JP6992979B2 - Lens barrel - Google Patents

Description

The present invention relates to a lens barrel that has a simple structure but can effectively block light even with a large extension amount such as a high-magnification zoom lens or a macro lens.

In a high-magnification zoom lens, a macro lens, or the like, in order to satisfy the necessary functions, the moving group such as the zoom lens group or the focus lens group must be largely extended. There is a problem to be aware of when the moving group tries to move out greatly by zooming or focusing.

For example, there is a problem that the internal structure can be seen by the photographer due to the large distance between the moving lens group and the fixed lens group, or flare occurs due to the passage of external light through the gap created between the lens groups. It is a problem that stray light such as ghosts and ghosts are generated and light is collected on the internal mechanical parts.

In order to solve these problems, it is common practice to arrange a light-shielding part between the lens group and the lens group in which the distance between the groups is greatly widened.

In order to move the light-shielding parts arranged between the moving lens group and the fixed lens group to the optimum position, for example, a method of using a cam groove and a straight guide groove can be considered as in the moving lens group.

However, when such a configuration is adopted, the cam grooves for the moving lens group provided in the cam cylinder and the cam grooves for the light-shielding parts generally have different angles and lengths, so that the cam grooves interfere with each other. The cam groove may not be cut or the distance between the cam grooves may be narrowed, resulting in insufficient strength of the cam cylinder.

Therefore, there is also a conventional technique for moving light-shielding parts without using a cam groove.

For example, in the invention described in Patent Document 1, a first drive mechanism held immovably in the optical axis direction, a second drive mechanism driven in the optical axis direction by the first drive mechanism, and a second drive mechanism. In a camera having a plurality of lens groups driven in the optical axis direction by the camera, and having a rearmost lens group lens holding frame unit having a configuration in which the lens group most protrudes from the second drive mechanism toward the film side between the retractable end and the wide end. A camera equipped with a moving mask that is connected to the second drive mechanism via a tension spring and is normally urged toward the objective side to be in close contact with the rear part of the second drive mechanism, but at the wide end is in close contact with the last group of the lens. Has been done.

According to the present invention, in a two-stage extension type lens barrel, an urging mechanism that adheres a moving mask to the last group of the photographing lens at the wide end and to the rear of the straight guide end at the tele end without taking up extra space. By devising the assembly structure, space can be saved, the opening of the moving mask can be made as small as possible, and the effect of blocking harmful luminous flux can be improved.

Further, in the invention described in Patent Document 2, the movable light-shielding plate 30 is moved back and forth along the optical axis substantially integrally with the second lens group 7 in the first region on the wide-angle end side in the entire zoom range. The arm 30c formed on the movable light-shielding plate 30 is pressed against the rear end surface 5d of the holding frame 5 of the second lens group 7 by the spring 32, and the movable light-shielding plate 30 is first placed in the second region on the telephoto side of the first region. The front surface 30d is pressed against the rear end surface of the straight cylinder 2 so as to move forward and backward almost integrally with the lens group 6. Then, in the third region from the second region to the telephoto end, the operation of the movable light-shielding plate 30 is restricted by the stopper 1d formed on the fixed cylinder 1, and the distance between the movable light-shielding plate 30 and the second lens group 7 is widened. The zoom lens barrel is disclosed.

According to the present invention, a light-shielding plate having an opening having an opening having a size defined at the wide-angle end can be positioned at a different position with respect to the rear lens group for each region, so that an excellent flare prevention effect can be obtained. .. Further, the light-shielding plate is provided on the rear end surface of the member that holds the rear lens group in the first region and after the member that holds the front lens group in the second region, without using a complicated mechanism such as a cam. Since it is sufficient to provide a means for pressing the end face with a spring or the like, it is possible to prevent the configuration from becoming complicated.

Further, in the invention described in Patent Document 3, it is a retractable lens barrel provided with a lens system whose position changes depending on the photographing position and the storage position, and a lens group that adjusts the position in the optical axis direction at the time of assembly is fixed. Lens fixing frame; Moving cylinder member that is screwed into this lens fixing frame and moved in a predetermined locus; A light-shielding member whose light-shielding portion is located behind the lens fixing frame; A spring member; and behind the light-shielding member, which compresses the first spring member by contacting the light-shielding member rearwardly urged by the first spring member when located in the storage position. A light-shielding structure for a retractable lens barrel with a positioned retractable contact member; is disclosed.

According to the present invention, in the retractable lens barrel, not only the degree of freedom in installing the light-shielding member in the shooting state is improved, but also the size and thickness can be reduced.

Japanese Unexamined Patent Publication No. 8-29850 Japanese Unexamined Patent Publication No. 6-201966 Japanese Patent No. 4130963

However, the above-mentioned conventional technique has the following problems.

That is, in the invention disclosed in Patent Document 1, the moving mask 16 is configured to be in close contact with the rear portion of the straight guide ring 6 in the telephoto end state (FIG. 3). In this case, if the position of the moving mask 16 at the telephoto end is to be changed due to a design change or the like, the total length of the straight guide ring 6 itself must be reduced or lengthened, and the degree of freedom in design is extremely low. Further, the tension spring 17 is connected between the straight guide ring 6 and the moving mask 16 to form an urging mechanism, and it is difficult to unitize them in combination with the above-mentioned close contact configuration, and the assemblability and the degree of freedom in design are improved. It will drop.

Further, in the invention disclosed in Patent Document 2, since the stopper pin 1d projecting from the outer peripheral surface of the fixed cylinder 1 and the first light-shielding plate 30 are in contact with each other, the outer diameter of the fixed cylinder 1 becomes large, and the product Will lead to an increase in size. Further, if an attempt is made to form such a stopper pin 1d, the processing cost will increase. Further, as in the case of Patent Document 1 described above, since it is difficult to unitize the unit, the assemblability and the degree of freedom in design are lowered.

Further, in the invention disclosed in Patent Document 3, a conical coil spring 28, which is a compression spring, is inserted between the light-shielding frame 27 and the second group frame 26 in order to always urge the light-shielding frame 27 rearward. Therefore, since the spring is arranged over the entire circumference, it is not possible to arrange a member other than the spring, and the degree of freedom in design is reduced. Further, if a plurality of small-diameter coil springs are used instead of the conical coil springs 28 in order to prevent this, it becomes necessary to take measures against the so-called buckling phenomenon that occurs when the coil springs are compressed.

Another issue common to these patent documents is the accuracy of centering of light-shielding parts. That is, the diameter of the opening can be made as small as possible by accurately aligning the center of the opening of the light-shielding part with the optical axis and centering the light. This is important because it is possible to accurately block only unnecessary stray light without blocking the necessary effective light rays.

In Patent Documents 1 and 3, the moving mask 16 formed of the press parts and the leg portion extending in the optical axis direction from the annular light-shielding portion 27a are engaged with the groove portion provided in the straight guide ring 6 and the intermediate cylinder member 25. It can be said that the centering is roughly done by this. However, in order to perform centering with higher accuracy, it is necessary to increase the thickness of the legs and the grooves, which causes a space problem. In addition, there is a limit to the bending accuracy of the pressed parts.

Further, in Patent Document 2, only a study is made to correct the position in the optical axis direction by using a protrusion, and the centering of the light-shielding plate 30 is not mentioned in the first place.

The present invention has been made in view of such a situation, and a lens barrel capable of effectively blocking light even with a large extension amount such as a high-magnification zoom lens or a macro lens, although it has a simple structure. The purpose is to provide.

In order to achieve the above object, the lens barrel for carrying out the present invention has at least a cam cylinder having a first cam groove, and at least a first straight guide groove and a second straight guide groove. A fixed cylinder adjacent to the cam cylinder in the radial direction and at least a part of a lens group that advances and retreats in the optical axis direction at the time of focusing or scaling are held in the first cam groove and the first straight guide groove. A lens moving frame that engages and moves forward and backward in the optical axis direction, and a light-shielding member moving frame that holds a light-shielding member that prevents harmful light from entering and engages with the second straight guide groove to move forward and backward in the optical axis direction. And a plurality of coil springs inserted between the lens moving frame and the light-shielding member moving frame to urge each other in a direction of attracting each other, and the lens moving frame moves during focusing or scaling. The range includes the first region in which the light-shielding member moving frame moves integrally with the lens moving frame by the urging force of the coil spring, the light-shielding member moving frame stops, and the lens moving frame overcomes the urging force of the coil spring. The light-shielding member moving frame comprises a second region that moves independently, and is characterized in that the light-shielding member moving frame stops when it comes into contact with one end of the second straight-ahead guide groove in the second region.

Further, the lens barrel in which the present invention is carried out is preferably characterized in that the outer peripheral surface of the light-shielding member moving frame that slides on the inner peripheral surface of the fixed cylinder is an in-row surface.

Further, in the lens barrel according to the present invention, preferably, the engaging portion of the light-shielding member moving frame that engages with the second straight guide groove is a substantially rectangular parallelepiped, and the side wall of the second straight guide groove. It is characterized in that the side surface of the engaging portion that slides on the surface is an in-row surface.

According to the lens barrel according to the present invention, it is possible to provide a lens barrel capable of effectively blocking light even with a large extension amount such as a high-magnification zoom lens or a macro lens, although it has a simple structure. With the goal.

It is sectional drawing of the lens barrel which is one Embodiment of this invention, and shows the upper half section at the time of infinity photography, and the lower half section at the time of the shortest distance photography. It is a developed perspective view which shows the relationship between the 2nd group moving frame and a light-shielding ring unit. It is a partial perspective view for demonstrating the position of the light-shielding ring at the time of the intermediate distance photography. It is a partial perspective view for demonstrating the rectangular parallelepiped key which is a 2nd Embodiment.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. The present invention is not limited to this embodiment.

FIG. 1 is a cross-sectional view of a lens barrel 100 according to an embodiment of the present invention. The upper half cross section of this figure shows the state at the time of infinity shooting, and the lower half cross section shows the state at the time of the shortest distance shooting.

As shown in this figure, the lens barrel 100 has an imaging optical system consisting of three lens groups G1 to G3 in order from the subject side, as well as a fixed cylinder 110, a cam cylinder 120, and a straight-moving cylinder as main configurations. It has a 130 and a focus operation ring 140. The straight cylinder 130, the fixed cylinder 110, the cam cylinder 120, and the focus operation ring 140 are arranged in this order from the inner peripheral side with the optical axis of the imaging optical system as the center.

The lenses of each lens group are fixed to their respective mirror chambers by caulking, a presser ring, or the like, and each mirror chamber is further fixed to the lens moving frame. In the lens barrel 100 of the present embodiment, the first lens group G1 and the second lens group G2 are moved back and forth in the optical axis direction during focusing.

The group 1 moving frame 151 holds the first lens group G1 and is fastened to the straight cylinder 130 by a screw (not shown). The straight cylinder 130 is engaged with a straight guide groove (not shown) provided in the fixed cylinder 110 and a cam groove (not shown) provided in the cam cylinder 120 via a cam follower (not shown). As a result, the group 1 moving frame 151 is held at a predetermined position.

The second group moving frame 152 holds the second lens group G2, and the straight guide groove 111 provided on the fixed cylinder 110 and the cam groove 121 provided on the cam cylinder 120 via the three second group cam followers 161. Is engaged with. As a result, the second group moving frame 152 is held at a predetermined position. The aperture unit 162 is fixed to the subject side of the second group moving frame 152. The aperture unit 162 is a variable aperture, and the aperture diameter changes according to an instruction from a camera control unit (not shown).

The light-shielding ring unit 170 is located on the image plane side of the second group moving frame 152. A light-shielding ring 171 is fixed to the light-shielding ring unit 170. Three light-shielding ring cam followers 172 fixed to the light-shielding ring unit 170 are engaged only with the straight guide groove 112 provided in the fixed cylinder 110. Further, a plurality of coil springs 173 are hung between the two groups moving frame 160 located in the front. The function of the coil spring 173 will be described in detail later.

The fixed cylinder 110 and the cam cylinder 120 constitute a cam mechanism, and when the user operates the focus operation ring 140, the operating force is transmitted to the cam cylinder 120 and the cam cylinder 120 rotates about the optical axis. Each of the cam followers of the first group and the second group is moved back and forth in the optical axis direction in cooperation with the cam groove and the straight guide groove, which are engaged with each other by the rotation of the cam cylinder 120.

The third group holding frame 180 is located on the image plane side of the second group moving frame 160. The position of the three-group moving frame 180 is unchanged with respect to the above-mentioned focus operation.

FIG. 2 is a developed perspective view showing the relationship between the two-group moving frame 160 and the light-shielding ring unit 170. As shown in this figure, the two-group moving frame 160 and the light-shielding ring unit 170 have a substantially disk shape, and are configured to move back and forth on the inner peripheral side of the cylindrical fixed cylinder 110 in the optical axis direction.

Three second group cam followers 161 are fixedly installed on the outer periphery of the second group moving frame 160. As described above, these cam followers are engaged with the straight guide groove 111 and the cam groove 121.

On the other hand, three light-shielding ring cam followers 172 are fixedly provided on the outer periphery of the light-shielding ring unit 170. As described above, these cam followers are engaged only with the straight guide groove 112 of the fixed cylinder 110 located on the inner peripheral side. Therefore, the height of the light-shielding ring cam follower 172 is lower than that of the second group cam follower 161.

A coil spring 173 is inserted between the second group moving frame 160 and the light shielding ring unit 170. Three coil springs 173 are arranged in a 120 ° distribution, and the two-group moving frame 160 and the light-shielding ring unit 170 are connected via these. The coil spring 173 is a tension spring, and an urging force in a direction of approaching each other is always acting.

As a result of the focus operation by the user described above, the positional relationship of each element of the lens barrel 100 changes from the infinity shooting state shown in the upper half cross section of FIG. 1 to the shortest distance shooting state shown in the lower half cross section of FIG. Change. Hereinafter, the movement of each element accompanying the focus operation will be described.

In the infinity shooting state, the light-shielding ring unit 170 is in contact with the group 1 moving frame 150 and the group 2 moving frame 160 located at a predetermined interval by the urging force of the coil spring 173. .. As the contact surface between the two, a plurality of contact portions (not shown) are provided, and the distance between the two is set so as to be an optimum distance in the infinity shooting state.

As described above, unlike the two-group moving frame 160 that moves in the optical axis direction by the cam groove 121 in a predetermined locus, the light-shielding ring unit 170 does not have a cam groove, and the light-shielding ring cam follower 172 with respect to the fixed cylinder 110. It is in a suspended state. Therefore, the straight guide grooves of the two-group moving frame 160 and the light-shielding ring unit 170 are set so that they can come into contact with each other in the infinity state.

FIG. 3 is a partial perspective view for explaining the position of the light-shielding ring unit 170 with respect to the fixed cylinder 110, and shows a state at the time of intermediate distance shooting. In this figure, it can be seen that the two-group moving frame 160 and the light-shielding ring unit 170 are moving toward the subject in the optical axis direction along the respective straight guide grooves as compared with the case of infinity shooting (FIG. 1).

From the state shown in FIG. 1 (during infinity shooting) to the state shown in this figure, the two-group moving frame 160 and the light-shielding ring unit 170 are in contact with each other due to the influence of the coil spring 173 and are integrated with each other toward the subject. I'm moving. Specifically, the light-shielding ring unit 170 having no dedicated cam groove moves to the second group moving frame 160 adjacent to the subject side while being pulled by the coil spring 173. Since the light-shielding ring unit 170 is only suspended from the light-shielding ring cam follower 172, the elastic force of the coil spring 173 does not fall below the static friction force of the light-shielding ring cam follower 172. Therefore, the light-shielding ring unit 170 follows the group 2 moving frame 160 in a contact state without the coil spring 173 extending.

The follow-up of the light-shielding ring unit 170 by the coil spring 173 is performed within the range of the length at which the straight guide groove 112 is cut. That is, as shown in this figure, the light-shielding ring unit 170 is followed until the light-shielding ring cam follower 172 comes into contact with the subject-side end surface of the straight guide groove 112.

The section in which the light-shielding ring unit 170 follows the second group moving frame 160 from the infinity shooting state (upper half cross section of FIG. 1) to the above-mentioned contact stop state of the light-shielding ring cam follower 172 (FIG. 3) is also the first region. I will call it.

Consider the case where the focus operation ring 140 is further rotated from the state shown in this figure. In this case, the second group moving frame 160 is continuously moved toward the subject in the optical axis direction according to the shape of the cam groove 121. On the other hand, as described above, the light-shielding ring unit 170 cannot move further toward the subject in the optical axis direction because the light-shielding ring cam follower 172 is already in contact with the end of the straight guide groove 112, and the distance between the two is large. Come away.

The length of the coil spring 173 increases as the second group moving frame 160 and the light-shielding ring unit 170 separate from each other.

Further, when the focus operation ring 140 is rotated, the second group moving frame 160 continues to move toward the subject side, and eventually comes into contact with the mechanical end and stops. This state is the shortest distance shooting state, which is shown in the lower half cross section of FIG.

The two-group moving frame 160 from the contact state of the light-shielding ring cam follower 172 (FIG. 3) to the contact stop state of the above-mentioned second-group cam follower 161 (lower half cross section of FIG. 1) moves independently from the light-shielding ring unit 170. The section to be used is also referred to as a second region.

The outer peripheral surface of the light-shielding ring unit 170 shown in FIG. 2 has an in-row surface 174, which is slidable with the inner peripheral surface of the fixed cylinder 110 adjacent in the radial direction, but at the same time, rattling in the radial direction. Is set to be small enough. By suppressing the rattling in the radial direction, it is possible to reduce error cases such as the light shielding ring 171 accidentally cutting the effective light ray or passing the harmful light ray to be cut.

As described above, according to the lens barrel in which the present invention is carried out, the stopper of the light-shielding ring unit is the end face of the straight guide groove with which the cam follower of the light-shielding ring unit is engaged, so that the outer diameter is increased. It is possible to increase the degree of freedom in designing the stopper position without using it.

Further, since the two-group moving frame and the light-shielding ring unit are connected by a plurality of coil springs, it is possible to assemble only these two parts, which is advantageous in terms of assembling and management. Further, since there is no restriction on the insertion direction when these parts are inserted into the fixed cylinder, the degree of freedom in the assembly process can be increased.

In addition, since the outer peripheral surface of the light-shielding ring unit is used as an in-row surface to suppress rattling in the radial direction between the light-shielding ring unit and the fixed cylinder, high-precision centering of the light-shielding ring unit is possible, and the light-shielding ring opening is extended to the limit of effective light rays. It can be made smaller to improve the light blocking effect of harmful rays.

In the above-described embodiment, the in-row surface 174 provided on the outer periphery of the light-shielding ring unit 170 is used as a mechanism for improving the centering accuracy of the light-shielding ring unit 170, but the present invention is not limited to this.

For example, as the light-shielding ring cam follower 172 that suspends the light-shielding ring unit 170 without using an inlay on the outer peripheral surface, a rectangular parallelepiped key as shown in FIG. 4 is adopted instead of a general columnar cam follower, and a key is further used. Even if the side surface is slid with the side wall of the linear guide groove 112 that engages as an inlay surface, the same effect as that of the above-described embodiment can be obtained.

That is, since the keys arranged by 120 ° distribution come into surface contact with the side wall of each straight guide groove 112, rattling in the radial direction can be suppressed, and the light-shielding ring unit 170 can be centered with high accuracy.

100 lens barrel, 110 fixed cylinder, 111 straight guide groove, 112 straight guide groove, 120 cam cylinder, 121 cam groove, 130 straight cylinder, 140 focus operation ring, 150 1 group moving frame, 160 2 group moving frame, 1612 Group cam follower, 162 aperture unit, 170 light-shielding ring unit, 171 light-shielding ring, 172 light-shielding ring cam follower, 173 coil spring, 174 inlay surface, 180 3 group holding frame

Claims (3)

With a cam tube having at least the first cam groove,
A fixed cylinder having at least a first straight guide groove and a second straight guide groove and adjacent to the cam cylinder in the radial direction.
Lens movement that holds at least a part of the lens group that moves forward and backward in the optical axis direction during focusing or scaling, and engages with the first cam groove and the first straight guide groove to move forward and backward in the optical axis direction. Frame and
A light-shielding member moving frame that holds a light-shielding member that prevents harmful light from entering and engages with the second straight guide groove to advance and retreat in the optical axis direction.
A plurality of coil springs inserted between the lens moving frame and the light-shielding member moving frame to urge each other in a direction of attracting each other, and a plurality of coil springs.
Have,
The moving range of the lens moving frame at the time of focusing or scaling is the first region in which the light-shielding member moving frame moves integrally with the lens moving frame due to the urging force of the coil spring, and the light-shielding member moving frame stops. The lens moving frame is composed of a second region in which the lens moving frame overcomes the urging force of the coil spring and moves independently.
The lens barrel, wherein the light-shielding member moving frame stops when it comes into contact with one end of the second straight guide groove in the second region. The lens barrel according to claim 1, wherein the outer peripheral surface of the light-shielding member moving frame that slides on the inner peripheral surface of the fixed cylinder is an in-row surface. The engaging portion of the light-shielding member moving frame that engages with the second straight guide groove is a substantially rectangular parallelepiped, and the side surface of the engaging portion that slides on the side wall of the second straight guide groove is an inlay surface. The lens barrel according to claim 1.

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