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Patent Searching and Data


Title:
ZOOM LENS, LENS UNIT, CAMERA, AND PERSONAL DIGITAL ASSISTANT
Document Type and Number:
Japanese Patent JP2005266181
Kind Code:
A
Abstract:

To obtain a high variable magnification ratio and a high performance over the whole variable magnification range with a zoom lens in which each optical system of a negative 1st group G1, a positive 2nd group G2, a negative 3rd group G3, and a positive 4th group G4 is sequentially located from an object side, and thereby reducing a full length and a front lens diameter of the optical system.

The zoom lens is constituted of the 1st group G1 arranged sequentially from an object side, a negative meniscus lens E1, an negative lens E2, and positive lens E3 with their convexes faced to the object side, and an aspherical surface is formed on the image plane side of either of the negative lenses in the 1st group G1, and the magnification is made variable from a short focus end to a long focus end by gradually changing the spaces between each group optical system to narrow the space between the 1st group G1 and the 2nd group G2, to widen the space between the 2nd group G2 and the 3rd group G3, and also to widen the space between the 3rd group G3 and the 4th group G4. Expressing the focal length of the 1st group G1 as F1, the focal length of the whole system at the short focus end as FW, the space between the 3rd group G3 and the 4th group G4 at the long focus end as D3T, and the space between the 3rd group G3 and the 4th group G4 at the short focus end as D3W, a specified conditional fomula is satisfied.


Inventors:
HIRAKAWA MAKOTO
Application Number:
JP2004000077306
Publication Date:
September 29, 2005
Filing Date:
March 17, 2004
Export Citation:
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Assignee:
RICOH KK
International Classes:
G02B15/20; G02B13/18; H04N5/225; H04N101/00; (IPC1-7): G02B15/20; G02B13/18; H04N5/225
Attorney, Agent or Firm:
真田 修治