JPH08122612A - Structure of cam of lens moving mechanism - Google Patents

Abstract

PURPOSE: To provide a structure of the cam of a lens moving mechanism where the load of the turning of a cam part is not changed even when a lens frame is moved and the load on a motor is not increased by holding the engaging projection of a lens frame with opposed cam surfaces. CONSTITUTION: The engaging projection 34d is formed in a front lens frame 34 holding a front zoom lens 24 so as to freely slide inside a finder barrel 32. The cam part 50 is fitted on a cam shaft 48 turned by a motor for zooming, and a presser cam 52 is provided to freely slide and to be opposed to the cam surface 50a. The presser cam 52 presses the cam part 50 by a coil spring 54. The engaging projection 34d is held by the cam surfaces 50a and 52a. When the motor for zooming is turned, the front lens frame 34 is guided and moved by the cam surface 50a. At such a time, the pressing force by the coil spring 54 is constant regardless of the position of the front lens frame 34, so that the load of the turning of the cam shaft 48 is kept nearly constant, and the burden on the motor for zooming is not increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens moving mechanism for moving a lens of a camera in its optical axis direction.
Particularly, it relates to a structure of a cam for moving the lens.

[0002]

2. Description of the Related Art In recent years, a camera which employs a variable focus lens device and which can change the focal length appropriately so as to take a picture by a camera has become popular. In a camera equipped with this device, the focal length is changed by moving the zoom lens of the photographing optical system and the viewfinder optical system in the optical axis direction, and a lens moving mechanism is provided for moving the zoom lens. There is.

As shown in FIG. 3, for example, in a finder optical system 1, a front zoom lens 4 and a rear zoom lens 6 are arranged behind an objective lens 2, and the rear zoom lens 6 is provided.
A fixed lens, an eyepiece lens, and the like, which are not shown, are arranged in the rear of the above. The front zoom lens 4 is held by a front lens frame 8, and the front lens frame 8 is slidably attached to a guide rod 10 extending in a direction substantially parallel to the optical axis S ₀ . The rear zoom lens 6 is held by a rear lens frame 11, and the rear lens frame 11 is the guide rod.
It is slidably attached to 10. The front lens frame 8 and the rear lens frame 11 are return springs formed by coil springs.
They are connected by 12, and the lens frames 8 and 11 are urged toward each other.

Further, the cam shaft is arranged substantially parallel to the guide rod 10.
A cam portion 13 is provided, and a cam portion 14 having a substantially cylindrical shape and cam surfaces 14a formed on both end surfaces is fitted to the cam shaft 13. Engagement protrusions 8a and 11a are formed on a part of the lens frames 8 and 11, and the engagement protrusions 8a and 11a are in contact with the cam surface 14a of the cam portion 14. That is, the return spring 1
By the tension of 2, the engaging protrusions 8a and 11a of the lens frames 8 and 11
Holds the cam portion 14 from the front and back.

When a photographer operates a zoom switch, a zoom motor (not shown) is driven, and the rotation shaft of the zoom motor is rotated by a gear 16 fitted to one end of the cam shaft 13. When transmitted, the cam shaft 13 and the cam portion 14 are rotated. As a result, the positions of the lens frames 8 and 11 that engage with the cam portion 14 are changed. In addition, the lens frame 8,
By changing the position of 11, the focal length is changed while maintaining the predetermined optical relationship between the zoom lenses 4 and 6.
The shape of the cam surface 14a of the cam portion 14 is set.

On the other hand, by driving the zoom motor,
A lens moving mechanism (not shown) of the photographing optical system is activated.
Therefore, the change of the focal length of the photographing optical system and the change of the focal length of the finder optical system are performed in conjunction with each other.

[0007]

However, in the above-mentioned lens moving mechanism, the lens frames 8 and 11 are returned to each other by the return spring.
Since they are connected by 12, the tension of the return spring 12 becomes particularly large when the lens frames 8 and 11 are separated from each other. When this tension increases, a large load is applied to the rotation of the cam shaft 13 when the cam portion 14 rotates, and a load may be imposed on the zoom motor that rotates the cam shaft 13.
In particular, since the front lens frame 8 has a large moving range, and it is difficult to increase the diameter of the cam portion 14 in order to reduce the size and weight of the camera, it is necessary to increase the rising angle of the cam surface 14a. To smoothly rotate the cam portion 14, a zoom motor having a large output must be used.

Further, since it is desirable that the load for rotating the cam shaft 13 is substantially constant regardless of the focal length, the engaging protrusions 8a, 11a of the lens frames 8, 11 are pressed against the cam surface 14a. It is desirable that the pressing force of the urging spring is almost constant.

Therefore, an object of the present invention is to provide a cam structure of a lens moving mechanism in which the load for rotating the cam shaft does not increase particularly regardless of the position of the lens.

[0010]

In order to achieve the above-mentioned object, the structure of the cam of the lens moving mechanism according to the present invention is as follows.
A lens moving mechanism that holds a lens in an optical system in a lens frame, an engaging portion of the lens frame is engaged with a lens moving cam, and the lens frame is moved in the optical axis direction by the operation of the lens moving cam, It is characterized in that the lens moving cam is composed of a positive cam.

Further, the width of the cam groove of the positive cam is freely changeable, and urging means for urging in a direction of reducing the width is provided, and both side walls of the cam groove serve as an engaging portion of the lens frame. It is also characterized by sandwiching.

[0012]

When the zoom lens in the optical system is provided with the lens moving mechanism, the photographer operates the zoom switch to drive the zoom motor, thereby rotating the positive moving cam of the lens moving mechanism. It Then, the engaging portion of the lens frame engaged with the positive cam is guided, the position of the lens held by the lens frame is changed, and the focal length of the optical system is changed.

When the width of the cam groove of the positive cam is freely changeable and a biasing means for biasing the width of the positive cam is provided, the lens moves when the positive cam rotates. The frame is guided and moved in the cam groove. At this time, the urging force of the urging means is maintained substantially constant, and the rotation load of the positive cam hardly changes due to the change of the focal length. Therefore, the load on the zoom motor is substantially constant, and the rotation of the positive cam is stable. further,
Since both side walls of the cam groove sandwich the engaging portion of the lens frame, backlash does not occur even when the lens frame moves in any direction.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the cam of the lens moving mechanism according to the present invention will be specifically described below with reference to the illustrated embodiments. In this embodiment, the case where the lens moving mechanism is used for the zoom lens of the viewfinder of the camera having the variable focus lens device is described.

As shown in FIG. 2, the finder optical system 20
Is composed of an objective lens 22 facing the subject, a front zoom lens 24 and a rear zoom lens 26 for changing the focal length, an appropriate fixed lens group 28, and an eyepiece lens 30, and these lenses are almost L It is arranged inside a character-shaped finder cylinder 32.

The objective lens 22 is fixed to the tip of the finder barrel 32. The front zoom lens 24 is held by the mount portion 34a of the front lens frame 34 behind the objective lens 22, and the rear zoom lens 26 is behind the rear lens frame 34 behind it.
The lens frames 34, 36 are held by a mount portion 36a of 36, and are slidable in the direction of the optical axis S.

A field frame 38 is provided behind the rear zoom lens 26.
And a reflecting mirror 40 that bends the optical axis S is provided at a corner of the finder cylinder 32. The fixed lens group 28 is arranged beside the reflecting mirror 40, and the fixed lens group 28 is provided.
At the base end of 32, a prism 42 that bends the optical axis S at a substantially right angle
Is housed. The eyepiece lens 30 is arranged so as to face the exit surface of the prism 42. It should be noted that the finder barrel cover 44 is covered after these lenses and the like and a lens moving mechanism 58 to be described later are incorporated to shield the finder barrel 32 from light.

By the way, as shown in FIGS. 1 and 2, guide rods 46 are provided on the sides of the front zoom lens 24 and the rear zoom lens 26 substantially parallel to the direction of the optical axis S.
The guide bar 46 is supported by the side wall of the finder cylinder 32.

The lens frames 34 and 36 are mount parts.
Sliding cylinders 34b and 36b are integrally connected to the side portions of 34a and 36a, and through holes are formed in the sliding cylinders 34b and 36b. It is installed. Further, guide protrusions 34c, 36c are provided on the side portions of the mount portions 34a, 36a.
And is engaged with a guide hole 32a formed in the side wall of the finder cylinder. Therefore, the lens frames 34, 36 are slidable by being guided by the guide rod 46 and the guide hole 32a. Incidentally, the sliding cylinders 34b, 3
Engagement protrusions 34d and 36d are provided as protrusions on the 6b.

On the other hand, a cam shaft 48 that is substantially parallel to the guide rod 46 is provided adjacent to the guide rod 46.
48 is rotatably supported on the side wall of the finder cylinder 32. A substantially cylindrical cam portion 50 is fitted on the cam shaft 48, and cam surfaces 50a are formed at both ends of the cam portion 50 as side walls of a cam groove. The engagement projections 34d and 36d of the lens frames 34 and 36 are in contact with the cam surface 50a, and the engagement projections 34d and 36d are guided along the cam surface 50a. At this time, the shape of the cam surface 50a is set so that the focal length is changed while maintaining the predetermined optical relationship between the front zoom lens 24 and the rear zoom lens 26. For example,
When the amount of movement of the front zoom lens 24 is larger than the amount of movement of the rear zoom lens 26, the inclination angle of the front cam surface 50a is larger than the inclination angle of the rear cam surface 50a.

A slidable presser cam 52 is loosely inserted in the camshaft 48, and the cam portion 50 of the presser cam 52 is inserted.
A cam surface 52a having a shape that is substantially in close contact with the cam surface 50a of the cam portion 50 is formed at the end portion opposite to. A coil spring 54 is provided as a biasing means on the cam shaft 48 between the other end of the pressing cam 52 and the side wall of the finder cylinder 32, and the pressing cam 52 causes the pressing cam 52 to move the cam portion 50. It is biased to press. Therefore, the cam portion 50
Engaging projection 34 of the front lens frame 34 in contact with the cam surface 50a of the
d is the cam surface 50a of the cam portion 50 and the cam surface of the pressing cam 52.
It is sandwiched between 52a and.

A coil spring is attached to the guide bar 46 between the sliding cylinder 36b of the rear lens frame 36 and the side wall of the finder cylinder 32.
56 is provided, and the rear lens frame 36 is biased forward. Therefore, the engaging protrusion 36d of the rear lens frame 36 is
Is in contact with the cam surface 50a of the cam portion 50.

The lens moving mechanism 58 is constituted by the above-mentioned cam portion 50, the pressing cam 52, the cam shaft 48, the lens frames 34 and 36, and the like.
Is configured.

Then, one end of the cam shaft 48 is projected to the outside of the finder cylinder 32, and the gear 60 is fitted therein. The gear 60 is linked to a rotary shaft of a zoom motor (not shown) through an appropriate gear train, and the zoom motor is linked to a lens moving mechanism (not shown) of a zoom lens of a photographing optical system. Therefore, the finder optical system
The change in the focal length of 20 and the change in the focal length of the photographing optical system are configured to substantially match.

The operation of the embodiment of the cam structure of the lens moving mechanism according to the present invention constructed as described above will be described below.

When the photographer turns on the main switch of the camera, the photographer stands by in a photographable state. Then, as shown in FIG. 2, the image of the subject is transmitted through the objective lens 22, the front zoom lens 24, the rear zoom lens 26, the fixed lens group 28, the eyepiece lens 30, etc., and is captured by the photographer.

When the photographer operates the zoom switch, a zoom motor (not shown) is driven,
The rotation shaft is rotated. As a result, the gear train associated with the rotation shaft is operated, and the gear 60 emerging from the finder cylinder 32 is rotated.

As shown in FIG. 1, when the gear 60 is rotated, the cam shaft 48 and the cam portion 50 are rotated, and the engaging protrusions 34d are brought into contact with the cam surface 50a of the cam portion 50. , 36d is the cam surface 5
It is guided by 0a and moved in the direction of the optical axis S. Then, the front zoom lens 24 and the rear zoom lens 26 held by the lens frames 34 and 36 are moved while maintaining a predetermined optical relationship, and the focal length of the finder optical system 20 is changed.

The rotation of the zoom motor is also transmitted to a lens moving mechanism of a zoom lens of a photographing optical system (not shown), and the zoom lens is moved to change the focal length. That is, the finder optical system 20 described above
The change of the focal length of and the change of the focal length of the shooting optical system
It is almost the same.

Therefore, in this embodiment, since the front lens frame 34 is moved while the engaging projection 34d of the front lens frame 34 is held between the cam portion 50 and the pressing cam 52, the front lens frame 34 is moved.
Regardless of the position of 34, the pressing force of the coil spring 54 that presses the pressing cam 52 against the cam portion 50 is maintained substantially constant. Therefore, the load of turning the cam portion 50 and the cam shaft 48 does not increase, the load on the zoom motor is substantially constant, and the zoom lenses 24 and 26 can be moved with a stable output. As a result, the rotation of the cam shaft 48 and the cam portion 50 is stabilized, the movements of the zoom lenses 24 and 26 are smooth, and the focal length is reliably changed. Further, since it is not necessary to use a zoom motor having a large output, it is possible to reduce the size and weight of the camera body and reduce the material cost.

On the other hand, the coil spring 56 is urged by the sliding cylinder 36b of the rear lens frame 36, and the sliding cylinder 36b is guided by the cam surface 50a and moved in the direction of the optical axis S. The pressing force of 56 changes depending on the position of the rear lens frame 36. That is, as the rear lens frame 36 moves rearward, the pressing force increases, and the engagement protrusion 36d may press the cam surface 50a, which may increase the load of rotating the cam portion 50 and the cam shaft 48. is there. However, in the case of this embodiment, since the moving amount of the rear lens frame 36 is relatively small, the pressing force of the coil spring 56 does not become particularly large. Therefore, the cam part
The rotation of the cam portion 50 is hardly affected and the load of rotation of the cam portion 50 does not increase.

By the way, in the present embodiment, the pressing cam 52 is installed only in front of the cam portion 50. However, this is because the cam surface 50a at the rear portion of the cam portion 50 has a gentle inclination angle and the rear lens frame 36 is fixed. Even if the coil spring 56 is directly pressed, the coil spring 56
This is because the pressing force of does not change significantly. Therefore, another pressing cam may be installed behind the cam portion 50. In this case, the pressing force applied to the cam portion 50 from the rear is substantially constant, and the load of the rotation of the cam shaft 48 does not change.

Further, in this embodiment, the cam portion 50 and the pressing cam are
Since 52 is a separate body, each component may be molded separately. For this reason, the cylindrical groove cam can be molded more easily than integrally molded, and the molding is prevented from being complicated and the manufacturing cost of parts being increased.

In this embodiment, the lens moving mechanism 58 is described as being provided in the zoom lenses 24 and 26 of the finder optical system 20, but it may be provided in another lens. For example, the structure may be provided in the focus lens of the photographing optical system. In this case, the load of the movement of the focus lens becomes substantially constant regardless of the position of the focal point, the movement of the focus lens becomes smooth, and the focusing operation is performed more reliably.

[0035]

As described above, according to the cam structure of the lens moving mechanism according to the present invention, the lens in the optical system is held by the lens frame, and the engaging portion of the lens frame is engaged. Since the lens is moved in the optical axis direction by operating the moving cam, the force with which the engaging portion presses the positive moving cam is maintained substantially constant regardless of the position of the lens frame. Therefore, regardless of the position of the lens, the load for operating the certainty cam becomes substantially constant, and the output of the motor or the like for operating the certainty cam can be made substantially constant. Therefore, the operation of the positive movement cam becomes stable, and the lens moves smoothly. Also,
Since it is not necessary to use the above-mentioned motor or the like having a large output, it is possible to contribute to reduction in size and weight of the camera and cost reduction.

Further, the width of the cam groove of the positive cam is freely changeable, and urging means for urging the cam groove in a direction to reduce the width is provided, and both side walls of the cam groove serve as an engaging portion of the lens frame. In the case of the sandwiching structure, since the front portion and the rear portion of the engaging portion are always in contact with the cam groove, backlash does not occur even if the lens frame moves in either the front or rear direction. . Therefore, the lens is accurately positioned and the optical system is operated reliably.

Further, since the lens moving mechanism according to the present invention is constructed by using the cam of the conventional lens moving mechanism as the positive moving cam, it is not necessary to improve other members.
Therefore, the parts of the conventional lens moving mechanism can be used as they are, and the manufacturing cost does not increase significantly.

[Brief description of drawings]

FIG. 1 is a partially omitted sectional view showing an embodiment of a lens moving mechanism according to the present invention.

FIG. 2 is a schematic perspective view of a finder including a lens moving mechanism according to the present invention.

3 is a partially omitted sectional view showing a conventional lens moving mechanism, which corresponds to FIG.

[Explanation of symbols]

 20 Viewfinder optical system 24 Front zoom lens 26 Rear zoom lens 32 Viewfinder barrel 34 Front lens frame 34d Engagement protrusion (engagement part) 36 Rear lens frame 36d Engagement protrusion (engagement part) 48 Cam shaft 50 Cam part (proactive movement) Cam) 50a Cam surface (cam groove side wall) 52 Presser cam (proactive cam) 52a Cam surface (cam groove side wall) 54 Coil spring (biasing means) 56 Coil spring 58 Lens moving mechanism

Front page continuation (72) Inventor Mitsufumi Misawa 3-1345 Izumi, Asaka-shi, Saitama Fuji Shashin Film Co., Ltd.

Claims (2)

[Claims] 1. A lens frame for holding a lens in an optical system,
In a lens moving mechanism in which an engaging portion of the lens frame is engaged with a lens moving cam, and the lens frame is moved in the optical axis direction by the operation of the lens moving cam, the lens moving cam is composed of a positive moving cam. The structure of the cam of the lens moving mechanism characterized by. 2. A width of a cam groove of the positive cam is freely changeable, and a biasing means for biasing the width of the cam groove is provided. Both side walls of the cam groove serve as an engaging portion of the lens frame. The cam structure of the lens moving mechanism according to claim 1, wherein the cam is sandwiched.