PROJECTION OPTICAL SYSTEM AND PROJECTOR APPARATUS

• US 20140268073A1
• Filed: 03/11/2014
• Published: 09/18/2014
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Takano, Yohei
• Granted Patent: US 9,244,257 B2
• Time in Patent Office: Days
• US Class Current: 353/99
• CPC Class Codes: G02B 13/006 at least one element being a compound optical element, e.g. cemented elements
• CPC Class Codes: G02B 13/0065 having a beam-folding prism or mirror
• 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 17/08 Catadioptric systems used in non-imaging applications G02B19/00
• 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: G02B 17/0896 with variable magnification or multiple imaging planes, including multispectral systems systems with only refractive elements G02B15/14
• CPC Class Codes: G03B 21/147 Optical correction of image distortions, e.g. keystone
• CPC Class Codes: G03B 21/208 Homogenising, shaping of the illumination light
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066

Abstract

A projection optical system comprises an image forming unit that forms an image; a refractive optical system including a plurality of lenses that enlarges and projects the image on a screen; and a reflecting surface, wherein an intermediate image is formed between the refractive optical system and the reflecting surface, and the projection optical system satisfies conditions of “0.6<D/Did<0.8” and “2.5<Did/F<6”, where “Did” represents a maximum paraxial image height of the intermediate image in a focusing state in which a projection image is maximum, “D” represents a maximum value of a distance between an optical axis and an intersection of a paraxial image surface and a light beam passing center of an aperture stop of the refractive optical system, and “F” represents a focal length of the refractive optical system in a focusing state in which the projection image is maximum.

Claims

1. A projection optical system comprising in this order:

an image forming unit that forms an image;

a refractive optical system including a plurality of lenses that enlarges and projects the image on a screen; and

a reflecting surface, wherein

an intermediate image is formed between the refractive optical system and the reflecting surface, and

the projection optical system satisfies conditions of “

0.6<

D/Did<

0.8” and

“

2.5<

Did/F<

6”

, where

“

Did”

represents a maximum paraxial image height of the intermediate image in a focusing state in which a projection image is maximum,

“

D”

represents a maximum value of a distance between an optical axis and an intersection of a paraxial image surface and a light beam passing center of an aperture stop of the refractive optical system, and

“

F”

represents a focal length of the refractive optical system in a focusing state in which the projection image is maximum.

2. The projection optical system according to claim 1, wherein

the projection optical system satisfies a condition of “

5<

β

<

8”

, where “

β

”

represents a paraxial magnification of the refractive optical system in the focusing state in which the projection image is maximum.

3. The projection optical system according to claim 1, wherein

the projection optical system satisfies a condition of “

0.4<

Y/F<

0.75”

, where “

Y”

represents a maximum value of a distance between the optical axis and an end of the image forming unit.

4. The projection optical system according to claim 1, wherein

the stop is fixed relative to the image forming unit in the focusing state.

5. The projection optical system according to claim 1, wherein

the reflecting surface is a concave surface mirror positioned at a most magnification side.

6. The projection optical system according to claim 5, wherein

the concave surface mirror includes a free curved surface.

7. The projection optical system according to claim 1, wherein

the refractive optical system includes at least one aspheric surface lens.

8. The projection optical system according to claim 1, further comprises a reflecting mirror that is arranged between the refractive optical system and the reflecting surface.

9. A projector apparatus comprising a projection optical system, wherein the projection optical system comprises in this order:

an image forming unit that forms an image;

a refractive optical system including a plurality of lenses that enlarges and projects the image on a screen; and

a reflecting surface, wherein

an intermediate image is formed between the refractive optical system and the reflecting surface, and

the projection optical system satisfies conditions of “

0.6<

D/Did<

0.8” and

“

2.5<

Did/F<

6”

, where

“

Did”

represents a maximum paraxial image height of the intermediate image in a focusing state in which a projection image is maximum,

“

D”

represents a maximum value of a distance between an optical axis and an intersection of a paraxial image surface and a light beam passing center of an aperture stop of the refractive optical system, and

“

F”

represents a focal length of the refractive optical system in a focusing state in which the projection image is maximum.