JP2008158159A5

JP2008158159A5 -

Info

Publication number: JP2008158159A5
Application number: JP2006345587A
Authority: JP
Filing date: 2006-12-22
Publication date: 2010-02-12
Anticipated expiration: 2026-12-22

Claims

In order from the enlargement side to the reduction side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens having a negative refractive power group, the fifth lens group having a positive refractive power, is composed of a sixth lens group having a positive refractive power, for zooming, said first, sixth lens group is immovable, during zooming A zoom lens in which the fifth lens group moves from the second lens group and the first lens group moves upon focusing. The first lens group has a positive lens on the most magnifying side and has at least one positive lens. Having a negative lens, and when the Abbe number and partial dispersion ratio of one negative lens material are νdn and θgFn, respectively,
νdn <35
0.008 <θgFn− (0.644−0.00168 · νdn) <0.040
A zoom lens characterized by satisfying the following conditions:

When the focal length of the entire system at the wide-angle end is fw and the focal length of the negative lens having the smallest Abbe number among the negative lenses in the first lens group is f1n, −4.3 <f1n / fw <−1. .4
The zoom lens according to claim 1, wherein the following condition is satisfied.

When the focal length of the entire system at the wide-angle end is fw, and the back focus in terms of air when focusing on an object at infinity is bf,
0.35 <fw / bf <0.65
The zoom lens according to claim 1, wherein the following condition is satisfied.

The first lens group has a meniscus-shaped positive lens having a convex surface on the reduction side and a convex side on the most reduction side, and the curvature radii of the enlargement side and the reduction side surface of the positive lens are r1a and r2a, respectively. When
0.08 <(r1a-r2a) / (r1a + r2a) <0.70
The zoom lens according to claim 1, 2 or 3, wherein the following condition is satisfied.

When the focal length of the first lens group is f1, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fw and ft, respectively.
^{^{^{-1.0 <f1 / (fw 2 +}}} ft 2) 1/2 <-0.65
The zoom lens according to claim 1, wherein the following condition is satisfied.

6. The zoom lens according to claim 1, wherein the first lens group includes six or more lenses having both lens surfaces having a spherical shape.

The fourth lens group has one or more negative lenses having an aspherical surface, and when the refractive index of one negative lens material is Nd4n,
1.60 <Nd4n
The zoom lens according to claim 1, wherein the following condition is satisfied.

A zoom lens according to claim 1, and a display unit that forms an original image, wherein the original image formed by the display unit is projected onto a projection surface by the zoom lens. Image projection device.

When a prism is provided between the zoom lens and the projection image, and the Abbe number of the material of the prism is νdpr and the partial dispersion ratio is θgFpr, νdpr <40
0.002 <θgFpr− (0.644−0.00168 · νdpr) <0.040
The image projection apparatus according to claim 8, wherein the following condition is satisfied.