Optical: systems and elements – Image stabilization – By movable refractive structure
Reexamination Certificate
1999-09-09
2001-03-06
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Image stabilization
By movable refractive structure
C359S407000, C359S409000, C359S554000
Reexamination Certificate
active
06198575
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical system for an observing device such as a binocular or a terrestrial telescope that has an image-vibration compensation system.
Recently, binoculars provided with image-vibration compensation systems for preventing vibration of an observed image due to a hand-held shake of a user have been developed. Japanese Laid Open Publication No. HEI 6-43365 discloses an image-vibration compensation system of a binocular that employs a variable angle prism for each of the telescopic optical systems of the binocular.
FIG. 37
shows one example of the telescopic optical system that has the same arrangement of the optical components as the publication. The optical system includes an objective lens
1
that is a cemented doublet, a variable angle prism
2
as a compensation element, an erecting system
3
and an eyepiece
4
. When the optical system vibrates due to hand-held shake of a user, the vertex angle of the variable angle prism
2
is controlled to stabilize the image.
In such a construction, however, since the variable angle prism
2
is located in the convergent light, if the vertex angle of the prism is changed, significant decentering coma occurs.
FIG. 38
shows the axial coma at a standard condition where the vertex angle of the variable angle prism
2
is 0 degrees.
FIG. 39
shows the axial coma when the variable angle prism
2
is angled to stabilize the image when the optical system is inclined by 1 degree. The image viewed by a user is deteriorated due to the decentering coma when the variable angle prism
2
is angled to compensate for the vibration of the image. While
FIGS. 38 and 39
show the change of the coma in the specific example, the image vibration compensation system having the variable angle prism tends to generate the decentering coma in general.
Another example of the image-vibration compensation system for binoculars is disclosed in Japanese Laid Open Publication No. HEI 6-308431. The binocular in the publication employs a compensation device that is attached in front of the objective optical systems of the binocular. This arrangement can reduce the decentering coma when the compensation prism is angled. However, since the first lens of the objective optical system has the largest diameter in the telescopic optical system, in general, and the device is arranged in front of the first lenses, the device becomes large in size, which increases the size of the binocular.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an optical system of an observing device having image-vibration compensation system, which is capable of preventing the decentering coma without increasing the size of the device.
For the above object, according to the present invention, there is provided an optical system of an observing device having an image-vibration compensation system. The optical system includes an objective optical system, an erecting system and an observing optical system arranged in the order from an object side, the objective optical system consisting of:
a first lens having positive refractive power, at least one lens surface of the first lens being an aspherical surface;
a second lens arranged at the erecting system side of the first lens; and
a third lens arranged at the erecting system side of the second lens,
wherein one of the second and third lenses has positive refractive power and the other has negative refractive power, and
wherein the first lens is movable in a direction orthogonal to an optical axis of the objective optical system to compensate an image vibration due to a hand-held shake.
With this construction, since the first lens of the objective optical system is moved to compensate the image vibration, the decentering coma does not generate when the image vibration is compensated. Further, since the compensation element is a part of the objective optical system, the size of the observing device becomes smaller than the conventional device in which the extra prism is arranged at the object side of the objective optical system.
The optical system is preferable to satisfy the following conditions (1), (2) and (3):
0.5<|(tan 1°)/&phgr;
1
|<5.0 (unit:mm) (1)
|&phgr;
23
/&phgr;
13
|<1.00 (2)
1.0
<hi/hx<
1.5 (3)
where,
&phgr;
1
is a refractive power of the first lens,
&phgr;
23
is a composite refractive power of the second and third lenses,
&phgr;
13
is a composite refractive power of the objective optical system,
hi is a height from an optical axis of an intersecting point of a paraxial axial ray on the object side surface of the second lens (hi≠0), and
hx is a height from an optical axis of an intersecting point of the paraxial axial ray on the erecting system side surface of the third lens.
In the specification and claims, “the paraxial axial ray” is defined as a ray from an object point on an optical axis at infinity.
Further, the first lens of the objective optical system may be a plastic lens.
The second and third lenses may be cemented together. In such a case, the condition (4) is preferably satisfied:
−0.3<&phgr;
4
/&phgr;
13
<0.0 (4)
where,
&phgr;
4
is a refractive power of the cemented surface of the second and third lenses.
On the other hand, the second and third lenses may be independently arranged without being cemented. In such a case, the condition (5) is preferably satisfied:
D
23
/f
13
<0.2 (5)
where,
D
23
is a distance between the object side surface of the second lens and the erecting system side surface of the third lens, and
f
13
is a focal length of the objective optical system.
REFERENCES:
patent: 5000549 (1991-03-01), Yamazaki
patent: 5521758 (1996-05-01), Hamano
patent: 5581400 (1996-12-01), Takase et al.
patent: 5694244 (1997-12-01), Abe et al.
patent: 5917653 (1999-06-01), Taniguchi
patent: 61-156019 (1986-07-01), None
patent: 6-43365 (1994-02-01), None
patent: 6-308431 (1994-11-01), None
Asahi Kogaku Kogyo Kabushiki Kaisha
Greenblum & Bernstein P.L.C.
Nguyen Thong
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