JPH0743690Y2 - Lens drive mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a lens driving mechanism, and more particularly to a lens driving mechanism for driving a lens in an optical axis direction by a driving force of a motor or the like.

[Prior Art] Generally, a helicoid-type lens feeding mechanism is often used as a lens driving mechanism, but such a lens feeding mechanism has a large loss due to a frictional force at a helicoid portion.
In addition, there is a defect that the mechanism is complicated and the size is increased.

Therefore, a mechanism has been proposed in which the lens is driven in the optical axis direction by supporting the lens on a guide shaft parallel to the optical axis and driving a cam that is in pressure contact with a cam follower provided on the lens side. See Japanese Patent Publication No. 62-38627).

[Problems to be Solved by the Invention] However, in the lens drive mechanism of this prior application, there are a point of action of a spring that biases the cam follower in the direction of the cam and a point of contacting the cam follower with the cam. Since they are different, a moment is generated during this, and the moment acts on the guide shaft. By appropriately selecting the material of the guide shaft and the fitting portion of the lens fitted to the guide shaft, the friction coefficient between the guide shaft and the fitting portion of the lens can be made as small as possible, but the moment is the lens frame. If the guide shaft is always acting, the fitting part between the lens and the guide shaft becomes unevenly worn over time,
The lens will not be driven smoothly.

In view of the above problems, an object of the present invention is to provide a lens driving mechanism capable of smoothly driving a lens by preventing a moment from acting on a guide shaft.

[Means and Actions for Solving the Problems] The lens driving mechanism of the present invention is designed to displace a lens having a cam surface which is the front end surface or the rear end surface of a movable member arranged so as to be displaced in the circumferential direction of the lens. A cam mechanism that is provided so as to project substantially parallel to the optical axis from the frame, and a cam follower is provided so that the tip end thereof contacts the cam surface, and the lens frame is moved in the optical axis direction by this cam mechanism, Further, it is arranged so as to pass an abutting position of the cam follower and the cam surface and to apply an urging force in a direction to bring the cam follower and the cam surface into contact with each other in substantially the same position and in the same direction as a straight line parallel to the optical axis. And a biasing means.

[Embodiment] FIG. 2 is an exploded perspective view showing an internal configuration of an embodiment of an autofocus (hereinafter abbreviated as AF) zoom camera to which the lens driving mechanism of the present invention is applied. In FIG. 2, a lens frame 2 of the relay lens L ₄ is integrally provided on the first fixed block 1, and guide shafts 3 and 4 are arranged on both sides of the lens frame 2. The one of the guide shaft 3 focus lens L ₁ which will be described later, the variator L _2, a main guide shaft for movably supporting the lens frame compensator L ₃ in the direction along the optical axis O, the other of the guide shaft 4 Is a sub-guide shaft for stopping rotation of each lens frame. The two guide shafts 3 and 4 extend forward along the optical axis O in parallel and slightly extend rearward. Relay lens L ₄
A diaphragm unit 5 is arranged in front of the lens unit 3, and the unit 5 extends around the lens frame 2 in a direction perpendicular to the optical axis O.
The mounting holes 5a, 5b, 5c on the aperture unit 5 are aligned with the screw holes 2d, 2e, 2f on the arm portions 2a, 2b, 2c of the book and fixed by screws (not shown). A compensator L ₃ is arranged in front of the diaphragm unit 5, and a variator L ₂ is arranged in front of it. Lens frame 6 of compensator L ₃ and variator L ₂
The lens frame 7 is supported by the guide shafts 3 and 4. The front end of one arm of the lens frames 6 and 7 is 2
The main guide shaft 3 diverges into two support portions 6a, 6b and 7a, 7b, and the compensator L ₃ and the variator L ₂ are accurately supported by the main guide shaft 3 penetrating through the holes provided in these support portions. . The supporting portions 6a, 6b of the lens frame 6 and the supporting frames 7a, 7b of the lens frame 7 are supported by the main guide shaft 3 in a state in which the supporting portions 6b, 7b, 6a, 7a are intricately arranged in this order from the rear. (See Figure 1). This is the compensator
This is so that L ₃ and the variator L ₂ can be brought close to each other during zooming. The compensator L ₃ and the variator L ₂ are prevented from rotating by the auxiliary guide shaft 4 penetrating through the holes formed in the support portions 6c and 7c at the tips of the other arm portions of the lens frames 6 and 7. Also, the one arm portion and the other arm portion of both lens frames 6 and 7 are in mutually inverted positions, and some of these arm portions are notched in the lens frames 6 and 7 in directions opposite to each other. There is. When the lens frames 6 and 7 are viewed from the front-rear direction, the space 24a close to the main guide shaft 3 due to the notched end surfaces 6d and 7d of one arm.
Is formed, and the notched end surfaces 6e and 7e of the other arm form a space 24b close to the sub guide shaft 4 (see FIG. 3). A focusing spring 28, which will be described later, is arranged in the one space portion 24a.

Also, the support portion 6b of the compensator L ₃ and the variator L ₂
Zooming cam followers 8 and 9 are attached to the supporting portion 7b of each. These two cam followers
8 and 9 are fitted in one cam groove 11 formed in the zoom cam plate 10, and a wire spring 12 having a habit of opening is hung between the two cam followers 8 and 9, respectively. Cam surfaces 11a formed on the end surfaces of the
It is in contact with 11b. The zoom cam plate 10 has a rack 10 that meshes with a zoom drive gear 13 provided at the base of the guide shaft 3.
a is formed, and the zoom cam plate 10 is guided by the zoom cam shaft 15 provided on the fixed member 14 to guide the optical axis O.
It can be moved in the direction orthogonal to. The fixing member 14 is fixed to the first fixing block 1. Further, the unit plate 17 of the zoom drive unit 16 is fixed to the first fixed block 1, and the driving force of the zoom motor 18 of the unit 16 is transmitted to the zoom drive gear 13 via the transmission gears 19 to 21. There is. Leaves 10b and 10c are provided at the tip end portion of the zoom cam plate 10, and the leaf end 10b and 10c are provided with a zoom end detection sensor 22 or 2 including a photo reflector or the like.
3 are facing each other.

The focus lens L ₁ is arranged in front of the variator L ₂ . Similarly to the lens frames 6 and 7, the lens frame 25 of the focus lens L ₁ has the tip of one arm branching into two front and rear support portions 25a and 25b, and the main guide shaft 3 is inserted in the holes of the two. The auxiliary guide shaft 4 penetrates through the hole formed in the support portion 25c at the tip of the other arm to prevent the focus lens L ₁ from rotating. Has been done.

A screw hole 25d is provided in the vicinity of the hole through which the guide shaft 3 penetrates in the support portion 25a. The screw hole 25d has a threaded outer periphery for focusing.
26 is screwed. The tip of the cam follower pin 26 projects to the back side of the support 25a. A ring-shaped focusing cam member 27 as a movable member is arranged at the outer peripheral position of the lens frame 25. The front end surface of the focusing cam member 27 is a cam surface 27a.
The tip end of the cam follower pin 26 faces 7a (see FIG. 1).

Also, on the extension of the central axis of the cam follower pin 26,
On the back of this lens frame 25, a spring hook 25e is mounted on a support portion 25b.
(See FIG. 1) is formed, and one end of the focusing spring 28 is hooked on the spring hook 25e. The other end of the focusing spring 28 is hooked on a spring hook 2g formed in the lens frame 2 of the relay lens L _4. That is, the focusing spring 28 biases the lens frame 25 of the focus lens L ₁ rearward, penetrates the space 24 a of the lens frames 6 and 7 in the vicinity of the guide shaft 3, and is parallel to the guide shaft 3. Is stretched over.

The lens frame 25 and the focusing cam member 27, which is a movable member, are arranged in the second fixed block 29. The second fixing block 29 is attached to each of the screw holes 2h to 2k formed at the tip of the arm portions 2a, 2b, 2c of the lens frame 2 by using a screw member (not shown) and integrated with the first fixing block 1. Has been done. The rear end surface of the focusing cam member 27 contacts the stepped end surface 29a of the second fixed block 29 to regulate the position of the focusing cam member 27 in the optical axis direction. In other words, the stepped end surface 29a of the second fixed block 29 regulates the position of the focusing cam member 27, so that the lens frame
The cam follower pin 26, which is urged rearward by the focusing spring 28 together with 25, is moved to the focusing cam member.
The cam surface 27a of 27 is pressed.

A gear portion 27b is formed on a part of the outer periphery of the focusing cam member 27, which is a movable member, and the gear portion 27b meshes with a drive gear 30 supported by the auxiliary guide shaft 4. This drive gear 30 is driven by a focusing drive unit 31. The drive unit 31 is configured by attaching an AF motor 32 and transmission gears 33 to 35 to a unit plate 36. The drive unit 31 is configured such that the unit plate 36 is attached to the second fixed block 29 with the screw 37 so that the drive gear 30 and the transmission gear 35 mesh with each other and the drive force from the drive unit 31 is transmitted to the focusing cam member 27. Becomes Further, a protruding piece 27c is provided on a part of the outer periphery of the focusing cam member 27, and the reference position of the focusing cam member 27 is a cam position formed by a photo interrupter attached to the second fixed block 29 by the protruding piece 27c. It is adapted to be detected by the detection sensor 38.

A front cover 39 is arranged in front of the lens frame 25 of the focus lens L ₁ , and the cover 39 is fixed to the front surface of the second fixed block 29. The front ends of the two guide shafts 3 and 4 are fixed to the front cover 39 at a predetermined interval which is the same as the distance between the rear ends of the guide shafts 3, 4 so that the two guide shafts 3 and 4 are arranged in parallel along the optical axis O. It is set up.

Outside the second fixed block 29, a light projecting section 40a and a light receiving section 40b are provided.
The AF distance measuring unit 40 of a triangular distance measuring type that is integrally provided apart from the base line length and, if necessary, the AF auxiliary light device 41 that emits auxiliary light at the time of distance measurement at night, etc., from the leaf spring. It is attached by a pressing member 42a, a screw 42b, and the like.

Further, a holder 44 for holding a CCD (charge coupled device) 43 is arranged as an imager unit behind the first fixed block 1. The CCD holder 44 holds the CCD 43 inside the holder via three leaf springs 45, 46 and 47 while biasing the CCD 43 in the front-back, left-right and up-down directions. The back plate 48 is screwed on the back of the holder 44 holding the CCD 43.
Attached by 9. By adjusting the screw 49, the inclination of the image pickup surface of the CCD 43 can be adjusted. The screw 50 on the CCD holder 44 is for adjusting the vertical position of the CCD 43 with respect to the holder 44, and the screw 51 is
This is for adjusting the left and right position of the CCD 43. The CCD holder 44 includes a guide shaft 3 protruding rearward of the first fixed block 1,
The image pickup surface of the CCD 43 can be adjusted in the optical axis direction by appropriately rotating the adjusting cam ring 52 supported by the rear end of the block 4 and interposed between the block 1 and the CCD holder 44. Has become.

In the AF zoom camera configured as described above,
A portion of the lens driving mechanism of the present invention is shown in a sectional view in FIG. As mentioned above, the focus lens L ₁ and the variator
Since L ₂ and compensator L ₃ are supported by two guide shafts 3 and _{4 which} are integrated with the relay lens L ₄ and are parallel to the optical axis O,
The positioning accuracy of each of these lenses with respect to the optical axis O is high.

Among these lenses, as for the driving of the focus lens L ₁ related to the lens driving mechanism of the present invention, the lens frame 25 is constantly urged in the optical axis direction by the focusing spring 28 stretched in parallel with the guide shaft 3, With this biasing force, the cam follower pin 26 provided on the lens frame 25 presses the cam surface 27a of the focusing cam member 27,
When the focusing cam member 27 is rotated by driving the motor 32, the cam surface 27a moves with respect to the cam follower pin 26, whereby the lens frame 25 moves along the guide shafts 3 and 4, and focusing driving is performed.

Regarding the drive of this focus lens L ₁ , its lens frame
Considering the force acting on 25, the force from the cam follower pin 26 and the force from the focusing spring 28. When the focus lens L ₁ actually moves, the frictional force between the lens frame 25 and the guide shaft 3 also largely acts,
The frictional force can be considerably reduced by appropriately selecting the material of the bush on the sliding contact surface of the lens frame 25 with respect to the guide shaft 3. Therefore, the strong force exerted on the lens frame 25 is the force on the cam follower pin 26 and the force on the focusing spring 28. The force acting on the lens frame 25 ideally acts on the guide shaft 3 coaxially, but in reality, it is impossible to provide all of these action points coaxially on the guide shaft 3. If the force acting on the lens frame 25 is divided into several parts other than the guide shaft 3, a moment is generated, and a force for tilting the lens frame 25 with respect to the guide shaft 3 is exerted. That is, even if the spring is provided coaxially with the guide shaft 3, the cam cannot be provided coaxially with the guide shaft 3, so that a moment is generated at different points of action, unlike the lens drive mechanism of the previous application. become. However, in this embodiment, as described above and as is clear from FIG. 1, the focusing spring 28
Is hung near the guide shaft 3 in parallel with the guide shaft 3,
Moreover, since the direction of the urging force of the focusing spring 28 and the pressing direction of the cam follower pin 26 against the cam surface 27a coincide with each other, in this case, these points of action are such that the lens frame 25 moves to the guide shaft 3a. As long as it moves along, it does not act as a moment on the lens frame 25 at all. That is, the lens frame 25 is not acted upon by a force to tilt it during driving, and therefore the lens frame 25 moves smoothly along the guide shaft 3. Moreover, since such a moment does not act on the lens frame 25, the lens frame 25
There is no risk of itself deforming. Furthermore, lens frame 25
The smoothness of the movement makes the optical performance such as the responsiveness and accuracy of the focusing operation more satisfactory.

In addition, the focusing spring 28 includes the lens frame 7 of the variator L _{2 and} the lens frame of the compensator L ₃ between the spring hook 25e of the lens frame 25 of the focus lens L ₁ and the spring hook 2g of the lens frame 2 of the relay lens L _4. 6 does not hinder the movement of the lens frames 6 and 7, that is, as shown in FIG.
The dead space is effectively used because it is bridged through the space portion 24a formed by the cutout end surfaces 6d and 7d. Incidentally, when the guide shaft 3 is provided with a spring, the guide shaft 3 must be lengthened by the length for fitting the spring in addition to the movable range of the lens frames 6, 7, 25. In this embodiment, the guide shaft 3 may have the minimum necessary length.

In general, the aperture of the focus lens L ₁ is the largest, and the variator L ₂ and the compensator L ₃ behind the focus lens L ₁ are formed to have a small aperture in order to allow the converged light from the focus lens L ₁ to pass therethrough. , 7 has a sufficient margin to form the space portion 24a for disposing the focusing spring 28. Further, since a relatively long spring can be used as the focusing spring 28 in this dead space, a spring having a low value can be used as the spring constant, and it is always stable with respect to the lens frame 25 regardless of its focus position. Can give power.

[Effect of the Invention] As described above, according to the present invention, since the contact position between the cam follower and the cam surface and the point of action of the urging force coincide with each other, no moment is generated between them. The lens can be driven smoothly. Further, the moment does not cause the lens frame to be deformed.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of the AF zoom camera shown in FIG. 2, and FIG. 2 is an exploded perspective view of an embodiment of the AF zoom camera to which the lens driving mechanism of the present invention is applied. FIG. 3 is a sectional view taken along the line III-III in FIG. 1. 25 …… Focus lens lens frame 26 …… Cam follower pin 27 …… Focusing cam member (movable member) 27a …… Cam surface 28 …… Focusing spring (biasing means)

Claims (1)

[Scope of utility model registration request] 1. A cam, which has a front end surface or a rear end surface of a movable member arranged to be displaced in the circumferential direction of itself as a cam surface, is projected from the lens frame substantially in parallel with the optical axis,
A cam mechanism provided with a cam follower so that its tip comes into contact with the cam surface, and the lens mechanism is moved by the cam mechanism in the optical axis direction, and the cam mechanism is moved through the contact position between the cam follower and the cam surface. Urging means arranged so as to apply an urging force in a direction in which the cam follower and the cam surface are brought into contact with each other in substantially the same position and in the same direction as the straight line parallel to the optical axis. And a lens drive mechanism.