Finder optical system and image pickup apparatus using the same

• US 6,643,062 B1
• Filed: 09/07/2000
• Issued: 11/04/2003
• Est. Priority Date: 09/07/1999
• Status: Expired due to Term

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Kamo, Yuji
• Primary Examiner(s): NGUYEN, THONG Q
• Application Number:
  US09/657,517
• Time in Patent Office: 1,153 Days
• Field of Search: 359/362, 359/399, 359/405-410, 359/422-432, 359/676-677, 359/690-691, 359/831-837, 359/708, 359/629-634, 396/373-386
• US Class Current: 359/431
• CPC Class Codes: G02B 13/22 Telecentric objectives or lens systems
• CPC Class Codes: G02B 17/045 having static image erecting or reversing properties only optical derotators G02B27/642; optical devices for controlling the direction of light using movable or deformable optical elements G02B26/08
• CPC Class Codes: G02B 17/0816 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 17/0832 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
• CPC Class Codes: G02B 23/14 Viewfinders for photographic apparatus G03B13/02
• CPC Class Codes: G02B 23/145 Zoom viewfinders

Abstract

A high-performance real-image finder optical system reduced in size, particularly in thickness, includes a positive objective optical system, an image-inverting optical system for erecting an intermediate image formed by the objective optical system, and a positive ocular optical system. The objective optical system has at least two movable units moving when zooming is performed. A prism is placed on the object side of the intermediate image. At least one reflecting surface of the prism has a rotationally asymmetric surface configuration. At least one reflecting surface of the image-inverting optical system is formed from a roof surface. The finder optical system satisfies the following condition:

1.0<d/(f_W·tan θ_W·Z)<2.5

where d is the distance from the entrance surface of the objective optical system to the first reflecting surface of the image-inverting optical system; f_W is the focal length of the objective optical system at the wide-angle end; θ_W is the maximum field angle of the objective optical system at the wide-angle end; and Z is a zoom ratio.

Claims

1. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system has;

at least two movable units moving when zooming is performed; and

a prism placed on an object side of the intermediate image formed by said objective optical system, said prism including at least one reflecting surface having a rotationally asymmetric surface configuration;

said image-inverting optical system having at least one reflecting surface formed from a roof surface;

said finder optical system satisfying the following condition;

2. A finder optical system according to claim 1, wherein said roof surface is placed on a pupil side of said intermediate image.

3. A finder optical system according to claim 1, wherein a number of reflection in said prism is three.

4. A finder optical system according to claim 1, wherein the number of said movable units is two.

7. A finder optical system according to claim 1, 5 or 6, wherein said prism is placed closer to a pupil than any of said movable units.

8. An image pickup apparatus comprising:

a photographic optical system having an optical path for photography;

an

a finder optical system having an optical path for a finder;

wherein said finder optical system according to claim 1, 5, or 6, is used as said finder optical system.

9. A finder optical system according to claim 1, wherein a number of reflections in said prism is two.

5. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system includes;

an optical system having at least two movable units moving when zooming is performed, said optical system having a positive composite power; and

a prism placed on a pupil side of said optical system, said prism including an image-inverting function, and said prism including at least one reflecting surface having a rotationally asymmetric surface configuration;

wherein;

at least either one of a first transmitting surface and first reflecting surface of said prism has a negative power, and a second transmitting surface of said prism has a positive power, and

a composite focal length of said at least two movable units satisfies the following condition;

10. A finder optical system according to claim 5, wherein a number of reflections in said prism is three.

11. A finder optical system according to claim 5, wherein a number of reflections in said prism is two.

6. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system has;

at least two movable units moving when zooming is performed; and

a prism placed on an object side of the intermediate image formed by said objective optical system, said prism having three reflecting surfaces, wherein at least one of said reflecting surfaces has a rotationally asymmetric surface configuration, and

wherein a composite focal length of said at least two movable units satisfies the following condition;

12. A finder optical system according to claim 6 wherein at least two of the reflecting surfaces of said prism are formed from independent surfaces, respectively, which are separate from other transmitting and reflecting surfaces.

13. A finder optical system according to claim 6, wherein a first reflecting surface of said prism has a rotationally asymmetric surface configuration and is formed from an independent surface that is separate from other transmitting and reflecting surfaces.

14. A finder optical system according to claim 6, wherein a third reflecting surface of said prism has a rotationally asymmetric surface configuration and is formed from an independent surface that is separate from other transmitting and reflecting surfaces.

15. A finder optical system according to claim 6, wherein a second transmitting surface of said prism has a power.

16. A finder optical system according to claim 15, wherein the second transmitting surface has a rotationally asymmetric surface configuration.

17. A finder optical system according to claim 6, wherein an axial principal ray or a projective axial principal ray defined by projecting the axial principal ray onto a plane containing a part of the axial principal ray does not cross itself in said prism.

18. A finder optical system according to claim 6, wherein either one of a first transmitting surface and first reflecting surface of said prism has a negative power.

19. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system includes, in order from an object side thereof;

a negative first unit;

a positive second unit; and

a negative third unit;

wherein at least the first unit and the second unit are movable units moving when zooming is performed, and the third unit is formed from a prism including an image-inverting function, said prism including an entrance surface having a negative refracting power and at least one reflecting surface having a rotationally asymmetric surface configuration with a negative power.

21. A finder optical system according to claim 19 or 20, wherein a second transmitting surface of said prism has a power.

22. A finder optical system according to claim 21, wherein said second transmitting surface has a rotationally asymmetric surface configuration.

23. A finder optical system according to claim 19 or 20, wherein a number of reflections in said prism is three.

24. A finder optical system according to claim 19 or 20, wherein when zooming is performed, said third unit is stationary with respect to a plane where the intermediate image is formed.

25. A finder optical system according to claim 19 or 20, wherein both said movable units are formed from refracting lenses.

26. A finder optical system according to claim 19 or 20, wherein said movable units are each formed from a single refracting lens.

20. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system includes, in order from an object side thereof;

a negative first unit;

a positive second unit; and

a positive third unit;

wherein at least the first unit and the second unit are movable units moving when zooming is performed, and the third unit is formed from a prism including an image-inverting function, said prism including at least one reflecting surface having a rotationally asymmetric surface configuration, and said prism including at least one transmitting surface or reflecting surface that has a negative power, said third unit having a principal point positioned on a pupil side of a plane where the intermediate image is formed, and

wherein a composite focal length of said movable units satisfies the following condition;

27. A finder optical system according to claims or 19 or 20, wherein a number of reflections in said prism is two.

28. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system includes;

an optical system having at least two movable units moving when zooming is performed, said optical system having a positive composite power; and

a prism placed on a pupil side of said optical system, said prism including an image-inverting function, and said prism including at least one reflecting surface having a rotationally asymmetric surface configuration;

wherein at least either one of a first transmitting surface and first reflecting surface of said prism has a negative power, and a second transmitting surface of said prism has a positive power, and

wherein said finder optical system satisfies the following condition;

29. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system has;

at least two movable units moving when zooming is performed; and

a prism placed on an object side of the intermediate image formed by said objective optical system, said prism having three reflecting surfaces, wherein at least one of said reflecting surfaces has a rotationally asymmetric surface configuration, and

wherein said finder optical system satisfies the following condition;

30. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system includes, in order from an object side thereof;

a negative first unit;

a positive second unit; and

a negative third unit;

wherein at least the first unit and the second unit are movable units moving when zooming is performed, and the third unit is formed from a prism including an image-inverting function, said prism including at least one reflecting surface having a rotationally asymmetric surface configuration, and

wherein said finder optical system satisfies the following condition;

31. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system includes, in order from an object side thereof;

a negative first unit;

a positive second unit; and

a positive third unit;

wherein at least the first unit and the second unit are movable units moving when zooming is performed, and the third unit is formed from a prism including an image-inverting function, said prism including at least one reflecting surface having a rotationally asymmetric surface configuration, and said prism including at least one transmitting surface or reflecting surface that has a negative power, said third unit having a principal point positioned on a pupil side of a plane where the intermediate image is formed, and

wherein said finder optical system satisfies the following condition;

32. A finder optical system comprising, in order from an object side thereof;

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power,

wherein said objective optical system has;

at least two movable units moving when zooming is performed; and

a prism placed on an object side of the intermediate image formed by said objective optical system, said prism including at least one reflecting surface having a rotationally asymmetric surface configuration;

said image-inverting optical system including a Porro prism;

said finder optical system satisfying the following conditions;

33. A finder optical system according to claim 32, wherein a second transmitting surface of said prism of said objective optical system has a power.

34. A finder optical system according to claim 33, wherein said second transmitting surface of said prism has a rotationally asymmetric surface configuration.

35. A finder optical system according to claim 32, wherein a first reflecting surface of said objective optical system has a power.

36. A finder optical system according to claim 32, wherein a number of reflections in said prism is two or three.

37. A finder optical system according to claim 32, wherein the number of said movable units is two.

38. A finder optical system according to claim 32, wherein said prism is placed closer to a pupil than any of said movable units.

39. An image pickup apparatus comprising:

a photographic optical system having an optical path for photography; and

a finder optical system having an optical path for a finder,

wherein said finder optical system according to claim 32, is used as said finder optical system.

40. A finder optical system according to claim 32, wherein a number of reflections in said prism is two.

41. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power;

wherein said objective optical system has;

at least two movable units moving when zooming is performed; and

a prism placed on an object side of the intermediate image formed by said objective optical system, said prism having two reflecting surfaces, wherein at least one of said reflecting surfaces has a rotationally asymmetric surface configuration, and said prism constituting a part of said objective optical system and a part of said image-inverting optical system;

said finder optical system satisfying the following condition;

43. A finder optical system according to claim 41, wherein a first reflecting surface of said prism has a rotationally asymmetric surface configuration and is formed from an independent surface that is separate from other transmitting and reflecting surfaces.

44. A finder optical system according to claim 41, wherein a second transmitting surface of said prism has a power.

45. A finder optical system according to claim 41, wherein the second transmitting surface has a rotationally asymmetric surface configuration.

46. A finder optical system according to claim 41, wherein an axial principal ray or a projective axial principal ray defined by projecting the axial principal ray onto a plane containing a part of the axial principal ray does not cross itself in said prism.

47. A finder optical system according to claim 41, wherein either one of a first transmitting surface and first reflecting surface of said prism has a negative power.

48. A finder optical system according to claim 41, wherein a composite focal length of said at least two movable units satisfies the following condition:

49. A finder optical system according to claim 41 or 42, wherein said prism is placed closer to a pupil than any of said movable units.

50. An image pickup apparatus comprising:

a photographic optical system having an optical path for photography; and

a finder optical system having an optical path for a finder;

wherein said finder optical system according to claim 41 or 42, is used as said finder optical system.

42. A finder optical system comprising, in order from an object side thereof:

an objective optical system having a positive refracting power;

an image-inverting optical system for erecting an intermediate image formed by said objective optical system; and

an ocular optical system having a positive refracting power,

wherein said objective optical system has;

at least two movable units moving when zooming is performed; and

a prism placed on an object side of the intermediate image formed by said objective optical system, said prism including two reflecting surfaces, both of said reflecting surfaces being independent of other transmitting and reflecting surfaces, at least one of said reflecting surfaces having a rotationally asymmetric surface configuration, said prism having an optical path in which an axial principal ray or a projective axial principal ray defined by projecting the axial principal ray onto a plane containing a part of the axial principal ray bends in a same direction with respect to a travel direction of light rays at said two reflecting surfaces, and said prism constituting a part of said objective optical system and a part of said image-inverting optical system;

said finder optical system satisfying the following condition;

51. A finder optical system according to claim 42, wherein a first transmitting surface of said prism has a negative power.

52. A finder optical system according to claim 42, wherein a second transmitting surface of said prism has a positive power.

53. A finder optical system according to claim 42, wherein a reflection angle at a first reflecting surface of said prism satisfies the following condition:

54. A finder optical system according to claim 42, wherein a reflection angle at a second reflecting surface of said prism satisfies the following condition:

55. A finder optical system according to claim 42, wherein an exit angle of said prism with respect to an optical axis entering said objective optical system satisfies the following condition:

56. A finder optical system according to claim 42, wherein a roof surface is disposed on a pupil side of the intermediate image.

57. A finder optical system according to claim 42, wherein said image-inverting optical system is a Porro prism.