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

• US 7,938,545 B2
• Filed: 10/21/2010
• Issued: 05/10/2011
• 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): Dowling; William C
• Application Number:
  US12/909,540
• Publication Number:
  US 20110038039A1
• Time in Patent Office: 201 Days
• Field of Search: 353/70, 353/77, 353/78, 353/98, 353/99, 349/5, 349/7, 348/742, 348/743
• US Class Current: 353/70
• 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 for use in an image projection apparatus illuminating a lightbulb forming an image in accordance with a modulating signal with illumination light from a light source is disclosed. The projection optical system includes first and second optical systems arranged along an optical path defining an upstream-downstream direction in the order described from upstream to downstream on the downstream side of the lightbulb. The first optical system includes at least one dioptric system and has positive power. The second optical system includes at least one reflecting surface having power and has positive power. The image formed by the lightbulb is formed as an intermediate image in the optical path, and the intermediate image is magnified and projected.

Claims

1. A projection optical system configured to project an image of an object and form a final image on a plane, the projection optical system comprising:

a first optical system including at least one dioptric system;

a reflection part provided in an optical path of output light output from the first optical system;

a second optical system provided in an optical path of light reflected from the reflection part, the second optical system including a reflecting surface having positive power,

wherein the image of the object is formed as an intermediate image in an optical path of the first optical system, the reflection part, and the second optical system, and the intermediate image is magnified and projected, and

the reflection part, the first optical system, and the second optical system are arranged at respective positions so that the reflection part is closer to a plane on which the final image is formed than is the first optical system, and the first optical system is closer to the plane than is the second optical system.

5. An image projection apparatus, comprising:

an image forming part configured to be illuminated with illumination light to form an image of an object; and

the projection optical system as set forth in claim 1.

2. A projection optical system configured to project an image of an object and form a final image on a plane, the projection optical system comprising:

a first optical system including a plurality of dioptric elements;

a second optical system provided in an optical path of output light output from the first optical system, the second optical system including at least one reflecting surface having positive power,

wherein the image of the object is formed as an intermediate image in an optical path of the first optical system and the second optical system, and the intermediate image is magnified and projected, and

one of the dioptric elements at an end of the first optical system on a light output side is a lens having negative power.

3. The projection optical system as claimed in claim 2, wherein the light output from the first optical system is output in a spreading manner from the one of the dioptric elements at the end of the first optical system on the light output side.

6. An image projection apparatus, comprising:

an image forming part configured to be illuminated with illumination light to form an image of an object; and

the projection optical system as set forth in claim 2.

4. A projection optical system configured to project an image of an object and form a final image on a plane, the projection optical system comprising:

a first optical system including a plurality of dioptric elements;

a second optical system provided in an optical path of output light output from the first optical system, the second optical system including at least one reflecting surface having positive power,

wherein the image of the object is formed as an intermediate image in an optical path of the first optical system and the second optical system, and the intermediate image is magnified and projected, and

one of the dioptric elements at an end of the first optical system on a light output side is a meniscus lens.

7. An image projection apparatus, comprising:

an image forming part configured to be illuminated with illumination light to form an image of an object; and

the projection optical system as set forth in claim 4.