JP3792827B2 - Optical device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical device provided with an image blur correction device for optically correcting camera shake such as camera shake by driving a part of a photographing optical system.
[0002]
[Prior art]
Conventionally, in order to prevent image blur due to camera shake or the like that is likely to occur during hand-held shooting, a camera shake state is detected by a shake detection unit, and a photographing lens system or a part of the optical system is corrected according to the detection result. In the past, there has been known a shake correction apparatus having a configuration in which this is moved in a direction perpendicular to the optical axis.
[0003]
In a camera having such a blur correction function, a correction lens constituting at least a part of the photographing lens system is movably supported, and the correction lens absorbs blur in a plane perpendicular to the optical axis of the main optical system. By moving the image in the moving direction, the shift of the image formation position due to the shake is corrected to eliminate the image shake.
[0004]
In such a shake correction device, as a drive mechanism for moving the correction lens, a motor is used as a drive source, a drive force is transmitted by a gear, a lever, a screw, etc., and a lens frame that is spring-biased from one side is pressed. The electromagnetic actuator is composed of a coil and a magnet, and either one is held on the fixed side and the other is held on the correction lens side, and the lens frame is moved directly.
[0005]
At this time, if the lens frame rotates around the optical axis, the target drive amount and the actual movement amount will deviate, and accurate detection of the lens frame position will not be possible, resulting in accurate shake correction. Therefore, it is necessary to intervene a guide member that can translate the lens frame without rotating. Also, if the guide member is slid, it will not be able to drive smoothly due to its frictional resistance, especially when correcting small amplitudes. Therefore, two tension coil springs are attached at opposite positions across the optical axis on the outer periphery of the lens frame. The rotation of the lens frame is prevented by a pulling force in the radial direction.
[0006]
For example, Japanese Patent Laid-Open No. 3-186824 discloses a configuration in which the thrust generation axis of the driving means and the optical axis of the correction lens are made to coincide with each other so that the rotational moment around the optical axis of the correction lens is reduced and the driving can be performed more smoothly. Has been.
[0007]
Further, in the structure described in Japanese Patent Application Laid-Open No. 7-28114, the driving force transmitting means so as to reduce the rotational moment around the optical axis generated by the friction generated between the engaging portion of the driving force transmitting means and the lens frame. The position of the lens frame acting on the lens frame is brought close to the friction generating axis and is shifted from the center of the optical axis so that the drive control of the lens frame in a required state can be performed appropriately and reliably.
[0008]
[Problems to be solved by the invention]
However, in the above-described conventional example, in the conventional example in which two tension coil springs are attached at opposite positions sandwiching the optical axis on the outer periphery of the lens frame as described above, the load during driving is large and the target performance is obtained. Has a problem of requiring large power consumption. Moreover, since a large space is required in the radial direction, there is a problem that it is difficult to reduce the size of the apparatus.
[0009]
Furthermore, in the conventional example in which the thrust generation axis of the driving unit and the optical axis of the correction lens coincide with each other, it is assumed that the weight of the correction lens occupies most of the weight of the entire movable part. If the optical system becomes smaller, such as a digital still camera, the weight other than the correction lens such as the lens frame cannot be ignored.
[0010]
In particular, when a moving coil type or moving magnet type electromagnetic actuator is used, it is necessary to hold a coil or magnet as a part of the driving means on the movable part, and the ratio of the weight of the moving unit increases. Therefore, if the thrust generation axis of the driving means and the optical axis of the correction lens are made coincident with each other, a rotational moment around the optical axis is generated due to weight imbalance, and the driving characteristics are deteriorated. There is a problem that an error occurs in detection.
[0011]
Furthermore, in the conventional example in which the rotational moment due to friction is canceled, the driving force is transmitted to the driving force transmitting means and the lens frame is driven via the moving amount generating means, so that there is no gap between the moving amount generating means and the lens frame. Since it is a guide for driving in one direction at the same time as driving in the other direction, it is necessary to urge it with a spring from one side. For this reason, the influence of friction is large, and there is an effect as described in the conventional example. However, in the structure in which the lens frame is directly driven as in the moving coil system, such as a drive amount transmission means and a movement amount generation means. Since no member is required and the influence of friction can be reduced, there is a problem that the influence of the weight balance is increased accordingly.
[0012]
In view of the above problems, an object of the present invention is to effectively cancel or reduce the force generated when the correction lens is driven by a simple and inexpensive structure, to accurately drive the correction lens, and to effectively perform shake correction. An object of the present invention is to provide an optical device including a shake correction device that can be performed.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, an optical apparatus according to the present invention includes a lens frame that is movable in a plane substantially perpendicular to the optical axis, a part of the main optical system, and a camera shake caused by camera shake and the like. And a fixed frame having a guide portion for moving the lens frame in a plane substantially orthogonal to the optical axis, and located between the lens frame and the fixed frame. One end of a coil spring having an inner diameter larger than an effective light beam diameter passing through the correction lens is held by the lens frame, and the other end is held by the fixed frame.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail based on the illustrated embodiments.
FIG. 1 is a sectional view of a zoom lens for a video camera which is an optical apparatus embodying the present invention, and FIG. 2 is an exploded perspective view of the zoom lens barrel of FIG. In FIG. 1, on the optical axis, the first group lens L1 from the object side, the second group lens L2 for zooming, and the third group serving as a correction lens driven in a direction perpendicular to the optical axis for blur correction. A lens L3, a fourth lens group L4 that performs focus adjustment, and a low-pass filter F are arranged. A CCD sensor (not shown) is disposed behind the low-pass filter F.
[0016]
The first group lens L1 is held in the front lens barrel 1, the second group lens L2 is held in the second group lens barrel 2, and the second group lens barrel 2 has the front lens barrel 1 and the rear lens barrel in the front-rear direction. 3 is movable in the direction of the optical axis by two guide bars 4a and 4b held by the shaft 3. The third lens group L3 is held by the correction unit 5, is sandwiched between the front lens barrel 1 and the rear lens barrel 3, and is fixed by screws. The fourth group lens L4 is held by the fourth group barrel 6, and is held movably in the optical axis direction by the guide bars 4a and 4b similarly to the second group barrel 2. The low pass filter F is held by the rear barrel 3. Is retained. A diaphragm S is disposed between the second lens group L2 and the third lens group L3. The diaphragm S is driven by an electromagnetic diaphragm unit 7. The electromagnetic diaphragm unit 7 is a front mirror. It is sandwiched between the cylinder 1 and the shake correction unit 5.
[0017]
A zoom motor 11 including a stepping motor has a driving part and a screw part integrally attached to a U-shaped sheet metal, and is fixed to the front barrel 1 with screws. On the other hand, a rack 12 is attached to the second group barrel 2, and the rack 12 is driven in the optical axis direction by meshing with a threaded portion of the zoom motor 11. At this time, the rack 12 is urged by the spring 13 in the meshing direction and the optical axis direction, so that the thrust is removed when meshed.
[0018]
The focus motor 14 is the same motor as the zoom motor 11 and is fixed to the rear barrel 3 with screws. A rack 15 and a spring 16 are attached to the fourth group barrel 6 in the same manner as the second group barrel 2, and when the rack 15 meshes with the threaded portion of the focus motor 14, the third group lens L4 is moved in the optical axis direction. To be driven.
[0019]
An interrupter 21 is fixed to the front barrel 1 with screws in a state where terminals are soldered to the substrate 22, and the second group barrel 2 is integrally provided between the light projecting portion and the light receiving portion. By passing the slit portion 2a, the reference position of the second lens barrel 2 is detected and driven to each zoom position by the number of pulses input to the zoom motor 11. Similarly, in the focus adjustment, the slit portion 6a provided in the fourth group barrel 6 is detected as a reference position by the interrupter 23 and the substrate 24 attached to the rear barrel 3, and is step-driven.
[0020]
FIG. 3 is an exploded perspective view of the shake correction unit 5, and a fixed frame 30 as a main body of the correction unit 5 is sandwiched between the front lens barrel 1 and the rear lens barrel 3. The movable frame 31 holds the third group lens L3 that is a shake correction lens, and the pins 32 attached to the three outer peripheral positions engage with the long holes 30a provided in the fixed frame 30 in the circumferential direction, thereby the optical axis. It is held movably in a plane perpendicular to the surface. The coil spring 33 is held between the fixed frame 30 and the movable frame 31 so as to be slightly compressed. At this time, the coil spring 33 is first bonded and fixed to the fixed frame 30 so that the bent portion 33a is in a predetermined phase. After that, the fixed portion 30 and the movable frame 31 are phase-matched by incorporating the bent portion 33a so as to fit into the groove 31a shown in FIG.
[0021]
The holding force of the coil spring 33 suppresses rotation around the optical axis when the movable frame 31 is driven. That is, since the rotation is prevented by the torsional torque of the coil spring 33, the rotation cannot be completely stopped. However, compared to the case of using a member that is guided by sliding, a load due to friction is not generated, and a small amount is driven. There is no problem that causes a catch at the beginning of movement.
[0022]
Further, the torsional torque of the coil spring 33 is set so as to return against the friction between the pin 32 and the elongated hole 30a up to a rotation angle satisfying the target performance even when a rotational moment is applied to the movable frame 31. Therefore, the blur correction effect is not deteriorated. Coils 34a and 34b are fixed to the movable frame 31 for driving in the horizontal direction, that is, the X direction and in the vertical direction, that is, the Y direction, respectively.
[0023]
Magnets 36a, 36b attracted to the lower yokes 35a, 35b are inserted into the holes 30c, 30d of the fixed frame 30 from the back side and fixed. The upper yoke 37 is fixed with screws 39 together with the sensor holder 38 from the front, so that a magnetic circuit for driving in the X and Y directions is configured. That is, the magnet 36a, the lower yoke 35a, and the upper yoke 37 constitute a magnetic circuit for driving in the X direction, and the coil 34a is inserted therein, and the magnet 36b, the lower yoke 35b, and the upper yoke are driven for driving in the Y direction. A magnetic circuit is constituted by 37, and a coil 34b is inserted therein, whereby a moving coil type electromagnetic actuator is constituted.
[0024]
Infrared light emitting diodes 40a and 40b and position detection light receiving elements 41a and 41b are inserted and fixed to the sensor holder 38 from the X and Y directions, respectively. And between each infrared light emitting diode 40a, 40b and the position detection light-receiving element 41a, 41b, the elongate hole-shaped slit 31b, 31c integrally provided in the movable frame 31 is provided, and the infrared light emitting diode 41a is provided. 41b, only the infrared light that has passed through the slits 31b and 31c is received by the position detection light-receiving elements 41a and 41b, and the positions of the movable frame 31 in the X and Y directions are detected. It has become. Electrical components of these infrared light emitting diodes 40a and 40b, position detection light receiving elements 41a and 41b, and coils 34a and 34b are connected to a flexible printed board 42 shown separately, and are connected to a control circuit provided on the camera body side (not shown). It is connected.
[0025]
FIG. 4 is a front view of only the drive unit of the shake correction unit 5. If the central axes of the coil 34a, the magnet 36a, and the yoke 35a, which are actuators in the X direction, are AA lines, and the central axes of the coil 34b, the magnet 36b, and the lower yoke 35b, which are actuators in the Y direction, are BB lines, The central axis of thrust in the Y direction coincides with the AA line and the BB line, respectively, and shifts from the optical axis center of the third lens unit L3, which is a shake correction lens, toward the driving actuators in the other directions. ing. Point G is the total center of gravity including the third lens unit L3, which is a movable part, the movable frame 31, the coils 34a and 34b, and the pin 32, and the thrust center axes AA and BB intersect the center of gravity G. It is set to be. By doing so, it is possible to reduce the rotational moment generated by weight imbalance.
[0026]
In the moving magnet system as in the present embodiment, the lens frame can be directly driven, so that a driving force transmission member is not required and the portion where friction is generated can be reduced. Further, since the pins 32 and the long holes 30a are equally provided at three locations in the circumferential direction, the rotational moment generated by the frictional force and viscous resistance at the portions is small. For this reason, the influence of weight imbalance increases as a factor causing the third group lens L3 to generate a rotational moment, and the thrust generating central axis of the driving means passes through the center of gravity of the entire movable portion as in this embodiment, so that the lens Since the rotational moment generated in the frame can be suppressed satisfactorily and the target position can be reliably driven with high accuracy, an image blur correction device having a high blur correction effect can be realized.
[0027]
【The invention's effect】
As described above, according to the optical device according to the present invention, the rotation of the lens frame around the optical axis is suppressed by the torsional torque of the coil spring, so that it can move in a direction substantially perpendicular to the optical axis. Regardless of the structure, it is possible to prevent deterioration of drive characteristics and position detection accuracy. In addition, since it is possible to prevent the deterioration of characteristics during minute driving due to sliding, it is possible to effectively correct even slight camera shake.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a zoom lens for a video camera according to an embodiment.
FIG. 2 is an exploded perspective view of a zoom lens barrel.
FIG. 3 is an exploded perspective view of a shake correction unit.
FIG. 4 is a front view of a drive unit of a shake correction unit.
[Explanation of symbols]
L3 3rd lens group 5 Shake correction unit 30 Fixed frame 31 Movable frame 32 Pin 33 Coil springs 34a, 34b Coils 35a, 35b Lower yoke 36a, 36b Magnet 37 Upper yoke 40a, 40b Infrared light emitting diode 41a, 41b Position detection light receiving element

Claims (1)

A lens frame movable in a plane substantially orthogonal to the optical axis, a part of the main optical system, a correction lens that is held by the lens frame to suppress camera shake caused by camera shake, and the lens frame is connected to the optical axis. A fixed frame having a guide portion for moving in a plane substantially orthogonal to the lens frame, and having an inner diameter larger than an effective luminous flux diameter that is located between the lens frame and the fixed frame and passes through the correction lens An optical apparatus , wherein one end of a coil spring is held by the lens frame and the other end is held by the fixed frame.

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