| US 7,468,847 B2 | ||
| Optical lens system for taking image | ||
| Hsiang Chi Tang, Taichung (Taiwan) | ||
| Assigned to Largan Precision Co., Ltd., Taichung (Taiwan) | ||
| Filed on May 31, 2007, as Appl. No. 11/755,738. | ||
| Claims priority of application No. 95148721 A (TW), filed on Dec. 25, 2006. | ||
| Prior Publication US 2008/0151389 A1, Jun. 26, 2008 | ||
| Int. Cl. G02B 9/14 (2006.01) | ||
| U.S. Cl. 359—785 [359/784] | 21 Claims |
| 1. An optical lens system for taking image comprising three lens elements with refractive power, from the object side to the
image side:
a first lens element with positive refractive power having a convex surface on the object side and a concave surface on the
image side, at least one of the object-side surface and the image-side surface of the first lens element being aspheric;
a plastic second lens element with negative refractive power having a concave surface on the object side and a convex surface
on the image side, the object-side surface and the image-side surface of the second lens element being aspheric;
a plastic third lens element with positive refractive power having a convex surface on the object side and a concave surface
on the image side, the object-side surface and the image-side surface of the third lens element being aspheric; and
an aperture stop located in front of the first lens element for controlling brightness of the optical lens system;
wherein a focal length of the second lens element is f2, a focal length of the optical lens system is f, and they satisfy the relation:
0.3<|f/f2|<0.74.
|