JP2008134300A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus which restrains the action of a shutter from being influenced by leaked magnetic field from an autofocus actuator, and prevents the performance degradation of the shutter without causing cost rise and upsizing. <P>SOLUTION: In the imaging apparatus, a magnetic circuit 50 that is a drive source of a mechanical shutter 17 is separated in a radial direction from a magnetic circuit 40 that is a drive source of the autofocus actuator. Thus, the magnetic circuit 50 is restrained from being influenced by the leaked magnetic field of the magnetic circuit 40, and the action of the mechanical shutter 17 is restrained from being influenced by the leaked magnetic field from the autofocus actuator without causing the cost rise. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus having a magnetic circuit in which an autofocus actuator and a shutter unit are composed of a magnet, a coil, and a yoke, and as a specific example, relates to an image pickup apparatus mounted on a portable electronic device.

  In recent years, a camera built in a portable electronic device has been improved in image quality, and the number of pixels of an image sensor has been increased. In addition, there is a tendency to mount an autofocus function necessary for improving image quality on an imaging device. In order to perform autofocus, it is generally necessary to move an optical system including an internal optical member. Here, as an actuator for driving the optical system, a magnetic circuit using a magnet and a coil is used, and a coil or a voice coil method for driving a magnet is widely used by utilizing an electromagnetic induction phenomenon of the magnetic circuit. It has been.

  On the other hand, in the conventional IT (interline transfer) type image sensor, increasing the number of pixels reduces the readout speed of all pixels, and the influence of light rays entering during the transfer processing of the captured pixels. , Smear and other phenomena occur, resulting in a problem that the image quality deteriorates. In order to prevent this problem, it is necessary to provide a mechanical shutter that mechanically blocks the light entering the image sensor while the pixel transfer process is performed after the photographing is completed.

  As described above, regarding the arrangement when the autofocus mechanism and the mechanical shutter are mounted, the imaging lens can be moved in the optical axis direction as described in Patent Document 1 (Japanese Patent Laid-Open No. 2005-156649). An arrangement of a supporting actuator and a mechanical shutter has been proposed.

  By the way, a problem that occurs in an image pickup apparatus using a voice coil type actuator using an electromagnetic induction phenomenon of an autofocus actuator and a mechanical shutter each having a magnetic circuit including a magnet and a coil will be described below.

  FIG. 9 shows a cross-sectional shape of a main part of a voice coil type actuator generally used for autofocusing of portable devices. This voice coil type actuator has a cylindrical yoke 110, and a cylindrical magnet 111 and a coil 112 are arranged inside the cylindrical yoke 110. The coil 112 is fixed to the optical member holder 120 holding the optical member 121. Then, by passing a current through the coil 112, an electromagnetic induction phenomenon occurs between the magnet 111 and the coil 112, and the optical member holder 120 moves in the arrow direction Z (optical axis direction) in FIG. Here, since it is necessary for the coil 112 and the optical member holder 120 to move the optical member 121 having a relatively large mass at high speed, it is necessary to increase the thrust due to this electromagnetic induction phenomenon. As a result, the magnetic circuit composed of the yoke 110, the magnet 111, and the coil 112 needs to be enlarged.

  As a result, although the magnetic flux leaks around the magnetic circuit, the above-described leakage of magnetic flux does not become a problem when it is not necessary to provide another actuator around the magnetic circuit of the autofocus actuator. On the other hand, when a magnetic circuit of a mechanical shutter, for example, is provided as a magnetic circuit of another actuator around the magnetic circuit of the autofocus actuator, the above-described leakage of magnetic flux becomes a problem.

  As shown in FIG. 8, the magnetic circuit of the mechanical shutter includes a substantially U-shaped yoke 210, a coil 212 wound around the yoke 210, and a cylindrical magnet 211 sandwiched between the yokes 210. And have. The magnet 211 has a rotation shaft 230 that forms a central portion. An arm portion 231 extending from the magnet 211 is connected to the shutter blade 280.

  Here, when the coil 212 is energized, a polarity is generated at the tip of the substantially U-shaped yoke 210, thereby rotating the magnet 211. Along with this, the arm portion 231 rotates around the rotation shaft 230. Then, the shutter blade 280 rotates about the rotation shaft 281 of the shutter blade 280 to the position depicted by the broken line in FIG. 8, and the shutter blade 280 shields the opening 282 of the mechanical shutter holder (not shown). . The shutter blade 280 and the arm 231 are made of resin, and the shutter magnetic circuit formed by the magnet 211, the coil 212, and the yoke 210 is smaller than the magnetic circuit for autofocus shown in FIG. The thrust generated by the magnetic circuit is also smaller than that of the autofocus magnetic circuit.

  Therefore, when both the autofocus actuator of FIG. 9 and the mechanical shutter of FIG. 8 are arranged in the imaging apparatus, the leakage flux of the autofocus actuator of FIG. 9 affects the magnet 211 of the mechanical shutter of FIG. There is a concern that the problem of increasing time or the problem that the mechanical shutter does not operate in some cases may occur.

On the other hand, if a shield member made of a soft magnetic material such as permalloy is inserted between the magnetic circuit of the mechanical shutter and the magnetic circuit of the autofocus actuator in order to reduce the leakage magnetic field, the cost of the imaging apparatus increases. . This is a serious problem when it is assumed that the imaging device is mounted on a mobile phone or the like.
JP 2005-156649 A

  Accordingly, an object of the present invention is to provide an imaging apparatus that can reduce the influence of the leakage magnetic field of the autofocus actuator on the operation of the shutter without increasing the cost and size, and can prevent the shutter performance from degrading. .

In order to solve the above problems, an imaging device of the present invention includes an imaging element, an optical member,
An autofocus actuator that moves the optical member in the optical axis direction and uses a first magnetic circuit including a magnet, a yoke, and a coil as a drive source;
A shutter unit disposed on the subject side of the optical member and having a second magnetic circuit including a magnet, a yoke, and a coil as a drive source;
The second magnetic circuit is separated from the first magnetic circuit in at least the radial direction of an optical axis direction of the optical member and a radial direction orthogonal to the optical axis direction. Yes.

  According to the image pickup apparatus of the present invention, the second magnetic circuit that is the driving source of the shutter unit is radially separated from the first magnetic circuit that is the driving source of the autofocus actuator. As a result, the influence of the leakage magnetic field of the first magnetic circuit on the second magnetic circuit can be reduced, and the influence of the leakage magnetic field from the autofocus actuator on the operation of the shutter unit can be reduced without increasing the cost.

  Therefore, the performance of each drive source of the autofocus actuator and the shutter unit can be sufficiently exhibited. In particular, since the performance of the magnetic circuit of the shutter unit can be sufficiently exhibited, an increase in the closing time of the shutter unit can be suppressed, and the size of the magnetic circuit of the shutter unit can be suppressed. As a result, it is possible to contribute to downsizing of the entire imaging apparatus.

  In the imaging apparatus according to the embodiment, the first magnetic circuit is an annular shape having the optical axis of the optical member as a central axis, and the second magnetic circuit is relative to the first magnetic circuit. Are spaced radially outward, and a radial distance between the first magnetic circuit and the second magnetic circuit is 2 mm to 3 mm.

  According to this embodiment, it is possible to reduce the size while reducing the influence of the leakage magnetic field from the autofocus actuator on the operation of the shutter unit. That is, as shown in FIG. 6, when the radial distance is less than 2 mm, the influence of the leakage magnetic field exerted on the second magnetic circuit by the first magnetic circuit increases rapidly. On the other hand, when the radial distance exceeds 3 mm, the reduction rate of the leakage magnetic field of the first magnetic circuit becomes saturated.

  According to the imaging apparatus of the present invention, since the second magnetic circuit that is the drive source of the shutter unit is radially separated from the first magnetic circuit that is the drive source of the autofocus actuator, the first magnetic circuit The influence of the leakage magnetic field on the second magnetic circuit can be reduced, the influence of the leakage magnetic field from the autofocus actuator on the operation of the shutter part can be reduced without incurring an increase in cost, and the deterioration of the performance of the shutter part can be prevented. .

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 is a perspective view showing a configuration of a main part of an embodiment of the imaging apparatus of the present invention, and FIG. 2 is an exploded perspective view of a main part of this embodiment. Moreover, the principal part cross section of this embodiment is shown in FIG.

  As shown in FIGS. 1 to 3, the imaging apparatus of this embodiment includes optical members 21 </ b> A, 21 </ b> B, and 21 </ b> C, an optical member holder 20 that holds the optical members 21 </ b> A to 21 </ b> C, and an autofocus actuator holder 14. . The optical member holder 20 has an inner member 20A and an outer member 20B. As shown in FIG. 3, a plate spring 13A is disposed between the autofocus actuator holder 14 and the outer member 20B of the optical member holder 20, and the optical member holder 20 is disposed on both sides in the optical axis direction Z with the plate spring 13A. A leaf spring 13B is arranged so as to be sandwiched between the two. The leaf springs 13A and 13B are fixed to the autofocus actuator holder 14. Thus, the leaf springs 13A and 13B support the optical member holder 20 so as to be movable in the optical axis direction Z.

  A cylindrical yoke 10 having a substantially U-shaped cross section is fixed to the inner peripheral surface of the autofocus actuator holder 14. Inside the yoke 10, a cylindrical magnet 11 is fixed to the yoke 10 with an adhesive. A coil 12 is disposed in the gap between the yoke 10 and the magnet 11, and the coil 12 is fixed to the optical member holder 20.

  The yoke 10, the magnet 11, and the coil 12 constitute a first magnetic circuit 40. The first magnetic circuit 40, the autofocus actuator holder 14, the leaf springs 13A and 13B, and the optical member holder 20 constitute an autofocus actuator. The autofocus components including the yoke 10 and the leaf springs 13A and 13B are fixed to the autofocus actuator holder 14.

  In addition, the imaging apparatus converts an image formed by the IR cut glass 60 that forms an infrared cut filter that cuts near-infrared region components of the light beams transmitted through the optical members 21 </ b> A to 21 </ b> C and the optical member 21 into an electrical signal. An image sensor 70. The image sensor 70 is disposed on the image sensor substrate 16 for processing a video signal received by the image sensor 70, and the IR cut glass 60 is disposed on the image sensor 70. The IR cut glass 60 is fixed to the image sensor cover 15 in a through hole formed in the image sensor cover 15. The autofocus actuator holder 14 is disposed on the image sensor cover 15. The image sensor cover 15 is arranged so as to cover the image sensor substrate 16, and positions and fixes the IR cut glass 60 and the autofocus actuator holder 14 with respect to the image sensor 70.

  Furthermore, the imaging apparatus of this embodiment includes a mechanical shutter 17 as a shutter unit that shields light from entering the optical members 21A to 21C during a period in which the imaging element 70 transfers an image signal after the imaging is completed. Yes. The mechanical shutter 17 includes a mechanical shutter holder 18 and a magnetic circuit 50 that is a second magnetic circuit. The mechanical shutter holder 18 has an opening 18A penetrating in the optical axis direction Z. The magnetic circuit 50 of the mechanical shutter 17 includes a substantially U-shaped yoke 210, a coil 212, and a yoke, coil, and magnet similar to the cylindrical magnet 211 shown in FIG. The mechanical shutter 17 has the same shutter blades 280, a rotation shaft 281, an arm portion 231 and a rotation shaft 230 as those shown in FIG. Therefore, the mechanical shutter 17 performs the same operation as described above with reference to FIG.

  As shown in FIG. 3, the magnetic circuit 50 of the mechanical shutter 17 is separated from the magnetic circuit 40 of the autofocus actuator in the radial direction. In this embodiment, the magnetic field generated by the magnetic circuit 50 is smaller than the magnetic field generated by the magnetic circuit 40. In this embodiment, the magnetic circuit 40 has an annular shape with the optical axis J of the optical members 21 </ b> A to 21 </ b> C as a central axis, and the magnetic circuit 50 is spaced radially outward from the magnetic circuit 40.

  In this embodiment, the magnetization direction of the magnet 11 of the magnetic circuit 40 is the direction of the arrow X shown in FIG. That is, the magnet 11 of the magnetic circuit 40 generates a radial magnetic field perpendicular to the optical axis J of the optical members 20A to 20C. When a current is passed through the coil 12, the coil 12 receives a force in the optical axis direction due to electromagnetic induction, and thus a thrust force that moves the optical member holder 20 to which the coil 12 is fixed in the optical axis direction is generated. The position of the optical member holder 20 in the optical axis direction is held by a balance between the thrust by the electromagnetic induction and the elastic force by the leaf springs 13A and 13B. Therefore, the amount of movement of the optical member holder 20 in the optical axis direction is proportional to the value of current flowing through the coil 12.

  Next, the leakage magnetic flux of the magnetic circuit 40 that is a drive source of the autofocus actuator will be described with reference to FIGS.

  4 is a cross-sectional view corresponding to the cross-sectional view of FIG. 3. In FIG. 4, the optical axis J is the Z-axis, and an axis that is orthogonal to the optical axis J and passes through the upper end of the yoke 10 (the end in the optical axis direction). It is described as the X axis. The intersection of the X axis and the Z axis is the origin O. A point, B point, and C point on the Z axis represent positions of 1 mm, 2 mm, and 3 mm from the origin O, respectively. Here, the origin O is the center of the magnetic circuit 40 in the radial direction orthogonal to the optical axis J. In FIG. 4, straight lines LA, LB, and LC are straight lines extending in a direction parallel to the X axis from points A, B, and C, respectively.

  FIG. 6 shows the distribution of leakage magnetic flux of the magnetic circuit 40 in the X-axis direction from the positions of points A, B, and C on the Z-axis in FIG. In FIG. 6, the vertical axis represents the magnetic flux density (T) of the leakage magnetic flux, and the horizontal axis represents the X-axis coordinate (distance (mm) from the optical axis J to the radial direction). In FIG. 6, the characteristic K1 represents the magnetic flux density distribution on the straight line LA extending from the point A in the direction parallel to the X axis, and the characteristic K2 represents the magnetic flux density distribution on the straight line LB extending from the point B in the direction parallel to the X axis. The characteristic K3 represents the magnetic flux density distribution on the straight line LC extending from the point C in the direction parallel to the X axis. In FIG. 6, a broken line L <b> 1 represents the position of the radially outer end of the yoke 10.

  As shown in FIG. 6, the leakage magnetic flux density decreases in the order of characteristics K1, K2, and K3, and the leakage magnetic flux density decreases as the distance from the upper end of the yoke 10 in the optical axis direction increases. In addition, the peak of the leakage magnetic flux density of each characteristic K1, K2, K3 exists inward in the radial direction from the position L1 of the radial outer end of the yoke 10, and the magnitude of the peak is the characteristic K3, K2, K1. It becomes larger in order. Each peak waveform has a characteristic K2 sharper than the characteristic K3, a characteristic K1 sharper than the characteristic K2, and the peak waveform of the leakage magnetic flux density becomes sharper as it approaches the upper end of the yoke 10.

  On the other hand, in FIG. 5, a straight line parallel to the optical axis J and passing through the radially outer end of the yoke 10 is defined as the Z1 axis, and a straight line orthogonal to the Z1 axis and passing through the lower end of the yoke 10 is defined as the X1 axis. The point where the Z1 axis and the X1 axis intersect is the origin O1. The E point, F point, and G point on the X1 axis represent positions of 1 mm, 2 mm, and 3 mm from the origin O1, respectively. Here, the origin O <b> 1 represents the position of the radially outer end and the lower end of the yoke 10. In FIG. 5, straight lines LE, LB, and LC are straight lines extending in a direction parallel to the Z1 axis from points E, F, and G, respectively. A broken line L11 extends from the upper end of the yoke 10 in parallel with the X1 axis.

  FIG. 7 shows the distribution of the leakage magnetic flux of the magnetic circuit 40 in the direction parallel to the optical axis from the positions of the points E, F, and G on the X1 axis in FIG. In FIG. 7, the vertical axis represents the magnetic flux density (T) of the leakage magnetic flux, and the horizontal axis represents the X1-axis coordinates (distance (mm) from the Z1 axis in the radial direction). In FIG. 7, characteristic K11 represents the magnetic flux density distribution on the straight line LE extending from the point E in the direction parallel to the Z1 axis, and characteristic K12 represents the magnetic flux density distribution on the straight line LF extending from the point F in the direction parallel to the Z1 axis. The characteristic K13 represents the magnetic flux density distribution on the straight line LG extending from the point G in the direction parallel to the Z1 axis. In FIG. 7, a broken line L <b> 11 represents the position of the upper end of the yoke 10.

  As shown in FIG. 7, the leakage magnetic flux density decreases in the order of characteristics K11, K12, and K13, and the leakage magnetic flux density decreases as the distance from the radially outer end of the yoke 10 increases in the radial direction. Each of the characteristics K11, K12, and K13 has no peak in the range from the lower end of the yoke 10 (Z1 coordinate is 0 (mm)) to the upper end of the yoke 10 (Z1 coordinate is 3.5 (mm)).

  Referring to FIG. 6, as shown by the characteristic K1 at a position 1 mm away from the upper end of the yoke 10 in the optical axis direction, the position about 1 mm inward from the radially outer end of the yoke 10 toward the optical axis. As a result, the leakage magnetic flux is at the maximum value (about 0.082 (T)). On the other hand, as shown by the characteristic K11 in FIG. 7, the maximum value of the leakage magnetic flux is about 0.046 (T) at a position 1 mm away from the radially outer end of the yoke 10 radially outward. .

  Further, as shown by the characteristic K2 in FIG. 6, at a position 2 mm away from the upper end of the yoke 10 in the optical axis direction, a position about 1.5 mm inward from the radially outer end of the yoke 10 toward the optical axis. As a result, the leakage magnetic flux becomes the maximum value (about 0.04 (T)). On the other hand, as indicated by the characteristic K12 in FIG. 7, the maximum value of the leakage magnetic flux is about 0.025 (T) at a position 2 mm away from the radial outer end of the yoke 10 radially outward. .

  Further, as shown by the characteristic K3 in FIG. 6, at a position 3 mm away from the upper end of the yoke 10 in the optical axis direction, a position about 2.2 mm inward from the radially outer end of the yoke 10 toward the optical axis. As a result, the leakage magnetic flux is the maximum value (about 0.025 (T)). On the other hand, as shown by the characteristic K13 in FIG. 7, the maximum value of the leakage magnetic flux is about 0.013 (T) at a position 3 mm away from the radial outer end of the yoke 10 radially outward. .

  That is, from the characteristic diagrams of FIGS. 6 and 7, in order to reduce the influence of the leakage magnetic flux from the magnetic circuit 40 of the autofocus actuator, the magnetic circuit 50 is more radial than the magnetic circuit 50 is separated in the axial direction. It can be seen that it is advantageous to separate them.

  For example, referring to the characteristic K2 in FIG. 6, even if the magnetic circuit 40 is separated from the magnetic circuit 40 by 2 mm in the Z-axis direction, the range is not separated from the magnetic circuit 40 in the radial direction (X direction) (X is 6.8 mm or less). ) In order to reduce the leakage magnetic flux density to 0.03 (T) or less, it is necessary to arrange the magnetic circuit 50 within 3 mm from the optical axis J, which causes difficulty in arrangement. On the other hand, referring to the characteristic K12 in FIG. 7, if the magnetic circuit 50 is separated from the magnetic circuit 40 by 2 mm in the radial direction (X1-axis direction), the leakage magnetic flux density is at any position in the optical axis direction. Can be made 0.03 (T) or less.

  Therefore, as in this embodiment, by separating the magnetic circuit 50 of the mechanical shutter 17 in the radial direction from the magnetic circuit 40 of the autofocus actuator, a magnetic shield made of a soft magnetic material such as permalloy with a small separation dimension. The influence of the leakage magnetic flux from the magnetic circuit 40 can be reduced without inserting a material. Therefore, according to this embodiment, the drive performance of the mechanical shutter 17 by the magnetic circuit 50 can be sufficiently exhibited while suppressing the increase in size and cost of the imaging device and the complexity of the structure, and the increase in the shutter closing time of the mechanical shutter 17 can be achieved. Performance degradation and malfunction can be prevented.

  Referring to the characteristics K1 and K2 in FIG. 6, when the radial distance of the magnetic circuit 50 from the magnetic circuit 40 is less than 2 mm, the distance between the magnetic circuit 40 and the magnetic circuit 50 in the optical axis direction. Is 1 mm to 2 mm, the influence of the leakage magnetic field exerted on the magnetic circuit 50 by the magnetic circuit 40 increases rapidly. On the other hand, when the radial separation dimension exceeds 3 mm, the reduction rate of the leakage magnetic field of the magnetic circuit 40 is saturated. Therefore, in order to reduce the size while reducing the influence of the leakage magnetic field from the autofocus actuator on the operation of the mechanical shutter 17, the separation distance of the magnetic circuit 50 radially outward from the magnetic circuit 40 is set to 2 mm to 3 mm. It is more desirable to do. Note that the magnetic circuit 50 of the mechanical shutter 17 may be spaced apart from the magnetic circuit 40 of the autofocus actuator both in the optical axis direction and in the radial direction.

  The imaging device of the present invention can be applied to all devices such as cameras mounted on portable devices, and it is possible to suppress degradation of the performance of the mechanical shutter due to the influence of the leakage magnetic field of the autofocus actuator. Become.

It is a perspective view which shows the structure of the principal part of embodiment of the imaging device of this invention. It is a principal part disassembled perspective view of the said embodiment. It is principal part sectional drawing of the said embodiment. It is a schematic diagram explaining the leakage magnetic field distribution measurement position immediately above the magnetic circuit 40 shown in FIG. It is a schematic diagram explaining the leakage magnetic field distribution measurement position of the side of the magnetic circuit 40 shown in FIG. It is a figure which shows the measurement result of the leakage magnetic field distribution in the measurement position shown in FIG. It is a figure which shows the measurement result of the leakage magnetic field distribution in the measurement position shown in FIG. It is a figure which shows the structure of the principal part of the magnetic circuit of a mechanical shutter. It is a figure which shows the structure of the conventional autofocus actuator.

Explanation of symbols

10 yoke 11 magnet 12 coils 13A, 13B leaf spring 14 autofocus actuator holder 15 image sensor cover 16 image sensor substrate 17 mechanical shutter 20 optical member holders 21A to 21C optical member 40 first magnetic circuit 50 magnetic circuit 60 of mechanical shutter 17 IR cut Glass 70 Image sensor

Claims (2)

An image sensor;
An optical member;
An autofocus actuator that moves the optical member in the optical axis direction and uses a first magnetic circuit including a magnet, a yoke, and a coil as a drive source;
A shutter unit disposed on the subject side of the optical member and having a second magnetic circuit including a magnet, a yoke, and a coil as a drive source;
The second magnetic circuit is separated from the first magnetic circuit in at least the radial direction of an optical axis direction of the optical member and a radial direction orthogonal to the optical axis direction. An imaging device. The imaging apparatus according to claim 1,
The first magnetic circuit is annular with the optical axis of the optical member as a central axis,
The second magnetic circuit is spaced radially outward from the first magnetic circuit,
An imaging apparatus, wherein a radial distance between the first magnetic circuit and the second magnetic circuit is 2 mm to 3 mm.

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