JP6597204B2 - Lens unit and imaging device - Google Patents

Description

  The present invention relates to a lens unit and an imaging device that enable displacement of a lens in the optical axis direction.

  In recent years, imaging devices such as digital still cameras and portable terminals equipped with an imaging device using a solid-state imaging device such as a CCD (Charge Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) type image sensor have become widespread. Yes. However, it is generally said that the user's needs are to promote further improvement in image quality as well as to improve the portability and design of these imaging devices. As an example of promoting high image quality, there is a case where an imaging device is provided with a focusing function for displacing a focusing lens in the optical axis direction in order to suppress blurring of a subject. On the other hand, in order to improve the portability and design of the imaging device, it is necessary to reduce the size of the imaging device.

  Here, as shown in Patent Document 1, in order to displace the focusing lens in the optical axis direction, a holding frame that holds the focusing lens via a driven portion that is in contact with the cam surface of the rotating cam member is provided. The driving technique is known. Since the rotation angle of the cam member accurately corresponds to the position of the cam surface in contact with the driven portion in the optical axis direction, the focusing lens can be displaced with high accuracy. However, if the driven part is separated from the cam surface, the position of the holding frame becomes unstable, and accurate focusing operation cannot be performed. Therefore, in Patent Document 1, a coil spring is provided that constantly urges the cam surface and the driven portion by urging the holding frame with respect to the lens frame in the optical axis direction.

JP 2006-113607 A JP 2006-98652 A

  By the way, in the technique of Patent Document 1, the rectangular parallelepiped guide body provided in the lens frame is held by a pair of guide pieces, so that the holding frame is guided in the optical axis direction with respect to the lens frame. Yes. However, if the distance between the guide pieces is too narrow compared to the width of the guide body, a competition occurs and there is a possibility that the holding frame cannot be displaced smoothly. Therefore, in order to smoothly move the holding frame, it can be said that it is preferable that the distance between the guide pieces is slightly larger than the width of the guide body. However, when the distance between the guide pieces is slightly larger than the width of the guide body, there is a backlash between the two, which may cause the holding frame to rotate around the optical axis. If the holding frame rotates about the optical axis inadvertently, the position where the driven part abuts on the cam surface will fluctuate, which may cause the position of the focusing lens in the optical axis direction to become unstable. .

  On the other hand, Patent Document 2 discloses a technique for suppressing an optical axis shift caused by a loose fit between a bearing portion and a guide shaft by using a torsion spring in an optical device that enables a zoom operation. . Therefore, it is conceivable that the cam surface and the driven part are always brought into contact with each other using the coil spring disclosed in Patent Document 1 and the guide play is eliminated using the torsion spring disclosed in Patent Document 2. However, in Patent Document 2, in the first place, a coil spring (reference numeral 18 in Patent Document 2), a torsion spring (reference numeral 20 in Patent Document 2), and a coil spring that biases a cam barrel against a lens frame (reference numeral 145 in Patent Document 2). Therefore, simply diverting such a configuration may increase the size of the imaging apparatus and increase the cost.

  The coil spring (18) used in Patent Document 2 has a function of urging the two lens groups so as to be close to each other in the optical axis direction. In order to urge each of the opposing cam surfaces. Therefore, although the distance between the optical axes of the two holding frames is accurately determined by this coil spring, the holding frame cannot be urged in the optical axis direction with the lens frame as a reference. Further, the biasing force of the coil springs generates a biasing force in the opposite direction around the optical axis in the two lens groups, which may cause decentering and the like, thereby degrading the optical performance.

  An object of the present invention is to solve the above-described problems, and to provide a lens unit capable of realizing a highly accurate displacement of the lens in the optical axis while being small in size, and an imaging apparatus using the lens unit. And

The lens unit of the present invention is
A lens,
A holding frame that includes a driven portion and holds the lens;
A lens frame provided with a guide member for guiding the holding frame in the optical axis direction;
A cam portion rotatably attached to the lens frame, provided with a cam surface that contacts the driven portion, and rotated by a driving force from a driving source;
An urging member that applies an urging force in a direction in which at least the cam surface and the driven portion are close to each other;
When the cam portion rotates, a driving force is transmitted to the holding frame via the driven portion that contacts the cam surface, and the holding frame is guided along the guide member in the optical axis direction while being guided by the guide member. It comes to displace,
The biasing force of the biasing member is directed in a direction inclined with respect to the optical axis of the lens ,
The cam portion and the lens frame are in contact with each other so that they can move relative to each other, and the frictional force acting between the cam portion and the lens frame is urged by the urging member on the cam surface. Of the normal force applied to the contact point with the drive unit, the component is smaller than the component in the contact surface direction between the cam unit and the lens frame .

  ADVANTAGE OF THE INVENTION According to this invention, the lens unit which can implement | achieve the highly accurate displacement of an optical axis direction of a lens is small, and an imaging device using the same can be provided.

It is an exploded view of the imaging device 100 including the lens unit concerning this Embodiment. It is the figure which looked at the imaging device 100 which removed the upper cover and the imaging unit in the optical axis direction. It is the figure which cut | disconnected the structure of FIG. 2 by the II-II line | wire, and looked at the arrow direction. It is sectional drawing similar to FIG. 2 of the imaging device which is a comparative example. It is a schematic diagram which shows the state which expand | deployed the cam surface 106c on the plane with the arm part 123. FIG. It is the schematic diagram which looked at the cam part from the side. It is a figure similar to FIG. 2 of the imaging device concerning a modification.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an exploded view of an imaging apparatus 100 including a lens unit according to the present embodiment. FIG. 2 is a diagram of the imaging apparatus 100 with the upper lid and the imaging unit removed as viewed in the optical axis direction. FIG. 3 is a view of the configuration of FIG. 2 taken along the line II-II and viewed in the direction of the arrow. The imaging device 100 is mounted on a mobile device such as a mobile phone and functions as a camera.

  In FIG. 1, an imaging unit 110 is attached to the lower side of a box-shaped lens frame 101 without an upper wall. The imaging unit 110 includes a rectangular substrate 111 and a photoelectric conversion unit 112 made of a CCD sensor or a CMOS sensor formed on the upper surface of the substrate 111. The imaging unit 110 is connected to a control circuit (not shown), and has a function of converting an optical image into an electrical signal and outputting it to the outside.

The lens frame 101 includes a bottom wall 101a to which the imaging unit 110 is attached, and side walls 101b to 101e extending upward from the periphery of the bottom wall 101a. An opening 101f is formed on the bottom wall 101a so as to face the photoelectric conversion portion 112, and two guide shafts 102 and 103 are implanted as guide members with the opening 101f interposed therebetween. Cylindrical guide shafts 102 and 103 extend in parallel to an optical axis direction (vertical direction in FIG. 1) of a lens LS described later.

  A semi-ring-shaped hook 104 is formed in the vicinity of the guide shaft 102 in the bottom wall 101a, and a slit groove 101g extending in the vertical direction is formed in the inner surface of the side wall 101c in the vicinity of the guide shaft 102. Yes. Although not shown, an optical sensor is arranged in the slit groove 101g.

  Further, a shaft portion 105 is planted in the vicinity of the guide shaft 102 in the bottom wall 101 a so as to extend in the vertical direction, and a cam unit 106 is rotatably disposed around the shaft portion 105. . The cam unit 106 as a cam portion has a cam piece 106b bonded or integrally formed on the upper surface of the worm wheel 106a. A cam surface 106c whose height changes in the circumferential direction is formed on the upper surface of the cam piece 106b.

  A motor 107 as a drive source is attached to the installation portion 101h of the bottom wall 101a. A worm gear 107a is attached to the rotating shaft of the motor 107, and the worm gear 107a meshes with the worm wheel 106a as shown in FIG.

  A holding frame 120 that holds a lens LS (or a plurality of lenses) that is a focusing lens is generally cylindrical and has two protruding portions 121 and 122 that protrude in a direction perpendicular to the optical axis. The protrusion 121 has a circular opening 121 a that engages with the guide shaft 102, and the protrusion 122 has an opening 122 a that engages with the guide shaft 103. Here, by making the opening 122a a long hole extending in the direction perpendicular to the optical axis, the degree of difficulty in assembly can be reduced. In such a case, it is preferable to perform the assembly reference by fitting the guide shaft 102 and the circular opening 121a.

  Further, a plate-like arm portion 123 which is a driven portion extends from the protruding portion 121 to the cam unit 106 side, and the tip thereof is in contact with the cam surface 106c as shown in FIG. Further, a plate-like arm portion 124 extends from the protruding portion 121 toward the side wall 101c of the lens frame 101, and the tip thereof enters the slit groove 101g as shown in FIG.

  A protruding portion 125 is provided so as to protrude from the protruding portion 121 adjacent to the arm portion 124. Ends of coil springs 126 as urging members are respectively attached to the collar portion 125 and the hanging portion 104 of the lens frame 101, and urge the holding frame 120 toward the bottom wall 101a side of the lens frame 101. ing. Further, the cam unit 106 is also biased toward the bottom wall 101a via the arm portion 123, whereby the position of the cam unit 106 in the optical axis direction is also fixed. As is apparent from FIG. 3, the axis AX of the coil spring 126 is inclined with respect to the optical axis OA of the lens LS, and the urging force of the coil spring 126 is exhibited along the axis AX. The lens frame 101, the lens LS, the holding frame 120, the cam unit 106, and the coil spring 126 constitute a lens unit.

  A rectangular plate-shaped upper lid 130 is attached to the upper ends of the side walls 101 b to 101 e of the lens frame 101. An opening 130 a is formed in the upper lid 130. With the lens LS and the holding frame 120 assembled between the lens frame 101 and the upper lid 130, the opening 101f of the bottom wall 101a exposes the image side of the lens LS, and the opening 130a of the upper lid 130 faces the object side. It is supposed to be exposed. In this state, the holding frame 120 can be displaced in the optical axis direction.

  Next, the operation of the imaging apparatus according to this embodiment will be described. First, the origin adjustment at the time of assembly will be described. The motor 107 generates a pulse signal corresponding to the rotation angle. When the motor 107 is rotationally driven by supplying power from a power source (not shown), the cam unit 106 is rotated via the worm gear 107a and the worm wheel 106a. An optical sensor (not shown) detects the tip position of the arm part 124 that has entered the slit groove 101g, thereby determining the position in the optical axis direction that serves as a reference for the lens LS. When the reference position is reached, the rotation of the motor 107 is stopped. Such a state is stored as the origin, and the number of pulses generated when the motor 107 rotates in the reverse direction from this position is counted, so that the cam unit 106 from the origin is in accordance with the reduction ratio of the worm gear 107a and the worm wheel 106a. The amount of rotation can be calculated.

  At the time of shooting, when the lens LS of the imaging apparatus 100 mounted on an imaging device (not shown) is directed toward the subject, the subject light incident through the lens LS forms an image on the photoelectric conversion unit 112 of the imaging unit 110. The photoelectric conversion unit 112 changes the image of the subject into an electrical signal and outputs it to a liquid crystal display (not shown). Thereby, the image of the subject is displayed on the display. When the user performs a release operation at an appropriate timing, the subject is imaged, the image data is output from the photoelectric conversion unit 112, and after predetermined image processing, is recorded in a memory (not shown).

  The imaging apparatus 100 according to the present embodiment can perform a focusing operation by displacing the lens unit in the optical axis direction according to the distance of the subject. After measuring the distance to the subject (subject distance) with a distance measuring device (not shown), when the motor 107 is driven to rotate forward to rotate the worm gear 107a, the worm wheel 106a rotates in the forward direction, and the cam unit 106 Rotate in the same direction. Here, since the tip of the arm portion 123 is pressed against the cam surface 106c of the cam piece 106b by the biasing force of the coil spring 126, the height position of the cam surface 106c changes according to the rotation of the cam unit 106. Accordingly, the holding frame 120 together with the arm portion 123 is displaced in the optical axis direction while being guided by the guide shafts 102 and 103, and the lens LS can be displaced to a position in the optical axis direction suitable for the subject distance.

  By the way, in the present embodiment, in order to increase the resolution in the displacement in the optical axis direction of the lens LS, the inclination of the cam surface 106c in the cam piece 106b is made gentler than in the prior art. For this reason, the problem resulting from the direction of the force produced between the cam surface 106c and the arm part 123 has arisen. Such a problem will be described with reference to a comparative example.

  FIG. 4 is a cross-sectional view similar to FIG. 2 of an imaging apparatus as a comparative example. In the comparative example of FIG. 4, the axis AX of the coil spring 126 is parallel to the optical axis OA of the lens LS. Further, the inclination of the cam surface 106c of the comparative example is tighter than the inclination of the cam surface 106c of the present embodiment. Other configurations are the same as those in the above-described embodiment. FIGS. 5A and 5B are schematic views showing a state where the cam surface 106c is developed in a plane together with the arm portion 123. FIG. 5A corresponds to the present embodiment, and FIG. 5B corresponds to a comparative example. The angle difference is exaggerated to make it easier. In FIG. 5, the vertical direction is the optical axis direction, and the horizontal direction is the optical axis orthogonal direction.

  Here, in the case of the comparative example in FIG. 5B, the inclination angle θ2 of the cam surface 106c is relatively large. Therefore, when a reaction force F2 is generated at the contact point P2 between the cam surface 106c and the arm portion 123 based on the urging force of the coil spring 12, the component perpendicular to the optical axis is F2 · sin θ2.

  Here, the guide shaft 102 is engaged with the circular opening 121a of the holding frame 120, and the guide shaft 103 is engaged with the opening 122a of the holding frame 120. To do. However, in the comparative example, since the optical axis orthogonal direction component F2 · sin θ2 applied from the cam surface 106c to the arm portion 123 is relatively large, the holding frame 120 is biased in the optical axis orthogonal direction by the optical axis orthogonal direction component. As a result, when the guide shafts 102 and 103 are pressed in a certain direction, the play is effectively removed.

  On the other hand, in the case of the present embodiment in FIG. 4A, the inclination angle θ1 of the cam surface 106c is smaller than the inclination angle θ2 of the comparative example. Therefore, when the reaction force F1 is generated at the contact point P1 between the cam surface 106c and the arm portion 123 based on the biasing force of the coil spring 126, the component orthogonal to the optical axis is F1 · sin θ1, but F1 = F2. Then, from θ1 <θ2, F1 · sin θ1 <F2 · sin θ2. That is, as the inclination angle of the cam surface 106c decreases, the component of the reaction force in the direction perpendicular to the optical axis, that is, the force that biases the arm portion 123 in the direction orthogonal to the optical axis decreases.

  Therefore, in the present embodiment, the force for urging the arm portion 123 in the direction perpendicular to the optical axis is relatively small, so that the force for pressing the holding frame 120 against the guide shafts 102 and 103 is weak, and some external force causes There is a possibility that the holding frame 120 is displaced in the direction orthogonal to the optical axis with respect to the lens frame 101 by the amount of play. In this case, since the arm portion 123 is also displaced together with the holding frame 120, the position where the tip abuts against the cam surface 106c is changed, and thus the lens LS is not rotated even though the cam surface 106c is not rotated. The position in the optical axis direction is displaced, and there is a possibility of causing a focus shift.

  This problem is solved in the present embodiment as follows. In the present embodiment, the axis AX of the coil spring 126 is inclined with respect to the optical axis OA of the lens LS. That is, the urging force of the coil spring 126 is directed in a direction inclined with respect to the optical axis direction. For this reason, as shown in FIGS. 2 and 3, a component force Fh directed in the direction orthogonal to the optical axis is generated in the flange portion 125 to which one end of the coil spring 126 is attached. Therefore, even when the inclination of the cam surface 106c is gentle, the holding frame 120 can be pressed in one direction with respect to the guide shafts 102 and 103 by being biased in the direction orthogonal to the optical axis by the component force Fh. . As a result, for example, even when a loose fit occurs between the circular opening 121a and the guide shaft 102, the guide shaft 102 is relatively offset with respect to the circular opening 121a, so that the play is removed. It is possible to provide guidance.

  According to the present embodiment, the holding frame 120 is arranged in the optical axis direction and the optical axis by using only the single coil spring 126 without separately providing biasing means for biasing the holding frame 120 in the direction orthogonal to the optical axis. Since it can be urged in the orthogonal direction, the contact between the cam surface 106c and the arm portion 123 can be stably performed, the backlash between the holding frame 120 and the guide shafts 102 and 103 can be eliminated, and the lens LS can be removed. It can be positioned at the in-focus position with high accuracy.

  Furthermore, another problem may be caused by reducing the inclination of the cam surface 106c. When the inclination of the cam surface 106c is loose, the component of the force that urges the cam unit 106 in the rotational direction out of the force applied from the arm portion 123 to the cam surface 106c becomes small. As a result, the backlash caused by the backlash between the worm wheel 106a that drives the cam piece 106b and the worm gear 107a cannot be completely eliminated, and the position where the arm portion 123 abuts on the cam surface 106c may become unstable. In this embodiment, such a problem can be solved.

  FIG. 6 is a schematic view of the cam unit of the present embodiment as viewed from the side. The cam piece 106b and the worm wheel 106a are integrated, but the cam unit 106 is configured to slide with respect to the bottom wall 101a of the lens frame 101.

  According to the law of action and reaction, a pressing force F1 equal to the reaction force F1 (see FIG. 5) at the contact P1 is applied from the arm portion 123 to the cam surface 106c. When the inclination angle of the cam surface 106c with respect to the bottom wall 101a is θ1, the pressing force F1 includes a component F1 · cos θ1 orthogonal to the bottom wall 101a and a component parallel to the bottom wall 101a (here, the arm portion on the cam surface 106c). Of the normal direction force applied to the contact point P1 with the contact point 123, the component in the contact surface direction between the bottom wall 101a and the worm wheel 106a) F1 · sin θ1 can be decomposed. In this case, when the friction coefficient between the bottom wall 101a and the worm wheel 106a is μ, the frictional force acting between the bottom wall 101a and the worm wheel 106a is expressed by μF1 · cos θ1. At this time, if μF1 · cos θ1 <F1 · sin θ1, that is, μ <tan θ1, the cam unit 106 can be rotated by overcoming the frictional force with the bottom wall 101a. By pressing the gear teeth in one direction against the gear teeth of the worm gear 107a, the play between the gear teeth can be eliminated.

  FIG. 7 is a diagram similar to FIG. 2 of an imaging apparatus according to a modification. In this modification, the hanging portion 104 of the lens frame 101 is shifted to the holding frame 120 side with respect to the above-described embodiment. Accordingly, the axis of the coil spring 126 is inclined in the vertical and horizontal directions in the drawing with respect to the optical axis OA (extending in the direction perpendicular to the paper surface in FIG. 7), and accordingly, in the flange portion 125 by the biasing force of the coil spring 126. The generated component force Fh in the direction perpendicular to the optical axis is divided into a component Fhx going upward and a component Fhy going left.

  Here, the cam surface 106c has a shape that becomes lower (approaches the bottom wall 101a) as it goes clockwise around the shaft portion 105 as viewed in the direction of FIG. That is, at the position where the arm portion 123 abuts, the cam surface 106c is inclined so as to become lower from the left to the right in the figure, so the normal line at the contact point of the arm portion 123 on the cam surface 106c is as shown in FIG. It is inclined in the left-right direction with respect to the direction perpendicular to the paper surface.

  In the case of this modification, since the axis of the coil spring 126 is inclined as described above, a component Fhy directed to the left side through the flange 125 is generated with respect to the embodiment of FIG. Similar to the embodiment, the guide shaft 102 is relatively offset with respect to the circular opening 121a, and the force applied from the arm portion 123 to the cam surface 106c is It approaches the normal direction of the cam surface 106c with respect to the direction extending in parallel to the optical axis from the contact point. That is, the value of the force F1 shown in FIG. 6 increases. As a result, even when the urging force of the coil spring 126 is the same, the urging force in the rotational direction of the cam piece 106b is increased as compared with the above-described embodiment, and the gear teeth of the worm wheel 106a are moved relative to the gear teeth of the worm gear 107a. By pressing in one direction, it becomes easy to eliminate the play between the gear teeth.

DESCRIPTION OF SYMBOLS 100 Imaging device 101 Mirror frame 101a Bottom wall 101b-101e Side wall 101f Opening part 101g Slit groove 101h Installation part 102 Guide shaft 103 Guide shaft 104 Hook part 105 Shaft part 106 Cam unit 106a Worm wheel 106b Cam piece 106c Cam surface 107 Motor 107a Worm gear 110 Imaging unit 111 Substrate 112 Photoelectric conversion unit 120 Holding frame 121 Protruding part 121a Circular opening 122 Protruding part 122a Opening 123 Arm part 124 Arm part 125 Hook part 126 Coil spring 130 Upper lid 130a Opening part LS Lens OA Optical axis

Claims (3)

A lens,
A holding frame that includes a driven portion and holds the lens;
A lens frame provided with a guide member for guiding the holding frame in the optical axis direction;
A cam portion rotatably attached to the lens frame, provided with a cam surface that contacts the driven portion, and rotated by a driving force from a driving source;
An urging member that applies an urging force in a direction in which at least the cam surface and the driven portion are close to each other;
When the cam portion rotates, a driving force is transmitted to the holding frame via the driven portion that contacts the cam surface, and the holding frame is guided along the guide member in the optical axis direction while being guided by the guide member. It comes to displace,
The biasing force of the biasing member is directed in a direction inclined with respect to the optical axis of the lens ,
The cam portion and the lens frame are in contact with each other so that they can move relative to each other, and the frictional force acting between the cam portion and the lens frame is urged by the urging member on the cam surface. A lens unit having a component smaller than a component in a contact surface direction between the cam portion and the lens frame in a normal direction force applied to a contact point with the drive portion .   The force urged from the driven portion to the cam surface by the urging member is a direction approaching a normal line passing through the contact point of the driven portion in the cam surface with respect to the optical axis direction, and the 2. The lens unit according to claim 1, wherein the lens unit is inclined in a direction in which a fitting backlash between the guide member for guiding the holding frame in the optical axis direction and the holding frame can be shifted to one side. An image sensor for photoelectrically converting an object image, an imaging apparatus characterized by comprising a lens unit according to claim 1 or 2.

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