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

• US 7,637,621 B2
• Filed: 09/19/2008
• Issued: 12/29/2009
• 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:
  US12/233,650
• Publication Number:
  US 20090021703A1
• Time in Patent Office: 466 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, 359/649, 359/650, 359656-661, 359/663, 359/668, 359726-731
• 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 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 reflection optical system; and

a transmission optical system,

wherein the reflection optical system includes a plurality of reflecting surfaces having power and includes at least one rotationally asymmetric reflecting surface;

the transmission optical system includes a transmitting surface having refractive power and includes at least one aspheric surface, and

wherein a diaphragm is provided between a first surface of the transmission optical system from an upstream side thereof and a first surface of the reflection optical system from a downstream side thereof so that an image of the diaphragm is formed with negative reducing magnification by an optical element provided on a downstream side of the diaphragm.

2. The magnification projection optical system as claimed in claim 1, wherein the rotationally asymmetric reflecting surface is positioned at a furthest downstream end of the second optical system in a projection optical path.

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

4. 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.

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