Title:
【発明の名称】ズームレンズ
Document Type and Number:
Japanese Patent JP3066925
Kind Code:
B2
Abstract:
PURPOSE:To excellently compensate the power chromatic aberration of the zoom lens for projection by including at least one positive lens which satisfies a specific expression in a 2nd lens rear group. CONSTITUTION:In the zoom lens which consists of a 1st lens group with negative refracting power and a 2nd lens group with positive refracting power in order from the screen side and varies in focal length by varying the interval between the 1st and 2nd lens groups, the 2nd lens group is composed of a screen side 2nd lens front group and an original-image side 2nd lens rear group. Then the 2nd lens rear group includes a positive lens which satisfies the condition shown by an inequality I. Namely, glass which has extraordinary variance is used for the positive lens in the 2nd lens group where a main light beam passes at a high position. In the inequality, thetag.F2rP is the extraordinary variance value of the positive lens in the 2nd lens rear group and Vd2rP is the Abbe number of the positive lens in the 2nd lens rear group; and thetag.F is expressed by an equation II, where ng is the refractive index of a g-line, nFF is the refractive index of an F line, and nc is the refractive index of a C-line.
Inventors:
Saburo Sugawara
Application Number:
JP27985091A
Publication Date:
July 17, 2000
Filing Date:
October 25, 1991
Export Citation:
Assignee:
Canon Inc
International Classes:
G02B15/16; (IPC1-7): G02B15/16
Domestic Patent References:
| JP3120507A | ||||
| JP60129720A | ||||
| JP6057813A | ||||
| JP5536886A |
Attorney, Agent or Firm:
Keizo Nishiyama (2 outside)