Lens barrel

[0059] (Example 1)

[0060] Hereinafter, the lens barrel according to Embodiment 1 of the present invention will be described by referring to FIGS. 1 to 6. Fig. 1 is a schematic perspective view of a lens barrel according to Embodiment 1 of the present invention. The lens barrel includes a linear actuator and a stepping motor. Figure 2 is a schematic diagram of a beam of magnetic flux leaking from the lens barrel. Fig. 3 is a graph of magnetoresistance change characteristics of an MR element. Fig. 4 is a schematic perspective view of a position detecting part equipped with an MR element. Figure 5 is a schematic diagram of a beam of magnetic flux leaking to a stepping motor with an encoder. Figure 6 It is a schematic diagram of a beam of magnetic flux leaking to the magnetic sensor according to Embodiment 1 of the present invention.

[0061] A focus lens moving frame 31 holds a focus lens group 30, which points in parallel to an optical axis. The focus lens moving frame 31 smoothly moves in one optical axis direction (X direction) along the guide posts 32a and 32b, and the end (not shown) of the guide post is fixed on the lens barrel. A fixing member 34 on the linear actuator 33 is mounted on the lens barrel to drive the focus lens moving frame 31 along the optical axis. The fixing member 34 includes a main magnet 35 whose magnetization direction is perpendicular to the driving direction (X direction), a U-shaped main yoke 36 and a plate-shaped side yoke 37.

[0062] A magnetic circuit 38 including the fixing member 34 is laterally symmetrical when viewed from one driving direction, and is substantially laterally symmetrical when viewed from the other driving direction (X direction). A moving member 39 of the actuator 33 includes a coil 40, and the coil is fixed to the focus lens moving frame 31 in such a way that a predetermined gap can be created between the coil 40 and the magnetic head 35. Electric current is supplied to the coil 40 and flows in a direction perpendicular to the magnetic flux generated by the magnetic head 35. In this way, the focus lens moving frame 31 is driven to move in the optical axis direction.

[0063] In order to control the position of the focus lens moving frame 31, a magnetic sensor 41 used as a position detection device is mounted on the fixed side in the lens barrel, and the magnetic sensor is located at a center where the magnetic circuit 38 is viewed from a driving direction (X direction). The time is symmetrical around the center, and the magnetic sensor is also located at a center where the magnetic circuit 38 is symmetrical around the center when viewed from another driving direction. A magnetic mark 42 containing alternating N poles and S poles is mounted on the focus lens moving frame 31 and is separated from the detection surface on the facing magnetic sensor 41 by a predetermined distance. The magnetic sensor 41 is a two-phase magnetoresistive sensor including MR elements 43a and 43b made of ferromagnetic thin films. The MR elements 43a and 43b are arranged at a certain interval along the driving direction, and the interval is equal to 1/4 of the interval between the N pole and the S pole. The magnetic sensor 41 and the magnetic mark 42 are installed such that the direction of current flowing through the MR elements 43a and 43b is perpendicular to the magnetization direction of the magnetic head 35.

[0064] Next, a position detection method using the magnetic sensor 41 will be described. Regarding the directionality of the magnetoresistance change shown in Figure 3, the magnetoresistance change is independent of the magnetic field in the direction perpendicular to the current direction of the MR elements 43a and 43b and perpendicular to the detection surface (the Y direction); the magnetoresistance mainly depends on the direction perpendicular to the MR The current direction of the elements 43a and 43b is parallel to the magnetic field in the direction (X direction) of the detection surface; the magnetoresistance changes slightly with respect to the magnetic field in the direction parallel to the current direction of the MR elements 43a and 43b (the Z direction).

[0065] Due to this characteristic, when the magnetic mark 42 having the magnetization pattern shown in FIG. 4 changes its position relative to the magnetic sensor 41, the magnetic resistance of the MR elements 43a and 43b will change as the magnetic field of the sine wave pattern in the X direction changes. Although a sine wave mode magnetic field change with a phase difference of 180° from the X direction also occurs in the Y direction, due to the above-mentioned characteristics, the magnetic resistance of the MR elements 43a and 43b does not change significantly. Therefore, when the voltage applied to the MR elements 43a and 43b is used as an output signal, the output signal has two sine waves with a phase difference of 90°. These two sine waves are subjected to modulation and interpolation processing in a signal processing circuit (not shown) to determine the position and driving direction of the lens moving frame 31. Based on these data, the position of the focus lens group 30 can be controlled with high precision by a control circuit (not shown).

[0066] However, in order to obtain a high-precision linear actuator, it is necessary to suppress the external interference magnetic field from entering the magnetic sensor 41. When the external disturbance magnetic field appears in the linear actuator 33 along the optical axis direction (X direction), the external disturbance magnetic field is superimposed on the change in the magnetic field intensity of the sine wave mode. In this way, the signal wave will shift, thereby distorting the waveform of the output signal. This will lead to increased error in position detection. Although the sensitivity of magnetoresistance change is small in a direction orthogonal to the optical axis direction (Z direction), the rate of change of magnetoresistance is reduced, and thus the sensitivity of the MR element is lowered.

[0067] Therefore, it is necessary to prevent the linear actuator 33 from being affected by the external disturbance magnetic field, especially the main magnet 35 in the X and Z directions.

[0068] As described above, by installing the magnetic sensor 41 in the center of the magnetic circuit 38, magnetic flux leakage can be reduced. As shown in FIG. 2(a), the MR elements 43a and 43b have the property of changing magnetoresistance in the X and Z directions. Since the magnetic circuit 38 is substantially symmetrical with respect to one driving direction (X direction), the magnetic sensor 41 located at the center of symmetry has a small amount of magnetic flux leakage along the X direction. In addition, as shown in FIG. 2(b), since the magnetic circuit 38 is substantially symmetrical with respect to the other driving direction, the magnetic flux leakage along the Z direction of the magnetic sensor 41 located at the center of symmetry is small. As described above, optimizing the position of the magnetic sensor 41 will result in a reduction in magnetic flux leakage.

[0069]The stepping motor 47 with an encoder will be described below, which is used to drive a zoom lens group 45 to move along the optical axis direction.

[0070] The stepping motor 47 with encoder includes a stepping motor 48, a screw 49 combined with the rotation shaft of the stepping motor, a sensing magnet 50 with alternating N poles and S poles, and a pair of the sensing magnet 50 A fixed magnetic sensor 51 for angle detection. Please note that in FIG. 1, the sensing magnet 50 and the magnetic sensor 51 are covered by a cover 51 a for fixing the magnetic sensor 51. For the screw 49, a zoom lens moving frame 46 holding the zoom lens group 45 is connected with a screw 52 engaged with the screw 49.

[0071] In this way, by rotating the screw 49, the zoom lens group 45 can be moved linearly in the X-axis direction. The system CPU (not shown) of the stepping motor with encoder is used to calculate the angle information of the rotating shaft and an electric phase angle information according to the count value of an electric phase counter. The CPU will calculate a drive command value based on the angle information and the electrical phase angle information. The stepper motor 47 with an encoder will be controlled by the excitation current of an exciter.

[0072] However, when the magnetic sensor 51 of the stepping motor 47 with an encoder is affected by an external disturbance magnetic field, the output of the magnetic sensor 51 is distorted, similar to the magnetic sensor 41 of the linear actuator 33. The performance of the actuator will decrease. Please note that for the magnetic sensor 41 of the linear actuator 33, the magnitude limit of the external disturbance magnetic field is about 10 Gauss. Compared with the limit of the external disturbance magnetic field of the linear actuator 33, the limit of the magnetic sensor 51 of the stepper motor 47 with encoder is smaller. Part of the reason is that the sensing magnet 50 is cylindrical and the surface of the magnetic sensor is smaller. flat.

[0073] The encoder-equipped stepping motor 47 is less affected by the external interference magnetic field from the magnet 48a of the stepping motor 48. Nevertheless, since the lens barrel is small, the distance between the stepping motor 47 and the linear actuator 33 is short. In particular, the stepping motor 47 is easily affected by the main magnet 35 of the linear actuator 33. Therefore, in the stepping motor 47 with an encoder, the magnetic sensor 51 needs to be installed in such a position so that the magnetic sensor 51 is not easily affected by the external interference magnetic field. This situation will be described below.

[0074] When the magnetic sensor 51 is installed in the position shown in FIGS. 5 and 6 in the stepping motor 47 with an encoder, it is necessary to suppress the external interference magnetic field in two directions, namely, the tangential (Z direction) and the direction of rotation of the magnetic sensor 50 The current direction of the magnetic sensor 51 (X direction). The magnetic sensor 51 of the stepping motor 47 with encoder is installed based on the following principle. Since the magnetic circuit 38 of the linear actuator 33 is laterally symmetric when viewed from one driving direction, the magnetic sensor 51 located at the center of symmetry basically cannot detect the magnetic flux leakage in the Z direction. Similarly, since the magnetic circuit 38 of the linear actuator 33 is substantially laterally symmetric when viewed from another driving direction, the magnetic sensor 51 located at the center of symmetry basically cannot detect the magnetic flux leakage in the X direction. In this way, the magnetic sensor 51 of the stepping motor 47 with an encoder will not be affected by the external interference magnetic field, thereby realizing a high-precision actuator system.

[0075] As described above, according to Embodiment 1, it is possible to provide a system including a stepping motor with an encoder for zooming and a linear actuator for focusing, instead of a system using an ordinary stepping motor. Therefore, the zoom function can have a transmission speed of approximately 30-2000 pps (pulse per second). Therefore, ultra high speed and ultra low speed zoom can be achieved. Thus, a high-performance lens barrel and a video camera using the lens barrel can be obtained.

[0076] In addition, when closed-loop control is used, the rotation angle and torque can be controlled to achieve low energy consumption and low noise. For focusing, by using a magnetic sensor, in addition to high response performance, high resolution and high accuracy can also be obtained, thereby achieving excellent focusing performance. In addition, only by arranging the magnetic sensor in the above manner, the external interference magnetic field can be reduced. Therefore, unlike the conventional method, it is not necessary to use components such as a shield, thereby achieving low cost and preventing the lens barrel from increasing in size due to the addition of space for accommodating such components. Therefore, a small and light-weight lens barrel can be obtained.

[0077] Needless to say, if the polarities of the main magnets of the set of linear actuators in Embodiment 1 shown in FIGS. 2, 5, and 6 are reversed, the same effect can be obtained.

[0078] In the linear actuator of Embodiment 1, the magnetic sensor is installed in the lens barrel on the fixed side, and the magnetic mark is installed on the lens moving frame on the moving side. Alternatively, the magnetic mark can be installed in the lens barrel on the fixed side, and the magnetic sensor can be installed on the lens moving frame on the moving side. In this case, needless to say, the same effect can be obtained.

[0079] Although a magnetoresistive magnetic sensor with MR elements is used in Embodiment 1, any type of magnetic sensor can be used as long as it can input and output a signal corresponding to the intensity of magnetic force.

[0080] (Example 2)

[0081] Next, a second embodiment of the present invention will be described by referring to FIGS. 7 to 9. Fig. 7 is a schematic perspective view of a lens barrel according to Embodiment 2 of the present invention. The lens barrel includes an image vibration compensation device and a linear actuator. Fig. 8 is a perspective view of key components of the image vibration compensation device. Fig. 9 is a block diagram of an image shake compensation circuit. The parts described above are denoted by the same reference numerals, and their descriptions are omitted.

[0082] The first lens group for compensating for image vibration when taking an image is fixed on a holder 2 that can move in the Z direction shown in FIG. 7. Hereinafter, the holder 2 is referred to as a pitch moving frame 2. By installing a support 2a and a lock pin 2b located on the opposite side of the support 2a, the tilt moving frame 2 can smoothly move through the two tilt axes 3a and 3b. An electromagnetic actuator 6p is also installed under the tilt moving frame 2.

[0083] The electromagnetic actuator 6p includes a coil 7p fixed on the pitch moving frame 2, a magnet 8p, and a yoke 9p mounted on the fixed frame 10 as described later. The yoke 9p has protrusions 9pa on opposite sides. The fixed frame 10 is provided with occlusal holes 10pa capable of engaging the protrusions 9pa, and they are arranged in a direction substantially parallel to the smooth movement of the tilting frame 2. In this way, the yoke 9p is fixed to the fixing frame 10 without an adhesive or the like. One surface of the magnet 8p is magnetized with two poles, and the magnet is fixed to a U-shaped yoke 9p opened on one side.

[0084] A frame 4 for moving the image vibration compensation lens group 1 in the Y direction is mounted on the tilt moving frame 2 on the optical axis imaging plane side. Hereinafter, the holder 4 is referred to as a swing movable frame. The fixing members 4c and 4d are installed in the swing frame 4 on the side of the optical axis object to fix the opposite ends of the two tilt axes 3a and 3b used to drive the tilt frame 2 to move smoothly as described above. Similarly, by installing a support 4a and a lock pin 4b on the opposite side of the support 4a, the swing moving frame 4 can smoothly move through the two swing shafts 5a and 5b. The two rocking shafts 5a and 5b are fixed to the fixed parts 10c and 10d on the fixed frame 10, and the fixed frame 10 is installed on the side of the optical axis imaging plane of the rocking movable frame 4. An electromagnetic actuator 6y is installed on the left side of the swing frame 4.

[0085] The electromagnetic actuator 6y includes a coil 7y fixed on the swing frame 4, a magnet 8y, and a yoke 9y mounted on the fixed frame 10. The yoke 9y has protrusions 9ya on opposite sides. The fixing frame 10 is provided with an occlusal hole 10ya capable of engaging the protruding block 9ya, and the occluding hole 10ya is arranged in a direction substantially parallel to the smooth movement of the swing movable frame 4. In this way, the yoke 9y is fixed to the fixing frame 10 without an adhesive or the like. One surface of the magnet 8y is magnetized with two poles, and the magnet is fixed to a U-shaped yoke 9y with one side open.

[0086] In this way, when current flows through the coil 7p of the pitch moving frame 2, the magnet 8p and the yoke 9p will generate electromagnetic force in the Z direction. Similarly, when current flows through the coil 7y of the swing moving frame 4, the magnet 8y and the yoke 9y will generate electromagnetic force in the Y direction. In this way, the image vibration compensation lens group 1 can be driven by the electromagnetic actuators 6p and 6y to move in two directions substantially perpendicular to the optical axis.

[0087] Next, the position detection section will be described. A detection part 11p mounted on the upper part of the tilting frame 2 in the Z direction includes a light emitting element 12p (such as an LED), a slit 13p, and a light receiving element 14p (PSD) fixed on the PSD substrate 15. Similarly, a detection portion 11y mounted on the upper part of the swing movable frame 2 along the Y direction includes a light emitting element 12y (such as an LED), a slit 13y, and a light receiving element 14y (PSD) fixed on the PSD substrate 15.

[0088] The light emitting elements 12p and 12y emit light beams through the corresponding slits 13p and 13y. The light beams passing through the slits 13p and 13y will enter the corresponding light receiving elements 14p and 14y. In this way, the movement of the image vibration compensation lens group 1 is equal to the movement of the light receiving elements 14p and 14y. The light-receiving elements 14p and 14y will output information about the position where the light beam is incident on their light-receiving surface as two current values. The output value is calculated to determine the position of the lens group 1.

[0089] Next, a flexible printed cable connected between the pitch and swing movable frames 2 and 4 and the fixed frame 10 will be described.

[0090] A flexible printed cable 16 is installed on an upper surface of the tilting frame 2 in a manner to surround the compensation lens group 1. The flexible printed cable 16 is electrically connected between the coil 7p and the light emitting element 12p. The flexible printed cable 16 is fixed to the tilting frame 2 at one location 16b and is oriented perpendicular to the smoothly moving Z direction. The other end 16a of the flexible printed cable 16 is fixed on a part 10e on one side of the fixing frame 10, and the end 16a is parallel to the Z direction in which the tilt moving frame 2 moves smoothly.

[0091] In this way, the coil 7p and the light emitting element 12p are connected to a circuit (not shown) for supplying excitation current. Similarly, a flexible printed cable 17 is installed on one side of the swing moving frame 4. The flexible printed cable 17 is electrically connected between the coil 7y and the light emitting element 12y. The flexible printed cable 17 is fixed on the swing moving frame 4 at one part 17b thereof, and the flexible printed cable 17 is oriented perpendicular to the Y direction of the smooth movement. The other end 17a of the flexible printed cable 17 is fixed to a part 10e on one side of the fixing frame 10, and the end 17a is substantially parallel to the Z direction in which the tilt moving frame 2 moves smoothly. Thus, the coil 7y and the light-emitting element 12y are connected to a circuit (not shown) for supplying excitation current. In this way, the displacement unit 20 for image vibration compensation includes the above-mentioned components.

[0092] In addition, the shift unit 20 has the structure shown in FIG. 8, which shows a shift unit assembly, so that the size of the shift unit is reduced in the diameter direction of the lens. The tilt moving frame 2 and the swing moving frame 4 have different heights along the optical axis direction. The tilt moving frame 2 is installed on the object side of the optical axis. The yoke 9y on the displacement actuator 6y for swing is inserted into the optical axis imaging plane side of the support 2a of the tilt movement frame 2 in such a way that the yoke 9y overlaps the support 2a when viewed from the optical axis direction. Therefore, the size of the displacement unit 20 in the radial direction, that is, the width B, can be reduced, resulting in a reduction in the volume of the displacement unit.

[0093] The operation of the lens barrel thus constructed will be described below.

[0094]The hand movement acting on the camera with the image vibration compensation device will be detected by two angular velocity sensors 21 (not shown) separated by approximately 90° from each other. The output of the angular velocity sensor 21 is integrated with respect to time. The obtained value is converted into a hand shake angle. The generated angle is converted into target position information of the image vibration compensation lens group 1. A servo circuit 22 is used to calculate the difference between the target position information of the image vibration compensation lens group 1 and the current position information, so as to move the image vibration compensation lens group 1 according to the target position information. The resulting difference is transmitted as a signal to the electromagnetic actuators 6p and 6y. The electromagnetic actuators 6p and 6y drive the image vibration compensation lens group 1 based on this signal. The motion of the image vibration compensation lens group 1 will be detected by the position detection parts 11p and 11y and fed back to compensate for the image vibration in the camera.

[0095] The swing frame 4 is driven in the Y direction in the following manner. The current is supplied to the coil 7y through the flexible printed cable 17 in response to an instruction from the drive circuit. The flow of current will cause the electromagnetic actuator 6y to generate a force in the Y direction to drive the swing moving frame 4. The tilting frame 2 is driven in the Z direction in the following manner. The current is supplied to the coil 7p through the flexible printed cable 17 in response to an instruction from the drive circuit. The flow of current will cause the electromagnetic actuator 6p to generate a force in the Z direction to drive the pitch moving frame 2. In this way, the compensation lens group 1 can move arbitrarily in a plane perpendicular to the optical axis, so that the image vibration generated by the hand movement can be compensated.

[0096] As described above, according to Embodiment 2, the pitch and pan movement for moving the compensation lens group in the direction perpendicular to the optical axis is mounted in the lens barrel with the image vibration compensation shift unit. The tilting and swaying movable frames are arranged at different heights relative to the optical axis. The swing frame is installed in such a way that it overlaps the tilt frame when viewed from the direction of the optical axis. Therefore, the size of the shift unit in the width direction can be reduced, thereby achieving a reduction in the volume of the lens barrel with the shift unit.

[0097] (Example 3)

[0098] Next will pass through the reference Figure 10 to 13 The third embodiment of the present invention is described. Picture 10 It is a schematic perspective view of a lens barrel according to Embodiment 3 of the present invention. The lens barrel contains an image vibration compensation device and a linear actuator. Fig. 11 is a schematic structural diagram of a yoke in a linear actuator. Picture 12 It is a schematic diagram of a beam of magnetic flux of the magnet in the displacement actuator of the image vibration compensation device. Figure 13 It is a schematic diagram of a beam of magnetic flux of the magnet in the linear actuator according to the third embodiment of the present invention. The parts described in the foregoing are denoted by the same reference numerals, and their descriptions are omitted.

[0099] The shift unit 20 in Embodiment 3 is the same as that described in Embodiment 2. For simplification, the fixing frame 10 of the displacement unit 20 is omitted in FIG. 11. The pitch magnet 8p, the swing magnet 8y and the magnet 35 of the linear actuator 33 are such as Picture 12 with 13 (a) Shown. The tilt moving frame 2 and the swing moving frame 4 have different heights along the optical axis direction. The tilt moving frame 2 is installed on the side of the optical axis object.

[0100] The main yoke 36 and the side yoke 37 of the linear actuator 33 for driving the focus lens group 30 described in Embodiment 1 are mounted on the optical axis imaging plane side of the yoke 9p of a pitch actuator 6p. FIG. 11 shows a top view of the arrangement structure of the actuators of the displacement unit 20. A magnetic sensor 41 is used as the position detecting portion of the linear actuator 33. As mentioned earlier, the influence of the external interference magnetic field will cause the sensor output to be distorted, resulting in a decrease in the performance of the actuator.

[0101] Therefore, in order to mount the shift unit 20 and the linear actuator 33 in a single lens barrel, it is necessary to reduce the magnetic flux leaking from the shift unit 20 and the linear actuator 33. Although one solution to reduce the magnetic flux leakage is to increase the interval between the shift unit 20 and the linear actuator 33, this will result in an increase in the volume of the lens barrel. Therefore, in order to reduce the size in the optical axis direction, it is necessary to maintain the interval between the displacement unit 20 and the linear actuator 33 while reducing the magnetic flux leakage. A method of reducing leakage will be described below.

[0102] The magnetic sensor 41 of the linear actuator 33 is mounted on the center of a magnetic circuit 38 with respect to two directions. The two directions are the optical axis direction (X direction) and a direction perpendicular to it (Z direction). The influence of the external interfering magnetic field is basically zero, so that the magnetic flux leakage can be reduced. Under this condition, when the magnetization of the magnet 8p of the pitch actuator 6p is as Picture 10 As shown, due to the influence of the pitch actuator 6p, this position of the magnetic sensor 41 will cause Picture 12 The magnetic flux shown is leaking. The position of the magnetic sensor described in Embodiment 1 is a position along the Z-axis direction indicated by a white circle.

[0103] Since the magnetic flux leakage is discharged in the -Z direction under the influence of the pitch actuator 6p, the magnetic flux leakage will enter the magnetic sensor 41 at the position shown by the white circle. When the magnetization of the main magnet 35 of the linear actuator 33 is as Picture 10 When shown, there will be a magnetic flux leakage as shown by the white circle. Therefore, the magnetic sensor 41 is displaced by a distance b in the Z direction to reach the position shown by the black circle. As a result, the magnetic flux leakage of the pitch actuator 6p in the Z-axis direction and the linear actuator 33 will cancel each other, so that the amount of magnetic flux leakage entering the magnetic sensor 41 is substantially zero.

[0104] The pitch actuator 6p has no influence on the magnetic sensor 41 in the X direction. In addition, since the position of the magnetic sensor 41 in the X direction is not changed, the magnetic sensor 41 is disposed at the magnetic core of the magnetic circuit 38 of the linear actuator 33 in the X direction. In this way, the linear actuator 41 has no influence on the magnetic sensor 41. Please note that due to the distance from the rocking actuator 6y, the magnetic flux leakage of the rocking actuator 6y is smaller than that of the pitch actuator 6p.

[0105] As described above, according to Embodiment 3, since the linear actuator is arranged so that the linear actuator is not affected by the external disturbance magnetic field, the linear actuator can be installed in the lens barrel with the hand shake compensation shift unit. In this way, the focus lens group is driven by the linear actuator to achieve fast response performance. In addition, the magnetic sensor can also be used to obtain high resolution and high accuracy, thereby achieving excellent focusing performance.

[0106] In addition, unlike the traditional technology, the magnetic flux leakage can be reduced only by planning the location of the magnetic sensor. It is not necessary to use components such as a shielding cover, thereby achieving low cost and preventing the lens barrel from increasing in size due to the addition of space for accommodating such components.

[0107] In addition, the tilting and swaying movable frames are arranged at different heights relative to the optical axis. The linear actuator for driving the focus lens is directly installed on the optical axis imaging plane side of the tilt actuator, and the tilt actuator is installed on the optical axis object side. Therefore, the size in the width direction can be shortened and the space in the optical axis direction can be effectively used, thereby achieving a reduction in the volume of the lens barrel.

[0108] Needless to say, even if Picture 10 The polarities of the magnets in the pitch actuator and the linear actuator in the displacement unit shown are reversed, and the same effect as in Embodiment 3 can also be obtained.