Lens barrel and image pickup apparatus

In a lens barrel including an image pickup optical system containing plural lens groups and a barrel member for holding the image pickup optical system and conducting protruding and retracting, the lens frame holding a prescribed lens group of the image pickup optical system is swung so that the prescribed lens group is moved to a position where the optical axis is different from those of other lens groups at the time of the retraction, and in the process of changing from the protruded state to retracted state, the lens frame is swung by engagement with a cam-shaped portion of a first engagement member, and is then engaged with a second engagement member.

This application is based on Japanese Patent Application No. 2010-191904 filed on Aug. 30, 2010 with Japanese Patent Office, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a lens barrel designed to move a prescribed lens group to a position where the optical axis of the prescribed lens is different from that of another lens group at the time of retraction, and an image pickup apparatus provided with the lens barrel.

What is commonly known in the prior art includes a lens barrel which is retracted by reducing the interval between lens groups in an image pickup optical system in order to improve portability, when not used for photographing.

One of recent disclosures for further minimizing the thickness of the retracted barrel includes a lens barrel where a prescribed lens group is moved to a position where the optical axis of this is different from an optical axis of another lens group as well as the interval between lens groups is reduced (e.g., the Japanese Unexamined Patent Application Publication No. 2004-233916).

A common mechanism for moving a prescribed lens group to a position where the optical axis of this is different from that of another lens group generally has the following structure. As described in the aforementioned Patent Application Publication No. 2004-233916, a lens frame for holding the prescribed lens group is supported by a shaft in such a way that the frame can be swung, and is biased by a spring. This lens frame is brought in contact with a stopper and is stopped at a position where the optical axis agrees with that of another lens group. At the time of barrel refraction, a cam is engaged with the lens frame to make it to be swung against the bias pressure of the spring, whereby lens retraction is performed.

In the aforementioned lens barrel where a prescribed lens group is moved to a position where the optical axis is different from that of another lens group whereby lens retraction is performed, it is a common practice that a spring bias force is constantly applied to the engaged cam at the time of lens retraction. When this structure is exposed, for example, to a high temperature for a long time with the spring bias force applied thereto, the cam may be deformed by the bias force on a rare occasion if the cam is made of resin and is comparatively fragile. As a result, the lens frame may fail to perform a desired swinging operation and this problem has been one of the causes for reduction in operation reliability. Further, in a proposal for solving these problems, the cam is made of a metallic material. However, this fails to solve the problem of increased costs.

In view of the problems described above, it is one of the objects of the present invention to provide a thin lens barrel of high operation reliability at a reduced cost.

SUMMARY

To achieve at least one of the above mentioned objects, a lens barrel and image pickup apparatus reflecting one aspect of the present invention include the following.

(1) A lens barrel including: an image pickup optical system having a plurality of lens groups; a barrel member which holds the image pickup optical system and is protruded and retracted; and a first engagement member and a second engagement member for swinging a lens frame which holds a prescribed lens group of the image pickup optical system so as to move the prescribed lens group to a position where an optical axis of the prescribed lens group is different from an optical axis of another lens group when the barrel member is retracted, wherein, the lens frame is swung while being engaged with a cam-shaped portion of the first engagement member in a process of changing a state of the barrel member from a protruded state to a retracted state, and then the lens frame is engaged with the second engagement member.

(2) The lens barrel described in the above item (1), wherein the second engagement member is a part of a mechanism for camera shake compensation.

(3) The lens barrel described in the above item (2), wherein the lens frame is further swung by the mechanism for camera shake compensation.

(4) The lens barrel described in the above item (1), wherein a cam shape is formed on the second engagement member, and the lens frame is further swung by the cam shape of the second engagement member.

(5) An image pickup apparatus provided with the lens barrel described in any one of the above items (1) through (4), and an imaging element for photoelectric conversion of a subject image.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following describes the present invention with reference to embodiments without the present invention being restricted thereto.

FIG. 1is an external view representing a camera as an example of the image pickup apparatus provided with a lens barrel in the present embodiment.

InFIG. 1, the numeral150represents a lens barrel of the present embodiment having a zooming imaging optical system inside. The numeral111represents a finder window, the numeral112represents a release button, the numeral113represents a flush light emitting section, and the numeral116represents an external input/output terminal (for example, USB terminal). The numeral117represents a slide barrier and the lens barrel150is retracted when the slide barrier117is operated in a direction to close. By pressing the release button to a first stage, the camera is activated to be ready for photographing, that is, focusing and photometry, and to a second stage, photographing exposure is executed.

Although not illustrated, the back of the camera is provided with a finder ocular portion, a zoom button for zooming up and down, an image display section for displaying an image and other text information, and a menu/set button. The camera bottom surface is equipped with a tripod hole and a slot for a battery for power supply to various portions and a card used to record photographed images.

The following describes the lens barrel150of the present embodiment.

First Embodiment

FIG. 2is a schematic cross sectional view showing the protruded state of the lens ban1150of the first embodiment (in the photographing mode). The state of the wide-angle end is shown in this diagram.

InFIG. 2, the symbol O represents an optical axis, the numeral1,2and3represent a first lens group, a second lens group and a third lens group respectively, and the numeral54represents an optical filter where an infrared cut filter and optical low pass filter are laminated. These configure an imaging optical system. The numeral55represents an imaging element.

The symbol1krepresents a first lens group lens frame to retain the first lens group1and is retained by the front cylinder71. The symbol2K represents a second lens group lens frame to retain the second lens group2. The second lens group lens frame k2is retained by second lens group moving frame66and is configured to be capable of moving out from the optical axis O by swinging. The numeral64represents an aperture and/or shutter unit retained by the second lens group moving frame66. The symbol3krepresenting a third lens group lens frame retains the third lens group3and is configured to be able to move in a direction of the optical axis O by an unillustrated stepping motor. The third lens group lens frame3kcan move independently thus focusing can be carried out by moving the third lens group3. The numeral65represents a bottom board and it is provided with an imaging element moving mechanism90for camera shake compensation by moving the imaging element55along the surface perpendicular to the optical axis O.

Next, motion of lens barrel150will be described.

InFIG. 2, the fixed barrel74is mounted onto the bottom board65. On the inner surface of the fixed barrel74, a cam groove74cis formed. The numeral73represents an intermediate barrel which is rotated by an unillustrated motor, through the intermediate barrel drive gear85, a reduction gear train and column-shaped gear86. The intermediate barrel73is moved by this rotation in the direction of the optical axis O while a cam pin73pimplanted in the intermediated barrel73is guided by the cam groove74cformed on the fixed barrel74.

The guide ring83is engaged with a straight guide section formed on the fixed barrel74to be capable of straight movement in the direction of the optical axis O and moves straight in the optical axis O direction while maintaining the intermediate barrel drive gear85, in accordance with movement of the intermediate barrel73in the direction of the optical axis O. On this guide ring83, a cam groove and a straight guide section are formed.

In a cam cylinder72, there is implanted cam pin72pwhich engages with the intermediate barrel73and guide ring83. Cam cylinder72rotates along with rotation of the intermediate barrel73with which the cam pin72pengages, and moves in the direction of the optical axis O while being guided by the cam groove formed on the guide ring83, with which the cam pin72pengages. That is, the earn pin72pis engaged with a key way formed to be parallel with the optical axis of intermediate barrel73and with the cam groove formed on the guide ring83. On an inner surface of the cam cylinder72, there is formed a cam groove to guide the front cylinder71and second lens group moving frame66respectively.

The straight guide82A is engaged with a straight guide section formed on the guide ring83to be able to move straight in the direction of the optical axis O and moves straight in the direction of the optical axis O in accordance with movement of the cam cylinder72in the direction of the optical axis O. The decorative cylinder82B is also engaged with the straight guide section formed on the guide ring83to be able to move straight, and moves straight in the direction of the optical axis O in accordance with movement of the cam cylinder72in the direction of the optical axis O.

The front cylinder71on which the cam pin71pto engage with one cam groove formed on the cam cylinder72is implanted, is engaging with the straight guide82A. Also the second lens group moving frame66on which the cam pin66pto engage with another cam groove formed on the cam cylinder72is implanted, is engaging with the straight guide82A.

In this way, the front cylinder71and second lens group moving frame66are moved straight in the direction of the optical axis O by rotation of the cam cylinder72, being guided by the cam grooves engaged respectively, thus a distance between the first lens group1retained by the front cylinder71and the second lens group2retained by the second lens group moving frame66is changed so as to carry out zooming.

From this state, the intermediate barrel drive gear85is further driven to rotate the intermediate barrel73, and positions of the first lens group and second lens group are changed by the cam groove formed on the inner surface of the cam cylinder72so as to carry out zooming.

The above is an outline of movement of the lens barrel150of the first embodiment during the protrusion.

FIG. 3is an extracted perspective view of the imaging element moving mechanism90.

In the imaging element moving mechanism90shown inFIG. 3, the first moving member96holds an imaging element55and optical filter54composed of an infrared cut filter or an optical low-pass filter in front of the imaging element55.

On the second moving member93, there are fixed two guide shafts95aand95beach representing a guide member, and first moving member96is arranged to be guided by the guide shafts95aand95bto be capable of moving in the direction of the illustrated arrow Y. That is, the second moving member93holds the first moving member96.

On the base plate91, there are fixed two guide shafts92aand92beach representing a guide member, and the second moving member93is guided by the guide shafts92aand92bto be capable of moving in the direction of the illustrated arrow P.

Further, the arm portion93mand PI shielding section93fare formed integrally on the second moving member93. The arm portion93mis in contact with the nut representing the second female screw member that engages with the lead screw which is the second male screw member rotated by the stepping motor61P serving as the second motor. Owing to this, by rotation of the stepping motor61P, the second moving member93is moved in the direction of the arrow P. The PI shielding section93fis configured to pass through the light emitting and receiving section of the photo interrupter PIp which is an initial position detecting section fixed on the base plate91.

Similarly, the first moving member96is provided with an arm portion and PI shielding section formed as an integral unit, although not illustrated. The arm portion is in contact with the nut as a first female screw member that is engaged with the lead screw as a first male screw member which is rotated by the stepping motor61Y as a first motor. This arrangement allows the first moving member96to be moved in the direction of the arrow Y by the rotation of the stepping motor61Y. The PI shielding section is formed to pass through the light transmitting and receiving sections of the photo interrupter PIy as an initial position detector fixed onto the base plate91.

Owing to this, by driving stepping motors61P and61Y, it is ensured that the first moving member96, that is, the imaging element55can be moved in a plane that is perpendicular to the optical axis OB of the image pickup optical system.

FIG. 4is a schematic cross-sectional view showing a refracted state of the lens barrel150related to the first embodiment.

To realize the retracted state of the lens barrel150shown inFIG. 4, the intermediate barrel73is rotated reversely by rotating the intermediate barrel drive gear85in the reverse direction through an unillustrated motor, a reduction gear train and a column-shaped gear86, after third lens group lens frame3kis moved to the bottom board65side from the state shown inFIG. 2.

By the reverse rotation of the intermediate barrel73, the cam cylinder72is rotated reversely, then the front cylinder71and second lens group moving frame66approach each other while being guided by the cam grooves engaged respectively, and the intermediate barrel73and cam cylinder72move to the bottom board65side.

At this stage, the second lens group lens frame2kretained by the second lens group moving frame66is rotatably supported by an unillustrated rotary shaft, and swings centering around the rotary shaft and moves away to a position different from the optical axis of other lens groups. Further, the second lens group lens frame2kis structured to carries out sliding movement with respect to the rotary shaft after evacuating from the optical axis O.

The intermediate barrel73and cam cylinder72move to the bottom board65side and the third lens group3, second lens group moving frame66, aperture and/or shutter unit64and first lens group I come close to each other maintaining minimum distances to realize the retraction state.

In the process of changing from the protruded state to the retracted state, the second lens group lens frame2kis brought to a position where the optical axis is different from those of other lens groups. After that, the lens frame section of the second lens group lens frame2kis engaged with the second moving member93of the imaging element moving mechanism90, as illustrated. The lens frame section of the second lens group lens frame2kis moved upward on the figure by the movement of the second moving member93of the imaging element moving mechanism90.

FIG. 5is a perspective view showing a second lens group lens frame2kof the lens barrel in the first embodiment. This view shows the second lens group lens frame2kand the second lens group moving frame66as observed from the imaging element. It shows the state where the lens barrel protrudes and the second lens group2is located on the optical axis O to enable photographing.

As shown in the diagram, the second lens group moving frame66is provided with a rotary shaft67, and the rotary shaft67is inserted in the cylindrical portion2ktformed on the second lens group lens frame2k. A torsion coil spring68is mounted between the cylindrical portion2ktand the second lens group moving frame66, and the rotary shaft67is provided with a retaining device69for the cylindrical portion2kt.

This torsion coil spring68applies bias force to the cylindrical portion2ktformed on the second lens group lens frame2kin the direction of the arrow A using the coil structure. Using both ends, the torsion coil spring68applies bias force to the arm portion of the second lens group lens frame2kin the direction of the arrow B. The projection2ksformed on the second lens group lens frame2kcomes in contact with the stopper pin66s formed on the second lens group moving frame66so that the second lens group lens frame2k, i.e., the second lens group2is positioned on the optical axis O. Further, a pin2kpis formed on the cylindrical portion2kt.

The symbol3kkindicates a cam-shaped portion formed on the third lens group lens frame3k. The pin2kpand cam-shaped portion3kkare formed at the position where engagement with each other is performed in the process of changing &Hu the protruded state to the retracted state. When the lens barrel has protruded to enable photographing, the pin2kpis separated from the cam-shaped portion3kk.

Each ofFIGS. 6a-6dis a diagram showing the positional relationship of a pin2kp, cam-shaped portion3kkand bottom board65in the process of changing from the protruded state of the lens barrel150to the retracted state in the first embodiment.

FIG. 7is a diagram showing the positional relationship of a second lens group lens frame2kand imaging element moving mechanism90in the process of changing from the protruded state of the lens barrel150to the retracted state in the first embodiment.

Referring toFIGS. 6a-6dandFIG. 7, the following describes the operation of the second lens group lens frame2kin the process of changing from the protruded state of the lens barrel150to the retracted state in the first embodiment.

When the lens barrel has protruded as illustrated inFIG. 2andFIG. 5, the pin2kp, the cam-shaped portion3kkand bottom board65are separated from one another, as shown inFIG. 6a.

To change the lens barrel from the protruded state to the retracted state, the third lens group lens frame3kis moved to the bottom board65side (imaging element side), as shown above. This ensures that the cam-shaped portion3kkformed on the third lens group lens frame3kcomes closer to the bottom board65, as shown inFIG. 6b. In this case, the second lens group lens frame2kis located at the position indicated by the broken line ofFIG. 7.

When the third lens group lens frame3khas been moved, the second lens group moving frame66travels toward the bottom board65(imaging element), as described above. The pin2kpformed on the cylindrical portion2ktof the second lens group lens frame2kis engaged with the cam-shaped portion3kk, as illustrated inFIG. 6c.

After the pin2kphas been engaged with the cam-shaped portion3kk, the second lens group moving frame66is further moved toward the bottom board65(imaging element). This allows the pin2kpto travel along the slope of the cam-shaped portion3kk. The second lens group lens frame2kofFIG. 5is swung in the direction opposite to the B-marked direction against the bias force of the torsion coil spring68.

When the second lens group moving frame66has further traveled toward the bottom board65, the pin2kpis swung to a prescribed position of retraction at the position C on the cam-shaped portion3kk(wherein the optical axis is different from those of other lens groups), as shown inFIG. 6d. This allows the lens frame section of the second lens group lens frame2kto be moved from the position illustrated by the broken line ofFIG. 7to the position illustrated by the solid line. Thus, the lens frame section of the second lens group lens frame2kis swung to the position where it does not interfere with the second moving member93of the imaging element moving mechanism90, as viewed in the direction of optical axis.

When the pin2kphas come in contact with the bottom board65, the second lens group moving frame66is further moved toward the bottom board65. This allows the second lens group lens frame2kto slide and move along the rotary shaft67ofFIG. 5in the direction opposite to the A-marked direction against the bias force of the torsion coil spring68. When the second lens group moving frame66has come closer to the bottom board65, the end of lens frame section of the second lens group lens frame2kis located outside the second moving member93of the imaging element moving mechanism90, as shown inFIG. 4.

After the second lens group moving frame66has come to a prescribed position at the time of retraction on the bottom board65side and has stopped there, the stepping motor61P of the imaging element moving mechanism90is driven, and the second moving member93is moved upward in the figure. This allows the pin2kpto be separated from the cam-shaped portion3kk, and to come to the position D ofFIG. 6d.

The retracted state ofFIG. 4is reached by the aforementioned procedure.

To be more specific, in the process of changing from the protruded state to the retracted state, the lens barrel150of the first embodiment ensures that the second lens group lens frame2kis moved to the position where the optical axis is different from those of other lens groups by being engaged with the cam-shaped portion3kkformed on the third lens group lens frame3k, as the first engagement member, and being swung. After that, the second lens group lens frame2kis engaged with the second moving member93of the imaging element moving mechanism90as the second engagement member. Then the second lens group lens frame2kis further swung by the imaging element moving mechanism90.

To be more specific, at the time of lens retraction, the bias force of the torsion coil spring68applied to the second lens group lens frame2kis received by the second moving member93of a rigid imaging element moving mechanism90. Thus, even if the lens group is exposed to severe working conditions for a long time, this structure avoids the possibility of the lens group being deformed by the bias force, and enhances the operation reliability. Further, the cam for swinging can be made of resin, with the result that a lens barrel of reduced costs can be produced.

In the present example, the second lens group lens frame2kis further swung by the second moving member93of the imaging element moving mechanism90, for the sake of explanation. Without being restricted thereto, however, it is also possible to make such arrangements that the portion of the lens frame section of the second lens group lens frame2kcoming in contact with the second moving member93is designed in a tapered shape. After this tapered portion has come in contact with the second moving member93, the second lens group lens frame2kis further swung along the taper shape.

In this example, an imaging element moving mechanism was used as a shake compensation device for the sake of explanation. Without being restricted thereto, it is also possible to use the mechanism where the lens group is moved for shake compensation. In this case, the lens group moving mechanism for shake compensation is used as the second engagement member, and is engaged with the lens frame section of the second lens group lens frame2k. This structure provides the same effect.

Second Embodiment

FIG. 8is a schematic cross sectional view showing the protruded state (photographing state) of the lens barrel150of a second embodiment. It should be noted that the state of the wide-angle end is illustrated inFIG. 8.

FIG. 9is a schematic cross sectional view showing the retracted state of the lens barrel150in the second embodiment.

In the lens barrel150of the second embodiment ofFIG. 8andFIG. 9, the operations of protruding and retraction are the same as those shown inFIG. 2andFIG. 4. The imaging element moving mechanism90for shake compensation is omitted. Thus, the description of protrusion and retraction is omitted. Only the swinging operation of the second lens group lens frame2kwill be described.

FIG. 10is a perspective view showing a second lens group lens frame2kof the lens barrel in the second embodiment. This view shows the second lens group lens frame2kand the second lens group moving frame66as observed from the imaging element. It shows the protruded state of the lens barrel and the second lens group2is located on the optical axis O to enable photographing.

As shown in the diagram, the second lens group moving frame66is provided with a rotary shaft67, and the rotary shaft67is inserted in the cylindrical portion2ktformed on the second lens group lens frame2k. A torsion coil spring68is mounted between the cylindrical portion2ktand the second lens group moving frame66, and the rotary shaft67is provided with a retaining device69for the cylindrical portion2kt.

This torsion coil spring68applies bias force to the cylindrical portion2ktformed on the second lens group lens frame2kin the direction of the arrow A using the coil structure. Using both ends, the torsion coil spring68applies bias force to the arm portion of the second lens group lens frame2kin the direction of the arrow B. The projection2ksformed on the second lens group lens frame2kcomes in contact with the stopper pin66s formed on the second lens group moving frame66so that the second lens group lens frame2k, i.e., the second lens group2is positioned on the optical axis O. Further, a pin2kpis formed on the cylindrical portion2kt.

The symbol3kkindicates a cam-shaped portion formed on the third lens group lens frame3k. The numeral65kindicates cam-shaped portion formed on the bottom board65. The pin2kp, cam-shaped portion3kkand cam-shaped portion65kare formed at the position where engagement with each other is performed in the process of changing from the protruded state to the retracted state. When the lens barrel has protruded to enable photographing, the pin2kp, cam-shaped portion3kkand cam-shaped portion65kare separated from one another.

Each ofFIGS. 11a-11dis a diagram showing the positional relationship of a pin2kp, cam-shaped portion3kkand cam-shaped portion65kin the process of changing from the protruded state of the lens barrel150to the retracted state in the second embodiment.

When the lens barrel is placed in the protruded state as illustrated inFIG. 8, the pin2kp, cam-shaped portion3kkand cam-shaped portion65kare separated from one another, as shown inFIG. 11a. To move the lens barrel from the protruded state to the retracted state, the third lens group lens frame3kis moved toward the bottom board65side (imaging element side), as described above. Then the cam-shaped portion3kkformed on the third lens group lens frame3kis aligned with the upper portion of the cam-shaped portion65kformed on the bottom board65, as shown inFIG. 11b, with the result that the cam is made in a continuous integral shape.

Upon completion of the traveling of the third lens group lens frame3k, the second lens group moving frame66travels toward the bottom board65(toward imaging element), as described above. The pin2kpformed on the cylindrical portion2ktof the second lens group lens frame2kstarts to be engaged with the cam-shaped portion3kk, as shown inFIG. 11c. When the pin2kphas been engaged with the cam-shaped portion3kk, the pin2kpis moved along the slope of the cam shape. The second lens group lens frame2kofFIG. 10is swung in the direction opposite to the B-marked direction against the bias force of the torsion coil spring68. When the second lens group moving frame66has moved further toward the bottom board65, the pin2kpis transferred to the cam-shaped portion65kfrom the cam-shaped portion3kk. The lens frame2kis further swung in the direction opposite to the B-marked direction and is located at a prescribed evacuation position (wherein the optical axis is different from those of other lens groups).

When the pin2kphas come in contact with the bottom65hof the cam-shaped portion65k, the second lens group lens frame2kis slid and moved along the rotary shaft67ofFIG. 10in the direction opposite to the A-marked direction against the bias force of the torsion coil spring68, by the movement of the second lens group moving frame66toward the bottom board65.

Owing to the above, the second lens group lens frame2ktravels to the position where the optical axis is different from those of other lens groups, and the refracted state ofFIG. 9is attained.

To be more specific, the lens barrel of the second embodiment ensures that, in the process of changing from the protruded state to the retracted state, the second lens group lens frame2kto be shifted to the position where the optical axis is different from those of other lens groups is swung by being engaged with the cam-shaped portion3kk(the first engagement member) formed on the third lens group lens frame3k. After that, the lens frame2kis transferred to the cam-shaped portion65k(the second engagement member) formed on the bottom board65to be engaged therewith. The process of the retraction is now completed.

As described above, the engagement member is configured to be divided into different components, and is combined into a continuous configuration at the time of the retraction. This structure allows the height of individual engagement members (length in the direction of optical axis) to be reduced and the moldability to be enhanced. Further, the second engagement member exposed to spring bias force at the time of retraction can be formed on the bottom board of a fixed member as a short projection, and sufficient strength is provided. This structure provides an engagement section rigid enough to resist the spring bias force, and enhances operation reliability. Further, the engagement section can be made of resin, with the result that cost reduction is achieved.

The second embodiment has been described with reference to an example where a cam shape is also formed on the second engagement member formed on the bottom board65. Without the present invention being restricted thereto, it is also possible to make such arrangements that the cam is formed only on the first engagement member, and the second engagement member is provided only with a shape capable of catch.

The aforementioned embodiments have been described with reference to an example of the lens barrel for holding the image pickup optical system composed of three lens groups. Without being restricted thereto, the present invention is applicable to the lens barrel provided with at least two lens groups so that, at the time of retraction, one lens group is moved to the position where the optical axis is different from that of another lens group.

According to the embodiments of the present invention, a thin lens barrel of enhanced operation reliability is provided at a reduced cost.