Optical: systems and elements – Image stabilization
Reexamination Certificate
2001-01-26
2003-07-01
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Image stabilization
C359S557000, C396S052000, C396S055000
Reexamination Certificate
active
06587270
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved shake correcting apparatus for correcting shake, e.g., in a camera, by driving a correcting system using electromagnetic driving means which comprises a coil unit and a permanent magnet.
2. Description of the Related Art
In recent cameras, principal image pick-up operations such as exposure time determination and focusing have been entirely automated, so that even people inexperienced in camera operation can perform image pick-up with rare failure.
Also, a system for preventing shake applied to a camera has been recently developed, so that there is no factor inducing failure in image pick-up.
A system for preventing camera shake will now be simply described.
Camera-shake generally has frequencies of 1 to 10 Hz. A basic concept for enabling image pick-up while eliminating shake, even when such shake is produced at the time of shutter release, is that vibration due to camera-shake is detected and a correction lens displaced according to the detected value. Therefore, in order to take a photograph without image-shake, even when camera-shake is produced, it is required that vibration of a camera is first detected and then changes in an optical axis due to the camera-shake are corrected.
The vibration (camera-shake) is principally detected by attaching vibration detecting means to a camera for detecting linear acceleration, angular acceleration, angular velocity, angular displacement, and so forth, and for properly computing the output for camera-shake correction. Based on the detected information, image-shake control is performed by driving a camera-shake correcting apparatus that varies an image pick-up optical axis.
A conventional camera-shake correcting apparatus such as the apparatus disclosed in Japanese Patent Laid-Open No. 10-26779 comprises a supporting frame for supporting a lens or an image pick-up element, a correcting system having a permanent magnet fixed to the supporting frame for generating a magnetic field approximately parallel to an optical axis of the lens or the image pick-up element, and a supporting member for supporting the correcting system movably on a surface orthogonal to the optical axis and having a coil at a position opposing the permanent magnet for the purpose of reducing the size and weight of the apparatus.
In order to drive the supporting frame by such a shake correcting apparatus in a plane orthogonal to an optical axis of the lens or the image pick-up element, a permanent magnet (which is not a coil requiring connections for electric supply) is provided on a side of the correction system (the supporting frame side), so as to eliminate any requirement for supplying electricity to the correction system to drive it, and so as to dispense with any connection process required for electric supply.
FIGS. 12 and 13
illustrate a specific structure, in which yokes
505
p
and
505
y
having permanent magnets
503
p
and
503
y
respectively adhered thereon are fixed to a supporting frame
502
for supporting a correction lens
501
by crimping or screwing (permanent magnets
503
p
and
503
y
have complimentary structures in the pitch and yaw orientations, respectively; thus, for simplicity only the permanent magnet
503
p
is shown in FIG.
13
). Coils
507
p
and
507
y
are attached on a surface of a bottom board
506
opposing the permanent magnets
503
p
and
503
y
(coils
507
p
and
507
y
have complimentary structures in the pitch and yaw orientations, respectively; thus, for simplicity only coil
507
y
is shown in FIG.
13
).
In a shake correcting apparatus disclosed in Japanese Patent Laid-Open No. 10-26780, as shown in
FIGS. 14A
to
14
C, a coil
507
p
(
507
y
) having substantially the same structure as mentioned above is fixed to a bottom board (not shown) for supporting the correction lens with claws
509
, etc., via a frame board
508
so as to simplify assembling.
In a shake correcting apparatus disclosed in Japanese Patent Laid-Open No. 11-212134, as shown in
FIG. 15
, a coil unit
606
p
having a coil
605
is pulled in and fixed to a bottom board
601
with a screw
604
inserted into a hole
603
from the bottom surface of the bottom board
601
as viewed in the drawing. In order to maintain high accuracy in an air gap, coil retainers
607
and
608
are formed on the bottom board
601
, enabling the coil unit
606
p
to be positioned so that it is difficult to separate coil unit
606
p
from positioning projections
609
. The coil retainers
607
and
608
also prevent the coil unit
606
p
from being warped and deflected when it is pulled in with the screw
604
so as to avoid interfering with permanent magnet
610
p
, etc. In addition, a substrate
602
is provided for mounting electrical components.
Also, in an actuator for a vibration proof apparatus disclosed in Japanese Patent Laid-Open No. 11-135597, as shown in
FIG. 16
, there are arranged a magnet
701
, a coil
702
disposed so as to oppose the magnet
701
for supplying a driving force to the magnet
701
by electric charging, and a damper board
703
being a non-magnetic metallic plate and disposed between the magnet
701
and the coil
702
, so that a damping effect is obtained by utilizing magnetic friction produced between the damper board
703
and the magnet
701
. The coil
702
is fixed to the damper board
703
, thereby facilitating control of an air gap between the magnet
701
and the coil
702
; inserting the damper board
703
thus enables the structure to restrain any increase in the air gap as much as possible.
In a shake correcting apparatus as described above, stabilizing a driving force for correcting a shake is required; however, there has been a problem of large individual differences in the generated driving force from one apparatus to another apparatus because, when the thicknesses of the coil, which is liable to vary widely due to manufacturing error, and the coil unit formed of the coil are changed, the air gap between the permanent magnet and the coil, which has a large effect on the driving force for correcting the shake, is also changed.
As the air gap decreases, the driving force is increased; however, there has been a limit in the amount the air gap may be decreased while still avoiding contact between the coil and the permanent magnet due to a warp of the coil. For example, a structure disclosed in Japanese Patent Laid-Open No. 11-212134, shown in
FIG. 15
, is provided to improve accuracy in the air gap; however, since the coil unit
606
p
is pulled in and fixed to the bottom board
601
with the screw
604
inserted into the hole
603
from the bottom surface of the bottom board
601
as viewed in the drawing, an abutting face of the coil unit
606
p
is not a surface opposing the permanent magnet
610
p
, but an opposite surface thereto, so that when the thickness of the coil unit
606
p
varies, an air gap between the permanent magnet
610
p
and the coil
605
also varies. Although forming the coil retainers
607
and
608
on the bottom board
601
prevents the coil unit
606
p
from being warped and deflected when it is pulled in with the screw
604
so as to avoid interfering with a permanent magnet
610
p
, etc., since the position of the coil
605
is not always restricted by the coil retainers
607
and
608
, variation in an air gap cannot be reliably prevented.
Also, in an actuator for a vibration proof apparatus disclosed in Japanese Patent Laid-Open No. 11-135597, as shown in
FIG. 16
, although fixing the coil
702
to the damper board
703
facilitates controlling the size of an air gap between the magnet
701
and the coil
702
, since there is rarely a gap between a bottom board
704
and the coil
702
, when the thickness of the coil
702
varies (e.g., becomes larger, as shown in FIG.
17
), the air gap also varies. That is, fixing the coil
702
to the damper board
703
, alone, cannot absorb variation in the thickness of the coil
702
.
SUMMARY OF THE INVENTION
It is one object of the present invention to provi
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