Photography – Camera shake sensing – Having stabilization system
Reexamination Certificate
1999-06-29
2001-12-04
Perkey, W. B. (Department: 2851)
Photography
Camera shake sensing
Having stabilization system
Reexamination Certificate
active
06327433
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement in a driving apparatus for driving a moving member, a correction optical apparatus having a correction optical system, or an image blur correction apparatus having the correction optical apparatus.
2. Related Background Art
For an existing camera, since exposure determination, focusing and other operations important for photographing are all automated, even a person unskilled in camera operation has a very little possibility of causing a photographing failure.
Moreover, a system for correcting image blur caused by manual vibration applied to the camera has been recently researched, and factors for inducing photographer's photographing failure have almost been eliminated.
Here, a system for correcting image blur caused by manual vibration will briefly be described.
The manual vibration of the camera during photographing is a vibration having a frequency normally in the range of 1 Hz to 12 Hz. In order to enable a photo with no image blur to be taken even if such manual vibration occurs at the time of releasing a shutter, as a basic idea, camera vibration caused by the manual vibration is detected, and a correction lens has to be displaced in accordance with the detected value. Therefore, in order to enable photos to be taken in such a manner that no image blur occurs even if manual vibration occurs, first, the camera vibration needs to be exactly detected, and secondly, an optical axis change caused by the camera vibration needs to be corrected by displacing the correction lens.
The vibration (camera vibration) can be detected, in principle, by mounting, on the camera, a vibration detection apparatus comprising a vibration detector for detecting acceleration, speed and the like and a calculation portion for electrically or mechanically integrating output signals of the vibration detector to output displacement. Subsequently, by controlling a correction optical apparatus in an image blur correction apparatus mounted to displace a correction optical system based on the detected information and to change a photographing optical axis, image blur correction can be realized.
As a conventional example of driving means of the correction optical system, a driving portion is used in which a coil and a magnet opposed thereto are used, the magnet is disposed on a fixed portion, the coil is disposed on the correction optical system, and an electric current is supplied to the coil for driving. A vertical vibration direction when a camera is set up in a positive position (hereinafter referred to as the pitch direction) and a transverse vibration direction orthogonal to the pitch direction (hereinafter referred to as the yaw direction) are detected, two pairs of the driving portions are correspondingly arranged to correct vibrations in the pitch and yaw directions, and the two directions are driven independently of each other. Such driving means is proposed.
FIG. 9
is a perspective view showing a coil and magnets in an example of a conventional driving means, and
FIGS. 10A and 10B
are schematic views showing the relationship of the magnets and coil constituting the conventional driving means.
In the drawings, a first magnet
901
is polarized at
901
a
and
901
b,
has a central non-magnetized neutral area
901
c,
and is fixed to a base plate (not shown). In the same manner as the first magnet
901
, a second magnet
902
is polarized at
902
a,
902
b,
has a central non-magnetized neutral area
902
c,
and is fixed to a base plate (not shown). The first, second magnets
901
and
902
are attached to first, second yokes
903
and
904
, respectively, to constitute a closed magnetic circuit having a flow of magnetic flux as shown by an arrow B. A flat coil
905
disposed between the opposed first and second magnets
901
,
902
is integrally attached to a support frame
907
for supporting a correction optical system
906
, and driven in a direction shown by an arrow C by supplied electricity.
Additionally,
FIG. 10A
shows that the correction optical system
906
is positioned in a driving center, and
FIG. 10B
shows that the correction optical system
906
is driven by a maximum driving amount in the direction of the arrow C, and positioned in a driving end. Furthermore, a thrust applied to the coil
905
is a product of a magnetic flux density passed through the coil
905
, a current supplied to the coil
905
and an effective length of the coil through which the magnetic flux passes. Moreover, the effective length of the coil
905
through which the magnetic flux passes is proportional to a width L
0
in which the coil is opposed to the magnets (of a driving direction of the coil constituted integrally with the correction optical system). Therefore, when a magnetic flux leakage in the closed magnetic circuit is ignored, the thrust applied to the coil is substantially proportional to the width L
0
of the coil opposed to the magnets.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided an image blur correction apparatus comprising a movable portion for moving to correct an image blur and a driving device for operating the movable portion. The driving device comprises a coil integrally provided on the movable portion, and a magnet disposed opposite at the coil.
For a relationship of a width of a driving direction of the coil and a width of the opposite magnet, the width of the magnet is set larger than the width of the coil, and smaller than a length obtained by adding to the width of the coil a movement length of the coil corresponding to a maximum driving length of the movable portion.
REFERENCES:
patent: 4853734 (1989-08-01), Tokura et al.
patent: 4963905 (1990-10-01), Haraguchi et al.
patent: 5537174 (1996-07-01), Ishikawa
patent: 5724194 (1998-03-01), Ishikawa
patent: 5937212 (1999-08-01), Kurahashi et al.
patent: 5974269 (1999-10-01), Sato et al.
patent: 5995762 (1999-11-01), Enomoto et al.
patent: 6011927 (2000-01-01), Kamata
Ishikawa Masanori
Shinohara Mitsuru
Watanabe Takashi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Perkey W. B.
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