JP3995444B2 - Lens drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lens driving device that moves a lens in an optical axis direction, and more particularly to a lens driving device that includes a driving source such as a step motor as a driving mechanism.
[0002]
[Prior art]
As shown in FIGS. 7 and 8, the conventional lens driving device is arranged in and out of a fixed cylinder 2 fixed to a base 1 holding a filter 1 a and a CCD 1 b as an image pickup device, and inside the fixed cylinder 2. The first lens frame 4, the second lens frame 5, the third lens frame 6, and the cylindrical cam 3 that are sequentially arranged in the optical axis direction L inside the cylindrical cam 3 and the cylindrical cam 3 and hold the lens G respectively are driven. A drive mechanism 7 and a drive mechanism 8 that drives the third lens frame 6 are known.
[0003]
As shown in FIGS. 7 and 8, the drive mechanism 8 includes a nut 8a held by the third lens frame 6, a lead screw 8b extending in the optical axis direction L and screwed into the nut 8a, and a lead screw 8b. A step motor 8c as a drive source that is directly connected to generate rotational driving force, a guide shaft 8d that guides the third lens frame 6 in the optical axis direction L, and a detent that restricts rotation of the third lens frame 6 around the optical axis. A shaft 8e and the like are provided.
When the lead screw 8b is rotated by the step motor 8c, the third lens frame 6 is moved in the optical axis direction L together with the nut 8a.
[0004]
[Problems to be solved by the invention]
By the way, in the above lens driving device, since the step motor 8c for driving the third lens frame 6 is arranged inside the cylindrical cam 3, a sufficient space is secured to accommodate the step motor 8c. It is necessary to increase the inner diameter D of the cylindrical cam 3.
Further, since the step motor 8c is arranged inside the cylindrical cam 3, there is a limit to retract the second lens frame 5 and the first lens frame 4 in the retracted state, and the apparatus in the optical axis direction L is correspondingly reduced. Thickness is required.
[0005]
As a result, even in a camera equipped with this lens driving device, the lens barrel (cylindrical cam 3 and first lens frame 4) protruding and retracting from the main body becomes large, and the thickness of the main body in the optical axis direction is also required. It is difficult to reduce the size and thickness.
Further, since the exterior of the step motor 8c is generally formed of a metal material, when it is arranged inside the cylindrical cam 3, it is necessary to take measures against flare caused by reflection on the surface of the step motor 8c, which increases the cost. Invite.
[0006]
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a lens driving device that can achieve cost reduction, size reduction, thickness reduction, and the like while ensuring a desired function. Is to provide.
[0007]
[Means for Solving the Problems]
The lens driving device of the present invention includes a base, a fixed cylinder that is fixed to the base and has an axial center in the optical axis direction, and is disposed inside the fixed cylinder so as to be movable in and out in the optical axis direction with respect to the fixed cylinder and has a cam action. A cylindrical cam having one or more front lens frames that are held in front of the optical axis direction inside the cylindrical cam and are reciprocated by the cylindrical cam, and in the optical axis direction behind the front lens frame. A rear lens frame that is reciprocally arranged to hold the lens, and is driven by a drive source, a lead screw that is rotated by the drive source, and a lead screw to be driven, and is held by the rear lens frame. nuts, guide shafts for guiding the rear lens frame in the optical axis direction, and a drive mechanism for the rear lens frame includes a detent shaft for restricting the rotation of the optical axis, the driving source is outside of the fixed barrel Oite, is fixed on the base with its driving shaft to direct the base side, the lead screw is in the optical axis direction, one end portion is arranged outside the fixed barrel so as buried in the base, The guide shaft is disposed in the vicinity of the lead screw on the outside of the fixed cylinder, and the rear lens frame is connected to the guide shaft while penetrating the lead screw and holding a nut in an arm portion extending to the outside of the fixed cylinder. It is characterized by that.
According to this configuration, a driving source for driving the rear lens frame, the lead screw, and since the guide shaft is disposed outside of the cylindrical cam and the fixed barrel, be formed smaller outer diameter of the cylindrical cam and the fixed barrel In the retracted state, the front lens frame can be retracted to a position closer to the rear lens frame, and the drive source is fixed on the base so that the drive shaft faces the base side. Since the screw is disposed so that one end thereof is buried in the base in the optical axis direction, the apparatus can be thinned in the optical axis direction.
Therefore, when this apparatus is mounted on a camera or the like, the lens barrel (cylindrical cam and lens frame) protruding and retracting from the camera body can be reduced in diameter and size, and the camera body can be reduced in thickness. In addition, flare countermeasures are not required, and the cost of the apparatus can be reduced.
Further, the guide shaft is disposed in the vicinity of the lead screw, and the rear lens frame is connected to the guide shaft while penetrating the lead screw and holding a nut in an arm portion extending from a part thereof to the outside of the fixed cylinder. Therefore, the driving force by the lead screw is efficiently transmitted to the lens frame, and the lens frame can be moved smoothly.
[0009]
In the above configuration, the front lens frame has a first lens frame and a second lens frame sequentially arranged from the subject side, the first lens frame and the second lens frame perform zooming operation, and the rear lens frame is A configuration that performs a focusing operation can be adopted.
According to this configuration, in the lens driving device capable of zooming photographing that includes the three lens groups independently including the first lens frame, the second lens frame, and the third lens frame, it is possible to reduce the size, the thickness, and the cost. Can be made.
[0011]
In the above configuration, the lead screw can be directly connected to the drive source outside the fixed cylinder, and the rotation stopper shaft can be arranged inside the fixed cylinder.
According to this configuration, when the lead screw is rotated by the directly connected driving source and the lens frame is guided in the optical axis direction by the guide shaft, the driving force by the lead screw is efficiently transmitted to the lens frame. Can be moved smoothly.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
1 to 3 show an embodiment of a lens driving device according to the present invention. FIG. 1 is a front view in which some components are omitted, and FIGS. 2 and 3 are developed sectional views.
As shown in FIG. 1, the lens driving device has a substantially rectangular outline, a low-pass filter 11, a base 10 to which a CCD 12 or the like as an image sensor is attached, and an axis centered in the optical axis direction L that is fixed to the base 10. A cylindrical fixed cylinder 20, a cylindrical cam 30 that is supported so as to be rotatable and linearly movable inside the fixed cylinder 20 and has a cam action, and a first lens that is supported so as to be movable in the optical axis direction L inside the cylindrical cam 30. The group 40, the second lens group 50, the third lens group 60 supported so as to be movable in the optical axis direction L with respect to the base 10, the driving mechanism 70 that transmits the driving force to the cylindrical cam 30, and the third lens group 60. A drive mechanism 80 for transmitting force is provided.
[0014]
As shown in FIGS. 2 and 3, the cylindrical cam 30 is formed on the inner peripheral surface of the follower pin 31 and the arcuate gear portion 32 formed on the outer peripheral surface, and is camped on the first lens group 40 and the second lens group 50. A cam cylinder 33 and the like that guide the operation in the optical axis direction L while restricting the rotation of the cam grooves 33 and 34, the first lens group 40, and the second lens group 50 are provided.
The follower pin 31 is inserted into the cam groove 21 of the fixed cylinder 20, and the cylindrical cam 30 is moved forward and backward in the optical axis direction L by being rotated by the drive mechanism 70.
[0015]
2 and 3, the first lens group 40 includes a first lens frame 41 as a front lens frame that holds the lens G, and a follower pin that is formed in the first lens frame 41 and inserted into the cam groove 33. 42 etc. are provided. When the cylindrical cam 30 rotates, the first lens group 40 moves forward and backward in the optical axis direction L.
[0016]
2 and 3, the second lens group 50 includes a second lens frame 51 as a front lens frame that holds the lens G, and a follower pin formed in the second lens frame 51 and inserted into the cam groove 34. 52, a shutter unit S fixed to the second lens frame 51, and the like. The shutter unit S includes an electromagnetic drive source S1 that drives the shutter blades or the diaphragm blades. Then, when the cylindrical cam 30 rotates, the second lens group 50 moves forward and backward in the optical axis direction L.
[0017]
As shown in FIGS. 1 to 3, the third lens group 60 includes a third lens frame 61 as a rear lens frame that holds the lens G. The third lens frame 61 extends to the outside of the fixed cylinder 20 from the lens frame portion 62 that holds the lens G inside the cylindrical cam 30, the connecting portion 63 formed in the vicinity of the lens frame portion 62, and the lens frame portion 62. The arm portion 64, a nut holding portion 65 formed at the tip of the arm portion 64, a connecting portion 66 formed integrally in the vicinity of the nut holding portion 65, and the like.
[0018]
Connecting portion 63, as shown in FIGS. 1 to 3, the long hole 63a for receiving the cormorants by slides closely in the circumferential direction of the lens G causes loosely inserted the detent shaft 81 in the radial direction of the lens G Have. The third lens frame 61 is regulated so as not to rotate in the plane perpendicular to the optical axis direction L (around the optical axis) by inserting the anti-rotation shaft 81 into the long hole 63a.
[0019]
The arm portion 64 extends rearward in the optical axis direction L from the lens frame portion 62, and passes through the notch portion 36 of the cylindrical cam 30 and the notch portion 22 of the fixed barrel 20 along the base 10 from the rear end portion thereof, and is fixed. The tube 20 extends to the outside in the radial direction. Further, since the arm portion 64 is long and extends from the inside of the cylindrical cam 30 to the outside of the fixed cylinder 20, a reinforcing rib 64a is formed on the upper surface or the lower surface of the arm portion 64 in order to prevent its bending. Has been. Thereby, even if the arm part 64 becomes comparatively long, the 3rd lens frame 61 is moved to the optical axis direction L with high precision.
[0020]
As shown in FIGS. 1 and 3, the nut holding portion 65 includes a clamping space 65 a that clamps the nut 67 with a slight gap and restricts its rotation, and a through hole 65 b that penetrates in the optical axis direction L. As shown in FIG. 1, the holding space 65 a is formed with a recess 65 a ′ into which the protrusion 67 a of the nut 67 is fitted, and restricts the nut 67 from rotating in a plane perpendicular to the optical axis direction L. Yes.
[0021]
As shown in FIGS. 1 and 3, the connecting portion 66 is integrally formed in the vicinity of the nut holding portion 65 and has two connecting pieces 66 a and 66 b formed at positions separated in the optical axis direction L. The connecting pieces 66a and 66b are formed with through holes 66a 'and 66b' into which guide shafts 82 extending in the optical axis direction L are slidably inserted.
[0022]
As shown in FIG. 3, the coil spring 83 is disposed between the rear surface of the connecting piece 63a and the base 10 in a compressed state. The coil spring 83 urges the connecting portion 66, that is, the third lens frame 61 toward the front (subject side) in the optical axis direction L. This urging force is set so as to urge the third lens frame 61 forward even when the third lens frame 61 is moved forward most forward (subject side).
[0023]
As shown in FIG. 3, a step motor 84 as a drive source is fixed to the fixed plate 13 that protrudes from the base 10 and extends outside the fixed cylinder 20, and the drive shaft 84a extends in the optical axis direction. The lead screw 85 is directly connected. The lead screw 85 is screwed into the nut 67.
[0024]
A drive mechanism 80 for driving the third lens frame 61 (third lens group 60) in the optical axis direction L by the step motor 84, the lead screw 85, the guide shaft 82, the rotation preventing shaft 81 , and the nut 67 as the drive source. It is configured.
[0025]
Here, since the step motor 84 having a relatively large contour is disposed outside the fixed cylinder 20, the outer diameters of the cylindrical cam 30 and the fixed cylinder 20 can be set small. The diameter dimensions of the lens frame (lens barrel) 41, the second lens frame 51, and the third lens frame 61 (lens frame portion 62) can be reduced. Therefore, a lens barrel having a small outer diameter as a whole can be formed. .
[0026]
In addition, since the step motor 84 is disposed outside the fixed cylinder 20, the second lens group 50 and the first lens group 40 can be further retracted and stopped toward the third lens group 60 in the retracted state. The apparatus can be thinned in the optical axis direction L. Furthermore, since the step motor 84, which is generally formed of a metal exterior, is disposed outside the cylindrical cam 30, measures for flare caused by reflection on the surface thereof become unnecessary, and the cost is reduced accordingly. be able to.
[0027]
Further, since the connecting portion 66 is formed in the vicinity of the nut holding portion 65 and the guide shaft 82 is disposed in the vicinity of the lead screw 85, the engagement between the lead screw 85 and the nut 67 is performed uniformly without deviation. The driving force by the lead screw 85 is efficiently transmitted to the third lens frame 61. Therefore, the third lens frame 61 is smoothly moved in the optical axis direction L.
[0028]
As shown in FIG. 2, the drive mechanism 70 includes a DC motor 71 fixed to the base 10, a worm 72 fixed to the drive shaft 71 a, a worm wheel 73 that is supported by the base 10 and meshes with the worm 72, and a worm wheel 73. The worm 74 is integrally formed coaxially with the worm wheel 75, is supported by the base 10 and meshes with the worm 74, the gear 76 is integrally formed coaxially with the worm wheel 75, and is supported by the base 10 and is gear 76. And a gear 77 that meshes with the arcuate gear portion 32. Since the DC motor 71 is also arranged outside the fixed cylinder 20, it contributes to the miniaturization of the fixed cylinder 20 and the cylindrical cam 30 as described above.
[0029]
In the drive mechanism 70, when the DC motor 71 rotates, the cylindrical cam 30 rotates through the worm 72, the worm wheel 73, the worm 74, the worm wheel 75, the gear 76, and the gear 77, and the first lens group 40 and The second lens group 50 moves forward or backward in the optical axis direction L, respectively. That is, the first lens group 40 and the second lens 50 perform a zooming operation so that a wide range of shooting from wide-angle shooting to telephoto shooting can be performed.
[0030]
In the drive mechanism 80, when the step motor 84 rotates, the third lens group 60 moves forward or backward in the optical axis direction L via the lead screw 85 and the nut 67. That is, the third lens group 60 performs a focusing operation on the imaging surface of the CCD 12 in accordance with the zooming operation of the first lens group 40 and the second lens group 50.
[0031]
Next, a general operation when the lens driving device 90 is mounted on a digital camera will be described. First, in a retracted state where no photographing is performed, the first lens group 40 and the second lens group 50 are retracted toward the rear in the optical axis direction L and are in the retracted state.
[0032]
From this retracted state, the cylindrical cam 30 is rotated straight by the drive mechanism toward the front in the optical axis direction L, and the follower pins 42 and 52 are guided to the cam grooves 33 and 34 by the rotation of the cylindrical cam 30, respectively. Thus, the first lens group 40 moves forward and the second lens group 50 moves rearward, for example, to the wide-angle shooting position. On the other hand, the third lens group 60 is moved to the in-focus position according to the positions of the first lens group 40 and the second lens group 50 by the drive mechanism 80 (step motor 84 or the like).
[0033]
From this wide-angle shooting position, when the cylindrical cam 30 is further rotated in the same direction by the drive mechanism and goes straight forward, the follower pin 52 is guided by the cam groove 34 and the second lens group 50 moves forward. To the telephoto position. On the other hand, the third lens group 60 is moved to the in-focus position according to the positions of the first lens group 40 and the second lens group 50 by the drive mechanism 80 (step motor 84 or the like).
[0034]
In the telephoto shooting position, as shown in FIG. 4, the first lens frame (lens barrel) 41 and the cylindrical cam 30 protrude from the camera body 100, but the first lens frame 41 and the cylindrical cam 30 Since the outer diameter is formed to be small, the lens barrel (cylindrical cam 30 and first lens frame 41) that appears and disappears from the camera body 100 can be reduced in size and size. Further, since the lens driving device 90 is formed to be thin, the camera body 100 on which this device is mounted can also be thinned.
That is, as shown in FIG. 4, the camera body 100 on which the lens driving device 90 according to the present invention is mounted has a lens barrel portion that has a smaller diameter and a smaller size than the conventional camera body 100 ′ indicated by a two-dot chain line. The thickness is reduced in the optical axis direction.
[0035]
5 and 6 are a front view and a longitudinal sectional view showing another embodiment of the lens driving device according to the present invention. In addition, about the structure same as the above-mentioned embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
In this apparatus, as shown in FIGS. 5 and 6, the third lens frame 61 ′ is integrally formed with the lens frame 62, the connecting portion 63 provided integrally with the lens frame 62, and the lens frame 62. In addition, a nut holding portion 65 ′ and a connecting portion 66 ′ provided adjacent to each other are formed. That is, the lead screw 85 ′, the guide shaft 82, and the rotation preventing shaft 81 are disposed inside the fixed cylinder 20 and the cylindrical cam 30.
[0036]
The drive mechanism 80 ′ is supported by the step motor 84 fixed to the base 10 outside the fixed cylinder 20, the gear 110 fixed to the drive shaft 84 a, the gear 120 fixed to the lead screw 85 ′, and the base 10. It is arranged between the gear 110 and the gear 120 and is constituted by a gear train including two-stage gears 130, 140, 150.
[0037]
In this apparatus, the arm portion 64 as in the above-described embodiment is not provided, and the nut holding portion 65 ′ and the connecting portion 66 ′ are formed directly on the lens frame portion 62, and the driving force of the step motor 84 is changed to the gear train. Therefore, the first lens frame 61 'can be reduced in size.
In addition, since the lead screw 85 ′, the guide shaft 82, and the rotation prevention shaft 81 are integrated (integrated) with respect to the lens frame portion 62, the first lens frame 61 ′ does not tilt and the optical axis direction L Therefore, the driving force is efficiently transmitted and the movement can be performed more smoothly.
[0038]
In the above embodiment, in the lens driving device including the plurality of lens groups 40, 50, 60, the structure according to the present invention is adopted for the third lens group 60. However, the present invention is not limited to this. Even if the structure according to the present invention is employed in a lens driving device including only one lens group or two lens groups, the same size reduction and thickness reduction can be achieved.
[0039]
In the above embodiment, the case where the lead screws 85 and 85 ′ are used as the driving mechanism 80 for driving the third lens group 60 is shown, but the present invention is not limited to this, and the driving force is generated by the driving source. The structure according to the present invention may be adopted in a configuration using another driving mechanism as long as the third lens frame 61, 61 ′ is driven by being transmitted.
[0040]
【The invention's effect】
As described above, according to the lens driving device of the present invention, the drive source for driving the lens frame that is reciprocally movable in the optical axis direction inside the fixed cylinder fixed to the base is provided outside the fixed cylinder. In this case, the fixed cylinder can be made smaller by that amount, so that the apparatus can be made smaller and thinner. Further, it is possible to reduce the size and thickness of a camera or the like equipped with this apparatus.
Furthermore, it is not necessary to take measures against flare caused by the surface reflection of the drive source, and the cost of the apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of a lens driving device according to the present invention.
2 is a longitudinal sectional view showing a driving mechanism for driving a cylindrical cam of the lens driving device shown in FIG. 1. FIG.
3 is a longitudinal sectional view showing a driving mechanism for driving a third lens frame of the lens driving device shown in FIG. 1. FIG.
4 is an external perspective view showing a case where the lens driving device shown in FIG. 1 is mounted on a digital camera. FIG.
FIG. 5 is a front view showing another embodiment of the lens driving device according to the present invention.
6 is a longitudinal sectional view showing a driving mechanism for driving a third lens frame of the lens driving device shown in FIG.
FIG. 7 is a front view showing a conventional lens driving device.
FIG. 8 is a longitudinal sectional view showing a conventional lens driving device.
[Explanation of symbols]
10 Base 11 Filter 12 CCD
13 Fixed plate 20 Fixed cylinder 30 Cylindrical cam 40 First lens group 41 First lens frame (front lens frame)
50 Second lens group 51 Second lens frame (front lens frame)
60 Third lens group 61, 61 'Third lens frame (rear lens frame)
62 Lens frame part 63 Connection part 64 Arm part 65, 65 'Nut holding part 66, 66' Connection part 67 Nut 70 Drive mechanism 71 DC motor 72, 74 Worm 73, 75 Worm wheel 76, 77 Gear 80, 80 'Drive mechanism 81 Non-rotating shaft (drive mechanism)
82 Guide shaft (drive mechanism)
83 Coil spring 84 Step motor (drive source, drive mechanism)
85,85 'lead screw (drive mechanism)
90 Lens drive device 100 Camera body 110, 120 Gear (gear train)
130,140,150 Two-stage gear (gear train)
G Lens L Optical axis direction

Claims (3)

A base, a fixed cylinder fixed to the base and having an axis in the optical axis direction, a cylindrical cam disposed inside the fixed cylinder so as to be able to project and retract in the optical axis direction with respect to the fixed cylinder, and having a cam action; One or more front lens frames that hold a lens and are disposed in front of the optical axis inside the cylindrical cam and are reciprocated by the cylindrical cam; and reciprocating in the optical axis direction behind the front lens frame A rear lens frame that is freely arranged and holds the lens, a drive source for driving the rear lens frame, a lead screw that is rotated by the drive source, and screwed into the lead screw and held by the rear lens frame A drive mechanism including a nut, a guide shaft that guides the rear lens frame in the optical axis direction, and a detent shaft that restricts the rear lens frame from rotating about the optical axis ;
The drive source is fixed on the base so that the drive shaft faces the base side outside the fixed cylinder,
The lead screw is arranged outside the fixed cylinder so that one end of the lead screw is buried in the base in the optical axis direction ,
The guide shaft is disposed in the vicinity of the lead screw outside the fixed cylinder,
The rear lens frame is connected to the guide shaft while penetrating the lead screw and holding the nut in an arm portion extending to the outside of the fixed cylinder.
A lens driving device. The front lens frame has a first lens frame and a second lens frame sequentially arranged from the subject side,
The first lens frame and the second lens frame perform a zooming operation,
The rear lens frame performs a focusing operation.
The lens driving device according to claim 1. The lead screw is directly connected to the drive source outside the fixed cylinder ,
The detent shaft is disposed inside the fixed cylinder,
The lens driving device according to claim 1 or 2, wherein

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