Projection zoom lens and projection-type display apparatus

1. A projection zoom lens for projecting an optical image of rays, which are irradiated from a light source onto a light valve and are modulated by a predetermined image displayed on the light valve, onto a screen, the projection zoom lens comprising:

a plurality of lens groups that is formed as a telecentric system on a reduction side thereof and includes at least two movable lens groups which are movable during zooming,

wherein the plurality of lens groups is arranged to include, in order from a magnification side, at least a first lens group that has a negative refractive power, remains stationary during zooming, and performs focusing, and a second lens group that has a negative refractive power and remains stationary during zooming and focusing.

2. The projection zoom lens according to claim 1 , wherein the plurality of lens groups includes, in order from the second lens group toward the reduction side, a third lens group that has a positive refractive power and is movable along an optical axis during zooming, a fourth lens group that has a positive refractive power and is movable along the optical axis during zooming, a fifth lens group that has a positive or negative refractive power and is movable along the optical axis during zooming, and a sixth lens group that has a positive refractive power and remains stationary during zooming.

3. The projection zoom lens according to claim 2 , wherein the third lens group, the fourth lens group, and the fifth lens group are movable from the reduction side to the magnification side during zooming from a wide-angle end to a telephoto end.

4. The projection zoom lens according to claim 1 , wherein the following Conditional Expression (1) is satisfied:

−7.0 <f 2 /fw<− 2.0  (1),

where

fw is a focal length of the whole lens system at the wide-angle end, and

f 2 is a focal length of the second lens group.

5. The projection zoom lens according to claim 1 , wherein the following Conditional Expression (2) is satisfied:

1.5 <Bf/fw< 4.0  (2),

where

fw is a focal length of the whole lens system at the wide-angle end, and

Bf is an air-converted back focal length of the whole lens system.

6. The projection zoom lens according to claim 2 , wherein the fourth lens group is formed of a single biconvex lens, and satisfies the following Conditional Expression (3):

70 <νd 4  (3),

where

νd4 is an Abbe number of the biconvex lens constituting the fourth lens group at the d-line.

7. The projection zoom lens according to claim 1 , wherein the following Conditional Expression (4) is satisfied:

70 <νd 5  (4),

where

νd5 is an Abbe number of a positive lens convex toward the reduction side in the fifth lens group at the d-line.

8. The projection zoom lens according to claim 2 , wherein in the entire zooming range, an aperture, which remains stationary during zooming so as to keep an F number constant, is disposed between the fourth lens group and the fifth lens group.

9. The projection zoom lens according to claim 2 , wherein in the entire zooming range, an aperture, which is independently movable so as to keep an F number constant, is disposed between the fourth lens group and the fifth lens group.

10. A projection-type display apparatus comprising the projection zoom lens according to claim 1 and further comprising:

the projection zoom lens being telecentric on the reduction side thereof;

a light source;

a light valve;

an illumination optical unit that guides rays originated from the light source into the light valve; and

wherein the rays originated from the light source are optically modulated by the light valve, and are projected onto a screen by the projection zoom lens.