Lens barrel

Abstract

To provide a lens barrel that improves lens drive force.SOLUTION: To provide a lens barrel improving lens drive force, the lens barrel comprises: a first yoke and second yoke that have a length in an optical axis direction; a third yoke that has the length in the optical axis direction, and is arranged between the first yoke and the second yoke; a first magnet that is arranged in the first yoke; a second magnet that is arranged in the second yoke; a coil that is penetrated into the third yoke, and movable in the optical axis direction by magnetic force of the first magnet and second magnet; and a lens holding frame that holds a lens, and is movable in the optical axis direction integrally with the coil, in which a first plane surface including a first lateral surface distant from the third yoke of facing two lateral surfaces of the first yoke in a circumferential direction of the lens, and a second plane surface including a second lateral surface distant from the third yoke of facing two lateral surfaces of the second yoke in the circumferential direction go across each other.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] Regarding the lens barrel. [Background technology]

[0002] A lens barrel that employs a voice coil motor as a lens driving device has been proposed (for example, Patent Document 1). In the lens barrel, improvement of the driving force is desired. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-49334 A Summary of the Invention

[0004] According to a first aspect, a lens barrel includes a first yoke and a second yoke having a length in the optical axis direction, a third yoke having a length in the optical axis direction and arranged between the first yoke and the second yoke, a first magnet arranged on the first yoke, a second magnet arranged on the second yoke, a coil that penetrates the third yoke and is movable in the optical axis direction by the magnetic force of the first magnet and the second magnet, and a lens holding frame that holds a lens and is movable in the optical axis direction integrally with the coil, and a first plane that includes a first side surface that is farther from the third yoke of two side surfaces of the first yoke that face each other in the circumferential direction of the lens intersects with a second plane that includes a second side surface that is farther from the third yoke of two side surfaces of the second yoke that face each other in the circumferential direction.

[0005] According to a second aspect, an imaging device includes the above-described lens barrel.

[0006] The configurations of the embodiments described below may be appropriately improved, and at least a part of them may be replaced with other components. Furthermore, components that are not particularly limited in terms of their location may be located in any location that can achieve their function, not limited to the location disclosed in the embodiments. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a camera including a lens barrel and a camera body according to an embodiment. [Diagram 2] FIG. 2(A) is an oblique view of the voice coil motor according to the first embodiment, FIG. 2(B) is a view of the voice coil motor from the direction indicated by the arrow AR1 in FIG. 2(A), and FIG. 2(C) is a view of the voice coil motor from the direction indicated by the arrow AR2 in FIG. 2(A). [Diagram 3] 3A is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 3B is an enlarged view of the periphery of the voice coil motor in FIG. 3A. [Figure 4] FIG. 4(A) shows an example in which a voice coil motor according to a comparative example is arranged between a first fixed barrel 10 and a second fixed barrel 20, and FIG. 4(B) is an enlarged view of the periphery of the voice coil motor in FIG. 4(A). [Diagram 5] FIG. 5 is an enlarged view of the periphery of the voice coil motor in FIG. [Figure 6] FIG. 6 is a diagram for explaining the arrangement of the first and second side yokes. [Figure 7] FIG. 7 is a diagram showing an outline of a model used to consider the arrangement of the first and second side yokes. [Figure 8] FIG. 8 is a diagram showing an outline of a model used to consider the arrangement of the first and second side yokes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A lens barrel 100 according to an embodiment will be described in detail below with reference to the drawings. Note that in each drawing, some elements may be omitted in order to facilitate understanding.

[0009] 1 is a diagram showing a camera 1 including a lens barrel 100 according to this embodiment and a camera body 101. Note that in this embodiment, the lens barrel 100 is detachable from the camera body 101, but is not limited to this, and the lens barrel 100 and the camera body 101 may be integrated.

[0010] Camera body 101 includes therein an image sensor 111 and a control unit 112. Image sensor 111 is composed of a photoelectric conversion element such as a CCD (Charge Coupled Device), and converts a subject image formed by an imaging optical system (lens barrel 100 attached to camera body 101) into an electrical signal.

[0011] The control unit 112 includes a CPU (Central Processing Unit) and the like, and controls the overall operation of the camera 1 relating to photography, including the focusing drive of the camera body 101 and the attached lens barrel 100.

[0012] As shown in Fig. 1, the lens barrel 100 according to this embodiment includes a first fixed barrel 10 and a second fixed barrel 20 arranged on the inner peripheral side of the first fixed barrel 10. In this embodiment, the first fixed barrel 10 is made up of multiple parts, but it may be made up of a single part. As shown in Fig. 1, a lens mount LM that enables the lens barrel 100 to be attached to and detached from a camera body 101 is fixed to the first fixed barrel 10.

[0013] Furthermore, the lens barrel 100 includes multiple lenses L1 to L4 arranged in sequence along a common optical axis OA. The lens L3 is held in a lens holding frame F3, and the other lenses are held in a second fixed barrel 20. Each of the lenses L1 to L4 may be composed of multiple lenses.

[0014] The lens barrel 100 also includes a guide bar 22 that guides the lens holding frame F3 in the optical axis direction. The guide bar 22 is fixed to the second fixed barrel 20. Instead of the guide bar 22, the lens holding frame F3 may be guided in the optical axis direction by a rectilinear groove extending in the optical axis direction.

[0015] In this embodiment, the lens L3 is a focus lens that is moved in the optical axis direction to adjust the focus. The lens L3 is provided so as to be moved in the optical axis direction by a voice coil motor (VCM) 30 disposed inside the lens barrel 100.

[0016] The VCM 30 is driven by a driving device 113. The driving device 113 controls the focusing drive of the lens L3 under the control of the control unit 112 of the camera body 101. Specifically, the driving device 113 generates a driving signal for the VCM 30 based on position information of the lens L3 input from a position detection mechanism (not shown) such as an optical encoder or a magnetic encoder, and target position information of the lens L3 input from the control unit 112 of the camera body 101, and outputs the driving signal to the VCM 30.

[0017] The VCM 30 drives the lens L3 linearly in the optical axis direction by the drive signal. As will be described in detail later, as shown in FIG. 1, a coil 35 included in the VCM 30 is connected to the lens holding frame F3. Specifically, the lens holding frame F3 is connected to the coil 35 via a connecting portion 115 of the lens holding frame F3, for example, by adhesive. As a result, when the coil 35 is driven linearly in the optical axis direction, the lens holding frame F3 is driven linearly in the optical axis direction, and the position of the lens L3 in the optical axis direction changes.

[0018] When the drive signal of the VCM 30 is OFF, the coil 35 of the VCM 30 does not have a holding force to maintain its position and therefore moves freely. Therefore, when the lens barrel 100 is turned up or down, the coil 35 moves due to the weight of the lens holding frame F3 and the lens L3, and the lens holding frame F3 may collide with the second fixed barrel 20, generating an impact noise. Therefore, as shown in FIG. 1, a cushioning material 40 is provided at a portion of the second fixed barrel 20 that overlaps with the lens holding frame F3 in the optical axis direction. As a result, the connecting portion 115 collides with the cushioning material 40, thereby mitigating the impact and suppressing the impact noise.

[0019] In camera 1, which is composed of camera body 101 and lens barrel 100 as described above, when a shutter button (not shown) is pressed (release operation or focus operation), control unit 112 in camera body 101 controls focusing drive of lens barrel 100 and the like via drive device 113. In addition, image sensor 111 converts subject image light formed by lens barrel 100 into an electrical signal, and the image data is recorded (i.e., photographed) in a memory (not shown) provided in camera body 101.

[0020] Next, the configuration of the VCM30 that drives the lens L3 will be described. Fig. 2(A) is a perspective view showing the configuration of the VCM30, Fig. 2(B) is a view of the VCM30 seen from the direction of the arrow AR1 in Fig. 2(A), and Fig. 2(C) is a view of the VCM30 seen from the direction of the arrow AR2 in Fig. 2(A). Fig. 3(A) is a cross-sectional view taken along the line AA in Fig. 1, and Fig. 3(B) is an enlarged view of the vicinity of the VCM30 in Fig. 3(A).

[0021] As shown in FIG. 2(A), the VCM 30 of this embodiment includes a first side yoke 31a and a second side yoke 31b having a length in the optical axis direction, and a center yoke 32 having a length in the optical axis direction and disposed between the first side yoke 31a and the second side yoke 31b.

[0022] 3A and 3B, the cross sections of the first side yoke 31a and the second side yoke 31b in a plane perpendicular to the optical axis OA are rectangular, and the cross-sectional areas of the first side yoke 31a and the second side yoke 31b in the plane perpendicular to the optical axis OA are uniform along the optical axis OA. The cross section of the center yoke 32 in the plane perpendicular to the optical axis OA is substantially circular, and the cross-sectional area of ​​the center yoke 32 in the plane perpendicular to the optical axis OA is uniform along the optical axis OA.

[0023] The VCM 30 also includes an upper yoke 34a that connects one ends in the optical axis direction of the first side yoke 31a, the second side yoke 31b, and the center yoke 32, and a lower yoke 34b that connects the other ends in the optical axis direction of the first side yoke 31a, the second side yoke 31b, and the center yoke 32. This forms a closed magnetic path.

[0024] A first magnet 33a is disposed on the side surface of the first side yoke 31a facing the center yoke 32, and a second magnet 33b is disposed on the side surface of the second side yoke 31b facing the center yoke. As shown in Figures 3(A) and 3(B), the cross sections of the first magnet 33a and the second magnet 33b in a plane perpendicular to the optical axis OA have a rectangular shape, and the cross-sectional areas of the first magnet 33a and the second magnet 33b in the plane perpendicular to the optical axis OA are uniform along the optical axis OA.

[0025] 2(B), the first magnet 33a is arranged, for example, so that its north pole faces the center yoke 32, and the second magnet 33b is also arranged so that its north pole faces the center yoke 32. This forms a magnetic path in which magnetic flux enters the center yoke 32 from the north poles of the first magnet 33a and the second magnet 33b, passes through the upper yoke 34a and the lower yoke 34b and the first side yoke 31a and the second side yoke 31b, and returns to the south poles of the first magnet 33a and the second magnet 33b, as shown by the arrows in FIG.

[0026] The first and second side yokes 31a, 31b and the upper and lower yokes 34a, 34b are made of, for example, cold rolled steel plate (SPCC: Steel Plate Cold Commercial), and the center yoke 32 is made of, for example, SS (Steel Structure)400.

[0027] The VCM 30 also includes a coil 35 that penetrates the center yoke 32. There is a small gap between the inner peripheral surface of the coil 35 and the center yoke 32A, allowing the coil 35 to move in the optical axis direction. The coil 35 is also configured so that the direction of magnetic flux that converges from the first side yoke 31a and the second side yoke 31b to the center yoke 32 is perpendicular to the winding direction of the coil 35.

[0028] A driving signal (current) is input to the coil 35 from the driving device 113. When a current flows through the coil 35, the coil 35 moves in the optical axis direction due to the magnetic force of the first magnet 33a and the second magnet 33b. More specifically, the coil 35 moves in the optical axis direction due to electromagnetic interaction between the coil 35 through which a current flows and the first magnet 33a and the second magnet 33b. By changing the direction of the current flowing through the coil 35, the moving direction of the coil 35 can be switched between the subject side and the camera body 101 side (image surface side). In addition, by changing the value of the current flowing through the coil 35, the driving force and moving speed of the coil 35 can be changed.

[0029] In this embodiment, the VCM 30 is disposed between the first fixed barrel 10 and the second fixed barrel 20, as shown in Fig. 3(A). Therefore, as shown in Fig. 2(C), the upper yoke 34a (and the lower yoke 34b) has an arc shape, and as shown in Fig. 3(A) and Fig. 3(B), the first side yoke 31a and the second side yoke 31b are disposed non-parallel. Since the first side yoke 31a and the second side yoke 31b are disposed non-parallel, the VCM 30 can be disposed efficiently between the first fixed barrel 10 and the second fixed barrel 20.

[0030] More specifically, as shown in Fig. 3(A), in the VCM30, a plane P1 including a side surface SF1 farther from the center yoke 32 among two side surfaces of the first side yoke 31a facing each other in the circumferential direction of the lens L3 intersects with a plane P2 including a side surface SF2 farther from the center yoke 32 among two side surfaces of the second side yoke 31b facing each other in the circumferential direction. The planes P1 and P2 intersect at a position different from the center point C1 of the lens L3. That is, the intersection line IL1 between the planes P1 and P2 does not intersect with the center point C1 of the lens L3. The center point C1 of the lens L3 is located between the center yoke 32 and the intersection line IL1.

[0031] In addition, in a plane perpendicular to the optical axis OA, the intersection line IL1 is on a straight line connecting the center point C2 of the center yoke 32 and the center point C1 of the lens L3. In other words, in a plane perpendicular to the optical axis OA, the center point C2 of the center yoke 32, the center point C1 of the lens L3, and the intersection line IL1 are on a straight line. In addition, the intersection line IL1 intersects with the lens L3.

[0032] Furthermore, since the first side yoke 31a and the second side yoke 31b are arranged non-parallel, the first magnet 33a and the second magnet 33b attached to the side surfaces of the first side yoke 31a and the second side yoke 31b on the center yoke 32 side, respectively, are also non-parallel. More specifically, a plane P3 including a side surface SF3 farther from the center yoke 32 among two side surfaces of the first magnet 33a facing each other in the circumferential direction of the lens L3 intersects with a plane P4 including a side surface SF4 farther from the center yoke 32 among two side surfaces of the second magnet 33b facing each other in the circumferential direction. In addition, an intersection line IL2 between the plane P3 and the plane P4 intersects with the lens L3. In addition, the intersection line IL2 is located between the center yoke 32 and the center point C1 of the lens L3. More specifically, the intersection line IL2 is on a straight line connecting the center point C2 of the center yoke 32 and the center point C1 of the lens L3.

[0033] 4A shows an example in which a VCM30X according to a comparative example is disposed between a first fixed barrel 10 and a second fixed barrel 20. In the VCM30X according to the comparative example, the first side yoke 31a and the second side yoke 31b are disposed non-parallel to each other, as in the VCM30. However, in the comparative example, an intersection line IL1 between a plane P1 including a side surface SF1 of the first side yoke 31a and a plane P2 including a side surface SF2 of the second side yoke 31b intersects with a center point C1 of the lens L3. Other configurations are similar to those of the VCM30, and therefore detailed description thereof will be omitted.

[0034] Fig. 4(B) is an enlarged view of the periphery of the VCM30X in Fig. 4(A). As shown in Fig. 4(B), in the VCM30X according to the comparative example, in a plane perpendicular to the optical axis OA, a distance d3 between an outer circumferential corner CR1 of the first magnet 33a on the center yoke 32 side and a center point C2 of the center yoke 32 is longer than a distance d4 between an inner circumferential corner CR2 of the first magnet 33a on the center yoke 32 side and a center point C2 of the center yoke 32. Therefore, the magnetic field on the outer circumferential side is weaker than the magnetic field on the inner circumferential side, and the VCM30X according to the comparative example may not be able to obtain a desired driving force.

[0035] On the other hand, in the VCM30 of this embodiment, as shown in FIG. 3(A), the first side yoke 31a and the second side yoke 31b are arranged so that the intersection line IL1 between a plane P1 including the side surface SF1 of the first side yoke 31a and a plane P2 including the side surface SF2 of the second side yoke 31b does not intersect with the center point C1 of the lens L3, and the center point C1 of the lens L3 is located between the center yoke 32 and the intersection line IL1.

[0036] 5, the difference (d1-d2) between the distance d1 between the outer circumferential corner CR1 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32 and the distance d2 between the inner circumferential corner CR2 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32 is smaller than the difference (d3-d4) between the distance d3 and the distance d4 in the VCM30X according to the comparative example. As a result, the magnetic field on the outer circumferential side is stronger in the VCM30 than in the VCM30X of the comparative example, and the driving force of the VCM30 is improved compared to the VCM30X of the comparative example. Therefore, the lens L3 can be driven stably.

[0037] 6, in the VCM 30, the angle β between the line connecting the center point C2 of the center yoke 32 and the center point C1 of the lens L3 and the plane P1 including the side surface SF1 of the first side yoke 31a is set to a range of 5.4° to 11°. The same applies to the angle between the line connecting the center point C2 of the center yoke 32 and the center point C1 of the lens L3 and the plane P2 including the side surface SF2 of the second side yoke 31b.

[0038] In addition, in a plane perpendicular to the optical axis OA, when the angle α formed by a straight line connecting the corner CR3 of the first side yoke 31a on the lens L3 side and far from the center yoke 32 and the center point C1 of the lens L3 and a straight line connecting the center point C2 of the center yoke 32 and the center point C1 of the lens L3 is within the range of 16° to 17°, the angle β formed by the straight line connecting the center point C2 of the center yoke 32 and the center point C1 of the lens L3 and the plane P1 and the plane P2 is within the range of 7.8° to 8.3°.

[0039] This makes it possible to make the distance between the outer circumferential corner CR1 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32 approximately equal to the distance between the inner circumferential corner CR2 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32, thereby improving the driving force of the VCM 30.

[0040] The arrangement of the first side yoke 31a and the second side yoke 31b was examined. Figures 7 and 8 are diagrams showing an outline of a model used to examine the arrangement of the first side yoke 31a and the second side yoke 31b. The coil 35 is omitted from Figures 7 and 8. The two-dot chain line and the three-dot chain line correspond to the outer peripheral surface of the second fixed barrel 20 and the inner peripheral surface of the first fixed barrel 10, respectively.

[0041] As shown in FIGS. 7 and 8, the coordinates of the central axis O of the lens L3 are (0,0), the side yoke and the magnet are approximated by a rectangle R1, and the vertices of the rectangle are A1, A2, A3, and A4.

[0042] Also, the length (width) of the rectangle R1 in the longitudinal direction is W, and the length (thickness) of the rectangle R1 in the lateral direction is t. In a plane perpendicular to the optical axis OA, the length of a straight line L11 connecting the apex A1 of the rectangle R1 and the central axis O of the lens L1 is R, the angle between the straight line connecting the center point C2 of the center yoke 32 and the central axis O of the lens L1 and the straight line L11 connecting the apex A1 of the rectangle R1 and the central axis O of the lens L1 is α, and the angle between the straight line connecting the center point C2 of the center yoke 32 and the central axis O of the lens L1 and the straight line L12 passing through the apex A3 and the apex A1 of the rectangle R1 is β. The case of α=β (the case of FIG. 7) corresponds to a comparative example.

[0043] With the above assumptions, the coordinates of the vertices A1 to A4 of the rectangle R1 and the center point C2 of the center yoke 32 are as follows: Coordinates of A1: (R cosα, R sinα) Coordinates of A2: (R cosα+t sinβ, R sinα-t cosβ) Coordinates of A3: (R·cosα+W·cosβ,R·sinα+W·sinβ) Coordinates of A4: (R·cosα+W·cosβ+t·sinβ,R·sinα+W·sinβ-t·cosβ) Coordinates of C2: (R+0.5W,0)

[0044] The values ​​of R, W, t, α, and β were changed to calculate the distance D1 between the apex A2 and the center point C2 of the center yoke 32, and the distance D2 between the apex A4 and the center point C2 of the center yoke 32. The calculation results are shown in Table 1.

[0045] [Table 1]

[0046] Here, the smaller the difference between distance D1 and distance D2, the smaller the difference in strength between the magnetic field on the outer periphery side and the magnetic field on the inner periphery side, and the more the driving force of the voice coil motor can be improved. As shown in Examples 1 to 11, even when each dimension is changed, the difference between distance D1 and distance D2 can be reduced if β is within the range of 5.4° to 11°.

[0047] Furthermore, for example, as shown in Examples 1 to 3, 8, and 11, when α=16° to 17°, by setting β to 7.8° to 8.3°, the difference between the distance D1 and the distance D2 can be reduced regardless of the magnitude of R.

[0048] As described above in detail, the lens barrel 100 according to this embodiment includes the first side yoke 31a and the second side yoke 31b having a length in the optical axis direction, the center yoke 32 having a length in the optical axis direction and disposed between the first side yoke 31a and the second side yoke 31b, the first magnet 33a disposed in the first side yoke 31a, the second magnet 33b disposed in the second side yoke 31b, a coil 35 that penetrates the center yoke 32 and is movable in the optical axis direction by the magnetic forces of the first magnet 33a and the second magnet 33b, and a lens holding frame F3 that holds the lens L3 and is movable in the optical axis direction together with the coil 35. A plane P1 including the side SF1 farther from the center yoke 32 of the two side surfaces of the first side yoke 31a that face each other in the circumferential direction of the lens L3 intersects with a plane P2 including the side SF2 farther from the center yoke 32 of the two side surfaces of the second side yoke 31b that face each other in the circumferential direction. That is, the first side yoke 31a and the second side yoke 31b are arranged non-parallel to each other. This allows the VCM 30 to be efficiently arranged between the first fixed barrel 10 and the second fixed barrel 20. Furthermore, the VCM 30 can be made smaller in size in the radial direction of the lens L3 than when the first side yoke 31a and the second side yoke 31b are arranged in parallel to each other.

[0049] In this embodiment, the planes P1 and P2 intersect at a position different from the center point C1 of the lens L3. Furthermore, the center point C1 of the lens L3 is located between the intersection line IL1 between the planes P1 and P2 and the center yoke 32.

[0050] 5, by arranging the first side yoke 31a and the second side yoke 31b in this manner, it is possible to reduce the difference (d1-d2) between the distance d1 between the outer circumferential corner CR1 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32, and the distance d2 between the inner circumferential corner CR2 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32, thereby reducing the difference in strength between the magnetic field on the outer circumferential side and the magnetic field on the inner circumferential side, thereby improving the driving force of the voice coil motor. This allows the lens L3 to be driven stably.

[0051] Furthermore, according to this embodiment, in a plane perpendicular to the optical axis OA, the intersection line IL1 between the plane P1 and the plane P2 is on a straight line connecting the center point C2 of the center yoke 32 and the center point C1 of the lens L3. That is, in a plane perpendicular to the optical axis OA, the first side yoke 31a and the second side yoke 31b are disposed symmetrically with respect to the straight line connecting the center point C2 of the center yoke 32 and the center point C1 of the lens L3. This makes it possible to equalize the strength of the magnetic field between the first magnet 33a and the center yoke 32 and the strength of the magnetic field between the second magnet 33b and the center yoke 32, thereby enabling the lens L3 to be driven stably.

[0052] Moreover, according to this embodiment, the intersection line IL1 between the plane P1 and the plane P2 intersects with the lens L3. As a result, even if the shape of the upper yoke 34a (and the lower yoke 34b) is made into an arc shape as shown in FIG. 1C, the difference between the distance d1 between the outer circumferential corner CR1 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32 and the distance d2 between the inner circumferential corner CR2 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32 can be made small. Therefore, a VCM that has a high driving force and can be arranged in the lens barrel 100 can be realized.

[0053] In this embodiment, in a plane perpendicular to the optical axis OA, the angle β formed by the straight line connecting the center point C2 of the center yoke 32 and the center point C1 of the lens L3 and the plane P1 including the side surface SF1 of the first side yoke 31a and the plane P2 including the side surface SF2 of the second side yoke 31b is set to a range of 5.4° to 11°. As a result, as shown in Table 1, it is possible to reduce the difference between the distance d1 between the outer circumferential corner CR1 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32 and the distance d2 between the inner circumferential corner CR2 of the first magnet 33a on the center yoke 32 side and the center point C2 of the center yoke 32, and therefore the difference between the magnetic field strength on the outer circumferential side and the magnetic field strength on the inner circumferential side can be reduced, thereby improving the driving force of the VCM 30.

[0054] Furthermore, in a plane perpendicular to the optical axis OA, when the angle α formed by the line connecting the corner CR3 of the first side yoke 31a on the lens L3 side and far from the center yoke 32 to the center point C1 of the lens L3 and the line connecting the center point C2 of the center yoke 32 to the center point C1 of the lens L3 is within the range of 16° to 17°, β is set within the range of 7.8° to 8.3°. As a result, as shown in Table 1, the distance D1 and the distance D2 can be made substantially equal, and the magnetic field strength between the first magnet 33a and the second magnet 33b and the center yoke 32 can be made substantially uniform in the radial direction of the lens L3, thereby improving the driving force of the VCM 30.

[0055] In the above embodiment, the first and second side yokes 31a, 31b and the upper and lower yokes 34a, 34b are made of SPCC, and the center yoke 32 is made of SS400. However, the present invention is not limited to this. For example, the first and second side yokes 31a, 31b and the upper and lower yokes 34a, 34b may be made of SPCC, and the center yoke 32 may be made of a material having a higher saturation magnetic flux density than SPCC (e.g., Fe-35% Co-Cr alloy, Fe-20% Co-Cr-V alloy, silicon steel plate Fe-3% Si alloy, pure iron, or SS400). This can eliminate the jamming of magnetic flux generated at the end of the center yoke 32 in the optical axis direction, and improve the flow of magnetic flux in the center yoke 32, thereby improving the driving force of the VCM 30.

[0056] In the above embodiment, the cross-sectional area of ​​the center yoke 32 in a plane perpendicular to the optical axis direction is constant along the optical axis OA, but this is not limited to the above. For example, the cross-sectional area of ​​both ends of the center yoke 32 in the optical axis direction may be larger than the cross-sectional area of ​​the center portion. This can eliminate congestion of magnetic flux generated at the ends of the center yoke 32 in the optical axis direction and improve the flow of magnetic flux within the center yoke 32, thereby improving the driving force of the VCM 30.

[0057] In the above embodiment, the second fixed barrel 20 that houses the lens holding frame F3 may be a movable barrel that is capable of moving linearly in the optical axis direction. In the above embodiment and its modified examples, the lens barrel 100 may be a fixed focal length lens or a zoom lens.

[0058] The above-described embodiment is a preferred example, but is not limited thereto, and various modifications are possible without departing from the scope of the present invention, and any combination of components may be used. [Explanation of symbols]

[0059] 1 Camera 30 Voice coil motor 31a 1st side yoke 31b 2nd side yoke 32 Centre York 33a 1st magnet 33b 2nd magnet 35 Coil 100 Lens barrel 101 Camera body L3 Lens F3 lens holder

Claims

[Claim 1] A first yoke and a second yoke each having a length in an optical axis direction; a third yoke having a length in the optical axis direction and disposed between the first yoke and the second yoke; A first magnet disposed on the first yoke; A second magnet disposed on the second yoke; a coil that is inserted through the third yoke and is movable in the optical axis direction by a magnetic force of the first magnet and the second magnet; a lens holding frame that holds a lens and is movable in the optical axis direction together with the coil; Equipped with a first plane including a first side surface farther from the third yoke among two side surfaces of the first yoke opposed to each other in the circumferential direction of the lens, and a second plane including a second side surface farther from the third yoke among two side surfaces of the second yoke opposed to each other in the circumferential direction, intersect at a position within the lens different from a center point of the lens when viewed from the optical axis direction, a difference between a first distance between an outer circumferential corner of the first magnet on the third yoke side and a center point of the third yoke and a second distance between an inner circumferential corner of the first magnet on the third yoke side and the center point of the third yoke is 0.14 mm or less, In a plane perpendicular to the optical axis, an angle between a first line connecting a center point of the third yoke and a center point of the lens and the first plane, and an angle between the first line and the second plane are within a range of 5.4° to 11°. Lens barrel.

Images