Patent Grant
10423006
The present invention relates to a technique for reducing magnetic noise generated by a coil of an image shake correction device.
Various imaging devices have been proposed each having an image shake correction mechanism for reducing an image blur on an image formation surface caused by a camera shake when capturing still images or moving images. In particular, the optical image shake correction mechanism can be considered to have a highly effective camera shake correction effect. A general optical image shake correction mechanism detects shaking of the optical axis caused by the camera shake or the like by means of a vibration gyroscope sensor, etc., and moves an image shake correcting action unit such as a correction lens in the imaging lens so as to cancel the detected shaking of the optical axis. In order to move the image shake correcting action unit, electromagnetic force generated by supplying a current to a coil arranged opposite to a permanent magnet is used.
However, when a current flows through the coil of the image shake correction device, a magnetic field is generated. This magnetic field leaks to an imaging element, such as a CMOS image sensor or its surrounding circuit mounted on an imaging device and is superimposed on an image signal as magnetic noise to deteriorate the image quality. As a method for suppressing the magnetic noise generated by a coil of the image shake correction device, for example, Japanese Patent Application Laid-Open No. 2015-34912 proposes a configuration in which an electromagnetic wave shielding member is disposed on an imaging element side of a flexible printed board that supplies a current to the coil.
In order to cover the camera shake correction coil with the electromagnetic shielding member, it is necessary to secure the path of light from an object passing through the imaging optical system while maintaining the camera shake correction function. Therefore, it is difficult to completely cover the camera shake correction coil with the electromagnetic shielding member, and even when the electromagnetic shielding member described in Japanese Patent Application Laid-Open No. 2015-34912 is used, the leakage of the magnetic field generated by the coil of the image shake correction device cannot be sufficiently prevented. In particular, when a highly sensitive imaging element is used, there has been a problem that the influence of noise due to the leakage of the magnetic field cannot be ignored.
According to one aspect of the present invention, there is provided an imaging lens including: a lens; an image shake correcting action unit provided movably in a direction perpendicular to an optical axis of the lens; a stationary unit for supporting the image shake correcting action unit; a permanent magnet provided on one of the image shake correcting action unit and the stationary unit and a coil provided on an other; a drive circuit for moving the image shake correcting action unit relative to the stationary unit; a mount section for being connected to an imaging unit having an imaging element; and a conductive member which is nonmagnetically conductive and disposed between the coil and the mount section so as to include a facing surface facing a surface formed by a binding wire of the coil and having a larger area than a surface formed by an inner periphery of the coil.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.
First, with reference to
The imaging lens 100 shown in
The imaging lens 100 has the optical image shake correction mechanism 200 inside. As shown in
The stationary unit 202 has an optical system (lens 111) for collecting the object light to an imaging element provided in an imaging unit (not shown). On the other hand, the correcting action unit 201 has a correction lens 204 for correcting a deviation of the optical axis of the optical system (lens 111), that is, the optical axis of the object light, and is disposed on the optical axis of the object light so as to be movable in a direction perpendicular to the optical axis. Magnet units 210 and 220 are provided on one of the correcting action unit 201 and the stationary unit 202, and coils 231 and 232 are provided on the other. For example, in
As shown in
When the imaging device is held in the normal position, the magnet units 210 and 220 are located below the center of the correction lens 204, and symmetrically arranged in the horizontal direction with respect to a vertical line Y extending from top to bottom to pass through the center of the correction lens 204. As shown in
As shown in
The correcting-action-unit support 205 and the support 207 are connected to each other by spring or the like (not shown) and are supported by elastic force of the spring. In this case, the coil 231 is provided so as to be close to the magnet unit 210 without contact therewith and so that the surface formed by winding wire of the coil 231 (hereinafter, referred to as a “coil surface”) and the surface of the magnet unit 210 are arranged to face each other. Similarly, the coil 232 is provided so as to be close to the magnet unit 220 without contact therewith and so that the coil surface formed by winding wire of the coil 232 and the surface of the magnet unit 220 are arranged to face each other.
As shown in
The bent portions 302 and 303 are provided along the support 207 as shown in
In this case, although it has been mentioned that a space is provided between the bent portion 303 and the inner casing 102, if the configuration is made so as not to hinder the movement of the image shake correction mechanism 200, a configuration in which the bent portion 303 and the inner casing 102 are in contact with each other or a configuration in which another member is inserted therebetween can be employed. In
In
In addition, the imaging lens 100 according to the present embodiment may also include a lens, which is necessary for adjusting the focal distance, or the like. In the imaging lens 100 according to the present embodiment, the magnet units 210 and 220 are provided in the correcting action unit 201 and the coils 231 and 232 are provided in the stationary unit 202, but not limited thereto, and the configuration only need to move the correcting action unit 201 with respect to the stationary unit 202 relatively. It is also possible to provide the correcting action unit 201 with the coils 231 and 232, and the stationary unit 202 with the magnet units 210 and 220.
Next, the operation of the image shake correction device according to the first embodiment will be more specifically described with reference to
As shown in
Thus, as shown in
As described above, the image shake correction mechanism 200 of the present embodiment has the two magnet units 210 and 220 and the two coils 231 and 232. The correcting action unit 201 is moved relative to the stationary unit 202 by resultant force f3′ of the electromagnetic force f1′ generated between the magnet unit 210 and the coil 231 and the electromagnetic force f2′ generated between the magnet unit 220 and the coil 232. Thus, in order to apply the resultant force in various directions perpendicular to the optical axis of the object light, the magnitude and the phase relationship of the current flowing through the coils 231 and 232 are changed. In the present embodiment, the magnet units 210 and 220 are symmetrically arranged in the horizontal direction with respect to the vertical line Y as shown in
As described above, the correcting-action-unit support 205 end the support 207 are connected by a spring or the like (not shown), and are supported by the elastic force of the spring. Therefore, the drive of the correcting action unit 201 is performed by the resultant force of the weight of the correcting action unit 201, the elastic force of a spring or the like (not shown) and the electromagnetic force generated by the current flowing through the coils 231 and 232.
In the image shake correction mechanism 200 of the present embodiment, the two magnet units 210 and 220 and the two coils 231 and 232 are provided, but the number thereof is not limited to this, and since a necessary number of pieces only have to be prepared for driving the correcting action unit 201, the configuration may have more number of the magnet units and coils.
In addition, the magnet units 210 and 220 and the coils 231 and 232 are disposed below the center of the correction lens 204 in
Although the correcting-action-unit support 205 and the support 207 are connected to each other by a spring or the like (not shown), the supports only have to support the correcting action unit 201, and thus for example, a configuration using electromagnetic force such as force used for driving the correcting action unit 201 or other mechanical mechanisms such as springs may be employed.
Next, referring to
As described above, when a current I flows through the coils 231 and 232 of the image shake correction mechanism 200 to correct the deviation of the optical axis of the object light, a magnetic field is generated from the coils 231 and 232. As shown in
In this case, the eddy current Ie flowing in the facing surface 301 becomes a vortex-state current enclosed in the conductive member 300, and more current flows outside the positions of the conductive member 300 opposed to the inner peripheries of the coils 231 and 232. That is to say, the eddy current flows most at the edge of the facing surface 301. Hence, the facing surface 301 is configured to have at least a larger area than the area formed by the inner peripheries of the coils 231 and 232.
The conductive member 300 is provided with the bent portions 302 and 303 outside the positions of the conductive member 300 opposed to the inner peripheries of the coils 231 and 232. Due to the presence of the bent portions 302 and 303, the edge of the facing surface 301 where the eddy current flows most becomes thicker. As a result, since the thickness of the edge of the facing surface 301 increases, the resistance value at the edge of the facing surface 301 lowers. In addition, a sufficient thickness can be provided also for the skin depth corresponding to the frequency of the eddy current. Thus, by providing the bent portions 302 and 303, more eddy currents flow to generate the magnetic field Bc shown in
As described above, in the image shake correction mechanism 200 of the present embodiment, the magnetic noise generated by the coils 231 and 232 of the image shake correction mechanism 200 is reduced by eddy currents flowing through the conductive member 300. Thus, it is preferable that many of the magnetic fields generated by the coils 231 and 232 are interlinked with the facing surface 301.
The component of the magnetic field on the winding axis in the winding axis direction generated by the coils 231 and 232 becomes smaller as the position in the component becomes farther away from the coil surface formed by the wire wound in the coils 231 and 232. Here, the winding axis means the central axis when the wires of the coils 231 and 232 are wound. It is theoretically known that, for example, the component of the magnetic field on the winding axis in the winding axis direction located at a distance corresponding to the radius of the outer peripheries of the coils 231 and 232 from the coil surface is equal to about ½ of the component of the magnetic field on the winding axle in the winding axis direction located on the coil surface. Therefore, it is preferable that the distance from the coil surfaces of the coils 231 and 232 to the facing surface 301 of the conductive member 300 is smaller (shorter) than the maximum radius of the outer peripheries of the coils 231 and 232. Here, the maximum radius of the outer peripheries of the coils 231 and 232 means the greatest (longest) length from the center to the outer periphery of the coil surface of each of the coils 231 and 232.
In addition, in the image shake correction mechanism 200 of the present embodiment, the bent portions 302 and 303 are provided to increase the thickness of the edge of the facing surface 301 and reduce the resistance value. Thus, a larger amount of eddy current is supplied to reduce the magnetic field interlinked with the facing surface 301. Accordingly, it is preferable that the length L of the bent portions 302 and 303 from the edge of the facing surface 301 shown in
The eddy current flowing in the facing surface 301 has a distribution in which a current flows more where the linking with the coils 231 and 232 is stronger around positions at which the facing surface 301 intersects with the winding axes of the coils 231 and 232. Thus, most of the eddy currents will flow through the facing surface 301 with a width corresponding to the radius of the outer peripheries of the coils 231 and 232. By increasing the thickness of the facing surface 301 to reduce the resistance value, the bent portions 302 and 303 increase the eddy current and reduce the magnetic field interlinked with the facing surface 301.
Hence, in the conductive member 300 of the present embodiment, the length L of the bent portions 302 and 303 is made greater than the minimum radius of the outer peripheries of the coils 231 and 232. Here, the minimum radius of the outer peripheries of the coils 231 and 232 is the smallest (shortest) length from the center to the outer periphery of the coil surface of the coils 231 and 232. As a result, when the thickness of the bent portions 302 and 303 and the thickness of the facing surface 301 are approximately equal to each other, the resistance value of the bent portions 302 and 303 can be made smaller (lower) than the resistance value of the eddy current path of the facing surface 301.
As shown in
As described above, in the conductive member 300 of the present embodiment, the magnetic field generated in the coils 231 and 332 of the image shake correction mechanism 200 and interlinked with the facing surface 301 is canceled by applying a lot of eddy current to the edge including the bent portions 302 and 303. This can reduce the magnetic field reaching the imaging element and suppress the occurrence of image disturbance by the simple structure of the bent portions 302 and 303. The magnetic noise can be reduced by only adding the conductive member 300 having the bent portions 302 and 303 to the existing structure. As a result, it is not necessary to increase the size of the members in order to reduce the magnetic noise, and thus, the magnetic noise can be reduced while the space saving and lightening of the product are dealt with. In addition, the magnetic noise can be reduced without affecting the object light reaching the imaging element, the mechanism for zooming, and the like.
Although an imaging device allowing the removal of the imaging lens from the imaging unit has been described, the present invention can be applied to an imaging device in which the imaging lens and the imaging unit are integrated, and the same effect can be obtained.
In order to confirm the effect of the conductive member 300 of the present embodiment for reducing the magnetic noise, comparative examination between the present embodiment and the conventional configuration was made based on actual measurement. As Example 1 in the comparative examination, the conductive member 300 shown in
As shown in
As shown in
The digital single-lens camera shown in
As shown in
Next, in order to confirm the influence of the length L of the bent portion 302 provided on the conductive member 300 on reduction of the magnetic noise, the length L of the bent portion 302 was changed and a comparative examination was made by simulation.
In Example 2, the length L of a bent portion 302b of the conductive member 300b was varied to compare the magnetic field levels reaching the imaging element, so that the effect of the length L of the bent portion 302b on the reduction of the magnetic noise was examined. The magnetic field simulation for an imaging lens 100b according to Example 2 was performed using a commercially available electromagnetic field simulation (“Maxwell 3D” manufactured by ANSYS).
First, the simulation model with which the magnetic field simulation was conducted is described with reference to
The nonmagnetic conductive member 300b facing the coils 231 and 232 is made of copper. As shown in
The lens outer casing 101b was a cylindrical conductor made of aluminum having a thickness of 1.14 [mm], a length of 56.6 [mm] and an inner diameter of 58.1 [mm]. The lens outer casing 101b is connected to a camera outer casing 401 via a mount section 402. The mount section 402 was a cylindrical conductor composed of SUS304 having a thickness of 9 [mm], a length of 4.2 [mm], and an inner diameter of 40 [mm]. The camera outer casing 401 had a rectangular parallelepiped shape with a height of 65 [mm], a width of 105 [mm], a depth of 25 [mm] and a thickness of 1 [mm]. The camera outer casing 401 was provided with an opening having a diameter of 58 [mm] to which the mount section 402 of the lens outer casing 101b was connected so that the central axis of the opening of the camera outer casing 401 coincided with the central axis of the mount section 402.
In the camera outer casing 401, the observation plane M for observing the magnetic field reaching the position where the imaging element should be disposed was provided, and a GND conductor pattern 403 corresponding to a pattern of a board located on the back surface of the imaging element was provided. The observation plane M had a height of 16 [mm] and a width of 24 [mm] as for its area and was arranged at a distance of 24.4 [mm] from the coils 231 and 232 in the direction parallel to the central axis of the imaging lens 100b. Also, the center point of the observation plane M was positioned on the central axis of the imaging lens 100b. The GND conductor pattern 403 had a height of 26.7 [mm], a width of 36.55 [mm] and a thickness of 0.035 [mm] and arranged at a distance of 3.12 [mm] from the observation plane M in the direction parallel to the central axis of the imaging lens 100b.
In order to carry out the magnetic field simulation, currents of approximately 55 [kHz] and 1 [A] in the same phase were applied to the coils 231 and 232, and the average value of the magnetic field reaching the observation plane M was obtained.
According to the result shown in
As described above, the image shake correction device according to the present embodiment has a nonmagnetic conductive member that is arranged between the coil and the imaging element, that is, between the coil and the mount section, and has a facing surface facing the surface formed by the winding wire of the coil and having a larger area than the surface formed by the inner periphery of coil. The conductive member has a bent portion outside the position opposed to the inner periphery of the coil. With such a configuration, an imaging lens and an imaging device that can reduce the magnetic noise generated by the coil, having a simple configuration can be provided.
Next, an image shake correction device according to a second embodiment of the present invention will be described with reference to
The image shake correction device of the present embodiment has a configuration in which the conductive member 300c shown in
As described above, in the image shake correction device of the present embodiment, the plurality of bent portions of the conductive member are bent in the same direction. With such a configuration, it is possible to save space and miniaturize the product.
Next, an image shake correction device according to a third embodiment of the present invention will be described with reference to
The image shake correction device of the present embodiment is configured to have the conductive member 300d shown in
The conductive member 304d is a rectangular conductor having a width corresponding to the length of the bent portion 302d in the bending direction and a length corresponding to the circumference of the edge on the lens 111 side of a facing surface 301d. The conductive member 305d is a rectangular conductor having a width corresponding to the length of the bent portion 303d in the bending direction and a length corresponding to the circumference of the edge on the opposite side of the facing surface 301d from the lens 111.
The conductive member 304d is bent along the periphery on the lens 111 side of the facing surface 301d and connected to the bent portion 302d provided with the cutouts, at a plurality of positions. The conductive member 305d is bent along the periphery on the opposite side of the facing surface 301d from the lens 111 and connected to the bent portion 303d provided with cutouts, at a plurality of positions. The method for connecting the bent portions 302d and 303d and the conductive members 304d and 305d may be, for example, a method using a screw, or a conductive adhesive or a pressing method using other members.
As described above, the bent portion of the present embodiment has connecting portions having cutouts (bent portions 302d and 303d). And the bent portion has a second conductive member (conductive members 304d and 305d) connected to the connecting portions at a plurality of positions. With such a configuration, the eddy current flowing due to the interlinking of the magnetic field with the facing surface flows also through the second conductive member, and thereby an imaging lens and an imaging device capable of reducing the magnetic noise generated by the coil can be provided.
In addition, in the present embodiment, the surface where the bent portions 302d and 303d and the conductive members 304d and 305d are connected increases in the thickness of the conductor, so that the structure has a lower resistance value and the eddy current can flow more easily. Therefore, according to the present embodiment, even when cutouts are formed in the bent portions 302d and 303d, the magnetic field reaching the imaging element can be reduced. Moreover since the cutouts are provided, the bent portions 302d and 303d can be forced by bending directly without using a die or the like with regard to the creation of the bent portions 302d and 303d along the curved surface of the facing surface 301d.
Incidentally, as more eddy currents flow through the bent portions 302d and 303d and the conductive members 304d and 305d, more magnetic field reduction effect is created. According to the above example, the connection between the bent portions 302d and 303d and the conductive members 304d and 305d is made at a plurality of positions, and the bent portions and the conductive members preferably have further more connecting positions.
Next, an image shake correction device according to a fourth embodiment of the present invention will be described. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.
In the image shake correction device of the present embodiment, the thickness of the facing surface 301 of the conductive member 300 is made thinner than the thickness of the edges of the facing surface 301 where the bent portions 302 and 303 are to be provided. Such a conductive member 300 can be manufactured by applying press work to the conductive member 300 of the above-described embodiment except the edges thereof. For example, when the conductive member 300 is thinned by press work or the like, only the edges of the conductive member 300 are not subjected to press work, so as to keep thickness to the edges to secure edges equivalent to the bent portions 302 and 303 described above. Incidentally, the thick edges created by not performing the press work or the like can be regarded as the bent portions 302 and 303 as they are, or the thick edges of the facing surface 301 may be further provided with the bent portions 302 and 303.
As described above, in the image shake correction device of the present embodiment, the conductive member undergoes press work, and the thickness of the conductive member is thinned leaving the edges as they are. Therefore, a manufacturing method of an image shake correction device which can reduce the magnetic noise generated by the coil can be provided, because the bent portion including the edge of the facing surface has a structure in which more eddy current can easily flow.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computer's or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2016-241955, filed Dec. 14, 2016 which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-241955 | Dec 2016 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 9568743 | Hayashi | Feb 2017 | B2 |
| 20110097062 | Tsuruta | Apr 2011 | A1 |
| 20110286732 | Hosokawa | Nov 2011 | A1 |
| 20160006958 | Iwamatsu | Jan 2016 | A1 |
| 20160178923 | Hayashi | Jun 2016 | A1 |
| Number | Date | Country |
|---|---|---|
| 2015-034912 | Feb 2015 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20180164603 A1 | Jun 2018 | US |
