JP3163789B2 - Camera lens barrel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens barrel used for an image pickup apparatus such as a video camera, and more particularly to a four-group zoom / inner focus type movable lens group having an autofocus function and an electric zoom function. The present invention relates to a camera lens barrel driven by a coil-type linear motor.

[0002]

2. Description of the Related Art For example, in a video camera, an inner focus type zoom lens mirror for performing focusing, correction, image formation, and the like by moving a master lens group for focusing and a variator lens group for zooming along an optical axis. Tubes are known. In this type of lens barrel, a so-called auto-focus method for automatically adjusting the focus, correction, and image formation of a read image is also known.

A lens barrel employed in a conventional zoom / inner focus type image pickup apparatus is a four-group lens in which a first and third lens group are fixed and a second and fourth lens group are movable. In addition to being configured from a system, for example, a focusing function, a correction function, and an imaging function are provided to the movable fourth group lens, and the moving positions of the second group lens and the fourth group lens are automatically controlled. I have.

In some of such camera lens barrels, a movable lens group for zooming or focusing is driven by a DC motor or a stepping motor. However, high torque can be generated with low power consumption. There has also been proposed a motor employing a voice coil type linear motor (hereinafter referred to as a VC type linear motor) with an increased zoom / focus speed.

[0005]

However, in a conventional camera lens barrel, for example, when a VC-type linear motor is used as a drive source of the fourth group movable lens, the VC-type linear motor is offset from the optical axis of the lens group. The thrust of the VC type linear motor is not smoothly transmitted to the fourth group lens group moving along the optical axis because the fourth group lens group is configured to be driven through the arm. Therefore, the responsiveness of zoom and focus is reduced.

The present invention has been made in view of such problems of the prior art, and employs a VC linear motor as a drive source for a movable lens group and moves a drive center of the VC linear motor. An object of the present invention is to align the optical axis with the optical axis of the lens group, accurately align the drive center axis with the optical axis, and firmly fix the VC linear motor.

[0007]

In order to achieve the above object, a camera lens barrel according to the present invention comprises at least one movable lens group and a voice coil type for moving the movable lens group along an optical axis. A linear motor, wherein the movable lens group is attached to a mover of the voice coil linear motor, and the voice coil linear motor is driven so that a drive center axis of the voice coil linear motor coincides with the optical axis. In a camera lens barrel in which the yoke is fixed to the barrel, positioning uneven portions are formed on each of the yoke and the barrel so that the drive center axis of the voice coil type linear motor coincides with the optical axis. Forming a temporary fixing engagement portion for temporarily fixing the yoke to the lens barrel when assembling the yoke to the lens barrel, in each of the yoke and the lens barrel; Rutotomoni, is characterized in that fixed in the mechanical fastening means and said barrel and said yoke.

[0008] The mechanical fastening means is a screw screwed along the optical axis direction to fasten the back yoke and the bottom surface of the lens barrel. Further, the mechanical fastening means is formed by inserting a projection formed in the lens barrel into a through hole formed in the back yoke, and then caulking the projection. Further, the mechanical fastening means is a screw that is screwed along a direction not parallel to the optical axis and fastens a back yoke and a side surface of the lens barrel.

[0009]

The voice coil type linear motor comprises a yoke in which a back yoke and a center yoke are integrally formed, a permanent magnet provided in the yoke to form a magnetic field, and a mover around which a coil is wound. A DC motor that moves and moves a mover along a center yoke by switching a current direction of a coil.

The movable lens group is attached to the mover while the yoke is attached to the lens barrel so that the drive center axis of the voice coil type linear motor coincides with the optical axis of the lens group. As a result, the drive center axis of the voice coil type linear motor, that is, the center of the thrust of the mover coincides with the optical axis, and this thrust is transmitted directly from the linear motor to the movable lens group. The center of the lens group does not shift from the optical axis, and the movable lens group moves smoothly.

In this case, in the camera lens barrel of the present invention, since the positioning uneven portion is formed on each of the yoke and the barrel, the drive center axis of the voice coil type linear motor and the optical axis coincide with each other with high precision. Can be done.

When the yoke is assembled to the lens barrel, the temporary fixing engagement portions for temporarily fixing the yoke to the lens barrel are formed on each of the yoke and the lens barrel. Can be done.

Further, the yoke and the lens barrel are constituted by screws screwed into the optical axis direction or non-parallel to the optical axis, or mechanical fastening means such as caulking a projection formed on the lens barrel, Since the back yoke and the lens barrel are fixed, the mounting strength of the motor is increased, and the stability and reliability of the lens barrel can be improved.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view showing an entire configuration of a lens barrel according to one embodiment of the present invention, FIG. 2 (A) is a view taken in the direction of arrow A shown in FIG. 1, and FIG. 2 (B) is a view shown in FIG. It is sectional drawing which follows the BB line.

As shown in FIG. 1, the lens barrel according to the present embodiment includes a first group lens 1, a second group lens 2, a third group lens 3, Fourth lens group 4
And a CCD (Charge Coupled Device, not shown) as an image pickup device is disposed at the focal position of the fourth group lens 4.

The first lens group 1 is a focusing level group.
It is composed of a plurality of lenses, for example, three lenses, and is fixed in the main lens barrel 5. The second group lens 2 is a lens group for zooming (variable magnification), and is composed of a plurality of lenses, for example, three lenses. The second group lens 2 is supported by two guide shafts 6 and 7 and has an optical axis. It is provided movably along the II ′ direction.

The third lens group 3 is a correcting lens group.
It is composed of one or more lenses, for example, one lens, and is fixed in the rear barrel 8. Further, the fourth group lens 4 is a focusing lens group, and includes a plurality of lenses.
For example, it is composed of two sheets, and is provided movably along the optical axis II ′. An iris 9 is provided between the fixed first lens unit 1 and the third lens unit 3 while being sandwiched between the main lens barrel 5 and the rear lens barrel 8. By means of 10, the iris 9 is driven up and down. “11” is a stepping motor that is fixed to the main lens barrel 5 and moves the second lens group 2.

In the lens barrel of the present embodiment, the lens barrel is supported by two guide shafts 12 and 13 and serves as a drive source for the fourth lens unit 4 which is provided to be movable along the optical axis II '. ,
The voice coil type linear motor 18 is employed.

The VC linear motor 18 is a linear DC motor including a yoke 17 and a permanent magnet 16 as a stator, and a movable element 15 around which a coil 14 is wound. As shown in FIGS. 1 and 2B, the yoke 17 includes a back yoke 17a to which four permanent magnets are attached, and a center yoke 17b formed in an annular shape at the center of the back yoke. It forms a magnetic field by the permanent magnet 16.

On the other hand, the movable element 15 to which the fourth group lens 4 is attached is inserted between the main lens barrel 5 and the rear lens barrel 8 through the lens holder of the third lens group 3. It is supported by guide shafts 12 and 13 and is slidable along the optical axis II ′. As shown in FIG. 2 (B), the mover 15 is inserted into the center yoke 17b with a small gap, and switches the current direction of the coil 14 wound around the outer periphery, thereby moving the mover 15, ie, the fourth mover. The group lens 4 can move forward and backward along the center yoke 17b.

In particular, in the lens barrel of the present embodiment, the drive center axis of the mover 15 and the optical axis II 'are made to coincide.
As a result, the thrust of the VC linear motor 18 is directly transmitted to the mover 15, that is, the fourth group lens 4, so that the center of the fourth group lens 4 does not deviate from the optical axis II ′, and , The fourth group lens 4 moves smoothly and at high speed.

As described above, in order to precisely match the drive center axis of the VC type linear motor 18 with the optical axis II ′, this embodiment adopts the following structure as a mounting structure of the VC type linear motor. I have.

First, in order to accurately position the yoke 17 and the rear barrel 8, positioning recesses (through holes as shown) 19 a, 19 b are formed in the back yoke 17 a.
And a positioning projection 20 (only one is shown) is formed on the inner surface of the rear barrel 8.

In the embodiment shown in FIGS. 2A and 2B, the left side of the positioning recess of the back yoke 17a (FIG. 2A).
The positioning concave portion 19a is formed with high precision, and the positioning concave portion 19b on the right side is formed as a long hole so as to absorb the molding tolerance of the positioning convex portion 20 formed in the rear barrel 8. Then, a positioning projection 20 formed on the rear barrel 8 is formed.
Is fitted into the left positioning concave portion 19a to secure the assembly accuracy of the yoke 17 and the rear barrel 8.

The yoke 17 and the rear barrel 8 are connected to the tap 21 cut in the back yoke 17a by the rear barrel 8
Screw 22 from the bottom surface 8a side of the back yoke 1
7a is attached by being pulled into close contact with the bottom surface 8a of the rear lens barrel 8.

In this case, it is desirable to use the dead space of the yoke 17 to determine the mounting position of the screw 22 so that the tip of the screw 22 does not interfere with the mover 15 and the permanent magnet 16. By the way, in the embodiment shown in FIG. 2B, the tap 21 formed on the yoke 17 is
Is located substantially at the end of the back yoke 17a, and there is a possibility that the tip of the screw 22 may interfere with the corner of the back yoke 17a. Therefore, the notch 23 is formed at the corner of the back yoke 17a.

Since the back yoke 17a and the rear barrel 8 are fixed by the screws 22, the mounting strength of the VC type linear motor is increased, and the stability and reliability of the lens barrel can be improved. . In addition, the screw 22 according to the present embodiment connects the back yoke 17a to the bottom surface 8a of the rear barrel 8.
Optical axis I
Positioning of -I 'and the drive center axis becomes more accurate.

Further, in this embodiment, there is provided a means for temporarily fixing the yoke 17 to the rear barrel 8 when tightening the screw 22 described above. That is, a dowel (temporarily fixed engaging portion) 24 is formed on the side surface of the back yoke 17a, and an engaging hole (temporarily fixed engaging portion) 25 that engages with the dowel 24 is formed on the side surface of the rear barrel 8. (See FIGS. 1 and 2B). Dowel 24 and engagement hole 2 in this case
The positional relationship between the yoke 17 and the lens barrel 5 does not need to be formed with high accuracy. At least when the yoke 17 is screwed to the rear barrel 8, it is sufficient that the yoke 17 is temporarily fixed.
In addition, “26” shown in FIG. 2B is a tapered surface for facilitating insertion of the yoke 17 and engagement of the dowel 24 with the engagement hole 25.

As described above, if the temporary fixed engaging portions 24 and 25 are formed on the yoke 17 and the rear barrel 8, respectively, the work of screwing the yoke can be performed extremely easily.

The present invention can be variously modified without being limited to the above-described embodiment. FIG. 3 is a half sectional view showing another embodiment of the present invention, and FIG. 4 is a half sectional view showing still another embodiment of the present invention.

In the embodiment shown in FIG. 3, caulking is employed as mechanical fastening means for assembling the yoke 17 and the rear lens barrel 8. In this case, the projection 2 is provided on the inner surface of the rear barrel 8.
7 is formed, and a through hole 28 positioned in the back yoke 17a is opened, and when the yoke 17 is inserted into the rear lens barrel 8, the projection 27 is inserted into the through hole 28 to perform positioning. Then, the tip of the projection 27 is crushed by, for example, ultrasonic welding or the like to perform caulking.

In this embodiment, in addition to the effects of the above-described first embodiment, there is an advantage that the positioning uneven portion and the mechanical fastening means can be shared.

In the case where the mechanical fastening means in the present invention is constituted by screws, even if the function of a pulling screw is not provided as shown in FIG.
May be fastened from the side surface of the rear barrel 8.
However, in this case, the dowels 24 formed on the yoke 17
It is necessary to make the positional relationship between the lens and the engaging hole 25 formed in the rear lens barrel 8 accurate.

The embodiments described above are described to facilitate understanding of the present invention, but are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design changes and equivalents belonging to the technical scope of the present invention. For example, in the above-described embodiment, the fourth group lens has V
Although the C-shaped linear motor is applied, the lens barrel of the present invention is not limited to the fourth lens group as long as it is a movable lens group.

[0035]

As described above, according to the present invention, since the positioning uneven portion is formed on each of the yoke and the lens barrel, the drive center axis of the voice coil type linear motor and the optical axis can be accurately matched. Can be done.

In attaching the yoke to the lens barrel, the temporary fixing engagement portions for temporarily fixing the yoke to the lens barrel are formed on each of the yoke and the lens barrel. Can be done.

Further, the yoke and the lens barrel are constituted by screws screwed into the optical axis direction or non-parallel to the optical axis, or mechanical fastening means such as caulking projections formed on the lens barrel. Since the back yoke and the lens barrel are fixed, the mounting strength of the motor is increased, and the stability and reliability of the lens barrel can be improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration of a lens barrel according to one embodiment of the present invention.

2A is a view taken in the direction of the arrow A shown in FIG. 1, and FIG.
It is sectional drawing which follows the BB line of (A).

FIG. 3 is a half sectional view showing another embodiment of the present invention.

FIG. 4 is a half sectional view showing still another embodiment of the present invention.

[Explanation of symbols]

 II ′ optical axis 4 fourth lens group (movable lens group) 8 rear lens barrel 15 movable element 17 yoke 18 voice coil type linear motor 19a, 19b positioning concave part 20 positioning convex part 22, 29: Screw (mechanical fastening means) 24: Dowel (temporary fixing engagement part) 25: Through hole (temporary fixing engagement part) 27: Projection (mechanical fastening means) 28: Through hole (mechanical fastening means)

Continuation of the front page (56) References JP-A-1-206681 (JP, A) JP-A-1-287412 (JP, A) JP-A-62-286832 (JP, A) JP-A-60-146926 (JP) , U) Japanese Utility Model Open 2-33587 (JP, U) Japanese Utility Model Showa 63-94412 (JP, U) Japanese Utility Model Open Utility Model 2-1715 (JP, U) Japanese Utility Model Open Utility Model 59-46309 (JP, U) 64-38610 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B ⁷ /02-7/105

Claims (4)

(57) [Claims] 1. A voice coil type linear motor having at least one movable lens group and a voice coil type linear motor for moving the movable lens group along an optical axis, wherein the movable lens group is used as a mover of the voice coil type linear motor. A voice coil linear motor, wherein the yoke of the voice coil linear motor is fixed to the lens barrel such that a drive center axis of the voice coil linear motor coincides with the optical axis; Forming a positioning uneven portion on each of the yoke and the lens barrel such that the drive center axis of the yoke coincides with the optical axis; and temporarily fixing the yoke to the lens barrel when assembling the yoke to the lens barrel. And forming the temporary fixed engaging portion on each of the yoke and the lens barrel, and fixing the yoke and the lens barrel by mechanical fastening means. A camera lens barrel according to symptoms. 2. The camera according to claim 1, wherein the mechanical fastening means is a screw screwed along the optical axis direction to fasten a back yoke and a bottom surface of the lens barrel. Lens barrel. 3. The mechanical fastening means according to claim 1, wherein the projection formed on the lens barrel is inserted into a through hole formed in the back yoke, and then the projection is caulked. A lens barrel for a camera according to item 1. 4. The mechanical fastening means according to claim 1, wherein said mechanical fastening means is a screw which is screwed in a direction not parallel to said optical axis and tightens a back yoke and a side surface of said lens barrel. A lens barrel for a camera according to item 1.