JP2006047907A - Lens driving device and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact lens driving device capable of driving a lens in an optical axis direction, and to provide an imaging apparatus. <P>SOLUTION: The lens driving device is equipped with a stator which has cylindrical shape, a rotor which is positioned in the cylindrical shape of the stator and driven to be rotated by magnetic field formed by the stator, a lens holder which is positioned on the further inside of the cylindrical shape of the rotor and holds the lens, a changing mechanism which changes the direction of force generated by driving and rotating the rotor to a direction going along the optical axis of the lens and transmits the force to the lens holder, and a holding body which has a guiding part to guide the rotation of the rotor and a positioning part to regulate the position of the stator by stator's physical abutting, and holding a space between the rotor and the stator at the predetermined one. <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, and the captured images are immediately taken on the spot to other mobile phones, personal computers, etc. 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 the stepping motor, a gap (referred to as an air gap) is provided between the rotor and the stator in order to rotate the rotor. There's a problem. Conversely, if the air gap is narrow, the attractive force with the magnetic field formed by the stator increases, so if the air gap is not uniform over the entire circumference of the rotor, the rotor is attached to the stator at a particularly narrow portion of the air gap. The torque is strongly attracted and biased, and the torque decreases.

  A stepping motor applied to a normal size digital camera or the like is relatively large so that it has a large original torque and a sufficient air gap. Therefore, the influence of torque reduction is small.

  However, in an imaging device that is much smaller than a digital camera, the lens is more susceptible to friction due to the downsizing of the device, making it difficult to drive the lens smoothly. There is a problem that will not be driven at all.

  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 drive a lens along an 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 positioned further inside the cylindrical shape of the rotor and holding the lens so that the optical axis is along the cylindrical axis;
A conversion mechanism that converts the direction of the force due to the rotational drive of the rotor into a direction along the optical axis of the lens and transmits it to the lens holder;
It has a guide portion for guiding the rotation of the rotor, and a holding body for holding the interval between the rotor and the stator at a predetermined interval, the positioning portion determining the position of the stator by physically contacting the stator. Features.

  According to the lens driving device of the present invention, the position of the stator is defined by the positioning portion of the holding body, and the rotation of the rotor is guided by the guiding portion of the holding body, so that the interval between the stator and the rotor is uniformed by a simple structure. Various intervals can be maintained. Therefore, the problem that the torque is reduced due to the bias of the rotor is avoided, and the lens is driven smoothly. Moreover, since the position of the stator and the rotor is defined by one member, the lens driving device of the present invention can be prevented from increasing in size, and can be mounted on a small device such as a mobile phone.

Further, an image pickup apparatus of the present invention that achieves the above object is an image pickup apparatus that drives a lens in a direction along an optical axis, forms an image of subject light with the lens, and acquires 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 that is located further inside the cylindrical shape of the rotor and holds the lens so that the optical axis is along the cylindrical axis;
A conversion mechanism that converts the direction of the force due to the rotational drive of the rotor into a direction along the optical axis of the lens and transmits it to the lens holder;
A holding part that holds a gap between the rotor and the stator at a predetermined interval, and a guide part that guides the rotation of the rotor, and a positioning part that determines a position of the stator by physically contacting the stator;
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 the apparatus is mounted on a small device such as a mobile phone, it is possible to avoid the problem that the torque of the rotor decreases and to drive the lens smoothly.

  ADVANTAGE OF THE INVENTION According to this invention, the small lens drive device which can drive a lens along an optical axis, and an imaging device can be provided.

  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 imaging device 1 is a small imaging device mounted on a mobile phone or the like, and focuses a subject by driving a plurality of lenses in a direction along the optical axis (hereinafter, this direction is referred to as a front-rear direction). An autofocus function is provided. This imaging device 1 has an outer appearance in which a cylindrical stator 30 is sandwiched between an upper cover 10 and a lower cover 40, and a magnet and a plurality of lenses (to be described later) are placed inside the stator 30. A held lens holder 20 or the like is disposed. The stator 30 corresponds to an example of a stator according to the present invention.

  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 magnet 50 corresponds to an example of a rotor according to the present invention, and 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. . Further, 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. .

  For example, the magnet 50 is passed through a ring-shaped head in which N poles and S poles are alternately formed along the inner periphery, thereby alternately alternating N and S poles along the outer periphery of the cylindrical shape. It is a permanent magnet with a magnetic pole. 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. 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 the outer surface of the lens holder 20.

  The lens holder 20 holds lenses arranged in the order of the first lens 21, the second lens 22, and the third lens 23 from the side close to the upper cover 10. 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 10) (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 20b extending in the front-rear direction is provided in the space on the side of the first lens 21 of the lens holder 20, and the outer surface of the portion holding the second lens 22 and the third lens 23. Is provided with a spiral groove 20a.

  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. A combination of the spiral groove 51a and the spiral groove 20a corresponds to an example of a conversion mechanism according to the present invention.

  The upper cover 10 and the lower cover 40 shown in FIG. 2 are connected by screws 80 (not shown in FIG. 2, see FIG. 4).

  The upper cover 10 is provided with a concave portion 10 a 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 50 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 part 20b of the lens holder 20 and the concave part 10a of the upper cover 10 are fitted to each other, such rotation of the lens holder 20 is prevented.

  The upper cover 10 is also provided with a first convex portion 10 b that contacts the stator 30 and defines the position of the stator 30, and a second convex portion 10 c that contacts the magnet 50 and guides the rotation of the magnet 50. It has been. If the interval between the stator 30 and the magnet 50 is biased, the stator 30 strongly attracts the magnet 50 at a portion where the interval is narrow, the torque is reduced, and the magnet 50 does not rotate smoothly. In the present embodiment, the spacing between the stator 30 and the magnet 50 is uniformly maintained by the first convex portion 10b and the second convex portion 10c. The 2nd convex part 10c is an example of the guide part said to this invention, and the 1st convex part 10b is equivalent to an example of the positioning part said to this invention. Moreover, what united the 1st convex part 10b and the 2nd convex part 10c is equivalent to an example of the holding body said to this invention.

  The lower cover 40 holds the low-pass filter 70 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 70. In the low-pass filter 70, unnecessary fine spatial frequency components included in the subject light are leveled. By using the low-pass filter 70, problems such as pseudo colors and moire can be reduced.

  The subject light that has passed through the low-pass filter 70 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 50 rotates by one step, and the rotating body 51 rotates as the magnet 50 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 is reversed. When the magnitudes of the contrasts are reversed, a pulse current in a direction opposite to the direction in which the stator 30 is energized immediately before is supplied to the stator 30 to return the lens holder 20 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, the feature of the present invention in the image pickup apparatus 1 is the action of the first convex portion 10b and the second convex portion 10c that maintain the distance between the stator 30 and the magnet 50. Hereinafter, the operation of the first convex portion 10b and the second convex portion 10c in the process of assembling the imaging device 1 will be described.

  FIG. 4 is an exploded perspective view of the imaging apparatus 1.

  In the imaging apparatus 1, a plurality of pillars 11 provided on the upper cover 10 and the lower cover 40 are connected by screws 80, and the stator 30 is disposed in a space surrounded by the upper cover 10, the pillars 11, and the lower cover 40. The

  When the imaging apparatus 1 is assembled, first, the stator 30 is disposed inside the upper cover 10.

  FIG. 5 is a perspective view of the upper cover 10 on which the stator 30 is disposed as viewed from the back side.

  The upper cover 10 is provided with a first convex portion 10b and a second convex portion 10c which are also shown in FIG. The stator 30 is fitted and adhered to the outside of the first convex portion 10b of the upper cover 10. At this time, the position of the stator 30 in the left-right direction is fixed by the first protrusion 10b, and the stator 30 can be attached to the upper cover 10 with high accuracy.

  Subsequently, as shown in FIG. 4, the rotating body 51 and the lens holder 20 are attached inside the cylindrical shape of the magnet 50. Further, the magnet 50 is fitted between the first convex portion 10b and the second convex portion 10c of the upper cover 10 shown in FIG. The position of the magnet 50 in the left-right direction is defined by the first convex portion 10b and the second convex portion 10c, and the distance from the stator 30 is maintained.

  When the stator 30 and the magnet 50 are attached to the upper cover 10, the lower cover 40 and the upper cover 10 are connected by screws 80. When the column 11 of the upper cover 10 and the lower cover 40 are bonded with an adhesive or the like, the CCD 60 is held by the lower cover 40 that also serves as the CCD cover, and the imaging apparatus 1 is configured.

  As described above, in the imaging device 1, the positions of the stator 30 and the magnet 50 are defined by the first and second convex portions 10b and 10c provided on the upper cover 10, and the positions thereof are defined. Compared with the case where each part is prepared, the size of the apparatus is suppressed. In addition, the first convex portion 10b and the second convex portion 10c hold the gap between the stator 30 and the magnet 50 evenly, and a part of the magnet 50 is strongly attracted to the stator 30, so that the magnet 50 is It is possible to avoid a problem that the motor does not rotate smoothly.

  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.

  In the above description, an example in which a CCD is applied as an image sensor has been described. However, the image sensor referred to in the present invention may be, for example, a MOS or the like.

  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.

  Moreover, although the example which provides the 1st convex part 10b and the 2nd convex part 10c in the upper cover 10 was demonstrated above, the holding body said to this invention may be provided in the lower cover 40, 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.

1 is an external perspective view of an imaging apparatus to which an embodiment of the present invention is applied. 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 figure which shows the stator 30 and the magnet 50. FIG. 1 is an exploded perspective view of an imaging device 1. FIG. It is the perspective view which looked at the upper cover 10 with which the stator 30 is arrange | positioned from the back side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 10 Upper cover 10a Concave part 10b 1st convex part 10c 2nd convex part 11 Pillar 20 Lens holder 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 50 Magnet 51 Rotating body 51a Spiral groove 60 CCD
70 Low pass filter 80 screw

Claims (2)

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 that is positioned further inside the cylindrical shape of the rotor and holds the lens so that the optical axis is along the cylindrical axis;
A conversion mechanism that converts the direction of the force generated by the rotational drive of the rotor into a direction along the optical axis of the lens and transmits the direction to the lens holder;
A holding portion for holding a gap between the rotor and the stator at a predetermined interval, having a guide portion for guiding the rotation of the rotor, and a positioning portion for determining the position of the stator by the physical contact of the stator. A lens driving device comprising: 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 that is positioned further inside the cylindrical shape of the rotor and holds the lens so that the optical axis is along the cylindrical axis;
A conversion mechanism that converts the direction of the force generated by the rotational drive of the rotor into a direction along the optical axis of the lens and transmits the direction to the lens holder;
A holding portion for holding a gap between the rotor and the stator at a predetermined interval, having a guide portion for guiding the rotation of the rotor, and a positioning portion for determining the position of the stator by the physical contact of the stator. ,
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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