JP2004334099A - Lens barrel and imaging apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a lens barrel on which a stepping motor with a sensor is mounted and to miniaturize an imaging apparatus. <P>SOLUTION: The stepping motor 3 with a sensor is constituted of an actuator part 4 and a sensor part 6, and the sensor part 6 is separated and arranged on the front side of the lens barrel 1. As a result, since a distance between the sensor part 6 and the other actuator gets long, the influence of disturbance magnetic field on the sensor part 6 is reduced and a degradation in the performance of the motor 3 is restrained, so that zoom speed is made higher and zoom sound is made lower without making the lens barrel 1 large. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lens barrel used for an imaging device such as a video camera.
[0002]
[Prior art]
In general, a lens barrel for a video camera is composed of four lens groups, of which a movable lens group for zooming and focusing is moved in the optical axis direction by being guided by a guide pole. Among these methods, as a method of driving the zoom lens group at high speed, a sensor is attached to the stepping motor, closed loop control is performed, and the rotation angle and torque are controlled, so that high-speed response, low power consumption, and low power consumption are achieved. A system for achieving noise reduction has been proposed.
[0003]
FIGS. 9A and 9B are exploded perspective views of a conventional lens barrel. (For example, see Patent Document 1). The sensor-equipped stepping motor 50 includes an actuator 51, a lead screw portion 52 provided integrally with a rotation shaft of the actuator 51, and an N-pole and an S-pole attached alternately to the rotation shaft of the actuator 51. It is composed of a magnetized sensor magnet 53 and a magnetic sensor 54 for angle detection, which is fixedly arranged facing the sensor magnet 53. In FIG. 9, the sensor magnet 53 and the magnetic sensor 54 are covered by a cover 55 for fixing the magnetic sensor 54. A screw member 57 engaged with a zoom lens moving frame 56 holding the zoom lens group L2 is screwed into the lead screw portion 52. Therefore, by the rotation of the lead screw portion 52, the zoom lens unit L2 is linearly moved in the X-axis direction.
[0004]
[Patent Document 1]
JP 2000-227614 A
[Problems to be solved by the invention]
However, the conventional lens barrel has the following problems.
[0006]
(1) When the magnetic sensor 54 of the stepping motor 50 with a sensor is affected by a disturbance magnetic field, output distortion of the magnetic sensor 54 is generated, and the performance of the actuator is deteriorated. In order to take measures against this, as shown in Patent Document 1, the magnetic sensor 54 is disposed at a position that is hardly affected by a disturbance magnetic field from the magnet 59 of another actuator 58 or at a position where the disturbance magnetic field can be canceled. However, in recent years when lens barrels have become increasingly smaller, it has become difficult to achieve this constraint.
[0007]
(2) Since the actuator 51, the sensor magnet 53, and the magnetic sensor 52 are arranged side by side, the stepping motor with sensor 50 has a disadvantage that the length in the X-axis direction is longer than that of a normal stepping motor. I have. In addition, in order to achieve the miniaturization of the video camera body, we want to cut out a part of the lens barrel and arrange a mechanism, circuit, battery, etc. that performs recording and playback on magnetic tape close to the cut-out part. There is a growing demand. Therefore, the current configuration in which the sensor unit and the actuator unit are arranged adjacent to each other is disadvantageous particularly in reducing the size of the lens barrel in the X-axis direction.
[0008]
Therefore, the present invention is to solve the above-mentioned conventional problem, and is to realize further miniaturization of a lens barrel equipped with a stepping motor with a sensor.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a first lens barrel of the present invention has a cylindrical shape or a cylindrical shape, and is multipolarly magnetized in a circumferential direction, and is rotatably mounted coaxially with the actuator portion. A sensor magnet, a stepping motor with a sensor constituted by a sensor unit composed of a magnetic sensor disposed opposite to the periphery of the sensor magnet, a lens holding frame for holding a lens group, and a lens holding frame in an optical axis direction. , And the actuator and the sensor are separated from each other on both sides of the connection with the lens holding frame at the center.
[0010]
According to the first lens barrel, since the influence of a disturbance magnetic field from another actuator on the magnetic sensor can be reduced, the sensor lens-equipped stepping motor can be mounted without increasing the lens barrel size, thereby achieving high performance. Zoom driving can be realized.
[0011]
Next, the image pickup apparatus using the second lens barrel of the present invention includes a cutout part with a part cutout at a position on the optical axis image plane side where the sensor-equipped stepping motor is provided. A part of the image pickup device is arranged so as to overlap with the cutout portion.
[0012]
According to the imaging apparatus using the second lens barrel, a part of the lens barrel is cut out, and a part of the imaging apparatus is arranged so as to overlap with the cutout part, thereby reducing the size of the imaging apparatus. be able to.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
Hereinafter, the lens barrel according to Embodiment 1 of the present invention will be described with reference to FIGS. 1A and 1B are exploded perspective views of a lens barrel equipped with a stepping motor with a sensor according to Embodiment 1, FIG. 2 is a cross-sectional view of the stepping motor with a sensor, and FIG. 3 is a position using an MR element. FIG. 4 is a diagram showing a magnetoresistive change rate characteristic of an MR element, FIG. 5 is an exploded perspective view of an image blur correction device, and FIG. 6 is a positional relationship between a moving frame for a zoom lens and a stepping motor with a sensor. FIG.
[0014]
First, a stepping motor 3 with a sensor, which is a component of the lens barrel 1 and moves the zoom lens group L2 that changes the zoom magnification in the optical axis direction (X-axis direction), will be described. The stepping motor 3 with a sensor includes an actuator unit 4, a lead screw unit 5, and a sensor unit 6. The lead screw section 5 is provided integrally with the rotation shaft 7 of the actuator section. The sensor section 6 includes a sensor magnet 8 and a magnetic sensor 9. The sensor magnet 8 has a cylindrical shape or a cylindrical shape, is coaxially attached to the rotating shaft 7, and has N and S poles alternately magnetized in the circumferential direction. Further, a magnetic sensor 9 for detecting an angle is fixedly arranged at a portion facing the sensor magnet 8. The angle 10 is provided with bearing portions 11a and 11b that connect the actuator portion 4 and the sensor portion 6 and rotatably support the rotating shaft 7. Further, both ends of the rotating shaft 7 are supported by thrust receiving members 12a and 12b. Therefore, when the actuator unit 4 rotates, the rotation amount and the rotation direction can be detected by the magnetic sensor 9.
[0015]
The zoom lens group L2 is held by a zoom lens moving frame 15. A screw member 16 is engaged with the sleeve portion 15a of the lens moving frame 15, and the screw member 16 is screwed to the lead screw portion 5 of the stepping motor 3 with the sensor. Therefore, by the rotation of the lead screw portion 5, the zoom lens group L2 is linearly moved in the X-axis direction along the guide poles 17a and 17b by the zoom lens moving frame 15. The CPU (not shown) of the sensor-equipped stepping motor system calculates the rotation axis angle information and the electric phase angle information based on the angle and the electric phase counter value output from the magnetic sensor 9. Then, the CPU calculates a drive command value based on the angle information and the electric phase angle information, and controls the sensor-equipped stepping motor 3 by supplying a drive current with a driver.
[0016]
Next, a detection method by the magnetic sensor 9 will be described with reference to FIG. The magnetic sensor 9 is a two-phase type magnetoresistive sensor composed of MR elements 9a and 9b made of a ferromagnetic thin film. The MR elements 9a and 9b are an N pole and an S pole of the sensor magnet 8. Are provided in the driving direction at an interval of 1/4 of the magnetization pitch up to the sensor magnet 8 and the direction of the current flowing through the MR elements 9a and 9b is perpendicular to the magnetization direction of the sensor magnet 8. The sensors 9 are respectively arranged. In this figure, for the sake of simplicity, the sensor magnet 8 has a columnar shape and is developed into a flat plate.
[0017]
Next, a position detection method using the magnetic sensor 9 will be described with reference to FIG. Regarding the direction of the magnetoresistance change, the resistance value hardly changes with respect to a magnetic field perpendicular to the current direction of the MR elements 9a and 9b and in a direction (y1 direction) perpendicular to the detection surface. The resistance value greatly changes with respect to a magnetic field perpendicular to the current direction of 9b and in a direction (x1 direction) parallel to the detection surface, and further, in a direction parallel to the current direction of MR elements 9a and 9b (z1 direction). ) Has the characteristic that the resistance value slightly changes. From this characteristic, when the position of the sensor magnet 8 having the magnetization pattern shown in FIG. 3 changes (rotates) with respect to the magnetic sensor 9, the MR element corresponds to the sinusoidal magnetic field intensity change pattern generated in the x1 direction. The resistance values of 9a and 9b change. Here, a sinusoidal magnetic field intensity change pattern having a phase different from that of the x1 direction by 180 ° also occurs in the y1 direction, but the resistance values of the MR elements 9a and 9b hardly change due to the above characteristics. Therefore, when the voltages applied to the MR elements 9a and 9b are output signals, the output signals have two sinusoidal waveforms having a phase difference of 90 °, and the two signal waveforms are modulated by a signal processing circuit (not shown). By performing the insertion process, the rotation amount and the rotation direction of the sensor-equipped stepping motor 3 are detected, and the position of the zoom lens unit L2 can be controlled with high accuracy by a control circuit (not shown) based on the data.
[0018]
Next, a linear actuator 20 which is another component of the lens barrel 1 and drives a focus lens group L4 for performing focus adjustment will be described. The focus lens moving frame 21 holds the focus lens group L4, is disposed in parallel with the optical axis, and has both ends fixed along a guide pole 17a, 17c fixed to a lens barrel (not shown) in the optical axis direction (X). Direction). The stator 22 of the linear actuator 20 for driving the focus lens moving frame 21 in the optical axis direction includes a main magnet 23 magnetized perpendicular to the driving direction (X direction), a U-shaped main yoke 24, And is provided in the lens barrel 1. On the other hand, the coil 27 which is a component of the mover 26 of the linear actuator 20 is fixed to the focus lens moving frame 21 so as to have a predetermined gap with the main magnet 23, and is orthogonal to the magnetic flux generated by the main magnet 23. By passing a current through the coil 27, the focus lens moving frame 21 is driven in the optical axis direction.
[0019]
On the other hand, a magnetic scale 28 having N poles and S poles alternately magnetized is attached to the movable focus lens moving frame 21 so as to face the detection surface of the magnetic sensor 29 at a predetermined distance. I have. This magnetic sensor 29 is the same as the MR element used in the stepping motor 3 with a sensor. Next, an image blur correction device that corrects image blur during shooting will be described with reference to FIG. A lens group L3 for correcting image blur during photographing is fixed to a pitching movement frame 30 movable in the Z direction. The pitching moving frame 30 is configured to be slidable via two pitching shafts 31a and 31b by providing a bearing 30a and a detent 30b on the opposite side. An electromagnetic actuator 32p is arranged below the pitching movement frame 30. The electromagnetic actuator 32p includes a coil 33p attached to the pitching movement frame 30, a magnet 34p attached to a fixed frame 36 described later, and a yoke 35p. The magnet 34p has two poles magnetized on one side, and is fixed to a U-shaped yoke 35p open on one side.
[0020]
On the optical axis image side of the pitching movement frame 30, a yawing movement frame 37 for moving the lens group L3 for correcting image blur in the Y direction is attached. On the optical axis object side of the yawing movement frame 37, fixing portions 38c and 38d for fixing both ends of two pitching shafts 31a and 31b for sliding the pitching movement frame 30 described above in the Z direction are provided. I have. Similarly, the yaw movement frame 37 is configured to be slidable via two yaw shafts 39a and 39b by providing a bearing 38a and a detent 36b on the opposite side. The two yawing shafts 39a and 39b are fixed to fixing portions 36c and 36d of a fixing frame 36 provided on the optical axis image plane side of the yawing moving frame 37. An electromagnetic actuator 32y is arranged on the left side of the yawing movement frame 37. The electromagnetic actuator 32y includes a coil 33y attached to a yawing moving frame 37, a magnet 34y attached to a fixed frame 36, and a yoke 35y. The magnet 34y is magnetized in two poles on one side, and is fixed to a U-shaped yoke 35y open on one side.
[0021]
Therefore, when a current flows through the coil 33p of the pitching movement frame 30, an electromagnetic force is generated in the Z-axis direction by the magnet 34p and the yoke 35p. Similarly, when a current flows through the coil 33y of the yawing movement frame 37, an electromagnetic force is generated in the Y-axis direction by the magnet 34y and the yoke 35y. As described above, the lens group L3 for correcting image blur is driven in two directions substantially perpendicular to the optical axis by the two electromagnetic actuators 32p and 32y.
[0022]
Next, the position detection unit of the image blur correction device will be described. The detection unit 40p of the pitching movement frame 30 moving in the Z direction is configured by a light emitting element 41p (for example, an LED), a slit 42p, and a light receiving element 44p (PSD) attached to the PSD board 43. Similarly, the detection unit 40y of the yawing movement frame 37 in the Y direction includes a light emitting element 41y, a slit 42y, and a light receiving element 44y attached to the PSD board 43. The light emitting elements 41p and 41y project light through the slits 42p and 42y, and the light passing through the slits 42p and 42y enters the light receiving elements 44p and 44y. Therefore, the movement of the image blur correction lens group L3 is the movement of light incident on the light receiving elements 44p and 44y. The light receiving elements 44p and 44y output the position information of the light incident on the light receiving surface as two current values, the output values are calculated, and the positions are detected. As described above, the image blur correction unit 45 is configured by these components.
[0023]
Next, in the stepping motor 3 with the sensor, an advantage of separating the actuator section 4 and the sensor section 6 which are the main points of the present invention will be described.
[0024]
In order to drive the sensor-equipped stepping motor 3 with high accuracy, it is important that the magnetic sensor 9 is not affected by a disturbance magnetic field. That is, in order to have a configuration in which the magnet is not adversely affected by the magnet of another actuator, in this embodiment, the main magnet 23 of the linear actuator 20 or the magnets 34p and 34y of the image blur correction unit 45, the magnetic sensor 9 is required. It is effective to dispose the lens at the farthest position in the lens barrel 1, that is, in the vicinity of the L1 lens group on the front side (left side in the figure) of the lens barrel 1, as shown in FIG. is there.
[0025]
Next, the relationship between the stepping motor 3 with sensor, the zoom lens moving frame 15 and the screw member 16 will be described. The screw member 16 connected to the zoom lens moving frame 15 is screwed with the lead screw portion 4 of the sensor-equipped stepping motor 3 as described above, and the rotation of the sensor-equipped stepping motor 3 causes the zoom lens moving frame 15 to rotate. Is movable within the range of FIG. This b is a value determined in advance by optical specifications in order to achieve a predetermined zoom magnification.
[0026]
Conversely, when the actuator unit 4 is also moved to the front of the lens barrel 1 together with the sensor unit 6 as shown in FIG. Although the same, the movement range b of the screw member 16 of the zoom lens moving frame 15 needs to be shifted to the right due to the screwing relationship between the lead screw portion 4 and the screw member 16. Therefore, the length a 'of the sleeve portion 15a of the zoom lens moving frame 15 is increased, and as a result, the length of the lens barrel 1 is also increased, which is contradictory to miniaturization of the lens barrel 1.
[0027]
From the above viewpoint, the actuator unit 4 and the sensor unit 6 of the sensor-equipped stepping motor 3 are separated from each other, and only the sensor unit 6 is disposed in front of the lens barrel 1, so that the lens barrel 1 can be downsized. it can.
[0028]
The operation of the lens barrel 1 thus configured will be described below.
[0029]
When actually taking a picture, the zoom lens unit L2 is driven by the sensor-equipped stepping motor 3 according to the zoom magnification. For focusing, the linear lens 20 drives the focus lens unit L4. Further, by detecting a camera shake with a detection sensor incorporated in the imaging apparatus and driving the correction lens group L3 so as to cancel the camera shake, it is possible to correct the image shake caused by the camera shake.
[0030]
As described above, according to the present invention, the actuator section and the sensor section of the stepping motor with a sensor are separated from each other. The effect of the disturbance magnetic field from the actuator can be reduced. Therefore, it is possible to realize high-performance zoom driving by mounting a stepping motor with a sensor, that is, high-speed response, low power consumption, and low noise without increasing the size of the lens barrel. Further, it is possible to achieve an excellent focus function by the linear actuator and a function of photographing a good image in which the camera shake is suppressed by the image blur correction unit.
[0031]
In the embodiment of the present invention, a magnetoresistance effect type magnetic sensor using an MR element is used, but any type of magnetic sensor may be used as long as it outputs an output signal corresponding to the strength of the magnetic force. Applicable to
[0032]
(Embodiment 2)
Next, a lens barrel according to Embodiment 2 of the present invention and an imaging apparatus using the same will be described with reference to FIGS. FIG. 7 is a perspective view in which a part of an imaging device is arranged in a cutout portion of a lens barrel according to Embodiment 2, and FIG. 8 is a schematic diagram illustrating a positional relationship between the lens barrel and the imaging device. Note that the components described so far are denoted by the same reference numerals, and description thereof is omitted.
[0033]
The lens barrel 1 shown in FIG. 7 has a notch 1a on the rear side (−X direction) of the actuator 4 of the stepping motor 3 with sensor. The notch 1a is an empty space by disposing the sensor unit 6 of the stepping motor with sensor 3 on the front side of the lens barrel 1. In the figure, a part of the components of the imaging device 46, for example, the mechanism 47 is arranged so as to overlap the notch 1a. As a result, as shown in FIG. 8, by arranging the mechanism in the notch portion 1a of the lens barrel 1, the width of the imaging device 45 in the direction A shown in FIG. 8A or the imaging shown in FIG. The length of the device 45 in the B direction can be reduced.
[0034]
As described above, according to the second embodiment, the actuator section and the sensor section of the stepping motor with a sensor are separated, and a part of the lens barrel in which the sensor section is originally arranged is cut out. By arranging a part of the imaging device so as to overlap with the cutout portion, the size of the imaging device can be reduced as compared with an imaging device using a lens barrel in which the part is not cutout.
[0035]
In the embodiment of the present invention, the mechanism of the imaging device is arranged in the cutout portion of the lens barrel. However, the present invention is not limited to this. Needless to say, this is obtained.
[0036]
【The invention's effect】
As described above, according to the lens barrel of the present invention, the influence of the disturbance magnetic field received by the magnetic sensor can be reduced by separating the actuator unit and the sensor unit of the stepping motor with a sensor. A remarkable effect is obtained in that the accuracy of the stepping motor with sensor can be improved without increasing the size of the cylinder. Further, according to the invention, in the lens barrel, a portion behind the stepping motor with the sensor is cut out, and a part of the image pickup device is arranged so as to overlap the cutout portion, so that the size of the image pickup device is reduced. The remarkable effect that can be obtained is obtained.
[Brief description of the drawings]
FIGS. 1A and 1B are exploded perspective views of a lens barrel equipped with a stepping motor with a sensor according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view of the stepping motor with a sensor according to the first embodiment; FIG. 3 is a schematic perspective view of a position detecting means using an MR element according to the embodiment; FIG. 4 is a diagram showing a magnetoresistance change rate characteristic of the MR element according to the embodiment; FIG. 6 is an exploded perspective view of the image blur correction device. FIG. 6 is a diagram showing a positional relationship between a moving frame for a zoom lens and a stepping motor with a sensor according to the embodiment. FIG. 7 is a sectional view of a lens barrel according to a second embodiment of the present invention. FIG. 8 is a perspective view in which a part of an imaging device is arranged in a notched portion. FIG. 8 is a schematic diagram illustrating a positional relationship between a lens barrel and an imaging device in the same embodiment. Lens barrel Exploded perspective view EXPLANATION OF REFERENCE NUMERALS
REFERENCE SIGNS LIST 1 lens barrel 1 a cutout 3 stepping motor with sensor 4 actuator 5 lead screw 6 sensor 7 rotation axis 8 sensor magnet 9 magnetic sensor 15 zoom lens moving frame 16 screw member 20 linear actuator 45 image blur correction unit 46 imaging Device 47 Mechanism L2 Zoom lens group

Claims (2)

An actuator portion, a cylindrical or cylindrical shape, a multi-pole magnetized in a circumferential direction, a sensor magnet rotatably mounted on the actuator portion coaxially, and a sensor magnet disposed to face a peripheral edge of the sensor magnet; A stepping motor with a sensor constituted by a sensor unit comprising a magnetic sensor, a lens holding frame for holding a lens group, and a connecting portion for driving the lens holding frame in the optical axis direction and connecting to the lens holding frame. A lens barrel in which the actuator section and the sensor section are separated from each other on a central portion thereof and on both sides thereof. At a position on the optical axis image plane side of the position where the stepping motor with the sensor is provided, a cutout part having a cutout part is provided, and a part of the imaging device is overlapped and arranged in the cutout part. An imaging apparatus using the lens barrel according to claim 1.

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