PROJECTION OPTICAL SYSTEM AND PROJECTION IMAGE DISPLAY APPARATUS

• US 20080158439A1
• Filed: 10/08/2007
• Published: 07/03/2008
• Est. Priority Date: 11/06/2006
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: NISHIKAWA, Jun
• Granted Patent: US 8,107,163 B2
• Time in Patent Office: Days
• US Class Current: 348/744
• CPC Class Codes: G02B 17/08 Catadioptric systems used in non-imaging applications G02B19/00
• CPC Class Codes: G02B 17/0852 having a field corrector only
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• CPC Class Codes: H04N 5/7408 Direct viewing projectors, e.g. an image displayed on a video CRT or LCD display being projected on a screen

Abstract

A projection optical system for magnifying an image on a primary imaging plane onto a secondary imaging plane includes a first optical system for forming an intermediate image and a second optical system including a concave reflecting surface disposed between the intermediate image and the secondary plane. The first optical system includes first and second groups respectively having negative and positive power, an aperture, and a third group having positive power from the intermediate image. The surfaces of the first and second optical systems have rotational symmetry about a light axis. A ray traveling from the center of the primary plane to the center of the secondary plane intersects the light axis, is reflected off the reflecting surface, intersects the light axis again, and reaches the secondary plane. The following conditions are satisfied: 0.5<φ1/φ2<3, 1<AST/ASS<5, |AST|/L12<1, and −3<K_rel.

Claims

1. A projection optical system for magnifying an image on a primary imaging plane on a reduction side onto a secondary imaging plane on a magnification side, comprising:

a first optical system configured to form an intermediate image of the primary imaging plane, the first optical system including a first group having a negative refractive power, a second group having a positive refractive power, an aperture, and a third group having a positive refractive power in this order from the intermediate image adjacent to the aperture; and

a second optical system including a concave reflecting surface disposed between the intermediate image and the secondary imaging plane;

wherein each of surfaces of the first optical system and the second optical system has rotational symmetry with respect to a light axis that is common to all of the surfaces, a light ray traveling from the center of the primary imaging plane to the center of the secondary imaging plane intersects the light axis, is reflected off the concave reflecting surface, intersects the light axis again, and reaches the secondary imaging plane, and wherein the following conditional expressions are satisfied;

0.5<

φ

1/φ

2<

3 

 

(1)

1<

AST/ASS<

5 

 

(2)

|AST|/L12<

1 

 

(3)

where

φ

1=refractive power of the first optical system,

φ

2=refractive power of the second optical system,

|AST|=position at which the intermediate image is formed in the tangential plane by the first optical system,

|ASS|=position at which the intermediate image is formed in the sagittal plane by the first optical system, and

L12=distance between the first optical system and the second optical system on the light axis, and wherein all of lenses included in the first optical system and having a positive refractive power satisfy the following conditional expression;

−

3<

K_—

rel 

 

(4)

where

K_rel=temperature coefficient of the index of refraction.

2. The projection optical system according to claim 1, wherein at least one positive lens included in the third group satisfies the following conditional expression:

0.7<

Δ

P 

 

(5)

and at least one negative lens included in the third group satisfies the following conditional expression;

Δ

P<

−

0.3 

 

(6)

where

Δ

P={ν

−

(−

0.001917 ×

P+0.6568)}×

100,

ν

=(nd−

1)/(nF−

nC),

P=(ng−

nF)/(nF−

nC),

ng=the index of refraction of the g-line having a wavelength of 435.83 nm,

nF=the index of refraction of the F-line having a wavelength of 486.13 nm,

nd=the index of refraction of the d-line having a wavelength of 587.56 nm, and

nC=the index of refraction of the C-line having a wavelength of 656.27 nm.

3. The projection optical system according to claim 2, wherein the first optical system includes at least one pair of cemented lenses and satisfies the following conditional expression:

|Δ

α

|<

45 

 

(7)

where

|Δ

α

|=a difference in coefficient of linear expansion between adjacent glass pieces having a contact surface therebetween.

4. The projection optical system according to claim 1, wherein an aspherical plastic lens is disposed in any one of the first group to the third group of the first optical system and the following conditional expressions are satisfied:

−

0.3<

φ

_—

p1/φ

1<

0.05 

 

(8)

−

35<

β

<

35 

 

(9)

where

φ

_p1=the refraction power of the aspherical plastic lens,

φ

1=the refraction power of the first optical system, and

β

=a maximum angle of tangent of the curved surface of the aspherical plastic lens.

5. The projection optical system according to claim 1, wherein, when a projection screen size is changed, a distance between the second optical system and the secondary imaging plane is changed, and at least one of the groups of the first optical system or some of the lenses of the groups and the concave reflecting surface of the second optical system are moved along the light axis parallel to the light axis.

6. A projection image display apparatus comprising:

a light source;

modulating means for modulating light emitted from the light source on the basis of a video signal and outputting the modulated light; and

a projection optical system for magnifying an image on a primary imaging plane on a side of the modulating means onto a secondary imaging plane on a side of a screen;

wherein the projection optical system is the projection optical system according to any one of claims 1 to 5.

7. A projection image display apparatus comprising:

a light source;

a modulating unit configured to modulate light emitted from the light source on the basis of a video signal and output the modulated light; and

a projection optical system configured to magnify an image on a primary imaging plane on a side of the modulating unit onto a secondary imaging plane on a side of a screen;

wherein the projection optical system is the projection optical system according to any one of claims 1 to 5.