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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image blur prevention apparatus for
preventing image blur which is caused due to camera movement.
2. Related Background Art
There have been proposed a number of apparatuses which are intended to
prevent failures in photography due to camera movement by detecting a
vibration due to camera movement, displacing a correction lens in response
to the detected value and correcting a variation of an optical axis of an
image. More specifically, these apparatuses are arranged so that the
vibration is detected by a vibration sensor such as an angular
acceleration meter or an angular velocity, an angular displacement is
electrically or mechanically calculated in accordance with a signal from
the vibration sensor, and the correction lens is driven in accordance with
this angular displacement information.
Methods of correction by the correction lens include parallel shifting or
tilting of the optical axis for some of the photographic lenses, or a
combination of parallel shifting and tilting of the optical axis and
provision of a variable angle prism (VAP) in a front part of a
photographic optical system.
The following particularly describes the method of shifting some of the
photographic lenses. This method is adapted so that a correction lens
frame is held to be freely slidable either in a pitch direction or in a
yaw direction at right angles to the optical axis for a circuit base
member by holding a coupling member on the circuit base member of an image
blur correcting unit to be movable in a direction (for example, the pitch
direction) at right angles to the optical axis for photography and holding
the correction lens frame on which the correction lens is mounted on the
coupling member to be movable in a direction (for example, the yaw
direction) at right angles to the optical axis.
As an actuator for driving the correction lens, a voice coil is fixed to
the correction lens frame respectively in the pitch and yaw directions at
right angles to the photographic optical axis, and a pair of a yoke and a
magnet corresponding to these voice coils are fixed to the circuit base
member.
For detecting a shifted position of the correction lens in the pitch and
yaw directions, respectively, a light emitting device (or a light
receiving device) is held on the correction lens frame and the light
receiving device (or the light emitting device) corresponding to the light
emitting device is held on the circuit base member to detect the position
of the correction lens in response to a quantity of received light from
the light emitting device whereby the correction lens is accurately driven
and controlled according to this positional information.
In an electrical wiring for the above, a printed circuit board provided
with a control circuit for driving and controlling the correction lens is
mounted on the circuit base member, an IRED which moves for the circuit
base member and the coil serving as the actuator are wired with thin
conductors between electrical components and the printed circuit board,
and the lengths of conductors are determined with an allowance enough to
meet the maximum extent of movement of the correction lens frame, thereby
ensuring stable electrical connection for relative movement of the
components. In addition, instead of a plurality of conductors, the
apparatus is arranged so that electrical connection is made with a
U-curved flexible printed circuit board.
In the above conventional example, however, the printed circuit board
mounted on the circuit base member and the electrical components such as
the IRED and coils, which are relatively moved, have been connected with
conductors and therefore the number of man-hours for assemblies such as
soldering work and costs have increased. The number of conductors has also
increased with variations in their properties and therefore a possibility
of breakage of these conductors during assembly would be higher. In
addition, it has been troublesome to repair individual conductors.
Wiring with the flexible printed board has been disadvantageous in that the
width of the overall pattern of the curved part of the board is
excessively large if the wiring patterns are arranged in one assembly, an
energizing force by curving the flexible printed circuit board is strong
to impede the movement of the correction lens frame and the driving force
is changed by a curving direction of the printed board and adversely
affect the control as a whole.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical apparatus
comprising an optical unit which can be moved in at least two different
directions; a circuit base member; and a connection member which connects
the optical unit and the circuit base member and has a deformation
characteristic which differs with the direction, the connection member
being adapted to ensure connection so that a driving force for movement of
the optical unit is not changed depending on the direction of movement of
the optical unit.
The above arrangement is effective to prevent variations of the driving
force in accordance with the driving direction of the movable optical unit
and occurrence of noises from the currents by separately connecting a
plurality of conductors to a plurality of connecting members, for example,
for a plurality of connections.
In addition, another aspect of the invention is to provide an optical
apparatus comprising an optical unit which is movable in at least two
different directions; a circuit base member; and at least two connection
members which connect said optical unit and said circuit base member and
respectively have a deformation characteristic which differs with the
direction.
The above arrangement is effective to prevent variations of the driving
force in accordance with the driving direction of the movable optical unit
and occurrence of noises from the currents by separately connecting a
plurality of conductors to a plurality of connecting members, for example,
for a plurality of connections.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a lens body tube provided with an image blur
correction apparatus which is an embodiment of the present invention;
FIG. 2 is a disassembled perspective view of an image blur correction unit
of the image blur correction apparatus which is an embodiment of the
present invention;
FIG. 3 is a perspective view illustrating a structure of a flexible printed
circuit board shown in FIG. 2; and
FIG. 4 is a side view of a principal part illustrating a lock mechanism of
a correction optical system shown in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of the invention are described below, referring
to the accompanying drawings whereof:
In the embodiments described below, an image blur is detected by detecting
a vibration of a camera.
FIGS. 1 and 2 relate to an embodiment of the invention; FIG. 1 is a
sectional view of a lens body tube provided with a zooming function in
which an image blur correction apparatus is incorporated and FIG. 2 is a
disassembled perspective view of the image blur correction unit.
In FIG. 1, A to D respectively denote optical lenses (B is a correction
lens) which are secured in a first group body tube 1, a lens hold ring 201
which is a component of the image blur correction unit 2 described later,
a third group body tube 3 and a fourth group body tube 4.
Numeral 5 is an external tube in which a mount 6 to be fixed to a camera
body, not shown, is secured, numeral 7 denotes a fixed tube which is
secured with a screw to the external tube 5 and numeral 8 is a zoom cam
tube which is rotatably held with a zoom operating ring 9 around an
optical axis.
A key 1a is fitted to the first group body tube 1 and engaged with a cam
groove 8a of the zoom cam tube 8 and a straight groove 7a of the fixed
tube 7. A roller 203 of the image blur correction unit 2 is fixed to a
circuit base member 202 and engaged with a cam groove 8b of the zoom cam
tube 8 and a straight groove 7b of the fixed tube 7. Accordingly, the zoom
cam tube 8 is rotated by rotating the zoom operating ring 9 and the first
group body tube 1 and the image blur correction unit 2 are moved in the
optical axis direction by a known cam mechanism. FIG. 1 shows a wide state
and operation to the TELE side causes the first group body tube to advance
and the image blur correction unit 2 to retract.
Numerals 10 denote a focus cam tube which is rotated along the internal
periphery of the fixed tube 7 and movably held in the optical axis
direction and, when a zoom key 8c fixed to the zoom cam 8 is engaged with
the straight groove 10a and a pin 7c arranged on the fixed tube 7 is
engaged with a cam groove 10b, the focus cam tube moves in the optical
axis direction while rotating along with rotation of the zoom cam 8.
The third group body tube 3 has a roller 3a, which is engaged with a
straight groove 11a of a focus drive tube 11 which is rotatably held at
the fixed position on the external peripheries of the cam groove 10c and
the fixed tube 7 of the focus cam tube 10. The focus drive tube 11 has a
gear 11b at its rear part and is rotated by a rotating force of a motor 12
transmitted to the gear 11b through a reduction gear train 13, whereby the
third group body tube 3 moves in the optical axis direction and the focus
is adjusted.
The fourth group body tube 4 has a known diaphragm unit 14 at its front end
part and is fixed to the fixed tube 7.
15 is a printed circuit board on which electrical components are arranged
and which controls focal adjustment, driving of the diaphragm and the
image blur correction unit 2 by the signals from the camera body. 16 is a
battery case which is fixed with a screw to the rear part of the fixed
tube 7 to hold the battery described later and provided with contact
fixtures 16a and 16b from which conductors (not shown) are connected to an
image blur prevention circuit of the printed circuit board 15. 17 is a
battery to be used as a power supply for controlling and driving the image
blur correction unit 2 and, in this embodiment, two cylindrical lithium
cells are arranged so that two electrodes are positioned in parallel to
the optical axis. 18 is a battery cover which prevents the battery 17 from
coming off from the battery case 16 to supply a stable power and held to
be movable in the optical direction.
For mounting the battery, the battery 17 is pushed in the battery case 16
through an opening 5a of an external tube 5. Accordingly, the battery 17
is temporarily fixed by the energizing force of the contact fixture 16a.
Subsequently, the battery cover 18 is fitted to the opening 5a of the
external tube 5 from the rear side and slid to the front side. Then a hook
18a provided on the battery cover 18 engages with a groove 5b provided on
the internal periphery of the external tube 5 to secure the battery cover
18. For replacing the battery 17, the battery cover 18 is slid to the rear
while pressing the front external peripheral part 18b. With this
operation, the hook 18a is disengaged from the groove 5b of the external
tube 5 and the battery cover 18 can be removed to permit replacement of
the battery 17.
19 is a switch for changing over whether correction of the image blur
should be carried out and, when this switch 19 is ON, the image blur
correction unit 2 can be driven and controlled according to the
communications information with the camera body. 20 is a vibration sensor
for detecting an unintentional vibration of a camera such as an
unintentional joggle of hands in photography and, in this embodiment, a
vibration gyro for detecting the angular velocity is presumed.
The above vibration sensor 20 is each provided on the upper side and the
lateral side of the external peripheral part near the mount of the fixed
tube 7 so that a rotary vibration of the camera in the vertical direction
(pitch direction) and in the horizontal direction (yaw direction) can be
detected. These vibration sensors 20 are connected with wires to the image
blur prevention circuit of the printed circuit board and the outputs of
these vibration sensors are converted to an angular displacement by the
image blur prevention circuit. In addition, an amount of shift of the
correction lens is calculated by adding a focal distance information and a
distance-to-subject information and used for drive control.
21 is a battery cover fitting detection switch which is attached to the
fixed tube 7 and arranged so that, when the battery cover 18 is mounted,
its hook 18a makes a flap 21a contact with another flap 21b, that is,
turns on.
The image blur correction unit 2 is described below, referring to FIG. 2.
In FIG. 2, 202 is the base member of the image blur correction unit 2 and
provided with rollers 203 each of which is fixed at each of three
equally-spaced positions. When this roller 203 engages with the cam groove
8b of the zoom cam tube 8 and the straight groove 7b of the fixed tube 7,
the image blur correction unit 2 as a whole is moved in the optical axis
direction by the zooming operation described above. 204 is a coupling arm
which is supported to be movable in the horizontal direction (hereinafter
referred to as the "X direction") in reference to a pin 205a and a pin
205b is fixed in the vertical direction (hereinafter referred to as the "Y
direction") and a shifting frame 206 is held to be movable in the Y
direction in reference to the pin 205b.
The shifting frame 206 is held to be movable both in the X and Y directions
in reference to the base member 202. In addition, a guide plate 207 is
fixed to the base member 202 so that the shifting frame 206 does not move
in the optical axis direction (Z direction), and the shifting frame 206 is
held by and between the guide plate 207 and the base member 202.
Voice coils 208a and 208b are fixedly bonded to the shifting frame 206 for
driving in X and Y directions. Yokes 210a and 210b on which magnets 209
are mounted at the positions corresponding to the voice coils 208a and
208b are fixed with screws to the base member 202.
Shifting position detection means of the shifting frame 206 comprises light
emitting devices IRED211a and IRED211b which are fixed with slits 212a and
212b in holes 206a and 206b of the shifting frame 206 and light receiving
devices PSD213a and PSD213b which are fixed to the base member 202.
214 is a flexible printed circuit board which is fitted to the rear side of
the base member 202 and provided with a circuit pattern and electrical
components which form part of the image blur prevention circuit. It is
also provided with a pair of extension lugs 214a and 214b which are bent
to the front side a U-shape. The coil 208a attached to the shifting frame
206 and the terminal of the IRED211a are inserted into and soldered to the
holes of the extension lug 214(a), and the coil 208b and the terminal of
the IRED211b are similarly soldered to the extension lug 214b. Extension
lugs 214a and 214b are drawn out from approximately opposing positions of
a doughnut-shaped mounting part. The bending directions of the U-bent
portions of the extension lugs are X and Y directions which are arranged
to be at right angles to each other. This is intended to uniformly apply a
recovery force produced by bending the extension lugs 214a and 214b to the
shifting frame 206 in X and Y directions.
The extension lug 214a is described in detail below referring to FIG. 3.
When the shifting frame 206 is shifted in the X direction, the connecting
parts of the coil 208a at the end and the IRED211a (these components are
not shown in FIG. 3) are moved in parallel so that the curvatures of bent
portions 51 and 52 are changed. In the present embodiment, a reinforcing
pattern portion (between bent portions 51 and 52) is provided at the
middle part of the extension lug 241(a) and the extension lug 214a is bent
mainly at two positions to minimize the space required. However, if there
is available a sufficient space, the extension lug can be bent at a
position to have a large U-shaped curve.
The recovery force of the extension part 214a with a structure as shown in
FIG. 3 is small and acts mainly in the optical axis direction (Z
direction). Accordingly, it has a less effect in the shifting direction
and rather deviates a play of components which are mounted in layers to
the optical axis direction, thus preventing movement of the part due to
such play.
The extension lug 214a is provided with a mounting part as a base, and
slits 53 and 54 to permit bending in a direction at right angles to the
U-shaped bent portions 51 and 52. In other words, when the shifting frame
206 is moved in the Y direction, the bent portions 51 and 52 do not change
and bent portions 55 and 56 shown with broken lines in FIG. 3 are bent to
permit the end part of the extension lug 214a to be movable in parallel.
Bent portions 55 and 56 are not be bent and maintain flatness when the
correction lens B is not shifted. The bent portions 55 and 56 are bent to
provide a recovery force by shifting the correction lens B. This recovery
force acts in a direction where the correction lens is moved toward the
center. If the image blur is corrected in normal photography, a large
amount of power is consumed to prevent shifting of the correction lens B
due to its own weight and therefore such power consumption can be
substantially reduced by energizing the correction lens B toward the
center with this recovery force.
The above paragraphs have described the extension lug 214a. This is similar
to the extension lug 214b when the bending directions are deviated by 90
degrees. In other words, the effects of the recovery forces of the bent
portions which act on the shifting frame 206 are made equal both in X and
Y directions by arranging two extension lugs 214a and 214b at
approximately right angles. Since wiring is divided for two extension lugs
214a and 214b, a clearance between wires is increased to be more effective
in reduction of adverse effect of noise.
The flexible printed circuit board 214 has a pull-out part 214c which is
bent backwardly and guided by a support member 215 to the rear of the
unit. The pull-out part 214c is formed in such a manner that the pull-out
part 214c is folded once to the front side at the end of the support
member 215, bent again in the U-shape and extended backwardly (refer to
FIG. 1). The rear end of the pull-out part 214c is electrically connected
to the printed circuit board 15 to communicate with the image blur
prevention circuit. The image blur correction unit 2 is moved in the
optical axis direction by the zooming operation and, in this case, the
bent portion 214d to allow stable signal communications.
The following describes a lock mechanism of the correction optical system
(correction lens B and others) when image blur correction is not carried
out, referring to FIGS. 2 and 4.
216 is a lock lever which is fitted with a step screw 217 to the base
member and supported to be turnable around the axis of the step screw 217
as the pivot. 218 is a plunger which is internally provided with a
solenoid, fixed to the base member 202 and electrically connected to the
flexible printed circuit board 214. 219 is a coil spring which is held by
the base member 202 to energize the lock lever 216 in a direction where it
is kept away from the plunger 218.
When a power is supplied to the plunger 218, a step portion of an actuating
shaft 218a is engaged with the groove 216a of the lock lever 216 and
therefore the lock lever 216 is attracted against the energizing force,
and stabilized by an internal magnet. Therefore, even if the power supply
is disconnected, it maintains the stable state. At this time, the shifting
frame 206 is driven toward the center, a projection 216b of the lock lever
216 enters into the hole 206c of the shifting frame 206, and the shifting
frame 206 is locked at the central position.
If a power is reversely supplied to the plunger 218, the plunger 218 is
released from the stable state, the projection 216 of the lock lever 216
is disengaged from the hole 206c of the shifting frame 206 by the
energizing force of the coil spring 219, and the shifting frame 206 is
ready for shifting.
For assembly of the image blur correction unit 2, the lens hold ring 201
which holds the correction lens B is assembled after the printed circuit
board 214 has been arranged and coils 208a, 208b, IRED211a, IRED211b,
PSD213a and PSD213b and the plunger 218 have been connected with wires.
This procedure is necessary to prevent a damage and stain due to oil
splashes of the correction lens B during assembly. In addition, such
procedure is intended to reuse the correction lens B which is expensive
and will require a lot of man-hours in manufacturing even though the image
blur correction unit 2 is checked as defective.
In the present embodiment, one lens unit is made up by mounting and
securing the correction lens B comprising a plurality of lens in the lens
hold ring 201 and fixed by passing through the opening 214e provided in
the flexible printed circuit board 214 and the opening 202a provided in
the base member 206 and meshing the threaded part 201c to the threaded
part 206d of the shifting frame 206. In this case, the lens hold ring 201
is provided with a fitting surface 201a (which abuts with the opening
202e) to prevent deviation of the optical axis for the shifting frame 206
and a body fitting surface 201b.
220 is a shield plate which is provided with light shielding lines on its
front side and installed on an image blur correction unit 2 which has been
determined satisfactory in the functional inspection after the assembly
process. The shield plate serves to prevent a stray light to coils 208a
and 208b in detection of the amount of shift of the correction lens B and
limit the effective light flux incident from the front side of the lens
body tube.
Operation of the image blur correction apparatus is described below.
The lens body tube is mounted on the camera body and the main switch of the
camera body is set to ON. When the image blur correction start switch 19
of the lens body tube is set to ON, the power is supplied from the battery
17 to the control circuit. Image blur correcting operation is carried out
in conjunction with the release button of the camera. When the release
button is half-pressed, the lock mechanism is released by the plunger 218,
the correction lens B is shifted in response to the output of the
vibration sensor 20 and the image blur correction is carried out. When the
release button is further pressed, a film is exposed as known and, after
the exposure, the correction lens B is driven to the central position and
locked again by the plunger 218 and the image blur correction is stopped.
When the release button is released from the half-pressed state, the
correction lens B is similarly locked after lapse of a specified time and
the image blur correction can be stopped. When the switch 19 is turned
off, the correction lens B is locked and the image blur correction is
stopped.
The power of the battery 17 gradually diminishes as the image blur
correction is repeated. In the present invention, when the power level of
the battery 17 is detected by the image blur prevention control circuit on
the printed circuit board 15 and it is determined that the correction lens
B cannot be driven, the correction lens B is locked at the central
position (where the optical axis for photography is aligned with the
optical axis of the correction lens B) to prohibit the correcting
operation.
When the battery cover fitting detection switch 21 detects that the battery
cover 18 is removed, the image blur prevention control circuit locks the
correction lens at the central position and prohibits the correcting
operation.
In addition, when the battery cover fitting detection switch 21 detects
that the battery cover 18 is removed, the image blur prevention control
circuit immediately prohibits the image blur correcting operation and
locks the correction lens B at the central position even though the image
blur correction start switch 19 is kept on and the image blur correcting
operation is being carried out according to the release signal of the
camera. This prevents the correction lens B from remaining unlocked and
being to be freely shiftable to cause a play in the image blur correction
unit when the power supply is suddenly turned off during the correcting
operation. In addition, it is intended to detect (from the state of the
battery cover fitting detection switch 21) that the battery cover 18 is
opened as a prestage for removing the battery 17 and lock the correction
lens B at the central position wile the battery is not removed owing to
the energizing force of the contact fixture 16a and the power is still
supplied.
Thus the image blur prevention control circuit enables to prevent the
correction lens B from being locked at the central position, uncomfortable
noise due to a play of the lens unit and the correction lens B and the
image blur correction unit 2 from being damaged even when the photographer
inadvertently tries to replace the battery during the correcting
operation.
As described above, the image blur prevention apparatus according to the
above-described embodiment has at least a pair of extension parts, which
respectively have U-shaped bent portions which are bent along with
movement of the shifting member and are provided with conductive patterns
for transmitting and receiving information between electrical components
and the control circuit part, the pair of extension parts being arranged
so that the bending directions of respective bent portions are
approximately at right angles to each other, and provided with a flexible
printed circuit board the end part of which is connected to the
above-described electrical components wherein connection between the
control circuit part on the printed circuit board and electrical
components which are moved together with the shifting member is made with
the conductive pattern and not with lead wires and the energizing force
obtained from bending of a pair of extension parts may be uniformly
applied even though the unit moved in any direction which orthogonally
intersects the optical axis of the optical apparatus.
Accordingly, the number of man-hours for assembly can be substantially
reduced and a change of the driving force depending on the shifting
direction of the shifting member can be prevented.
According to the above-described embodiment, a pair of extension parts are
formed in a shape extended from an opposing position in reference to the
optical axis of the optical apparatus, the energizing force in th optical
axis direction which acts on the shifting member in accordance with
bending of the extension parts is made uniform and electrical wiring is
divided into a plurality of divisions to increase the clearance between
wires.
An adverse effects to the shifting member due to bending of the extension
parts can be prevented and an adverse effect due to noise can be reduced.
Similarly according to the above embodiment, the extension parts are
respectively provided with a first bent portion which is bent in the U
shape and a second bent portion which is bent in a different direction
from the bending direction of the first bent portion when the shifting
member is moved from the specified position (central position) so that the
energizing force of the bent portions always acts in a direction where the
shifting member is forced to move to the specified position.
Therefore the shifting member can be prevented from dropping due to its own
weight and current consumption for holding the shifting member at the
specified position can be reduced.
The light beam deflection apparatus is not limited to installation within
the lens unit and can also be provided in other equipment such as cameras,
video units or the like.
The image blur prevention means according to the present invention is not
limited to optical members which are moved in a plane and can have optical
members which rotate around the specified axis or those such as a variable
angle prism which move in other ways of movement.
Driving means for driving the optical members is not limited to a drive
unit having voice coils and magnets and other driving means such as motors
and stepping motors can be used.
The light beam deflection apparatus is not limited to the object of image
blur prevention and can be used for other objects, for example, tracking
and dynamic focusing and further intentional soft focusing and the like.
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