Imaging optical system having bending optical element

Patent metadata

Field	Value
Publication number	US-9465199-B2
Application number	US-201414501816-A
Country	US
Kind code	B2
Filing date	Sep 30, 2014
Priority date	Oct 15, 2013
Publication date	Oct 11, 2016
Grant date	Oct 11, 2016

Abstract

An imaging optical system includes a bending optical element which bends an object-emanating light bundle, a post-bending lens system on a post-bending optical axis defined by the bending optical element, and an image sensor. An effective optical surface of a large-diameter lens element, having a greatest axial light bundle effective radius, is formed into a non-circular shape by making a length of the effective optical surface from the post-bending optical axis toward a side opposite from the object side smaller than the axial light bundle effective radius, with reference to the axial light bundle effective radius lying on a plane which extends orthogonal to a plane including both the post-bending optical axis and a pre-bending optical axis of the imaging optical system and includes the post-bending optical axis.

First claim

What is claimed is:

1. An imaging optical system, comprising:
a bending optical element which bends a light bundle emanating from an object;
a post-bending lens system arranged on a post-bending optical axis defined by an optical axis of said imaging optical system being bent by said bending optical element; and
an image sensor, on which an image of said object is formed via said post-bending lens system;
wherein an effective optical surface of a large-diameter lens element, having an axial light bundle effective radius that is greatest among those of all lens elements of said post-bending lens system, is configured into a non-circular shape by a length of said effective optical surface from said post-bending optical axis toward a side opposite from the object side being smaller than said axial light bundle effective radius, with reference to said axial light bundle effective radius lying on a plane which includes said post-bending optical axis and extends orthogonal to a plane including both said post-bending optical axis and a pre-bending optical axis of said imaging optical system,
wherein said non-circular shape of said effective optical surface satisfies the following conditions:
RU>RL,
( RU+RL )<2 RH , and
0.5<{( RU+RL )/2 RH }<0.09,

wherein when viewed in a direction along said post-bending optical axis, where an upper direction designates a direction parallel to a pre-bending optical axis and travelling toward the object side, a lower direction designates a direction opposite to said upper direction, and a horizontal direction designates a direction that is orthogonal to a plane on which both said pre-bending optical axis and said post-bending optical axis lie,
wherein RU designates a distance between said post-bending optical axis and an outermost point of said effective optical surface of said large-diameter lens element in said upper direction within the axial light bundle effective radius,
wherein RL designates a distance between said post-bending optical axis and an outermost point of said effective optical surface of said large-diameter lens element in said lower direction within said axial light bundle effective radius, and
wherein RH designates a distance between said post-bending optical axis and an outermost point of said effective optical surface of said large-diameter lens element in said horizontal direction within said axial light bundle effective radius.

2. The imaging optical system according to claim 1 , wherein said axial light bundle effective radius that is greatest among those of all lens elements of said post-bending lens system is determined with reference to said axial light bundle effective radius lying on a plane which includes said post-bending optical axis and extends orthogonal to a plane including both said post-bending optical axis and a pre-bending optical axis of said imaging optical system.

3. The imaging optical system according to claim 1 , wherein said effective optical surface of said large-diameter lens element is circular in shape except in said lower direction, and
wherein, in said lower direction, said effective optical surface of said large-diameter lens element comprises a straight side, which is parallel to said post-bending optical axis and orthogonal to a plane on which both said post-bending optical axis and said pre-bending optical axis lie, to define a D-cut shape.

4. The imaging optical system according to claim 1 , further comprising a first lens element on said object side of said bending optical element.

5. The imaging optical system according to claim 1 , wherein said imaging optical system is a retrofocus type in which a negative lens group and a positive lens group are arranged, as a whole, in that order from said object side, and
wherein said large-diameter lens element is included in said positive lens group.

6. The imaging optical system according to claim 1 , wherein said large-diameter lens element is at a position at which an entrance pupil of said imaging optical system is similar in shape to said effective optical surface of said large-diameter lens element.

7. An imaging optical system, comprising:
a bending optical element which bends a light bundle emanating from an object;
a post-bending lens system on a post-bending optical axis defined by an optical axis of said imaging optical system being bent by said bending optical element; and
an image sensor, on which an image of said object is formed via said post-bending lens system,
wherein an outer shape of an effective optical surface of a large-diameter lens element, an axial light bundle effective radius of which is greatest among all lens elements of said post-bending lens system, is formed to be non-circular as viewed in a direction of said post-bending optical axis, and
wherein a shape of an entrance pupil of said imaging optical system satisfies the following conditions:
RU′>RL′,
( RU′+RL′ )<2 RH′ , and
0.5<{( RU′+RL′ )/2 RH′ }<0.09,

wherein, when the entrance pupil is viewed in a direction along a pre-bending optical axis, where an lower direction designates a direction parallel to said post-bending optical axis which travels toward the image sensor side, a upper direction designates a direction opposite to said lower direction, and a horizontal direction designates a direction orthogonal to a plane on which both a pre-bending optical axis and said post-bending optical axis lie,
RU′ designates a distance between said pre-bending optical axis and an outermost point of the entrance pupil in said upper direction,
RL′ designates a distance between said pre-bending optical axis and an outermost point of the entrance pupil in said lower direction, and
RH′ designates a distance between said pre-bending optical axis and an outermost point of the entrance pupil in said horizontal direction.

Assignees

• Hoya Corp

Inventors

• Nomura Hiroshi
• Tada Eijiroh

Classifications

• G02B13/005 Primary

  having spherical lenses only · CPC title

• G02B13/04

  Reversed telephoto objectives · CPC title

• G02B13/0065 Primary

  having a beam-folding prism or mirror · CPC title