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

• US 7,631,975 B2
• Filed: 09/19/2008
• Issued: 12/15/2009
• 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:
  US12/233,653
• Publication Number:
  US 20090015801A1
• Time in Patent Office: 452 Days
• Field of Search: 353/30, 353/31, 353/34, 353/37, 353/69, 353/70, 353 77- 79, 353/99, 353/102, 359/449, 359/648, 359/650, 359656-661, 359/663, 359/668, 359726-731, 359/739
• 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 for use in an image projection apparatus illuminating an image display panel forming an image in accordance with a modulating signal with illumination light from a light source. 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 image display panel. 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 image display panel is formed as an intermediate image in the optical path, and the intermediate image is magnified and projected.

Claims

1. A magnification projection optical system that guides a light beam from an image display panel to a screen in an upstream-downstream direction, projects the light beam from a direction inclined to a normal of the screen, and forms on the screen a magnified version of an image displayed on the image display panel, the magnification projection optical system comprising:

a transmission optical system including a plurality of transmitting surfaces;

a reflection optical system including a plurality of reflecting surfaces; and

a diaphragm,

wherein one of the reflecting surfaces, on which a light beam passing through the diaphragm is made incident first, has negative power, and

wherein another one of the reflecting surfaces, which another one is subsequent to the one having negative power, has positive power.

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

the reflecting surfaces of the reflection optical system have power and include at least one rotationally asymmetric reflecting surface; and

the transmitting surfaces of the transmission optical system have refractive power and include at least one aspheric surface.

3. The magnification projection optical system as claimed in claim 2, wherein the rotationally asymmetric reflecting surface is positioned at a furthest downstream end of the second optical system in a projection optical path.

4. The magnification projection optical system as claimed in claim 1, wherein the transmission optical system includes a rotationally asymmetric transmitting surface having refractive power.

5. The magnification projection optical system as claimed in claim 1, wherein the transmission optical system has an optical axis set to be decentered with respect to a position of the image display panel in a plane including a light guide path.

6. The magnification projection optical system as claimed in claim 1, wherein the reflection optical system is formed as a unit.