Projection optical system, magnification projection optical system, magnification projection apparatus, and image projection apparatus

• US 7,048,388 B2
• Filed: 02/05/2004
• Issued: 05/23/2006
• Est. Priority Date: 02/06/2003
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Takaura, Atsushi, Fujita, Kazuhiro, Sakuma, Nobuo
• Primary Examiner(s): KOVAL, MELISSA J
• Application Number:
  US10/771,523
• Publication Number:
  US 20040156117A1
• Time in Patent Office: 838 Days
• Field of Search: 353/30, 353/37, 353/69, 353/70, 353/77, 353/99, 353/102, 353/31, 359/663, 359/668, 359/727, 359/730, 359/731
• US Class Current: 353/99
• 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 17/0816 off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements
• CPC Class Codes: G02B 17/0848 off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements
• CPC Class Codes: G02B 17/0852 having a field corrector only
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066

Abstract

A projection optical system guiding and projecting a light beam from a projected object surface onto a projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system. An intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as the final image on the projection surface via the reflecting mirrors, which include at least one anamorphic polynomial free-formed surface having different vertical and lateral powers. A light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface and the transmission dioptric system is decentered with respect to a normal of the projected object surface, the transmission refractive elements prevented from being decentered with respect to each other.

Claims

1. A projection optical system guiding and projecting a light beam from a projected object surface onto a projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors, wherein:

the transmission dioptric system includes a plurality of transmission refractive elements;

substantial telecentricity is provided from the projected object surface up to a first surface of the transmission dioptric system;

an intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as a final image on the projection surface via the reflecting mirrors;

the reflecting mirrors include at least one anamorphic polynomial free-form surface having different vertical and lateral powers;

a light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface; and

the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other.

2. The projection optical system as claimed in claim 1, wherein:

the reflection dioptric system includes first and second reflecting mirrors arranged in an order described from upstream to downstream on a downstream side of the transmission dioptric system;

the intermediate image surface of the projected object surface is positioned between the first and second reflecting mirrors; and

the first reflecting mirror includes an axially symmetric reflecting surface having negative power, and the second reflecting mirror includes an anamorphic polynomial free-form surface having different vertical and lateral powers.

3. The projection optical system as claimed in claim 1, comprising an anamorphic polynomial free-form surface having different vertical and lateral powers in the transmission dioptric system as a part correcting an aspect ratio of the intermediate image of the projected object surface.

4. The projection optical system as claimed in claim 1, wherein an NA in the transmission dioptric system is greater on an upstream side thereof than on the downstream side thereof.

5. The projection optical system as claimed in claim 1, wherein the intermediate image surface is tilted and curved with respect to a principal ray of a light beam emitted from a center of the projected object surface.

6. The projection optical system as claimed in claim 1, wherein a principal ray emitted from a center of the projected object surface and a principal ray emitted from a margin of the projected object surface are parallel to each other in a last surface of the transmission dioptric system.

7. The projection optical system as claimed in claim 1, wherein magnification of the intermediate image falls in a range of 1 to 5.

8. The projection optical system as claimed in claim 1, wherein magnification of projection is 40×

or higher.

9. The projection optical system as claimed in claim 8, wherein an angle of projection to the projection surface is 5°

or greater.

10. A projection optical system guiding and projecting a light beam from a projected object surface onto a projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors, wherein:

the transmission dioptric system includes a plurality of transmission refractive elements;

substantial telecentricity is provided from the projected object surface up to a first surface of the transmission dioptric system;

an intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as a final image on the projection surface via the reflecting mirrors;

the reflecting mirrors include at least one anamorphic polynomial free-form surface having different vertical and lateral powers;

a light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface; and

the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other at a group unit level.

11. The projection optical system as claimed in claim 10, wherein:

the reflection dioptric system includes first and second reflecting mirrors arranged in an order described from upstream to downstream on a downstream side of the transmission dioptric system;

the intermediate image surface of the projected object surface is positioned between the first and second reflecting mirrors; and

the first reflecting mirror includes an axially symmetric reflecting surface having negative power, and the second reflecting mirror includes an anamorphic polynomial free-form surface having different vertical and lateral powers.

12. The projection optical system as claimed in claim 10, comprising an anamorphic polynomial free-form surface having different vertical and lateral powers in the transmission dioptric system as a part correcting an aspect ratio of the intermediate image of the projected object surface.

13. The projection optical system as claimed in claim 10, wherein an NA in the transmission dioptric system is greater on an upstream side thereof than on the downstream side thereof.

14. The projection optical system as claimed in claim 10, wherein the intermediate image surface is tilted and curved with respect to a principal ray of a light beam emitted from a center of the projected object surface.

15. The projection optical system as claimed in claim 10, wherein a principal ray emitted from a center of the projected object surface and a principal ray emitted from a margin of the projected object surface are parallel to each other in a last surface of the transmission dioptric system.

16. The projection optical system as claimed in claim 10, wherein magnification of the intermediate image falls in a range of 1 to 5.

17. The projection optical system as claimed in claim 10, wherein magnification of projection is 40×

or higher.

18. The projection optical system as claimed in claim 17, wherein an angle of projection to the projection surface is 5°

or greater.

19. An image projection apparatus magnifying an image displayed on a projected object surface and projecting the magnified image on a projection surface by a projection optical system, wherein:

the projection optical system guides and projects a light beam from the projected object surface onto the projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors;

the transmission dioptric system includes a plurality of transmission refractive elements;

substantial telecentricity is provided from the projected object surface up to a first surface of the transmission dioptric system;

an intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as a final image on the projection surface via the reflecting mirrors;

the reflecting mirrors include at least one anamorphic polynomial free-form surface having different vertical and lateral powers;

a light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface; and

the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other.

20. The image projection apparatus as claimed in claim 19, wherein the image projection apparatus is of a front projector type.

21. The image projection apparatus as claimed in claim 19, wherein the image projection apparatus is of a rear projector type, comprising a folding mirror folding back an imaging optical path.

22. An image projection apparatus magnifying an image displayed on a projected object surface and projecting the magnified image on a projection surface by a projection optical system, wherein:

the projection optical system guides and projects a light beam from the projected object surface onto the projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors;

the transmission dioptric system includes a plurality of transmission refractive elements;

substantial telecentricity is provided from the projected object surface up to a first surface of the transmission dioptric system;

an intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as a final image on the projection surface via the reflecting mirrors;

the reflecting mirrors include at least one anamorphic polynomial free-form surface having different vertical and lateral powers;

a light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface; and

the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other at a group unit level.

23. The image projection apparatus as claimed in claim 22, wherein the image projection apparatus is of a front projector type.

24. The image projection apparatus as claimed in claim 22, wherein the image projection apparatus is of a rear projector type, comprising a folding mirror folding back an imaging optical path.