Projection lens system having variable magnification
A projection lens system is constructed as a zoom lens system which is for use with a laser light source and performs magnification variation by moving at least a lens group along the optical axis, and the projection lens system fulfills the following conditional formula: (|AC(B 2 −G)|+|AC(R 2 −G)|)/(|AC(B 1 −G)|+|AC(R 1 −G)|)<0.8, where AC(B 2 −G) represents longitudinal chromatic aberration between the wavelengths λB 2 and λG; AC(R 2 −G) represents longitudinal chromatic aberration between the wavelengths λR 2 and λG; AC(B 1 −G) represents longitudinal chromatic aberration between the wavelengths λB 1 and λG; and AC(R 1 −G) represents longitudinal chromatic aberration between the wavelengths λR 1 and λG.
1. A projection lens system constructed as a zoom lens system which is for use with a laser light source and performs magnification variation by moving at least a lens group along an optical axis, the projection lens system fulfilling conditional formula (1) below:
(| AC ( B 2 −G )|+| AC ( R 2 −G )|)/(| AC ( B 1 −G )|+| AC ( R 1 −G )|)<0.8 (1)
where
AC(B 2 −G) represents longitudinal chromatic aberration between blue and green laser wavelengths;
AC(R 2 −G) represents longitudinal chromatic aberration between red and green laser wavelengths;
AC(B 1 −G) represents longitudinal chromatic aberration between (i) a middle value of a green laser wavelength and a blue laser wavelength, and (ii) the green laser wavelength; and
AC(R 1 −G) represents longitudinal chromatic aberration between (i) a middle value of a green laser wavelength and a red laser wavelength, and (ii) the green laser wavelength.
2. The projection lens system according to claim 1 , comprising, in the following order from an enlargement side:
a first lens group;
a second lens group which is movable; and
at least two movable lens groups disposed closer to a reduction side than the second lens group,
wherein,
let a lens group located next to the second lens group on a reduction side of the second lens group be a third lens group,
lens elements in the movable lens groups from the third lens group onward all fulfill conditional formula (2) below:
0.4 <{fw 2 ×Σ( hw×hw×Δθg,F×pi/Vd )}/{ ft 2 ×Σ( ht×ht×Δθg,F×pi/Vd )}<2.5 (2)
where
Δθg,F represents an anomalous dispersion characteristic of each lens glass material;
pi represents a refractive power of each lens element;
fw represents a focal length at a wide-angle end;
ft represents a focal length at a telephoto end;
hw represents a light ray passing height of on-axis marginal light at the wide-angle end;
ht represents a light ray passing height of on-axis marginal light at the telephoto end; and
Vd represents dispersion (an Abbe number) of each lens glass material.
3. The projection lens system according to claim 2 ,
wherein
the at least two movable lens groups are each composed of two or less lens elements.
4. The projection lens system according to claim 2 ,
wherein
the projection lens system fulfills conditional formula (3) below:
T 3 s/TLw< 0.3 (3)
where
T 3 s represents a maximum distance, along the optical axis, from a lens surface in the movable lens groups from the third lens group onward to an aperture stop; and
TLw represents a total lens length at the wide-angle end.
5. The projection lens system according to claim 2 ,
wherein
the projection lens system fulfills conditional formula (4) below:
0.2 <|T max/ T 2|<0.8 (4)
where
Tmax represents a maximum moving amount of the movable lens groups from the third lens group onward in magnification variation; and
T 2 represents a moving amount of the second lens group in magnification variation.
6. The projection lens system according to claim 2 ,
wherein
the movable lens groups from the third lens group onward include at least a lens group having a negative optical power and at least a lens group having a positive optical power.
7. The projection lens system according to claim 2 ,
wherein
the third lens group has a negative optical power.
8. The projection lens system according to claim 2 ,
wherein,
let a lens group located on a reduction side of, next to, the third lens group be a fourth lens group,
the fourth lens group has a positive optical power.
9. The projection lens system according to claim 2 ,
wherein
each lens element having a negative optical power and included in the movable lens groups from the third lens group onward fulfills conditional formula (5) below:
Δθg,F>0 (5)
where
Δθg,F represents the anomalous dispersion characteristic of each lens glass material.
10. The projection lens system according to claim 2 ,
wherein
the first lens group is stationary in magnification variation.
11. The projection lens system according to claim 2 ,
wherein
a lens group located closest to the reduction side is stationary in magnification variation.
12. The projection lens system according to claim 2 ,
wherein
a lens group located closest to the reduction side has a positive optical power.
13. The projection lens system according to claim 2 ,
wherein
movable lens groups located closer to the reduction side than the third lens group are each composed of a single lens.
14. The projection lens system according to claim 2 ,
wherein
movable lens groups located closer to the reduction side than the third lens group are all located closer to the enlargement side than an aperture stop.
15. A projector, comprising:
an image display device that displays an image;
a laser light source;
an illumination optical system that directs light from the laser light source to the image display device; and
a projection lens system that projects, while enlarging, the image displayed on the image display device onto a screen surface,
wherein
the projection lens system is constructed as a zoom lens system which is for use with a laser light source and performs magnification variation by moving at least a lens group along an optical axis, and the projection lens system fulfills conditional formula (1) below:
(| AC ( B 2 −G )|+| AC ( R 2 −G )|)/(| AC ( B 1 −G )|+| AC ( R 1 −G )|)<0.8 (1)
where
AC(B 2 −G) represents longitudinal chromatic aberration between blue and green laser wavelengths;
AC(R 2 −G) represents longitudinal chromatic aberration between red and green laser wavelengths;
AC(B 1 −G) represents longitudinal chromatic aberration between (i) a middle value of a green laser wavelength and a blue laser wavelength, and (ii) the green lasert wavelength; and
AC(R 1 −G) represents longitudinal chromatic aberration between (i) a middle value of a green laser wavelength and a red laser wavelength, and (ii) the green laser wavelength.
16. The projector according to claim 15 ,
wherein
the projection lens system includes, in the following order from an enlargement side:
a first lens group;
a second lens group which is movable; and
at least two movable lens groups disposed closer to a reduction side than the second lens group; and
let a lens group located next to the second lens group on a reduction side of the second lens group be a third lens group,
lens elements in the movable lens groups from the third lens group onward all fulfill conditional formula (2) below:
0.4 <{fw 2 ×Σ( hw×hw×Δθg,F×pi/Vd )}/{ ft 2 ×Σ( ht×ht×Δθg,F×pi/Vd )}<2.5 (2)
where
Δθg,F represents an anomalous dispersion characteristic of each lens glass material;
pi represents a refractive power of each lens element;
fw represents a focal length at a wide-angle end;
ft represents a focal length at a telephoto end;
hw represents a light ray passing height of on-axis marginal light at the wide-angle end;
ht represents a light ray passing height of on-axis marginal light at the telephoto end; and
Vd represents dispersion (an Abbe number) of each lens glass material.
17. The projector according to claim 16 ,
wherein
the at least two movable lens groups of the projection lens system are each composed of two or less lens elements.
18. The projector according to claim 16 ,
wherein
the projection lens system fulfills conditional formula (3) below:
T 3 s/TLw< 0.3 (3)
where
T 3 s represents a maximum distance, along the optical axis, from a lens surface in the movable lens groups from the third lens group onward to an aperture stop; and
TLw represents a total lens length at the wide-angle end.
19. The projector according to claim 16 ,
wherein
the projection lens system fulfills conditional formula (4) below:
0.2 <|T max/ T 2|<0.8 (4)
where
Tmax represents a maximum moving amount of the movable lens groups from the third lens group onward in magnification variation; and
T 2 represents a moving amount of the second lens group in magnification variation.
20. The projector according to claim 16 ,
wherein,
the movable lens groups from the third lens group onward of the projection lens system include at least a lens group having a negative optical power and at least a lens group having a positive optical power.