Projection optical system having an aperture to limit quantity of light to a refractive optical system, and image display device using the same

• US 8,901,473 B2
• Filed: 10/24/2012
• Issued: 12/02/2014
• Est. Priority Date: 10/28/2011
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Tatsuno, Hibiki
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US13/659,104
• Publication Number:
  US 20130107232A1
• Time in Patent Office: 769 Days
• Field of Search: 250/208.1, 250/216, 250/239, 359649-651, 359726-738, 353/79, 353/98, 353/99, 353/119
• US Class Current: 250/208.1
• 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 17/0852 having a field corrector only
• CPC Class Codes: G03B 21/008 using micromirror devices
• CPC Class Codes: G03B 21/14 Details
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066

Abstract

A projection optical system that is used for an image display device having an image display element, includes a refractive optical system that includes a plurality of lenses; an aperture that limits a quantity of light led to the refractive optical system from the image display element; a lens group that is arranged between the image display element and the aperture, has a positive refractive power, and has low field curvature with respect to the image display element; and a mirror optical system that has a concave mirror arranged on an opposite side from the image display element across the refractive optical system, the aperture, and the lens group.

Claims

1. A projection optical system that is used for an image display device having an image display element, comprising:

a refractive optical system that includes a plurality of lenses;

an aperture that limits a quantity of light led to the refractive optical system from the image display element;

a lens group that is arranged between the image display element and the aperture, has a positive refractive power, and has low field curvature with respect to the image display element; and

a mirror optical system that has a concave mirror arranged on an opposite side from the image display element across the refractive optical system, the aperture, and the lens group.

2. The projection optical system according to claim 1, wherein one convex lens constitutes the lens group.

3. The projection optical system according to claim 1, wherein from a side of the image display element, three lenses arranged in order of a positive lens, a negative lens, and a positive lens constitute the lens group.

4. The projection optical system according to claim 2, wherein at least one surface of a positive lens constituting the lens group has an aspherical shape, and an aspherical surface of the positive lens has a shape that functions to make field curvature lower than a spherical shape having a paraxial curvature radius.

5. The projection optical system according to claim 3, wherein at least one surface of a positive lens constituting the lens group has an aspherical shape, and an aspherical surface of the positive lens has a shape that functions to make field curvature lower than a spherical shape having a paraxial curvature radius.

6. The projection optical system according to claim 1, comprising:

a flat mirror on a light path between the concave mirror and the refractive optical system.

7. The projection optical system according to claim 1, wherein the lens group is fixed when zooming and focusing are performed.

8. An image display device comprising:

an image display element;

a light source;

an illumination optical system that leads light emitted from the light source to the image display element;

a projection optical system that projects an image displayed on the image display element and forms the image; and

a dust-proof member that is provided on a side of the projection optical system where an imaging luminous flux is emitted,

the projection optical system including;

a refractive optical system that includes a plurality of lenses;

an aperture that limits a quantity of light led to the refractive optical system from the image display element;

a lens group that is arranged between the image display element and the aperture, has a positive refractive power, and has low field curvature with respect to the image display element; and

a mirror optical system that has a concave mirror arranged on an opposite side from the image display element across the refractive optical system, the aperture, and the lens group.

9. The image display device according to claim 8, wherein one convex lens constitutes the lens group.

10. The image display device according to claim 8, wherein from a side of the image display element, three lenses arranged in order of a positive lens, a negative lens, and a positive lens constitute the lens group.

11. The image display device according to claim 9, wherein at least one surface of a positive lens constituting the lens group has an aspherical shape, and an aspherical surface of the positive lens has a shape that functions to make field curvature lower than a spherical shape having a paraxial curvature radius.

12. The image display device according to claim 10, wherein at least one surface of a positive lens constituting the lens group has an aspherical shape, and an aspherical surface of the positive lens has a shape that functions to make field curvature lower than a spherical shape having a paraxial curvature radius.

13. The image display device according to claim 8, comprising:

a flat mirror on a light path between the concave mirror and the refractive optical system.

14. The image display device according to claim 13, wherein the dust-proof member is a plate-shaped member, and a plate surface of the dust-proof member is arranged parallel to an image display surface of the image display element.

15. The image display device according to claim 8, wherein the lens group is fixed when zooming and focusing are performed.

16. The image display device according to claim 8, wherein a lens or a mirror closest to the image display element on a light path from the light source to the image element is cut off corresponding to an external shape of the lens group.

17. An image display device comprising:

a reflection-type light valve;

a lamp light source that illuminates the light valve;

an illumination optical system that leads light emitted from the lamp light source to the light valve;

a projection optical system that projects an image displayed on the light valve and forms the image; and

a dust-proof member that is provided on a side of the projection optical system where an imaging luminous flux is emitted,

the projection optical system including;

a refractive optical system that includes a plurality of lenses;

an aperture that limits a quantity of light led to the refractive optical system from the light valve;

a lens group that is arranged between the light valve and the aperture, has a positive refractive power, and has low field curvature with respect to the light valve; and

a mirror optical system that has a concave mirror arranged on an opposite side from the light valve across the refractive optical system, the aperture, and the lens group.