JP2009139516A - Lens driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens driving device which suppresses backlash of an engagement gap between a cylindrical turning part of a rack and a nearly cylindrical bearing shape of a lens holding frame, then, achieves higher accuracy in automatic focusing. <P>SOLUTION: The lens driving device is configured such that the lens holding frame 3 supporting the cylindrical turning part of the rack 5 includes two surfaces that form an angle with each other, and the cylindrical turning part of the rack 5 is biased and held by the two surfaces, thus, with the simple structure, the rack 5 is supported by the lens holding frame 3 without causing backlash. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a lens driving device for a zoom lens / focus lens mounted on a camera, a video camera, or the like.

  As every year, video cameras are becoming smaller and lighter, with higher magnification and higher performance. In the above-described video camera, an autofocus method using a video signal is used as a method for adjusting the focus. This autofocus method uses the peak position of the high frequency component signal (focus voltage) in the video signal from the image sensor as the in-focus position. For example, the position of the focus lens is highly accurate so that the focus voltage is maximized. Is controlling.

  In addition, high-precision movement control is also required for zoom lenses due to miniaturization and high magnification.

As a device that transmits drive to move such a lens,
There is one described in Japanese Patent Laid-Open No. 05-272149. In this apparatus, a motor having a lead screw parallel to the optical axis direction is disposed in the vicinity of a lens frame that is a driven member, and a rack provided on a lens holding frame that is a driven member is disposed on the lead screw. The rack gear meshes and one end of the rack has a trapezoidal shape, the other end has a shaft that is substantially cylindrical in the optical axis direction, one end of the lens holding frame has a cylindrical hole shape, and the other end has a substantially cylindrical bearing shape. The trapezoidal portion of the rack is urged against the cylindrical hole portion of the lens holding frame, and the cylindrical rotating portion of the rack is fitted into the substantially cylindrical bearing shape of the lens holding frame, so that the rack A spring material is provided that is rotatably held in a direction perpendicular to the optical axis direction and applies a predetermined pressure to the lead screw. The lens holding frame is moved by driving the motor with predetermined control.
JP 05-272149 A

  However, in the above-described conventional example, the cylindrical rotating portion of the rack is configured to be rotatable to the substantially cylindrical bearing shape of the lens holding frame, so that even if the fitting gap is configured to be extremely small, there is some structure. There was a backlash.

This rattling caused an error in the operation of moving the focus lens back and forth with an amplitude of several microns in the direction of the optical axis, which hindered high accuracy of autofocus.
The present invention solves this problem, and an object of the present invention is to provide a lens driving device capable of suppressing the looseness of the fitting gap and increasing the accuracy of autofocus.

  In order to solve the conventional problem, a lens driving device according to claim 1 of the present invention includes a lens holding frame that holds a lens, a guide shaft that guides the lens holding frame in the optical axis direction, and the lens holding frame. A lead screw that is rotated by a drive source to drive in the optical axis direction, a rack gear portion that meshes with the lead screw, and a substantially cylindrical rotation support portion that can bias the rack gear portion toward the lead screw. And a lens driving device including a rack that drives the lens holding frame in the optical axis direction according to rotation of the lead screw. The lens holding frame has a substantially cylindrical shape that supports a substantially cylindrical rotating portion of the rack. The rack bearing portion has two surfaces having angles with each other in a part of the rack bearing portion, and the cylindrical rotating portion is urged and held by the two surfaces. To configure.

  The lens driving device according to claim 2 of the present invention is the lens driving device according to claim 1, wherein the support shaft of the rack is provided with two mutually angled surfaces provided on a part of the rack bearing portion of the lens holding frame. And a large-diameter cylindrical portion that contacts the cylindrical rack bearing portion of the lens holding frame, and the radius of the small-diameter cylindrical portion is smaller than the radius of the large-diameter cylindrical portion. Configure as follows.

Furthermore, a lens driving device according to a third aspect of the present invention is the lens driving device according to the second aspect, wherein the radial center of the small-diameter cylindrical portion and the radial center of the large-diameter cylindrical portion are coaxial.
Furthermore, in the lens driving device according to claim 4 of the present invention, in the configuration according to claim 1, the rack is urged against the lead screw by a spring, and a shaft portion having a substantially cylindrical shape of the rack by a reaction of the urging force. Is configured to be biased and held by the two mutually angled surfaces.
Further, the lens driving device according to claim 5 of the present invention has a shaft portion in which one end of the rack is substantially conical or spherical and the other end is substantially cylindrical in the optical axis direction. One end of the lens holding frame has a circular hole shape, and the other end has a substantially cylindrical bearing shape. The substantially cylindrical bearing shape portion of the lens holding frame has two mutually angled surfaces, and the rack The substantially conical shape or the substantially spherical portion of the lens abuts against the circular hole portion of the lens holding frame and is biased and held by the compression restoring force of the coil spring, and the cylindrical rotating portion of the rack is substantially the same as the lens holding frame. The rack is fitted into a cylindrical bearing shape, and the rack is held so as to be rotatable in a direction perpendicular to the optical axis direction. The rack is urged by the torsion coil action of the spring, and the reaction of the urging force causes the rack to react. Substantially cylindrical shape Is the shaft portion which is urged to the surface having the two angles to each other adapted to hold.

  According to the lens driving device of the present invention, the rack can be supported on the lens holding frame without backlash with the simple structure shown in claim 1, and a highly accurate lens moving operation can be performed with a simple and inexpensive configuration.

  Furthermore, as shown in claim 2, the radius of the cylindrical shaft portion of the rack biased by two mutually angled surfaces provided in the lens holding frame portion is substantially the same as that of the other lens holding frame. By making it smaller than the sliding radius of the cylindrical bearing portion and the cylindrical shaft portion of the rack, the angle formed by two mutually angled surfaces provided in the lens holding frame portion can be reduced. The effect of receiving becomes more remarkable.

Furthermore, as shown in claim 3, the center of rotation of the cylindrical shaft portion of the rack urged by two mutually angled surfaces provided in the lens holding frame portion, and the other lens holding frame By arranging the rotation center of the sliding portion of the substantially cylindrical bearing portion of the rack and the cylindrical shaft portion of the rack on the same axis, the lead screw and the guide pole are not aligned in parallel due to variations in accuracy of components, and the holding frame Even when the rack is rotated on the basis of the rotation center of the holding frame by the movement, the clearance between the portions supported by the cylinders does not change, and a stable operation can be obtained.
Furthermore, as shown in claim 4, the rack is urged against the lead screw by a spring, and a substantially cylindrical shaft portion of the rack is counteracted by the urging force so that the two surfaces having an angle with each other. The lens driving device according to claim 1, wherein the rack is supported by the lens holding frame without play.
Furthermore, as shown in claim 5, one end of the rack has a substantially conical or spherical shape, and the other end has a shaft portion that is substantially cylindrical in the optical axis direction, and one end of the lens holding frame has a circular hole shape. The other end has a substantially cylindrical bearing shape, the substantially cylindrical bearing shape portion of the lens holding frame has two mutually angled surfaces, and the substantially conical shape or the substantially spherical portion of the rack is Abutting against the circular hole of the lens holding frame and being urged and held by the compression restoring force of the coil spring, the cylindrical rotating part of the rack is fitted into the substantially cylindrical bearing shape of the lens holding frame, The rack is held so as to be rotatable in a direction perpendicular to the optical axis direction, and is urged against the lead screw by the torsion coil action of the spring, and the substantially cylindrical shaft portion of the rack is caused by the reaction of the urging force. Have two angles with each other And a lens driving device according to claim 1 which is configured to be biased to hold the surface, it is possible to play without supporting the rack in the lens holding frame.

  Embodiments of a lens driving device of the present invention will be described in detail below with reference to the drawings.

(Embodiment)
FIG. A, FIG. B, FIG. 2, FIG. 3 and FIG. 4 are drawings that best illustrate the features of the present invention. A, FIG. B is a cross-sectional view, FIG. 2 is a front view, and FIGS. 3 and 4 are detailed views of bearing portions. FIG. 5 is a detailed view of a conventional bearing portion.

  FIG. A, FIG. B, in FIG. 2, 1 and 2 are guide poles arranged parallel to the optical axis, 3 is a lens holding frame supported by the guide poles 1 and 2 so as to be movable in the optical axis direction, and 4 is a lens holding frame. The lens held by 3, 5 is a rack attached to the lens holding frame 3, 6 is a lead screw meshing with the rack gear portions 5 c and 5 d for driving the lens holding frame 3 in the optical axis direction, and 7 is a lead screw. A motor 8 serving as a power source for rotationally driving the motor 8 functions as a compression spring to eliminate backlash between the rack 5 and the lens holding frame 3, and the backlash between the rack gear portions 5 c and 5 d and the lead screw 6 is engaged. It is a loose coil spring that functions as a torsion coil spring to eliminate it.

  The lens holding frame 3 engages the guide pole 1 with a square hole portion 3a provided on a support arm projecting on the guide pole 1 side, and a cylindrical hole 3b provided on a support arm projecting on the other side. The guide pole 2 is passed through 3c and supported so as to be movable in the optical axis direction.

  The rack 5 has a conical or spherical surface portion 5a projecting from one end portion of the side surface, and a support shaft 5b projecting from the other side surface of the conical or spherical surface portion 5a.

  The lens holding frame 3 is provided with support arms 3d and 3e formed in parallel in the vicinity of the cylindrical holes 3b and 3c provided in the support shaft, and the cone of the rack 5 is provided in the hole 3i provided in one support arm 3d. The rack 5 is assembled to the lens holding frame 3 by engaging the portion 5a and engaging the support shaft 5b with the cylindrical portion 3j of the other support arm 3e. At this time, in order to facilitate assembly, a slit is provided in the cylindrical portion 3j, and on the other hand, the support shaft 5b supported here is formed in an oval shape so that it can pass through the slit, and the rack 5 is inserted and then rotated to the use position. By doing so, a cylindrical bearing is constituted and held.

  A coil spring 8 fitted to the support shaft 5b at the time of assembly is interposed between the rack 5 and the support arm 3e in a compressed state.

  Then, the lead screw 6 is interposed between the rack gear portions 5c and 5d, and the one end 8a of the coil spring 8 is locked at the 5e position of the rack 5, and the other end 8b of the coil spring 8 is locked at the 3f position of the lens holding frame 3. The lead screw 6 is locked so as to be pressed.

  In the above assembled state, the extension restoring force of the coil spring 8 acts on the rack 5 in the pressing direction of the conical portion 5a against the hole 3i of the support arm 3d, and the torsion restoring force causes the lead screw 7 to act on the rack gear portion 5c. Press.

  As shown in FIG. 3, the support shaft 3e has a surface 3g for supporting the cylindrical surface of the support shaft 5b at a position symmetric with respect to the line in the substantially intermediate direction 10 of the angle formed by both ends 8a and 8b of the spring 8. 3h is provided.

  With this configuration, the support shaft 5b is biased in the direction of approximately T by the spring 8, and is biased to the 3g and 3h surfaces provided on the support frame 3e. This state is exactly the same as when the cylindrical member is installed on the V block, and is positioned so as to be rotatable around the central axis of the cylinder without play.

  Accordingly, the rack 5 can be rotated with respect to the lens holding frame 3 even if the rack 5 is attached to the lens holding frame 3 without looseness and the relative position between the lead screw 6 and the rack 5 varies. And the lead screw 6 can be kept in a good meshing state.

  By adopting such a configuration, a lens holding frame that holds the focus lens through the rack 5 by operating the motor 7 to move the focus lens back and forth with an amplitude of several microns in the optical axis direction in order to perform an autofocus operation. 3 is operated in the back-and-forth motion, in the conventional configuration, the rack 5 and the lens holding frame 3 are affected by the clearance between the support shaft 5b provided in the rack 5 and the cylindrical portion 3j provided in the lens holding frame 3. The movement of the lens holding frame 3 in the direction of the optical axis is reduced, and an error occurs in the information obtained by the focusing operation, making it impossible to obtain a precise autofocusing operation. According to this, it becomes possible to reduce the influence of the clearance, and it is possible to perform an autofocus operation with higher accuracy than before.

  In particular, in recent years, it has been required to reduce the amount of forward and backward movement of the focus lens during autofocus by increasing the zoom magnification and downsizing the lens itself. Patents are extremely effective.

  In addition, the auto focus lens is controlled in conjunction with the position of the zoom lens, and the movement accuracy of the zoom lens is also necessary for the high accuracy of the auto focus, and constitutes a zoom lens with a high magnification and a small size. Therefore, the configuration of this patent is also extremely effective in the driving mechanism of the zoom lens moving frame.

  Note that the direction of T is not necessarily in the middle of the angle formed by both ends 8a and 8b of the spring 8 due to the shape and characteristics of the spring, so the support surface 3g is optimally positioned in accordance with the actual spring load configuration. 3h may be provided. In addition, due to structural limitations, even if the positions for biasing the support surfaces 3g and 3h are shifted from each other, the same effect can be obtained if there is a biasing force on both surfaces.

  FIG. 4 shows a detailed view of the bearing portion described in the second and third aspects of the invention. The support shaft 5b of the rack 5 is provided with a small cylindrical portion 5b-a having a cylindrical radius Ra which is in contact with the support surfaces 3g and 3h provided on the cylindrical portion 3j of the lens holding frame 3, and the cylindrical portion of the lens holding frame 3. 3j has a large cylindrical portion 5b-b having a cylindrical radius Rb corresponding to 3j, the radius Ra is smaller than the radius Rb, and the centers of the respective radii are arranged concentrically. . A, FIG. B, exactly the same as the embodiment shown in FIG.

  As described above, by reducing the cylindrical radius of the rack 5 at the portion where the support surfaces 3f and 3g meet, the angle S formed by the support surfaces 3f and 3g can be reduced, and the effect of the V-reception is more remarkable. At the same time, it is advantageous for variations in the biasing angle of the rack 5 to the support surfaces 3g and 3h of the rack 5 by the rack spring 8.

  Furthermore, by arranging the center of the cylindrical radius corresponding to the support surfaces 3g and 3h and the radius center of the portion supported by the cylinders on the same axis, the lead screw and the guide pole are not parallel due to variations in accuracy of the components, Even when the rack is rotated with reference to the rotation center of the holding frame due to the movement of the holding frame, the clearance of the portions supported by the cylinders does not change, and a stable operation can be obtained.

  The lens driving device according to the present invention relates to a zoom lens and focus lens driving device of a zoom lens device mounted on a video camera or the like. The zoom lens device according to the present invention has a small, light, low-cost, high-precision lens driving mechanism, and is useful as a zoom lens device for digital still cameras, digital video cameras, and the like.

Sectional drawing of the lens drive device which shows one Example of this invention FIG. Enlarged view explaining the rack part of A The front view of the lens drive device which shows one Example of this invention 1 is a detailed view of a rack holding portion of a lens driving device showing one embodiment of the present invention. 3 is a detailed view of the rack holding portion of the lens driving device showing the embodiments of the first, second, and third aspects of the present invention. Detailed view of the rack holding portion of the lens driving device in the conventional embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Guide pole 2 Guide pole 3 Lens holding frame 4 Lens 5 Rack 6 Lead screw 7 Motor 8 Coil spring A FIG. Part Ra, Rb Radius of support shaft 5b provided on rack 5 S Relative angle of planes 3g and 3h T Arrow indicating direction 3a Square hole provided in lens holding frame 3b Cylindrical hole provided in lens holding frame 3c Cylindrical hole provided in the lens holding frame 3d Support arm provided in the lens holding frame 3e Support arm provided in the lens holding frame 3f Coil spring 8 provided in the lens holding frame 3g 5 support shafts provided in the lens holding frame Receiving plane 3h receiving plane 5 provided on the lens holding frame 3i 3d hole provided in 3d 3j cylindrical portion provided in 3d 5a cone or spherical protrusion 5b provided in rack 5b supporting shaft provided in rack 5b- a 5b Small diameter cylindrical portion provided on the support shaft
5b-b 5b Large-diameter cylindrical portion provided on the support shaft 5c Rack gear portion provided on the rack 5d Rack gear portion provided on the rack

Claims (5)

  A lens holding frame that holds the lens, a guide shaft that guides the lens holding frame in the optical axis direction, a lead screw that is rotated by a drive source to drive the lens holding frame in the optical axis direction, and the lead screw A rack gear portion that meshes with the lead screw and a substantially cylindrical rotation support portion that can urge the rack gear portion toward the lead screw, and that drives the lens holding frame in the optical axis direction according to the rotation of the lead screw. In the lens driving apparatus, the lens holding frame has a substantially cylindrical rack bearing portion that supports the substantially cylindrical rotating portion of the rack, and two portions of the rack bearing portion have an angle with each other. A lens driving device configured to hold and hold the cylindrical rotating portion against the two surfaces.   A small-diameter cylindrical portion that contacts two mutually angled surfaces provided on a part of the rack bearing portion of the lens holding frame on the rack support shaft, and a cylindrical rack bearing portion of the lens holding frame 2. The lens driving device according to claim 1, further comprising a large-diameter cylindrical portion corresponding to the first diameter, wherein a radius of the small-diameter cylindrical portion is smaller than a radius of the large-diameter cylindrical portion.   The lens driving device according to claim 2, wherein the radius center of the small-diameter cylindrical portion and the radius center of the large-diameter cylindrical portion are configured to be coaxial.   The rack is urged to the lead screw by a spring, and a substantially cylindrical shaft portion of the rack is urged and held by the two mutually angled surfaces by a reaction of the urging force. Item 4. The lens driving device according to Item 1.   One end of the rack has a substantially conical shape or a spherical shape, and the other end has a shaft portion that is substantially cylindrical in the optical axis direction. One end of the lens holding frame has a circular hole shape, and the other end has a substantially cylindrical bearing shape. The substantially cylindrical bearing-shaped portion of the lens holding frame has two mutually angled surfaces, and the substantially conical shape or the substantially spherical portion of the rack abuts on the circular hole portion of the lens holding frame. While being biased and held by the compression restoring force of the coil spring, the cylindrical rotating portion of the rack is fitted into the substantially cylindrical bearing shape of the lens holding frame, and the rack rotates in a direction perpendicular to the optical axis direction. The rack is held movably and urged against the lead screw by the torsional coil action of the spring, and by the reaction of the urging force, the substantially cylindrical shaft portion of the rack is attached to the two mutually angled surfaces. To be held and held The lens driving device according to claim 1 in which form.

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