Optical: systems and elements – Image stabilization – By movable refractive structure
Reexamination Certificate
2000-06-13
2001-06-19
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Image stabilization
By movable refractive structure
C359S407000, C359S431000, C359S554000
Reexamination Certificate
active
06249380
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image-blur correcting optical system suitable for a viewing optical apparatus with an image-blur correcting function.
2. Description of the Related Art
As an image-blur correcting optical system for a viewing optical apparatus, such as a binocular, a telescope and the like, the optical system, for example, disclosed in Japanese Unexamined Patent Publication No. Hei-10-186228 is known in the art. The image-blur correcting optical system disclosed therein is provided in an objective optical system constituted by a front lens group and a rear lens group, in this order from the object. An image-blur correction is conducted by moving the negative rear lens group in a direction substantially perpendicular to the optical axis. This image-blur correcting optical system is designed to be used in a viewing optical apparatus, such as a spotting scope, having a very long objective optical system. Therefore in order to provide an image-blur correcting apparatus (e.g., an actuator) in the objective optical system, a sufficient space for that purpose is secured therein. Further, since a negative lens element is used as an image-blur correcting lens element to shorten the objective optical system, the overall length thereof is less than or equal to the focal length of the objective optical system, which contributes to miniaturization of a viewing optical apparatus. Due to the above arrangement of the objective optical system, the spotting scope can be made enough short; however, the same arrangement is still considered to be too long for an objective optical system for a binocular or the like. Accordingly, the above image-blur correcting optical system cannot be applied to a viewing optical apparatus, such as a binocular or the like, in which the overall length of the objective optical system is inherently short and no sufficient space is maintained for an image-blur correcting apparatus.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a miniaturized and light (less heavier) image-blur correcting optical system which has high optical performance, and can provide a space for an image-blur correcting apparatus in a viewing optical apparatus in which the overall length of the objective optical system is short.
In order to achieve the above-mentioned object, there is provided an image-blur correcting optical system including an objective optical system, an image-erecting optical system, and an eyepiece optical system, in this order from the object. The objective optical system includes a front lens group and a rear lens group, in this order from the object, and the front lens group is made immoveable. The image-blur correcting optical system includes a positive blur-correcting lens group constituted by the rear lens group which is arranged to move in a direction perpendicular to the optical axis, in accordance with the magnitude of a shake imposed on the optical system. The image-blur correcting optical system satisfies the following conditions:
0.04
<A/fO
<0.2 (1)
0.35
<B/fO
<0.5 (2)
TL/fO
>1.1 (3)
wherein
A designates the distance between the blur-correcting lens group (the rear lens group) and an optical element which is positioned on the object-side of the blur-correcting lens group;
B designates the distance between the blur-correcting lens group and an optical element which is positioned on the operator's eye-side (hereinafter, eyepiece-side) of the blur-correcting lens group;
fO designates the focal length of the entire objective optical system; and
TL designates the distance between the object-side surface of the most object-side lens element in the objective optical system and the image plane thereof. The image plane is depicted by the dashed line
15
of FIG.
13
.
Due to this arrangement, even in a miniaturized viewing optical apparatus, such as a binocular, which has the short objective optical system, a space for an image-blur correcting apparatus can be secured while suitable optical performance is maintained.
In order to correct aberrations effectively through the objective optical system, the following condition is preferably satisfied:
0.2<∅1/∅2<0.8 (4)
wherein
∅1 designates the power of the front lens group of the objective optical system; and
∅2 designates the power of the rear lens group of the objective optical system.
Furthermore, in order to obtain suitable sensitivity on the movement of the blur-correcting lens group, the objective optical system preferably satisfies the following condition:
0.5<|tan 1°/(∅0 −∅1)|<5 (5)
wherein ∅0 designates the power of the entire objective optical system.
The present disclosure relates to subject matter contained in Japanese Patent Application No.Hei-11-166501 (filed on Jun. 14, 1999) which is expressly incorporated herein by reference in its entirety.
REFERENCES:
patent: 5917653 (1999-06-01), Taniguchi
patent: 6046853 (2000-04-01), Yano
patent: 6072630 (2000-06-01), Yano
patent: 6118585 (2000-09-01), Kanai
patent: 10186228 (1998-07-01), None
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Nguyen Thong
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