JP2519892Y2 - Zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a zoom lens, and more specifically, in a zoom lens in which each lens is movably supported by a guide axis parallel to the optical axis, the focus lens is the optical axis. The present invention relates to a mechanism that drives in a direction along the.

[Prior Art] A mechanism has been proposed in which a 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 Utility Model Laid-Open No. 62-38627).

[Problems to be Solved by the Invention] However, in the lens driving mechanism of this prior application, a spring for pressing the cam follower against the cam is fitted into the guide shaft. The guide axis is the minimum required length of the moving range of the lens, and if a spring is inserted in addition to this, the guide axis must be lengthened by that amount, but in reality, the guide axis Since the shaft cannot be made so long, a spring having a short length and a relatively strong elastic force, that is, a spring having a high spring constant is used. When such a spring having a short length and a high spring constant is used, the force for pressing the cam follower against the cam changes depending on the position of the lens, so that the lens cannot move smoothly.

In view of such problems, an object of the present invention is to provide a zoom lens capable of smoothly driving a focus lens.

[Means and Actions for Solving the Problems] The zoom lens of the present invention is a zoom lens in which a variator, a compensator, and a focus lens having an effective aperture larger than those lenses are movably supported by a guide shaft parallel to the optical axis. A lens for moving the focus lens in a direction along the optical axis by a drive system, and a means for moving the focus lens closer to the optical axis side than the guide axis, and a lens frame of the focus lens and a lens frame of the relay lens. A space between the variator and the compensator, which is located between the variator and the compensator, is arranged so as to pass along a region extended in the optical axis direction, and the focus lens is arranged on the optical axis. And an elastic member adapted to urge in a direction along the elastic member, the elastic member for moving the focus lens parallel to the guide axis. Along with this, the portion of the dead space around the variator and compensator is expanded and contracted.

[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 zoom lens 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 part 6b of the compensator L ₃ and the variator
A cam follower 8 for zooming is provided on each supporting portion 7b of L _2.
And 9 are attached. The 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 them, so that the two cam followers 8 and 9 are The cam surfaces 11 formed on the end surfaces of the cam grooves 11 that face each other.
It is in contact with a and 11b. The zoom cam plate 10 has a rack that meshes with a zoom drive gear 13 provided at the base of the guide shaft 3.
10a is formed, and the zoom cam plate 10 can be moved in the direction orthogonal to the optical axis O by being guided by the zoom cam shaft 15 provided on the fixed member 14. 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 . The lens frame 25 of this focus lens L ₁ also
As with the lens frames 6 and 7, the front end of one arm is 2
The main guide shaft 3 is divided into two supporting portions 25a and 25b so that the main guide shaft 3 penetrates through these holes and can be moved in the optical axis direction with high precision. The focus lens L ₁ is prevented from rotating by the auxiliary guide shaft 4 passing through the hole.

A screw hole 25d is provided in the vicinity of the hole passing through the guide shaft 3 of the support portion 25a, and a focusing cam follower pin 26 having a thread on the outer periphery is screwed into the screw hole 25d. There is. The tip of the cam follower pin 26 projects to the back side of the support 25a. A ring-shaped focusing cam member 27 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, and the tip end portion of the cam follower pin 26 faces the cam surface 27a (see FIG. 1).

In addition, on the extension of the central axis of the cam follower pin 26, the back of the lens frame 25 is spring-loaded on the support portion 25b.
5e (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, and penetrates the space 24a of the lens frames 6 and 7 near the optical axis O of the guide shaft 3. Guide shaft 3
It is stretched in parallel with. Since the focus lens L ₁ has a larger diameter than the variator L ₂ , the compensator L ₃ , and the relay lens L ₄ , the lens frames 7, 6, 2 are larger than the lens frame 25 toward the optical axis O. Therefore, the space portion 24a formed in the lens frames 6 and 7 is a sufficient space for inserting and placing the focusing spring 28.

The lens frame 25 and the focusing cam member 27 are arranged in the second fixed block 29. The second fixed block 29 is
The first fixing block 1 is integrated with the screw holes 2h to 2k formed at the tips of the arm portions 2a, 2b, 2c of the lens frame 2 by using screw members (not shown). The rear end surface of the focusing cam member 27 is a step end surface of the second fixed block 29.
The position of the focusing cam member 27 with respect to the optical axis direction is regulated by making contact with the 29a. That is, the step end surface 29a of the second fixed block 29 regulates the position of the focusing cam member 27, so that the cam follower pin 26, which is biased rearward by the focusing spring 28 together with the lens frame 25, is moved to the cam of the focusing cam member 27. The surface 27a is pressed.

The gear part 17 is provided on a part of the outer periphery of the focusing cam member 27.
The gear portion 27b formed with b meshes with the 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. In this drive unit 31, the unit plate 36 is fixed to the second fixing block 29 with screws 37.
The drive gear 30 and the transmission gear 35 mesh with each other by being attached to the drive gear 31, and the drive force from the drive unit 31 is transmitted to the focusing cam member 27. 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.

The front cover 39 is 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.

On the outside of the second fixed block 29, the light projecting section 40a and the light receiving section 4 are provided.
Triangular AF with 0b separated by the base line length
A distance measuring unit 40 and, if necessary, an AF auxiliary light device 41 that emits auxiliary light at the time of distance measurement such as at night are attached by a pressing member 42a made of a leaf spring and a screw 42b.

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, the zoom lens portion 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.

Regarding driving of the focus lens L ₁ related to the zoom lens of the present invention among these lenses, 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. The cam follower pin 26 provided on the lens frame 25 is pressed against the cam surface 27a of the focusing cam member 27 by the urging force.
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 , considering the force acting on the lens frame 25, the force is 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, but the material of the bush is appropriately selected on the sliding contact surface of the lens frame 25 with respect to the guide shaft 3. By selecting, the frictional force can be considerably reduced. 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. Lens frame 25
Although it is ideal that the force acting on the guide shaft 3 acts coaxially on the guide shaft 3, in reality, it is impossible to provide all of these working 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 the lens frame 25 moves against the guide shaft 3.
The power to tilt 25 will work. That is, even if a spring is provided coaxially with the guide shaft 3 as in the zoom lens of the above-mentioned prior application, the cam cannot be provided coaxially with the guide shaft 3, so that a point of action is different and a moment is generated. Become. However, in this embodiment, as described above,
Further, as is apparent from FIG. 1, the focusing spring 28 is hung near the guide shaft 3 in parallel with the guide shaft 3, and moreover, the direction of the urging force by the focusing spring 28 and the cam of the cam follower pin 26. Since the pressing direction against the surface 27a coincides, in this case, these action points do not act on the lens frame 25 at all as long as the lens frame 25 moves along the guide axis 3. 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.

Further, the focusing spring 28 has a focus lens L ₁
The lens frames 6 and 7 are moved to the lens frame 7 of the variator L ₂ and the lens frame 6 of the compensator L ₃ between the spring frame 25e of the lens frame 25 of 2 and the spring frame 2g of the lens frame 2 of the relay lens L _4. Without interfering with the above, that is, as shown in FIG. 3, the dead space is effectively utilized because it is bridged through the space portion 24a formed by the cutout end faces 6d and 7d. Incidentally, when the guide shaft 3 is provided with a spring as in the zoom lens of the above-mentioned prior application, the lens frames 6, 7,
In addition to the movable length range of 25, the guide shaft 3 must be lengthened by the length for fitting the spring, but in the present embodiment, the guide shaft 3 may have the minimum necessary length.

As described above, as is the case with this embodiment as well, in general, the aperture of the focus lens L ₁ is the largest, and the lenses variator L ₂ and compensator L ₃ behind the focus lens L ₁ pass the converged light by the focus lens L _1. Since the aperture is formed small, the lens frames 6 and 7 have a sufficient margin to form the space 24a for disposing the focusing spring 28. Therefore, by disposing the focusing spring 28 in this dead space, it is not necessary to secure an occupied space for the focusing spring 28 in particular, and the lens barrel is compact. Moreover, in the dead space, since the focusing spring 28 can use a relatively long spring, a spring having a weak elastic force, that is, a spring having a small value as a spring constant can be used. A stable force can always be applied regardless of the focus position, and the focus lens L ₁ can be moved smoothly.

[Advantages of the Invention] As described above, according to the present invention, since the elastic member can be disposed in the empty space without providing it on the guide shaft or the like, the structure can be downsized, and the elastic member can be long and spring-like. Since a lens having a small constant can be used, the biasing force does not change regardless of the position of the focus lens, and the lens can be driven smoothly.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of the AF zoom camera shown in FIG. 2, FIG. 2 is an exploded perspective view of an embodiment of the AF zoom camera to which the zoom lens of the present invention is applied, and FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 1. 3,4 ...... Guide shaft 24a ...... Space (outer peripheral position of variator and compensator) 25 ...... Lens frame of focus lens 26 ...... Cam follower pin (means for moving focus lens) 27 ...... Focusing cam member (focus lens) 28 …… Focusing spring (elastic member) 31 …… Focusing drive unit (drive system) L ₁ …… Focus lens L ₂ …… Variator L ₃ …… Compensator

Claims (1)

(57) [Scope of utility model registration request] 1. A zoom lens comprising a variator, a compensator, and a focus lens having an effective aperture larger than those lenses, which is movably supported by a guide shaft parallel to the optical axis. A means for moving in the direction along the axis and a position closer to the optical axis side than the guide axis and between the lens frame of the focus lens and the lens frame of the relay lens, and the outer circumference of the variator and compensator. An elastic member arranged so as to pass along a region extending in the optical axis direction of the space portion generated at the side position, and biasing the focus lens in the direction along the optical axis. A zoom lens comprising: