Viewing optical system and image pickup optical system and apparatus using the same

A viewing optical system comprising:

• an observation image forming member for forming an observation image to be viewed by an observer;
• and
• an ocular optical member for leading the observation image formed by said observation image forming member to an exit pupil formed at a position of an observer's eyeball;
• said ocular optical member including at least a first prism member and a second prism member;
• said first prism member having at least:
• a first entrance surface through which light rays from said observation image enter said first prism member;
• a reflecting surface reflecting the light rays within said first prism member;
• and
• a first exit surface through which the light rays exit said first prism member;
• wherein said first entrance surface, said reflecting surface and said first exit surface are disposed to face each other across a first prism medium;
• said second prism member having at least:
• a second entrance surface through which the light rays exiting from said first prism member enter said second prism member;
• and
• a second exit surface through which the light rays exit said second prism member;
• wherein said second entrance surface and said second exit surface are disposed to face each other across a second prism medium;
• said first prism member and said second prism member being cemented together with a holographic element interposed between said first exit surface and said second entrance surface;
• wherein said reflecting surface of said first prism member is a concave surface that gives a positive power to the light rays when reflecting them;
• and
• wherein said first exit surface and said second entrance surface are each formed from a spherical surface or a toric surface satisfying the following conditions:
• −2.0<Da/Ra<2.0 (2)
• −0.05<Db/Rb<0.05 (3)
• where Ra and Da are a curvature radius and an outer diameter of the surface in a direction of an axis where the surface has a larger curvature, and Rb and Db are a curvature radius and an outer diameter of the surface in a direction of an axis where the surface has a smaller curvature.

An image pickup optical system comprising:

• an image pickup device placed in an image plane to pick up an image of an object;
• an aperture stop placed in a pupil plane to reduce a brightness of a light beam from the object;
• and
• an image-forming optical member disposed between said image plane and said pupil plane to lead said image of the object to said image plane;
• said image-forming optical member including at least a second prism member and a first prism member;
• said second prism member having at least:
• a third entrance surface through which light rays emanating from the object and passing through said aperture stop enter said second prism member;
• and
• a third exit surface through which the light rays exit said second prism member;
• wherein said third entrance surface and said third exit surface are disposed to face each other across a second prism medium;
• said first prism member having at least:
• a fourth entrance surface through which the light rays exiting from said second prism member enter said first prism member;
• a reflecting surface reflecting the light rays within said first prism member;
• and
• a fourth exit surface through which the light rays exit said first prism member;
• wherein said fourth entrance surface, said reflecting surface and said fourth exit surface are disposed to face each other across a first prism medium;
• said second prism member and said first prism member being cemented together with a holographic element interposed between said third exit surface and said fourth entrance surface;
• wherein said reflecting surface of said first prism member is a concave surface that gives a positive power to the light rays when reflecting them;
• and
• wherein said third exit surface and said fourth entrance surface are each formed from a plane surface or a cylindrical surface.

An image pickup optical system comprising:

• an image pickup device placed in an image plane to pick up an image of an object;
• an aperture stop placed in a pupil plane to reduce a brightness of a light beam from the object;
• and
• an image-forming optical member disposed between said image plane and said pupil plane to lead said image of the object to said image plane;
• said image-forming optical member including at least a second prism member and a first prism member;
• said second prism member having at least:
• a third entrance surface through which light rays emanating from the object and passing through said aperture stop enter said second prism member;
• and
• a third exit surface through which the light rays exit said second prism member;
• wherein said third entrance surface and said third exit surface are disposed to face each other across a second prism medium;
• said first prism member having at least:
• a fourth entrance surface through which the light rays exiting from said second prism member enter said first prism member;
• a reflecting surface reflecting the light rays within said first prism member;
• and
• a fourth exit surface through which the light rays exit said first prism member;
• wherein said fourth entrance surface, said reflecting surface and said fourth exit surface are disposed to face each other across a first prism medium;
• said second prism member and said first prism member being cemented together with a holographic element interposed between said third exit surface and said fourth entrance surface;
• wherein said reflecting surface of said first prism member is a concave surface that gives a positive power to the light rays when reflecting them;
• and
• wherein said third exit surface and said fourth entrance surface are each formed from a spherical surface or a toric surface satisfying the following conditions:
• −2.0<Da/Ra<2.0 (2)
• −0.05<Db/Rb<0.05 (3)
• where Ra and Da are a curvature radius and an outer diameter of the surface in a direction of an axis where the surface has a larger curvature, and Rb and Db are a curvature radius and an outer diameter of the surface in a direction of an axis where the surface has a smaller curvature.