JP2005345514A - Lens-driving device and image pickup unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small lens-driving device which drives a lens along an optical axis, and to provide an image pickup unit. <P>SOLUTION: The lens-driving device is provided with a stator which has a cylindrical shape and forms a magnetic field within the cylindrical shape, a rotor which is located in the cylindrical shaped stator and rotatively driven by the magnetic field formed by the stator, a lens holder which is located further inside the rotor and holds a small lens which is located at the end part of the array of a plurality of lenses, a conversion mechanism which converts the direction of force caused by the rotative driving of the rotor, in a direction along the optical axis of the lens and transmits the force to the lens holder, and a rotation-stopping mechanism which is arranged at the small lens side and prevents the rotation of the lens holder by physical contact. <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 (hereinafter, the direction along the optical axis is referred to as the front-rear direction). In digital cameras and digital video cameras, 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 the device and the 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 this 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, Patent Literature 1, Patent Literature 2, and Patent Literature 3), a method of moving the lens barrel by the rotor itself (for example, Patent Literature 4, Patent Literature 5, and Patent Literature 6), and the lens barrel and the rotor are integrated. A method (for example, Patent Document 7) is proposed. Among these methods, according to the methods described in Patent Document 4, Patent Document 5, Patent Document 6, and Patent Document 7, it is not necessary to provide a special moving mechanism, and the entire apparatus can be downsized. Since the lens barrel rotates and moves in the front-rear direction, the image may be displaced due to the eccentricity of the lens. On the other hand, according to the methods described in Patent Document 1, Patent Document 2, and Patent Document 3, the rotational force of the rotor is converted into a longitudinal force by a moving mechanism provided between the rotor and the lens barrel. Therefore, by providing a rotation stopper that restricts the movement of the lens in the rotation direction, the lens can be moved in the front-rear direction without rotating, and problems due to the eccentricity of the lens can be avoided.
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

  However, the method described in the above-mentioned patent document is devised for the purpose of being applied to a digital camera or the like of a normal size. , The lens does not drive, and there is a problem that the space for storing the components cannot be taken. For example, when the methods described in Patent Document 1, Patent Document 2, and Patent Document 3 are applied as they are to a small imaging device, there is a problem that it is difficult to take a space for providing a rotation stopper.

  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.

A lens driving device of the present invention that achieves the above object has a cylindrical shape, a stator that forms a magnetic field in the cylindrical shape, and
A rotor that is positioned within the cylindrical shape of the stator and has a cylindrical shape that is coaxial with the cylindrical shape and that is rotationally driven relative to the stator by a magnetic field formed by the stator;
A plurality of small lenses having a relatively small diameter among a plurality of lenses are arranged on the inner side of the cylindrical shape of the rotor and hold a plurality of lenses so that the optical axis of each lens is along the axis of the cylindrical shape. A lens holder positioned at the end of the lens array;
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 rotation retaining mechanism is provided on the side of the small lens to prevent the lens holder from rotating relative to the stator by physical contact.

  According to the lens driving device of the present invention, since the plurality of lenses arranged so that the small lenses come to the end are held by the lens holder, the diameter of the small lens and the lenses other than the small lens are placed on the side of the small lens. A space corresponding to the difference from the diameter is generated. Therefore, even when mounted on a small device such as a cellular phone, a rotation-retaining mechanism can be provided in this space, and a plurality of lenses can be driven with high accuracy while suppressing displacement.

  Further, in the lens driving device of the present invention, 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 meshing with the spiral groove. Preferably it is.

  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, in the lens driving device of the present invention, the rotation retaining mechanism includes a guide and a rail that extend parallel to the optical axis of the lens and fit to each other. One of the guide and the rail is fixed to the lens holder, The other is preferably fixed to the stator.

  Here, “fixed to the lens holder (stator)” may be directly fixed to the lens holder or the stator, or indirectly fixed to the lens holder or the stator. Also good.

  By the guide and rail fixed to the lens holder and the stator, the lens holder is guided in the direction along the optical axis, and the rotation of the lens holder with respect to the stator can be reliably restrained.

An imaging device of the present invention that achieves the above object has a cylindrical shape, a stator that forms a magnetic field in the cylindrical shape, and
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 plurality of small lenses having a relatively small diameter among a plurality of lenses are arranged on the inner side of the cylindrical shape of the rotor and hold a plurality of lenses so that the optical axis of each lens is along the axis of the cylindrical shape. A lens holder positioned at the end of the lens array;
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 rotation retaining mechanism provided on the side of the small lens to prevent the lens holder from rotating relative to the stator by physical contact;
An image pickup mechanism 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 provided in a small device or the like, a plurality of lenses can be accurately driven, and an autofocus function, a zoom function, or the like can be mounted on the small device.

  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.

  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. 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, a lens, and the like, which will be described later, are arranged inside the stator 30. Has been. In addition, the lens holder 20 that holds the lens has a part of the front side meshed with a part of the upper cover 10.

  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 passed through 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 a stator according to the present invention, and the magnet 50 corresponds to an example of a 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 supplied 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, a magnetic field line is generated in the coil 31 and the magnetic field line is 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 1. In this embodiment, the first lens 21 having the smallest diameter among the three lenses is disposed at the end closer 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.

  The first lens 21 has a smaller diameter than the second lens 22 and the third lens 23, and the side of the first lens 21 is wider than the space on the side of the second lens and the third lens. 2 is vacant. The first lens 21 corresponds to an example of a small lens according to the present invention. The lens holder 20 is provided with a spiral groove 20a on the outer surface of the portion holding the second lens 22 and the third lens 23. The outer periphery of the portion holding the first lens 21 is It is in contact with the cover 10.

  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 rotator 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 shown in FIG. 2 is fixed to the stator 30 and is in contact with the outer surface of the portion of the lens holder 20 that holds the first lens 21.

  The lower cover 40 is also fixed to the stator 30, and 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 imaging mechanism 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, the rotational force of the magnet 40 is transmitted to the lens holder 20 by the spiral groove 51a and the spiral groove 20a. However, when the movement of the lens holder 20 in the rotation direction is not restricted, the lens holder 20 rotates and moves back and forth. Since the image is moved in the direction, the image may be displaced due to the eccentricity. In order to prevent such rotation of the lens holder 20, the lens holder 20 and the upper cover 10 are provided with a rotation retaining mechanism. Below, this rotation stop mechanism is demonstrated.

  FIG. 4 is an external perspective view of the upper cover 10, and FIG. 5 is an external perspective view of the lens holder 20.

  A rail 10a is provided on the inner surface of the upper cover 10 shown in FIG. Further, a guide 21b that fits into the rail 10a of the upper cover 10 is provided on the outer surface of the lens holder 20 shown in FIG. When the guide 21b of the lens holder 20 and the rail 10a of the upper cover 10 are fitted to each other, the rotation of the lens holder 20 is prevented. A combination of the guide 21b and the rail 10a corresponds to an example of the rotation-retaining mechanism according to the present invention.

  The rail 10a and the guide 21b are provided in a space 2 on the side of the first lens 21 shown in FIG. This space 2 is a space generated when the diameter of the first lens 21 is smaller than that of the second lens 22 and the third lens 23. By using this space, the small imaging device 1 mounted on a mobile phone or the like. In addition, a rotation retaining mechanism can be provided, and the rotation of the lens holder 20 can be reliably prevented.

  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 spiral groove 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.

  In the above description, an example in which the guide is provided on the lens holder and the rail is provided on the upper cover has been described. It may be provided.

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 an upper cover 10. 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 Rail 20 Lens holder 20a Spiral groove 20b Guide 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 (4)

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;
Positioned further inside the cylindrical shape of the rotor, a plurality of lenses are held side by side so that the optical axis of each lens is along the axis of the cylindrical shape. A lens holder that positions the lens at the end of the array of the plurality of lenses;
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 lens driving device comprising: a rotation retaining mechanism provided on a side of the small lens to prevent the lens holder from rotating relative to the stator by physical contact.   The conversion mechanism includes a spiral groove provided on an inner peripheral surface of the rotor and a spiral groove provided on an outer surface of the lens holder, which meshes with the spiral groove. 2. The lens driving device according to 1.   The rotation retaining mechanism includes a guide and a rail that extend in parallel to the optical axis of the lens and fit to each other. One of the guide and the rail is fixed to the lens holder, and the other of the guide and the rail is fixed to the stator. The lens driving device according to claim 1, wherein the lens driving device is fixed. 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;
Positioned further inside the cylindrical shape of the rotor, a plurality of lenses are held side by side so that the optical axis of each lens is along the axis of the cylindrical shape. A lens holder that positions the lens at the end of the array of the plurality of lenses;
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 rotation retaining mechanism provided on the side of the small lens to prevent the lens holder from rotating relative to the stator by physical contact;
An imaging apparatus comprising: an imaging mechanism that forms an image of subject light that has passed through the lens and acquires image data representing the subject light.

Images