Image-taking optical system and image input apparatus

• US 7,133,217 B2
• Filed: 09/04/2002
• Issued: 11/07/2006
• Est. Priority Date: 09/04/2001
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Chatani, Sawako, Sunaga, Toshihiro
• Primary Examiner(s): Spector, David N.
• Application Number:
  US10/235,520
• Publication Number:
  US 20030090794A1
• Time in Patent Office: 1,525 Days
• Field of Search: 353/99, 359/727, 359/729, 359/730, 359/731, 359/806, 359/807
• US Class Current: 359/730
• CPC Class Codes: G02B 17/0663 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: G03B 21/56 Projection screens

Abstract

An image-taking optical system according to the present invention for forming an image of a two-dimensional object on an image-taking surface comprises a plurality of reflecting surfaces which reflect light from the two-dimensional object sequentially and guides the light to the image-taking surface, and a reference axis passing through the center of the pupil of the image-taking system and the center of the optical image formed on the image-taking surface is inclined with respect to the normal line of the two-dimensional object.

The present invention provides an image-taking optical system which achieves a reduction in size, ensures a ratio of an amount of peripheral light, allows correction of trapezoidal distortion of a formed image, and is suitable for oblique image-taking.

Claims

1. An image-taking optical system for forming an image of a two-dimensional object on an image-taking surface, comprising:

a plurality of reflecting surfaces which reflect light from said two-dimensional object sequentially and guide the light to said image-taking surface,

wherein a reference axis passing through the center of the pupil of said image-taking optical system and the center of the image formed on said image-taking surface is inclined with respect to the normal line of said two-dimensional object.

2. The image-taking optical system according to claim 1,

wherein said reflecting surfaces include at least one curved reflecting surface.

3. The image-taking optical system according to claim 2,

wherein said curved reflecting surface is a rotationally asymmetric surface.

4. The image-taking optical system according to claim 2,

wherein said reflecting surfaces include at least two of said curved reflecting surfaces, and the image-taking optical system further comprising an aperture stop which is disposed between said two curved reflecting surfaces.

5. The image-taking optical system according to claim 2, further comprising an aperture stop which is disposed on said curved reflecting surface.

6. The image-taking optical system according to claim 2, further comprising an aperture stop which is disposed between said curved reflecting surface and said image-taking surface.

7. The image-taking optical system according to claim 1,

wherein the relative distance between optical surfaces of said image-taking optical system is variable for focusing.

8. The image-taking optical system according to claim 1,

wherein the relative distance between an optical surface of said image-taking optical system and said image-taking surface is variable for focusing.

9. The image-taking optical system according to claim 1,

wherein the following condition is satisfied:

|1−

cos θ

·

β

(α

)/β

(α

+90°

)|<

0.2

where θ

is an angle of inclination of said reference axis with respect to said normal line of said two-dimensional object, α

is an azimuth representing a plane including said reference axis and said normal line of said two-dimensional object, and β

(ξ

) is a magnification of said image-taking optical system at an azimuth ξ

°

around said reference axis.

10. The image-taking optical system according to claim 1,

wherein each reflecting surface of said plurality of reflecting surfaces other than a reflecting surface by which light from said two-dimensional object is first reflected consists of a surface reflecting mirror.

11. The image-taking optical system according to claim 1,

wherein each reflecting surface of said plurality of reflecting surfaces other than a reflecting surface by which light from said two-dimensional object is first reflected consists of an internal reflecting surface in an optical element in a prism shape having two refraction surfaces which the light enter and exit.

12. An image input apparatus comprising:

the image-taking optical system according to claim 1, and

a photoelectric converting element which is disposed on said image-taking surface and photoelectrically converts the image of said two-dimensional object formed by said image-taking optical system.

13. The image input apparatus according to claim 12,

wherein a first reflecting surface of said plurality of reflecting surfaces by which light from said two-dimensional object is first reflected can be moved to a position at which said first reflecting surface guides the light from said two-dimensional object to said image-taking optical system subsequent to said first reflecting surface and to a position at which said first reflecting surface is retracted with respect to said image-taking optical system subsequent to said first reflecting surface.