Photography – With exposure objective focusing means – focusing aid – or... – Mechanical mechanism for displacement of exposure objective
Reexamination Certificate
2002-03-05
2003-11-25
Adams, Russell (Department: 2851)
Photography
With exposure objective focusing means, focusing aid, or...
Mechanical mechanism for displacement of exposure objective
C359S823000
Reexamination Certificate
active
06654557
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a lens driving apparatus which performs focus adjustment (hereinafter abbreviated as focusing) by performing lens position adjustment of a master lens when a subject is photographed using a video camera or the like and, more particularly, to a lens driving apparatus which can prevent defocusing during a zooming operation resulting from manual focusing, or defocusing of a photographed image which would otherwise result from a difference between positions during photographing.
BACKGROUND ART
Conventionally, a focusing operation of a lens driving apparatus included a video camera or the like, which is disclosed in Japanese Published No. Hei.
6-308361
, has been known, and this will be described with reference to figures hereinafter.
FIG. 8
is a perspective view illustrating a main portion of a conventional lens driving apparatus.
FIG. 9
is an expanded cross sectional view illustrating a relationship between a feed screw and a first arm of a driving member in the lens driving apparatus shown in FIG.
8
.
FIG. 10
is an expanded cross sectional view illustrating a relationship between the feed screw and a second arm of the driving member in the lens driving apparatus shown in FIG.
8
.
FIG. 11
is an expanded cross sectional view illustrating a combination relationship between the driving member and a lens holding frame in the lens driving apparatus shown in FIG.
8
.
FIG. 12
is an expanded cross sectional view illustrating a combination and protective relationship between the driving member and the lens holding frame in the lens driving apparatus shown in FIG.
8
.
FIG. 13
is a cross sectional view of a main section illustrating the conventional lens driving apparatus when the apparatus is faced in a horizontal direction to perform photographing. And,
FIG. 14
is a cross sectional view of a main section illustrating the conventional lens driving apparatus during tilt-photographing.
A structure of the conventional lens driving apparatus will be described hereinafter. In
FIG. 8
, a lens
1
, which performs focusing of a subject is fixed to a lens holding frame
2
, made of a resin, by performing an operation such as heat-staking. The lens holding frame
2
is held by a first guide pole
3
and a second guide pole
4
, which are arranged in a fixed body tube (not shown) so as to be slidable in the direction of a lens optical axis
5
. Further, there is provided a groove
2
a
on an upper part of the lens holding frame
2
, which groove connects a driving member
9
to the lens holding frame
2
. There is further provided a feed screw
7
a
in a driving shaft
7
of a motor
6
, which motor is attached to the fixed body tube. The driving member
9
made of a resin is slidably held by a third guide pole
10
arranged at a motor mounting body
8
and extending parallel to the driving shaft
7
. Furthermore, the driving member
9
is provided with a notch nut
9
a
which is threadedly engaged with the feed screw
7
a
as shown in
FIG. 9
, and is also provided with a first arm
9
b
having spring characteristics for supporting the feed screw
7
a
by sandwiching the feed screw.
On the other hand, a second arm
9
d
is formed on the driving member
9
as shown in
FIG. 10
, and a gap between the second arm
9
d
and a thread part of the feed screw
7
a
is constructed so as to have a smaller gap size than a screw-thread height size of the notch nut
9
a
. Further, as shown in
FIG. 11
, at a portion of the driving member
9
that is connected with the lens holding frame
2
there is provided an edge portion
9
c
having enough rigidity to slidably move the lens holding frame
2
, and also having spring characteristics. This edge portion
9
c
is inserted into the groove
2
a
in the direction of the arrow, thereby constructing a backlash-free connection in the direction of the lens optical axis
5
. Further, as shown in
FIG. 12
at the portion of the driving member that is connected with the lens holding frame
2
there is provided a stopper edge portion
9
e
which does not abut the groove
2
a
, so that the edge portion
9
c
having the spring characteristics is not curved to a spring limit due to shock.
In the conventional lens driving apparatus so constructed, an operation thereof will be described hereinafter. The feed screw
7
a
formed in the driving shaft
7
is inserted into the notch nut
9
a
of the driving member
9
so as to be pressured and energized by the first arm
9
b
having the spring characteristics. In this case, since the driving member
9
is slid by the third guide pole
10
to move in the direction of the lens optical axis
5
when the motor
6
rotates, the lens holding frame
2
connected to the driving member
9
is also slid by the first guide pole
3
and the second guide pole
4
in accordance with rotation of the motor
6
to move in the direction of the lens optical axis
5
, thereby to obtain focusing of the lens
1
.
However, in this construction, the driving member
9
supports the feed screw
7
a
by sandwiching it through the notch nut
9
a
and the first arm
9
b
. Therefore, when the feed screw
7
a
vibrates during rotation of the motor
6
, this vibration is directly transmitted to the driving member
9
, thereby causing the driving member to vibrate around the third guide pole
10
. Since the driving member
9
and the lens holding frame
2
are connected to each other in the direction of the lens optical axis
5
by the edge portion
9
c
, having spring characteristics, without backlash, vibration is transmitted to the lens holding frame
2
without being completely absorbed in the edge portion
9
c
, and therefore, the lens vibrates, whereby, when focusing is performed, an image shakes so that a photographed video becomes hard to view.
Further, even when a tilt-photography is performed by a video camera which is provided with this lens driving apparatus, there is a problem as follows. Specifically, when a focusing operation is performed while photographing is performed in a state where the video camera is horizontal, the lens holding frame
2
, which holds the lens
1
, is slid by the first guide pole
3
and the second guide pole
4
. Also, the driving member
9
is slid by the third guide pole
10
, and the lens holding frame
2
and the driving member
9
, having respective clearances d, horizontally move in the direction of the lens optical axis
5
to perform focusing as shown in FIG.
13
.
When photographing is performed in a slightly tilted state from this state, as shown in
FIG. 14
, the edge portion
9
c having the spring characteristics cannot absorb a slope of the lens holding frame
2
, and therefore, the lens holding frame
2
tilts in a self-weight direction of the lens
1
shown by an arrow W
3
, by a smaller of a clearance D
2
maintained between the first guide pole
3
and the lens holding frame
2
and a clearance D
3
maintained between the third guide pole
10
and the driving member
9
, thereby accordingly generating a tilt of the lens
1
and then a single blur phenomenon of a photographed video.
The present invention is made to solve these problems, and has for its object to provide a lens driving apparatus which faithfully transmits a feed displacement of a motor as feed displacement of a lens, has a stable driving performance, and wherein a photographed video does not vibrate due to a vibration of the motor.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, provided is a lens driving apparatus having a lens holding frame which holds a lens and is guided by a first guide pole and a second guide pole to slidably move in a lens optical axis direction. The apparatus further has a driving shaft having a feed screw which is rotated and driven by a motor, and a driving member which has a rack threadedly engaged with the feed screw of the driving shaft at one end and is engaged with the lens holding frame at another end. The driving member is rotatably mounted to a positioning dowel which is provided on the lens holding frame and exten
Kikuchi Yoshihiro
Takabatake Yukihiro
Adams Russell
Matsushita Electric - Industrial Co., Ltd.
Smith Arthur A.
Wenderoth , Lind & Ponack, L.L.P.
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