JP4411425B2 - Zoom lens barrel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens barrel used for a photographic camera, an electronic still camera, and the like, and more particularly to a zoom lens barrel that moves a lens to a storage position when retracted.
[0002]
[Prior art]
Most cameras using a zoom lens camera have a lens retracting mechanism, and when not in use, the lens barrel is housed in the camera body for portability. When a lens barrel extension signal is obtained in conjunction with the turning on of the power source switch, the lens barrel is extended from the retracted position to the projecting position, and a zooming operation can be performed. In addition, when a lens barrel retraction signal is obtained in conjunction with an operation of turning off the power switch, the lens barrel is retreated from the protruding position to the retracted position.
[0003]
When the lens barrel is retracted, the zoom lens group and the focus lens group in the lens barrel are moved close to each other by guide means such as a cam barrel and a helicoid mechanism in order to minimize the storage space. The In order to simplify the structure of the lens barrel, the guide means for moving each lens group within the zooming range according to the zooming operation has a function of moving each lens group to the storage position, and the lens group at the protruding position. There is known a method of moving each lens group to the storage position all at once while moving the lens to the retracted position. Also, a method for providing a retracting guide means different from the guide means for moving each lens group within the zooming range, and switching and using them is known from Japanese Utility Model Laid-Open No. 58-40735.
[0004]
[Problems to be solved by the invention]
When the lens barrel is retracted, the guide means for moving each lens group within the zoom range moves the lens group to the storage position because it only needs to drive a common motor during zooming or retracting. There is an advantage that the basic configuration can be simplified, but if you try to move each lens group in the variable magnification range all the way to the storage position without interfering with each other by interlocking with the retracted lens barrel, the structure of the guide means will be Easy to make complicated. Further, when the cam cylinder is used as the guide means, the cam groove cannot be tilted so much that the cam cylinder has to be rotated at a large rotation angle. Further, those using the zooming guide means and the retracting guide means require a separate motor for each drive, and an increase in cost cannot be avoided.
[0005]
The present invention has been made in consideration of the above-mentioned circumstances, and these lens groups are moved to the storage position without interfering with each other by using guide means for moving the lens groups within the zooming range, and the structure is simple. An object of the present invention is to provide a zoom lens barrel that can be manufactured at a low cost.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the zoom lens barrel of the present invention, a first lens holding frame that holds a first lens group among a plurality of lens groups constituting a photographing optical system; and the first lens holding the third lens group are arranged on the imaging surface side of the second lens group; the second lens holding frame and which holds the second lens group are arranged on the imaging surface side of the group and has a third lens holding frame to move in the optical axis direction while being guided by the guide means provided in the second lens holding frame; the first, and the most image plane side of the second lens holding frame The zoom lens moves from the close storage position to the zooming guide area that extends toward the subject through the storage guide area, and the first and second lens holding frames are arranged to have different intervals in the zooming guide area. is moved to the first moving means performs magnification; the second lens holding frame Digit the third lens holding frame using the drive motor from the in-focus initial position away from the second lens holding frame is moved toward the second lens holding frame and the second moving means for focusing; wherein the first moving means, said first and second lens holding frame to move from zooming guiding region to the boundary between the housing guiding zone when stored, temporarily stops the movement reaches the boundary In addition, the second moving means moves the third lens holding frame to a storage preliminary position that brings the third lens holding frame closer to the second lens holding frame by driving the motor while the movement of the first moving means is stopped. is allowed, then to move the first while moving to resume to approximate the second lens holding frame to the first lens holding frame, and the second lens holding frame of the first moving means to the storage position It is a thing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIGS. 1 to 3, the zoom lens 10 of the camera is composed of three groups of first to third lens groups 11 to 13 in order from the subject side, and holds these lens groups 11 to 13. Further, in order to move in the direction of the optical axis O, a fixed cylinder 14, a cam cylinder 15, a first lens moving cylinder 16, a second lens holding frame 17, and a third lens holding frame 18 are used.
[0009]
The first lens group 11 is fixed to the first lens moving cylinder 16, and the second lens group 12 is fixed to the second lens holding frame 17. A straight guide opening 19 extending in parallel with the optical axis O is formed in the fixed cylinder 14. A first cam groove 20 for moving the first lens group 11 and a second cam groove 21 for moving the second lens group 12 are formed on the inner periphery of the cam cylinder 15, respectively.
[0010]
A variable power motor 22 is fixed outside the fixed cylinder 14. The zooming motor 22 rotates the cam cylinder 15 about the optical axis O. The first lens moving cylinder 16 is provided with a first cam follower 23 that engages with the first cam groove 20 through the rectilinear guide opening 19 at a position that divides the outer periphery into three parts. The second lens holding frame 17 is provided with a second cam follower 24 that engages with the second cam groove 21 through the rectilinear guide opening 19 at a position that divides the outer periphery into three parts. The first and second cam grooves 20 and 21 and the rectilinear guide opening 19 move the first lens moving cylinder 16 and the second lens holding frame 17 in the direction of the optical axis O by the rotation of the cam cylinder 15.
[0011]
The first lens moving cylinder 16 moves between a position protruding from the fixed cylinder 14 toward the subject side and a storage position stored inside the fixed cylinder. Although not shown, the outer periphery of the fixed tube 14 is covered with the camera body, and the first lens moving tube 16 is stored in the camera body when moved to the storage position. Further, the second lens holding frame 17 changes the interval with respect to the first lens moving cylinder 16 and comes closest to the storage position. Reference numeral 26 denotes an imaging position.
[0012]
The second lens holding frame 17 is provided with a guide rod 27, and the third lens holding frame 18 is provided with a bearing portion 28 that engages with the guide rod 27. The guide means including the guide rod 27 and the bearing portion 28 supports the third lens holding frame 18 so as to be movable in the direction of the optical axis O with respect to the second lens holding frame 17.
[0013]
A focusing motor 30 is fixed to the second lens holding frame 17. A feed screw 31 is attached to the shaft of the focusing motor 30. The feed screw 31 is screwed into a screw portion 32 provided on the third lens holding frame 18. As a result, the third lens holding frame 18 changes the interval with respect to the second lens holding frame 17 and comes closest to the storage position and the storage preliminary position. The storage position of the third lens group 13 is an absolute position closest to the second lens group 12 when the zoom lens 10 is in the retracted position. In addition, the storage preliminary position of the third lens group 13 is a relative position closest to the second lens group 12 when the zoom lens 10 is not in the retracted position. The third lens group 13 is a focus lens.
[0014]
The movement positions of the first and second lens groups 11 and 12 are detected by a cam barrel rotation position detector 29 . The cam cylinder rotation position detection unit 29 detects the movement position of the first and second lens groups 11 and 12 by detecting the rotation position of the cam cylinder 15. The cam cylinder rotational position detecting unit 29, the outer periphery of the cam barrel 15, and the code plate 29 a provided in along the circumferential direction about the optical axis O, sliding to slide code plate 29 a It is composed of a child 29 b, sent from the code plate 29 a via the slider 29 b in the control unit 34 reads the code corresponding to the rotational position of the cam barrel 15. The control unit 34 identifies the zoom position corresponding to the movement position of the first and second lens groups 11 and 12 based on the signal obtained from the cam barrel rotation position detection unit 29 .
[0015]
The focusing motor 30 is a pulse motor. The control unit 34 drives the focusing motor 30 during the shooting preparation operation to move the third lens group 13 from the storage preliminary position to the initial focus position. Further, during the focusing operation, a pulse signal corresponding to the focusing position determined by the zoom position and the subject distance is sent to the driver 35 to drive the focusing motor 30 in a predetermined rotation direction, so that the third lens The group 13 is moved from the initial focus position to the in-focus position. Further, the controller 34 drives the focusing motor 30 after the exposure is completed to return the third lens group 13 from the in-focus position to the initial focus position. Note that the shooting preparation operation is an operation for changing the camera from the non-use state to the use state. Moreover, the operation | movement made into the reverse state is set as a collapsing operation.
[0016]
A power switch 37, a shutter button 38, a zoom lever 39, and the like provided outside the camera are connected to the control unit 34. In a non-use state, the zoom lens 10 is in a retracted state, and in this state, the first to third lens groups 11 to 13 are in a state of being closest to each other when in the retracted position. . When the power switch 37 is turned on, the camera is set from the non-use state to the use state. In the use state, the first lens group 11 is extended from the fixed cylinder 14 toward the subject side, and the zoom lens is set at the wide end.
[0017]
The zoom lever 39 is a lever that is operated in a seesaw manner, for example, and either the tele end or the wide end is operated. The control unit 34 drives the zooming motor 22 in the rotational direction in response to the operation of one of the zoom levers 39 by sending a drive signal via the driver 40.
[0018]
FIG. 4 shows the movement of the zoom lens 10 with respect to the rotational position of the cam cylinder 15. The zoom lens 10 is moved between the retracted position and the wide position. The tele position is set between the retracted position and the wide position. When the zoom lens 10 is in the retracted position, the rotational position of the cam cylinder 15 is the initial position. The rotation of the cam cylinder 15 in the feeding direction is a direction from the initial position toward the terminal position. When the cam cylinder 15 is at the initial position, the zoom lens 10 is set at the retracted position, and when the cam cylinder 15 is at the end position, it is set at the wide position.
[0019]
The rotation area of the cam cylinder 15 is composed of a zooming area and a storage area. The zooming area is the rotation area of the cam cylinder 15 at the time of zooming, and the storage area is the area where the cam cylinder 15 rotates during the shooting preparation operation or the retraction operation. In the zoom range, the shapes of the first and second cam grooves 20 and 21 are determined in order to move the first and second lens groups 11 and 12 in the direction of the optical axis O so that the distance between them is different. It has been. As a result, when the cam cylinder 15 is rotated in the zooming range between the tele position and the wide position, the focal length of the zoom lens 10 changes continuously.
[0020]
In the storage area, the shapes of the first and second cam grooves 20 and 21 are determined so that the first and second lens groups 11 and 12 set at the zoom position are moved to the storage position, respectively. Then, after the third lens group 13 is moved to the storage preliminary position H by driving the focusing motor 30, it is moved together with the second lens group 12 and set to the storage position. The timing for moving the third lens group 13 to the storage preliminary position H is set when the cam cylinder 15 is rotated to the rotation position F in the storage area. The rotation position F may be an arbitrary position in the storage area. Further, the zoom position may be the boundary between the zooming area and the storage area, that is, the tele position of the zoom lens 10.
[0021]
During the collapsing operation, the zooming motor 22 is intermittently driven, and the focusing motor 30 is driven while the driving is stopped. That is, as shown in FIG. 5, the controller 34 temporarily stops driving the zooming motor 22 from time t1 to time t4 when the cam cylinder 15 reaches the rotational position F. Then, while the drive of the zooming motor 22 is stopped, the focusing motor 30 is driven by a predetermined pulse. As a result, the third lens group 13 is moved from the initial focus position I to the storage preliminary position H between time t2 and time t3.
[0022]
On the other hand, the zooming motor 22 is driven again toward the initial position at the time t4 when a predetermined time has elapsed from the time t3 when the driving of the focusing motor 30 is stopped, and the time when the cam cylinder 15 reaches the initial position. The driving is stopped at t5. Thereby, the retracting operation is completed. At this time, the first lens group 11 and the second lens group 12 are located at the storage positions J and K, respectively. The third lens group 13 moves together with the second lens group 12 and is located at the storage position L.
[0023]
As in the case of the retracting operation, during the photographing preparation operation, when the cam cylinder 15 reaches the rotational position F, the driving of the zooming motor 22 is temporarily stopped, and the focusing motor 30 is moved by a certain amount of pulses while the driving is stopped. And the third lens group 13 is moved from the storage preliminary position H to the focus initial position I. Then, the third lens group 13 is moved together with the second lens group 12 by re-driving the zooming motor 22 thereafter, and the focus initial position I is changed from the focus initial position I at the tele position to the wide position. Move to position M.
[0024]
Here, the initial focus position of the third lens group 13 is a position that is set when performing the focusing operation, and this position moves together with the second lens group 12, and therefore varies depending on the zoom position. FIG. 5 is a position in the variable magnification region on the line indicated by reference numeral 13 in FIG. For example, the initial focus position at the tele position is the position indicated by the symbol I in the figure, and the initial focus position at the wide position is the position indicated by the symbol M. The shape of the second cam groove 21 is such that the position of the second lens group 12 on the optical axis O is the same when the cam cylinder 15 is rotated to the tele position and when it is rotated to the rotation position F. Is decided. Therefore, the position of the third lens group 13 on the optical axis O at the tele position is also the same position as the initial focus position I when the cam cylinder 15 is rotated to the rotation position F.
[0025]
Next, the operation of the above embodiment will be described. When the camera is not used, the zoom lens 10 is in the retracted position. In the retracted position, as shown in FIG. 5, the first lens moving cylinder 16 approaches the storage position J where the fixed lens 14 is retracted, and the second lens holding frame 17 approaches the first lens moving cylinder 16. In the storage position K, the third lens holding frame 18 is further set in the storage position L close to the second lens holding frame 17.
[0026]
To put the camera into use, the power switch 37 is turned on. In response to the power switch 37 being turned on, the control unit 34 drives the zooming motor 22 to rotate forward. The drive of the zooming motor 22 is transmitted to the cam cylinder 15. As a result, the cam cylinder 15 rotates toward the end position. When the cam cylinder 15 rotates, the first lens moving cylinder 16 and the second lens holding frame 17 are extended toward the subject side by the action of the first and second cam grooves 20 and 21 and the rectilinear guide opening 19, respectively. Then, the third lens holding frame 18 moves together with the second lens holding frame 17.
[0027]
When the control unit 34 monitors the signal from the cam barrel rotational position detection unit 29 and identifies that the cam barrel 15 has reached the rotational position F, the control unit 34 temporarily stops the driving of the zooming motor 22. At this time, time t4 shown in FIG. 5 is reached. Thereafter, a signal for a predetermined pulse is sent at a time t3 after the elapse of a predetermined time after the driving of the zooming motor 22 is stopped, and the focusing motor 30 is driven. The driving of the focusing motor 30 is transmitted to the screw portion 32 of the third lens holding frame 18 via the feed screw 31. The third lens holding frame 18 moves to the initial focus position I at time t2 when driving for a predetermined pulse is completed. The control unit 34 measures time with a built-in timer circuit.
[0028]
At time t <b> 1 after the elapse of a predetermined time after the driving of the focusing motor 30 is stopped, the control unit 34 drives the zooming motor 22 to rotate forward again. Then, when it is identified that the cam cylinder 15 has reached the terminal rotation based on the signal from the cam cylinder rotation position detection unit 29 , the control unit 34 stops the driving of the variable power motor 22. As a result, the zoom lens 10 is set to the wide position at time t0, and the camera is in use. At this time, the third lens group 13 is located at the initial focus position M at the wide position shown in FIG.
[0029]
When taking a picture, the zoom lever 39 is operated to perform zooming. At the time of this operation, the control unit 34 drives the zooming motor 22 for the time corresponding to the operation in the rotation direction according to the operation of the tele end or wide end lever. As a result, the cam cylinder 15 is rotated within the zooming range, and the zoom lens 10 is set at a desired zooming position. At this time, the third lens group 13 moves together with the second lens group 12 and is set at the initial focus position corresponding to the zoom position.
[0030]
In response to the half-pressing operation of the shutter button 38, the control unit 34 performs distance measurement and photometry. Among these, the focus position of the third lens group 13 is specified from the subject distance obtained from the distance measurement result and the zoom position at that time. Note that the focus position is stored in advance in the memory 41 as a moving amount of the third lens group 13, the amount of movement determined for each object distance is different at each zoom position.
[0031]
The control unit 34 drives the focusing motor 30 by sending a pulse signal corresponding to the read movement amount to the driver 35. As a result, the third lens holding frame 18 moves in the direction approaching the second lens holding frame 17 from the initial focus position corresponding to the zoom position at that time, and within the focusing range G shown in FIG. Move to the in-focus position corresponding to the subject distance. Thereby, the focus of the zoom lens 10 is focused on the subject. Then, the shutter button 38 is fully pressed subsequent to the half-pressing operation, so that the shutter mechanism is operated with exposure according to photometry. Then, after the exposure operation is completed, the focusing motor 30 is driven to return the third lens group 13 to the initial focus position corresponding to the previous zoom position. The focusing operation may be performed by fully pressing the shutter button 38, and the exposure operation may be performed after a predetermined time has elapsed from the completion of the focusing operation.
[0032]
After the photographing is completed, the power switch 37 is turned off so that the camera is not used. In response to the power switch 37 being turned off, the control unit 34 drives the zooming motor 22 in the reverse direction. By this driving, the cam cylinder 15 is rotated toward the initial position which is the feeding direction. Then, at time t1 when the rotational position of the cam cylinder 15 reaches the rotational position F, the driving of the zooming motor 22 is temporarily stopped. Then, the focusing motor 30 is driven by a predetermined pulse at a time t2 after the elapse of a predetermined time after the drive of the zooming motor 22 is stopped. As a result, the third lens group 13 moves in a direction approaching the second lens group 12. At time t3, the driving of the focusing motor 30 is stopped, and the third lens group 13 is set at the storage preliminary position H.
[0033]
At time t4 after the elapse of a predetermined time since the driving of the focusing motor 30 is stopped, the reverse rotation driving of the zooming motor 22 is resumed. As a result, the cam cylinder 15 is rotated again toward the initial position, and the driving of the variable power motor 22 is stopped at time t5 when the cam cylinder 15 reaches the initial position. As a result, the first and second lens groups 11 and 12 are set at the storage positions J and K, respectively. Then, the third lens group 13 moves together with the second lens group 12 and is set at the storage position L.
[0034]
As described above, during the retracting operation, the driving of the zooming motor 22 is temporarily stopped when the cam cylinder 15 is within the storage area, and the focusing motor 30 is driven during the stop to store the third lens group 13. Since the second lens group 12 is moved to the storage position K before the third lens group 13 is moved to the storage preliminary position H, for example, the third lens group is moved to the preliminary position H. It is possible to reliably prevent inconvenience that 13 interferes with an aperture or the like disposed at the rear end of the lens barrel.
[0035]
Here, the first lens holding frame of the first lens moving cylinder 16 of the above embodiment the present invention, also, the second lens holding frame 17 to the second lens holding frame of the present invention, the third lens holding frame 18 Each corresponds to a third lens holding frame of the present invention . Further, the first guiding means of the present invention is used in the zooming motor 22, the first and second cam grooves 20, 21, the first and second cam followers 23, 24, the linear guide opening 19 and the like of the above embodiment, The second guide means corresponds to the focusing motor 30, the feed screw 31, and the like.
[0036]
In the above embodiment, the variable magnification moving mechanism is a cam mechanism, but the present invention is not limited to this, and a helicoid mechanism may be used. Further, although the screw 31 sends a focus moving mechanism may be used a cam mechanism or a helicoid mechanism instead.
[0037]
In the above embodiment, the zoom position is identified by the rotational position of the cam cylinder 15, but the present invention is not limited to this, and may be identified by the rotation amount of the cam cylinder 15. Alternatively, the second lens group 11 or 12 may be identified by the moving amount or the moving position. In these cases, the third lens group 13 is moved to the storage preliminary position H based on the signal obtained from the means for identifying the zoom position.
[0038]
In the above embodiment, the zoom lens has a three-group configuration. However, the present invention is not limited to this, and a two-group configuration or a four-group or more configuration may be used. In addition, the first to third lens groups 11 to 13 are arranged in order from the subject side. However, the present invention is not limited to this order. For example, the third lens is arranged on the subject side of the second lens group 12. Group 13 may be arranged. Furthermore, the present invention can be applied not only to a zoom lens camera but also to a bifocal camera that switches to a tele position, a wide position, and a retracted position, for example. Furthermore, although the tele position is set between the retracted position and the wide position, it is also possible to set the wide position between the retracted position and the tele position. In this case, the boundary between the zooming guide area and the storage guide area is the wide position.
[0039]
In the above-described embodiment, the lens barrel extension or the extension signal is identified in response to the operation of the power switch 37. However, the present invention is not limited to this, and for example, the photographing lens is protected. A protective cover may be provided on the front surface of the camera so as to be freely opened and closed, and configured to be configured so that the lens barrel feeding or feeding signal is identified in response to the opening and closing operation of the protective cover.
[0040]
Furthermore, the present invention can be applied to, for example, an electronic still camera in addition to a photographic camera. In this case, instead of the distance measuring mechanism, a contrast method for determining whether or not the image is in focus using the contrast of the image obtained from the CCD is used, and the focusing operation is performed based on the signal obtained from this method. You may do it.
[0041]
Furthermore, in the above embodiment, also intermittently driving the same in zooming motor 22 and when the retracting operation when the photographic preparation operation, the third by driving the focusing motor 30 during the driving stop The lens group 13 is moved to the focus initial position M, but instead, for example, the cam cylinder 15 is rotated to the end position without stopping the driving of the zooming motor 22 during the shooting preparation operation, During the driving, the focusing lens 30 may be driven to move the third lens group 13.
[0042]
As another example, as shown in FIG. 6, during the photographing preparation operation, the zooming motor 22 is driven from time t6 to time t7 to rotate the cam cylinder 15 all the way to the end position, and thereafter zooming is performed. The third lens group 13 may be moved to the initial focus position M by driving the focusing motor 30 at time t8 after a predetermined time has elapsed after the driving of the driving motor 22 is stopped. In this way, the camera can be quickly put into use by continuing to drive the zooming motor 22 only during the shooting preparation operation and rotating the cam cylinder 15 all the way to the end position.
[0043]
【The invention's effect】
In the zoom lens system of the present invention as described above, the first guiding means to guide the first and second lens holding frame to the boundary between the accommodating guide zone, temporarily stop the guide reaches the boundary, the first When the guide of the first guide means is stopped, the second guide means moves the third lens holding frame to the storage preliminary position for approaching the second lens holding frame, so when the lens group moves to the storage position. Interference can be reliably prevented. In addition, it is not necessary to provide a separate mechanism for moving to the storage position as described in the prior art, and therefore, the camera can be reduced in cost and size.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a zoom lens using a lens moving device of the present invention, showing a state of a retracted position.
FIG. 2 is a cross-sectional view showing a zoom lens at a tele position.
FIG. 3 is a cross-sectional view showing a zoom lens at a wide position.
FIG. 4 is an explanatory diagram showing the amount of movement of the zoom lens in the optical axis direction with respect to the amount of rotation of the cam cylinder.
FIG. 5 is an explanatory diagram showing driving of a zooming and focusing motor during a retracting operation.
FIG. 6 is an explanatory diagram of another example in which the cam cylinder is rotated all the way to the end position during the shooting preparation operation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Zoom lens 11 1st lens group 12 2nd lens group 13 3rd lens group 16 1st lens moving cylinder 17 2nd lens holding frame 18 3rd lens holding frame 14 Fixed cylinder 15 Cam cylinder 22 Zooming motor 30 Focusing motor
29 cam cylinder rotation position detector

Claims (1)

In a zoom lens barrel having a plurality of lens groups constituting a photographing optical system,
A first lens holding frame that holds a first lens group of the plurality of lens groups;
A second lens holding frame for holding a second lens group disposed on the imaging surface side of the first lens group;
Holds the third lens group are arranged on the imaging surface side of the second lens group, the second is guided to move in the optical axis direction guide means provided in the second lens holding frame Three lens holding frames;
It is moved to said first, and zoom guiding zone for feeding toward the object side through the accommodating guide zone of the second lens holding frame most gather the image plane side storage position, in the magnification-varying guiding region First moving means for performing zooming by moving the first and second lens holding frames so that the distance between them is different;
Second moving means for focusing by moving the third lens holding frame with respect to the second lens holding frame using driving of a motor fixed to the second lens holding frame. ,
It said first moving means, said first and second lens holding frame when stored moved from zooming guiding region to the boundary between the accommodating guide zone, with temporarily stopping the movement reached the boundary,
The second moving means moves the third lens holding frame to a storage preliminary position for approaching the second lens holding frame by driving the motor while the movement of the first moving means is stopped.
Thereafter, characterized in that moving the first while moving to resume to approximate the second lens holding frame to the first lens holding frame, and the second lens holding frame of the first moving means to the storage position Zoom lens barrel.

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