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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera having a lens barrel that can be
extended and collapsed between a predetermined extended position and a
predetermined collapsed position, the camera taking images by capturing
object light incident via an image taking lens set in the extended
position.
2. Description of the Related Art
Camera have hitherto been known which contain an image taking lens composed
of multiple lens groups, have a lens barrel that can be extended and
collapsed between a predetermined extended position and a predetermined
collapsed position, and takes images by capturing object light incident
via the image taking lens set in the extended position.
Some of these cameras have a lens barrier that is closed when the lens
barrel is in the predetermined collapsed position and that is opened when
the lens barrel is brought into the predetermined extended position (for
example, refer to Patent Document 1).
Further, the lens barrel, which is extended and collapsed, is provided with
a backlash compensating mechanism in order to allow images to be taken
more accurately.
<Patent Document 1>
Japanese Patent Laid-Open No. 7-49515
In this case, when the lens barrel is provided with a lens barrier opening
and closing mechanism and a backlash compensating mechanism, the size of
the lens barrel increases because it is provided with various other parts.
This may hinder efforts to reduce the size of the camera.
SUMMARY OF THE INVENTION
In view of the above circumstances, it is an object of the present
invention to provide a camera having its size reduced by improving the
arrangement of a backlash compensating mechanism and a lens barrier
opening and closing mechanism for a lens barrel that can be extended and
collapsed.
To accomplish this object, the present invention provides a camera
containing an image taking lens composed of multiple lens groups and
having a lens barrel that can be extended and collapsed between a
predetermined extended position and a predetermined collapsed position,
the camera taking images by capturing object light incident via the image
taking lens set in the extended position:
the lens barrel has:
a first lens group holding section that holds a first lens group of the
multiple lens groups which is disposed at a front position; and
a second lens group holding section that holds a second lens group disposed
adjacent to and behind the first lens group, and
the first lens group holding section holds the first lens group and a lens
barrier that can be freely opened and closed to cover a front surface of
the first lens group and that is urged in a direction in which the lens
barrier is closed, and the first lens group holding section further has a
lens barrier opening member that opens the lens barrier when urged
backward, while allowing the lens barrier to be moved in the closed
direction when the urging is relieved, and
the lens barrier further has an elastic member connecting the second lens
group holding section and the lens barrier opening member of the first
lens group holding section together, and urges the lens barrier opening
member toward the second lens holding member as the lens barrel is moved
to the extended position, while relieving the urging as the lens barrel is
moved to the collapsed position.
With the camera according to the present invention, the opening of the lens
barrier interacts with the compensation of backlash occurring between the
first lens group holding section and the second lens group holding
section. Consequently, unlike the independent provision of a mechanism
that opens the lens barrier and a mechanism that prevents the camera from
shaking, the camera according to the present invention allows a shared
mechanism to achieve these mechanisms thereby simplifying these mechanisms
to contribute to a reduction in the size of the camera.
In this case, the second lens group holding section may have a projection
that contacts with the lens barrier opening member to push the lens
barrier opening member forward when the lens barrel is moved to the
collapsed position, and the lens barrier opening member may be pushed by
the projection to allow the lens barrier to be moved in the closed
direction.
This arrangement allows the closure of the lens barrier to be controlled
using a simple mechanism.
According to the camera of the present invention, it is possible to reduce
the sizes of a backlash compensating mechanism and lens barrier opening
and closing mechanism of a lens barrel that can be extended and collapsed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view showing the appearance of an embodiment of a
camera according to the present invention;
FIG. 2 is a perspective view showing the appearance of the embodiment of
the camera according to the present invention;
FIG. 3 is a sectional view taken along an optical axis in which a lens
barrel of the camera is collapsed;
FIG. 4 is a sectional view taken along the optical axis in which the lens
barrel is maximally extended;
FIG. 5 is a schematic view showing a configuration of a lens barrier
opening and closing mechanism provided in the lens barrel;
FIG. 6 shows that the ring is being rotatively moved by a ring
rotative-moving lever; and
FIG. 7 is a conceptual drawing showing operations of the lens barrier
opening and closing mechanism.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present invention will be described below.
FIGS. 1 and 2 are perspective views showing the appearance of an embodiment
of a camera according to the present invention.
FIG. 1 shows of a camera 1 according to the present embodiment, in which a
lens barrel 100 containing a zoom lens is collapsed. FIG. 2 shows an
extended state in which a lens barrier of the lens barrel 100 of the
camera 1 is opened.
The lens barrel 100 of the camera 1, shown in FIGS. 1 and 2, contains a
first lens group located in a front position of the camera, a second lens
group located adjacent to and behind the first lens group, and a third
lens group located closer to a rear surface of the camera.
A flash light emitting window 12 and a finder objective window 13 are
arranged in the upper part of a front surface of the camera 1, shown in
FIGS. 1 and 2. Further, a shutter button 14 is arranged on a top surface
of the camera 1.
A power switch 15 is provided in a left side of the camera 1, shown in
FIGS. 1 and 2. When the power switch 15 is pushed upward to turn on a
power supply, the lens barrel 100, which is collapsed as shown in FIG. 1,
is extended into the lens barrier open state shown in FIG. 2. Further, a
zoom operation switch is disposed on a rear surface (not shown) of the
camera 1. When one side of the zoom operation switch is depressed, the
lens barrel 100, which is in the state shown in FIG. 2, is extended toward
a telephotographic side (frontward) as long as the user depresses the
switch. When the other side of the zoom operation switch is depressed, the
lens barrel 100 is moved to a wide angle side (backward) as long as the
user depresses the switch; the limit of this operation corresponds to the
state shown in FIG. 2. Accordingly, the state shown in FIG. 2 corresponds
to the case in which the zoom is set for the limit of the movement toward
the wide angle side. The power switch 15 is pushed downward to return the
extended lens barrel to the collapsed state shown in FIG. 1, while turning
off the power supply.
Further, the camera 1 is provided with a solid image taking element 400
behind the third lens group. In the camera 1, object light having passed
through the image taking lens forms an object image on the solid image
taking element. When the shutter button 14 is turned on, image data
representative of the object image formed on the solid image taking
element is recorded to take an image.
FIG. 3 is a sectional view taken along an optical axis in which the lens
barrel of the camera is collapsed. FIG. 4 is a sectional view taken along
the optical axis in which the lens barrel is maximally extended.
The lens barrel 100 is provided with an image taking lens 200 composed of a
first lens group 210, a second lens group 220, and a third lens group 230.
The lens barrel 100 can be collapsed and extended between the collapsed
state shown in FIG. 3 and the maximally extended state shown in FIG. 4.
As described previously, the lens barrel 100 is moved between the minimally
extended state shown in FIG. 2 and in which it is slightly extended
forward to open the lens barrier and the maximally extended state shown in
FIG. 4. Thus, the lens barrel 100 is moved in the direction of the optical
axis so as to vary the focal length of the lens groups 210, 220, and 230
as a whole, which constitute the image taking lens 200, provided in the
lens barrel 100. Further, the focus is adjusted by moving only the third
lens group 230 of the image taking lens 200 in the direction of the
optical axis.
Further, in the lens barrel 100, a lens shutter 300 is disposed between the
first lens group 210 and the second lens group 220.
Furthermore, FIGS. 3 and 4 show that a CCD image taking element 400 fixed
to a fixing frame 101 in turn fixed to a camera body is provided behind
the image taking lens 200.
Here, description will be given of operations of the lens barrel 100
performed between the collapsed state shown in FIGS. 1 and 3 and the
maximally extended state shown in FIG. 4.
The lens barrel 100 is provided with the fixing frame 101, fixed to the
camera body, and a driving cylinder 102 that can be rotated relative to
the fixing frame. Although the driving cylinder 102 can be rotated
relative to the fixing frame 101, it is prohibited from moving in the
direction of the optical axis relative to the fixing frame 101. This is
because a projection 102a provided in a circumferential direction is
fitted in a groove in the fixing frame 101 which extends in the
circumferential direction. The driving cylinder 102 has a gear 102b
provided on its outer peripheral surface. Further, a driving gear (not
shown) is meshed with the gear 102b. Accordingly, a driving force from a
motor (not shown) is transmitted via the gear 102b to rotate the driving
cylinder 102.
The driving cylinder 102 is further provided with a key groove 102c
extending in the direction of the optical axis. A cam pin 104 fixed to the
rotative moving cylinder 103 projects into the key groove 102c through a
cam groove formed in the fixing frame 101. Accordingly, when the driving
cylinder 102 is rotated, the rotative moving cylinder 103 is rotated
together with the driving cylinder 102 because the cam pin 104 projects
into the key groove 102c. Furthermore, since the cam pin 104 penetrates
the cam groove in the fixing frame 101, it is moved in the direction of
the optical axis in accordance with the shape of the cam groove while
rotating together with the driving cylinder 102.
Further, a rectilinear moving frame 105 is provided inside the rotative
moving cylinder 103.
The rectilinear moving frame 105 is engaged with the rotative moving
cylinder 103 so as to be rotatable relative to the rotative moving
cylinder 103. Further, the rectilinear moving frame 105 is fitted into the
key groove 101a in the fixing frame 101 and thus prohibited from rotating.
Therefore, when rotation of the driving cylinder 102 causes the rotative
moving cylinder 103 to move in the direction of the optical axis, the
rectilinear moving frame 105 moves together with the rotative moving
cylinder 103. However, the rectilinear moving frame 105 is fitted into the
key groove 101a in the fixing frame 101 and thus prohibited from rotating.
Consequently, the rectilinear moving frame 105 moves rectilinearly in the
direction of the optical axis as the rotative moving cylinder 103 moves.
Further, the second lens group 220 is held by a second lens group holding
frame 222. A cam pin 226 fixed to the second lens group holding frame 222
projects into the cam groove in the rotative moving cylinder 103 and into
a key groove 105a in the rectilinear moving frame 105 which extends in the
direction of the optical axis. Accordingly, as the rotative moving
cylinder 103 moves rotatively in the direction of the optical axis in
unison with the rotation of the driving cylinder 102, the second lens
group holding frame 222 and the second lens group 220, held by the second
lens group holding frame 222, are rectilinearly moved in the direction of
the optical axis in accordance with the shape of the cam groove in the
rotative moving cylinder 103, into which the cam pin 226 is fitted.
Further, the lens shutter 300 is attached to the second lens group holding
frame 222 so as to be urged forward by a coil spring (not shown). Thus,
the lens shutter 300 is also moved in the direction of the optical axis
together with the second lens group 220.
Furthermore, the lens barrel 100 is provided with a rectilinear moving
cylinder 106, which holds the first lens group 210. A cam pin 107 fixed to
the rectilinear moving frame 106 projects into the cam groove in the
rotative moving cylinder 103 and into the key groove 105a in the
rectilinear moving frame 105, which extends in the direction of the
optical axis. Accordingly, as the rotative moving cylinder 103 moves
rotatively in the direction of the optical axis in unison with the
rotation of the driving cylinder 102, the rectilinear moving cylinder 106
is rectilinearly moved in the direction of the optical axis in accordance
with the shape of the cam groove in the rotative moving cylinder 103, into
which the cam pin 107 is fitted.
The lens barrel 100 is extended as described above and is collapsed by
rotating the driving cylinder 102 in the opposite direction.
In the third lens group 230 of the image taking lens 200, a lead screw 234
is rotated by a driving source (not shown) and is screwed into a nut 233
integrally held by the third lens group holding frame 232, which also
holds the third lend group 230. Accordingly, as the lead screw 234
rotates, the third lens group 230 is moved in the direction of the optical
axis to adjust the focus.
In this case, the first lens,holding member 212, fixed to the rectilinear
moving cylinder 106, is provided with a lens barrier 2121, a ring 2122,
and a ring rotative-moving lever 2123, described later.
Further, the second lens group holding member 222 is provided with a
projection 2221. The projection 2221 is connected by a spring 500 to the
ring rotative-moving lever 2123, provided on the first lens group holding
member 212.
The lens barrier 2121 is composed of two generally L-shaped plate pieces.
In FIGS. 3 and 4, the plate pieces of the lens barrier 2121 move down and
up, respectively, to the center of the first lens group to protect the
first lens group. In these figures, the plate pieces of the lens barrier
2121 move up and down, respectively, to their original positions to expose
the first lens group.
Then with reference to FIG. 5 description will be given of an opening and
closing operations of the lens barrier.
FIG. 5 is a schematic view showing a configuration of a lens barrier
opening and closing mechanism provided in the lens barrel.
FIG. 5 shows the lens barrier 2121, composed of the two plate pieces 2121a
and a torsion spring 2121e that urges the plate pieces 2121a in a
direction in which the barrier is closed, the ring 2122, through which a
part of the plate piece is inserted, the ring rotative-moving lever 2123,
used to move the ring rotatively, the spring 500, and the projection 2221,
provided on the second lens group holding frame 222, in this order from
the top to bottom of this figure.
The two plate pieces of the lens barrier 2121 move in the direction of an
arrow B as described above and are thus superimposed on each other to
protect the lenses. The two plates superimposed on each other at the
center of the lenses move back in the direction of an arrow A to expose
the lenses.
The plate piece 2121a is provided with a rotating shaft 2121b supported on
a part of the first lens group holding member 212, a guide projection
2121d inserted into a guide slot 2122a formed in the ring 2122, and a
spring receiving projection 2121c that receives from the torsion spring
2121e an urging force for moving the plate piece in the direction of the
arrow B. That is, the torsion spring 2121e urges the lens barrier 2121 so
as to move it in the direction in which it is closed.
The ring 2122 is formed with the two guide slots 2122a, into which the
respective guide projections 2121d, provided on the respective plates
2121a, constituting the lens barrier 2121, are inserted, as described. The
ring 2122 is also formed with a lever slot 2122b into which an end 2123a
of the L-shaped ring rotative-moving lever 2123 is inserted.
Since the end 2123a of the ring rotative-moving lever 2123 is inserted into
the lever slot 2122b, when the spring 500, connected to the second lens
group holding frame 222, urges the ring rotative-moving lever 2123 toward
the second lens group holding frame, the ring rotative-moving lever 2123
is rotatively moved in the direction of an arrow C around a rotating shaft
2123c supported on a part of the first lens group holding frame 212. Thus,
the ring 2122 is rotatively moved in the direction of an arrow E. When the
ring 2122 is moved in this way, the guide projection 2121d, inserted into
the guide slot 2122a of the ring, moves together with the ring. The two
plate pieces are thus rotatively moved in the direction of the arrow A,
i.e. the lens barrier is opened.
At this time, the urging force of the spring 500, which connects the ring
rotative-moving lever 2123, provided in the first lens group holding frame
212, and the second lens group holding frame together causes the cam pin
107 of the rectilinear moving cylinder 106, to which the first lens group
holding frame 212 is fixed, to move closer to the cam pin 226, fixed to
the second lens group holding frame 222. These cam pins are biased in the
grooves into which they are fitted, i.e. the camera is prevented from
shaking. The ring rotative-moving lever 2123 can be rotatively moved until
the end 2123a points in the direction of the optical axis.
On the other hand, when the lens barrel 100 has moved beyond the barrier
open position shown in FIG. 2 and approaches the collapsed position shown
in FIG. 1, the first lens group holding frame 212 approaches the second
lens group holding frame 222. Then, the projection 2221, provided on the
second lens group holding frame, pushes the other end 2123b of the ring
rotative-moving lever 2123. The ring rotative-moving lever 2123 is thus
rotatively moved in the direction of an arrow D. In unison with this
movement, the ring is rotatively moved in the direction of an arrow F. The
lens barrier is thus moved in the direction in which it is closed.
FIG. 6 shows that the ring is being rotatively moved by the ring
rotative-moving lever.
Part (a) of FIG. 6 shows the positional relationship between the ring 2122
and the ring rotative-moving lever 2123 observed if the lens barrel 100 is
moved to its extended position in which the lens barrier is opened. The
ring 2122 has been rotatively moved in the direction of the arrow E in
unison with the movement, in the direction of the arrow C, shown in FIG.
5, of the end 2123a of the ring rotative-moving lever inserted into the
lever slot 2122b. In this state, the guide projection 2121c inserted into
the guide slot 2122a has been moved by the ring 2122 in the direction of
the arrow E against the urging force of the torsion spring 2121e. In this
case, the lens barrier is open.
Part (b) of FIG. 6 shows the positional relationship between the ring 2122
and the ring rotative-moving lever 2123 observed if the lens barrel 100 is
moved to its collapsed position in which the lens barrier is closed. The
ring 2122 has been rotatively moved in the direction of the arrow F in
unison with the movement, in the direction of the arrow D, shown in FIG.
5, of the end 2123a of the ring rotative-moving lever inserted into the
lever slot 2122b. In this state, the guide projection 2121c inserted into
the guide slot 2122a is returned by the ring to the position shown by a
dotted circle. Subsequently, the guide projection 2121c is returned by the
urging force of the torsion spring 2121e, shown in FIG. 5, to the position
shown by a solid circle. Thus, the lens barrier is completely closed.
Compared to the direct complete closure of the lens barrier by the ring,
the above operation obviates the need to exert an excessive force on the
lens barrier owing to positional errors.
FIG. 7 is a conceptual drawing showing operations of the above lens barrier
opening and closing mechanism.
FIG. 7 shows a mechanism that is actually different from but conceptually
the same as the lens barrier opening and closing mechanism in the camera 1
according to the present embodiment. The upper part of each one of parts
(a) to (c) is a schematic view representative of the first lens group
holding frame 212. The lower part of each one of parts (a) to (c) is a
schematic view representative of the second lens group holding frame 222.
Among members constituting the lens barrier opening and closing mechanism
shown in FIG. 7, the members having the same functions as those shown in
FIG. 5 are denoted by the same reference numerals as those shown in FIG.
5.
Part (a) of FIG. 7 shows the state of the lens barrier opening and closing
mechanism in which the lens barrel is collapsed as shown in FIG. 1. Part
(b) of FIG. 7 shows the state of the lens barrier opening and closing
mechanism in which the lens barrel is extended as shown in FIG. 2. Part
(c) of FIG. 7 shows the state of the lens barrier opening and closing
mechanism in which the lens barrel is maximally extended as shown in FIG.
4.
In the collapsed position shown in part (a) of FIG. 7, the ring
rotative-moving lever 2123 is pushed by the projection 2221, provided on
the second lens group holding member 222. The ring rotative-moving lever
2123 is thus rotatively moved around the shaft 2123c in the direction in
which the force for opening the lens barrier 2121a is weakened. Thus, the
torsion spring 2121e, connected to the lens barrier, exerts an urging
force for moving the lens barrier in the closing direction and surpassing
the above weakened force.
When the lens barrel is extended from its collapsed position to its
position slightly in front of the camera, e.g. from the state shown in
part (a) of FIG. 7 to the state shown in part (b) of FIG. 7, the ring
rotative-moving lever 2123 is released from the pressure exerted by the
projection 2221. The ring rotative-moving lever 2123 is then rotatively
moved around the shaft 2123b to open the lens barrier. This is because the
force of the spring 500 which urges the ring rotative-moving lever 2123
toward the second lens group holding member surpasses the urging force of
the torsion spring 2121e.
If the lens barrel is maximally extended as shown in the state in part (c)
of FIG. 7, to which the state in part (b) of FIG. 7 has shifted, the
urging force of the torsion spring 2121e is still surpassed by the force
of the spring 500 which urges the lens rotative-moving lever 2123 toward
the second lens group holding member.
As described above, in the present embodiment, the shared mechanism is used
to achieve the lens barrier opening and closing mechanism and the
mechanism compensating backlash occurring between the first lens group
holding frame and the second lens group holding frame. Accordingly,
compared to the independent provision of the respective mechanisms, the
present embodiment simplifies the mechanisms of the camera. Therefore, the
present invention contributes to reducing the size of the camera.
In the example of the present embodiment, the camera is provided with the
projection that contacts with and pushes the lens barrier. However, the
present invention is not limited to this aspect.
Further, in the description of the present embodiment, the image taking
lens is composed of the three lens groups. However, the present invention
is applicable to image taking lenses composed of more or less lens groups,
e.g. two or four lens groups.
Furthermore, in the description of the example of the present embodiment,
the zoom lens is used as the image taking lens. However, the present
invention does not require the image taking lens to be a zoom lens but is
applicable to, for example, cameras which enables the lens barrel to be
freely collapsed and extended and which maintains, for example, a fixed
focus length in the extended state. In the example described in the
present embodiment, the spring is employed as an elastic member. However,
the present invention is not limited to this aspect.
Further, in connection with the lens shutter, the present embodiment has
not referred to the relationship between a shutter blade and a diaphragm.
However, in this lens shutter, the shutter blade may also be used as the
diaphragm blade or the diaphragm may be provided separately from the
shutter blade.
Moreover, in the description of the present embodiment, the electronic
camera having the CCD image taking element has been taken by way of
example. However, the application of the present invention is not limited
to electronic cameras. The present invention can be applied to cameras
that take photographs on silver films by providing them with a light
blocking lens barrier, a front cover, or the like.
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