| 摘要 |
To achieve a projection lens which has a wide angle view, a short projection distance and telecentricity and in which the projection can be performed with high contrast, various aberrations such as distortion aberration, etc. are reduced and the optical path is converted. A first lens group having negative refractive power and second and third lens groups having positive refractive power are arranged from a longer conjugate side. Representing a back focus at a projection distance of infinite point by BF; the composite focus distance of the entire system by F; the central air spacing between said first lens group and said second lens group by GD1; the composite focus distance of said first lens group by F1; the composite focus distance of said second lens group and said third lens group by F23; and the central air spacing between said second lens group and said third lens group by GD2, the following equation is satisfied: Ä2.8 <BF/FÜÄ3.0 <GD1/F <4.50ÜÄ0.40 <-F1/F23 <0.48ÜÄ0.40 <GD2/F23 <0.8Ü. At this time, the focus adjustment is carried out by moving the first lens group along the optical axis OA. <IMAGE> |
