JPH11289743A - Linear actuator and lens driving device and lens barrel using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens driving device which has a superior vibrating characteristic and is capable of making driving parts to be used commonly, coping with wide specification ranges that have weight differences between mobile lens groups without increasing the size of a lens barrel. SOLUTION: A magnetic circuit 33 which is constituted of a magnet and a yoke and has a nearly symmetrical shape, with respect to the center line is provided in the direction in which the directions of magnetization of magnets face opposite to each other, and a coil 8 is provided to a focus lens holder 1 formed integrally with a sleeve 9 which can be slid along a guide shaft positioned in parallel with the optional axis. In addition, a magnetic sensor 10 is provided horizontally on a lens barrel 3b at a prescribed distance from the side face of the magnet. Moreover, a magnetic scale 11 is provided to the focus lens holder 1, in such a way that the scale 11 facing opposite to the detecting surface of the magnetic sensor 10, and the sleeve 9 is positioned close to the coil 8 and magnetic scale 11, so that the center of gravity of a mobile section is positioned near the driving center 13 of the coil 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear actuator, and more particularly to a lens driving device for driving a photographing lens in an imaging device such as a camera and a video camera, and a lens barrel.

[0002]

2. Description of the Related Art In recent years, the technology of video cameras has been remarkably advanced, and many performance improvements have been made in various fields such as digital recording, miniaturization, lightening, long shooting, high speed, and high magnification zoom. In the lens barrel that is the image pickup unit, the so-called “inner focus method” in which the focus adjustment is performed by changing the position of the focus lens group behind the zoom lens group in the optical axis direction is achieved by reducing the size and weight. Because of its advantage that it is widely used at present and the focus plane moves at the zoom magnification, the focus lens group is generally used based on the movement trajectory data for each subject distance stored in the microcomputer. It moves in the direction of the optical axis in accordance with a change in the position of the lens group, and forms an object image on the imaging plane of the image sensor at the rear of the lens barrel.

[0003] In view of the characteristic of the movement trajectory data that the amount of movement of the focus surface on the telephoto side is large, to move the focus lens group so as to follow the zoom lens group, focus near the telephoto side rather than the zoom lens group. It is necessary to move the lens group quickly, and among the above items of performance improvement,
In order to realize high-speed zooming and long-time shooting, the driving part of this focus lens group is excellent in high-speed response and low power consumption that can follow the position change of the zoom lens group instead of the conventional stepping motor. A voice coil type linear actuator is employed.

As examples using this linear actuator, Japanese Patent Application Laid-Open Nos. 9-61692 and 9-12 are known.
In the lens driving device described in Japanese Patent No. 7397, a rod magnet made of a rod-shaped magnetic body and a magnet both ends of which are supported in the optical axis direction by a yoke, and a movable coil wound around a bobbin sliding along the bar magnet And a connecting means for holding the movable lens and connecting a movable lens holder along the guide means.

As another example, Japanese Patent Application Laid-Open No. H8-2482
In the lens driving device described in Japanese Patent Publication No. 90, a voice coil is provided around a lens holder that holds a focus lens and is slidable in the optical axis direction along a guide axis, and lenses on both sides of the voice coil. Focus lens driving means has been devised which includes a pair of yokes arranged on the lens barrel side and a pair of magnetic circuits composed of magnets joined and fixed to these yokes.

However, in the lens barrel using the lens driving device described in JP-A-9-61692 and JP-A-9-127397, the linear actuator can be formed separately from the lens barrel, so that the zoom magnification is increased. Also, the same linear actuator can be used for lens barrels with different optical performances, which means that the components of the driving means can be shared, but the linear actuator and lens holder are connected by a connecting member. In addition, there is a problem that a mechanical backlash is generated and the lens holder cannot be driven at a high speed, and a space for a connecting member in the lens barrel is required, so that the lens barrel cannot be downsized.

Further, in the lens driving device described in Japanese Patent Application Laid-Open No. 8-248290, since the voice coil is directly mounted around the lens holder, no rattling occurs, and the lens holder can be driven at high speed. However, if the size of the focus lens changes, the size of the voice coil needs to be changed, and it is necessary to provide a linear actuator corresponding to a lens barrel having different zoom magnification and optical performance. There was a problem that it could not be achieved. Furthermore, since it is necessary to provide a sleeve fitted on the guide shaft outside the voice coil and a magnetic scale opposed to a magnetic sensor provided on the lens barrel which is a position detecting means of the lens holder, the lens barrel is small. There was also a disadvantage that it was difficult to achieve the formation.

In order to solve the above-mentioned problems of the lens barrel, a lens driving device and a lens barrel described in Japanese Patent Application No. 09-314954 have been devised. The lens driving device and the lens barrel described in Japanese Patent Application No. 09-314954 are provided with a single magnetic circuit having a magnet and a yoke in the lens barrel and having a substantially symmetrical shape as viewed in the driving direction. A sleeve that fits with the guide shaft is formed integrally with the lens holder so that the lens holder that holds the movable lens group is slidable in the optical axis direction along the guide shaft, and the coil is movable near the sleeve. It is located away from the lens group.

Further, as a position detecting means, a magnetic sensor is formed by using the technology shown in the linear actuator described in Japanese Patent Application No. 09-31765 so as to minimize the influence of magnetic flux leakage from the magnetic circuit. At the center of symmetry, the direction of current of the MR element is substantially perpendicular to the magnetization direction of the magnet, and the magnetic scale is disposed on the lens barrel. It is arranged on the holder. Therefore, the coil, the sleeve, the magnetic scale, and the magnetic sensor are arranged in a straight line in the magnetization direction of the magnet.

Further, the center of gravity of a lens driving body composed of a moving lens group, a lens holder, a coil and a magnetic scale is arranged near the coil. As described above, in the lens driving device and the lens barrel described in Japanese Patent Application No. 09-314954, the linear actuator of the driving means is built in the lens barrel so as to be provided horizontally with the movable lens, and the lens holder is directly driven. At the same time, the distance between the drive center point, the position detection point, the sleeve, and the center of gravity is configured to be small in order to improve control responsiveness.
It has features that are superior to those of the related art, such as being capable of high-speed and high-precision lens driving, downsizing of a lens barrel, and common use of driving components.

[0011]

However, the lens driving device and the lens barrel described in Japanese Patent Application No. 09-314954 described above have a lens holder sleeve and a movable lens group so that the lens holder does not interfere with the magnetic circuit. Since some gaps need to be cut out, the rigidity of the lens holder decreases, and resonance tends to occur in the low-frequency range. It becomes.

Further, when two types of lens barrels in which the number of lenses constituting the movable lens group is different, that is, there is a large difference in the weight of the movable lens group, the components of the magnetic circuit and the coil are shared. It is necessary to increase the width of the magnetic circuit and the coil to generate thrust according to the heavier movable lens group.
Because the movable lens group is placed laterally on the magnetic circuit and the coil, it is directly connected to the increase in the size of the lens barrel in the height direction,
The size of the lens barrel having one movable lens group is unnecessarily increased. Therefore, it is difficult to share drive components in a wide range of lens specifications without increasing the lens barrel size.

In view of the above problems, it is an object of the present invention to provide a lens drive apparatus and a lens barrel described in Japanese Patent Application No. 09-314954, which do not impair the advantages of the lens drive apparatus, and which further have excellent vibration characteristics and a large lens barrel size. Instead, the present invention provides a lens driving device with a simple configuration that can share driving components in a wide range of lens specifications where the weight of the movable lens group is different.

[0014]

In order to solve the above-mentioned problems, a linear actuator according to the present invention drives a magnetic sensor in a single magnetic circuit composed of a magnet and a yoke which are substantially symmetrical when viewed from the driving direction. Seen from the direction,
By horizontally arranging the magnet at a predetermined distance from the side surface of the magnet, a leakage magnetic flux perpendicular to the magnetization direction of the magnet that jumps into the magnetic sensor when viewed from the driving direction can be reduced.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION
A magnet and a yoke magnetized perpendicular to the driving direction are provided.The stator has a magnetic circuit formed substantially symmetrically as viewed from the driving direction.The magnet has a predetermined gap, and a magnetic flux generated by the magnet. In a linear actuator having first driving means having a coil movable in a driving direction as a mover by passing a current perpendicularly, a magnetic sensor is provided on one of the mover side and the stator side. A first position detecting means, which is provided laterally at a predetermined distance from the side surface of the magnet when viewed from the driving direction, and on the other side, a magnetic scale is disposed so as to face a detection surface of the magnetic sensor. .

According to a second aspect of the present invention, the magnetic sensor is a magnetoresistive sensor using an MR element, and a direction of a current flowing through the MR element is substantially perpendicular to a magnetization direction of the magnet. The magnetic sensor is arranged so as to be as follows. According to a third aspect of the present invention, there is provided a lens driving apparatus for forming an object image on an image forming plane by an optical system including a moving lens group, wherein the magnet drive is provided as a means for driving the moving lens group. A linear actuator according to claim 1 or 2, wherein a magnetic surface is disposed in a direction facing the moving lens group.

According to a fourth aspect of the present invention, a guide means for guiding the moving lens group to move in the optical axis direction, and the moving lens group is held and fitted with the guide means. In a lens driving device having a lens holding means provided with a sleeve, the sleeve is arranged close to the first driving means and the first position detecting means when viewed from the optical axis direction. Things.

According to a fifth aspect of the present invention, as viewed from the optical axis direction, a straight line connecting the sleeve and the drive point of the first drive means, the sleeve and the first position detection means are provided. And a straight line connecting the detection points intersects at a substantially right angle. The invention according to claim 6 of the present invention includes the moving lens group, the lens holding unit, the first driving unit, and the first position detecting unit, as viewed from the optical axis direction. Position of the center of gravity of the lens driver
It is characterized by being arranged near the first driving means.

According to a seventh aspect of the present invention, the guide means for guiding the moving lens group to move in the optical axis direction, the moving lens group is held, and the guide means is fitted. In the lens driving device having the lens holding means provided with the sleeve, the sleeve is laterally provided on the second driving means and the second position detecting means when viewed from the optical axis direction, and the sleeve and the A straight line connecting the drive point of the second drive unit and a straight line connecting the sleeve and the detection point of the second position detection unit intersect at a substantially right angle.

According to an eighth aspect of the present invention, when viewed from the optical axis direction, the lens center of the movable lens group, the sleeve, and the detection point of the second position detecting means are substantially in a straight line. It is characterized by being arranged in. Less than,
Embodiments of a lens driving device and a lens barrel using the linear actuator of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing a front side of a rear barrel portion of a lens barrel using a linear actuator according to an embodiment of the present invention, and FIG. 2 is a linear actuator according to an embodiment of the present invention. FIG. 3 is a longitudinal sectional view of a main part showing an internal configuration of a lens barrel using a lens, FIG. 3 is an internal perspective view of a focus lens driving portion of a lens barrel using a linear actuator according to an embodiment of the present invention, and FIG. FIG. 5 is a view showing a flow of magnetic flux in a longitudinal section of a focus lens driving portion of a lens barrel using a linear actuator according to the embodiment of the present invention. FIG. 5 is a view showing a focus lens of a lens barrel using a linear actuator according to an embodiment of the present invention. FIG. 6 is a diagram showing a flow of magnetic flux in a cross section of a driving portion, FIG. 6 is a diagram showing a magnetoresistance change rate characteristic of an MR element, and FIG. 7 is a schematic perspective view of a position detecting means. .

A lens barrel using a linear actuator according to an embodiment of the present invention includes an electric zoom mechanism for changing magnification, an automatic aperture device for reproducing a subject with an appropriate exposure,
It is a lens barrel for a general video camera of the inner focus type having an autofocus mechanism for automatically performing focusing on a subject. Therefore, this lens barrel is composed of two fixed lens groups, one fixed lens group on the subject side and the third fixed lens group in the lens barrel, a variator lens group for zooming and the like, and a focus lens group for focus adjustment. It is composed of two moving lens groups and a diaphragm device.

First, a lens barrel using a linear actuator according to an embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. 1 and 2, reference numeral 3a denotes a front part of the lens barrel, 3b denotes a rear part of the lens barrel, and 23 denotes a first-group fixed lens group fixed to the subject side of the lens barrel 3a.
2 is a variator lens group for zooming or the like, 2 is a focus lens group for focus adjustment, 27 is located between the variator lens group 22 and the focus lens group 2, and is fixed between the lens barrels 3a and 3b. 3 fixed lens groups, 2
Reference numeral 4 denotes a diaphragm main body provided in front of the third group fixed lens group 27, 30 denotes a solid-state imaging device such as a CCD, and 31 denotes a C for attaching the solid-state imaging device 30 to a rear portion of the lens barrel 3b.
The CD mounting plate 29 is placed in front of the solid-state imaging device 30,
This is an optical filter made of quartz or the like.

A variator lens group 22 and a focus lens group 2 are held by a variator lens holder 21 and a focus lens holder 1, respectively, are arranged parallel to the optical axis, and are fixed at both ends to lens barrels 3a and 3b. It is configured to be independently slidable along the optical axis along each of 4a and 4b. Variator lens group 22
Must move in a wide range from the telephoto end to the wide-angle side in conjunction with the focus lens. Therefore, the drive source for driving the variator lens holder 21 has high controllability and needs to count the number of input pulses. In general, a stepping motor having the function of an encoder is generally used as the zoom motor 15.

The variator lens driving means includes a zoom motor 15 as a driving source, a bracket 16 to which the zoom motor 15 is assembled, and an output shaft of the zoom motor 15, which is rotatably supported by the bracket 16. A feed screw 18 having a length dimension of a moving range of the variator lens, and a rack 19 which engages with the feed screw and converts a rotary motion into a linear motion;
The zoom motor 15 is fixed to the lens barrel 3 a via a bracket 16, and the rack 19 is fixed to a variator lens holder 21. Therefore, with this configuration, the variator lens holder 21 can be arbitrarily moved according to the number of steps of the zoom motor 15.

For detecting the reference position of the variator lens 22, a photo-interrupter 28 composed of a light-emitting element (not shown) such as an LED and a light-receiving element (not shown) such as a phototransistor passes between them and blocks light. A variance holder 21 is provided with a position detection piece (not shown) integrally formed, and moves the variator lens group 22 to the photointerrupter 28 when the power is turned on.
This position is set as a reference position, and a movement position from this position is managed as the number of steps of the zoom motor 15 to calculate a starting position.

The aperture unit extracts an average value or a peak value of a video signal output in order to reproduce a subject with an appropriate exposure, and a plurality of aperture blades (not shown) so as to obtain an appropriate exposure. A diaphragm main body portion 24, which is constituted by a so-called auto iris that automatically adjusts the optical aperture of the lens barrel by driving the lens barrel, and stores a plurality of diaphragm blades (not shown);
An actuator (not shown) for driving the plurality of aperture blades (not shown) and an aperture drive control unit 25 having a built-in control unit (not shown) are provided. Aperture body 2
4 needs to accommodate a plurality of diaphragm blades (not shown) even in the case of the maximum optical aperture, and thus has an outer dimension substantially equal to the outermost dimension of the lens barrel 3a.
When a diaphragm unit is attached to the diaphragm drive control unit 2
5 protrudes.

Next, a focus lens driving means for a lens barrel using a linear actuator according to an embodiment of the present invention will be described with reference to FIGS. 1 and 3, a focus lens holder 1 holds a focus lens group 2 and is disposed parallel to an optical axis, and a guide shaft 4 having both ends fixed to lens barrels 3a and 3b.
The sleeve 9 is fitted with the sleeve 9a, and the rotation stopper is fitted with the guide 4b. The sleeve 9 is slidable in the optical axis direction along the guide shafts 4a and 4b.

In order to drive the lens holder 1 in the optical axis direction, a magnet 5 magnetized perpendicular to the driving direction
And a U-shaped main yoke 6 and a plate-shaped side yoke 7. The magnetic circuit is configured to be bilaterally symmetrical in the optical axis direction and substantially bilaterally symmetrical in the driving direction (X direction). Reference numeral 33 denotes a direction in which the magnetized surface of the magnet 5 faces the movable lens, and is provided on the lens barrel 3b.

On the other hand, in the focus lens holder 1, a coil 8 is provided transversely to the focus lens group 2 with a predetermined gap from the magnet 5, and a current is applied to the coil 8 in a direction orthogonal to the magnetic flux generated by the magnet 5. Is flowing, the focus lens holder 1 is driven in the optical axis direction. Further, as a position detecting means of the focus lens holder 1, a magnetic sensor 10 is provided on the lens barrel 3b.
Is provided laterally at the center of symmetry of the magnetic circuit 33 in the optical axis direction (X direction) and at a predetermined distance from the side surface of the magnet 5 when viewed from the optical axis direction. A magnetic scale 11 in which S poles and N poles are alternately magnetized at a predetermined pitch along a driving direction by moving a ferromagnetic material at a constant speed with respect to a magnetic head.
Are attached to face the detection surface of the magnetic sensor 10.

The magnetic sensor 10 is a two-phase magnetoresistive element composed of MR elements 32a and 32b made of a ferromagnetic thin film such as NiFe or NiCo having the characteristic that the resistance value changes according to the magnetic field shown in FIG. Type sensor, this MR element 3
The magnets 2a and 32b are provided in the driving direction (X direction) at an interval of 1/4 of the magnetization pitch between the S pole and the N pole of the magnetic scale 11, and the direction of the current flowing through the MR elements 32a and 32b is The magnetic sensor 10 and the magnetic scale 11 are disposed in a direction perpendicular to the magnetization direction of the magnetic sensor 10.

FIG. 6 shows the magnetoresistive change rate characteristics of the MR elements 32a and 32b in which the resistance value decreases when a magnetic field is applied.
The resistance value hardly changes with respect to a magnetic field perpendicular to the current direction of 2b and in the direction (Y direction) perpendicular to the detection surface, but is perpendicular to the current direction of the MR elements 32a and 32b and parallel to the detection surface. The resistance value greatly changes with respect to a magnetic field in an appropriate direction (X direction), and the resistance value slightly changes with a magnetic field in a direction (Z direction) parallel to the current direction of the MR elements 32a and 32b. With the characteristic.

From this characteristic, the focus lens holder 1
When the magnetic scale 11 moves and the position of the magnetic scale 11 changes with respect to the magnetic sensor 10, the resistance values of the MR elements 32a and 32b change in response to the sinusoidal magnetic field strength change generated in the X direction. Here, a sinusoidal magnetic field intensity change pattern having a 180 ° phase difference from the X direction also occurs in the Y direction, but the resistance values of the MR elements 32a and 32b hardly change due to the above characteristics. Therefore, the output signals of the voltages applied to the MR elements 33a and 33b become two sinusoidal waveforms having a phase difference of 90 °, and the two signal waveforms are subjected to modulation interpolation processing by a signal processing circuit (not shown). The position and the driving direction of the focus lens holder 1 are detected, and the focus lens group 2 is controlled by a control circuit (not shown) based on the movement trajectory data for each subject distance stored in a microcomputer (not shown) in advance. By moving in the optical axis direction in accordance with a change in the position of the variator lens group 22, the lens barrel 3 is moved.
b. An object image is formed on the image plane of the image sensor 30 provided at the rear.

The sleeve 9 is disposed close to the coil 8 and the magnetic scale 11 when viewed from the optical axis direction.
That is, the drive center point 12 (FIG. 1) and the position detection point 13 (FIG. 1) are located near the sleeve 9, and at the same time, the straight line connecting the sleeve 9 and the drive center point 12 of the coil 8 and the sleeve 9 and the magnetic scale 11 It is configured such that a straight line connecting the position detection points 13 intersects at a substantially right angle. Further, the focus lens group 2, the focus lens holder 1, and the coil 8
A center of gravity position 14 (FIG. 1) of the focus lens driving body composed of the magnetic scale 11 and the magnetic scale 11 is disposed near the coil 8.

The aperture drive control unit 25 of the aperture unit
Is disposed in an empty space on the subject side in front of the focus lens driving means, and the diaphragm main body 24 is connected to the guide shaft 4.
The lenses are arranged inside the guide shafts 4a and 4b so as not to interfere with the lens shafts 4a and 4b. Further, the zoom motor 15 is arranged at a position opposite to the aperture drive control section 25 with the optical axis interposed therebetween so as not to interfere with the aperture main body section 24, and the bracket 16 is attached to the lens barrel 3a.

The effects of the lens driving device and the lens barrel according to the embodiment of the present invention described above will be described. First, the magnetic circuit 33 including the coil 8 and the magnet 5 and the main yoke 6 and the side yoke 7 is not restricted by the size of the focus lens group 2.
Even for lens barrels with different zoom magnification and optical performance,
Japanese Patent Application Laid-Open No. H10-207,197, in which the same drive parts can be used, and the longitudinal direction of the horizontal width of the focus lens group 2 and the coil 8 is arranged in the height direction of the lens barrel 3b when viewed from the optical axis direction. Compared with the lens barrel described in JP-A-09-314954, in the lens barrel according to the embodiment of the present invention, the lengthwise direction of the width of the coil 8 and the sleeve 9 or the magnetic scale 1 are arranged in the width direction of the lens barrel 3b. Due to the configuration, there is room in the longitudinal direction of the width of the coil 8, and even when the focus lens group 2 is heavy with three lenses, the width of the magnetic circuit 33 and the coil 8 can be increased to increase the width of the lens barrel 3 b. The driving force corresponding to the weight of the focus lens group 2 can be increased without increasing the size. Therefore, the focus lens group 2
When sharing the components of the magnetic circuit 33 and the coil 8 for two types of lens barrels having a large difference in the weight of the focusing lens lens group 2, the magnetic lens 33 generates a thrust corresponding to the heavier focus lens lens group 2. Even if the horizontal width of the circuit 33 and the coil 8 is determined, the size of the lens barrel 3b does not increase, so that it is possible to flexibly share drive components in accordance with the specifications of a wide range of lens barrels.

In order to prevent the focus lens holder 1 from interfering with the magnetic circuit 33, it is necessary to partially cut off the space between the sleeve 9 of the focus lens holder 1 and the focus lens group 2. The lens barrel is configured such that the sleeve 9 is disposed in the width direction of the coil 8 in the width direction of the lens barrel 3b.
As compared with the lens barrel described in 54, the notch shape can be made smaller and the rigidity of the focus lens holder 1 can be improved, so that the resonance frequency of the focus lens driver can be increased. Therefore, it is possible to easily improve the vibration characteristics of the focus lens driving body without increasing the thickness of the focus lens holder 1 or adding ribs.

Next, the effect of the leakage magnetic flux from the magnetic circuit 33 on the magnetic sensor 10 will be described with reference to FIGS. Due to the characteristic that the MR elements 32a and 32b change their magnetic resistance in the X and Z directions due to magnetic disturbance, the sensitivity of the magnetic resistance change is large in the X direction, and a signal of a sinusoidal magnetic field intensity change pattern generated from a magnetic scale. When the magnetic disturbance is superimposed on the signal, the signal waveform is offset, causing a waveform distortion or the like of the output signal of the MR element, thereby causing a problem of increasing a position detection error. Further, although the sensitivity of the magnetoresistance change in the Z direction is low, there is a problem that the magnetic resistance change rate decreases due to the magnetic disturbance in the Z direction, and the sensitivity of the MR element decreases.

In the embodiment of the present invention, since the magnetic circuit 33 is configured to be substantially symmetrical in the optical axis direction (X direction), X at the position of the magnetic sensor 10 located at the center of the symmetry.
The leakage magnetic flux in the direction has a very small value. The magnetic circuit 33
Is located laterally at a predetermined distance from the side surface of the magnet when viewed from the optical axis direction, the value of the leakage magnetic flux in the Z direction at the position of the magnetic sensor 10 is very small.

Since the magnetic sensor 10 is arranged so that the direction of the current flowing through the MR elements 32a and 32b is perpendicular to the magnetization direction (Y direction) of the magnet 5, the sensitivity of the MR elements 32a and 32b is reduced. Can be prevented, but M
The direction of the current flowing through the R elements 32a and 32b is
The effect is not lost even if it is substantially perpendicular to the magnetization direction (Y direction).

In the embodiment of the present invention, a magneto-resistive magnetic sensor using an MR element is used, but any type of sensor that outputs an output signal corresponding to the strength of the magnetic force may be used. The present invention can be applied to all types of magnetic sensors by mounting the sensor such that the direction in which the magnetic field is easily affected by the magnetic disturbance coincides with the Z direction. In the embodiment of the present invention, the magnetic sensor 10 is provided in the lens barrel 3b and the magnetic scale 11 is provided in the lens holder 1. On the contrary, the magnetic scale 11 is provided in the lens barrel 3b, and the magnetic sensor is provided in the lens holder 1. Even if 10 is provided, the leakage magnetic flux in the Z direction can be made a very small value in the same manner as described above.

Further, since there is a minute gap in the fitting portion between the sleeve 9 and the guide shaft 4a, when a rotational moment is generated during driving, the focus lens holder 1 slides in the optical axis direction with a slight rotation. From the driving center point 1
A phase shift occurs between the position detection point 13 and the position detection point 13 to degrade control responsiveness. In the worst case, an oscillation state occurs. Therefore, the resolution and response speed must be reduced. There is a problem that a lens deviation occurs.

On the other hand, in the embodiment of the present invention,
First, when viewed from the optical axis direction, the drive center point 12 and the position detection point 1
3 is close to the sleeve 9 and the center of gravity 14 is also the driving center point 1
2, the torque generated during startup and during driving is reduced, and
Since the distance from the drive center point 12 and the position detection point 13 to the sleeve 9 is small, the amount of phase shift, that is, the control error is reduced.

Further, when viewed from the optical axis direction, a straight line connecting the sleeve 9 and the drive center point 12 and the sleeve 9 and the position detection point 1
3, the rotation moment about the Z axis is minimized, and the phase shift amount due to the rotation of the drive center point 12 about the Z axis is minimized. The amount of phase shift due to rotation of the position detection point 13 around the Y axis is minimized. Therefore, control responsiveness is further improved and high accuracy is achieved as compared with the lens barrel described in Japanese Patent Application No. 09-314954 in which the drive center point 12, the sleeve 9, and the position detection point 13 are arranged in a straight line. Drive control can be achieved. Further, as viewed from the optical axis direction, the lens center of the focus lens group 2 is positioned at the sleeve 9 and the position detection point 1.
By arranging the focus lens group on the straight line connecting to the lens group 3, the lens deviation due to the rotation of the focus lens group 2 around the Y axis is minimized.

Incidentally, even if the straight line connecting the sleeve 9 and the drive center point 12 and the straight line connecting the sleeve 9 and the position detection point 13 intersect at a substantially right angle, the straight line connecting the sleeve 9 with the lens center of the focus lens group 2 is also possible. , Sleeve 9 and position detection point 1
Even if 3 and 3 are arranged on substantially one straight line, the effect is not lost. Regarding the geometrical positional relationship among the sleeve 9, the drive center point 12, the position detection point 13, and the lens center of the focus lens group 2 for improving the control responsiveness, the drive means includes a voice coil type linear. Not only actuators, but also ultrasonic motors, DC motors, stepping motors, etc.
Not only magnetic sensors such as MR elements and Hall elements,
An optical sensor composed of a light-emitting element such as an optical LED and a light-receiving element such as a phototransistor, and a light scale in which a light-transmitting part and a light-shielding part are alternately formed at a fine pitch, or a light-emitting element such as an iRED. The use of any type of position detection sensor, such as a combination of photoelectric conversion elements such as a PSD, does not impede the effect.

Finally, in the embodiment of the present invention, a lens barrel equipped with a video camera and having an automatic focusing mechanism for automatically performing focusing on a subject and an electric zoom mechanism for changing a magnification is described. The invention is not limited to such a lens barrel for a video camera, but includes recording and reproducing devices such as hard disks and magneto-optical disks, printing devices such as plotters and printers, and linear actuators and guides used in the field of industrial equipment such as robots. The movable lens structure is movably supported in the lens barrel by means, and the present invention can be applied to various lens barrels having a linear actuator for moving the movable lens structure, such as a lens barrel for a still camera. it can.

[0047]

As described above, the linear actuator of the present invention can be used in a single magnetic circuit composed of a magnet and a yoke which are substantially symmetrical when viewed from the driving direction.
By arranging the magnetic sensor laterally at a predetermined distance from the side surface of the magnet when viewed from the driving direction, it is possible to reduce leakage magnetic flux perpendicular to the magnetization direction of the magnet that jumps into the magnetic sensor when viewed from the driving direction.

The magnetic sensor is a magnetoresistive sensor using an MR element, and the magnetic sensor is viewed from the driving direction so that the direction of the current flowing through the MR element is substantially perpendicular to the magnetization direction of the magnet. By horizontally arranging the magnet at a predetermined distance from the side surface of the magnet, the effect of preventing the sensitivity of the MR element from deteriorating due to magnetic disturbance can be obtained. Also, a driving means composed of one magnetic circuit composed of a magnet and a yoke and a coil, a magnetic sensor and a magnetic scale laterally disposed at a predetermined distance from a side surface of the magnet when viewed from the driving direction. By arranging the magnetized direction of the magnet in the direction opposite to the moving lens group, the lateral width of the magnetic circuit and the coil may be determined so as to generate a thrust according to the weight of the moving lens group. Since the size of the lens barrel does not increase, it is possible to flexibly share the driving parts in accordance with a wider range of specifications of the lens barrel in which the weight of the movable lens group is different. Furthermore, since the notch shape to avoid interference with the magnetic circuit of the lens holder is further reduced and the rigidity of the lens holder can be improved, a lens driving device with a high resonance frequency and excellent vibration characteristics is also added. Can be realized.

Further, when viewed from the optical axis direction, that is, the driving direction, the sleeve is provided transversely to the driving means and the position detecting means, and a straight line connecting the sleeve and the driving point of the driving means, and a detecting point of the sleeve and the position detecting means. And the straight line connecting the sleeve and the drive point of the drive means, the rotational moment about the straight line connecting the sleeve and the drive point of the drive means is minimized, the phase shift of the drive point is minimized, and the sleeve and the position Since the phase shift of the detection point about the straight line connecting the detection point of the detection means as an axis is minimized, a lens driving device having more excellent control response can be realized with a simple configuration at a low cost.

When the center of the optical axis of the movable lens group, the sleeve, and the detection point of the position detecting means are arranged on a substantially straight line when viewed from the optical axis direction, that is, the driving direction, the straight line is defined as the axis. It is possible to realize a high-precision lens driving device in which the obtained lens deviation is minimized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a front side of a rear barrel portion of a lens barrel according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a main part showing an internal configuration of a lens barrel using a linear actuator according to the embodiment of the present invention.

FIG. 3 is an internal perspective view of a focus lens driving portion.

FIG. 4 is a diagram showing a flow of a magnetic flux in a longitudinal section of the focus lens driving portion.

FIG. 5 is a diagram showing a flow of a magnetic flux in a cross section of the focus lens driving portion.

FIG. 6 is a diagram showing a magnetoresistance ratio characteristic of an MR element.

FIG. 7 is a schematic perspective view of a position detecting unit.

[Explanation of symbols]

 1 Focus Lens Holder 2 Focus Lens Group 3a, 3b Lens Barrel 4a, 4b Guide Shaft 5 Magnet 6 Main Yoke 7 Side Yoke 8 --- Coil 9 --- Sleeve 10 --- Magnetic sensor 11 --- Magnetic scale 12 --- Drive center point 13 --- Position detection point 14 --- Center of gravity 15 --- Zoom motor 16 ---- Bracket for Smooth Motor 24--------------------------------------------------------------------------------------------------

Claims (9)

[Claims] 1. A stator comprising a magnet and a yoke magnetized perpendicularly to a driving direction, and a magnetic circuit substantially symmetrically viewed from the driving direction, having a predetermined gap with the magnet. In a linear actuator having a first driving unit having a coil movable in a driving direction as a mover by applying a current so as to be orthogonal to a magnetic flux generated by a magnet, the linear actuator may have any of the mover side and the stator side. A first position detection device in which a magnetic sensor is disposed laterally at a predetermined distance from a side surface of the magnet when viewed from the driving direction, and a magnetic scale is disposed on the other side so as to face a detection surface of the magnetic sensor; A linear actuator comprising means. 2. The magnetic sensor according to claim 1, wherein the magnetic sensor is a magnetoresistive sensor using an MR element.
2. The linear actuator according to claim 1, wherein the magnetic sensor is arranged so as to be substantially perpendicular to a magnetization direction of the magnet. 3. A lens driving device for forming an object image on an image plane by an optical system including a moving lens group, wherein a means for driving the moving lens group includes changing a magnetization direction of the magnet to the moving lens group. 3. A lens driving device using the linear actuator according to claim 1 or 2 disposed in opposite directions. 4. A lens comprising: guide means for guiding movement of the movable lens group in the optical axis direction; and lens holding means having a sleeve for holding the movable lens group and fitting with the guide means. 4. The lens driving device according to claim 3, wherein the sleeve is disposed close to the first driving unit and the first position detecting unit when viewed from an optical axis direction. 5. A straight line connecting the sleeve and the drive point of the first drive means and a straight line connecting the sleeve and the detection point of the first position detection means are substantially perpendicular to each other when viewed from the optical axis direction. 5. The lens driving device according to claim 4, wherein the lens driving device intersects. 6. The moving lens group as viewed from the optical axis direction,
2. The apparatus according to claim 1, wherein the position of the center of gravity of a lens driving body comprising said lens holding means, said first driving means, and said first position detecting means is arranged near said first driving means. The lens driving device according to claim 4 or 5. 7. A guide means for guiding the movement of the movable lens group in the optical axis direction, and the lens holding means having the sleeve for holding the movable lens group and fitting with the guide means. A lens driving device having the following arrangement: when viewed from the optical axis direction, the sleeve is laterally provided on the second driving means and the second position detecting means, and the sleeve is connected to a driving point of the second driving means. A lens driving device, wherein a straight line and a straight line connecting the sleeve and the detection point of the second position detecting means intersect at a substantially right angle. 8. The optical system according to claim 1, wherein the center of the optical axis of the movable lens group, the sleeve, and the detection point of the second position detecting means are arranged substantially in a straight line when viewed from the optical axis direction. 8. The lens driving device according to 7. 9. A driving device for driving an imaging lens according to claim 3,
Or claim 4, claim 5, claim 6, or claim 7
A lens barrel characterized by using the lens driving device described above.