the object side, a negative first group (G1 and G11) and a positive second group (G2 and G12), and a group (rear group) at the back of the diaphragm includes a positive third group (G3 and G13). The positive third group (G3 and G13) of the rear group includes a cemented lens where three positive, negative, and positive single lenses are joined and that has a negative focal length as a whole. COPYRIGHT: (C)2011,JPO&INPIT |
