Olympus Imaging Corporation

Atsujiro Ishii

Hirohiko Kimata

Takeshi Hosoya

Yoshiaki Shimizu

The invention relates to a new mechanism for permitting a zoom lens to focus on a short distance subject by moving a focusing lens group in an amount that varies in an optical axis direction depending on a zooming position. The zoom lens comprises, in order from its object side, a positive first lens group, a negative second lens group and a positive third lens group. Zooming is implemented while the space between adjoining lens groups is varied, and focusing on a short distance subject is implemented by moving the negative second lens group in an amount that varies in the optical axis direction depending on a zooming position. The negative second lens group comprises a negative front unit GF and a negative rear unit GR. The space between the negative front unit GF and the negative rear unit GR is varied depending on a subject distance but that space remains constant wherever the zooming position lies.

Zoom lens

The invention relates to a zoom lens which, albeit being of simplified construction, makes sure brightness and holds back fluctuations of astigmatism, and facilitates making sure being fast and the angle of view and the zoom ratio at the wide-angle end. The zoom lens comprises a first group Gof positive power, a second group Gof negative power and a third group Gof positive power, with a stop S between the second group Gand the third group G. Upon zooming from the wide-angle end to the telephoto end, the first group G, the second group G, and the third group Gmoves; the second group Gmoves toward the object side after moving toward the image side; the first group Gand the third group Gare positioned on the object side at the telephoto end with respect to the wide-angle end. The first group Gcomprises one negative lens and one or two positive lenses, and the second group Gcomprises a first negative meniscus lens convex on its object side, a second negative lens wherein the image side surface is larger in the absolute value of a curvature than the object side surface, and a third positive lens wherein the object side surface is larger in the absolute value of a curvature than the image side surface. Upon focusing from a far distance to a near distance, the second group Gmoves.

The invention relates to a zoom lens that can achieve higher performance easily. In order from the object side of the zoom lens, it comprises a positive first lens group G, a negative second lens group G, a positive third lens group Gand a positive fourth lens group G, wherein zooming is implemented by a change in the space between the respective lens groups. Upon zooming from the wide-angle end to the telephoto end, while the space between the first lens group Gand the second lens group Ggrows wide, the space between the second lens group Gand the third lens group Gbecomes narrow and the space between the third lens group Gand the fourth lens group Gbecomes narrow, the first, the third, and the fourth lens group moves toward the object side only, and the second lens group Gmoves in a convex orbit toward the image plane side. The second lens group G, and the fourth lens group Ghas at least one aspheric surface, and the zoom lens satisfies the following conditions: 0.1&#x3c;|f/f|&#x3c;0.14 and 0.1&#x3c;|f/f|&#x3c;0.6 where fi is the focal length of an i-th lens group.

The invention relates to a zoom lens in which tweaks to the mode of movement of lens groups and the first lens group contribute more to making sure the desired zoom ratio and optical performances and ensuring that the whole length of the zoom lens is kept short while carrying it around. The zoom lens comprises a positive first lens group G, a negative second lens group Gand a positive third lens group G, and includes an aperture stop S located between the second Gand the third lens group G. Upon zooming from the wide-angle end to the telephoto end, the first lens group Gmoves in unison, and the second lens group Gmoves in unison. The first Gand the second lens group Gare positioned nearer to the object side at the telephoto end than at the wide-angle end, with an increasing spacing between the first Gand the second lens group Gand a decreasing spacing between the second Gand the third lens group G. The zoom lens satisfies conditions (1) and (2) about the power and the amount of movement of the first lens group G

Growing community of inventors

Shibuya-ku, Japan

Atsujiro Ishii