| US 7,511,892 B2 | ||
| Image-acquisition optical system | ||
| Hideyasu Takato, Hino (Japan) | ||
| Assigned to Olympus Medical Systems Corp., Tokyo (Japan) | ||
| Filed on Mar. 26, 2007, as Appl. No. 11/728,877. | ||
| Claims priority of application No. 2006-092465 (JP), filed on Mar. 29, 2006. | ||
| Prior Publication US 2007/0258150 A1, Nov. 08, 2007 | ||
| Int. Cl. G02B 15/14 (2006.01); G02B 21/00 (2006.01) | ||
| U.S. Cl. 359—676 [359/368; 359/686] | 7 Claims |
| 1. An image-acquisition optical system formed of a plurality of lens groups, wherein by moving at least one of the plurality
of lens groups on the optical axis, it is possible to change a state from a normal observation state (wide-angle end) to a
close-up magnified-observation state (telephoto end),
wherein a distance between an object side surface in the lens at an extreme object side and an observation point of an object
is less than or equal to 0.25 mm in the close-up magnified-observation state, and
wherein the following conditional expression is satisfied:
βTELE<−2.0
where βTELE is the magnification of the image-acquisition optical system at the telephoto end.
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