Imaging optical system

Patent metadata

Field	Value
Publication number	US-9429767-B2
Application number	US-201514677380-A
Country	US
Kind code	B2
Filing date	Apr 2, 2015
Priority date	Apr 23, 2014
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

An imaging optical system includes a front lens group including a front lens element and a reflector element which reflects a light bundle that exits from the front lens element; and a rear lens group on the image side of the front lens group. The front lens element is a spherically-swingable lens group which suppresses image shake by spherically-swinging about a predetermined spherical-swing center in accordance with vibrations applied to the imaging optical system. The following conditions (1) and (2) are satisfied:

ν d >58  (1),

and

f/y >3  (2),

wherein νd designates the Abbe number with respect to the d-line of at least one lens element of the spherically-swingable lens group, f designates the focal length of the imaging optical system, in a state where the focal length is at a maximum, and y designates the maximum image height of the imaging plane.

First claim

What is claimed is:

1. An imaging optical system comprising:
a front lens group including at least one front lens element, and a reflector element which reflects a light bundle that exits from said front lens element, in that order from the object side; and
a rear lens group provided on the image side of said front lens group,
wherein said front lens element serves as a spherically-swingable lens group which, in an image-stabilizing operation, suppresses image shake on the imaging plane by spherically-swinging said spherically-swingable lens group about a predetermined spherical-swing center in accordance with vibrations applied to said imaging optical system, and
wherein the following conditions (1) and (2) are satisfied:
ν d> 58  (1),

and
f/y> 3  (2),

wherein
νd designates the Abbe number with respect to the d-line of at least one lens element of said spherically-swingable lens group;
f designates the focal length of said imaging optical system, in a state where the focal length is at a maximum; and
y designates the maximum image height of the imaging plane.

2. The imaging optical system according to claim 1 , wherein the following condition (3) is satisfied:
−2< SF< 0  (3),

wherein
SF=(R2+R1)/(R2−R1);
R1 designates the radius of curvature of the surface closest to the object side on said spherically-swingable lens group; and
R2 designates the radius of curvature of the surface closest to the image side on said spherically-swingable lens group.

3. The imaging optical system according to claim 1 , wherein the following condition (4) is satisfied:
−0.3<( SC−R 2)/ f 1<0  (4),

wherein
SC designates the distance from the surface closest to the image side on said spherically-swingable lens group to said predetermined spherical-swing center;
R2 designates the radius of curvature of the surface closest to the image side on said spherically-swingable lens group; and
f1 designates the focal length of said spherically-swingable lens group.

4. The imaging optical system according to claim 1 , wherein said spherically-swingable lens group comprises a single lens element.

5. The imaging optical system according to claim 4 , wherein said single lens element, which serves as said spherically-swingable lens group, has a negative refractive power.

6. The imaging optical system according to claim 5 , wherein said single lens element, which serves as said spherically-swingable lens group, has a concave surface on the image side thereof.

7. The imaging optical system according to claim 5 , wherein the surface on the object side of said single lens element, which serves as said spherically-swingable lens group, has a smaller refractive power than the surface on the image side thereof.

8. The imaging optical system according to claim 1 , wherein, in a reference state in which said image-stabilizing operation is not carried out, said predetermined spherical-swing center is positioned on an extension of an optical axis, of said spherically-swingable lens group, extending behind an underside of a reflection surface of said reflector element.

9. The imaging optical system according to claim 1 , wherein said front lens group comprises a negative single lens element, which serves as said spherically-swingable lens group, having a concave surface on the image side thereof, said reflector element, a positive single lens element having a convex surface on the image side, and a negative single lens element having a concave surface on the object side, in that order from the object side.

10. The imaging optical system according to claim 1 , wherein said front lens group comprises a negative single lens element, which serves as said spherically-swingable lens group, having a concave surface on the image side thereof, said reflector element, a biconcave single lens element, and a positive meniscus lens element having a convex surface on the object side.

11. The imaging optical system according to claim 1 , wherein said front lens group comprises a negative single lens element, which serves as said spherically-swingable lens group, having a concave surface on the image side thereof, said reflector element, and a positive meniscus lens element having a convex surface on the object side.

Assignees

• Hoya Corp

Inventors

• Takakubo Yutaka

Classifications

• G02B27/646 Primary

  compensating for small deviations, e.g. due to vibration or shake (movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68) · CPC title

• G02B13/0065

  having a beam-folding prism or mirror · CPC title

• G02B15/177

  having a negative front lens or group of lenses · CPC title

• G02B15/144515

  arranged -+++ · CPC title

• G02B15/144511

  arranged -+-+ · CPC title