Imaging device having an optical image stabilizer

An imaging device includes an imaging sensor having an imaging surface upon which an object image is formed via a photographing optical system; a guiding device for guiding the imaging sensor in a direction parallel to the imaging surface of the imaging sensor; and a driving device for driving the imaging sensor, while being guided by the guiding device, based on an output of an image-shake detector which detects a direction and magnitude of an amount of vibration applied to the photographing optical system. One and the other of the guiding device and the driving device are respectively provided in front of and behind an image-stabilizing plane, which is coincident with the imaging surface of the imaging sensor, with respect to an optical axis direction of the photographing optical system.

This application claims foreign priority under 35 U.S.C. 119(a-d) based on Japanese Patent applications No. 2004-349184, filed Dec. 1, 2004, and No. 2005-56292, filed Mar. 1, 2005, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging device, and more specifically, relates to an imaging device having an optical image stabilizer which performs an image-stabilizing operation by driving an imaging sensor (CCD) so as to counteract image shake due to vibrations such as hand shake (camera shake).

2. Description of the Related Art

In image devices such as cameras which have image stabilizers for correcting camera shake (image shake), when vibrations such as hand shake are applied to the camera body, are well known in the art. For example, in a digital camera which uses an imaging sensor such as a CCD or CMOS as an imaging medium, image-stabilization is carried out by moving the imaging sensor along a plane (in a direction parallel to the imaging surface of the imaging sensor) which lies orthogonal to the incident optical axis of the imaging sensor in accordance with angular velocity data of the detected camera shake.

Since the positional error due to tilting, caused by camera shake, etc., of the imaging sensor has a large adverse influence on the picture quality, when the imaging sensor is driven in order to correct image-shake, a significantly high driving precision is required. Primary causes of adverse influence on the driving precision are clearance, which exists in the guide shaft portions for guiding the imaging sensor, and backlash which occurs within the driving-force transmission mechanism for transferring driving force from a driving device such as a motor.

SUMMARY OF THE INVENTION

The present invention provides a compact imaging device having an optical image stabilizer which can carry out image-stabilization by driving an imaging sensor with high precision, and can be provided at low cost.

According to aspect of the present invention, an imaging device is provided, including an imaging sensor having an imaging surface upon which an object image is formed via a photographing optical system; a guiding device for guiding the imaging sensor in a direction parallel to the imaging surface of the imaging sensor; and a driving device for driving the imaging sensor, while being guided by the guiding device, based on an output of an image-shake detector which detects a direction and magnitude of an amount of vibration applied to the photographing optical system. One and the other of the guiding device and the driving device are respectively provided in front of and behind an image-stabilizing plane, which is coincident with the imaging surface of the imaging sensor, with respect to an optical axis direction of the photographing optical system.

It is desirable for the driving device to be provided in front of the image-stabilizing plane, and the guiding device to be provided behind the image-stabilizing plane, which respect to the optical axis direction.

It is desirable for the guiding device and the driving device to be a first guiding device and a first driving device for linearly moving the imaging sensor along the image-stabilizing plane in a first direction, and a second guiding device and a second driving device for linearly moving the imaging sensor along the image-stabilizing plane in a second direction.

It is desirable for the guiding device to be provided so as to extend in a direction parallel to the image-stabilizing plane, wherein the guiding device includes a linear guide shaft which is slidably fitted through an imaging-sensor supporting member.

It is desirable for the driving device to include a motor having a rotational shaft which extends substantially parallel to the linear guide shaft, and a driving-force transmission device which converts a rotational motion of the rotational shaft of the motor into linear motion which moves in a direction parallel to the linear guide shaft, so as to apply the linear motion to the imaging-sensor supporting member.

It is desirable for the motor to include a stepping motor.

It is desirable for the driving-force transmission device to include a driven nut which is moved in the direction parallel to the linear guide shaft in accordance with rotation of the rotational shaft of the motor.

It is desirable for the driving-force transmission device to include a linearly moving member which is moved in the direction parallel to the linear guide shaft via the driven nut; and a swing member which is rotatable about a rotation axis parallel to the optical axis of the photographing optical system, the swing member pushing the imaging-sensor supporting member, which supports the image sensor, to move along the guiding direction of the linear guide shaft.

According to the above-described structure, a compact imaging device having an optical image stabilizer which can carry out image-stabilization by driving an imaging sensor with high precision, and can be provided at low cost.

The present disclosure relates to subject matter contained in Japanese Patent Application No. 2004-349184 (filed on Dec. 1, 2004), and Japanese Patent Application No. 2005-56292 (filed on Mar. 1, 2005), which are expressly incorporated herein by reference in their entireties.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2show cross-sections of a zoom lens10which is incorporated in a zoom lens camera. The zoom lens10is provided with a box-shaped housing11and a retractable barrel portion12retractably supported inside the housing11. The outside of the housing11is covered by exterior components of the camera; the exterior components are not shown in the drawings. A photographing optical system of the zoom lens10includes a first lens group13a, a shutter13b, a diaphragm13c, a second lens group13d, a third lens group13e, a low-pass filter13f, and a CCD image sensor13g(hereinafter referred to as a CCD), in that order from the object side (the left side as viewed inFIGS. 1 and 2). As shown inFIG. 5, the CCD13gis electrically connected to a control circuit14ahaving an image processing circuit. Thus, an electronic image can be displayed on an LCD monitor14bprovided on an outer surface of the camera, and the electronic image data can be recorded in a memory14c. In a photographic state (ready-to-photograph state) of the zoom lens10shown inFIG. 2, all of the optical elements constituting the photographing optical system are aligned on the same photographing optical axis Z1. On the other hand, in an accommodated (radially retracted) state of the zoom lens10shown inFIG. 1, the third lens group13e, the low-pass filter13fand the CCD13gare moved away from the photographing optical axis Z1to be radially retracted upward in the housing11, and the second lens group13dis linearly retracted into the space created as a result of the upward radial retracting movement of the third lens group13e, the low-pass filter13fand the CCD13g, which reduces the length of the zoom lens10in the retracted state thereof. The overall structure of the zoom lens10that includes a radially-retracting mechanism for radially retracting optical elements upward will be described hereinafter. In the following description, the vertical direction and the horizontal direction of the zoom lens camera body equipped with the zoom lens10as viewed from the front thereof are defined as a y-axis and an x-axis, respectively.

The housing11is provided with a hollow box-shaped portion15and a hollow fixed ring portion16which is formed on a front wall15aof the box-shaped portion15so as to enclose the photographing optical system about the photographing optical axis Z1. A rotation center axis Z0serving as the center of the fixed ring portion16is parallel to the photographing optical axis Z1and eccentrically located below the photographing optical axis Z1. A retraction space (accommodation space) SP (FIGS. 1 and 2) is formed inside the box-shaped portion15and above the fixed ring portion16.

A zoom gear17(FIGS. 8,10and11) is supported on an inner peripheral surface side of the fixed ring portion16to be rotatable on an axis of rotation parallel to the rotation center axis Z0. The zoom gear17is rotated forward and reverse by a zoom motor MZ (FIGS. 5,10, and11) supported by the housing11. In addition, the fixed ring portion16is provided on an inner peripheral surface thereof with a female helicoid16a, a circumferential groove16band a plurality of linear guide grooves16c(only one of them is shown inFIG. 8). The circumferential groove16bis an annular groove with its center on the rotation center axis Z0, while the plurality of the linear guide grooves16care parallel to the rotation center axis Z0(seeFIGS. 3,4and8).

A helicoid ring18is supported inside the fixed ring portion16to be rotatable about the rotation center axis Z0. The helicoid ring18is provided with a male helicoid18awhich is engaged with the female helicoid16aof the fixed ring portion16and thus can advance and retract in the optical axis direction while rotating due to the engagement of the female helicoid16awith the male helicoid18a. The helicoid ring18is further provided, on an outer peripheral surface thereof in front of the female helicoid18a, with a plurality of rotation guiding protrusions18b(only two of them are shown inFIG. 8). In a state shown inFIGS. 2 through 4in which the helicoid ring18advances to the frontmost position thereof with respect to the fixed ring portion16, the female helicoid16aand the male helicoid18aare disengaged from each other while the plurality of rotation guiding protrusions18bare slidably fitted in the circumferential groove16bso that the helicoid ring18is prevented from further moving in the optical axis direction and is allowed only to rotate at a fixed position in the optical axis direction. The helicoid ring18is further provided on threads of the male helicoid18awith an annular spur gear18cwhich is in mesh with the zoom gear17. Teeth of the spur gear18care aligned parallel to the photographing optical axis Z1. The zoom gear17is elongated in the axial direction thereof so as to remain engaged with the spur gear18cat all times over the entire range of movement of the helicoid ring18from a retracted state of the helicoid ring18shown inFIGS. 1 and 10to an extended state of the helicoid ring18shown inFIGS. 2 and 11. The helicoid ring18is constructed by combining two ring members which are splittable in the optical axis direction. InFIGS. 10 and 11, only the rear ring member of the helicoid ring18is shown.

A linear guide ring20is supported inside the helicoid ring18. The linear guide ring20is provided in the vicinity of the rear end thereof with a linear guide projection20a, and is guided linearly along the rotation center axis Z0(and the photographing optical axis Z1) by the slidable engagement of the linear guide projection20awith the linear guide groove16cof the fixed ring portion16as shown inFIG. 4. A rotation guiding portion21is provided between the inner peripheral surface of the helicoid ring18and the outer peripheral surface of the linear guide ring20. The helicoid ring18is supported by the linear guide ring20to be rotatable with respect to the linear guide ring20and to be movable together with the linear guide ring20in the optical axis direction via the rotation guiding portion21. The rotation guiding portion21consists of a plurality of circumferential grooves provided at different positions in the axial direction and radial protrusions, each of which is slidably engaged in the corresponding circumferential groove (seeFIGS. 3 and 4).

The linear guide ring20is provided on an inner peripheral surface thereof with a plurality of linear guide grooves20b(only one of them is shown in each ofFIGS. 1 through 4) which extend parallel to the rotation center axis Z0(and the photographing optical axis Z1). A plurality of linear guide projections22a(only one of them is shown in each ofFIGS. 1 through 4) which project radially outwards from a first lens group linear guide ring22and a plurality of linear guide projections23a(only one of them is shown in each ofFIGS. 1 through 4) which project radially outwards from a second lens group linear guide ring23are slidably engaged with the plurality of linear guide grooves20b, respectively. The first lens group linear guide ring22guides a first lens group support frame24linearly in a direction parallel to the rotation center axis Z0(and the photographing optical axis Z1) via a plurality of linear guide grooves22b(only one of them is shown in each ofFIGS. 2 and 3) formed on an inner peripheral surface of the first lens group linear guide ring22. The second lens group linear guide ring23guides a second lens group support frame25linearly in a direction parallel to the rotation center axis Z0(and the photographing optical axis Z1) via a plurality of linear guide keys23b(only one of them is shown in each ofFIGS. 1 through 4). The first lens group support frame24supports the first lens group13avia a focusing frame29, and the second lens group support frame25supports the second lens group13d.

A cam ring26is provided inside the linear guide ring20to be rotatable about the rotation center axis Z0. The cam ring26is supported by the first lens group linear guide ring22and the second lens group linear guide ring23to be rotatable with respect to each of the first lens group linear guide ring22and the second lens group linear guide ring23and to movable in the optical axis direction together therewith via rotation guiding portions27and28(seeFIG. 4). As shown inFIGS. 3 and 4, the rotation guiding portion27is composed of a discontinuous circumferential groove27a(not shown inFIG. 3) which is formed on an outer peripheral surface of the cam ring26, and an inner flange27bwhich projects radially inwards from the first lens group linear guide ring22to be slidably engaged in the discontinuous circumferential groove27a. As shown inFIGS. 3 and 4, the rotation guiding portion28is composed of a discontinuous circumferential groove28a(not shown inFIG. 3) formed on an inner peripheral surface of the cam ring26and an outer flange28bwhich projects radially outwards from the second lens group linear guide ring23to be slidably engaged in the discontinuous circumferential groove28a.

As shown inFIG. 4, the cam ring26is provided thereon with a plurality of follower protrusions26a(only one of them is shown inFIG. 4) which project radially outwards. The plurality of follower protrusions26apasses through a plurality of follower guide slots20c(only one of them is shown inFIG. 4) formed in the linear guide ring20to be engaged in a plurality of rotation transfer grooves18d(only one of them is shown inFIG. 4) formed on an inner peripheral surface of the helicoid ring18. Each rotation transfer groove18dis parallel to the rotation center axis Z0(and the photographing optical axis Z1), and each follower protrusion26ais slidably engaged in the associated rotation transfer groove18dto be prevented from moving in the circumferential direction relative to the associated rotation transfer groove18d. Accordingly, the rotation of the helicoid ring18is transferred to the cam ring26via the engagement between the plurality of rotation transfer grooves18dand the plurality of follower protrusions26a. Although the development shape of each follower guide groove20cis not shown in the drawings, each follower guide groove20cis a guide groove including a circumferential groove portion with its center on the rotation center axis Z0and an inclined lead groove portion parallel to the female helicoid16a. Accordingly, when rotated by a rotation of the helicoid ring18, the cam ring26rotates while moving forward or rearward along the rotation center axis Z0(and the photographing optical axis Z1) if each follower protrusion26ais engaged in the lead groove portion of the associated follower guide groove20c, and rotates at a fixed position in the optical axis direction without moving forward or rearward if each follower protrusion26ais engaged in the circumferential groove portion of the associated follower guide groove20c.

The cam ring26is a double-sided cam ring having a plurality of outer cam grooves26b(only one of them is shown inFIG. 3) and a plurality of inner cam grooves26c(only one of them is shown in each ofFIGS. 3 and 4) on outer and inner peripheral surfaces of the cam ring26, respectively. The plurality of outer cam grooves26bare slidably engaged with a plurality of cam followers24a(only one of them is shown inFIG. 3) which project radially inwards from the first lens group support frame24, respectively, while the plurality of inner cam grooves26care slidably engaged with a plurality of cam followers25a(only one of them is shown in each ofFIGS. 3 and 4) which project radially outwards from the second lens group support frame25. Accordingly, when the cam ring26is rotated, the first lens group support frame24that is guided linearly in the optical axis direction by the first lens group linear guide ring22moves forward and rearward along the rotation center axis Z0(and the photographing optical axis Z1) in predetermined motion in accordance with contours of the plurality of outer cam grooves26b. likewise, when the cam ring26is rotated, the second lens group support frame25that is guided linearly in the optical axis direction by the second lens group linear guide ring23moves forward and rearward along the rotation center axis Z0(and the photographing optical axis Z1) in predetermined motion in accordance with contours of the plurality of the plurality of inner cam grooves26c.

The second lens group support frame25is provided with a cylindrical portion25b(seeFIGS. 1 and 2) which holds the second lens group13d, and supports the shutter13band the diaphragm13cin front of the cylindrical portion25bto allow each of the shutter13band the diaphragm13cto be opened and closed. The shutter13band the diaphragm13ccan be opened and closed by a shutter actuator MS and a diaphragm actuator MA (seeFIG. 5), respectively, which are supported by the second lens group support frame25.

The focusing frame29which holds the first lens group13ais supported by the first lens group support frame24to be movable along the rotation center axis Z0(and the photographing optical axis Z1). The focusing frame29can be moved forward and rearward by a focusing motor MF (seeFIG. 5).

The operation of each of the zoom motor MZ, the shutter actuator MS, the diaphragm actuator MA and the focusing motor MF is controlled by the control circuit14a. Upon turning on a main switch14d(seeFIG. 5) of the camera, the zoom motor MZ is driven to bring the zoom lens10to the photographic state shown inFIG. 2. Upon turning off the main switch14d, the zoom lens10is moved from the photographic state to the retracted state shown inFIG. 1.

The above described operation of the zoom lens10is summarized as follows. Upon turning on the main switch14din the retracted state of the zoom lens10shown inFIG. 1, the zoom gear17is driven to rotate in a lens barrel advancing direction. Accordingly, the helicoid ring18moves forward in the optical axis direction while rotating, and simultaneously, the linear guide ring20linearly moves forward in the optical axis direction together with the helicoid ring18. In addition, the rotation of the helicoid ring18causes the cam ring26to move forward in the optical axis direction while rotating relative to the linear guide ring20. The first lens group linear guide ring22and the second lens group linear guide ring23linearly move forward in the optical axis direction together with the cam ring26. Each of the first lens group support frame24and the second lens group support frame25moves in the optical axis direction relative to the cam ring26in predetermined motion. Therefore, the moving amount of the first lens group13ain the optical axis direction when the zoom lens10is extended from the retracted state thereof is determined by adding the moving amount of the cam ring26relative to the fixed ring portion16to the moving amount of the first lens group support frame24relative to the cam ring26(the advancing/retracting amount of the first lens group support frame24by the cam groove26b). Furthermore, the moving amount of the second lens group13din the optical axis direction when the zoom lens10is extended from the retracted state thereof is determined by adding the moving amount of the cam ring26relative to the fixed ring portion16to the moving amount of the second lens group support frame25relative to the cam ring26(the advancing/retracting amount of the second lens group support frame25by the cam groove26c).

FIG. 6shows the moving paths of the helicoid ring18and the cam ring26and the moving paths of the first lens group13aand the second lens group13drelative to the cam ring26(the cam diagrams of the cam grooves26band26c). The vertical axis represents the amount of rotation (angular position) of the lens barrel from the retracted state of the zoom lens10to the telephoto extremity thereof, and the horizontal axis represents the amount of movement of the lens barrel in the optical axis direction. As shown inFIG. 6, the helicoid ring18is moved forward in the optical axis direction while rotating up to an angular position θ1which is located at about the midpoint in the range of extension of the zoom lens10from the retracted position (shown inFIG. 1) to the wide-angle extremity (shown by the upper half of the zoom lens10from the photographing optical axis Z1and shown inFIG. 2), whereas the helicoid ring18rotates at a fixed position in the optical axis direction as described above in the range of extension of the zoom lens10from the angular position θ1to the telephoto extremity (shown by the lower half of the zoom lens10from the photographing optical axis Z1and shown inFIG. 4). On the other hand, the cam ring26is moved forward in the optical axis direction while rotating up to an angular position θ2which is located immediately behind the wide-angle extremity of the zoom lens10in the range of extension of the zoom lens10from the retracted position to the wide-angle extremity, whereas the cam ring26rotates at a fixed position in the optical axis direction as described above in the range of extension of the zoom lens10from the angular position θ2to the telephoto extremity, similar to the helicoid ring18. In the zooming range from the wide-angle extremity to the telephoto-extremity, the moving amount of the first lens group13ain the optical axis direction is determined from the moving amount of the first lens group support frame24relative to the cam ring26which rotates at a fixed position in the optical axis direction (the advancing/retracting amount of the first lens group support frame24via the cam groove26b), while the moving amount of the second lens group13din the optical axis direction is determined from the moving amount of the second lens group support frame25relative to the cam ring26which rotates at a fixed position in the optical axis direction (the advancing/retracting amount of the second lens group support frame25via the cam groove26c). The focal length of the zoom lens10is varied by the relative movement in the optical axis direction between the first lens group13aand the second lens group13d.FIG. 7shows the actual moving path of the first lens group13awhich is obtained by combining the moving amounts of the helicoid ring18and the cam ring26with the moving amount of the first lens group13aby the cam groove26b, and the actual moving path of the second lens group13dwhich is obtained by combining the moving amounts of the helicoid ring18and the cam ring26with the moving amount by the cam groove26c.

In the zooming range from the wide-angle extremity to the telephoto extremity, a focusing operation is performed by moving the first lens group13ain the optical axis direction independently of other optical elements by the focusing motor MF.

The operations of the first lens group13aand the second lens group13dhave been described above. In the zoom lens10of the present embodiment, the optical elements of the zoom lens10from the third lens group13eto the CCD13gare retractable away from the photographing position on the photographing optical axis Z1to an off-optical-axis retracted position (radially retracted position) Z2located above the photographing position as described above. In addition, by moving the optical elements from the third lens group13eto the CCD13gon a plane perpendicular to the photographing optical axis Z1, image shake can also be counteracted. The retracting mechanism and the image stabilizing mechanism will be discussed hereinafter.

As shown inFIGS. 8 and 18, the third lens group13e, the low-pass filter13fand the CCD13gare held by a CCD holder30to be provided as a unit. The CCD holder30is provided with a holder body30a, a sealing member30band a pressure plate30c. The third lens group13eis held by the holder body30aat a front end aperture thereof. The low-pass filter13fis held between a flange formed on an inner surface of the holder body30aand the sealing member30b, and the CCD13gis held between the sealing member30band the pressure plate30c. The holder body30aand the pressure plate30care fixed to each other by three fixing screws30d(seeFIGS. 17 and 18) separately arranged around the central axis of the CCD holder30(the photographing optical axis Z1in a photographic state of the zoom lens10). The three fixing screws30dalso secure one end portion of an image transmission flexible PWB31to the rear surface of the pressure plate30cso that a supporting substrate of the CCD13gis electrically connected to the image transmission flexible PWB31.

The image transmission flexible PWB31extends from its connection end at the CCD13gto the retraction space SP in the housing11. The image transmission flexible PWB31is provided with a first linear portion31a, a U-shaped portion31b, a second linear portion31c, and a third linear portion31d(seeFIGS. 1 and 2). The first linear portion31ais substantially orthogonal to the photographing optical axis Z1and extends upward. The U-shaped portion31bis bent forward from the first linear portion31a. The second linear portion31cextends downward from the U-shaped portion31b. The third linear portion31dis folded upward from the second linear portion31c. The third linear portion31dis fixed to an inner surface of the front wall15aof the housing11therealong. The first linear portion31a, the U-shaped portion31band the second linear portion31c(except the third linear portion31d) serve as a free-deformable portion which is freely resiliently deformable according to the motion of the CCD holder30.

The CCD holder30is supported by a horizontal moving frame32via three adjusting screws33(seeFIGS. 17 and 18) separately arranged around the central axis of the CCD holder30(the photographing optical axis Z1in a ready-photograph state of the zoom lens10). Three compression coil springs34are installed between the CCD holder30and the horizontal moving frame32. The shaft portions of the three adjusting screws33are inserted into the three compression coil springs34, respectively. When the tightening amounts of the adjusting screws33are changed, the respective compression amounts of the coil springs34are changed. The adjusting screws33and the compression coil springs34are provided at three different positions around the optical axis of the third lens group13e, and accordingly, the inclination of the CCD holder30with respect to the horizontal moving frame32, or the inclination of the optical axis of the third lens group13ewith respect to the photographing optical axis Z1, can be adjusted by changing the tightening amounts of the three adjusting screws33.

As shown inFIG. 15, the horizontal moving frame32is supported by a vertical moving frame36to be movable with respect thereto via a horizontal guide shaft35extending in the x-axis direction. Specifically, the horizontal moving frame32is provided with a rectangular frame portion32awhich encloses the CCD holder30and an arm portion32bwhich extends horizontally from the frame portion32a. A spring supporting protrusion32cis formed on an upper surface of the frame portion32a, and an inclined surface32dand a position restricting surface32eare formed on an end portion of the arm portion32b. The position restricting surface32eis a flat surface parallel to the y-axis. On the other hand, the vertical moving frame36is provided with a pair of motion restricting frames36aand36b, a spring supporting portion36c, an upper bearing portion36d, and a lower bearing portion36e. The pair of motion restricting frames36aand36bare provided spaced apart in the x-axis direction. The spring supporting portion36cis located between the pair of the motion restricting frames36aand36b. The upper bearing portion36dis located on a line extended from the spring supporting portion36cin the x-axis direction. The lower bearing portion36eis located below the upper bearing portion36d. As shown inFIG. 16, the horizontal moving frame32is supported by the vertical moving frame36in a state where the frame portion32ais positioned in the space between the pair of motion restricting frames36aand36band where the inclined surface32dand the position restricting surface32eof the arm portion32bare positioned between the motion restricting frame36band the upper bearing portion36d.

One end of the horizontal guide shaft35is fixed to the motion restricting frame36aof the vertical moving frame36, and the other end of the horizontal guide shaft35is fixed to the upper bearing portion36dof the vertical moving frame36. Two through-holes are respectively formed in the motion restricting frame36band the spring supporting portion36cto be horizontally aligned to each other so as to allow the horizontal guide shaft35to pass through the motion restricting frame36band the spring supporting portion36c. Horizontal through-holes32x1and32x2(seeFIG. 16) into which the horizontal guide shaft35is inserted are formed in the arm portion32band the spring supporting protrusion32cof the horizontal moving frame32, respectively. The horizontal through-holes32x1and32x2of the horizontal moving frame32and the aforementioned two through-holes which are respectively formed in the motion restricting frame36band the spring supporting portion36care horizontally aligned with each other. Since the horizontal guide shaft35is slidably fitted in the horizontal through-holes32x1and32x2, the horizontal moving frame32is supported by the vertical moving frame36to be movable with respect to the vertical moving frame36in the x-axis direction. A horizontal moving frame biasing spring37is installed on the horizontal guide shaft35between the spring supporting protrusion32cand the spring supporting portion36c. The horizontal moving frame biasing spring37is a compression coil spring and biases the horizontal moving frame32in a direction (leftward as viewed inFIG. 16) to make the spring supporting protrusion32capproach the motion restricting frame36a.

Vertical through-holes36y1and36y2(seeFIG. 15) are further formed in the upper bearing portion36dand the lower bearing portion36eof the vertical moving frame36, respectively, which extend in a line along the y-axis direction which is orthogonal to the photographing optical axis Z1. The vertical through-hole36y1and the vertical through-hole36y2are vertically aligned, and a vertical guide shaft38(seeFIGS. 8 and 9) passes through vertical through-hole36y1and the vertical through-hole36y2. Both ends of the vertical guide shaft38are fixed to the housing11, and therefore, the vertical moving frame36can move along the vertical guide shaft38in the y-axis direction inside the camera. More specifically, the vertical moving frame36can move between the photographing position shown inFIG. 1and the retracted position shown inFIG. 2. When the vertical moving frame36is positioned in the photographing position as shown inFIG. 2, the centers of the third lens group13e, the low-pass filter13fand the CCD13gin the CCD holder30are positioned on the photographing optical axis Z1. When the vertical moving frame36is positioned in the radially retracted position as shown inFIG. 1, the centers of the third lens group13e, the low-pass filter13fand the CCD13gare positioned in the off-optical-axis retracted position Z2that is located above the fixed ring portion16.

The vertical moving frame36is provided with a spring hooking portion36fwhich projects horizontally from a side surface of the vertical moving frame36in a direction away from the vertical through-hole36y1, and a vertical moving frame biasing spring39is extended between the spring hooking portion36fand a spring hooking portion11a(seeFIG. 8) fixed to the housing11therein. The vertical moving frame biasing spring39is an extension coil spring and biases the vertical moving frame36downward (i.e., toward the photographing position thereof shown inFIG. 2).

As described above, the horizontal moving frame32that holds the CCD holder30is supported by the vertical moving frame36to be movable in the x-axis direction with respect to the vertical moving frame36, and the vertical moving frame36is supported by the housing11via the vertical guide shaft38to be movable in the y-axis direction with respect to the housing11. Image shake can be counteracted by moving the CCD holder30in the x-axis direction and the y-axis direction. To this end, the zoom lens10is provided with a driving device which achieves such movement of the CCD holder30. This driving device will be discussed hereinafter.

This driving device is provided with a horizontal driving lever40. As shown inFIGS. 9 and 19, the horizontal driving lever40is pivoted at the lower end thereof on a lever pivot shaft42which provided in the housing11and fixed thereto to be parallel to the photographing optical axis Z1. The horizontal driving lever40is provided at the upper end of the horizontal driving lever40with a force-applying end40a. The horizontal driving lever40is provided in the vicinity of the force-applying end40awith an operation pin40bwhich projects rearward in the optical axis direction and a spring hooking portion40cwhich projects forward in the optical axis direction. As shown inFIG. 12, the force-applying end40aof the horizontal driving lever40abuts against a lug43aof a moving member43. The moving member43is supported by a pair of parallel guide bars44(44aand44b) to be slidable thereon in the x-axis direction, and a driven nut member45abuts against the moving member43. The driven nut member45is provided with a female screw hole45band a rotation restricting groove45a(seeFIG. 9) which is slidably fitted on the guide bar44b. A drive shaft (a feed screw)46aof a first stepping motor46is screwed into the female screw hole45b. As shown inFIGS. 13 and 14, the driven nut member45abuts against the moving member43from the left side. One end of an extension coil spring47is hooked on the spring hooking portion40cof the horizontal driving lever40, and the other end of the spring47is hooked on a spring hooking portion11bwhich projects from an inner surface of the housing11(seeFIG. 12). The extension coil spring47biases the horizontal driving lever40in a direction to bring the moving member43to abut against the driven nut member45, i.e., in a counterclockwise direction as viewed inFIGS. 13,14and19. Due to this structure, driving the first stepping motor46causes the driven nut member45to move along the pair of guide bars44, and at the same time causes the moving member43to move together with the driven nut member45, thus causing the horizontal driving lever40to swing about the lever pivot shaft42. Specifically, moving the driven nut member45rightward as viewed inFIGS. 13 and 14causes the driven nut member45to press the moving member43in the same direction against the biasing force of the extension spring47, thus causing the horizontal driving lever40to rotate clockwise as viewed inFIGS. 13 and 14. Conversely, moving the driven nut member45leftward as viewed inFIGS. 13 and 14causes the moving member43to move in the same direction while following the leftward movement of the driven nut member45due to the biasing force of the extension coil spring47, thus causing the horizontal driving lever40to rotate counterclockwise as viewed inFIGS. 13 and 14.

As shown inFIG. 19, the operation pin40bof the horizontal driving lever40abuts against the position restricting surface32ethat is provided on the end portion of the arm portion32bof the horizontal moving frame32. Since the horizontal moving frame32is biased leftward as viewed inFIG. 19by the horizontal moving frame biasing spring37, the operation pin40bremains in contact with the position restricting surface32e. When the horizontal driving lever40swings, the position of the operation pin40bchanges along the x-axis direction, so that the horizontal moving frame32moves along the horizontal guide shaft35. Specifically, rotating the horizontal driving lever40clockwise as viewed inFIG. 19causes the operation pin40bto press the position restricting surface32e, which causes the horizontal moving frame32to move rightward as viewed inFIG. 19against the biasing force of the horizontal moving frame biasing spring37. Conversely, rotating the horizontal driving lever40counterclockwise as viewed inFIG. 19causes the operation pin40bto move in a direction away from the position restricting surface32e(leftward as viewed inFIG. 19), which causes the horizontal moving frame32to move in the same direction while following the leftward movement of the operation pin40bdue to the biasing force of the horizontal moving frame biasing spring37.

As shown inFIGS. 8 through 11,13and14, a second stepping motor (common actuator)70and a driven nut member (linearly movable member)71are installed in the close vicinity of the vertical guide shaft38. The second stepping motor70is provided with a drive shaft (feed screw shaft)70awhich extends parallel to said vertical guide shaft38and with which the driven nut member71is screw-engaged. As shown inFIG. 9, the driven nut member71is provided with a rotation restricting groove71awhich is slidably fitted on the vertical guide shaft38, and a female screw hole71bwhich is screw-engaged with the drive shaft70a. Rotating the drive shaft70aforward and reverse by driving the second stepping motor70causes the driven nut member71to move upwards and downwards in the y-axis direction along the vertical guide shaft38. As shown inFIGS. 10,11,13and14, the driven nut member71is in contact with a vertical moving frame36from bottom thereof. Due to this structure, driving the second stepping motor70causes the driven nut member71to move along the vertical guide shaft38, thus causing the vertical moving frame36to move along the vertical guide shaft38. Specifically, moving the driven nut member71upward causes the driven nut member71to push a lower bearing portion36eof the vertical moving frame36upward, so that the vertical moving frame36moves upward against the biasing force of the vertical moving frame biasing spring39. Conversely, moving the driven nut member71downward causes the vertical moving frame36to move downward together with the driven nut member71by the biasing force of the vertical moving frame biasing spring39.

In the above-described structure, the horizontal moving frame32can be caused to move left or right in the x-axis direction by driving the first stepping motor46forward or reverse. Furthermore, the vertical moving frame36can be caused to move upwards or downwards in the y-axis direction by driving the second stepping motor70forward or reverse.

The CCD holder30is supported by a horizontal moving frame32. The horizontal moving frame32is provided with a plate portion32fwhich is formed as a part of the arm portion32bto extend downward from the arm portion32b. The plate portion32fhas a substantially inverted-L shape as viewed from the front of the camera, and is elongated in the y-axis direction so that the lower end of the plate portion32freaches down to the close vicinity of the lower bearing portion36e. Additionally, the vertical moving frame36is provided at the end of the lower bearing portion36ewith a plate portion36s. As shown inFIGS. 8 through 11and13through14, two photo sensors55and56, each having a light emitter and a light receiver which are spaced apart from each other are installed in the housing11. The initial position of the horizontal moving frame32can be detected by the photo sensor55when the plate portion32fpasses between the light emitter and the light receiver of the photo sensor55. The plate portion32fand the photo sensor55constitute a photo interrupter. Likewise, the initial position of the vertical moving frame36can be detected by the photo sensor56when the plate portion36spasses between the light emitter and the light receiver of the photo sensor56. The plate portion36sand the photo sensor56constitute a photo interrupter.

The present embodiment of the zoom lens camera has an image-shake detection sensor57(seeFIG. 5) which detects the angular velocity around two axes (the vertical and horizontal axes of the camera) orthogonal to each other in a plane perpendicular to the photographing optical axis Z1. The magnitude and the direction of camera shake (vibrations) are detected by the image-shake detection sensor57. The control circuit14adetermines a moving angle by time-integrating the angular velocity of the camera shake in the two axial directions, detected by the image-shake detection sensor57. Subsequently, the control circuit14acalculates from the moving angle the moving amounts of the image on a focal plane (imaging surface/light receiving surface of the CCD13g) in the x-axis direction and in the y-axis direction. The control circuit14further calculates the driving amounts and the driving directions of the horizontal moving frame32and the vertical moving frame36for the respective axial directions (driving pulses for the first stepping motor46and the second stepping motor70) in order to counteract the camera shake. Thereupon, the first stepping motor46and the second stepping motor70are actuated and the operations thereof are controlled in accordance with the calculated values. In this manner, each of the horizontal moving frame32and the vertical moving frame36is driven in the calculated direction by the calculated amount in order to counteract the shake of the photographing optical axis Z1to thereby stabilize the image on the focal plane. The camera can be put into this image stabilization mode by turning on a photographing mode select switch14e(seeFIG. 5). If the switch14eis in an off-state, the image stabilizing capability is deactivated so that a normal photographing operation is performed.

The present embodiment of the zoom lens camera uses part of the above-described image stabilizing mechanism to perform the retracting operation (radially retracting operation) of the third lens group13e, the low-pass filter13fand the CCD13gtoward the off-optical-axis retracted position Z2into the retraction space SP when the zoom lens10is retracted from a photographic state. As shown inFIGS. 8 through 11,13and14, the second stepping motor70is installed with the body thereof being positioned at the bottom, and the drive shaft70athat extends upwards from the body of the second stepping motor70has a length greater than the amount of retracting movement of the vertical moving frame36in the y-axis direction. The vertical guide shaft38, which is parallel to the drive shaft70a, has a length greater than the length of the drive shaft70a. This configuration makes it possible to move the vertical moving frame36in the y-axis direction largely beyond a predetermined range of movement of the vertical moving frame36which is necessary for image stabilization, i.e., for counteracting image shake. Namely, the third lens group13e, the low-pass filter13fand the CCD13g, which are supported by the vertical moving frame36, can be moved from a position on the photographing optical axis Z1(the position shown inFIGS. 11 and 14) to the off-optical-axis retracted position Z2(the position shown inFIGS. 10 and 13).

The control circuit14acontrols the position of the vertical moving frame36by driving the second stepping motor70in accordance with the status of the zoom lens10. Firstly, when the zoom lens10is in the photographic state (i.e., when the focal length of the zoom lens10is set in between the wide-angle extremity and the telephoto extremity), the driven nut member71is positioned in the vicinity of the lower end of the drive shaft70aso that the vertical moving frame36(together with the third lens group13e, the low-pass filter13fand the CCD13g) is positioned on the photographing optical axis Z1. In this photographic state, the above described image stabilizing operation can be performed by driving the first stepping motor46and the second stepping motor70in the x-axis direction and the y-axis direction as appropriate. This image stabilizing operation is performed with the third lens group13e, the low-pass filter13fand the CCD13gremaining on the photographing optical axis Z1. Namely, during the image stabilizing operation, the third lens group13e, the low-pass filter13fand the CCD13gare not moved largely toward the off-optical-axis retracted position Z2beyond the photographing optical axis Z1.

The zoom lens10enters the photographic state shown inFIG. 2when the main switch14d(seeFIG. 5) of the camera is turned ON, and enters the retracted state shown inFIG. 1when the main switch14dis turned OFF. When the zoom lens changes from the photographic state to the retracted state upon the main switch being turned OFF, the control circuit14adrives the zoom motor MZ to perform the retracting operation of the zoom lens10and simultaneously drives the second stepping motor70to move the driven nut member71upward to a position at the close vicinity of the upper end of the drive shaft70a. Thereupon, the driven nut member71lifts the vertical moving frame36against the biasing force of the vertical moving frame biasing spring39, which causes the vertical moving frame36to move to the off-optical-axis retracted position Z2as shown inFIG. 1while being guided along the vertical guide shaft38. Consequently, the third lens group13e, the low-pass filter13fand the CCD13gare retracted radially outwards to the off-optical-axis retracted position Z2from a position on the photographing optical axis Z1.

The retracting operation of the vertical moving frame36, i.e., the operation of the second stepping motor70, is controlled to be completed at an angular position θ3(shown inFIGS. 6 and 7) before the zoom lens10is fully retracted. Subsequently, from the angular position θ3the helicoid ring18and the cam ring26further move rearward in the optical axis direction while rotating. Thereafter, when the helicoid ring18and the cam ring26reach their respective retracted positions shown inFIG. 1, the cylindrical portion25bof the second lens group support frame25that holds the second lens group13dis retracted into the space in the housing11which is formerly occupied by the vertical moving frame36when the zoom lens10is in the photographic state. In this manner, the thickness of the photographing optical system in the optical axis direction can be reduced in the retracted state of the zoom lens10, which makes it possible to reduce the thickness of the zoom lens10, which in turn makes it possible to reduce the thickness of a camera incorporating the zoom lens10. The timing of the commencement of the retracting operation of the vertical moving frame36can be freely determined within the range between the wide-angle extremity and the angular position θ3shown inFIGS. 6 and 7. In the present invention, the retracting operation of the vertical moving frame36that is carried out by the second stepping motor70is controlled so as to be started in the vicinity of the angular position θ2, at which the cam ring26changes its operating state between a state in which the cam ring26rotates at a fixed position and a state in which the cam ring26rotates while moving forward or rearward.

When the zoom lens10changes from the retracted state shown inFIG. 1to the photographic state shown inFIG. 2, operations of the zoom lens10which are reverse to the above described operations of the zoom lens10are performed. Firstly, the control circuit14aactuates the zoom motor MZ to start the advancing operation of the zoom lens10upon the main switch14dbeing turned ON. At this stage, the second stepping motor70has not been actuated. The advancing operation of the zoom motor MZ causes the second support frame25, which supports the second lens group13d, to move forward from the rearmost position shown inFIG. 1. This forward movement of the second support frame25opens the space below the vertical moving frame36positioned in the retracted position (and above the photographing optical axis Z1). The advancing operation of the second support frame25to a position where the second support frame25is not overlapped by the vertical moving frame36in the y-axis direction has been completed by the time the lens barrel10reaches the angular position θ3shown inFIGS. 6 and 7. From this state, the control circuit14astarts driving the second stepping motor70so that the driven nut member71moves to a position in the vicinity of the lower end of the drive shaft70awhile being guided along the vertical guide shaft38. At the same time, the vertical moving frame36follows the driven nut member71to move downward to a position on the photographing optical axis Z1, which is shown inFIGS. 11 and 14, by the biasing force of the vertical moving frame biasing spring39.

When the vertical moving frame36is retracted upward to the off-optical-axis retracted position Z2as shown inFIG. 20, the position restricting surface32ethat is provided on the arm portion32bof the horizontal moving frame32is disengaged from the operation pin40bthat is provided on the horizontal driving lever40. This disengagement of the position restricting surface32efrom the operation pin40bcauses the horizontal moving frame32to move leftward as viewed inFIG. 20by the biasing force of the horizontal moving frame biasing spring37up to a point at which the frame portion32aof the horizontal moving frame32abuts against the motion restricting frame36aof the vertical moving frame36. From this state, upon the vertical moving frame36being moved down to the photographing optical axis Z1, the inclined surface32dof the horizontal moving frame32comes in contact with the operation pin40bas shown by two-dot chain lines inFIG. 20. The inclined surface32dis inclined so as to guide the operation pin40bto the position restricting surface32eside according to the downward motion of the vertical moving frame36. Therefore, upon the vertical moving frame36being moved down to the photographing position, the operation pin40bis again engaged with the position restricting surface32eas shown inFIG. 19and the frame portion32aof the horizontal moving frame32returns to the neutral position thereof between the motion restricting frame36aand the motion restricting frame36b.

As can be understood from the above description, in the present embodiment of the zoom lens10, the vertical moving frame36is lifted from a position on the photographing optical axis Z1by the driving force of the second stepping motor70to move a retractable optical unit which is composed of the third lens group13e, the low-pass filter13fand the CCD13gto the off-optical-axis retracted position Z2(into the retraction space SP) when the zoom lens is retracted to the retracted position. The second lens group13denters the space on the photographing optical axis Z1which is created after the third lens group13e, the low-pass filter13fand the CCD13gare retracted to the off-optical-axis retracted position Z2as shown inFIG. 1, which makes it possible to reduce the thickness of the zoom lens10in the direction of the photographing optical axis Z1, and in turn makes it possible to achieve a compact camera incorporating the zoom lens10when the camera is in a non-photographing state even though the camera includes an optical image stabilizer.

FIG. 21shows the front/rear positional relationship, in the direction of the photographing optical axis Z1, of the components constituting the image stabilizing mechanism. As shown inFIG. 21, the first stepping motor46which constitutes a driving source for driving the CCD holder30in the x-axis direction, and the second stepping motor70which constitutes a driving source for driving the CCD holder30in the y-axis direction, are provided in front (i.e., on the object side) of a plane (image-stabilizing plane) (hereinafter referred to as the imaging plane) Pi which is coincident with (i.e., shares the same plane as that of) the imaging surface of the CCD13g. More specifically, the axis Pf1of the drive shaft46aof the first stepping motor46and the axis Pf2of the drive shaft70aof the second stepping motor70extend in a direction parallel to the imaging plane Pi, and axes Pf1and Pf2of the respective drive shafts46aand70aare positioned at forward distances Df1and Df2, respectively, in front of (on the object side) the imaging plane Pi in a forward direction of the photographing optical axis Z1. Furthermore, not only the first and second stepping motors46and70, the first moving member43which constitutes a driving-force transmission mechanism that transfers the driving force of the stepping motor46to the horizontal moving frame32, the horizontal driving lever40, and the driven nut member45also are positioned in front (on the object side) of the imaging plane Pi. A major portion of the driven nut member71, which transfers the driving force of the second stepping motor70to the vertical moving frame (imaging-sensor supporting member)36, also is provided in front of the imaging plane Pi in the forward direction of the photographing optical axis Z1, except for the end portion thereof which includes the rotation restricting groove71a.

On the other hand, as shown inFIG. 21, each of the horizontal guide shaft35, which guides the horizontal moving frame32in the x-axis direction, and the vertical guide shaft38, which guides the vertical moving frame36in the y-axis direction, is provided behind the imaging plane Pi (behind the imaging surface) in a rearward direction of the photographing optical axis Z1. More specifically, the both axes of the horizontal guide shaft35and the vertical guide shaft38extend in a direction parallel to the imaging plane Pi, and both axes of the horizontal guide shaft35and the vertical guide shaft38are positioned on a plane Pr which is located at a rearward distance Dr behind the imaging plane Pi in the direction of the photographing optical axis Z1. In the illustrated embodiment, the amount of “shift” from which the axes of the horizontal guide shaft35and the vertical guide shaft38are positioned from the imaging plane Pi is the same. The axis of the horizontal guide shaft35extends through the plane Pr, although the horizontal guide shaft35is positioned behind a spring hooking portion36finFIG. 21, and hence is not shown. Note that, as mentioned above, the major portion of the driven nut member71, including the female screw hole71b, is provided in front of the imaging plane Pi in the direction of the photographing optical axis Z1; however, due to the engagement relationship between the rotation restricting groove71aand the vertical guide shaft38, the end portion which includes the rotation restricting groove71aextends rearwards past the imaging plane Pi in the optical axis direction.

In the above-described image stabilizing mechanism which drives the CCD holder30(the third lens group13e, the low-pass filter13fand the CCD13g) along a plane extending substantially orthogonal to the photographing optical axis Z1in order to perform the camera shake counteracting operation (image stabilizing operation) and the radially retracting operation, driving devices such as the first and second stepping motors46and70are provided in a forward area (on the object side) with respect to the imaging plane Pi, and guide mechanisms such as the horizontal guide shaft35and the vertical guide shaft38are provided in a rearward area with respect to the imaging plane Pi. According to such an arrangement, the CCD holder30can be driven in a highly precise manner during a camera shake counteracting operation; the reason for which will be discussed hereinafter.

Generally, in a guiding device which guides a movable member, a minimal clearance is necessary in order to move such a movable member in a smooth manner. Furthermore, in a driving device such as a motor, backlash unavoidably occurs during the transfer of the driving force thereof. Namely, in the illustrated embodiment, clearance exists between the horizontal guide shaft35and the horizontal moving frame32, clearance exists between the vertical guide shaft38and the vertical moving frame36(the vertical through-holes36y1and36y2), and backlash also exists in the drive-transmission path from the first stepping motor46through to the horizontal moving frame32(via the horizontal driving lever40, the first moving member43, and the driven nut member45) and in the drive-transmission path from the second stepping motor70through to the vertical moving frame36(via the driven nut member71). Such clearance and backlash are determined at the design stage so as not to have adverse influence on the driving precision thereof in practice. However, in view of possible manufacturing error which may occur in the various components, it is desirable to construct an image-stabilizing mechanism in which such clearance and backlash has a minimal adverse influence on the driving precision thereof. Namely, in the illustrated embodiment, movable members, which are driven during an image-stabilizing operation, are included in the CCD holder13g, and since tilting and positional shift of the imaging surface of the CCD13ghave a large influence on the picture quality, it is necessary to effectively prevent tilting and positional shift of the imaging surface from occurring. Furthermore, the first and second stepping motors46and70are used as the driving source of the image-stabilizing mechanism. As commonly known in the art, a stepping motor is rotated about a rotational axis in a stepwise manner in accordance with input pulses, and since there is a chance that the backlash which exists in the driving-force transmission mechanism which converts such rotational motion into linear motion may induce a time lapse (retardation) in control during high-speed reciprocating motion in an image-stabilizing operation, it is necessary to increase the precision of the image-stabilizing mechanism and to increase the capability of tracking the motion of the CCD holder30during the driving of the stepping motor.

However, in a driving device for driving a movable member, the farther the movable member is moved, the easier it is for the region where inaccuracies (such as clearance and backlash) occur to have a greater influence on the driving precision of the movable member. For example, in the case of a guide shaft and a slidable member, if the slidable member were to have a tilt error about one point on the guide shaft, even for the same amount of tilt, a slidable member which is provided at a radial position that is farther away from the center of tilt has greater amount of positional error due to such tilt than in the case of a slidable member which is provided at a radial position that is closer to the center of tilt. Furthermore, if the distance from the movable member to the guide device and/or driving device is large, any intermediate members provided therebetween have to be formed longer, which increases the chance of having adverse influence on the driving precision thereof due flexing of such intermediate members and manufacturing error. Furthermore, the longer such intermediate members are, the greater the space that is required, resulting in undesirable enlargement of the apparatus (i.e., the zoom lens10). Due to such reasons, it is desirable to provide the guide device and driving device of the movable member as close to the movable member as possible. In the illustrated embodiment, the first and second stepping motors46and70, which constitute driving devices, are provided on one side of (in front of) the imaging plane Pi, whereas the horizontal guide shaft35and the vertical guide shaft38, which constitute guiding devices, are provided on the other side of (behind) the imaging plane Pi. Accordingly, it is easy to provide the driving devices and guiding devices close to the imaging surface of the CCD13g, the CCD13gbeing the subject (movable member) which is being moved in an image-stabilizing operation.

A more specific description will herein be given with reference toFIG. 22, which corresponds to the present invention, and with reference to comparative examples shown inFIGS. 24 through 26.FIG. 22shows the main components of the y-axis direction portion of the image-stabilization mechanism (y-axis-direction image-stabilizing mechanism) for the CCD13g, according to the present invention. InFIG. 22, the driven nut member71is omitted for clarity, and only the second stepping motor70and the vertical guide shaft38which is a guiding device for guiding the movable member (CCD13g) in the y-axis direction are shown. As shown inFIG. 22, by distributing the positions of the second stepping motor70(on the axis Pf2) and the vertical guide shaft38(on the plane Pr) at front and rearward locations, respectively, with respect to the imaging plane Pi, the second stepping motor70and the vertical guide shaft38can be respectively provided close to the imaging plane Pi without interfering with each other.

In the comparative examples shown inFIGS. 24 and 25, second stepping motors170and270(and drive shafts170aand270a) and vertical guide shafts138and238, are respectively provided on the rearward side of the imaging plane Pi of respective CCDs113gand213g.

In the construction shown inFIG. 24, since the vertical guide shaft138is provided on the other side (rearward side) of the second stepping motor170from that of the CCD113g(which is provided in front of the second stepping motor170(object side)) the vertical guide shaft138cannot be positioned close to the imaging plane Pi. Hence, precision error in the sliding portion between the vertical guide shaft138and a vertical moving frame (imaging-sensor supporting member)136has a large adverse influence on the moving precision of the CCD113g. In other words, since the allowable clearance of the sliding portion between the vertical guide shaft138and the vertical moving frame136is small, the required precision of the moving parts (i.e., the vertical guide shaft138and the vertical moving frame136) becomes strict, which can easily incur high manufacturing costs.

In the structure shown inFIG. 25, since the second stepping motor270(drive shaft270a) is provided on the other side (rearward side) of the vertical guide shaft238from that of the CCD213g(which is provided in front of the vertical guide shaft238(object side)), the second stepping motor270cannot be positioned close to the imaging plane Pi. Hence, backlash which exists within the driving-force transmission for transferring the rotational driving force of the drive shaft270ato the CCD213gcan easily have a large adverse influence on the driving precision of the CCD213g. In other words, similar to the structure shown inFIG. 24, the required precision of the moving parts (i.e., the vertical guide shaft238and a vertical moving frame (imaging-sensor supporting member)236) becomes strict, which can easily incur high manufacturing costs.

In another comparative example shown inFIG. 26, a second stepping motor370(drive shaft370a) and a vertical guide shaft338are both provided in front of the imaging plane Pi of a CCD313g. In the structure shown inFIG. 26, since the second stepping motor370(drive shaft370a) is provided on the other side of (in front of) the vertical guide shaft338, the second stepping motor370cannot be positioned close to the imaging plane Pi. Hence, similar to the structure shown inFIG. 25, backlash which exists within the mechanism for transferring the rotational driving force of the drive shaft370ato the CCD313gcan easily have a large adverse influence on the driving precision of the CCD313g. Moreover, in the structure ofFIG. 26, even if the positions of the second stepping motor370and the vertical guide shaft338were to be switched, the same problems as in the structure ofFIG. 24would occur in the vicinity of the vertical guide shaft338(i.e., occurrence of precision error in the sliding portion between the vertical guide shaft338and a vertical moving frame (imaging-sensor supporting member)336).

In other words, as can be understood from the comparative examples shown inFIGS. 24 through 26, in a construction wherein a driving device (second stepping motor170,270or370) and a guiding device (vertical guide shaft138,238or338) are both provided in an area in front of the imaging plane Pi or are both provided in an area behind the imaging plane Pi, either the driving device or the guiding device will end up being located far away from the imaging surface of the CCD (113g,213gor313g), and accordingly, it would be difficult to achieve high-precision image-stabilization at a low cost. Conversely, according to the construction of the present invention shown inFIG. 22, the positions of the second stepping motor70and the vertical guide shaft38are distributed on front and rearward sides of the imaging plane Pi (i.e., are never provided on the same side of the imaging plane Pi), and accordingly, the driving device and the guiding device have a minimal adverse influence on the positional precision of the imaging surface of the CCD13g, and image-stabilization can be performed with high precision at a low cost.

In order to drive the CCD13gat a high precision, the front and rearward positions (with respect to the imaging plane Pi) of the axis of the vertical guide shaft38and the axis of the second stepping motor70can be reversed as shown inFIG. 23. However, with respect to the space efficiency within the zoom lens10of the present invention, the structure shown inFIG. 22is more desirable than that ofFIG. 23. The reason why the structure shown inFIG. 22is more desirable is because, as shown inFIG. 2, rotational members such as the helicoid ring18and the cam ring26are provided in front of (on the object side) the CCD holder30, and it is necessary to avoid interference between such front rotational members and the image-stabilizing mechanism. Furthermore, since the back surface (wall) of the camera is close to the rearward side of the CCD holder30, it is difficult to achieve a large-enough space in the direction of the thickness of the camera (i.e., in the left/right direction ofFIGS. 1 and 2(in the direction of the photographing optical axis Z1)). If the vertical guide shaft38and the second stepping motor70are compared, as can be understood fromFIG. 22, the vertical guide shaft38is long in the y-axis direction, however, the diameter thereof is small (the width thereof in the left/right direction inFIG. 22is small). Conversely, the drive shaft70aof the second stepping motor70is short in the y-axis direction, but the motor body of the second stepping motor70has a relatively large diameter (the width thereof in the left/right direction inFIG. 22is relatively large). Accordingly, it is more desirable to provide the second stepping motor70, having a short overall length in the y-axis direction, in the area in front of the imaging plane Pi wherein rotational members such as the helicoid ring18and the cam ring26are provided, rather than the vertical guide shaft38, because it is easier to avoid interference between the second stepping motor70and the rotational members such as the helicoid ring18and the cam ring26. Furthermore, it is more desirable to provide the vertical guide shaft38, which has a smaller diameter than that of the second stepping motor70, in the area on the rearward side of the imaging plane Pi which is narrow in width in the thickness direction of the camera (in the direction of the photographing optical axis Z1). In other words, providing the vertical guide shaft38behind the imaging plane Pi enables the camera to be constructed thinner (in the direction of the photographing optical axis Z1). In the area behind the CCD13g, since there is a space into which neither the helicoid ring18nor the cam ring26enter (seeFIG. 1), even if the vertical guide shaft38is long in the y-axis direction, the vertical guide shaft38can be easily provided behind the CCD13gwithout interfering with the helicoid ring18or cam ring26.

Note that although inFIG. 22the distances of the axis Pf2and the plane Pr from the imaging plane Pi in the forward and rearward directions, respectively, are shown as substantially the same distance, in practice, as shown inFIG. 21, the rearward distance Dr from the imaging plane Pi to the axes of the horizontal guide shaft35and the vertical guide shaft38, and the forward distances Df1and Df2from the imaging plane Pi to the axes of the drive shafts46aand70aof the first and second stepping motors46and70, respectively, have the following relationship:

Df1>Dr, and

In other words, in the forward/rearward direction of the CCD13g(i.e., in the direction of the photographing optical axis Z1), the horizontal guide shaft35and the vertical guide shaft38are positioned closer to the imaging plane Pi than the first and second stepping motors46and70. As mentioned above, since the space behind the CCD13gis particularly restricted, with respect to reducing the thickness of the camera in the direction of the photographing optical axis Z1, it is desirable for the horizontal guide shaft35and the vertical guide shaft38to be positioned as close to the imaging plane Pi as possible, as shown inFIG. 21.

Although the above description has been directed to the characteristics of the vertical guide shaft38and the second stepping motor70, which constitute the y-axis-direction image-stabilizing mechanism, the horizontal guide35and the first stepping motor46, which constitute an x-axis-direction image-stabilizing mechanism, are also positioned in accordance with the same technical principle as that of the vertical guide shaft38and the second stepping motor70. Namely, the first stepping motor46and the horizontal guide shaft35are distributed (positioned) on front and rearward sides of the imaging plane Pi of the CCD13g, respectively (seeFIG. 21), so that it is likewise possible to provide both the first stepping motor46and the horizontal guide shaft35close to the CCD13g, respectively, in the direction of the photographing optical axis Z1. Accordingly, the manufacturing cost of the image-stabilizing mechanism can be reduced, and the CCD holder30which includes the CCD13gcan be driven in the x-axis direction with high precision.

Note that similar to the modified embodiment of the y-axis-direction image-stabilizing mechanism shown inFIG. 23, the x-axis-direction image-stabilizing mechanism can alternatively be constructed to provide the horizontal guide shaft35in front of the imaging plane Pi, and to provide the first stepping motor46behind the imaging plane Pi. However, in the x-axis-direction image-stabilizing mechanism, as can be understood fromFIGS. 13 and 14, since a portion of the horizontal guide shaft35is positioned within the inner circumference of the helicoid ring18, as viewed from the front of the zoom lens10, it is desirable to provide the first stepping motor46in an area in front of the imaging plane Pi and provide the horizontal guide shaft35in an area behind the imaging plane Pi in order to avoid interference between the horizontal guide shaft35and the helicoid ring18. Since the first stepping motor46has a shorter overall length in the x-axis direction than that of the horizontal guide shaft35, the first stepping motor46can be space-efficiently accommodated in an area in front of the imaging plane Pi without interfering with the helicoid ring18(seeFIGS. 13 and 14).

Although the present invention has been described with respect to the illustrated embodiments, the present invention is not limited thereto. Although in the illustrated embodiments the optical axis of the zoom lens10is the photographing optical axis Z1which has no bends therein, the present invention can be applied to an optical system wherein the photographing optical axis thereof is bent at one or more optical axis positions. Furthermore, although in the illustrated embodiments, the third lens group13e, the low-pass filter13fand the CCD13gare moved as an integral unit during an image-stabilizing operation, the present invention can be applied to an embodiment wherein only the CCD (and the cover glass thereof) is moved during an image-stabilizing operation.