Lens barrel suitable to be housed

A retractable lens barrel achieving thinning thereof in both directions parallel and perpendicular to a photographic optical axis. The lens barrel has a first lens and a second lens disposed in an inside thereof, and has a structure in which an optical axis of the second lens is aligned with an optical axis of the first lens when photographing, and the first lens is moved to a housed position and the second lens is moved in a retreating direction from the optical axis of the first lens when the first and second lenses are retracted. The lens barrel also has a holding member for holding the second lens and a rotation unit for rotating the holding member of the second lens, the holding member being rotated about a rotation shaft different from the optical axis of the first lens and perpendicular to the optical axes of the first and second lenses.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a retractable lens barrel, and more particularly, to a retractable lens barrel for use in a video camera, a still camera, or other image pickup apparatuses.

2. Description of the Related Art

In recent years, downsizing and thinning of a video camera and a still camera have been strongly required. In order to realize the downsizing and the thinning, it has been common to cause photographic lenses to retract to be housed in a thin body. However, recently, in order to realize further thinning, there has been proposed a first conventional art in which, when the photographic lenses are retracted, a certain unit of the photographic lenses is retreated so as to be deviated from an optical axis.

For example, the first conventional art of a still camera having a lens unit composed of three lenses (optical elements) L1, L2and L3as shown inFIGS. 10A and 10Bis disclosed. In the still camera, all the lenses are located on the same photographic optical axis Z1as shown inFIG. 10Ain a photographing condition, and when the lenses are retracted, the lens L2is retreated to a position different from that on the optical axis Z1as shown inFIG. 10B(for example, refer to Japanese Patent Application Laid-Open No. 2003-315861).

Further, a second conventional art in which a converter lens is retreated out of a photographic optical axis while rotating has also been disclosed (for example, refer to Japanese Patent Application Laid-Open No. S63-135908).

However, the still camera of the first conventional art is constructed so that an optical axis Z1′ of the lens L2after retreat and the photographic optical axis Z1are in parallel to each other.

Therefore, when a diameter of the lens L2is larger than a thickness thereof, there is a problem in that a size of a lens barrel of the lens L2in a direction perpendicular to the optical axis Z1, that is, a radial size of the lens barrel of the lens L2is increased.

Further, in the second conventional art, a rotation axis of the converter lens does not move though is perpendicular to the photographic optical axis, and accordingly, there is a problem in that a thickness of a lens barrel thereof in a direction of the photographic optical axis is increased.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a retractable lens barrel capable of achieving thinning thereof in both directions parallel and perpendicular to a photographic optical axis.

According to the present invention, there is provided a lens barrel, which is provided with a first lens and a second lens disposed in an inside thereof, and has a structure in which an optical axis of the second lens is matched with an optical axis of the first lens when photographing is performed, and the first lens is moved to a housed position thereof and the second lens is moved in a retreating direction thereof from the optical axis when the first lens and the second lens are retracted, the lens barrel including: a holding member for holding the second lens; and a rotation unit for rotating the holding member of the second lens. In the lens barrel, the holding member of the second lens is rotated about a rotation axis different from the optical axis and perpendicular to the optical axis and the optical axis of the second lens.

DESCRIPTION OF THE EMBODIMENTS

A description will be made below of an embodiment of the present invention with reference to the drawings.

A detailed description will be made of an embodiment mode of the present invention with reference to the drawings.

FIG. 1is a view schematically showing a construction and arrangement of a retractable lens barrel according to an embodiment in a photographing condition.

InFIG. 1, a retractable lens barrel100includes: a lens frame1which holds a lens11; a lens frame2which holds a lens12; and a supplementary lens frame3having a rotation shaft3ain a direction perpendicular to an optical axis OA1of a photographic optical system. Further, the retractable lens barrel100includes a fixed barrel4which is fixed and attached onto a camera body (not shown) by screws or the like and holds a third lens13.

The lens frame1has a projected portion1aabutting on the lens frame2while the lens11is being retracted, and in addition, the lens frame2has a circular hole2aengaged with the rotation shaft3aof the supplementary lens frame3. Thus, an optical axis of the lens2can be surely rotated in association with the retraction of the lens11.

Further, the retractable lens barrel100includes: a linear-moving barrel5not-rotatably held by the fixed barrel4; and a rotation barrel6of which inner diameter is rotatably engaged with and held by an outer diameter of the linear-moving barrel5.

A helicoid screw4ais formed on an inner circumference of the fixed barrel4, and a helicoid screw6ais formed on an outer circumference of the rotation barrel6. The rotation barrel6is screwed into the fixed barrel4by using the helicoid screws4aand6a.

Further, on the rotation barrel6, a gear interlocking with a publicly known lens barrel drive system (not shown) is formed. The rotation barrel6is rotated by the lens barrel drive system, and advances/retreats along the helicoid screw4aof the fixed barrel4in a direction parallel to a direction of the optical axis OA1. Specifically, when a motor of the above-mentioned lens barrel drive system is driven, the gear meshing with the motor is first driven. Further, the rotation barrel6meshing with the gear concerned starts to rotate when the gear is driven as described above.

Further, each of the lens frame1and the supplementary lens frame3has a projected portion (not shown), and the respective projected portions are fitted into cam grooves formed in the rotation barrel6and the linear-moving barrel5. Thus, when the rotation barrel6abuts on the projected portions of the lens frame1and the supplementary lens frame3, the lens frame1and the supplementary lens frame3move along the cam grooves of the rotation barrel6and the linear-moving barrel5. In terms of positions, the projected portions of the lens frame1and the supplementary lens frame3and the cam grooves of the rotation barrel6and the linear-moving barrel5are formed in accordance with operation timing of the lens frame1and the supplementary lens frame3in processes ofFIGS. 4,6,8and9, which are to be described later.

A cam pin1bis provided on the lens frame1, and a cam pin3bis provided on the supplementary lens frame3. The cam pins1band3bare inserted into the cam grooves of the linear-moving barrel5and the rotation barrel6. Thus, when the rotation barrel6rotates, the cam pins1band3bof the lens frame1and the supplementary lens frame3rotationally move along the cam grooves of the rotation barrel6and the linear-moving barrel5, the lens frame1and the supplementary lens frame3advance and retreat in the optical axis direction, and zooming of the optical system is performed.

In the photographing condition, as shown inFIG. 1, all the lenses11,12and13in the retractable lens barrel100are located on the same optical axis OA1. Meanwhile, the retractable lens barrel100is constructed so that, in a retracted condition, only the lens12among all the above-mentioned lenses11,12and13can retreat to a position different from that on the optical axis OA1as shown inFIG. 2.

Note that, though each of the lenses11,12and13has been described to be composed of a single lens for a purpose of simplifying the explanation, each of those may be an optical system composed of a plurality of lenses.

FIG. 4is a flowchart showing a procedure of a transition process from the photographing condition to the retracted condition, which is executed by the retractable lens barrel100.

InFIG. 4, first, it is determined whether or not there is a command to start the transition to the retracted condition in the photographing condition (Step S400). When there is the command to start the transition as a result of the determination (YES in Step S400), the publicly known lens barrel drive system (not shown) is activated, and the rotation barrel6rotates through the gear interlocking with the lens barrel drive system (Step S400a). After that, in association with the rotation of the rotation barrel6, first, only the lens frame1starts to retract into the retractable lens barrel100from the photographing condition (FIG. 3A), and moves in the direction parallel to the direction of the optical axis OA1(Step S401). Note that, in terms of the positions, the projected portion of the supplementary lens frame3and the cam grooves of the linear-moving barrel5and the fixed barrel6are formed so that the supplementary lens frame3does not abut on the fixed barrel6immediately after the rotation of the rotation barrel6. Therefore, at the timing when the lens frame1starts to retract in Step S401, the supplementary lens frame3does not move in parallel to the optical axis OA1(does not retract/project).

Subsequently, when the projected portion1aof the lens frame1abuts on the lens frame2(Step S402,FIG. 3B), the lens frame2starts to rotate about the rotation shaft3aby a pressing force applied from the lens frame1(Step S403,FIG. 3C). Thus, the lens frame2retreats out of the optical axis OA1. Note that, in terms of the positions, the projected portion of the supplementary lens frame3and the cam grooves of the linear-moving barrel5and the fixed barrel6are formed so that the supplementary lens frame3does not abut on the fixed barrel6even at the timing of Step S402. Therefore, at the timing when the lens frame2starts to rotate in Step S401, the supplementary lens frame3does not move.

When an optical axis OA2of the lens12becomes substantially perpendicular to the optical axis OA1by the above-mentioned rotation of the lens frame2(YES in Step S404,FIG. 3D), the lens frame2finishes rotating (Step S405). Thus, the lens frame2completely retreats out of the optical axis OA1.

At the point of time when the lens frame2finishes rotating, the projected portion of the supplementary lens frame3abuts on the fixed barrel6. Thus, the supplementary lens frame3starts to move in the direction parallel to the optical axis OA1along the cam grooves of the linear-moving barrel5and the fixed barrel6by a pressing force applied from the fixed barrel6. When the supplementary lens frame3starts to move, the lens frame2also starts to move in parallel to the optical axis OA1in a similar way (Step S407).

Subsequently, when the condition is shifted to the retracted condition (YES in Step S408,FIG. 3E), the rotation barrel6stops rotating (Step S409), and this process is ended.

According to the process ofFIG. 4, the projected portion1ais made to abut on the lens frame2when the lens11is retreated, and the lens frame2is thereby rotated and retreated out of the optical axis OA1. Thus, the lens frame1can be housed in a space of the lens frame2, and a thickness of the retractable lens barrel100in the direction parallel to the optical axis OA1can be reduced.

Further, the lens frame1is made to abut on the supplementary lens frame3after the lens12is retreated out of the optical axis OA1, and the supplementary lens frame3and the lens frame2are thereby moved in the direction parallel to the optical axis OA1. Thus, a thickness of the retractable lens barrel100in the direction perpendicular to the optical axis OA1can also be reduced.

FIG. 6is a flowchart showing a procedure of a modification example of the transition process ofFIG. 4.

A process ofFIG. 6is basically the same as the process ofFIG. 4. The same steps as the steps ofFIG. 4are denoted by the same reference symbols, a duplicate description will be omitted and portions different from those of the process ofFIG. 4will only be described below.

InFIG. 6, first, the publicly known lens barrel drive system (not shown) is activated by the command to start the transition to the retracted condition, and the rotation barrel6starts to rotate through the gear interlocking with the lens barrel drive system (Steps S400and S400a). After that, in association with the rotation of the rotation barrel6, only the lens frame1starts to retract into the retractable lens barrel100from the photographing condition (FIG. 5A) (Step S401).

Subsequently, when the projected portion1aof the lens frame1abuts on the lens frame2(Step S402,FIG. 5B), the lens frame2starts to rotate about the rotation shaft3a(Step S403,FIG. 5D). At this time, the projected portion of the supplementary lens frame3abuts on the fixed barrel6. Thus, the supplementary lens frame3starts to move in the direction parallel to the optical axis OA1along the cam grooves of the linear-moving barrel5and the fixed barrel6by the pressing force applied from the fixed barrel6. When the supplementary lens frame3starts to move, the lens frame2also starts to move in parallel to the optical axis OA1in a similar way (Step S602).

When the optical axis OA2of the lens12becomes substantially perpendicular to the optical axis OA1by the above-mentioned rotation of the lens frame2, the lens frame2finishes rotating (Steps S404and S405,FIG. 5D). After that, when the condition is shifted to the retracted condition (Step S408,FIG. 5E) by the movements of the lens frame2and the supplementary lens frame3in parallel to the optical axis OA1, which are subsequently performed, the rotation barrel6stops rotating (Step S409), and this process is ended.

According to this modification example, at the same time when the lens frame2is rotated to retreat the lens12out of the optical axis OA1in the case of retreating the lens11, the lens frame2and the supplementary lens frame3are moved in parallel to the optical axis OA1. Accordingly, the lens11can be retracted more quickly.

FIGS. 7A,7B,7C,7D,7E and7F are views each showing the transition of the modification example of the retractable lens barrel100ofFIG. 1from the photographing condition to the retracted condition.

A retractable lens barrel100aofFIGS. 7A,7B,7C,7D,7E and7F is basically the same in construction as the above-mentioned retractable lens barrel100. The same constituents as those of the retractable lens barrel100are denoted by the same reference symbols, a duplicate description will be omitted, and a description will be made below of different constituents.

The retractable lens barrel100ais different from the retractable lens barrel100only in that the lens frame2has a long hole72ain place of the circular hole2a(FIG. 1) engaged with the rotation shaft3aof the supplementary lens frame3.

FIG. 8is a flowchart showing a procedure of a transition process from the photographing condition to the retracted condition, which is executed by the retractable lens barrel100aofFIGS. 7A,7B,7C,7D,7E and7F.

The process ofFIG. 8is basically the same as the process ofFIG. 4. The same steps as the steps ofFIG. 4are denoted by the same reference numerals, a duplicate description will be omitted and portions different from those of the process ofFIG. 4will only be described below.

InFIG. 8, first, the publicly known lens barrel drive system (not shown) is activated by the command to start the transition to the retracted condition, and the rotation barrel6rotates through the gear interlocking with the lens barrel drive system (Steps S400and S400a). After that, in association with the activation of the lens barrel drive system, the lens frame2moves in the direction perpendicular to the optical axis OA1(Step S801,FIG. 7B). Thus, an optical axis OA72of the lens12becomes an axis which is not coaxial with and is positionally different from the optical axis OA1immediately after the command to start the transition while being parallel thereto.

Subsequently, first, only the lens frame1starts to retract into the retractable lens barrel100(Step S401,FIG. 7C). After that, the projected portion1aof the lens frame1abuts on the lens frame2, and the lens frame2thereby starts to rotate (Steps S402and S403,FIG. 7D).

Next, at the point of time when the optical axis OA2of the lens12becomes substantially perpendicular to the optical axis OA1, and the lens frame2finishes rotating (Steps S405and S406,FIG. 7E), the lens frame2and the supplementary lens frame3start to move in parallel to the optical axis OA1(Step S407). After that, when the condition is shifted to the retracted condition (Step S408,FIG. 7F), the rotation barrel6stops rotating (Step S409), and this process is ended.

According to the process ofFIG. 8, the lens frame2first moves perpendicularly to the optical axis OA1(Step S801), and accordingly, a rotation radius of the lens frame2can be reduced, leading to space saving.

Note that timing when the rotation barrel6starts to move in parallel to the optical axis OA1in this process may be not the point of time when the lens frame2finishes rotating but the point of time when the projected portion1aof the lens frame1abuts on the lens frame2.

In this case, as shown inFIG. 9, between the process of Step S400aand the process of Step S401in the flowchart ofFIG. 6, a process of Step S801of moving the lens frame2perpendicularly to the optical axis OA1is performed.

Thus, the lens frame2first moves perpendicularly to the optical axis OA1, and after that, the lens frame2is rotated to retreat the lens12out of the optical axis OA1in the case of retreating the lens11. Simultaneously, the lens frame2and the supplementary lens frame3are moved in parallel to the optical axis OA1. Thus, the lens11can be retracted more quickly.

According to the present invention, by the rotation shaft arranged out of the photographic optical axis and perpendicular to the photographic optical axis and to the optical axis of the second lens disposed in the inside of the retractable lens barrel, the optical axis of the second lens is rotated so that the second lens is moved in parallel to the photographic optical axis. Accordingly, the reduction in thickness of the retractable lens barrel in both of the directions parallel and perpendicular to the photographic optical axis can be achieved.

This application claims the benefit of Japanese Patent Application No. 2005-348025, filed on Dec. 1, 2005, which is hereby incorporated by reference herein in its entirety.