JP4060046B2 - Lens drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lens driving device used as an objective lens focus adjustment mechanism.
[0002]
[Prior art]
In an observation apparatus such as an endoscope and a microscope, and a photographing apparatus such as an electronic still camera and a video camera, it is desired to reduce the size of an objective lens mechanism that is integrally incorporated. Specifically, in an endoscope, an objective lens is incorporated in the distal end surface of a flexible tube inserted into a body organ, and the diameter of the flexible tube is reduced in order to relieve pain of the patient, that is, the objective lens mechanism. Small diameter is a problem. In order to meet these demands, photographing devices such as electronic still cameras are always required to be smaller and lighter in camera body and to be more flexible in the arrangement of components in terms of design. For this purpose, it is necessary to reduce the size of the objective lens mechanism.
[0003]
In an endoscope or the like, the objective lens mechanism is configured by assembling a fixed focus lens having a deep subject depth, thereby reducing the size and simplifying the configuration. However, in the case of the fixed focus type, there is a problem that the focus is reduced when the subject image is enlarged close to the subject, and a focus adjustment function and a zoom function by a small lens driving device are required.
[0004]
[Problems to be solved by the invention]
However, in the case of a conventional lens focus adjustment mechanism, a lens holding frame that holds the outer periphery of the objective lens, and a drive transmission mechanism that moves the lens holding frame forward and backward along the optical axis outside the objective lens, for example, the rotation of the motor is held by the lens. Since a plurality of gears to be transmitted to the frame are necessary, there is a problem that it is difficult to reduce the size, particularly to reduce the diameter.
[0005]
The present invention has been made in view of the above problems, and an object thereof is to reduce the diameter of the objective lens focus adjustment mechanism.
[0006]
[Means for Solving the Problems]
The present invention includes an optical system supported at the tip of a cylindrical outer cylinder and capable of moving back and forth along an optical axis that coincides with the axial center of the cylindrical outer cylinder, and a rotor having a smaller diameter than the inner diameter of the cylindrical outer cylinder. And a wobble motor mechanism that causes the rotor to rotate and rotate inside the cylindrical outer cylinder, and a linkage member that converts the motion of the rotor into a linear motion along the optical axis direction of the optical system.
[0007]
The wobble motor mechanism includes a drive electrode that is equally divided in the circumferential direction on the inner peripheral surface of a cylindrical outer cylinder, and a conductive rotor that is freely inserted inside the drive electrode. It may be an electrostatic wobble motor that rotates the rotor by sequentially moving in the direction. Furthermore, the wobble motor mechanism may be configured to include an annular common electrode that is fixed to the inner peripheral surface of the cylindrical outer cylinder and through which the rotor is inserted, and is always in contact with the rotor.
[0008]
Further, the wobble motor mechanism is freely inserted into a plurality of drive magnetic poles uniformly disposed in the circumferential direction on the inner peripheral surface of the cylindrical outer cylinder, a field coil for generating a magnetic flux, and the drive magnetic poles. It may be an electromagnetic wobble motor that includes a magnetic rotor and rotates the rotor by sequentially switching drive magnetic poles to generate magnetic flux in the circumferential direction.
[0009]
It is preferable that the linkage member of the lens driving device cancels the eccentricity of the rotor, converts only the rotation of the rotor into motion in the optical axis direction, and transmits the motion to the optical system. More specifically, for example, the first linkage member in which the linkage member loosely fits along the first axis perpendicular to the optical axis with respect to the rotor, and the optical axis and the first axis with respect to the first linkage member. A second linkage member that is loosely fitted along a second axis perpendicular to the second axis, and a third linkage member that is loosely fitted relative to the second linkage member in the direction of the optical axis.
[0010]
The first linkage member is formed with a first elongated hole extending along the first axis, and the rotor is provided with a first pin guided by the first elongated hole and relatively moved along the first axis. A second elongated hole extending along the second axis is formed in the linkage member, a second pin guided by the second elongated hole and relatively moved along the second axis is provided on the first linkage member, and Further, it is preferable that a third elongated hole extending in the optical axis direction is formed in the second linkage member, and a third pin guided by the third elongated hole and relatively moved in the optical axis direction is provided in the third linkage member. . The third linkage member may hold the optical system integrally and be helicoidally supported by a cylindrical outer cylinder. Further, these linking members may be positioned in the optical axis direction by a cylindrical outer cylinder.
[0011]
The lens driving device may be provided at the distal end of the endoscope. At this time, the rotor and the linking member are respectively formed with circular holes for allowing light to enter the image guide fiber.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0013]
FIG. 1 is a view showing an endoscope to which the lens driving device of the present embodiment is applied, and is an enlarged perspective view showing a distal end portion of the endoscope. On the distal end surface 10a of the endoscope 10, two illumination windows 12 for supplying illumination light to a subject such as an inner wall surface of a living organ and reflected light from the subject provided between the illumination windows 12 are incident. An observation window 14 is provided. Furthermore, an air / water supply port 16 and a forceps hole 18 for inserting the treatment tool are provided on the endoscope distal end surface 10a.
[0014]
Inside the endoscope 10, there are a light guide fiber (not shown) for guiding illumination light from a light source (not shown) to the illumination window 12, and an image guide fiber 20 for guiding reflected light to an eyepiece (not shown). An objective lens system including a movable lens 22 for focus adjustment is provided between the distal end surface 20a of the image guide fiber and the observation window 14.
[0015]
2 and 3 are views showing a first embodiment of the lens driving device according to the present invention. FIG. 2 is an end view when the lens driving device is cut in a cross section parallel to the optical axis. The upper half shows the retracted state of the movable lens 22 and the lower half shows the advanced state of the movable lens 22. FIG. 3 is an exploded perspective view showing the configuration of the lens driving device other than the outer cylinder.
[0016]
The movable lens 22 is fitted into a cylindrical lens holding frame 30, and this lens holding frame 30 is helicoidally supported at the tip opening of the cylindrical outer cylinder 24, and has an optical axis L 1 that coincides with the axis of the outer cylinder 24. You can move forward and backward. That is, the lens driving device includes a helicoid screw mechanism 34 including a male screw portion 32 formed on the outer peripheral surface of the lens holding frame 30 and a female screw portion 26 formed on the inner peripheral surface of the outer cylinder front end portion 25, and the lens holding device. When the frame 30 rotates relative to the optical axis L1, this rotational movement is converted into a straight movement along the optical axis L1 by the helicoid screw mechanism 34, and the lens holding frame 30, that is, the movable lens 22 moves forward and backward along the optical axis L1. The distance from the image guide fiber tip surface 20a is changed.
[0017]
An image fiber support tube 28 made of a flexible synthetic resin material is provided between the image guide fiber 20 and the outer tube 24. The image fiber support tube 28 physically protects the image guide fiber 20, and its distal end surface 28a is an annular surface perpendicular to the optical axis L1, and is rearward from the distal end surface 20a of the image guide fiber (rightward in FIG. 2). ). The outer cylinder front end portion 25 that supports the lens holding frame 30 is formed with a smaller diameter than the main body portion of the outer cylinder 24, and a wobble motor mechanism is provided between the front end surface 28 a of the image fiber support cylinder 28 and the outer cylinder front end portion 25. 40. A first linkage member 50 and a second linkage member 60 that transmit the rotational driving force of the wobble motor mechanism 40 to the lens holding frame 30 are provided. The rotational driving force of the wobble motor mechanism 40 is sequentially transmitted to the first linkage member 50, the second linkage member 60, and the lens holding frame 30 as the third linkage member, whereby the movable lens 22 advances and retreats while rotating, the objective lens. The focus position of the system is adjusted.
[0018]
The wobble motor mechanism 40 is an electrostatic wobble motor including a cylindrical stator composed of a drive electrode 44 and a common electrode 46 fixed to the inner peripheral surface of the outer cylinder 24, and a rotor 42 that is a conductor. By changing the voltage application position, the electrostatic attraction force that attracts the rotor 42 is changed in the circumferential direction to cause the rotor 42 to roll. The drive electrode 44 is equally divided into six electrode elements 44a, 44b, 44c, 44d, 44e, and 44f in the circumferential direction, and a predetermined gap is provided between adjacent electrode elements to electrically isolate each other. Has been. The common electrode 46 is an annular member installed on the inner peripheral surface of the outer cylinder 24 and is separated from the drive electrode 44 to some extent in the direction of the optical axis L1. Both the inner diameter of the drive electrode 44 and the inner diameter of the common electrode 46 are equal, and the outer diameter of the cylindrical rotor 42 is set to a value smaller than these inner diameters. The axial length of the rotor 42 is longer than the total axial length of the drive electrode 44 and the common electrode 46, and the rotor 42 is movably inserted inside both the drive electrode 44 and the common electrode 46.
[0019]
A portion of the rotor 42 facing the drive electrode 44 is covered with an insulating film 41 so that the rotor 42 and the drive electrode 44 are not electrically connected. The insulating film 41 may be provided on the inner peripheral surface of the drive electrode 44. An insulating film is not provided on a portion of the rotor 42 facing the common electrode 46, and the rotor 42 and the common electrode 46 are always in contact with each other and are conductive. Note that an insulating spacer may be provided between the drive electrode 44 and the common electrode 46 or between the electrode elements 44a to 44f for electrical insulation.
[0020]
When a voltage is applied to any one of the electrode elements 44a to 44f and the common electrode 46, an electrostatic force is generated between the rotor 42 and the electrode element to which the voltage is applied, and a voltage is applied to the rotor 42. Is sucked into the electrode element. Therefore, when the electrode elements to which the voltage is applied are sequentially switched in the circumferential direction, for example, the arrow X direction (44a → 44b → 44c → 44d → 44e → 44f), the rotor 42 rolls in the X direction while being eccentric from the optical axis L1. At the same time, the motor rotates in the Y direction, which is the direction opposite to the rolling direction, around the rotor axis L2.
[0021]
A pair of first pins 45 a and 45 b projecting toward the movable lens 22 is implanted on the lens side end surface 43 of the rotor 42. The pair of first pins 45a and 45b are on a first axis L3 perpendicular to the rotor axis L2, and are point-symmetric with respect to the rotor axis L2. The first pins 45a and 45b are loosely fitted in a pair of first elongated holes 52a and 52b formed in the first linkage member 50, respectively.
[0022]
The first linkage member 50 is a disc member having a circular hole 56 formed in the center, and the outer diameter thereof is larger than the outer diameter of the rotor 42 and smaller than the inner diameter of the outer cylinder 24. The first linkage member 50 is in close contact with the lens side end surface 43 of the rotor 42, and at this time, the first pins 45a and 45b are engaged with the first elongated holes 52a and 52b. The first elongated holes 52a and 52b are in a point-symmetrical position with respect to the center of the first linkage member 50, extend along the radial direction, and the hole width is substantially equal to the diameter of the first pins 45a and 45b.
[0023]
Accordingly, when the rotor 42 rotates while rotating, the first pins 45a and 45b are guided by the first elongated holes 52a and 52b, and the first linkage member 50 rotates integrally with the rotor 42 in the circumferential direction. The first axis L3 coinciding with the longitudinal direction of the first pins 45a and 45b moves relative to each other while being in sliding contact with the lens side end surface 43. Thus, the eccentricity of the rotor 42 in the direction of the first axis L3 is canceled by the first pins 45a and 45b and the first long holes 52a and 52b.
[0024]
A pair of second pins 54 a and 54 b projecting toward the movable lens 22 is implanted on the lens-side end surface 53 of the first linkage member 50, and the pair of second pins 54 a and 54 b is the center of the first linkage member 50. With respect to each other. The straight line connecting the second pins 54a and 54b extends along the first axis L3 and the second axis L4 perpendicular to the optical axis L1, that is, the second pins 54a and 54b are circumferential from the first elongated holes 52a and 52b, respectively. At 90 degrees apart. The second pins 54a and 54b are loosely fitted in a pair of second elongated holes 62a and 62b formed in the second linkage member 60, respectively.
[0025]
The second linkage member 60 is a bottomed cylindrical member having a circular hole 66 formed in the center of the bottom surface, and has an outer diameter substantially equal to the inner diameter of the outer cylinder 24 and is rotatably supported by the outer cylinder 24. The annular bottom surface portion 63 of the second linking member 60 is in close contact with the lens side end surface 53 of the first linking member 50. At this time, the second long holes 62a and 62b formed in the bottom surface portion 63 are provided with second pins 54a and 54b. Engage. The second elongated holes 62a and 62b are in a point-symmetrical position with respect to the axial center of the second linkage member 60, extend along the radial direction, and the hole width is substantially equal to the diameter of the second pins 54a and 54b.
[0026]
When the first linkage member 50 rotates together with the rotor 42, the second pins 54a and 54b are guided by the second elongated holes 62a and 62b, and the second linkage member 60 rotates together with the first linkage member 50 in the circumferential direction. The cylindrical portion 61 of the second linkage member 60 is in contact with the inner peripheral surface of the outer cylinder 24 over the entire circumference, and relative movement along the second axis L4 of the second linkage member 60 is not allowed. However, when the first linkage member 50 is decentered in the direction of the second axis L4 with respect to the optical axis L1, the second pin 54a is in the second elongated hole 62a, and the second pin 54b is in the second elongated hole 62b. This eccentricity is canceled by relative movement along the biaxial line L4.
[0027]
As described above, the rotor 42 rotates while being eccentric with respect to the optical axis L1, but the first pins 45a and 45b and the first elongated holes 52a and 52b, the second pins 54a and 54b, and the second elongated holes 62a and 62b. Since the eccentricity of the rotation center is canceled in each of the first axis L3 direction and the second axis L4 direction orthogonal to each other, that is, the eccentricity with respect to the two-dimensional plane perpendicular to the optical axis L1 is canceled, the lens holding frame 30 has an optical axis. Only the rotation around L1 is transmitted.
[0028]
The rotor 42, the first linkage member 50, and the second linkage member 60 are sandwiched between the distal end surface 28a of the image fiber support tube 28 and the outer tube distal end portion 25, and are positioned in the optical axis L1 direction. 42, a clearance (not shown) is provided so that each of the first linkage member 50 and the second linkage member 60 can smoothly rotate relative to each other.
[0029]
The cylindrical portion 61 of the second linkage member 60 is provided with third elongated holes 64a and 64b extending in parallel with the optical axis L1. The pair of third elongated holes 64a and 64b are in point-symmetric positions with respect to the optical axis L1. On the other hand, third pins 34a and 34b projecting radially outward from the outer peripheral surface of the lens holding frame 30 as the third linking member are implanted. The third pins 34a and 34b are loosely fitted in the third elongated holes 64a and 64b, respectively. The inner diameter of the cylindrical portion 61 is slightly larger than the outer diameter of the lens holding frame 30, and the cylindrical portion 61 and the lens holding frame 30 have a third elongated hole 64 a and a third pin 34 a, and a third elongated hole 64 b and a third pin 34 b. Only engage. The width of the third elongated holes 64a and 64b is substantially equal to the diameter of the third pins 34a and 34b, and the second linkage member 60 and the lens holding frame 30 rotate integrally with respect to the circumferential direction.
[0030]
When the second linking member 60 rotates, the lens holding frame 30 is rotated around the optical axis L1, and at this time, the helicoid screw mechanism 34 (the male screw portion 32 and the female screw portion 26) converts it into a straight movement in the direction of the optical axis L1. Is done. At this time, the third pins 34a and 34b move relative to the optical axis L direction while being guided by the third elongated holes 64a and 64b, respectively, and the lens holding frame 30 moves relative to the optical axis L direction.
[0031]
FIG. 4 is a diagram showing a drive system of the wobble motor mechanism 40. The drive system of the wobble motor mechanism 40 includes a DC controller 102, a switching circuit 104, and a system controller 106 including an oscillator (not shown), which are provided in a processor 100 connected to the endoscope 10. The electrode elements 44a to 44f of the drive electrode 44 are connected to the switching circuit 104 via the drive electrode cable 110, respectively.
[0032]
When the switching circuit 104 sequentially applies the drive voltage provided by the DC power source 102 to the electrode elements 44a to 44f based on the command signal from the system controller 106, the rotor 42 rolls. The command signal given from the system controller 106 includes information on the rolling direction of the rotor 42 (the order in which the driving voltage is applied to the electrode elements) and the rolling amount (the number of times the driving voltage is switched).
[0033]
The common electrode 46 is directly connected to the ground terminal of the DC power supply 102 via the common electrode cable 108. As a result, the rotor 42 is always in pressure contact with any one of the drive electrodes 44, so that slipping or the like is prevented, and torque can be reliably transmitted to the movable lens 22 side.
[0034]
FIG. 5 is a timing chart showing an example of changes in voltage and movable lens position applied to the drive electrodes 44a to 44f of the wobble motor mechanism 40, and FIG. 6 shows a rotor when voltage is applied to the electrode elements in the order shown in FIG. It is a figure which shows the positional change of 42, Comprising: It is the end elevation in the VI-VI sectional view of FIG. 5A to 5G correspond to FIGS. 6A to 6G, respectively. In FIG. 6, the electrode elements to which a voltage is applied are indicated by hatching.
[0035]
A pulsed voltage is applied to each electrode element 44 a-f of the rotor 42. When rotating the rotor 42 in the Y direction, the voltage is increased by a certain time in the order of electrode elements 44a → 44b → 44c → 44d → 44e → 44f → 44a (in the order of FIG. 6 (A) → FIG. 6 (G)). Is applied to roll the rotor 42 in the X direction. Each time the voltage is switched, the rotor 42 rotates by an angle θ (rad) in the Y direction, the movable lens 22 is extended, and a subject at a closer distance comes into focus. If the rotation of the angle θ is defined as one step, the rotor 42 revolves once in six steps and rotates by an angle of 6 · θ. The angle θ is {6 · θ = 2π · (R−r) / r} where r is the outer diameter of the rotor 42 and R is the inner diameter of the drive electrode 44 and the common electrode 46.
[0036]
On the other hand, when rotating the rotor 42 in the X direction, the reverse order of FIG. 5, that is, the order of 44a → 44f → 44e → 44d → 44c → 44b → 44a (the order of FIG. 6 (G) → FIG. 6 (A)). A voltage may be applied to the rotor 42 to roll the rotor 42 in the Y direction.
[0037]
Since the rotor 42 and the drive electrode 44 and the common electrode 46 are in rolling contact with each other, the rolling friction force generated between them is extremely small. If the coefficient of static friction between the rotor 42, the drive electrode 44 and the common electrode 46 is large, it is large. Torque can be output. In other words, unless the static friction coefficient and the contact force by the electrostatic force are increased and the static friction force is set to be large, a slip occurs and a large torque cannot be generated.
[0038]
A circular hole 47 having a diameter larger than the diameter of the image guide fiber 20, specifically, a circular hole 47 having a diameter larger than the value obtained by adding the maximum eccentricity to the diameter of the image guide fiber 20 is formed on the lens side end surface 43 of the rotor 42. It is formed. Thereby, the lens side end face 43 does not block the optical path reaching the image guide fiber end face 20a regardless of the position of the rotor 42.
[0039]
7 is a view showing a change in position of the first linkage member 50 when a voltage is applied to the electrode elements in the order shown in FIG. 5, and is an end view taken along the line VII-VII in FIG. FIGS. 7A to 7G correspond to FIGS. 5A to 5G, respectively.
[0040]
When the rotor 42 rotates clockwise by an angle θ, the first pins 45a and 45b press the side surfaces of the first long holes 52a and 52b, and the first linkage member 50 rotates clockwise by the angle θ. The first axis L3 and the second axis L4 perpendicular to the first axis L3 also rotate clockwise by an angle θ, and the second pins 54a and 54b positioned on the second axis L4 also rotate around the center of the first linkage member 50 by an angle θ. Rotate clockwise. At this time, the first pins 45a and 45b are guided by the first elongated holes 52a and 52b and move along the first axis L3, whereby the first axis L3 with respect to the optical axis L1 at the center of rotation of the first linkage member 50. Misalignment is negated.
[0041]
The circular hole 56 of the first linkage member 50 is larger than the optical path from the movable lens 22 to the image guide fiber 20, and the light incident on the image guide fiber end face 20 a is blocked regardless of the position of the first linkage member 50. Absent.
[0042]
8 is a diagram showing a change in the position of the second linkage member 60 when a voltage is applied to the electrode elements in the order shown in FIG. 5, and is an end view taken along the line VIII-VIII in FIG. FIGS. 8A to 8G correspond to FIGS. 5A to 5G, respectively. The position of the first linkage member 50 is indicated by a broken line.
[0043]
When the first linkage member 50 rotates clockwise by an angle θ, the second pins 54a and 54b press the side surfaces of the second elongated holes 62a and 62b, and the second linkage member 60 rotates clockwise by the angle θ. At this time, the second pins 54a and 54b are guided by the second elongated holes 62a and 62b and move along the second axis L4, whereby the second axis L4 with respect to the optical axis L1 at the center of rotation of the second linking member 60. Misalignment is negated. Therefore, the third pins 64a and 64b and the lens holding frame 30 engaged with the third pins 64a and 64b rotate clockwise by an angle θ around the optical axis L1.
[0044]
The circular hole 66 of the second linking member 60 is larger than the optical path from the movable lens 22 to the image guide fiber 20, and the light incident on the image guide fiber end surface 20 a is blocked regardless of the position of the second linking member 60. Absent.
[0045]
Thus, in the first embodiment, the rotor 42 is rotated by rolling the rotor 42 having a smaller diameter than the inner diameter of the stator (44, 46), and this rotation is utilized as a driving force. The rotational center of the rotational driving force output from the rotor 42 is eccentric with respect to the optical axis L1, but the eccentricity is canceled by the first and second linking members 50 and 60 in the two-dimensional direction perpendicular to the optical axis L1. Since the center of rotation coincides with the optical axis L1, the lens holding frame 30 can be given a rotational driving force centered on the optical axis L1. Accordingly, the lens holding frame 30 can rotate by an angle θ per step about the optical axis L1.
[0046]
According to the first embodiment, by adopting the wobble motor mechanism 40 as a drive mechanism for moving the movable lens 22 back and forth in the direction of the optical axis L1, high torque output is possible, and a small lens drive device suitable for an endoscope or the like is obtained. It is done. In addition, since the rotor 42 and the drive electrode 44 and the common electrode 46 which are the stator are formed in an annular shape, the image guide fiber 20 can be inserted into the rotor 42 to effectively use the space in the outer cylinder 24 and reduce the diameter. That is, the outer diameter can be suppressed. Further, since the first linkage member 50 is formed as an annular plate member and the second linkage member 60 is formed as a bottomed cylindrical member, the distance between the image guide fiber distal end surface 20a and the movable lens 22 is reduced. Loss can be reduced.
[0047]
In the first embodiment, the number of electrode elements is six, but the number is not particularly limited and may be more than six. If the number of electrode elements is increased, the rotation angle θ per step of the rotor 42 is reduced, and the movable lens 22 can be smoothly advanced and retracted, and can be positioned with high accuracy.
[0048]
Next, a second embodiment of the lens driving device according to the present invention will be described with reference to FIGS. FIG. 9 is an end view when the lens driving device is cut in a cross section parallel to the optical axis. The upper half shows the retracted state of the movable lens, and the lower half shows the advanced state of the movable lens. FIG. 10 is an exploded perspective view showing the configuration of the lens driving device, and the movable lens, the lens holding frame, and the first and second linking members are not shown.
[0049]
The lens driving device of the second embodiment has the same configuration as that of the first embodiment except that the wobble motor mechanism is an electromagnetic wobble motor. The same configuration is indicated by adding 200 to the reference numerals, and description thereof is omitted.
[0050]
The wobble motor mechanism 240 is an electromagnetic wobble motor that includes a cylindrical stator having a drive magnetic pole 244 fixed to the inner peripheral surface of the outer cylinder 24 and a rotor 242 that is a magnetic body, and changes the excitation position of the drive magnetic pole 244. Thus, the magnetic attraction force that attracts the rotor 242 is changed in the circumferential direction to cause the rotor 242 to roll. The driving magnetic pole 244 is composed of twelve magnetic pole elements 270N1, 270S1, 280N1, 280S1, 290N1, 290S1, 270N2, 270S2, 280N2, 280S2, 290N2 and 290S2 that are evenly arranged in the circumferential direction. A predetermined gap is provided. The outer diameter of the cylindrical rotor 242 is smaller than the inner diameter of the drive magnetic pole 244, and the rotor 242 is accommodated inside the drive magnetic pole 244 so as to be freely movable.
[0051]
In the back of the rotor 242, three bobbin portions 272, 282 and 292 having the same shape and shape are arranged in series in order from the rotor 242 side along the optical axis L1, and the outer periphery of each of the bobbin portions 272, 282 and 292 is provided respectively. Field coils 276, 286 and 296 are wound. The first, second, and third bobbin portions 272, 282, and 292 are formed of a magnetic material, between the rotor 242 and the first bobbin portion 272, between the first bobbin portion 272 and the second bobbin portion 282, and Between the two bobbin portion 282 and the third bobbin portion 292, an annular spacer 274 made of an insulator is provided, and they are magnetically insulated from each other. The three annular spacers 274 each have a circular hole equal to the inner diameter of the bobbin portions 272, 282 and 292, and the outer diameter thereof is larger than the outer diameters of the bobbin portions 272, 282 and 292.
[0052]
The four magnetic pole elements 270N1, 270S1, 270N2 and 270S2 are strip-shaped magnetic members having a sector cross section extending from the first bobbin portion 276 in parallel to the optical axis L1. The magnetic pole elements 270N1 and 270N2 extend from the outer peripheral edge of the rotor-side flange (left side in FIG. 10) of the first bobbin portion 276 toward the rotor 242 and are point-symmetric with respect to the optical axis L. The magnetic pole elements 270N1 and 270N2 both have the same axial length, that is, the length in the optical axis L1 direction, and this axial length is long enough to cover the outer periphery of the rotor 242. The magnetic pole elements 270S1 and 270S2 extend toward the rotor 242 from the outer peripheral edge of the endoscope proximal flange (right side in FIG. 10) of the first bobbin portion 276, and their axial lengths are both equal and the magnetic pole elements The axial length of the bobbin portion 272 is longer than the axial length of 270N1 and 270N2. That is, the tip surfaces of the four magnetic pole elements 270N1, 270S1, 270N2, and 270S2 are located on the same plane perpendicular to the optical axis L1.
[0053]
A current in a fixed direction flows through the first field coil 276. At this time, the four magnetic pole elements 270N1, 270S1, 270N2, and 270S2 are excited, the magnetic pole elements 270N1 and 270N2 are set to the N pole, and the magnetic pole elements 270S1 and 270S2 are set to S. Become the pole. Magnetic pole element 270N1 (N pole) and magnetic pole element 270S1 (S pole) having different polarities, or magnetic pole element 270N2 (N pole) and magnetic pole element 270S2 (S pole) are adjacent to each other, so that the magnetic flux is between N pole and S pole. Is generated, and the rotor 42 that is a magnetic body is attracted to the magnetic pole elements 270N1 and 270S1 or the magnetic pole elements 270N2 and 270S2.
[0054]
In this way, the first stator 270 is configured by the first field coil 274, the first bobbin portion 276, and the four magnetic pole elements 270N1, 270S1, 270N2, and 270S2. The second stator 280 and the third stator 290 have the same configuration and will not be described in detail. However, the axial lengths of the magnetic pole elements are set so that the tip surfaces of all the magnetic pole elements coincide with the same plane perpendicular to the optical axis L1. Are different from each other, and the axial lengths of 290S1 and 290S2 extending from the endoscope proximal flange of the third stator 290 farthest from the rotor 242 are the longest. Around the optical axis L1, magnetic pole elements to be N poles and magnetic pole elements to be S poles are alternately arranged, for example, next to the magnetic pole element 270S1 of the first stator 270 along the X direction. The magnetic pole elements 280N1 and 280S1 of the second stator 280 are arranged in order, and the magnetic pole elements 290N1 and 290S1 of the third stator 290 are arranged in that order.
[0055]
FIG. 11 is a diagram showing a drive system of the wobble motor mechanism 240. In FIG. 11, the annular spacer 274 is omitted. The drive system of the wobble motor mechanism 240 includes a system controller 306 provided with a DC power supply 302, a switching circuit 304, and an oscillator (not shown) provided in the processor 300. First to third field coils 276, 286, and 296 are connected to DC power supply 302 via switching circuit 304, respectively.
[0056]
When switching circuit 304 energizes each field coil 276, 286, 296 in turn based on a command signal from system controller 306, rotor 242 rolls. The command signal given from the system controller 306 includes information on the rolling direction of the rotor 242 (the order of the field coils in which the driving current should flow) and the rolling amount (the number of times the driving current is switched).
[0057]
FIG. 12 is a timing chart showing an example of changes in driving current and movable lens position flowing through the field coils 276, 286, and 296 of the wobble motor mechanism 240, and FIG. 13 is an end view of the lens driving device taken along line XIII-XIII in FIG. It is.
[0058]
When one of the field coils, for example, the first field coil 276 is energized, the pair of adjacent magnetic pole elements 270N1 and 270S1 extending from the first bobbin portion 272 that accommodates the first field coil 276, and the magnetic pole Magnetic flux is generated between elements 270N2 and 270S2. The rotor 242 is attracted to the magnetic pole elements having a shorter distance from the position at the time of energization, for example, the magnetic pole elements 270N2 and 270S2 when the rotor 242 is at the position of the broken line as shown in FIG.
[0059]
Subsequently, when the energization of the first field coil 276 is stopped and the second field coil 286 is energized, the magnetic pole elements 280N1, 280S1, 280N2 and 280S2 of the second stator 280 are excited and the magnetic pole elements 280N1 and 280N1 are excited. Magnetic flux is generated between 280S1 and between 280N2 and 280S2. Then, the rotor 242 is attracted to the magnetic pole elements 280N2 and 280S2 close to the current position.
[0060]
Thus, when the field coils to be energized are switched in the order of 276, 286, and 296, the rotor 242 rolls in the X direction, and at the same time, the rolling direction about the rotor axis L2 that is eccentric from the optical axis L1. It rotates in the Y direction, which is the reverse direction. On the other hand, if the field coils 296, 286, and 276 are energized in this order, the rotor 242 rolls in the Y direction and rotates in the X direction.
[0061]
The rotation movement of the rotor 242 is converted into a linear movement in the direction of the optical axis L1 by the first linkage member 250, the second linkage member 260, and the lens holding frame 230, whereby the movable lens 222 advances and retreats along the optical axis L1.
[0062]
Also in the second embodiment, similarly to the first embodiment, by adopting a wobble motor mechanism, high torque output is possible, and a small lens driving device suitable for an endoscope or the like is obtained. Further, the rotor 242 and the stators 270, 280, 290 are formed in a cylindrical shape, so that loss of light amount can be prevented.
[0063]
As the wobble motor mechanism, an electrostatic wobble motor having a configuration different from that of the first embodiment may be used, or an electromagnetic wobble motor having a configuration different from that of the second embodiment may be used.
[0064]
As described above, the lens driving device of this embodiment includes the wobble motor mechanism in which the rotor that drives the movable lens and the stator that rolls the rotor are formed in a cylindrical shape, and the rotational motion of the rotor is converted into a linear motion in the optical axis direction. By providing the first and second linking members and the lens holding frame to be converted, the entire lens driving device can be reduced in diameter.
[0065]
【The invention's effect】
The lens driving device of the present invention can reduce the diameter of the focus adjustment mechanism of the objective lens.
[Brief description of the drawings]
FIG. 1 is a view showing an endoscope to which a lens driving device of the present embodiment is applied, and is an enlarged perspective view showing a distal end portion of the endoscope.
FIGS. 2A and 2B are end views when the lens driving device according to the first embodiment is cut in a cross section parallel to the optical axis. The upper half shows a retracted state of the movable lens, and the lower half shows an advanced state of the movable lens. .
3 is an exploded perspective view showing an internal configuration of the lens driving device of FIG. 2. FIG.
4 is a diagram showing a schematic configuration of the electrostatic wobble motor of FIG. 2;
5 is a timing chart showing changes in voltage applied to each drive electrode and common electrode of the electrostatic wobble motor of FIG. 2; FIG.
6 is a view showing the movement of the rotor of FIG. 2 in stages, and is a cross-sectional view taken along the line VI-VI of FIG.
7 is a view showing the movement of the first linkage member of FIG. 2 in stages, and is a cross-sectional view taken along the line VII-VII of FIG. 2;
8 is a view showing the movement of the second linkage member of FIG. 2 in stages, and is a cross-sectional view taken along line VIII-VIII of FIG.
FIG. 9 is an end view when the lens driving device of the second embodiment is cut in a cross section parallel to the optical axis, with the upper half showing the retracted state of the movable lens and the lower half showing the advanced state of the movable lens. .
10 is an exploded perspective view showing a configuration of the lens driving device of FIG. 9. FIG.
11 is a diagram showing a schematic configuration of the electromagnetic wobble motor of FIG. 9;
12 is a timing chart showing a change in current flowing through each drive electrode of the electromagnetic wobble motor shown in FIG. 9;
13 is a view showing the movement of the rotor of FIG. 9 in stages, and is a cross-sectional view taken along line XIII-XIII of FIG. 9;
[Explanation of symbols]
22, 222 Movable lens (optical system)
24, 224 outer cylinder
40, 240 Wobble motor mechanism
42, 242 Rotor
30 Lens holding frame (third linkage member)
50 First linkage member
60 Second linkage member
L1 optical axis
L3 1st axis
L4 Second axis

Claims (11)

An optical system supported at the tip of a cylindrical outer cylinder and capable of moving back and forth along an optical axis coinciding with the axial center of the cylindrical outer cylinder;
A wobble motor mechanism comprising a rotor having a smaller diameter than an inner diameter of the cylindrical outer cylinder, and rotating the rotor inside the cylindrical outer cylinder and rotating the rotor;
A linkage member that converts the movement of the rotor into a linear movement along the optical axis direction of the optical system ;
The linkage member is loosely fitted to the rotor so as to be relatively movable along a first axis perpendicular to the optical axis, and the optical axis and the first linkage with respect to the first linkage member. A second linkage member that is loosely fitted along a second axis perpendicular to the axis so as to be relatively movable; and a third linkage member that is loosely fitted relative to the second linkage member so as to be relatively movable in the optical axis direction. A lens driving device.   The wobble motor mechanism includes a drive electrode equally divided in the circumferential direction on the inner peripheral surface of the cylindrical outer cylinder, and a rotor of a conductor that is freely inserted inside the drive electrode, the voltage of the drive electrode The lens driving device according to claim 1, wherein the lens driving device is an electrostatic wobble motor that rotates the rotor by sequentially moving an application position in a circumferential direction.   The lens according to claim 2, wherein the wobble motor mechanism further includes an annular common electrode that is fixed to an inner peripheral surface of the cylindrical outer cylinder and through which the rotor is inserted, and is always in contact with the rotor. Drive device.   The wobble motor mechanism is freely movable inside the drive magnetic poles, a plurality of drive magnetic poles that are uniformly arranged in the circumferential direction on the inner peripheral surface of the cylindrical outer cylinder, a field coil for generating magnetic flux, and the like. The lens driving device according to claim 1, wherein the lens driving device is an electromagnetic wobble motor that includes a magnetic rotor to be inserted, and that sequentially rotates drive magnetic poles to generate magnetic flux in the circumferential direction.   2. The lens driving device according to claim 1, wherein the linking member cancels the eccentricity of the rotor, converts only the rotational motion of the rotor into motion in the optical axis direction, and transmits the motion to the optical system. The first linkage member is formed with a first elongated hole extending along the first axis, and the rotor has a first pin guided by the first elongated hole and relatively moved along the first axis. The lens driving device according to claim 1 , wherein the lens driving device is provided. The second linkage member is formed with a second slot extending along the second axis, and the first linkage member is guided by the second slot and is relatively moved along the second axis. The lens driving device according to claim 1 , wherein two pins are provided. The second linkage member is provided with a third elongated hole extending in the optical axis direction, and the third linkage member is provided with a third pin guided by the third elongated hole and relatively moved in the optical axis direction. The lens driving device according to claim 1 , wherein the lens driving device is provided. The lens driving device according to claim 1 , wherein the third linking member integrally holds the optical system and is helicoidally supported by the cylindrical outer cylinder. The lens driving device according to claim 9 , wherein the first to third linking members are positioned in the optical axis direction by the cylindrical outer cylinder.   2. The lens driving device according to claim 1, wherein a circular hole is provided at a distal end of an endoscope, and a circular hole for allowing light to enter an image guide fiber is formed in each of the rotor and the linking member.

Images