PROJECTION LENS SYSTEM HAVING MAGNIFICATION CHANGING FUNCTION AND PROJECTOR

• US 20150346464A1
• Filed: 12/25/2013
• Published: 12/03/2015
• Est. Priority Date: 12/27/2012
• Status: Active Grant

• Current Assignee: Konica Minolta Inc.
• Original Assignee: Konica Minolta Inc.
• Inventors: IMAI, YUSUKE, INOUE, KAZUHIKO
• Granted Patent: US 9,678,412 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• CPC Class Codes: G02B 13/22 Telecentric objectives or lens systems
• CPC Class Codes: G02B 15/1465 the first group being negative
• CPC Class Codes: G02B 15/177 having a negative front lens or group of lenses
• CPC Class Codes: G02B 27/0988 Diaphragms, spatial filters, masks for removing or filtering a part of the beam
• CPC Class Codes: G02F 1/133509 Filters, e.g. light shielding masks
• CPC Class Codes: G03B 21/142 Adjusting of projection optics
• CPC Class Codes: G03B 2205/0046 Movement of one or more optical elements for zooming
• CPC Class Codes: G03B 2205/0053 Driving means for the movement of one or more optical element

Abstract

A zoom lens is a projection lens which is composed of a negative first lens group, a negative second lens group, a positive third lens group, a negative fourth lens group, a fifth lens group, and a positive sixth lens group in order from the enlargement conjugate side, and changes magnification by changing the intervals between the lens groups. At least the second, third, and fifth lens groups move when the magnification is changed, and the third lens group moves from the enlargement conjugate side to the reduction conjugate side when the magnification is changed from a telephoto end to a wide angle end. An aperture stop is disposed between the surface closest to the reduction conjugate side of the third lens group and the surface closest to the enlargement conjugate side of the fifth lens group, and is approximately telecentric on the reduction conjugate side.

Claims

1. A projection lens system, comprising, in order from an enlargement conjugate side:

a first lens group having a negative refractive power;

a second lens group having a negative refractive power;

a third lens group having a positive refractive power;

a fourth lens group having a negative refractive power;

a fifth lens group; and

a sixth lens group having a positive refractive power,

the projection lens system achieving zooming by varying a distance between lens groups,

wherein

at least the second lens group, the third lens group, and the fifth lens group each move during zooming;

the third lens group moves from the enlargement conjugate side to a reduction conjugate side during zooming from a telephoto end to a wide-angle end;

an aperture stop is disposed between a most reduction-conjugate-side surface of the third lens group and a most enlargement-conjugate-side surface of the fifth lens group;

the projection lens system is substantially telecentric on the reduction conjugate side; and

the fourth lens group includes, in order from the enlargement conjugate side, two or more negative lens elements and a positive lens element.

2. The projection lens system according to claim 1,

wherein

the fifth lens group has a positive refractive power.

3. The projection lens system according to claim 2,

wherein

the first lens group remains stationary except during focusing.

4. The projection lens system according to claim 2,

wherein

the first lens group remains stationary except during focusing;

and

in addition to the second lens group, the third lens group, and the fifth lens group, the fourth lens group moves during zooming from the telephoto end to the wide-angle end.

6. The projection lens system according to claim 2,

wherein

a most enlargement-conjugate-side lens element in the first lens group has a negative refractive power.

7. The projection lens system according to claim 2,

wherein

conditional formula (1) below is fulfilled:

1.57<

np<

1.65

where

np represents an average value of refractive indices for a d-line of lens elements constituting the first lens group, the second lens group, and the third lens group.

8. The projection lens system according to claim 2,

wherein

conditional formula (2) below is fulfilled:

0.33<

|φ

1/φ

w|<

0.50

where

φ

1 represents a refractive power of the first lens group, and

φ

w represents a refractive power of the entire projection lens system at the wide-angle end.

9. The projection lens system according to claim 2,

wherein

at least one of lens elements having a negative refractive power included in the fourth lens group fulfills conditional formulae (3) and (4) below:

0.645<

θ

g_—

F+0.001682×

ν

d<

0.695 

 

(3)

60<

ν

d<

100 

 

(4)

where

θ

g_F represents a partial dispersion ratio of a material of the lens element,

θ

g_—

F=(Ng−

NF)/(NF−

NC)

Ng represents a refractive index for a g-line,

NF represents a refractive index for an F-line,

NC represents a refractive index for a C-line, and

ν

d represents an Abbe number of the material of the lens element.

10. The projection lens system according to claim 2,

wherein

the first lens group includes at least one lens element having a positive refractive power;

and

conditional formula (5) below is fulfilled;

0.33<

|φ

1p/φ

1|<

0.59

where

φ

1p represents an average refractive power of a lens element having a positive refractive power included in the first lens group, and

φ

1 represents a refractive power of the first lens group.

11. The projection lens system according to claim 2,

wherein

conditional formula (6) below is fulfilled:

0.053<

φ

x×

|Δ

5|<

0.105

where

φ

x represents a composite refractive power, at the telephoto end, of from a lens group disposed to the reduction conjugate side of the aperture stop through the fifth lens group, and

Δ

5 represents a movement amount of the fifth lens group during zooming from the telephoto end to the wide-angle end.

20. The projection lens system according to claim 1,

wherein

a most enlargement-conjugate-side lens element in the first lens group has a negative refractive power.

21. The projection lens system according to claim 1,

wherein

conditional formula (1) below is fulfilled:

1.57<

np<

1.65

where

np represents an average value of refractive indices for a d-line of lens elements constituting the first lens group, the second lens group, and the third lens group.

22. The projection lens system according to claim 1,

wherein

the first lens group includes at least one lens element having a positive refractive power;

and

conditional formula (5) below is fulfilled;

0.33<

|φ

1p/φ

1|<

0.59

where

φ

1p represents an average refractive power of a lens element having a positive refractive power included in the first lens group, and

φ

1 represents a refractive power of the first lens group.

23. The projection lens system according to claim 1,

wherein

conditional formula (6) below is fulfilled:

0.053<

φ

x×

|Δ

5|<

0.105

where

φ

x represents a composite refractive power, at the telephoto end, of from a lens group disposed to the reduction conjugate side of the aperture stop through the fifth lens group, and

Δ

5 represents a movement amount of the fifth lens group during zooming from the telephoto end to the wide-angle end.

45. A projector, comprising:

an image display device that displays an image;

a light source;

an illumination optical system that directs light from the light source to the image display device; and

the projection lens system according to claim 1 which projects the image displayed on the image display device onto a screen surface on an enlarged scale.

5. (canceled)

12-19. -19. (canceled)

24. A projection lens system, comprising, in order from an enlargement conjugate side:

a first lens group having a negative refractive power;

a second lens group having a negative refractive power;

a third lens group having a positive refractive power;

a fourth lens group having a negative refractive power;

a fifth lens group; and

a sixth lens group having a positive refractive power,

the projection lens system achieving zooming by varying a distance between lens groups,

wherein

at least the second lens group, the third lens group, and the fifth lens group each move during zooming;

the third lens group moves from the enlargement conjugate side to a reduction conjugate side during zooming from a telephoto end to a wide-angle end;

an aperture stop is disposed between a most reduction-conjugate-side surface of the third lens group and a most enlargement-conjugate-side surface of the fifth lens group;

the projection lens system is substantially telecentric on the reduction conjugate side; and

conditional formula (1) below is fulfilled;

1.57<

np<

1.65

where

np represents an average value of refractive indices for a d-line of lens elements constituting the first lens group, the second lens group, and the third lens group.

25. The projection lens system according to claim 24,

wherein

the fifth lens group has a positive refractive power.

26. The projection lens system according to claim 25,

wherein

the first lens group remains stationary except during focusing;

and

in addition to the second lens group, the third lens group, and the fifth lens group, the fourth lens group moves during zooming from the telephoto end to the wide-angle end.

27. The projection lens system according to claim 25,

wherein

a most enlargement-conjugate-side lens element in the first lens group has a negative refractive power.

28. The projection lens system according to claim 25,

wherein

conditional formula (2) below is fulfilled:

0.33<

|φ

1/φ

w|<

0.50

where

φ

1 represents a refractive power of the first lens group, and

φ

w represents a refractive power of the entire projection lens system at the wide-angle end.

29. The projection lens system according to claim 25,

wherein

at least one of lens elements having a negative refractive power included in the fourth lens group fulfills conditional formulae (3) and (4) below:

0.645<

θ

g_—

F+0.001682×

ν

d<

0.695

60<

ν

d<

100

where

θ

g_F represents a partial dispersion ratio of a material of the lens element,

θ

g_—

F=(Ng−

NF)/(NF−

NC)

Ng represents a refractive index for a g-line,

NF represents a refractive index for an F-line,

NC represents a refractive index for a C-line, and

ν

d represents an Abbe number of the material of the lens element.

30. The projection lens system according to claim 25,

wherein

the first lens group includes at least one lens element having a positive refractive power;

and

conditional formula (5) below is fulfilled;

0.33<

|φ

1p/φ

1|<

0.59

where

φ

1p represents an average refractive power of a lens element having a positive refractive power included in the first lens group, and

φ

1 represents a refractive power of the first lens group.

31. The projection lens system according to claim 25,

wherein

conditional formula (6) below is fulfilled:

0.053<

φ

x×

|Δ

5|<

0.105

where

φ

x represents a composite refractive power, at the telephoto end, of from a lens group disposed to the reduction conjugate side of the aperture stop through the fifth lens group, and

Δ

5 represents a movement amount of the fifth lens group during zooming from the telephoto end to the wide-angle end.

32. The projection lens system according to claim 24,

wherein

conditional formula (6) below is fulfilled:

0.053<

φ

x×

|Δ

5|<

0.105

where

φ

x represents a composite refractive power, at the telephoto end, of from a lens group disposed to the reduction conjugate side of the aperture stop through the fifth lens group, and

Δ

5 represents a movement amount of the fifth lens group during zooming from the telephoto end to the wide-angle end.

33. A projection lens system, comprising, in order from an enlargement conjugate side:

a first lens group having a negative refractive power;

a second lens group having a negative refractive power;

a third lens group having a positive refractive power;

a fourth lens group having a negative refractive power;

a fifth lens group; and

a sixth lens group having a positive refractive power,

the projection lens system achieving zooming by varying a distance between lens groups,

wherein

at least the second lens group, the third lens group, and the fifth lens group each move during zooming;

the third lens group moves from the enlargement conjugate side to a reduction conjugate side during zooming from a telephoto end to a wide-angle end;

an aperture stop is disposed between a most reduction-conjugate-side surface of the third lens group and a most enlargement-conjugate-side surface of the fifth lens group;

the projection lens system is substantially telecentric on the reduction conjugate side; and

conditional formula (6) below is fulfilled;

0.053<

φ

x×

|Δ

5|<

0.105

where

φ

x represents a composite refractive power, at the telephoto end, of from a lens group disposed to the reduction conjugate side of the aperture stop through the fifth lens group, and

Δ

5 represents a movement amount of the fifth lens group during zooming from the telephoto end to the wide-angle end.

34. The projection lens system according to claim 33,

wherein

the fifth lens group has a positive refractive power.

35. The projection lens system according to claim 34,

wherein

the first lens group remains stationary except during focusing;

and

in addition to the second lens group, the third lens group, and the fifth lens group, the fourth lens group moves during zooming from the telephoto end to the wide-angle end.

36. The projection lens system according to claim 34,

wherein

a most enlargement-conjugate-side lens element in the first lens group has a negative refractive power.

37. The projection lens system according to claim 34,

wherein

the first lens group includes at least one lens element having a positive refractive power;

and

conditional formula (5) below is fulfilled;

0.33<

|φ

1p/φ

1|<

0.59

where

φ

1p represents an average refractive power of a lens element having a positive refractive power included in the first lens group, and

φ

1 represents a refractive power of the first lens group.

38. A projection lens system, comprising, in order from an enlargement conjugate side:

a first lens group having a negative refractive power;

a second lens group having a negative refractive power;

a third lens group having a positive refractive power;

a fourth lens group having a negative refractive power;

a fifth lens group; and

a sixth lens group having a positive refractive power,

the projection lens system achieving zooming by varying a distance between lens groups,

wherein

at least the second lens group, the third lens group, and the fifth lens group each move during zooming;

the third lens group moves from the enlargement conjugate side to a reduction conjugate side during zooming from a telephoto end to a wide-angle end;

an aperture stop is disposed between a most reduction-conjugate-side surface of the third lens group and a most enlargement-conjugate-side surface of the fifth lens group;

the projection lens system is substantially telecentric on the reduction conjugate side; and

the fifth lens group has a negative refractive power or is afocal.

39. The projection lens system according to claim 38,

wherein

the first lens group remains stationary except during focusing.

40. The projection lens system according to claim 38,

wherein

the first lens group remains stationary except during focusing;

and

in addition to the second lens group, the third lens group, and the fifth lens group, the fourth lens group moves during zooming from the telephoto end to the wide-angle end.

41. The projection lens system according to claim 38,

wherein

a most enlargement-conjugate-side lens element in the first lens group has a negative refractive power.

42. The projection lens system according to claim 38,

wherein

conditional formula (1) below is fulfilled:

1.57<

np<

1.65

where

np represents an average value of refractive indices for a d-line of lens elements constituting the first lens group, the second lens group, and the third lens group.

43. The projection lens system according to claim 38,

wherein

conditional formula (2) below is fulfilled:

0.33<

|φ

1/φ

w|<

0.50

where

φ

1 represents a refractive power of the first lens group, and

φ

w represents a refractive power of the entire projection lens system at the wide-angle end.

44. The projection lens system according to claim 38,

wherein

the fourth lens group includes, in order from the enlargement conjugate side, one or more negative lens elements and a positive lens element;

and

at least one lens element having a negative refractive power included in the fourth lens group fulfills conditional formulae (3) and (4) below;

0.645<

θ

g_—

F+0.001682×

ν

d<

0.695

60<

ν

d<

100

where

θ

g_F represents a partial dispersion ratio of a material of the lens element,

θ

g_—

F=(Ng−

NF)/(NF−

NC)

Ng represents a refractive index for a g-line,

NF represents a refractive index for an F-line,

NC represents a refractive index for a C-line, and

ν

d represents an Abbe number of the material of the lens element.

46. A projector, comprising:

an image display device that displays an image;

a light source;

an illumination optical system that directs light from the light source to the image display device; and

the projection lens system according to claim 38 which projects the image displayed on the image display device onto a screen surface on an enlarged scale.