JPH06102447A - Lens barrel for camera - Google Patents

Abstract

PURPOSE:To accurately perform the alignment of a driving center axis and an optical axis and to firmly fix a VC type linear motor in the case the driving center of the VC type linear motor is aligned with the optical axis of a movable lens group. CONSTITUTION:This lens barrel for a camera is provided with movable lens groups 2 and 4, and a voice coil type linear motor 18 moving the lens groups 2 and 4 along the optical axis I-I'; and it is constituted by attaching the movable lens group 4 to the needle 15 of the motor 18 and fixing the yoke 17 of the motor 18 on the lens barrel 8 so that the driving center axis of the motor 18 may be aligned with the optical axis. Projecting and recessed parts for positioning 19 and 20 are respectively formed in the yoke 17 and the lens barrel 8 so that the driving center axis of the motor 18 may be aligned with the optical axis. Temporary fixing and engaging parts 24 and 25 temporarily fixing the yoke 17 in the lens barrel 8 in the case of assembling the yoke 17 in the lens barrel 8 are respectively formed in the yoke 17 and the lens barrel 8. The yoke 17 and the lens barrel 8 are fixed by mechanical fastening means 22, 27 and 29.

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 in an image pickup device such as a video camera, and more particularly, to a movable lens group of a four-group zoom / inner focus system having an autofocus function and an electric zoom function. The present invention relates to a lens barrel for a camera 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 focusing, correcting, and forming an image by moving a focusing master lens group and a zoom variator lens group along an optical axis. The cylinder is known. Further, in this type of lens barrel, there is also known a so-called autofocus system in which focusing, correction, and image formation of a read image are automatically adjusted.

A lens barrel used in a conventional zoom / inner focus type image pickup apparatus is a fourth group lens having a first group and a third group lens as a fixed system and a second group and a fourth group as a movable system. In addition to being composed of a system, for example, a focusing function, a correction function, and an image forming function are given to the movable fourth group lens to automatically control the moving positions of the second group lens and the fourth group lens. There is.

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

[0005]

However, in the conventional lens barrel for a camera, for example, when a VC linear motor is used as a drive source for the fourth movable lens, the VC 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 lens group that moves along the optical axis because the fourth lens group is arranged via the arm to drive the fourth lens group. Therefore, the responsiveness of zoom and focus is reduced.

The present invention has been made in view of the problems of the prior art as described above, and adopts a VC type linear motor as a drive source of the movable lens group and moves the drive center of the VC type linear motor. The objective is to align the optical axis of the lens group with the optical axis of the lens group, to accurately align the central axis of the drive with the optical axis, and to firmly fix the VC type linear motor.

[0007]

In order to achieve the above object, a lens barrel for a camera of 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, the movable lens group is attached to a mover of the voice coil type linear motor, and the voice coil type linear motor is arranged so that a drive center axis of the voice coil type linear motor coincides with the optical axis. In the lens barrel for a camera in which the yoke is fixed to the lens barrel, positioning concave and convex portions are formed on each of the yoke and the lens barrel so that the drive center axis of the voice coil type linear motor matches the optical axis. Forming a temporary fixing engagement portion on each of the yoke and the lens barrel for temporarily fixing the yoke to the lens barrel when assembling the yoke to the lens barrel Rutotomoni, is characterized in that fixed in the mechanical fastening means and said barrel and said yoke.

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

[0009]

The voice coil type linear motor is a linear motor including 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 the coil is wound. This is a DC motor, and by moving the coil current direction, the mover is moved forward and backward along the center yoke.

The movable lens group is attached to the movable element 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 and the optical axis coincide with each other, and this thrust is directly transmitted from the linear motor to the movable lens group. The center of the lens group does not deviate 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 irregularities are formed on each of the yoke and the barrel, the drive center axis and the optical axis of the voice coil type linear motor are accurately aligned. Can be made.

When assembling the yoke to the lens barrel, the temporary fixing engagement portions for temporarily fixing the yoke to the lens barrel are formed on the yoke and the lens barrel, respectively, so that the assembling work is extremely easy. Can be done.

Moreover, the yoke and the lens barrel are constituted by screws screwed in the optical axis direction or non-parallel to the optical axis, or mechanical fastening means such as crimping a protrusion 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]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view showing an overall configuration of a lens barrel according to an embodiment of the present invention, FIG. 2A is a view taken in the direction of arrow A shown in FIG. 1, and FIG. It is sectional drawing which follows the BB line.

As shown in FIG. 1, the lens barrel according to the present embodiment has a first lens group 1, a second lens group 2, a third lens group 3, and a third lens group in order along an optical axis II '. 4th lens group 4
And a CCD (charge couple device, not shown) as an image pickup device is provided at the focal position of the fourth lens group 4.

The first lens group 1 is a focusing level lens group,
It is composed of a plurality of lenses, for example, three lenses, and is fixed in the main lens barrel 5. The second lens group 2 is a zoom (variable magnification) lens group, is composed of a plurality of lenses, for example, three, and is supported by the two guide shafts 6 and 7 and the optical axis. It is provided so as to be movable along the II 'direction.

The third lens group 3 is a correction lens group,
It is composed of a single lens or a plurality of lenses, for example, one lens, and is fixed in the rear barrel 8. Further, the fourth lens group 4 is a focusing lens group, and a plurality of lenses,
For example, it is composed of two sheets, and is provided so as to be movable along the optical axis II ′. Further, an iris 9 is provided between the fixed first lens group 1 and third lens group 3 while being sandwiched between the main lens barrel 5 and the rear lens barrel 8, and the iris motor is provided. The iris 9 is driven up and down by 10. “11” is a stepping motor which is fixed to the main barrel 5 and moves the second lens group 2.

In the lens barrel of this embodiment, as a drive source for the fourth lens group 4, which is supported by the two guide shafts 12 and 13 and is movable along the optical axis II 'direction. ,
A voice coil type linear motor 18 is adopted.

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

On the other hand, the movable element 15 to which the fourth lens group 4 is attached is inserted into the lens holder of the third lens group 3 and is installed between the main lens barrel 5 and the rear lens barrel 8. It is supported by the guide shafts 12 and 13 and is slidable along the optical axis I-I '. As shown in FIG. 2B, the mover 15 is inserted into the center yoke 17b with a slight gap, and the current direction of the coil 14 wound around the outer periphery is switched, whereby the mover 15, that is, the fourth mover. The group lens 4 can be moved forward and backward along the center yoke 17b.

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

In order to accurately match the drive center axis of the VC type linear motor 18 and the optical axis II 'in this way, the following structure is adopted as the mounting structure of the VC type linear motor in this embodiment. There is.

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

In the embodiment shown in FIGS. 2A and 2B, the left side of the positioning recess of the back yoke 17a (see FIG. 2A).
The positioning recessed portion 19a (see (1)) is formed with high accuracy, and the right positioning recessed portion 19b is formed as an elongated hole so as to absorb the molding tolerance of the positioning protruding portion 20 formed on the rear barrel 8. Then, the positioning projection 20 formed on the rear lens barrel 8
Is fitted into the positioning recess 19a on the left side, the assembling accuracy of the yoke 17 and the rear lens barrel 8 is secured.

Further, the yoke 17 and the rear lens barrel 8 are different from the rear lens barrel 8 with respect to the tap 21 cut in the back yoke 17a.
Tighten the screw 22 from the bottom 8a side of the back yoke 1
7a is attached by pulling it in close contact with the bottom surface 8a of the rear barrel 8.

In this case, it is desirable to determine the mounting position of the screw 22 by utilizing the dead space of the yoke 17 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 formed in response to such a request.
Is located almost at the end of the back yoke 17a, and 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.

Since the back yoke 17a and the rear lens barrel 8 are fixed by the screws 22 in this manner, the mounting strength of the VC type linear motor is increased, and the stability and reliability of the lens barrel can be improved. . Moreover, in the screw 22 of this embodiment, the back yoke 17a is attached to the bottom surface 8a of the rear barrel 8.
Since it functions as a pull screw that adheres to the 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 lens barrel 8 when tightening the screw 22 described above. That is, the dowel (temporary fixed engaging portion) 24 is formed on the side surface of the back yoke 17a, and the engaging hole (temporary fixed engaging portion) 25 that engages with the dowel 24 is formed on the side surface of the rear barrel 8. (See FIG. 1 and FIG. 2B). Dowel 24 and engagement hole 2 in this case
The positional relationship with 5 does not need to be formed so accurately, and it is sufficient that the yoke 17 is temporarily fixed at least when the yoke 17 is screwed to the rear barrel 8.
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 fixing engaging portions 24 and 25 are formed on the yoke 17 and the rear lens barrel 8, respectively, the work for screwing the yoke can be performed very easily.

The present invention is not limited to the above-mentioned embodiments and can be modified in various ways. 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 adopted as a mechanical fastening means for assembling the yoke 17 and the rear lens barrel 8. In this case, the projection 2 is formed on the inner surface of the rear barrel 8.
7 is formed, 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 protrusion 27 is inserted into the through hole 28 and positioned. Then, the tips of the protrusions 27 are crushed by, for example, ultrasonic welding to carry out caulking.

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

Further, when the mechanical fastening means in the present invention is constituted by a screw, even if the function of the pull screw is not added as shown in FIG. 2, the screw 29 as shown in FIG. 4 is used.
May be tightened from the side surface of the rear lens barrel 8.
However, in this case, the dowel 24 formed on the yoke 17
It is necessary to make the positional relationship between the and the engagement hole 25 formed in the rear barrel 8 accurate.

It should be noted that the embodiments described above are described for facilitating the understanding of the present invention, and not for limiting the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design changes and equivalents within 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 irregularities are formed on each of the yoke and the lens barrel, the drive center axis and the optical axis of the voice coil type linear motor are accurately aligned. Can be made.

Further, 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 the yoke and the lens barrel respectively, so that the assembling work is extremely easy. Can be done.

Moreover, the yoke and the lens barrel are constituted by a screw that is screwed in the optical axis direction or non-parallel to the optical axis, or a mechanical fastening means such as crimping a protrusion 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 drawings]

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

2A is a view as seen from an arrow A 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 Codes] II '... Optical axis 4 ... Fourth group lens (movable lens group) 8 ... Rear lens barrel 15 ... Mover 17 ... Yoke 18 ... Voice coil type linear motors 19a, 19b ... Positioning recess 20 ... Positioning projections 22, 29 ... Screws (mechanical fastening means) 24 ... Dowels (temporary fixed engagement portions) 25 ... Through holes (temporary fixed engagement portions) 27 ... Protrusions (mechanical fastening means) 28 ... Through holes (machine (Fastening means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G03B 13/34 9119-2K G02B 7/11 P 7316-2K G03B 3/10

Claims (4)

[Claims] 1. 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 lens barrel for a camera in which a yoke of the voice coil type linear motor is fixed to a lens barrel so that the drive center axis of the voice coil type linear motor is aligned with the optical axis. A positioning uneven portion is formed on each of the yoke and the lens barrel so that the drive center axis of the yoke matches the optical axis, and the yoke is temporarily fixed to the lens barrel when the yoke is assembled to the lens barrel. A temporary fixing engagement portion is formed on each of the yoke and the lens barrel, and the yoke and the lens barrel are fixed 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 that is screwed along the optical axis direction and fastens the back yoke and the bottom surface of the lens barrel. Lens barrel. 3. The mechanical fastening means is characterized in that the protrusion formed on the lens barrel is inserted into a through hole formed in the back yoke, and then the protrusion is caulked. The lens barrel for a camera described in. 4. 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. The lens barrel for a camera described in.