JP4751688B2 - Lens barrel - Google Patents

Description

  The present invention relates to a lens barrel used in a video camera, a digital still camera, or the like.

  In a lens barrel of a video camera or digital still camera that records a moving image or a still image using an imaging device such as a CCD, a plurality of lens groups are driven in the optical axis direction to perform zooming and focusing operations. As an example of such a lens barrel, a lens configuration of a lens barrel used in a video camera or the like as shown in FIGS. 16 and 17 is known.

  As shown in FIGS. 16 and 17, the lens barrel has a configuration in which the first lens group 17, the second lens group 18, the third lens group 19, and the fourth lens group 13 are arranged in a straight line on the optical axis 15. It has become. 16 and 17, the optical axis direction is the X-axis direction, and the direction perpendicular to the optical axis direction is the Y-axis direction. Specifically, the first lens group 17 and the third lens group 19 are fixed in the direction of the optical axis 15, and the second lens group 18 moves in the direction of the optical axis to perform a zoom operation. That is, FIG. 16 in which the second lens group 18 approaches the first lens group 17 is a case where the shooting field angle is the widest, and FIG. 17 in which the second lens group 18 approaches the third lens group 19 The case where the angle of view is the most telephoto is shown.

  Further, in this lens barrel, the fourth lens group 13 moves in the optical axis direction, and a focusing operation is performed. That is, the fourth lens group 13 moves to an optimal position between the third lens group 19 and the image sensor 16 according to the increase / decrease of the imaging distance to the subject and the position of the second lens group 18 (ie, zoom magnification). Thus, an optical image is correctly formed on the image sensor 16.

  As described above, it is necessary to move the lens group in the optical axis direction in order to perform the zoom operation and the focus operation. As one of means for driving the lens group in the optical axis direction as described above, a stepping motor has been frequently used. The stepping motor is configured to rotate the rotating body by an angle corresponding to a predetermined number of pulses and to stop at a predetermined position. However, the stepping motor has problems such as the stop position accuracy is poor because the drive control system is an open loop, there is a hysteresis characteristic, and the rotational speed is relatively low. For this reason, the moving speed of the lens group to be driven, that is, the zoom speed and the focus speed are slowed, and the user's operational feeling is remarkably impaired. In addition, if the moving speed of the fourth lens group 13 that performs the focusing operation is not sufficiently high, there is a problem that the photographed image is blurred. As the second lens group 18 moves, it is necessary to move the fourth lens group 13 to a predetermined position, so this problem becomes more prominent as the zoom speed is increased. If the moving speed of the second lens group 18 is increased in order to improve the user's feeling of zoom operation, the time lag until the fourth lens group 13 moves to an appropriate position increases, and the image is blurred during the zoom operation. Occurs.

  Therefore, in order to improve the movement responsiveness of the lens group, a voice coil type linear motor is used as a lens driving device (see, for example, Patent Documents 1 to 3). A lens barrel using a linear motor will be described with reference to FIGS. 18 is a perspective view of the lens barrel, FIG. 19 is a schematic plan view of the lens barrel as seen from the image sensor side, and FIG. 20 is a schematic side view of the lens barrel as seen from the side. In any figure, only the part which comprises a linear motor is drawn. Further, FIG. 20 illustrates a state in which the movable frame 8 is closest to the image sensor 16. 18 to 20, the optical axis direction is the X-axis direction, the magnetizing direction is the Y-axis direction, and the direction perpendicular to the X-axis and the Y-axis is the Z-axis direction.

  The third lens group 19 is fixed to the third group frame 29 by adhesion or heat caulking, and the third lens group 19 is correctly positioned on the optical axis 15 by attaching the third group frame 29 to the fixed frame 5. . The third group frame 29 does not move in the optical axis direction.

  The magnet 1 is attached to a U-shaped main yoke 2. The main yoke 2 is fixed to the fixed frame 5 by press-fitting protrusions 12. A part of the main yoke 2 passes through the coil 4 that is bonded and fixed to the movable frame 8 on which the fourth lens group 13 is mounted. The open end of the main yoke 2 is closed by the side yoke 3, and the main yoke 2 and the side yoke 3 constitute a magnetic circuit. Then, by increasing or decreasing the current flowing through the coil 4, an appropriate driving force in the optical axis direction is generated in the coil 4 and the fourth lens group 13 is moved in the optical axis direction. A control circuit (not shown) reads the output of the magnetic sensor 7 and increases / decreases the current flowing through the coil 4 to control the position of the fourth lens group 13 in the optical axis direction with high accuracy.

  Since the magnetic sensor 7 detects a change in the magnetic field in the X-axis direction generated by the magnetic scale 6, it is necessary to suppress the influence of a disturbance magnetic field flowing into the magnetic sensor 7. For this reason, in the conventional lens barrel, the magnetic sensor 7 is arranged near the center of the magnetic flux distribution in the optical axis direction so as not to be affected by the magnetic flux generated from the main yoke 2. For example, as shown in FIG. 20, the center of the magnet 1 and the center of the magnetic sensor 7 may be arranged substantially in a straight line in the magnetizing direction of the magnet 1. Note that the center of the magnetic sensor 7 is not limited to the position shown in FIG. 20, and may be arranged near the center of the magnetic flux distribution (see, for example, Patent Document 4).

  On the other hand, since digital still cameras have become explosively widespread, the number of pixels of the image sensor 16 has increased rapidly, and a lens barrel having higher optical performance, that is, higher resolution has been demanded. In order to respond to such a demand by improving the optical system shown in FIGS. 16 and 17, the lens barrel becomes large and an expensive glass material is required, leading to an increase in cost. This is because in the lens configuration shown in FIGS. 16 and 17, the first lens group 17 and the third lens group 19 are at fixed positions, and the zoom operation is performed only by the movement of the second lens group 18.

  In view of this, a lens barrel has been proposed that performs a zoom operation by the cooperative operation of the first lens group 17, the second lens group 18, and the third lens group 19. 21 and 22 show examples of the lens configuration of such a lens barrel.

FIG. 21 shows the arrangement of lenses in which the first lens group is closest to the image sensor 16 (moves to the negative side in the X-axis direction) and the third lens group 19 is farthest from the second lens group 18, that is, the shooting field angle is The widest case is shown. FIG. 22 shows an arrangement of lenses in which the first lens group moves to the position farthest from the image sensor 16 (moves to the X axis direction positive side) and the third lens group 19 comes closest to the second lens group 18. That is, the case where the shooting angle of view is the most telephoto is shown. As is apparent from FIGS. 21 and 22, in this lens barrel, the zoom operation is performed by the cooperative operation of the first, second and third lens groups. Therefore, a lens barrel with higher optical performance can be provided without increasing the size of the lens barrel.
Japanese Patent Laid-Open No. 11-150972 Japanese Patent Laid-Open No. 11-215795 JP 2000-241694 A JP 2000-266984 A

  The focusing operation of the lens barrel shown in FIGS. 21 and 22 is performed by moving the fourth lens group 13 in the optical axis direction, similarly to the lens barrel of FIGS. 16 and 17. In the lens barrels of FIGS. 16 and 17, since the third lens group 19 is fixed, the movement amount 20 of the fourth lens group 13 in the optical axis direction is relatively small. On the other hand, in the lens barrel of FIGS. 21 and 22, since the third lens group 19 is moved by the zoom operation, the movement amount 20 of the fourth lens group 13 in the optical axis direction is the lens mirror shown in FIGS. 2-4 times larger than the cylinder. That is, in the lens barrel shown in FIGS. 21 and 22, it is necessary to operate the fourth lens group 13 at a higher speed than the lens barrel shown in FIGS. Therefore, in the lens barrels of FIGS. 21 and 22, a linear motor capable of high-speed operation is used.

  However, when the linear motor having the conventional configuration shown in FIGS. 18 to 20 is designed to be used as it is, it is necessary to extend the length of the magnet 1 and the main yoke 2 in the optical axis direction as shown in FIG. There is. Then, as is apparent from FIG. 23, when the movable frame 8 comes closest to the image sensor 16, the magnetic scale 6 largely protrudes toward the image sensor 16 in the optical axis direction (X-axis direction in FIG. 23). 5 must be provided with a protrusion 21. As a result, the lens configuration shown in FIGS. 21 and 22 is adopted to avoid an increase in the size of the lens barrel. On the contrary, the axial dimension of the lens barrel increases as the protruding portion 21 protrudes.

  An object of the present invention is to reduce the size of a lens barrel on which a linear motor is mounted.

The lens barrel according to claim 1 is provided such that at least one lens constituting at least a part of the imaging optical system, a fixing member, and the lens are fixed and movable relative to the fixing member in the optical axis direction. A moving member, a magnet provided on the fixed member and magnetized in a direction perpendicular to the optical axis direction, a yoke provided on the fixed member and arranged to face the magnet in a direction perpendicular to the optical axis direction, A coil provided on the member and arranged so that a current flows in a direction perpendicular to the magnetic flux generated between the magnet and the yoke, a magnetic scale provided on the moving member, and provided on the fixed member and perpendicular to the optical axis direction. And a magnetic sensor arranged to face the magnetic scale in the direction. The yoke includes a yoke main body and a first magnetic field adjusting unit that protrudes from the yoke main body toward the N pole side in the magnetizing direction of the magnet. The magnetic sensor is arranged so as to be shifted in the optical axis direction from the center in the optical axis direction of the magnet. The first magnetic field adjustment unit is disposed on the same side of the optical axis direction of the magnet as the magnetic sensor, and is located farther in the optical axis direction from the center of the optical axis direction of the magnet than the magnetic sensor. Is arranged.

  In this lens barrel, since the yoke has the first magnetic field adjustment portion that protrudes toward the N-pole side in the magnetizing direction of the magnet, a part of the magnetic flux flowing out from the magnet and the yoke to the magnetic sensor side is the first magnetic field. It is drawn to the adjustment unit. That is, the center of the magnetic flux on the magnetic sensor side can be moved to the first magnetic field adjustment unit side in the optical axis direction. As a result, the magnetic sensor can be disposed closer to the first magnetic field adjustment unit in the optical axis direction than in the prior art, and the magnetic scale can be disposed closer to the first magnetic field adjustment unit in the optical axis direction as well. Thereby, it is possible to prevent the magnetic scale from projecting from the moving member to the side opposite to the first magnetic field adjustment unit in the optical axis direction, and it is possible to reduce the size of the lens barrel.

  According to a second aspect of the present invention, in the lens barrel according to the first aspect, the first magnetic field adjusting portion further protrudes from the yoke body in a direction perpendicular to the optical axis direction and perpendicular to the magnetizing direction of the magnet.

  In this lens barrel, since the first magnetic field adjustment unit protrudes also in the direction perpendicular to the magnetizing direction of the magnet, the area of the surface perpendicular to the optical axis direction of the first magnetic field adjustment unit increases. As this area increases, the effect of moving the center of the magnetic flux in the optical axis direction also increases. Therefore, in this lens barrel, a part of the magnetic flux flowing out from the magnet and the yoke to the magnetic sensor side is attracted by the first magnetic field adjustment unit, and the magnetic sensor can be arranged on the first magnetic field adjustment unit side in the optical axis direction. it can.

  A lens barrel according to a third aspect is the lens barrel according to the first or second aspect, wherein the first magnetic field adjustment unit is at least one plate-like member. The plate thickness direction of the first magnetic field adjustment unit is the same as the optical axis direction.

  In this lens barrel, since the plate thickness direction of the first magnetic field adjustment unit is the same as the optical axis direction, the area of the surface perpendicular to the optical axis direction can be increased. Thereby, the center of magnetic flux can be moved to the optical field direction 1st magnetic field adjustment part side more reliably.

The lens barrel according to claim 4 is provided such that at least one lens constituting at least a part of the imaging optical system, a fixing member, and the lens are fixed and movable relative to the fixing member in the optical axis direction. A moving member, a magnet provided on the fixed member and magnetized in a direction perpendicular to the optical axis direction, and a yoke provided on the fixed member and arranged to face the magnet in a direction perpendicular to the optical axis direction; A coil provided on the moving member and arranged so that a current flows in a direction perpendicular to the magnetic flux generated between the magnet and the yoke, a magnetic scale provided on the moving member, and an optical axis direction provided on the fixed member. And a magnetic sensor arranged to face the magnetic scale in a vertical direction. The yoke includes a yoke main body and a first magnetic field adjusting unit that protrudes from the yoke main body in at least one of the direction perpendicular to the optical axis direction and perpendicular to the magnet magnetization direction. The first magnetic field adjustment unit is at least one plate-like member. The plate thickness direction of the first magnetic field adjustment unit is the same as the optical axis direction. The magnetic sensor is arranged so as to be shifted in the optical axis direction from the center in the optical axis direction of the magnet. The first magnetic field adjustment unit is disposed on the same side of the optical axis direction of the magnet as the magnetic sensor, and is located farther in the optical axis direction from the center of the optical axis direction of the magnet than the magnetic sensor. Is arranged.

  In this lens barrel, since the yoke has the first magnetic field adjustment unit, a part of the magnetic flux flowing out from the magnet and the yoke to the magnetic sensor side is attracted to the first magnetic field adjustment unit. That is, the center of the magnetic flux on the magnetic sensor side can be moved to the first magnetic field adjustment unit side in the optical axis direction. And since the plate | board thickness direction of a 1st magnetic field adjustment part is the same as an optical axis direction, the area of a surface perpendicular | vertical to an optical axis direction can be taken large. As a result, the magnetic sensor can be disposed closer to the first magnetic field adjustment unit in the optical axis direction than in the prior art, and the magnetic scale can be disposed closer to the first magnetic field adjustment unit in the optical axis direction as well. Thereby, it is possible to prevent the magnetic scale from projecting from the moving member to the side opposite to the first magnetic field adjustment unit in the optical axis direction, and it is possible to reduce the size of the lens barrel.

  A lens barrel according to a fifth aspect is the lens barrel according to any one of the first to fourth aspects, wherein the magnetic sensor is disposed in a direction in which the first magnetic field adjustment unit protrudes from the magnet.

  In this lens barrel, the magnetic sensor can be arranged in a range in which the center of the magnetic flux largely moves in the optical axis direction. That is, the effect of the first magnetic field adjustment unit can be maximized. Thereby, a magnetic sensor can be arrange | positioned more to the optical axis direction 1st magnetic field adjustment part side.

  A lens barrel according to a sixth aspect is the lens barrel according to any one of the first to fifth aspects, wherein the first magnetic field adjustment unit is disposed at an end of the yoke body in the optical axis direction.

  In this lens barrel, since the first magnetic field adjustment unit is disposed at the end of the yoke body in the optical axis direction, the center of the magnetic flux can be reliably moved in the optical axis direction.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the lens barrel further includes a second magnetic adjustment portion that protrudes from the yoke body toward the S pole in the magnetizing direction of the magnet.

In this lens barrel, since the yoke further includes the second magnetic adjustment unit, the center of the magnetic flux can be moved in the optical axis direction. In this case, the amount of movement of the center of the magnetic flux is substantially equal to the total amount of movement by the first and second magnetic field adjustment units .

  In the lens barrel according to the present invention, since the magnetic body has the first and second magnetic adjustment portions, the center of the magnetic field on the magnetization direction magnetic sensor side can be moved in the axial direction. The arrangement of the magnetic scale can be moved in the axial direction. As a result, the magnetic scale can be prevented from protruding in the axial direction from the moving member, and the lens barrel can be reduced in size.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

1. 1st Embodiment The lens-barrel 50 as 1st Embodiment of this invention is demonstrated using FIGS. FIG. 1 is a schematic side view of a lens barrel 50 as a first embodiment of the present invention, FIG. 2 is a schematic plan view of a lens barrel 50 as a second embodiment of the present invention, and FIG. FIG. 4 is a schematic perspective view of the main components, and FIG. 4 is a visualization diagram of the magnetic field analysis result in the XY plane at the center in the width direction (Z-axis direction) of the main yoke 2. 1-4, the optical axis direction is the X-axis direction, the magnetization direction of the magnet 1 is the Y-axis direction, and the direction perpendicular to the X-axis and the Y-axis is the Z-axis direction. In the X axis, Y axis, and Z axis, the direction of the arrow in the figure is the positive side, and the opposite direction is the negative side. The N pole side of the magnetizing direction of the magnet 1 is the Y axis direction positive side, and the S pole side is the Y axis direction negative side. 1 to 4, the same reference numerals are used for the same configuration as the lens barrel 50 shown in FIGS. 12 to 23.

  As shown in FIGS. 1 to 3, the lens barrel 50 includes a fixed frame 5 (fixed member), a movable frame 8 (moving member), a magnet 1, a main yoke 2 (magnetic body), and a side yoke 3. (Magnetic material), a coil 4, a magnetic scale 6, and a magnetic sensor 7 are provided.

  The fixed frame 5 is a box-shaped member that is open on one side in the optical axis direction, and accommodates each member therein. The movable frame 8 is a member to which the fourth lens group 13 is fixed, and is provided so as to be movable in the optical axis direction with respect to the fixed frame 5. Specifically, the movable frame 8 has bearing portions 10a and 10b, and is movable in the optical axis direction by two guide poles 9a and 9b provided on the fixed frame 5 and penetrating the bearing portions 10a and 10b. It is supported by.

  The magnet 1, the main yoke 2 and the side yoke 3 are for constituting a magnetic circuit and are attached to the fixed frame 5. Specifically, the main yoke 2 is a U-shaped magnetic material, and is fixed inside the fixed frame 5 by a pair of press-fitting protrusions 12 protruding in the Z-axis direction. Inside the main yoke 2, the magnet 1 is fixed by adsorption or adhesive. The magnet 1 is magnetized in the Y-axis direction, and is arranged to face a part of the main yoke 2 in the Y-axis direction. The side yoke 3 is fixed to the open end of the main yoke 2. The coil 4 is fixed to the movable frame 8 with an adhesive, and a part of the main yoke 2 penetrates the coil 4 in the X-axis direction. The coil 4 is arranged so that a current flows in a direction perpendicular to the magnetic flux generated between the magnet 1 and the main yoke 2. The coil 4, the magnet 1, and the main yoke 2 are movable in the X-axis direction.

  Further, as shown in FIG. 1, the side yoke 3 has a first magnetic field adjustment unit 11 a that protrudes toward the Y-axis direction magnetic sensor 7 side (Y-axis direction positive side). The first magnetic field adjustment unit 11a is a plate-like member that extends further from the end surface (upper surface) on the Y axis direction positive side of the main yoke 2 to the Y axis direction positive side. The plate thickness direction of the first magnetic field adjustment unit 11a is the same as the X-axis direction. That is, the surface perpendicular to the X-axis direction of the first magnetic field adjustment unit 11a is wide. In the present embodiment, the first magnetic field adjustment unit 11a is formed by extending a conventional side yoke to the Y axis direction positive side. The first magnetic field adjustment unit 11a has the same width as the main yoke 2 and the side yoke 3 in the Z-axis direction, but has a width larger than the width of the main yoke 2 and the side yoke 3, for example. May be.

  The magnetic scale 6 and the magnetic sensor 7 are for detecting the displacement of the movable frame 8 in the X-axis direction. Specifically, the magnetic scale 6 is fixed to the movable frame 8 with an adhesive or the like so as to extend in the X-axis direction. The magnetic sensor 7 is fixed to the fixed frame 5 so as to face the magnetic scale 6 in the magnetization direction. On the surface of the magnetic scale 6 facing the magnetic sensor 7, S and N poles are alternately magnetized at a predetermined pitch along the X-axis direction in FIG. Detects changes in the axial magnetic field.

  In general, the magnetization pitch of the magnetic scale 6 is as extremely narrow as about 200 to 300 μm, and the change in the magnetic field to be detected by the magnetic sensor 7 is also extremely small. For this reason, in order to accurately detect a minute magnetic field change, the magnetic sensor 7 is an MR element (magnetic thin film) made of a ferromagnetic thin film such as NiFe or NiCo having a characteristic that the resistance value changes according to the magnetic field change. Magnetoresistive element) is used. The MR element can detect a slight change in the magnetic field, and the output of the magnetic scale 6 can be obtained in a sine wave field. Therefore, even if the moving range of the magnetic scale 6 becomes long, the position can be detected with the same accuracy. .

  If the change of the magnetic field in the X-axis direction of the magnetic scale 6 can be detected by the magnetic sensor 7, the position in the X-axis direction of the movable frame 8 and the fourth lens group 13 that move together with the magnetic scale 6 can be detected. . Then, the position of the fourth lens group 13 in the X-axis direction can be controlled with high accuracy by increasing or decreasing the current passed through the coil 4 by control means (not shown) based on the output of the magnetic sensor 7.

  However, in order to enable such highly accurate control, it is necessary to suppress the influence of a disturbance magnetic field jumping into the magnetic sensor 7. In order to suppress the influence of the disturbance magnetic field, it is necessary to arrange the magnetic sensor 7 at the magnetic center position (the center position of the X-axis direction distribution of the magnetic flux jumping out of the yoke). Here, the magnetic center position in the lens barrel 50 of the present invention will be described.

  FIG. 4 shows a visualization diagram of the magnetic field analysis result in the XY plane at the center of the main yoke 2 in the width direction (Z-axis direction). In FIG. 4, many arrows indicate the direction of magnetic flux. The distribution state of the X-axis direction component Bx of the magnetic flux is shown as curves 14, 14a, 14b. A curve 14 indicates a position where the X-axis direction component Bx becomes zero, that is, a magnetic center position. A curve 14a indicates a position corresponding to the positive allowable limit of the external magnetic field Bx allowable by the magnetic sensor 7, and a curve 14b indicates a position corresponding to the negative allowable limit.

  Comparing the direction of the arrow and the state of the curves 14, 14a, and 14b with FIG. 25 of the conventional example, it can be seen that the magnetic flux jumping out from the upper surface of the main yoke 2 is drawn toward the first magnetic field adjusting unit 11a. This is because the side yoke 3 has the first magnetic field adjustment unit 11a protruding from the upper surface of the main yoke 2 to the Y axis direction positive side, and is perpendicular to the X axis direction of the first magnetic field adjustment unit 11a. This is because the surface is wide. That is, the first magnetic field adjusting unit 11a can make the distribution state of the magnetic flux from the main yoke 2 toward the magnetic sensor 7 asymmetric in the X-axis direction of FIG. 4, that is, the X-axis direction. In this case, the arrangement of the magnetic sensor 7 can be moved to the first magnetic field adjustment unit 11a side (positive side) in the X-axis direction. As a result, the magnetic sensor 7 can be disposed on the first magnetic field adjustment unit 11a side in the X-axis direction with respect to the movable frame 8.

  Furthermore, it can be seen that the distance in the X-axis direction between the curve 14a and the curve 14b in FIG. 4 is significantly larger than that in the conventional example (FIG. 25). This is because the first magnetic field adjustment unit 11a protrudes in the direction from the magnet 1 toward the magnetic sensor 7, so that the magnetic flux protruding from the upper surface of the main yoke 2 is relatively close to the magnetic sensor 7 and the first magnetic field adjustment unit 11a. This is because the amount of change in the magnetic flux in the optical axis direction in the vicinity of the magnetic center position has become smaller as a result of being attracted by The magnetic sensor 7 can be provided at any position as long as it is between the X axis direction of the curve 14a and the curve 14b indicating the allowable limit. Therefore, as shown in FIG. 4, the magnetic sensor 7 can be further shifted from the curve 14 indicating the magnetic center position to the X axis direction positive side. As a result, as shown in FIG. 1, the position of the magnetic scale 6 with respect to the magnet 1 can also be moved in the X-axis direction, so that the magnetic scale 6 does not protrude to the negative side in the X-axis direction, and a part of the fixed frame 5 It is not necessary to provide the protrusion 21 as shown in FIG. As described above, by providing the first magnetic field adjustment unit 11a, the size of the lens barrel 50 in the optical axis direction can be shortened, and the lens barrel 50 can be downsized.

  Further, since the first magnetic field adjustment unit 11a only has to extend the side yoke 3 in the direction from the magnet 1 to the magnetic sensor 7, the number of parts does not increase and the number of assembly steps does not increase. In addition, as a material used when manufacturing the side yoke 3, a relatively inexpensive iron plate (SECC material, SPCC material) or the like is used, so that the effects as described above can be obtained with almost no change in component costs. Can do.

  In addition, the deviation | shift amount of a magnetic center position (curve 14) and the variation | change_quantity of magnetic flux (interval of the curve 14a and the curve 14b) can be adjusted by changing the protrusion amount to the Y-axis direction of the 1st magnetic field adjustment part 11a. Therefore, the design according to the configuration of the lens barrel is possible. Further, when the first magnetic field adjustment unit 11a protruding to the Y axis direction negative side is provided on the side yoke 3, the magnetic center is shifted to the X axis direction negative side. In the first embodiment, the first magnetic field adjustment unit 11a is provided in a part of the side yoke 3, but may be provided integrally with the main yoke 2, or another part may be added. In this case, since the magnetic center position and the amount of change in the magnetic flux change according to the position of the first magnetic field adjustment unit 11a in the X-axis direction, the dimensions of the first magnetic field adjustment unit 11a are adjusted to adjust the size of the lens barrel. Design according to the configuration is possible.

  Further, as shown in FIGS. 5A and 5B, the width of the first magnetic field adjustment unit 11a does not need to match the yoke width, and by increasing or decreasing this width, the shift amount of the magnetic center position or The amount of change in magnetic flux can be adjusted. If the protrusion amount of the first magnetic field adjustment unit 11a to the Y axis direction positive side is the same, the magnetic center can be further shifted to the X axis direction positive side as the width of the first magnetic field adjustment unit 11a becomes wider. Further, when the area of the first magnetic field adjustment unit 11a at a position close to the magnetic sensor 7 when viewed in the Y-axis direction is increased / decreased, the area becomes larger due to the shift amount of the magnetic center position and the change amount of the magnetic flux. Even when the width of the first magnetic field adjustment unit 11a in the Z-axis direction is wider than the width of the main yoke 2 as shown in FIGS. 5A and 5B, it is better to increase the area on the Y-axis direction positive side as much as possible. Therefore, even if a shape in which the width of the first magnetic field adjustment unit 11a gradually increases toward the Y axis direction positive side is obtained, a preferable result can be obtained.

  The relationship between the shape and area of the first magnetic field adjustment unit 11a, the magnetic center position, and the amount of magnetic flux change can be easily evaluated using a magnetic field analysis such as a finite element method or a commercially available magnetic force meter called a gauss meter. . FIG. 6 shows the measurement result of the magnetic flux component Bx in the X-axis direction at the center in the width direction (Z-axis direction) of the main yoke 2 using a gauss meter. The mark 31 is the actual measurement result for the conventional example shown in FIGS. 19 and 24, and the mark 32 is the actual measurement result for the lens barrel 50 of the first embodiment shown in FIGS. A dotted line 33 indicates the magnetic field analysis result of FIG. 25, and a solid line 34 indicates the magnetic field analysis result of FIG.

  As shown in FIG. 6, it can be seen that the actual measurement result and the magnetic field analysis result agree very well. It can be seen that the X-intercept of the solid line 34 in FIG. 6 is the magnetic center position as the first embodiment, and is shifted to the left side in FIG. Moreover, the inclination of the solid line 34 is smaller than the inclination of the dotted line 33, and it can also be seen that the amount of change in the X-axis direction magnetic flux component Bx is small. As described above, since the distribution state of the magnetic flux component Bx in the X-axis direction can be measured only by using a commercially available magnetic force measuring device, the shape of the first magnetic field adjustment unit 11a is changed, and the magnetic center position and the magnetic flux change amount are in an optimum state. Can be.

  Moreover, as a modification of this embodiment, the case as shown in FIGS. 7-9 is also considered. FIG. 7 is a schematic side view of a lens barrel as a modification of the first embodiment of the present invention when viewed from the side. FIG. 8 shows a lens barrel as a modification of the first embodiment of the present invention from the image sensor side. FIG. 9 is a schematic plan view, and FIG. 9 is a schematic perspective view of main components constituting a linear motor as a modification of the first embodiment of the present invention.

  In this modification, as shown in FIGS. 7 to 9, the magnet 1, the main yoke 2 (magnetic material), the side yoke 3 (magnetic material), and the coil 4 are rotated about the optical axis (X axis). It is arranged in a rotated state. In this case, by providing the side yoke 3 with the first magnetic field adjusting portion 11a that protrudes to the Y axis direction positive side from the side surface of the main yoke 2, the distribution state of the magnetic flux from the magnet 1 and the main yoke 2 toward the magnetic sensor 7 can be changed. Asymmetrical in the X-axis direction. As a result, as shown in FIG. 7, the arrangement of the magnetic sensor 7 can be moved to the first magnetic field adjustment unit 11a side (positive side) in the X-axis direction. Accordingly, the magnetic sensor 7 can be disposed on the first magnetic field adjustment unit 11 a side in the X-axis direction with respect to the movable frame 8.

  As described above, the main function of the first magnetic field adjustment unit 11a is to draw the magnetic flux that jumps out of the magnet 1 in the optical axis direction. The effect of attracting the magnetic flux is further increased when the area of the plane perpendicular to the X axis (that is, the plane perpendicular to the optical axis direction and the drive direction of the linear motor 60) is large. That is, the shape of the first magnetic field adjustment unit 11a protrudes in a direction perpendicular to the optical axis direction (more specifically, the N-pole side in the magnetizing direction of the magnet 1 and the direction perpendicular to the magnetizing direction of the magnet 1). It is important that the thickness direction of the first magnetic field adjustment unit 11a is the same as the optical axis direction. Therefore, for example, as shown in FIG. 10A, the magnet 1 protrudes in the N pole side in the magnetization direction and in a direction perpendicular to the magnetization direction, or as shown in FIG. The same effect can be obtained even when the magnet 1 does not project toward the N pole side but projects in one direction perpendicular to the magnet 1 magnetizing direction. Moreover, when the 1st magnetic field adjustment part 11a protrudes to both rather than one of the directions perpendicular | vertical to the magnetizing direction of a magnet, the effect of attracting magnetic flux becomes higher compared with one case. Furthermore, the effect of attracting the center of the magnetic flux can be further enhanced by combining the first magnetic field adjustment unit 11a shown in FIGS. 3, 5, 9, and 10.

2. Second Embodiment A lens barrel 50 according to a second embodiment of the present invention will be described with reference to FIGS. 11, 12, and 13. FIG. 11 is a schematic side view of a lens barrel as a second embodiment as viewed from the side, FIG. 12 is a schematic perspective view of main components constituting the linear motor, and FIG. 13 is a width direction (Z-axis direction) of the main yoke 2. The visualization figure of the magnetic field analysis result in XY plane in the center is shown. In the following description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIGS. 11 and 12, in the lens barrel 50 in the second embodiment, the side yoke 3 has the same shape as the conventional example. And the main yoke 2 has the 2nd magnetic field adjustment part 11b on the lower surface. The second magnetic field adjusting unit 11b is a plate-like member extending from the main yoke 2 in the X-axis direction protruding to the S pole side in the magnetizing direction of the magnet 1, that is, the Y-axis direction negative side. The plate thickness direction of the second magnetic field adjustment unit 11b faces the Y-axis direction and is perpendicular to the optical axis direction. The distribution state of the magnetic flux flowing into the lower surface of the main yoke 2 is biased to the X axis direction negative side by the second magnetic field adjustment unit 11b as shown in FIG. In this way, the magnetic center position moves to the Y axis direction negative side on the lower surface of the main yoke 2, so that the magnetic center position of the magnetic flux from the upper surface of the main yoke 2 toward the magnetic sensor 7 also moves to the Y axis direction positive side by the reaction. Moving. That is, even if the second magnetic field adjustment unit 11b is provided instead of the first magnetic field adjustment unit 11a, the same effect as in the first embodiment can be obtained. The second magnetic field adjustment unit 11b is a plate-like member extending in the X-axis direction. Since the thickness direction of the second magnetic field adjustment unit 11b is perpendicular to the optical axis direction, the second magnetic field adjustment unit 11b protrudes from the main yoke 2 in the Y-axis direction. The size of the portion to be performed is small, and interference with peripheral members can be prevented.

  The second magnetic field adjustment unit 11b may be manufactured integrally with the main yoke 2 or may be attached to the main yoke 2 after being manufactured as a separate part. The second magnetic field adjusting portion 11b in the case of separate parts may be made of the same material as that of the main yoke 2 and the side yoke 3, and the manufacturing cost is relatively low if a material such as an iron plate (SECC material, SPCC material) is used. Can be suppressed. Further, the second magnetic field adjusting unit may be made of a material different from that of the main yoke 2 and the side yoke 3 and using permalloy (iron-nickel alloy) with high magnetic permeability, electromagnetic soft iron with high saturation magnetic flux density, or permendur. The area occupied by 11b can be reduced.

  The second magnetic field adjustment unit 11 b fixes the magnet 1 to the main yoke 2, and then attracts and fixes the magnet 1 to the main yoke 2 by the magnetic force of the magnet 1. After that, if the main yoke 2 is fixed to the fixed frame 5 using the press-fitting projections 12, the external magnetic field adjusting portion 11 is surrounded by the fixed frame 5 as shown in FIG. There is no need to do. The second magnetic field adjustment unit 11b may be fixed to the main yoke 2 or the fixed frame 5 with an adhesive or the like.

3. Third Embodiment A lens barrel 50 as a third embodiment of the present invention will be described with reference to FIGS. 14 and 15. FIG. 14 is a schematic side view of a lens barrel as a third embodiment as viewed from the side, and FIG. 15 is a visualization diagram of magnetic field analysis results in the XY plane at the center in the width direction (Z-axis direction) of the main yoke 2. . In the following description of the third embodiment, the same reference numerals are used for the same configurations as those in the first and second embodiments, and descriptions thereof are omitted.

  The lens barrel 50 of the third embodiment has both the first magnetic field adjustment unit 11a and the second magnetic field adjustment unit 11b. By providing the 1st magnetic field adjustment part 11a and the 2nd magnetic field adjustment part 11b, compared with the case where each is provided independently, a magnetic center position can be moved more largely. This is apparent from the state of magnetic flux distribution in FIG.

  Here, also in the above-mentioned patent document 3, the point which moves a magnetic center position by making a part of yoke protrude is described. Therefore, the lens barrel according to the present invention and the lens barrel described in Patent Document 3 are compared.

  First, the protrusion 36a of Patent Document 3 protrudes from the yoke 36 in the Z-axis direction, while the first magnetic field adjustment unit 11a and the second magnetic field adjustment unit 11b of the lens barrel 50 protrude in the Y-axis direction. That is, the protrusion directions of the two protrusions are completely different. In addition, it is considered that at least the first magnetic field adjustment unit 11a has a larger effect of moving the magnetic center position than the protrusion 36a of Patent Document 3. This is because, as can be seen from a comparison between FIG. 4 and FIG. 13, the first magnetic field adjustment unit 11a disposed on the Y-axis direction magnetic sensor side is disposed on the opposite side. This is because the effect of moving the magnetic center position is greater than that of 11b. This is related to the protruding direction and the arrangement of the protrusions. Further, as is clear from this embodiment, by providing both the first magnetic field adjustment unit 11a and the second magnetic field adjustment unit 11b, the magnetic center position can be moved more greatly than when each of them is provided alone. Can do. As described above, the lens barrel according to the present invention is completely different from the lens barrel according to the present invention in the direction in which the protrusion protrudes and the arrangement thereof, and the magnetic center position is moved more greatly. It can be said that it has.

  Thereby, as shown in FIG. 14, the position of the magnetic scale 6 with respect to the magnet 1 can also be moved further in the optical axis direction, so that the magnetic scale 6 does not protrude to the negative side in the X-axis direction. Conversely, since the concave portion 23 can be provided in a part of the fixed frame 5, the axial dimension of the lens barrel 50 can be further shortened, and the lens barrel 50 can be further reduced in size.

  In the lens barrel according to the present invention, the magnetic center position can be shifted from the center of the magnet simply by providing the first magnetic field adjustment unit and the second magnetic field adjustment unit on the yoke, and the amount by which the magnetic scale projects in the optical axis direction. Can be reduced. Thereby, the dimension of the lens barrel in the optical axis direction can be shortened. That is, the lens barrel according to the present invention is useful in general optical equipment such as a video camera and a digital still camera.

1 is a schematic side view of a lens barrel as a first embodiment of the present invention viewed from the side. 1 is a schematic plan view of a lens barrel as a first embodiment of the present invention as viewed from an image sensor side. The schematic perspective view of the main components which comprise the linear motor as 1st Embodiment of this invention. The visualization figure of the magnetic field analysis result in the lens-barrel as 1st Embodiment of this invention. The schematic perspective view of the main components which comprise the linear motor which shows the other application example as 1st Embodiment of this invention. The comparison figure of the measurement result and magnetic field analysis result of an optical axis direction magnetic flux component as 1st Embodiment of this invention. The side surface schematic diagram which looked at the lens barrel as a modification of 1st Embodiment of this invention from the side. The plane schematic diagram which looked at the lens barrel as a modification of a 1st embodiment of the present invention from the image sensor side. The schematic perspective view of the main components which comprise the linear motor as a modification of 1st Embodiment of this invention. The schematic perspective view of the main components which comprise the linear motor as a modification of 1st Embodiment of this invention. The side schematic diagram which looked at the lens barrel as a 2nd embodiment of the present invention from the side. The schematic perspective view of the main components which comprise the linear motor as 2nd Embodiment of this invention. The visualization figure of the magnetic field analysis result in the lens-barrel as 2nd Embodiment of this invention. The side schematic diagram which looked at the lens barrel as a 3rd embodiment of the present invention from the side. The visualization figure of the magnetic field analysis result in the lens-barrel as 3rd Embodiment of this invention. FIG. 6 is a schematic side view showing a lens configuration of a conventional lens barrel. FIG. 6 is a schematic side view showing a lens configuration of a conventional lens barrel. The disassembled perspective view of the linear motor periphery part of the conventional lens barrel. FIG. 6 is a schematic plan view of a conventional lens barrel viewed from the image sensor side. The side schematic diagram which looked at the conventional lens barrel from the side. FIG. 6 is a schematic side view showing a lens configuration of a conventional lens barrel. FIG. 6 is a schematic side view showing a lens configuration of a conventional lens barrel. The side schematic diagram which looked at the conventional lens barrel from the side. The schematic perspective view of the main components which comprise the conventional linear motor. The visualization figure of the magnetic field analysis result in the conventional lens barrel.

DESCRIPTION OF SYMBOLS 1 Magnet 2 Main yoke 3 Side yoke 4 Coil 5 Fixed frame 6 Magnetic scale 7 Magnetic sensor 8 Movable frame 11a 1st magnetic field adjustment part 11b 2nd magnetic field adjustment part 13 4th lens group 50 Lens barrel

Claims (7)

At least one lens constituting at least part of the imaging optical system;
A fixing member;
A moving member provided with the lens fixed and movable relative to the fixed member in an optical axis direction;
A magnet provided on the fixing member and magnetized in a direction perpendicular to the optical axis direction;
A yoke provided on the fixing member and arranged to face the magnet in a direction perpendicular to the optical axis direction;
A coil provided on the moving member and arranged so that a current flows in a direction perpendicular to the magnetic flux generated between the magnet and the yoke;
A magnetic scale provided on the moving member;
A magnetic sensor provided on the fixing member and arranged to face the magnetic scale in a direction perpendicular to the optical axis direction;
The yoke includes a yoke body and a first magnetic field adjustment unit that protrudes from the yoke body to the N pole side in the magnetizing direction of the magnet .
The magnetic sensor is arranged to be shifted in the optical axis direction from the center in the optical axis direction of the magnet,
The first magnetic field adjustment unit is disposed on the same side of the optical axis direction as the magnetic sensor with respect to the center of the magnet in the optical axis direction. It is arranged at a position far in the axial direction,
Lens barrel. The first magnetic field adjustment unit further protrudes from the yoke body in at least one of a direction perpendicular to the optical axis direction and a direction perpendicular to the magnetization direction of the magnet.
The lens barrel according to claim 1. The first magnetic field adjustment unit is at least one plate-like member,
The thickness direction of the first magnetic field adjustment unit is the same as the optical axis direction.
The lens barrel according to claim 1 or 2. At least one lens constituting at least part of the imaging optical system;
A fixing member;
A moving member provided with the lens fixed and movable relative to the fixed member in an optical axis direction;
A magnet provided on the fixing member and magnetized in a direction perpendicular to the optical axis direction;
A yoke provided on the fixing member and arranged to face the magnet in a direction perpendicular to the optical axis direction;
A coil provided on the moving member and arranged so that a current flows in a direction perpendicular to the magnetic flux generated between the magnet and the yoke;
A magnetic scale provided on the moving member;
A magnetic sensor provided on the fixing member and arranged to face the magnetic scale in a direction perpendicular to the optical axis direction;
The yoke includes a yoke body and a first magnetic field adjustment unit that protrudes from the yoke body in at least one of a direction perpendicular to the optical axis direction and perpendicular to the magnetizing direction of the magnet,
The first magnetic field adjustment unit is at least one plate-like member,
The thickness direction of the first magnetic field adjustment unit is the same as the optical axis direction ,
The magnetic sensor is arranged to be shifted in the optical axis direction from the center in the optical axis direction of the magnet,
The first magnetic field adjustment unit is disposed on the same side of the magnetic sensor as the optical axis with respect to the center of the magnet in the optical axis direction. It is arranged at a position far in the axial direction,
Lens barrel. The magnetic sensor is disposed in a direction in which the first magnetic field adjustment unit protrudes with respect to the magnet.
The lens barrel according to claim 1. The first magnetic field adjustment unit is disposed at an end in the optical axis direction of the yoke body.
The lens barrel according to any one of claims 1 to 5. The yoke further includes a second magnetic adjustment unit that protrudes from the yoke body toward the south pole in the magnetizing direction of the magnet.
The lens barrel according to claim 1 .

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