JPH04293005A - Optical equipment - Google Patents

Abstract

PURPOSE:To offer the optical equipment having an improved linear electromagnetic motor type lens moving device which is reducible in size and weight and also reducible in cost. CONSTITUTION:When a driving circuit supplies a current to a coil 3, a force parallel to the optical axis is generated between yokes 8-10, and 11-13 by the cross-linkage between magnetic flux and the coil current, and consequently a lens holding frame 2 is moved axially to the position where the force of a spring 18 balances with the electromagnetic force. Similarly, when the driving circuit supplies the current to a coil 6, an electromagnetic force parallel to the optical axis operates on the coil 6 and a lens holding frame 5 is moved to the position where the electromagnetic force balances with the resistance force of a spring 19. The common yokes 9 and 12 are provided to the two lens frames 2 and 5, so the device can be prevented from increasing in size and cost.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device in which a lens is moved by the power generated by a driving source, and in particular,
The present invention relates to an optical device configured to move a lens in an axial direction using an axial driving force generated by electromagnetic induction.

0002

[Prior Art] Many modern optical devices such as cameras employ lens drive technologies such as autofocus and electric zoom. It is designed to be moved by the power generated by Most of the drive sources used in such conventional optical equipment are general-purpose small motors, which have low output and low torque at low speeds, so a reduction mechanism with a large reduction ratio is required. Since it is necessary to convert the rotational motion of the motor into linear motion, a screw mechanism is required.

[0003] Therefore, conventional optical equipment has problems in that the friction loss in the lens drive system is large, the transmission efficiency is low, and the processing and manufacturing costs of the reduction mechanism and screw mechanism are large.

Therefore, recently, a lens moving device has been proposed in which a drive source that does not require a speed reduction mechanism is provided in a lens holding frame and a fixed part, and the power generated by the drive source is directly applied to the lens holding frame. Among these developments is, for example, an interchangeable lens using a vibration wave motor, which has already been commercialized by the present applicant.

The present inventor has also already proposed a linear motor type lens moving device.

[0006]

[Problems to be Solved by the Invention] The linear motor type lens moving device already proposed by the present inventor has coils, permanent magnets, and yokes (joints) arranged on a plurality of different circular arcs centered on the optical axis of the lens. A type of linear motor capable of generating axial force is constructed by arranging the coils, permanent magnets, and yokes to overlap each other, and by integrating the coil, permanent magnet, or yoke with the lens holding frame, the lens holding frame is It is configured as a driven element of a linear motor.

In the linear electromagnetic motor type lens moving device proposed by the present inventors as described above, each lens holding frame is provided with its own dedicated coil, permanent magnet, and yoke set. Ta.

However, providing a dedicated coil, permanent magnet, and yoke for each lens holding frame increases the number of component parts, leading to an increase in size, weight, and cost of optical equipment such as cameras and lens barrels. There was a problem.

An object of the present invention is to solve the above-mentioned problems inherent in the devices already proposed by the present inventor, and to provide an improved optical device that can be made smaller and lighter, as well as cost-reduced. It is to be.

0010

[Means for Solving the Problems] In the present invention, a yoke is shared by at least two lens holding frames, thereby reducing size, weight, and cost.

[0011]

[Operation] In the embodiment shown in FIGS. 1 to 3, for example, when a current is passed through the coil 3 by a drive circuit (not shown), the magnetic flux and the coil current are interlinked in the gaps between the yokes 8 to 10 and 11 to 13. A force parallel to the optical axis is generated, and as a result, the lens holding frame 2 is moved in the axial direction to a position where the force of the spring 18 and the electromagnetic force are balanced.

Similarly, the coil 6 is driven by a drive circuit (not shown).
When a current is applied to the coil 6, an electromagnetic force parallel to the optical axis acts on the coil 6, and the lens holding frame 5 is moved to a position where the electromagnetic force and the resistance force of the spring 19 are balanced.

In the present invention, two lens holding frames 2 and 5 are provided.
Since common yokes 9 and 12 are provided for both, it is possible to prevent an increase in size and cost of the device compared to a conventional device (device proposed by the present inventor).

[0014]

[Embodiments] Examples of the present invention will be described below with reference to the drawings. 1 to 3 are diagrams showing a first embodiment of a lens barrel configured to apply the present invention. In FIGS. 1 and 2, 2 is a first lens holding frame that holds the lens 1. The rear part of the holding frame 2 is a small diameter part, and the rear end of the small diameter part has a conductive wire extending in the circumferential direction. A first coil 3 is carried thereon. Fixed (stationary) with a rear end plate so as to surround the small diameter portion of the first lens holding frame 2
A lens barrel 7 is arranged. Two cylindrical yokes 8 and 11 are fixed on the inner circumferential surface of the fixed lens barrel 7 on the same circular arc at positions 180 degrees apart from each other with respect to the axis of the lens barrel 7. 11 is arranged with a slight gap in the radial direction from the small diameter portion of the lens holding frame 2 and the outer peripheral surface of the coil 3, and extends a predetermined length in the circumferential direction as shown in FIG. 1(b). There is. Further, on the inner surface of the rear end plate 7a of the fixed lens barrel 7, there is a line along the inner peripheral surface of the small diameter portion of the lens holding frame 2 and the inner peripheral surface of the coil 3 at a position 180 degrees apart with respect to the axis of the lens barrel 7. Two cylindrical yokes 9 and 12 extending a predetermined length in the circumferential direction are fixed, and a cylindrical permanent magnet 14 that is in contact with the yokes 8 and 9, 11 and a cylindrical permanent magnet 16 in contact with the yoke 12;
is fixed. Further, two cylindrical yokes 10 and 13 are fixed to the inner surface of the rear end plate 7a of the lens barrel 7, and are arranged on the same arc at positions radially inner than the yokes 9 and 12. At the same time, a cylindrical permanent magnet 15 is fixed between the yokes 9 and 10 and is in contact with both yokes 9 and 10.
A cylindrical permanent magnet 17 that contacts both yokes 12 and 13 is fixed between them.

In the space inside the yokes 10 and 13, a second lens holding frame 5 holding a lens 4 is disposed so as to be movable in the axial direction, and the outer peripheral surfaces of the lens holding frame 5 are spaced 180 degrees apart from each other. Two protrusions 5a and 5b protrude radially outward at a single position (see (b) in FIG. 1).
A coil 6 is fitted on the outer peripheral surface of the lens holding frame 5, and the coil 6 is inserted into the gap between the yokes 9 and 10 and the gap between the yokes 12 and 13, and is movable in the axial direction together with the lens holding frame 5. It has become. An annular spring 18 whose both ends are fixed to the coil 3 and the permanent magnets 8 and 16 is arranged in the gap between the yokes 8 and 9, and the lens holding frame 2 and the coil 3 are moved by the spring 18. In FIG. 1(a), it is always urged toward the right (that is, toward the rear). In addition, the gap between the yoke 9 and the yoke 10 and the yoke 1
An annular spring 19 is also housed in the gap between the yoke 13 and the yoke 13, and the front end of the spring 19 is fixed to the coil 6.
The rear end of lens 9 is fixed to permanent magnets 15 and 17, and the spring 19 always urges lens holding frame 5 and coil 6 to the right (ie, backward) in FIG. 1(a).

The permanent magnets 14 to 16 have polarities as shown in FIG. Magnetic flux is generated.

In the embodiment shown in FIGS. 1 to 3, for example, when a current is passed through the coil 3 by a drive circuit (not shown), the magnetic flux and the coil current are interlinked between the yokes 8 to 10 and 11 to 13. A force parallel to the optical axis is generated, and as a result, the lens holding frame 2 is moved in the axial direction to a position where the force of the spring 18 and the electromagnetic force are balanced.

Similarly, the coil 6 is driven by a drive circuit (not shown).
When a current is applied to the coil 6, an electromagnetic force parallel to the optical axis acts on the coil 6, and the lens holding frame 5 is moved to a position where the electromagnetic force and the resistance force of the spring 19 are balanced.

In the present invention, two lens holding frames 2 and 5 are used.
Since common yokes 9 and 12 are provided for both, it is possible to prevent an increase in size and cost of the device compared to a conventional device (device proposed by the present inventor).

FIGS. 4 and 5 show a second embodiment of the present invention. In the figure, 30 is the first lens, 31
holds the lens 30 and is movable parallel to the optical axis.
A lens holding frame 32 indicates two points on the outer periphery of the first lens holding frame 31.
33 is a second lens; 34 is a second lens holding frame that can hold the second lens 33 and move parallel to the optical axis; 35 is a second lens holding frame A coil fitted on the outer peripheral surface of 34, 36 a fixed cylinder,
37 is a front end plate fixed to the front end of the fixed cylinder 36, 38 is a rear end plate fixed to the rear end of the fixed cylinder 36, and 39 is fitted to the inner peripheral surface of the fixed cylinder 36, and the coil 32 and 35
A cylindrical yoke 40 and 42 are supported by the front end plate 37 and the rear end plate 38, and a cylindrical yoke is arranged on the inner peripheral side of the coils 32 and 35. 42 is fixed to the rear end plate 38 and the yoke 3
9 and a permanent magnet 44 disposed between the yoke 40 and the yoke 40;
46 is a permanent magnet fixed to the rear end plate 38 and sandwiched between yokes 41 and 42; 46 is a coil whose front end is fixed to the coil 35 and whose rear end is fixed to permanent magnets 43 and 44; An annular spring 45 has its front end fixed to the front end plate 37 and its rear end fixed to the coil 32 to bias the coil 32 and the lens holding frame 31 rearward. This is an annular spring that urges the

The permanent magnets 43 and 44 are polarized as shown in FIG. 5, and the magnetic flux in the gap between the yokes 39 and 40 and the gap between the yokes 41 and 42 is the same as that of the fixed cylinder as shown in the figure. The direction is radial.

As shown in FIG. 4, in this embodiment, the yokes 39 to 42 are common to the two lens holding frames 31 and 34, so this is easier than providing separate yokes for each lens holding frame. The entire lens barrel can be made smaller and lighter.

When a current is applied to the coil 32 by a drive circuit (not shown), an axial force acts on the lens holding frame 31 due to the electromagnetic force generated by the interlinkage between the magnetic flux between each yoke and the coil current, and the spring 45 The lens holding frame 31 is moved to a position where the resistance force and the driving force are balanced. Similarly, when current flows through the coil 35, the lens holding frame 34 is driven in the axial direction by the electromagnetic force caused by the interlinkage between the magnetic flux between each yoke and the coil current, and the lens holding frame 34 is moved to a position where the electromagnetic force and the resistance force of the spring 46 are balanced. The lens holding frame 34 is moved until.

FIGS. 6 and 7 show a third embodiment of the present invention. In this embodiment, a permanent magnet is attached to each lens holding frame, and a coil for each lens holding frame is fixed. It is fixed to the cylinder together with the yoke.

In FIG. 6, 50 is a first lens, 51
52 is a first coil fitted around the outer periphery of the lens holding frame 51; 53 is a second lens; and 54 is a lens 53. a second lens holding frame 55 that can hold and move parallel to the optical axis;
56 is a fixed cylinder, 57 is a cylindrical yoke fitted to the inner periphery of the fixed cylinder 56, and 58 and 59 are coils fitted to the inner periphery of the yoke 57. In this embodiment, the yoke 57 is common to the lens holding frames 51 and 54, which is the same as in the first embodiment, but the coil is fixed to the yoke, which is a stationary member, and the magnet is fixed to the lens, which is a moving member. Since it is attached to the holding frame, the structure is simpler in terms of electrical wiring than the structure of the first embodiment, and there is less risk of failure.

FIG. 7 shows the polarity of the permanent magnets 52 and 55 and the direction of magnetic flux in the gap between the magnets and the yoke 57.

In the configuration of FIG. 6, coils 58 and 59
When a current is applied to the lens holding frames 51 and 54, an electromagnetic force in the axial direction acts on the lens holding frames 51 and 54 due to the interaction between the current and the magnetic flux (based on Fleming's left hand rule), and the lens holding frames 51 and 54 move toward the optical axis. be moved along.

[0028]

[Effects of the Invention] As explained above, in the optical device of the present invention, since a common yoke is provided for a plurality of lens holding frames, the optical device can be made smaller and lighter than conventional devices of the same type. This also makes it possible to reduce costs.

[Brief explanation of the drawing]

FIG. 1(a) is a longitudinal cross-sectional view of a first embodiment of an optical instrument according to the present invention, and FIG. 1(b) is a cross-sectional view taken along the line II-II in FIG. 1(a).

FIG. 2 is an exploded perspective view of the device shown in FIG. 1.

FIG. 3 is an enlarged view of the magnet and yoke of the device shown in FIGS. 1 and 2;

FIG. 4(a) is a longitudinal sectional view of an optical device according to a second embodiment of the present invention. (b) is a sectional view taken along the line bb in FIG. 4(a).

FIG. 5 is a longitudinal sectional view showing a magnet and a yoke of the device shown in FIG. 4;

FIG. 6(a) is a longitudinal sectional view of an optical device according to a third embodiment of the present invention. (b) is a sectional view taken along the line bb in FIG. 6(a).

FIG. 7 is a schematic diagram showing a magnet and a yoke of the device shown in FIG. 6;

[Explanation of symbols]

1, 4, 30, 33, 50, 53; camera body 2, 5,
31, 34, 51, 54; Lens holding frame 14-17, 4
2, 43, 52, 55; permanent magnet 3, 6, 32, 35,
58, 59; Coils 8-13, 39-42, 57; Yoke 7, 36, 56; Fixed lens barrel 18, 19, 45, 46; Spring

Claims (1)

[Claims] 1. A plurality of lens holding frames capable of holding lenses and movable along the optical axis of the lenses, and a plurality of lens holding frames arranged around the optical axis so as to generate a moving force in the optical axis direction by electromagnetic induction in the lens holding frames. What is claimed is: 1. An optical device comprising a coil, a permanent magnet, and a yoke concentrically arranged as a yoke, wherein a common yoke is provided for at least two of the lens holding frames.