JP2007156068A - Lens barrel and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens barrel, in particular, of a thin type, which has a low-cost lens drive unit, and with which gradual continuous change of a focal distance is made possible and also a sufficient amount of focusing movement and resolution can be secured by a single drive source; and to provide an imaging apparatus. <P>SOLUTION: The lens barrel includes a plurality of lens groups for guiding subject light, and the lens drive unit having: a single motor for moving two of the plurality of lens groups in the direction of an optical axis; and a lead screw to be rotated linked with the rotation of a motor, one of the two movable lens groups being moved with the rotation of the lead screw and the other lens group being moved having a predetermined amount of play with respect to the rotation of the lead screw. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lens barrel including a lens driving device configured to move two lens groups with a single driving source, and an imaging device including the lens barrel.

  2. Description of the Related Art Conventionally, cameras equipped with a variable focal length photographing lens (hereinafter also referred to as a zoom lens) are commercially available. The zoom lens is configured to change the focal length (zooming) by moving a plurality of lens groups constituting the optical system to a desired position along the optical axis and changing the interval therebetween.

  There are roughly two types of methods for moving a plurality of lens groups along the optical axis. The lens frame is engaged with the linear guide, and the lens frame is moved linearly by rotating the cam barrel, and the optical axis is used. A shaft is arranged almost in parallel, and this shaft is used as a guide shaft for rectilinear guide. A sleeve through which the guide shaft passes is formed in the lens frame, and the lens frame is slid directly along the guide shaft using a motor and a lead screw. There is something that lets you move straight ahead.

  For the former to move the lens frame linearly by rotating the cam cylinder, cam grooves corresponding to the zooming area and the focusing area are alternately provided in the cam cylinder that moves the two lens groups. There is a so-called step zoom that performs focusing.

  The latter, which uses the lead screw to move the lens frame directly along the guide shaft, has a simple structure, so it is often used for lens barrels that do not require a retracting mechanism. There are a lead screw for moving one lens group and a lead screw for moving the other lens group as a driving device that moves the lens frame directly using, from one lead screw to the other lead screw. A lens driving device that transmits power using gears and a belt and moves two lens groups with one motor is known (for example, see Patent Document 1).

In addition, the two shafts with cam grooves are arranged in series with play in the rotational direction, and the lens group that engages the cam grooves of each shaft is driven to perform zooming and focusing with a single motor There is known a lens barrel that performs the above (see, for example, Patent Document 2).
JP 2001-124974 A JP-A-4-317015

  However, what is called step zoom above is one in which a plurality of lens groups can be moved along the optical axis by a single motor to perform zooming and focusing. However, the focal length changes stepwise during zooming. As a result, the focal length cannot be changed continuously in small increments. Further, since a cylindrical cam cylinder is disposed outside the lens group, there is a problem that the diameter is increased in thickness and size.

  In addition, the lens driving device described in Patent Document 1 can be applied to zooming but cannot perform focusing. Therefore, a driving source such as a motor for focusing is separately required and applied to a lens barrel. In addition to the cost increase, there is a problem of increasing the size.

  Furthermore, in the configuration of the lens barrel described in Patent Document 2, the play is an amount within one rotation of the shaft, and it is difficult to sufficiently secure the movement amount and accuracy (resolution) of the lens group for focusing. is there.

  In view of the above problems, the present invention enables a continuous change in focal length in small increments with a single drive source and can secure a sufficient amount of focusing movement and resolution. It is an object of the present invention to obtain a lens barrel and an imaging device provided with a low-cost lens driving device.

  The above object is achieved by the invention described below.

  1. A plurality of lens groups for guiding subject light, a single motor for moving two lens groups of the plurality of lens groups in the optical axis direction, and rotated in conjunction with the rotation of the motor. One of the two lens groups that is moved and moves with the rotation of the lead screw, and the other lens group has a predetermined play amount with respect to the rotation of the lead screw. A lens barrel comprising a lens driving device that moves with the lens.

  2. A female screw member threadably engaged with the lead screw, and a predetermined play between the female screw member and a lens frame that holds a lens group that moves with a predetermined play amount with respect to the rotation of the lead screw; 2. The lens barrel according to 1, wherein an amount is provided.

  3. The lens frame that holds the lens group that moves with a predetermined play amount with respect to the rotation of the lead screw includes a mechanism that applies a frictional force to a fixed member. 2. The lens barrel according to 2.

  4). A single detection unit that detects a position of the lens group that is moved by the lens driving device; and the detection unit determines a position of the lens group that moves with a predetermined play amount with respect to the rotation of the lead screw. The lens barrel according to any one of 1 to 3, wherein the lens barrel is detected.

  5. The lens group that moves with the rotation of the lead screw performs zooming and focusing by movement, and the lens group that moves with a predetermined play amount with respect to the rotation of the lead screw performs zooming by movement. The lens barrel according to any one of 1 to 4, which is characterized.

  6). The lens barrel according to any one of claims 1 to 5, wherein the optical system composed of the plurality of lens groups does not change its overall length.

  An imaging apparatus comprising the lens barrel according to any one of 7.1 to 6.

  According to the present invention, a low-cost lens with a thin lens barrel that can change the focal length in small increments with a single driving source and can secure a sufficient amount of focusing movement and resolution. It is possible to obtain a lens barrel and an imaging device that include a driving device.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto.

  FIG. 1 is a diagram illustrating an example of an internal arrangement of main constituent units of a camera 100 that is an example of an imaging apparatus including a lens barrel according to the present embodiment. FIG. 3 is a perspective view of the camera 100 as viewed from the subject side.

  As shown in the figure, in the camera 100, a lens barrel 50 according to the present invention including a foldable imaging optical system capable of zooming is arranged vertically on the right side as shown in the figure, and an opening 51 takes in a subject light flux. Is arranged. The opening 51 is provided with a lens barrier (not shown) that is in an open state that exposes the opening 51 and a closed state that covers the opening 51.

  Reference numeral 52 denotes a flash light emission window. Reference numeral 53 denotes a flash unit including a reflector, a xenon tube, other main capacitors, a circuit board, and the like disposed behind the flash light emission window. Reference numeral 54 denotes a card-type image recording memory. A battery 55 supplies power to each part of the camera. The image recording memory 54 and the battery 55 can be inserted and removed from a lid (not shown).

  A release button 56 is disposed on the upper surface of the camera. When the first button is pushed, a shooting preparation operation of the camera, that is, a focusing operation and a photometric operation are performed, and a shooting exposure operation is performed by pushing the second button. A main switch 57 is a switch for switching the camera between an operating state and a non-operating state. When switched to the operating state by the main switch 57, the lens barrier (not shown) is opened and the operation of each part is started. When the main switch 57 is switched to the non-operating state, the lens barrier (not shown) is closed and ends the operation of each unit.

  On the back side of the camera, an image display unit 58 configured by an LCD, an organic EL, or the like and displaying an image and other character information is disposed. Although not shown, a zoom button for zooming up and down, a playback button for playing back a captured image, a menu button for displaying various menus on the image display unit 58, and a desired function are selected from the display. An operation member such as a selection button is arranged.

  Although not shown, each part is connected between these main constituent units and a circuit board on which various electronic components are mounted is arranged to drive and control each main constituent unit. Yes. Similarly, although not shown, an external input / output terminal, a strap attaching portion, a tripod seat, and the like are provided.

  FIG. 2 is a cross-sectional view showing a foldable imaging optical system capable of zooming, which is included in the lens barrel 50 according to the present embodiment. This figure is a cross-sectional view taken along a plane including two optical axes before and after bending.

  As shown in the figure, OA is the optical axis before bending, and OB is the optical axis after bending. Reference numeral 1 denotes a first lens group. The first lens group 1 includes a prism 11 that is a reflection member that bends the optical axis OA in a substantially right angle direction, a lens 11 that is disposed toward the subject with the optical axis OA, and a prism 12. The lens 13 is disposed with the optical axis OB bent by the optical axis as the optical axis. The first lens group 1 is a lens group fixed to the main body 9.

  Reference numeral 2 denotes a second lens group, which is incorporated in the second lens group frame 2k. The second lens group is a lens group that moves together with the second lens group frame 2k during zooming (hereinafter also referred to as zooming).

  Reference numeral 3 denotes a third lens group, which is fixed to the main body 9. The third lens group 3 is a lens group that does not move.

  Reference numeral 4 denotes a fourth lens group, which is incorporated in the fourth lens group frame 4k. The fourth lens group is a lens group that moves integrally with the fourth lens group lens frame 4k at the time of zooming, and also moves alone to perform focus adjustment (hereinafter also referred to as focusing).

  Reference numeral 5 denotes a fifth lens group, which is fixed to the main body 9. The fifth lens group 5 is a lens group that does not move.

  Reference numeral 7 denotes an optical filter in which an infrared light cut filter and an optical low-pass filter are stacked, and is assembled to the main cylinder 9. Reference numeral 8 denotes an image sensor, and a CCD (Charge Coupled Device) type image sensor, a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor, or the like is used. The image sensor 8 is assembled to the main body 9. The FPC is a flexible printed circuit board that is connected to the image sensor 8 and connected to other circuits in the camera. S is an aperture shutter unit, which is fixed to the main cylinder 9. Reference numeral 10 denotes a lid member assembled to the main body 9.

  FIG. 3 is a plan view showing a schematic structure inside the main barrel 9 of the lens barrel 50 provided with the lens driving device according to the present embodiment. The figure schematically shows the lens barrel 50 shown in FIG. 2 with the lid member 10 removed and the lens driving device according to the present embodiment arranged outside the lens barrel for the sake of simplicity. It is.

  As shown in the figure, the lens barrel 50 has a sleeve 2s formed integrally with the second lens group frame 2k and a sleeve 4s formed integrally with the fourth lens group frame 4k. A guide shaft 15 is provided. Further, the guide shaft 16 passes through the rotation locking portion 2m formed integrally with the second lens group lens frame 2k and the rotation locking portion 4m formed integrally with the fourth lens group lens frame 4k. Is provided. Thereby, the second lens group lens frame 2k and the fourth lens group lens frame 4k are slidable along the guide shafts 15 and 16 in the direction of the optical axis OB. Each sleeve is fitted with a guide shaft, and the guide shafts 15 and 16 are disposed substantially in parallel with the optical axis OB, and are fixed to the main body 9 by bonding or the like at both ends thereof.

  An engaging portion 2t is integrally formed with the sleeve 2s. A female screw member 23 screwed with the lead screw and moved in the optical axis OB direction along the guide shaft 15 by the rotation of the lead screw has a predetermined play amount in the optical axis OB direction as shown in the figure. And is configured to engage.

  A female screw member 24 that engages with the lead screw and is moved along the guide shaft 15 in the direction of the optical axis OB by the rotation of the lead screw is engaged with the sleeve 4s.

In the stepping motor 20 (hereinafter also referred to as a motor), a lead screw 20r, which is a male screw member, is disposed on an extension line of the rotating shaft. In the lead screw 20r, a first screw groove 20r ₁ and a second screw groove 20r ₂ having different pitches and screw advance directions are formed on one shaft. The lead screw 20r having the first and second screw grooves 20r ₁ and 20r ₂ may be individually manufactured and joined to be integrated, or may be processed from an integrated shaft.

The female screw member 23 is engaged with the first screw groove 20r ₁ of the lead screw 20r, and moves the second lens group frame 2k engaged with a predetermined play amount in the optical axis OB direction. Similarly, female screw member 24, the second screw groove 20r ₂ and screwed of the lead screw 20r, moving the fourth lens group holding frame 4k which engages the optical axis OB direction.

  As a result, the second lens group 2 and the fourth lens group 4 approach the third lens group 3 from both sides with different movement amounts due to the rotation of the first motor 20 in a predetermined direction, and the reverse direction of the first motor 20. , Both of them move away from the third lens group 3 with different movement amounts.

In this way, by providing play between the female screw member 23 and the engaging portion 2t formed on the second lens group frame 2k that holds the second lens group 2, the female screw member 23 The play amount, which is the difference between the thickness t _{1 in the} direction of the optical axis OB and the opening amount t ₂ of the engaging portion 2 t can be freely set, and the fourth lens group 4 moves in a state where the second lens group 2 is stopped. A sufficient amount can be secured. Further, sufficient resolution is the amount increment of the stop position at the time of focusing by moving the fourth lens group frame 4k with the movement of the female screw member 24 by the second rotation of the screw groove 20r ₂ of the lead screw 20r It is possible to set in detail.

  32 is a photo interrupter. The photo interrupter 32 detects the initial position for positioning the second lens group frame 2k by detecting the switching position of the presence or absence of the shielding portion formed on the second lens group frame 2k.

  The position control of each lens group is performed by controlling the rotation direction and the rotation amount of the first motor 20 with reference to the initial position. The initial position detection of the lens group lens frame may be a photo reflector.

  That is, in the prior art, an initial position detection means is required for each lens group lens frame. However, in this embodiment, only one initial position detection of the lens group lens frame is required, which saves space and costs. Is possible. This detection means may be any means that detects the position of either the second lens group lens frame 2k or the fourth lens group lens frame 4k, but has a predetermined play amount with respect to the rotation of the lead screw. It is desirable to detect the position of the moving second lens group lens barrel 2k. Thereby, it is possible to know the focal length during zooming more accurately.

  FIG. 4 is an internal cross-sectional view of the sleeve 2s cut along a plane perpendicular to the optical axis OB. This figure shows only the sleeve 2s side of the second lens group frame 2k.

  As shown in the figure, a guide shaft 15 which is a member fixed to the main body 9 passes through a hole 2h formed in the sleeve 2s, and a friction member 21 biased by a compression coil spring 22 is guided by the guide shaft 15. The shaft 15 is pressed.

  Thereby, as shown in FIG. 2, even if the engaging portion 2t and the female screw member 23 formed in the sleeve 2s have a play amount, and the engaging portion 2t and the female screw member 23 are separated, The second lens group lens frame 2k can be maintained in a stopped state by this frictional force. The female screw member 23 comes into contact with the engaging portion 2t, and the second lens group lens frame 2k is moved in the optical axis OB direction by giving the engaging portion 2t a force that overcomes this frictional force.

  The lens driving device configured to move the second lens group and the fourth lens group of the lens barrel 50 configured as described above will be described in more detail.

  FIG. 5 is a diagram showing drive control when the second lens group and the fourth lens group of the lens barrel 50 according to the present embodiment are moved from the wide-angle side to the telephoto side. 4A is a movement diagram of the second lens group and the fourth lens group, and FIGS. 4B to 4E are engaging portions 2t of the sleeve 2s and the female screw member 23, and the sleeve 4s and the female lens. It is a figure which shows the position of the screw member.

  As shown in FIG. 5A, the second lens group 2 and the fourth lens group 4 are moved so as to approach the third lens group 3 so that the magnification is changed from wide angle (W) to telephoto (T). To do.

  The width from the broken line A to the solid line 2 indicating the position of the second lens group 2 shown in FIG. 5A corresponds to the play amount. When the female screw member 23 moves by this play amount, the female screw member 24 is moved. The fourth lens group 4 is set to move from the broken line C to the position of the broken line B. Hereinafter, a description will be given with reference to FIGS.

  With the state shown in FIG. 3 as the initial state at the wide-angle end, first, the motor is driven so that the female screw member 23 is moved from the Aw position to the 2w position. As a result, the female screw member 23 moves by an amount corresponding to the play amount and comes into contact with the other engaging portion 2t. The second lens group frame 2k remains stopped. At this time, the female screw member 24 and the fourth lens group lens frame 4k move from the Cw position to the Bw position. The state at this position is shown in FIG.

  Further, the motor is driven in the same direction, and the female screw member 23 is moved to a position of 2 ma and stopped. As a result, the second lens group frame 2k approaches the third lens group 3 and is in a position necessary for the focal length MA. At this time, the female screw member 24 and the fourth lens group frame 4k move from the position Bw to the position Bma. The state at this position is shown in FIG.

  Next, the motor is driven in the reverse direction to move the female screw member 24 and the fourth lens group lens frame 4k from the Bma position to the 4ma position. At this time, the female screw member 23 moves in the direction from Ama to Ama, but the female screw member 23 and the engaging portion 2t move within the play amount as shown in FIG. Thus, the second lens group frame 2k remains stopped. This state is a state in which the second lens group 2 and the fourth lens group 4 have the focal length MA and the focus is adjusted with respect to the subject distance at infinity.

  Thereafter, the motor is driven to move the female screw member 24 between 4ma and Bma, so that the fourth lens group lens frame 4k is stopped while the second lens group lens frame 2k is stopped. Focusing can be performed by moving in the state as shown in FIG. That is, the hatching area between the solid line and the broken line B of the fourth lens group 4 in FIG.

  That is, the predetermined play amount is set so that the female screw member 23 does not move the second lens group frame 2k even if the female screw member 24 moves in the focusing drive region.

  As described above, zooming from the wide-angle side to the telephoto side can be performed by the movement of FIGS. 7B to 6D, and focusing can be performed by the movement of FIGS.

  FIG. 6 is a diagram showing drive control when the second lens group and the fourth lens group of the lens barrel 50 according to the present embodiment are moved from the telephoto side to the wide angle side. 4A is a movement diagram of the second lens group and the fourth lens group, and FIGS. 4B to 4E are engaging portions 2t of the sleeve 2s and the female screw member 23, and the sleeve 4s and the female lens. It is a figure which shows the position of the screw member.

  The state will be described from the state in which the female screw member 23 is at the position 2ma and the state in which the female screw member 24 is at the position Bma (the state shown in FIG. 5B).

  First, the motor is driven so that the female screw member 23 is moved from the 2ma position to the Ama position and the female screw member 24 is moved from the Bma position to the Cma position. The state at this position is shown in FIG.

  Further, the motor is driven in the same direction, and the female screw member 23 is moved to the Amb position and stopped. As a result, the second lens group frame 2k moves in a direction away from the third lens group 3, and becomes a position necessary to obtain the focal length MB. At this time, the female screw member 24 and the fourth lens group frame 4k move from the position of Cma to the position of Cmb. The state at this position is shown in FIG.

  Next, the motor is driven in the reverse direction to move the female screw member 24 and the fourth lens group frame 4k from the Cmb position to the 4mb position. At this time, the female screw member 23 moves in the direction of 2 mb from the position of Amb. However, as shown in FIG. 5E, the female screw member 23 and the engaging portion 2t are moved within the play amount, so that they are separated from each other. Thus, the second lens group frame 2k remains stopped. This state is a state in which the second lens group 2 and the fourth lens group 4 have the focal length MA and the focus is adjusted with respect to the subject distance at infinity.

  Thereafter, by driving the motor so as to move the female screw member 24 between 4 mb and Bmb, focusing is performed by moving only the fourth lens group frame 4k while stopping the second lens group frame 2k. It can be carried out.

  As described above, zooming from the wide-angle side to the telephoto side is performed by the movement of FIGS. 7B to 7D, and the focus adjustment to the infinite object is performed by the movement of FIGS. From FIG. 5E, focusing can be performed by moving only the fourth lens group 4k.

  As described above, the two lens groups having a single motor for moving the two lens groups in the optical axis direction and the lead screw rotated in conjunction with the rotation of the motor are moved. Of these, one lens group moves with the rotation of the lead screw, and the other lens group is configured to move with a predetermined play amount with respect to the rotation of the lead screw, thereby requiring a complicated cam. Therefore, a lens barrel having a low-cost lens driving device that can be changed to an arbitrary focal length continuously and can be focused and that can perform focusing and that is thin in the radial direction and low in cost is obtained. Is possible.

  In addition, a sufficient amount of focusing movement and stepping accuracy (resolution) are ensured by providing a predetermined play amount between the female screw member screwed into the lead screw and the lens frame holding the moving lens group. It becomes possible to do.

  In the above description, the bending optical system has been described as an example. However, the present invention is not limited to this, and the present invention can be applied to an optical system that includes the bending optical system and does not change its overall length. In the case of a bending optical system, there is a strong demand for thinning the lens barrel when incorporated in a camera or the like. On the other hand, the lens barrel of the present embodiment is particularly suitable.

  In addition, although the example in which the second lens group lens frame is stationary by the frictional force has been described, a configuration in which the second lens group lens frame is stationary by using continuous clicks or the like may be used. In addition, the configuration of the integrally formed lead screw has been described, but the configuration may be such that the two lead screws rotate in conjunction with the rotation of the motor.

  In the above-described embodiment, the camera is described as an example of the imaging device. However, the present invention can also be applied to a lens barrel of a camera module built in a portable terminal such as a PDA or a cellular phone.

It is a figure which shows an example of the internal arrangement | positioning of the main structural unit of the camera which is an example of the imaging device provided with the lens barrel which concerns on this Embodiment. 1 is a cross-sectional view illustrating a foldable imaging optical system that is variable in magnification and is contained in a lens barrel according to the present embodiment. It is a top view which shows schematic structure inside the main barrel of the lens barrel provided with the lens drive device concerning this Embodiment. FIG. 5 is an internal cross-sectional view of a sleeve 2s cut along a plane perpendicular to the optical axis OB. It is a figure which shows the drive control at the time of moving the 2nd lens group and 4th lens group of the lens barrel which concerns on this Embodiment from a wide angle side to a telephoto side. It is a figure which shows drive control at the time of moving the 2nd lens group and 4th lens group of the lens barrel which concerns on this Embodiment from the telephoto side to the wide angle side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st lens group 2 2nd lens group 2k 2nd lens group frame 3 3rd lens group 4 4th lens group 4k 4th lens group frame 5 5th lens group 7 Optical filter 8 Imaging element 9 Main trunk 15, 16 Guide shaft 20 Stepping motor 20r Lead screw 23, 24 Female screw member 50 Lens barrel 100 Camera

Claims (7)

A plurality of lens groups for guiding subject light, a single motor for moving two lens groups of the plurality of lens groups in the optical axis direction, and rotated in conjunction with the rotation of the motor. A lead screw,
Among the two lens groups to be moved, one lens group moves with the rotation of the lead screw, and the other lens group moves with a predetermined play amount with respect to the rotation of the lead screw. A lens barrel comprising the apparatus. A female screw member threadably engaged with the lead screw, and a predetermined play between the female screw member and a lens frame that holds a lens group that moves with a predetermined play amount with respect to the rotation of the lead screw; The lens barrel according to claim 1, wherein an amount is provided. The lens frame that holds the lens group that moves with a predetermined play amount with respect to the rotation of the lead screw is provided with a mechanism that applies a frictional force to a fixed member. The lens barrel according to 1 or 2. A single detection unit that detects a position of the lens group that is moved by the lens driving device; and the detection unit determines a position of the lens group that moves with a predetermined play amount with respect to the rotation of the lead screw. The lens barrel according to claim 1, wherein the lens barrel is detected. The lens group that moves with the rotation of the lead screw performs zooming and focusing by movement, and the lens group that moves with a predetermined play amount with respect to the rotation of the lead screw performs zooming by movement. The lens barrel according to any one of claims 1 to 4, characterized in that: The lens barrel according to any one of claims 1 to 5, wherein an optical system composed of the plurality of lens groups has a total length that does not change. An imaging apparatus comprising the lens barrel according to claim 1.