JP2005351964A - Lens driving device and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-size lens driving device which can avoid displacement of the optical axis of a lens and which can drive a lens along the optical axis, and to provide an imaging apparatus. <P>SOLUTION: The lens driving device is equipped with: a stator having a cylindrical form and generating a magnetic field in the cylindrical form; a rotor located in the cylindrical form of the stator and to be driven to rotate by the magnetic field generated by the stator; a lens holder located inside the rotor to hold a lens and regulated in the movement in the direction perpendicular to the optical axis of the lens via a predetermined regulating part; and a converting mechanism to convert the direction of the force by the rotation of the rotor into a direction along the axis of the cylindrical form of the rotor and to transmit the force to the lens holder via a part other than the regulating part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lens driving device that drives a lens in a direction along an optical axis, and an imaging device that acquires image data representing subject light.

  2. Description of the Related Art It is widely practiced to incorporate an imaging device that captures a subject and obtains a digital captured image in a small device such as a mobile phone or a PDA (Personal Digital Assistant). Since an imaging device is provided in a small device that is always carried around, it is possible to easily take a picture anytime without having to carry a digital camera or a video camera. In addition, these small devices are generally equipped with a data communication function using wireless or infrared rays in advance. There is also an advantage that it can be sent to.

  However, since an imaging device built in a small device such as a mobile phone is considerably smaller than a normal digital camera, the size of components such as a lens and a charge coupled device (CCD) and the components are not limited. The storage space is greatly limited. For this reason, these small devices have insufficient shooting functions and image quality of captured images to be used as alternative devices for digital cameras. For obtaining images instead of memos, and for standby screens for mobile phones and the like. As in the case of obtaining an image, the use is often limited for shooting that does not require image quality.

  In recent years, small CCDs with high pixels and small lenses with high contrast have been developed in these respects, and the quality of captured images taken using small devices such as mobile phones and PDAs has rapidly increased. Is going on. In order to enhance the imaging function, which remains as a remaining issue, it is particularly desirable that these small devices are equipped with an autofocus function and a zoom function that are normally installed in digital cameras.

  The autofocus function and the zoom function are realized by moving a plurality of lenses in a direction along the optical axis in the imaging apparatus. In digital cameras, video cameras, and the like, as a lens driving method, a method using rotation of a DC motor or a stepping motor, a method using compression / expansion of a piezoelectric element, and the like are known. When these methods are applied to a small device such as a mobile phone, a cylindrical hollow rotor that surrounds the outer periphery of the lens barrel holding the lens in terms of downsizing of the device and accuracy of lens movement control. It is considered preferable to use a hollow stepping motor that rotates the stator by applying a pulse current to the stator that surrounds the outer periphery of the hollow rotor.

As a lens driving method to which such a hollow stepping motor is applied, for example, a method of driving the lens barrel in a direction along the optical axis via a moving mechanism such as a cam mechanism between the lens barrel and the rotor ( For example, see Patent Literature 1, Patent Literature 2, and Patent Literature 3), a method of moving a lens barrel with the rotor itself (for example, Patent Literature 4, Patent Literature 5, Patent Literature 6), a lens barrel and a rotor. A method of integrating them (for example, Patent Document 7) has been proposed.
JP-A-56-147132 JP 59-109006 JP 59-109007 JP 60-415 JP-A-60-416 JP 60-417 Japanese Patent Laid-Open No. 62-195615

  Here, in a digital camera, a video camera, or the like using a stepping motor as described in the above-mentioned patent document, the lens barrel has a sufficient margin with the rotor and the moving mechanism in order to drive the lens smoothly. Is engaged loosely. For this reason, the lens barrel may rattle when the lens is driven, and the optical axis of the lens may deviate from the rotation axis of the rotor. However, in a normal size digital camera or the like, a relatively large lens is used. In addition, even if the position of the optical axis of the lens is slightly deviated, the influence on the captured image is small.

  However, in an imaging device that is much smaller than a digital camera, the lens used is also greatly reduced in size, so the deviation of the lens optical axis that occurs when the lens is driven has a significant effect on the captured image, and the captured image is imaged. There is a risk of blurring.

  In addition, since a small imaging device is strongly affected by friction and the like with the downsizing of the device, the lens is originally difficult to drive smoothly, and a lens barrel and a moving mechanism to avoid the above-described image blurring. There is a problem that the lens will not be driven at all if the two are tightly engaged.

  In view of the above circumstances, an object of the present invention is to provide a small lens driving device and an imaging device that can avoid the positional deviation of the optical axis of the lens and can drive the lens along the optical axis.

The lens driving device of the present invention that achieves the above object is a lens driving device that drives a lens in a direction along the optical axis.
A stator having a cylindrical shape and forming a magnetic field in the cylindrical shape;
A rotor positioned within the cylindrical shape of the stator and having a cylindrical shape coaxial with the cylindrical shape, the rotor being driven to rotate relative to the stator by a magnetic field formed by the stator;
A lens holder that is positioned further inside the cylindrical shape of the rotor and holds the lens through a predetermined restricting portion, and the movement of the lens in a direction perpendicular to the optical axis of the lens is restricted;
A conversion mechanism that converts the direction of the force due to the rotational drive of the rotor into a direction along the cylindrical axis of the rotor and transmits it to the lens holder via other parts except for the restriction part, To do.

  According to the lens driving device of the present invention, the movement of the lens holder in the direction perpendicular to the lens optical axis is restricted via a predetermined defining portion (hereinafter, simply referred to as a defining portion), and the defining portion is The rotational force of the rotor is transmitted to the lens holder through a portion (hereinafter referred to as a non-specified portion) excluding the portion. Therefore, in order to move the lens holder smoothly, even when the conversion mechanism and the non-specified portion of the lens holder are loosely fitted together, Since the movement in the direction perpendicular to the lens optical axis is restricted via the prescribed portion, it is possible to avoid the positional deviation of the lens optical axis.

  Further, in the lens driving device according to the present invention, the conversion mechanism is provided on the outer surface of the spiral holder provided on the inner peripheral surface of the rotor and the outer surface of the lens holder other than the restriction portion meshed with the spiral groove. It is preferable that the spiral groove is formed.

  According to this preferred embodiment of the lens driving device, the distance between the rotor and the lens holder can be reduced compared with the case where a cam mechanism or the like is applied as the conversion mechanism, and the device can be miniaturized.

Further, an imaging apparatus of the present invention that achieves the above object is an imaging apparatus that acquires image data representing subject light by driving the lens in a direction along the optical axis and imaging subject light with the lens.
A stator having a cylindrical shape and forming a magnetic field in the cylindrical shape;
A rotor positioned within the cylindrical shape of the stator and having a cylindrical shape coaxial with the cylindrical shape, the rotor being driven to rotate relative to the stator by a magnetic field formed by the stator;
A lens holder that is positioned further inside the cylindrical shape of the rotor and holds the lens through a predetermined restricting portion, and the movement of the lens in a direction perpendicular to the optical axis of the lens is restricted;
A conversion mechanism that converts the direction of the force due to the rotational drive of the rotor into a direction along the cylindrical axis of the rotor and transmits it to the lens holder via the other part excluding the restriction part;
An imaging device is provided that forms an image of subject light that has passed through the lens and acquires image data representing the subject light.

  According to the imaging apparatus of the present invention, even when mounted on a small device such as a mobile phone, it is possible to avoid the positional deviation of the optical axis of the lens and drive the lens along the optical axis.

  Note that only the basic form of the imaging apparatus according to the present invention is shown here, but this is only for avoiding duplication, and the imaging apparatus according to the present invention is not limited to the above basic form. Various forms corresponding to the respective forms of the lens driving device described above are included.

  According to the present invention, it is possible to provide a small lens driving device and an imaging device capable of avoiding the positional deviation of the optical axis of the lens and driving the lens along the optical axis.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an external perspective view of an imaging apparatus to which an embodiment of the present invention is applied.

  The image pickup apparatus 1 is a small image pickup apparatus mounted on a mobile phone or the like, and drives a plurality of lenses in a direction along the optical axis (hereinafter, the direction along the optical axis is referred to as the front-rear direction). An autofocus function is available to adjust the focus. The imaging device 1 has an external appearance in which a cylindrical stator 30 is sandwiched between an upper cover 10 and a lower cover 40, and a magnet and a lens to be described later are held inside the stator 30. A lens holder 20 is disposed.

  FIG. 2 is a cross-sectional view of the imaging device 1 shown in FIG. 1 cut along a plane passing through the straight line AA ′.

  2 shows the upper cover 10, the lower cover 40, the stator 30, and the lens holder 20 that are also shown in FIG. 1, and further includes a first lens 21, a second lens 22, a third lens 23, a magnet 50, A rotating body 51, a CCD 60, and the like are shown.

  The lens holder 20, the magnet 50, and the rotating body 51 have a cylindrical shape coaxial with the stator 30. The magnet 50, the rotating body 51, and the lens holder 20 are arranged inside the stator 30 in this order from the side close to the stator 30. ing. The stator 30 and the magnet 50 constitute a stepping motor. When a pulse current is applied to the stator 30, the magnet 50 is rotated by the number of rotations corresponding to the pulse current. The stator 30 corresponds to an example of the stator according to the present invention, and the magnet 50 corresponds to an example of the rotor according to the present invention. The lens holder 20 corresponds to an example of a lens holder according to the present invention.

  Here, the description of FIG. 2 is temporarily interrupted, and the stator 30 and the magnet 50 will be described in detail with reference to FIG.

  FIG. 3 is a diagram showing the stator 30 and the magnet 50.

  The stator 30 is composed of two layers of coil parts, an upper coil part 30a and a lower coil part 30b. Since the upper coil portion 30a and the lower coil portion 30b have the same configuration, the description of the configuration of the lower coil portion 30b is omitted, and only the configuration of the upper coil portion 30a will be described.

  The upper coil portion 30a is formed to be surrounded by a cylindrical shape by an upper coil cover 32 and a lower coil cover 33, and a coil 31 made of a wound conductive wire is stored in the inside surrounded by the cover. . The upper coil cover 32 and the lower coil cover 33 are provided with teeth 32a and 33a arranged so as to alternately mesh with each other inside the cylindrical shape. There is a gap between the teeth 32a and the teeth 33a.

  A pulse current is alternately applied to the coil 31 of the upper coil portion 30a and the coil 31 of the lower coil portion 30b. When a pulse current is applied, magnetic field lines are generated in the coil 31, and the magnetic field lines are guided to the inside of the cylindrical shape by the upper coil cover 32 and the lower coil cover 33. When the introduced magnetic field lines reach the teeth 32a and 33a, the magnetic field lines once enter the air and cross the gap. As a result, one of the teeth 32 a and 33 a arranged so as to mesh with each other is an N pole, and the other is an S pole, and magnetic fields of the N pole and the S pole are alternately formed along the cylindrical inner periphery of the stator 30. .

  The magnet 50 is made of a magnetic material such as neodymium. For example, the magnet 50 is passed through the inside of a ring-shaped head in which N poles and S poles are alternately formed along the inner periphery. It is a permanent magnet that is alternately poled along the outer circumference with N and S poles. The magnet 50 is rotationally driven with respect to the stator 30 by a repulsive force and an attractive force with a magnetic field formed by the stator 30.

  The rotation drive of the magnet 50 will be described.

  The magnet 50 has 48 poles, and each of the upper coil portion 30a and the lower coil portion 30b has 48 teeth. Further, the position of the teeth of the upper coil portion 30a and the position of the teeth of the lower coil portion 30b are shifted by half of the teeth. When a pulse current is applied to the stator 30 as will be described later, the magnet 50 rotates with one pole as one step and rotates once in 48 steps.

  When rotating the magnet 50 in the forward direction, the energization is repeated in the order of the forward direction of the upper coil portion 30a, the forward direction of the lower coil portion 30b, the reverse direction of the upper coil portion 30a, and the reverse direction of the lower coil portion 30b. The magnet 50 can be reliably rotated in the forward direction. Further, by repeating energization in the order of the forward direction of the upper coil portion 30a, the reverse direction of the lower coil portion 30b, the reverse direction of the upper coil portion 30a, and the forward direction of the lower coil portion 30b, the magnet 50 is rotated in the reverse direction. be able to.

  This is the end of the description of FIG. 3, and the description will return to FIG.

  A rotating body 51 shown in FIG. 2 is bonded to the inside of the magnet 50 and is rotated as the magnet 50 rotates. The rotating body 51 is made of a material having a thermal expansion coefficient substantially equal to that of the magnetic body constituting the magnet 50. A spiral groove 51 a is provided on the inner surface of the rotating body 51, and the spiral groove 51 a meshes with a spiral groove 20 a (described later) provided on a part of the outer surface of the lens holder 20.

  The lens holder 20 is made of a material having a small thermal expansion coefficient, and holds lenses arranged in order of the first lens 21, the second lens 22, and the third lens 23 from the side close to the upper cover 1. The first lens 21, the second lens 22, and the third lens 23 satisfy the following conditions.

  First, in this example, the first lens 21 is made of a glass material, and has a meniscus shape having a positive power with a front surface (side closer to the upper cover) (hereinafter referred to as a surface) having a convex shape.

  The second lens 22 is made of a plastic material. In this example, the second lens 22 has a meniscus shape having a negative power with an aspherical back surface and a concave surface.

  The third lens 23 is made of a plastic material, and both surfaces of the front and back surfaces are aspherical, and the back surface is a concave shape near the optical axis and has a negative power shape.

Further, if the paraxial focal length of the entire lens system is f, the paraxial focal length of the third lens 23 is f3, the radius of curvature of the surface of the first lens 21 is R1, and the half angle of view at the maximum image height is θ,
0.6 <R1 / f <0.8 (1)
-1.0 <f3 / f <0 (2)
0.60 <tan θ <0.70 (3)
Meet.

  By applying the first lens 21, the second lens 22, and the third lens 23 that satisfy the above conditions, a compact and highly accurate lens group can be configured.

  Further, a convex portion 20 b extending in the front-rear direction is provided on the outer surface (first portion 201) on the side of the first lens 21 of the lens holder 20, and holds the second lens 22 and the third lens 23. A spiral groove 20a is provided on the outer surface (second portion 202) of the portion being formed. The first portion 201 corresponds to an example of a predetermined restricting portion referred to in the present invention, and the second portion 202 corresponds to an example of a portion excluding the restricting portion referred to in the present invention. The combination of the spiral groove 20a provided in the second portion 202 of the lens holder 20 and the spiral groove 51a provided in the rotating body 51 corresponds to an example of the moving mechanism referred to in the present invention.

  A mechanism for driving the lens holder 20 in the front-rear direction will be described.

  When a pulse current is applied to the stator 30, the rotating body 51 is rotated once every 48 steps as the magnet 50 rotates. The spiral groove 51a of the rotating body 51 is provided two more times (= 96 steps) than the spiral groove 51a of the lens holder 20, and the lens holder 20 can move by 96 steps.

  The rotational force of the rotating body 51 is converted into a force in the front-rear direction by the spiral groove 51a and the spiral groove 20a. The converted force in the front-rear direction is transmitted to the lens holder 20, and the lens holder 20 is driven in the front-rear direction. In this embodiment, the lens holder 20 moves about 1.25 mm in the front-rear direction with a full stroke (= 96 steps), and moves about 13 μm in the front-rear direction in one step. That is, in this imaging device 1, the lens position can be controlled in units of 13 μm.

  The upper cover 10 and the lower cover 40 shown in FIG. 2 are connected by screws (not shown).

  Similar to the lens holder 20, the upper cover 10 is made of a material having a small thermal expansion coefficient. The upper cover 10 is provided with a concave portion that extends in the front-rear direction and fits with the convex portion 20 b at a portion corresponding to the convex portion 20 b of the lens holder 20. The rotational force of the magnet 40 is transmitted to the lens holder 20 by the spiral groove 51a and the spiral groove 20a, but when the movement of the lens holder 20 in the rotation direction is not restricted, the lens holder 20 moves in the front-rear direction while rotating. Therefore, the image may be shifted due to the eccentricity of the lens. Since the convex portion 20b of the lens holder 20 and the convex portion 20b of the upper cover are fitted to each other, such rotation of the lens holder 20 is prevented.

  The lower cover 40 holds the low-pass filter 41 and the CCD 60.

  The subject light that has passed through the first lens 21, the second lens 22, and the third lens 23 is received by the CCD 60 through the low-pass filter 41. In the low-pass filter 41, unnecessary fine spatial frequency components included in the subject light are leveled. By using the low-pass filter 41, problems such as pseudo colors and moire can be reduced.

  The subject light that has passed through the low-pass filter 41 is received by the CCD 60, and image data representing the subject is generated. The CCD 60 corresponds to an example of an image sensor according to the present invention.

  In the imaging apparatus 1 as described above, the autofocus function is realized by the following procedure. In the following description, it is assumed that the lens holder 20 moves forward by applying a forward pulse current to the stator 30.

  First, subject light is roughly read by the CCD 60, and low-resolution data representing the subject light is generated. This low resolution data is transmitted to a CPU such as a mobile phone provided with the imaging device 1.

  Subsequently, a forward pulse current for moving the lens holder 20 by one step is supplied to the stator 30.

  When a pulse current is applied to the stator 30, the magnet rotates by one step, and the rotating body 51 rotates as the magnet rotates. The rotational force of the rotating body 51 is converted into a forward force and transmitted to the lens holder 20, and the lens holder 20 moves about 13 μm in the forward direction.

  When the lens holder 20 moves, the subject light is read again by the CCD 60 and low resolution data is generated. This low resolution data is also transmitted to a CPU such as a mobile phone provided with the imaging device 1.

  The CPU detects the contrast of each of the two low-resolution data transmitted from the CCD 60, and determines which of the detected contrasts is greater. When the contrast of the previous low resolution data is larger, a reverse pulse current for returning the lens holder 20 by one step backward is energized to the stator 30 and the contrast of the subsequent low resolution data is larger. In this case, a forward pulse current that moves the lens holder 20 forward one step further is supplied to the stator 30.

  As described above, the process of detecting the contrast by moving the lens holder 20 is continued for up to 96 steps until the magnitude of the contrast of the previous low-resolution data and the contrast of the subsequent low-resolution data are reversed. When the magnitudes of these contrasts are reversed, the stator 30 is energized with a pulse current in a direction opposite to the direction energized immediately before, and the lens holder 20 is returned by one step. The position of the lens holder 20 at this time is an in-focus position where the contrast is maximized.

  The imaging device 1 is basically configured as described above.

  Here, in the imaging apparatus 1, the spiral groove 20a of the lens case 20 and the spiral groove 51a of the rotating body 51 are loosely engaged with each other in order to drive the lens smoothly. Therefore, the imaging apparatus 1 requires a mechanism that avoids movement in a direction perpendicular to the optical axis of the lens (hereinafter, a direction perpendicular to the optical axis is referred to as a vertical direction) due to rattling of the lens case 20. .

  FIG. 4 is an external perspective view of the lens holder 20.

  The outer surface of the lens holder 20 has two parts, a first part 201 in which the first lens 21 is provided on the inner side and a second part 202 in which the second lens 22 and the third lens 23 are provided on the inner side. It is divided into parts. The first portion 201 corresponds to an example of a “predetermined restricting portion” according to the present invention, and the second portion 202 corresponds to an example of a “portion excluding the restricting portion” according to the present invention.

  The first portion 201 is provided with a convex portion 20 b that fits into the concave portion 10 a of the upper cover 10 and prevents the lens holder 20 from rotating. The second portion 202 has a helical groove of the rotating body 51. A spiral groove 20 a that fits with 51 a and transmits a driving force to the lens holder 20 is provided.

  Since the first lens 21 has a smaller outer diameter than the second lens 22 and the third lens 23, the first portion 201 of the lens holder 20 that holds the first lens 21 is more indented than the second portion 202. It is out. The first portion that is recessed is surrounded by the upper cover 10, so that the movement of the lens holder 20 in the vertical direction is restricted.

  As described above, since the lens holder 20 is restricted from moving in the vertical direction via the first portion 201 instead of the second portion 202 contacting the spiral groove 51a of the rotating body 51, smooth lens driving is possible. While maintaining the above, it is possible to avoid the problem that the lens moves in the vertical direction and the position of the optical axis shifts.

  Further, when the imaging device 1 is mounted on a mobile phone or the like, it is required that the performance is maintained in a temperature environment of about −20 ° C. to + 70 ° C. In the present embodiment, the upper cover 10 and the lens holder 20 are made of a material having a low coefficient of thermal expansion and small deformation due to temperature, and the upper cover 10 is positioned in the vertical direction of the lens holder 20 regardless of the temperature. It can be regulated with high accuracy.

  On the other hand, since the magnet 50 is made of a magnetic material having a high thermal expansion coefficient, the magnet 50 is made of a substance having a high thermal expansion coefficient substantially equal to that of the magnet 50 in order to avoid distortion of the rotating body 51 due to thermal deformation of the magnet 50. Is done. Further, in order to realize smooth lens driving even when the rotator 51 has expanded, the spiral groove 51a of the rotator 51 and the spiral groove 20a of the lens case 20 are engaged with a sufficient margin. Yes. For this reason, the lens case 20 is likely to rattle when the lens is driven, but since the upper cover 10 surrounds the first portion 201 of the lens holder 20, the movement of the lens in the vertical direction is restricted.

  Thus, according to the imaging device 1 of the present embodiment, the position of the optical axis of the lens can be maintained at the correct position regardless of the temperature, and smooth lens driving can be maintained.

  Here, the example in which the stepping motor that controls the rotation of the rotor by applying a pulse current to the stator has been described above. However, the motor for driving the lens holder according to the present invention is a DC motor or the like. Also good.

  Moreover, although the example which applies a helical groove | channel as a conversion mechanism was demonstrated above, the conversion mechanism said to this invention may be a cam groove, a cam pin, etc., for example.

  In the above description, the example in which the lens holder is driven to realize the autofocus function has been described. However, the lens driving device and the imaging device of the present invention may be configured to realize a zoom function, for example. Both the function and the auto focus function may be realized.

It is sectional drawing when cut | disconnecting the imaging device 1 shown in FIG. 1 in the surface which passes along straight line AA '. It is a hardware block diagram of the computer shown in FIG. It is a figure which shows the stator 30 and the magnet 50. FIG. 2 is an external perspective view of a lens holder 20. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 10 Upper cover 10a Concave part 11 Column 20 Lens holder 201 1st part 202 2nd part 20a Spiral groove 20b Convex part 21 1st lens 22 2nd lens 23 3rd lens 30 Stator 30a Upper coil part 30b Lower coil Part 31 Coil 32 Upper coil cover 33 Lower coil cover 32a, 33a Teeth 40 Lower cover 41 Low pass filter 50 Magnet 51 Rotating body 51a Spiral groove 60 CCD

Claims (3)

In the lens driving device that drives the lens in the direction along the optical axis,
A stator having a cylindrical shape, and forming a magnetic field in the cylindrical shape;
A rotor positioned within the cylindrical shape of the stator and having a cylindrical shape coaxial with the cylindrical shape, the rotor being driven to rotate relative to the stator by a magnetic field formed by the stator;
A lens holder in which movement in a direction perpendicular to the optical axis of the lens is restricted via a predetermined restriction part that holds the lens located further inside the cylindrical shape of the rotor;
A conversion mechanism for converting the direction of the force generated by the rotational drive of the rotor into a direction along a cylindrical axis of the rotor and transmitting the converted direction to the lens holder via the other part except the restriction part; A lens driving device.   The conversion mechanism includes a spiral groove provided on the inner peripheral surface of the rotor, and a spiral groove provided on the outer surface of the lens holder other than the restriction portion, which meshes with the spiral groove. The lens driving device according to claim 1, wherein the lens driving device is one. In an imaging device that drives a lens in a direction along the optical axis, forms an image of subject light with the lens, and obtains image data representing the subject light.
A stator having a cylindrical shape, and forming a magnetic field in the cylindrical shape;
A rotor positioned within the cylindrical shape of the stator and having a cylindrical shape coaxial with the cylindrical shape, the rotor being driven to rotate relative to the stator by a magnetic field formed by the stator;
A lens holder in which movement in a direction perpendicular to the optical axis of the lens is restricted via a predetermined restriction part that holds the lens located further inside the cylindrical shape of the rotor;
A conversion mechanism that converts the direction of the force generated by the rotational drive of the rotor into a direction along a cylindrical axis of the rotor and transmits the direction to the lens holder through the other part excluding the restriction part;
An imaging apparatus comprising: an imaging element that forms an image of subject light that has passed through the lens and acquires image data representing the subject light.

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