Projection optical unit and projection type video display device using the unit

• US 20060227299A1
• Filed: 10/26/2005
• Published: 10/12/2006
• Est. Priority Date: 04/08/2005
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yoshikawa, Hiroki, Yatsu, Masahiko, Hirata, Koji, Hisada, Takanori, Ohishi, Tetsu
• Granted Patent: US 7,467,872 B2
• Time in Patent Office: Days
• US Class Current: 353/77
• 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 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G03B 21/10 Projectors with built-in or built-on screen

Abstract

In the image display device, a projection lens including a plurality of lenses for enlarging an image from an image display element is constituted of a front group and a rear group. The rear group includes at least one free-shaped-surface lens including a surface having a rotationally asymmetrical shape. Furthermore, the device includes at least one free-shaped-surface mirror having a rotationally asymmetrical reflection surface. Accordingly, a set can be formed to be compact while correcting trapezoidal distortion and aberration.

Claims

1. A projection type image display device comprising:

an image display element;

a screen; and

a projection lens including a plurality of lenses for enlarging an image displayed in the image display element to project the image at a predetermined angle with respect to a normal of a main plane of the screen,

wherein the projection lens includes at least one asymmetrical lens directing a concave portion in an emission direction of light and having a rotationally asymmetrical shape.

2. The projection type image display device according to claim 1, wherein a curvature of a portion of the asymmetrical lens which passes a ray entering a lower end of the screen is larger than that of a portion of the lens which passes a ray entering an upper end of the screen.

3. The projection type image display device according to claim 1, wherein the projection lens includes at least one rotationally symmetrical spherical lens and at least one rotationally symmetrical non-spherical lens in addition to the asymmetrical lens.

4. The projection type image display device according to claim 1, further comprising:

a reflection mirror which reflects the lens emitted from the projection lens, the reflection mirror being a rotationally asymmetrical convex reflection mirror a part of which directs a convex portion in a reflection direction.

5. The projection type image display device according to claim 4, wherein a curvature of a portion of the convex reflection mirror which reflects a ray entering a lower end of the screen is larger than that of a portion of the mirror which reflects a ray entering an upper end of the screen.

6. The projection type image display device according to claim 4, wherein the portion of the convex reflection mirror which reflects the ray entering the lower end of the screen has a convex shape in a reflection direction, and the portion of the mirror which reflects the ray entering the upper end of the screen forms a concave shape in the reflection direction.

7. An projection optical unit for use in a projection type image display device, comprising:

an image display element;

a screen;

a projection lens including a plurality of lenses for enlarging an image displayed in the image display element; and

a reflection mirror for reflecting light from the projection lens to project the light from an oblique direction to the screen,

wherein the projection optical unit includes at least one free-shaped-surface lens having a rotationally asymmetrical shape, and the reflection mirror includes at least one free-shaped-surface mirror having a rotationally asymmetrical reflection surface.

8. A projection optical unit for use in a projection type image display device, comprising:

a first optical system including at least one free-shaped-surface lens having a rotationally asymmetrical free shaped surface for enlarging light from an image display element; and

a second optical system including at least one free-shaped-surface mirror having a rotationally asymmetrical free shaped reflection surface for reflecting the light from the first optical system,

wherein a picture plane center ray emitted from a center of a display picture plane of the image display element passes through the first optical system, the second optical system, and a flat reflection mirror to enter the screen obliquely with respect to a normal of the screen in a case where the light reflected by the free-shaped-surface mirror of the second optical system is reflected by the flat reflection mirror and projected onto the screen.

9. The projection type image display device according to claim 8, wherein the first optical system includes a front group including lenses having rotationally symmetrical shapes, and a rear group including the free-shaped-surface lenses.

10. The projection type image display device according to claim 9, wherein assuming that a distance of a path of a ray entering an upper end of the screen from the reflection surface of the second optical system is L1, a distance of a path of a ray entering a lower end of the screen from the reflection surface of the second optical system is L2, a distance between the upper end and the lower end of the picture plane of the screen is Dv, and an angle formed by the picture plane center ray and the normal of the screen is Os in a plane including the picture plane center ray and the normal of the screen in a position where the picture plane center ray enters, the following expression is satisfied:

|L1−

L2|<

1.2*sin θ

s*Dv.

11. The projection type image display device according to claim 9, wherein the normal of the display plane center of the image display element substantially disposed on the optical axis of the first optical system is inclined with respect to the optical axis of the first optical system.

12. The projection type image display device according to claim 9, wherein an optical path length ranging from a final surface of the front group to the reflection surface of the second optical system is five or more times a focal distance of the front group in the path of the picture plane center ray traveling to the screen.

13. The projection type image display device according to claim 9, wherein a shape of the reflection surface of the second optical system in a first position whose optical distance to the screen is closest has a convex shape in a reflection direction, a shape of the reflection surface of the system in a second position whose optical distance to the screen is farthest has a convex shape in the reflection direction, and a curvature of the convex shape of the second position is smaller than that of the convex shape of the second position.

14. The projection type image display device according to claim 9, wherein a shape of the reflection surface of the second optical system in a first position whose optical distance to the screen is closest has a convex shape in a reflection direction, and a shape of the reflection surface of the system in a second position whose optical distance to the screen is farthest has a concave shape in the reflection direction.

15. The projection type image display device according to claim 10, wherein assuming that an angle formed by the picture plane center ray and the normal of the screen is θ

s, and an angle formed by the normal of the free-shaped-surface mirror and the picture plane center ray is θ

m in a position of the free-shaped-surface mirror where the picture plane center ray enters, the following expression is satisfied;

θ

s+2*θ

m2<

95.

16. The projection type image display device according to claim 9, wherein a mirror is disposed midway in the front group, and an optical axis of a lens which passes light entering the mirror crosses that of a lens which passes light emitted from the mirror substantially at right angles.

17. The projection type image display device according to claim 8, wherein the image display element is disposed in such a manner that the center of the display picture plane of the image display element is positioned on the optical axis of the first optical system in the projection optical unit according to claim 8.

18. A projection type image display device comprising:

a first optical system including at least one free-shaped-surface lens having a rotationally asymmetrical free shaped surface for enlarging light from an image display element; and

a second optical system including at least one free-shaped-surface mirror having a rotationally asymmetrical free shaped reflection surface for reflecting light from the first optical system,

wherein a picture plane center ray emitted from a center of a display picture plane of the image display element passes through the first optical system, the second optical system, and a flat reflection mirror to enter the screen obliquely with respect to a normal of the screen in a case where the light reflected by the free-shaped-surface mirror of the second optical system is reflected by the flat reflection mirror and projected onto the screen, and

assuming that a distance of a path of a ray entering an upper end of the screen from the reflection surface of the second optical system is L1, a distance of a path of a ray entering a lower end of the screen from the reflection surface of the second optical system is L2, a distance between the upper end and the lower end of the picture plane of the screen is Dv, and an angle formed by the picture plane center ray and the normal of the screen is θ

s in a plane including the picture plane center ray and the normal of the screen in a position where the picture plane center ray enters, the following expression is satisfied;

|L1−

L2|<

1.2*sin θ

s*Dv.