Imaging optical system, optical apparatus and image projection apparatus

• US 9,606,425 B2
• Filed: 06/16/2016
• Issued: 03/28/2017
• Est. Priority Date: 06/19/2015
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ode, Takashi, Inoko, Kazuhiro
• Primary Examiner(s): Tran, Trang U
• Application Number:
  US15/184,370
• Publication Number:
  US 20160370692A1
• Time in Patent Office: 285 Days
• Field of Search: 348/759, 34824099-2403, 348335-369, 359/676, 359/689, 359/678, 359/882, 359/686
• US Class Current: 1/1
• CPC Class Codes: G02B 17/0852 having a field corrector only
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G03B 21/147 Optical correction of image distortions, e.g. keystone
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

An imaging optical system, which images an image on one conjugate surface of an enlargement side conjugate surface and a reduction side conjugate surface onto the other conjugate surface, includes, in order from the reduction side conjugate surface to the enlargement side conjugate surface, a refractive optical system and a reflective optical system. The refractive optical system forms an intermediate real image at an intermediate imaging position inside the refractive optical system. The reflective optical system includes a convex mirror disposed closest to the enlargement side conjugate surface. The predetermined conditional expression is satisfied.

Claims

1. An imaging optical system that images an image on one conjugate surface of an enlargement side conjugate surface and a reduction side conjugate surface onto the other conjugate surface, the imaging optical system comprising:

in order from the reduction side conjugate surface to the enlargement side conjugate surface,

a refractive optical system; and

a reflective optical system,

wherein the refractive optical system forms an intermediate real image at an intermediate imaging position inside the refractive optical system,

wherein the reflective optical system includes a convex mirror disposed closest to the enlargement side conjugate surface, and

wherein the following conditional expression is satisfied;

0.01≦

|fL/fM|≦

0.50

where fL is a focal length of the refractive optical system, and fM is a focal length of the reflective optical system.

2. The imaging optical system according to claim 1, wherein the reflective optical system is configured by the convex mirror.

3. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied:

−

2.0≦

β

≦

−

0.5

where β

is a lateral magnification between an image on the reduction side conjugate surface and the intermediate real image, and the lateral magnification β

is less than −

1 when the intermediate real image is larger than the image on the reduction side conjugate surface.

4. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied:

0.3≦

|f11/f12|≦

0.8

where, of the refractive optical system, f11 is a focal length of a first partial refractive optical system disposed between the reflective optical system and the intermediate imaging position, and f12 is a focal length of a second partial refractive optical system disposed between the intermediate imaging position and the reduction side conjugate surface.

5. The imaging optical system according to claim 1, wherein, when a lens disposed on the most reflective optical system side of the refractive optical system is a first lens, the first lens has an aspherical shape.

6. The imaging optical system according to claim 5, wherein the following conditional expression is satisfied:

0.2≦

Φ

G1/Φ

Gmax≦

2.0

where Φ

G1 is an effective diameter of the first lens, and Φ

Gmax is an effective diameter of a lens having the largest effective diameter in lenses other than the first lens of the refractive optical system.

7. The imaging optical system according to claim 5, wherein the following conditional expression is satisfied:

0.01≦

D/TL≦

0.30

where D is a distance between the reflective optical system and the first lens, and TL is a total length of the imaging optical system.

8. The imaging optical system according to claim 5, wherein two lights respectively having a maximum reflection angle and a minimum reflection angle in the reflective optical system do not cross each other between the first lens and the reflective optical system.

9. An optical apparatus comprising:

an imaging optical system that images an image on one conjugate surface of an enlargement side conjugate surface and a reduction side conjugate surface onto the other conjugate surface,

wherein the imaging optical system includes, in order from the reduction side conjugate surface to the enlargement side conjugate surface, a refractive optical system and a reflective optical system,

wherein the refractive optical system forms an intermediate real image at an intermediate imaging position inside the refractive optical system,

wherein the reflective optical system includes a convex mirror disposed closest to the enlargement side conjugate surface, and

wherein the following conditional expression is satisfied;

0.01≦

|fL/fM|≦

0.50

where fL is a focal length of the refractive optical system, and fM is a focal length of the reflective optical system.

10. An image projection apparatus comprising:

a light modulation element that modulates light; and

an imaging optical system that projects light from the light modulation element onto a projection surface,

wherein the imaging optical system images an image on one conjugate surface of an enlargement side conjugate surface and a reduction side conjugate surface onto the other conjugate surface,

wherein the imaging optical system includes, in order from the reduction side conjugate surface to the enlargement side conjugate surface, a refractive optical system and a reflective optical system,

wherein the refractive optical system forms an intermediate real image at an intermediate imaging position inside the refractive optical system,

wherein the reflective optical system includes a convex mirror disposed closest to the enlargement side conjugate surface, and

wherein the following conditional expression is satisfied;

0.01≦

|fL/fM|≦

0.50

where fL is a focal length of the refractive optical system, and fM is a focal length of the reflective optical system.

11. The image projection apparatus according to claim 10, further comprising an image pickup apparatus including an image pickup element and an image pickup optical system that forms an image of the projection surface on the image pickup element.