Image-forming optical system

• US 6,671,099 B2
• Filed: 12/26/2001
• Issued: 12/30/2003
• Est. Priority Date: 12/25/2000
• Status: Active Grant

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Nagata, Tetsuo
• Primary Examiner(s): Mack, Ricky
• Assistant Examiner(s): Thomas, Brandi N
• Application Number:
  US10/025,896
• Publication Number:
  US 20020159158A1
• Time in Patent Office: 734 Days
• Field of Search: 359/625, 359/627, 359/629, 359/630, 359/631, 359/637, 359/638, 359/640, 359/720, 359/831, 359/833, 359/834
• US Class Current: 359/629
• CPC Class Codes: G02B 13/0015 characterised by the lens design
• CPC Class Codes: G02B 13/005 having spherical lenses only
• 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 13/007 the beam folding prism having at least one curved surface
• CPC Class Codes: G02B 17/0832 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 17/086 wherein the system is made of a single block of optical material, e.g. solid catadioptric systems

Abstract

A high-performance and low-cost image-forming optical system has a reduced number of constituent optical elements and is made extremely thin, particularly in a direction perpendicular to an image pickup device, by folding an optical path using only three reflecting surfaces. The image-forming optical system has a front unit including a first prism 10, an aperture stop 2, and a rear unit including a second prism 20. The first prism 10 has a first transmitting surface 11, a first reflecting surface 12, and a second transmitting surface 13. The second prism 20 has a first transmitting surface 21, a first reflecting surface 22, a second reflecting surface 23, and a second transmitting surface 24. An optical path incident on the first reflecting surface 22 and an optical path exiting from the second reflecting surface 23 intersect each other. The first reflecting surface 12 of the first prism 10 and the first and second reflecting surfaces 22 and 23 of the second prism 20 have a curved surface configuration that gives a power to a light beam. The curved surface configuration is a rotationally asymmetric surface configuration that corrects aberrations due to decentration.

Claims

1. An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising, in order from an object side thereof:

a front unit including at least a first prism;

an aperture stop; and

a rear unit including a second prism;

wherein said first prism and said second prism are each formed from a medium having a refractive index (n) larger than 1.3 (n>

1.3), and wherein no intermediate image is formed;

said first prism having three optical functional surfaces transmitting or reflecting a light beam;

wherein when said three optical functional surfaces are defined as a first-first surface, a first-second surface, and a first-third surface, respectively, said first-first surface allows a light-beam from an object side thereof to enter said first prism through it, said first-second surface reflects the light beam entering through said first-first surface within said first prism, and said first-third surface allows the light beam reflected from said first-second surface to exit said first prism through it;

said second prism having four optical functional surfaces transmitting or reflecting a light beam;

wherein when said four optical functional surfaces are defined as a second-first surface, a second-second surface, a second-third surface, and a second-fourth surface, respectively, said second-first surface allows a light beam from an object side thereof to enter said second prism through it, said second-second surface reflects the light beam entering through said second-first surface within said second prism, said second-third surface reflects the light beam reflected from said second-second surface within said second prism, and said second-fourth surface allows the light beam reflected from said second-third surface to exit said second prism through it, and wherein said second-first surface and said second-second surface are disposed to face each other across said medium, and said second-third surface and said second-fourth surface are disposed to face each other across said medium, and further an optical path connecting said second-first surface and said second-second surface intersects an optical path connecting said second-third surface and said second-fourth surface;

wherein said first-second surface of said first prism has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration; and

wherein said second-second surface and said second-third surface of said second prism have a curved surface configuration that gives a power to a light beam, said curved surface configuration being a rotationally asymmetric surface configuration that corrects aberrations due to decentration.

2. An image-forming optical system according to claim 1, wherein three reflecting surfaces of said first prism and said second prism are plane-symmetry free-form surfaces each having only one plane of symmetry.

5. An image-forming optical system according to claim 1, wherein the following condition is satisfied:

9. An image-forming optical system according to claim 1,

wherein at least one optical element is placed on an object side of said first prism.

10. An image-forming optical system according to claim 1, wherein at least one optical element is placed between said first prism and said second prism.

11. An image-forming optical system according to claim 1, wherein at least one surface of said optical element has a rotationally asymmetric surface configuration that corrects aberrations due to decentration.

12. An image-forming optical system according to claim 1, wherein said ear unit consists of said second prism.

13. An image-forming optical system according to claim 1 or 2, wherein the first prism in said front unit comprises a single mirror.

14. An image-forming optical system according to claim 1 or 2, wherein the second prism in said rear unit comprises two mirrors.

15. An image-forming optical system according to claim 1 or 2, wherein the first prism in said front unit comprises a single mirror, and the second prism in said rear unit comprises two mirrors.

16. A finder optical system comprising:

said image-forming optical system according to any one of claims 1, 3, 4, 6, 7 or 8, said image-forming optical system being provided as a finder objective optical system;

an image-erecting optical system for erecting an object image formed by said finder objective optical system; and

an ocular optical system.

17. An electronic camera apparatus comprising:

said image-forming optical system according to any one of claims 1, 3, 4, 6, 7 or 8;

an image pickup device placed in an image plane formed by said image-forming optical system;

a recording medium for recording image information received by said image pickup device; and

an image display device that receives image information from one of said recording medium and said image pickup device to form an image for observation.

18. An endoscope system comprising:

an observation system having said image-forming optical system according to any one of claims 1, 3, 4, 6, 7 or 8 and an image transmitting member for transmitting an image formed by said image-forming optical system along a longitudinal axis; and

an illumination system having an illuminating light source and an illuminating light transmitting member for transmitting illuminating light from said illuminating light source along said longitudinal axis.

19. A projector comprising:

a light source;

a display device; and

a projection optical system for projecting information displayed on said display device;

wherein said projection optical system has said image-forming optical system according to any one of claims 1, 3, 4, 6, 7 or 8.

20. A portable information terminal comprising:

an input unit for inputting information;

a display unit for displaying the information; and

an image pickup optical system for imaging an object;

wherein said image pickup optical system has said image-forming optical system according to any one of claims 1, 3, 4, 6, 7 or 8.

21. A portable telephone comprising:

an input unit for inputting information;

a display unit for displaying the information;

a voice input unit;

a voice output unit;

an antenna; and

an image pickup optical system for imaging an object;

wherein said image pickup optical system has said image-forming optical system according to any one of claims 1, 3, 4, 6, 7 or 8.

3. An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising, in order from an object side thereof:

a front unit including at least a first prism;

an aperture stop; and

a rear unit including a second prism;

wherein said first prism and said second prism are each formed from a medium having a refractive index (n) larger than 1.3 (n>

1.3), and wherein no intermediate image is formed;

said first prism having three optical functional surfaces transmitting or reflecting a light beam;

wherein when said three optical functional surfaces are defined as a first-first surface, a first-second surface, and a first-third surface, respectively, said first-first surface allows a light beam from an object side thereof to enter said first prism through it, said first-second surface reflects the light beam entering through said first-first surface within said first prism, and said first-third surface allows the light beam reflected from said first-second surface to exit said first prism through it;

said second prism having four optical functional surfaces transmitting or reflecting a light beam;

wherein when said four optical functional surfaces are defined as a second-first surface, a second-second surface, a second-third surface, and a second-fourth surface, respectively, said second-first surface allows a light beam from an object side thereof to enter said second prism through it, said second-second surface reflects the light beam entering through said second-first surface within said second prism, said second-third surface reflects the light beam reflected from said second-second surface within said second prism, and said second-fourth surface allows the light beam reflected from said second-third surface to exit said second prism through it, and wherein said second-first surface and said second-second surface are disposed to face each other across said medium, and said second-third surface and said second-fourth surface are disposed to face each other across said medium, and further an optical path connecting said second-first surface and said second-second surface intersects an optical path connecting said second-third surface and said second-fourth surface;

wherein said first-second surface of said first prism has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration; and

wherein said second-second surface and said second-third surface of said second prism have a curved surface configuration that gives a power to a light beam, said curved surface configuration being a rotationally asymmetric surface configuration that corrects aberrations due to decentration,

wherein when a decentration direction of said image-forming optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, the following condition are satisfied;

4. An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising, in order from an object side thereof:

a front unit including at least a first prism;

an aperture stop; and

a rear unit including a second prism;

wherein said first prism and said second prism are each formed from a medium having a refractive index (n) larger than 1.3 (n>

1.3), and wherein no intermediate image is formed;

said first prism having three optical functional surfaces transmitting or reflecting a light beam;

wherein when said three optical functional surfaces are defined as a first-first surface, a first-second surface, and a first-third surface, respectively, said first-first surface allows a light beam from an object side thereof to enter said first prism through it, said first-second surface reflects the light beam entering through said first-first surface within said first prism, and said first-third surface allows the light beam reflected from said first-second surface to exit said first prism through it;

said second prism having four optical functional surfaces transmitting or reflecting a light beam;

wherein when said four optical functional surfaces are defined as a second-first surface, a second-second surface, a second-third surface, and a second-fourth surface, respectively, said second-first surface allows a light beam from an object side thereof to enter said second prism through it, said second-second surface reflects the light beam entering through said second-first surface within said second prism, said second-third surface reflects the light beam reflected from said second-second surface within said second prism, and said second-fourth surface allows the light beam reflected from said second-third surface to exit said second prism through it, and wherein said second-first surface and said second-second surface are disposed to face each other across said medium, and said second-third surface and said second-fourth surface are disposed to face each other across said medium, and further an optical path connecting said second-first surface and said second-second surface intersects an optical path connecting said second-third surface and said second-fourth surface;

wherein said first-second surface of said first prism has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration; and

wherein said second-second surface and said second-third surface of said second prism have a curved surface configuration that gives a power to a light beam, said curved surface configuration being a rotationally asymmetric surface configuration that corrects aberrations due to decentration,

wherein when a decentration direction of said image-forming optical system is a Y-axis direction, and a plane parallel to an axial principal ray is a YZ-plane, and further a direction perpendicularly intersecting the YZ-plane is an X-axis direction, the following conditions are satisfied;

6. An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising, in order from an object side thereof:

a front unit including at least a first prism;

an aperture stop; and

a rear unit including a second prism;

wherein said first prism and said second prism are each formed from a medium having a refractive index (n) larger than 1.3 (n>

1.3), and wherein no intermediate image is formed;

said first prism having three optical functional surfaces transmitting or reflecting a light beam;

wherein when said three optical functional surfaces are defined as a first-first surface, a first-second surface, and a first-third surface, respectively, said first-first surface allows a light beam from an object side thereof to enter said first prism through it, said first-second surface reflects the light beam entering through said first-first surface within said first prism, and said first-third surface allows the light beam reflected from said first-second surface to exit said first prism through it;

aid second prism having four optical functional surfaces transmitting or reflecting a light beam;

wherein when said four optical functional surfaces are defined as a second-first surface, a second-second surface, a second-third surface, and a second-fourth surface, respectively, said second-first surface allows a light beam from an object side thereof to enter said second prism through it, said second-second surface reflects the light beam entering through said second-first surface within said second prism, said second-third surface reflects the light beam reflected from said second-second surface within said second prism, and said second-fourth surface allows the light beam reflected from said second-third surface to exit said second prism through it, and wherein said second-first surface and said second-second surface are disposed to face each other across said medium, and said second-third surface and said second-fourth surface are disposed to face each other across said medium, and further an optical path connecting said second-first surface and said second-second surface intersects an optical path connecting said second-third surface and said second-fourth surface;

wherein said first-second surface of said first prism has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration; and

wherein said second-second surface and said second-third surface of said second prism have a curved surface configuration that gives a power to a light beam, said curved surface configuration being a rotationally asymmetric surface configuration that corrects aberrations due to decentration,

wherein the following condition is satisfied;

7. An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising, in order from an object side thereof:

a front unit including at least a first prism;

an aperture stop; and

a rear unit including a second prism;

wherein said first prism and said second prism are each formed from a medium having a refractive index (n) larger than 1.3 (n>

1.3), and wherein no intermediate image is formed;

said first prism having three optical functional surfaces transmitting or reflecting a light beam;

wherein when said three optical functional surfaces are defined as a first-first surface, a first-second surface, and a first-third surface, respectively, said first-first surface allows a light beam from an object side thereof to enter said first prism through it, said first-second surface reflects the light beam entering through said first-first surface within said first prism, and said first-third surface allows the light beam reflected from said first-second surface to exit said first prism through it;

said second prism having four optical functional surfaces transmitting or reflecting a light beam;

wherein when said four optical functional surfaces are defined as a second-first surface, a second-second surface, a second-third surface, and a second-fourth surface, respectively, said second-first surface allows a light beam from an object side thereof to enter said second prism through it, said second-second surface reflects the light beam entering through said second-first surface within said second prism, said second-third surface reflects the light beam reflected from said second-second surface within said second prism, and said second-fourth surface allows the light beam reflected from said second-third surface to exit said second prism through it, and wherein said second-first surface and said second-second surface are disposed to face each other across said medium, and said second-third surface and said second-fourth surface are disposed to face each other across said medium, and further an optical path connecting said second-first surface and said second-second surface intersects an optical path connecting said second-third surface and said second-fourth surface;

wherein said first-second surface of said first prism has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration; and

wherein said second-second surface and said second-third surface of said second prism have a curved surface configuration that gives a power to a light beam, said curved surface configuration being a rotationally asymmetric surface configuration that corrects aberrations due to decentration,

wherein the following condition is satisfied;

8. An image-forming optical system having a positive refracting power as a whole for forming an object image, said image-forming optical system comprising, in order from an object side thereof:

a front unit including at least a first prism;

an aperture stop; and

a rear unit including a second prism;

wherein said first prism and said second prism are each formed from a medium having a refractive index (n) larger than 1.3 (n>

1.3), and wherein no intermediate image is formed;

said first prism having three optical functional surfaces transmitting or reflecting a light beam;

wherein when said three optical functional surfaces are defined as a first-first surface, a first-second surface, and a first-third surface, respectively, said first-first surface allows a light beam from an object side thereof to enter said first prism through it, said first-second surface reflects the light beam entering through said first-first surface within said first prism, and said first-third surface allows the light beam reflected from said first-second surface to exit said first prism through it;

said second prism having four optical functional surfaces transmitting or reflecting a light beam;

wherein when said four optical functional surfaces are defined as a second-first surface, a second-second surface, a second-third surface, and a second-fourth surface, respectively, said second-first surface allows a light beam from an object side thereof to enter said second prism through it, said second-second surface reflects the light beam entering through said second-first surface within said second prism, said second-third surface reflects the light beam reflected from said second-second surface within said second prism, and said second-fourth surface allows the light beam reflected from said second-third surface to exit said second prism through it, and wherein said second-first surface and said second-second surface are disposed to face each other across said medium, and said second-third surface and said second-fourth surface are disposed to face each other across said medium, and further an optical path connecting said second-first surface and said second-second surface intersects an optical path connecting said second-third surface and said second-fourth surface;

wherein said first-second surface of said first prism has a rotationally asymmetric surface configuration that gives a power to a light beam and corrects aberrations due to decentration; and

wherein said second-second surface and said second-third surface of said second prism have a curved surface configuration that gives a power to a light beam, said curved surface configuration being a rotationally asymmetric surface configuration that corrects aberrations due to decentration,

wherein either of the following conditions is satisfied;

 

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