JPH0836125A - Driving device for optical member - Google Patents

Abstract

PURPOSE:To provide the driving device for an optical member constituted so that a problem that the external form thereof is made large-sized or a projecting part is formed is not caused even when a lens group requires a large stroke and provided with simple structure. CONSTITUTION:This device is provided with a voice coil motor 17 arranged by being surrounded by a fixed frame 13 and constituted so that a relatively movable CCD holder 14 with respect to the frame 13 is arranged movably along an optical axis O by being driven by electromagnetic induction, a CCD 55 fixed to the holder 14 and a four-group lens 31 arranged to be fixed in a space surrounded by the frame 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical member driving device,
More specifically, the present invention relates to an optical member driving device that drives an optical member forward and backward by an electromagnetic actuator.

[0002]

2. Description of the Related Art Conventionally, an electromagnetic actuator having a coil and a magnet has been widely used as an actuator for focus zoom in a lens barrel of a video camera or the like. The camera lens barrel disclosed in JP-A-4-25811 is an example in which a voice coil motor is applied as an electromagnetic actuator. This lens barrel has a movable lens frame of an optical member holding frame suspended on a shaft, a coil is arranged on the outer periphery of the movable lens frame, and a magnet yoke portion is arranged inside the outer frame so as to face the coil. In comparison with the conventional lens barrel, the outer shape does not have a protruding portion, and a moment that tilts the lens optical axis is not generated.

On the other hand, one of the selling points of video cameras in the market in recent years is zoom magnification. Currently, the mainstream zoom magnification is 10 times,
Doubling is becoming more common.

[0004]

Generally, as the zoom becomes higher in magnification, the stroke S as an AF stroke indicating the total stroke amount of the focus lens during AF (autofocus) operation increases. . The stroke S
In general, when the focal length f is the subject close distance L, the following relationship holds. That is, S = f ² / L (1) For example, when the subject distance L is 1 m with a lens having a focal length f of 5 to 60 mm and a zoom magnification of 12 times,
The stroke S is about 3.6 mm.

Under the above zoom magnification conditions, the subject distance L =
At 0.7 m, the AF stroke S is about 5.1 mm. Therefore, as the zoom ratio increases, the AF stroke increases and interference with other components becomes a problem. This problem also occurs in the lens barrel for a camera disclosed in Japanese Patent Laid-Open No. 4-25811.

In order to prevent the interference, it is necessary to have an optical design in consideration of the voice coil motor in advance, or to arrange the voice coil motor so as to project outside.
In the former case, the overall length of the lens barrel becomes long, and in the latter case, the lens barrel has a protruding portion.

The present invention has been made in order to solve the above-mentioned problems, and even if a large stroke of the optical member is required, the outer shape of the device is increased, or It is an object of the present invention to provide an optical member driving device having a simple structure without causing a problem such as a protruding portion.

[0008]

In the optical member driving device of the present invention, a movable portion which is arranged surrounded by a fixed portion and which is driven by electromagnetic induction and is movable relative to the fixed portion is an optical axis. An electromagnetic actuator movably arranged along the movable part, a first optical member fixed to the movable part, and a second optical member fixedly arranged in a space surrounded by the fixed part. Is characterized by.

The optical member driving device drives the first optical member fixed to the movable portion by the electromagnetic actuator arranged in the fixed portion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are a vertical cross-sectional view of a lens barrel to which an optical member driving device according to an embodiment of the present invention is applied and an exploded perspective view around the lens barrel driving device.

The lens barrel is a four-lens zoom lens barrel. For zooming with this lens barrel, the lead screw 29b is rotated by using the stepper 29a shown in FIG. Focusing is performed by moving the group forward and backward, and focusing is performed by the CCD 55, which is an image sensor.
Is carried out by moving the CCD holder 14 holding C. The zooming drive source may be a DC motor.

The structure of the lens barrel will be described. The lens barrel mainly holds the first lens group 22 and is attached to a fixed frame 28 fixed to the fixed frame 13 on the camera side. And guide shafts 23a, 23b for supporting the second group frame 24 and the CCD holder 14 so that they can move back and forth.
A second group holding frame 24 that is a lens frame that holds the second group lens 25 and is supported by the guide shaft and is movable back and forth; an iris portion 26 attached to a fixed frame 28; and a third group lens 3
3 group holding frame 2 which holds 0 and is attached to the fixed frame 28
7 and the fourth group lens 31 which is the second optical member,
A movable group which holds the fourth group holding frame 32 fixed to the fixed frame 13 inside the yoke 12 and the CCD 55 which is the image pickup element of the first optical member and is supported by the guide shafts 23a and 23b. And the inner frame of the CCD
It is composed of a holder l4.

An LED 61 (see FIG. 2) which is a light emitting element for position detection, a coil for speed detection (not shown), and an LPF 54 are attached to the CCD holder 14.
Further, a coil portion 14b of the voice coil motor 17 is arranged on the outer peripheral portion in front of the CCD.

The yoke portion 12 of the voice coil motor 17
Is attached to the fixed portion 13 of the outer frame. A fourth group holding frame 32 is attached inside the center of the yoke, and a magnet 16 is attached at a position facing the coil portion 14b of the CCD holder 14. Fixed frame l3
A PSD 62 (see FIG. 2), which is a light receiving element, is arranged at a position facing the LED 61, and a speed sensor magnet (not shown) is arranged at a position facing the speed sensor.

As described above, the stroke S of the voice coil motor is determined by the formula (1) based on the zoom magnification (focal length f) and the subject close distance L. For example, 12
Double (focal length f5-60mm), when L = 0.7m,
The stroke S is 5.1 mm.

To obtain the stroke, the length of the yoke magnet (in the direction of the optical axis) L _M is at least L _M = S + α as shown in the sectional view of the voice coil motor in FIG. ……… (2) It is necessary to set. The value α is the width of the coil section cross section. Then, the thrust F of the actual voice coil motor 17 is _{F = I × B × L C} ......... (3). It should be noted that I is the current of the motor, B is the magnetic flux density, and L _C is the coil length.

In order to suppress the current I, the magnetic flux density B and
The thrust is earned with the coil length L _C. Therefore, here, the stroke S and the coil portion cross-section width α are S = α, and therefore the magnet length L _M is L _M = 2 × S. Then, an adjustment margin due to an assembly error is necessary, and considering that, and the margin value is β, L _M = 2 × S + β (see the action cross-sectional view of the voice coil motor in FIG. 3B). As an example, if a margin of about 0.5 mm is provided on each side, a yoke portion magnet length L _{M of} about 11 mm is required.

Here, the arrangement of the voice coil motor 17 will be described with reference to the arrangement diagram of FIG. FIG. 4A shows
Each lens group 22, 2 of the optical system of the lens barrel of the present embodiment
5, 30 and 31 and the arrangement of the CCD 55 are shown.
Reference numeral 5 is a first optical member, which is a movable portion for focus.

FIG. 4B shows one of possible arrangements of the voice coil motor. In this example, the magnet 1 is used.
6 is fixedly arranged behind the CCD 55, not on the side of the fourth group lens 31. In this case, the dimension of the lens barrel in the longitudinal direction becomes long. FIG. 4C shows another possible arrangement example of the voice coil motor, in which the magnet 16 is arranged along an axis different from the optical axis O of the optical system. In this case, the voice coil motor is arranged on the side of the lens barrel, and the outer shape of the lens barrel is projected.

FIG. 4D shows the arrangement of the voice coil motor of the lens barrel of the present embodiment. In this arrangement, the voice coil motor in front of the CCD 55 is fixed to the second optical member 4 which is fixed. The magnet 16 and the yoke 12 of the voice coil motor 17 are arranged on the side of the holding frame of the group lens 31 to prevent interference between the fourth group lens 3l and the yoke 16. Therefore, the fourth group lens 31 can be arranged inside the yoke 16, the length of the lens barrel can be suppressed to be short, the length of the lens barrel can be shortened, and the motor portion can project laterally. No, the lens barrel is compactly assembled. Since the deterioration of the optical performance of the fourth group lens 3l due to its eccentricity, inclination, etc. is small, the problem of the deterioration of the optical performance does not occur even if it is attached via the yoke 12 part.

As described above, in the lens barrel of this embodiment, the coil 14b is provided in the inner frame of the CCD holder 14 coaxial with the optical axis O of each lens group of the optical member, and the fourth group lens holding frame 32 is provided. The magnet 16 and the yoke 12 are arranged on the outer frame to form the voice coil motor 17, and the yoke 12
The fourth group lens 31 of a fixed optical member is arranged inside.

Therefore, according to the present embodiment, since a space can be provided in the depth direction of the yoke 12, even if the AF stroke S is increased by increasing the magnification, it does not interfere with other parts and is desired. AF stroke S, in other words,
Although the desired stroke of the voice coil motor can be obtained, the lens barrel can be prevented from being upsized, and the voice coil motor can be arranged in the lens barrel without deteriorating the optical performance.

The first optical member in the lens barrel of the above embodiment may be supported by the movable portion via another member. Further, in the lens barrel of the above embodiment, the CCD
Although the holder 14 is a focusing movable frame, as a modification thereof, a lens barrel having a similar arrangement of the yoke portion can be proposed even when the fourth group lens is a focusing movable frame. At this time, the third group lens is arranged inside the yoke. Further, the electromagnetic actuator may have a configuration other than the voice coil motor 17, and may be, for example, a motor having a configuration in which a coil portion is arranged on the fixed portion side.

(Appendix) According to the embodiment described above,
A camera lens barrel having the following configuration can be proposed. (1) A voice coil motor composed of an inner frame around which a coil is wound, a yoke, and an outer frame to which a magnet is fixed can be moved coaxially with the optical axis and parallel to the optical axis. A lens barrel for a camera, characterized in that a CCD is arranged in the inner frame, and an optical member is fixed in the outer frame.

According to the lens barrel for the present camera, the voice coil motor is arranged in a state where the space is effectively used for the CCD and the optical member, and the lens barrel can be compactly assembled.

[0026]

As described above, in the optical member driving device of the present invention, the first optical member is mounted on the movable portion driven by the electromagnetic actuator, and the second optical member is provided in the space surrounded by the fixed portion. Is arranged and the space in the depth direction is effectively used, so that, for example, even if the stroke of the first optical member increases, it does not interfere with other parts, and the external shape of the device is compact. Can be realized.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a lens barrel having a built-in optical member driving device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the lens barrel of FIG. 1 around a voice coil motor.

3A and 3B are cross-sectional views showing an operating state of the voice coil motor of the lens barrel of FIG. 1, wherein FIG. 3A shows a relationship between a coil width and a stroke, and FIG. 3B shows a stroke. And the width of the magnet.

FIG. 4 is a diagram showing an arrangement of each lens group and a voice coil motor of an optical system of a lens barrel of a similar example considered to be the lens barrel of FIG. 1, in which FIG. The arrangement of only the system is shown, (B) and (C) show the arrangement of the lens barrel and the voice coil motor of a possible similar example, and (D) shows the arrangement of the lens barrel of FIG. And the placement of the voice coil motor.

[Explanation of symbols]

13 …………………… Fixed frame (fixed part) 14 …………………… CCD holder (movable part) 17 …………………… Voice coil motor (electromagnetic actuator) 31 ……………… … 4th group lens (second optical member) 55 ……………… CCD (first optical member)

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G03B 13/34 G03B 3/10

Claims (1)

[Claims] 1. An electromagnetic actuator, which is surrounded by a fixed part and is driven by electromagnetic induction so as to be movable relative to the fixed part so as to be movable along an optical axis, and the movable part. A drive device for an optical member, comprising: a first optical member fixed to the first optical member; and a second optical member fixedly arranged in a space surrounded by the fixing portion.