JP2023170722A - Driving device and lens barrel having the same - Google Patents

Abstract

[Problem] It is possible to hold the lens frame when the voice coil motor is not energized without using a complicated structure, and it is possible to accurately hold a heavier lens frame while reducing backlash compared to driving with a single stepping motor. To provide a driving device capable of driving at high speed and a lens barrel having the same. A driving device of the present invention includes a lens frame that holds a lens group, a voice coil motor that moves the lens frame in the optical axis direction, and a stopper mechanism that restricts movement of the lens frame. The stopper mechanism includes a stepping motor and a lead screw rotated by the stepping motor, and is characterized in that the lead screw is screwed into the lens frame. [Selection diagram] Figure 1

Description

The present invention relates to a driving device and a lens barrel having the same. In particular, it relates to a method of driving a lens unit that can move forward and backward in the optical axis direction.

Conventionally, in digital cameras and digital video cameras, stepping motors and voice coil motors have been used as drive devices for moving lens frames in the optical axis direction for zooming and focusing.

Driving the lens frame with a stepping motor allows for high-speed and accurate positioning. However, since the torque is small, there is a drawback that a heavy lens frame cannot be driven at high speed.

On the other hand, a voice coil motor has a larger torque than a stepping motor, so it can drive a heavy lens frame at high speed. However, since there is no stable stopping position in the de-energized state, there is a drawback that the lens frame driven by the voice coil motor is not held within the movable range and moves in the de-energized state. As a result, there is a possibility that abnormal noises due to the collision may occur inside the lens barrel.

Patent Document 1 discloses a lens drive device having a lead screw that is compact and capable of efficiently preventing play with a small number of parts and driving with high precision.

Further, Patent Document 2 discloses a lens barrel and a camera device that can prevent movement of an optical element inside the lens barrel even when the voice coil motor is not energized.

Japanese Patent Application Publication No. 2005-215309 JP2019-109427A

In the lens driving device described in Patent Document 1, the weight of the lens frame that can be stably driven is limited by the load of the biasing spring used to reduce play in the connecting parts.

In the lens barrel described in Patent Document 2, a drive mechanism is required to move the stopper member for holding the movable lens frame body from the retracted position to the contact position when the voice coil motor is not energized, and the number of parts is reduced. As the number increases, the structure becomes more complex.

The present invention was made in view of this situation, and it is possible to hold the lens frame body when the voice coil motor is not energized without using a complicated structure, and it is possible to hold the lens frame body when the voice coil motor is not energized. It is an object of the present invention to provide a driving device capable of driving a heavier lens frame accurately and at high speed while reducing backlash, and a lens barrel having the driving device.

In order to solve the above-mentioned problems, a drive device according to a first aspect of the present invention includes:
a lens frame that holds the lens group;
a voice coil motor that moves the lens frame in the optical axis direction;
It has a stopper mechanism that restricts the movement of the lens frame,
The stopper mechanism is
stepping motor and
It has a lead screw rotated by a stepping motor,
It is characterized by a lead screw screwed into the lens frame.

The drive device according to the second invention of the present invention is
The lens frame is
It has a fixed part,
The stopper mechanism is
It has a stopper member that is screwed together with the lead screw and moves in the optical axis direction when driven by a stepping motor.
It is characterized in that the lens frame and the lead screw are screwed together by fixing the fixed portion and the stopper member.

The drive device according to the third aspect of the present invention is
a direction control section;
has a drive control section,
The direction control section is
The voice coil motor controls the force that moves the lens frame forward and backward in the optical axis direction.
The drive control section is
It is characterized by driving or stopping the stopper mechanism.

A lens barrel according to a fourth aspect of the present invention is characterized by comprising the drive device according to the third aspect.

According to the present invention, it is possible to hold the lens frame when the voice coil motor is not energized, and it is possible to drive a heavier lens frame more accurately and at high speed compared to a drive method using a single stepping motor. .

A schematic diagram showing the configuration of a lens barrel 20 equipped with a focus unit 22 according to an embodiment of the present invention attached to a camera body 10 A side view of the focus unit 22 according to the embodiment of the present invention A cross-sectional view of Figure 2 cut at L, viewed from the front. A schematic diagram illustrating the operation of moving the lens frame 30 by the voice coil motor 40 and the stepping motor 51 in the focus unit 22.

Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to this example. Further, each drawing is simplified to simplify the explanation of the present invention.

FIG. 1 is a schematic diagram showing the configuration of a lens barrel equipped with a focus unit 22 according to an embodiment of the present invention attached to a camera body 10, FIG. 2 is a side view of the focus unit 22, and FIG. 2 is a cross-sectional view taken along the line L in FIG. 2 and viewed from the front, and FIG. 4 is a schematic diagram illustrating the operation of moving the lens frame 30 by the voice coil motor 40 and the stepping motor 51 in the focus unit 22. .

As shown in FIG. 1, a camera control section 11 included in the camera body 10 and a lens control section 21 included in the lens barrel 20 are communicating with each other. The camera control section 11 and the lens control section are constituted by a processing device such as a CPU. The lens control section 21 is configured to perform various controls within the lens barrel 20 in response to commands from the camera control section 11 and commands from various switches (not shown) disposed on the outer surface of the lens barrel. For example, when a release button (not shown) of the camera body 10 is operated, the camera control unit 11 issues a focus drive instruction to the lens control unit 21 in response to the operation, and the lens control unit 21 controls the focus control unit 60 in the focus unit 22. An instruction is issued to control the drive of the focus unit 22.

Next, the configuration of the focus unit 22 will be explained using FIGS. 2 and 3.

As shown in FIGS. 2 and 3, the focus unit 22 includes a lens frame 30, a voice coil motor 40, and a stopper mechanism 50.

The voice coil motor 40 includes a yoke a41, a yoke b42, an end yoke a43, an end yoke b44, a magnet 45, and a coil 46. The coil 46 has a winding shaft, and the yoke a41 is inserted through the winding shaft.

Further, the coil 46 is fixed to the lens frame 30 via a coil holding portion 47, and the lens frame 30 is configured to move together when the coil 46 moves.

The magnet 45 is fixed to the yoke b42, and is fixed to the surface of the yoke b42 that faces the yoke a41. The end yoke a43 and the end yoke b44 are arranged to fix the yoke a41 and the yoke b42.

Note that the focus unit 22 may be configured to include a plurality of voice coil motors 40. For example, in addition to the voice coil motor 40, a voice coil motor having the same configuration is arranged at a position symmetrical to the center of the lens frame 30. This makes it possible to obtain a large thrust, and furthermore, it becomes possible to make it difficult to generate unnecessary moments when moving the lens frame 30 in the optical axis direction.

The lens frame 30 holds the lens group 33, has a fixed portion 31 through which guide bars 341 and 342 arranged parallel to the optical axis are inserted. The lens frame 30 is movable in the optical axis direction via a guide bar 341 and a guide bar 342. Although the lens group 33 is described as one lens as an example, it may be a lens group including a plurality of lenses or a cemented lens in which a plurality of lenses are cemented. In addition, other optical elements such as a diaphragm and a filter may be included.

Note that in FIGS. 2 and 3, the fixed portion 31 is arranged so as to face the voice coil motor 40 with respect to the center of the lens frame 30, but the present invention is not limited thereto.

The stopper mechanism 50 includes a stepping motor 51, a lead screw 52, and a stopper member 53. The lead screw 52 is fixed to the rotating shaft of the stepping motor 51, and the stopper member 53 is screwed onto the lead screw 52. By driving the stepping motor 51, the lead screw 52 is rotated, and the stopper member 53 screwed onto the lead screw 52 is configured to be movable in the optical axis direction.

The fixed portion 31 and the stopper member 53 are fixed with adhesive or screws so that no gaps or looseness occur. By fixing the fixed portion 31 and the stopper member 53, the lens frame 30 can be moved in the optical axis direction by rotation of the lead screw 52.

Note that in FIGS. 2 and 3, the fixed portion 31 has a structure in which a protrusion is provided on a part of the lens frame 30, but the present invention is not limited to this. The stopper member 53 may be fixed to an arbitrary location on the lens frame 30, or a member for connecting the lens frame 30 and the stopper member 53 may be separately prepared and fixed.

Further, a configuration may be adopted in which the lead screw 52 is directly screwed into the lens frame 30 without using the fixed portion 31 and the stopper member 53. In the case of a configuration in which the lead screw 52 is directly screwed into the lens frame 30, driving the stepping motor 51 rotates the lead screw 52, and the lens frame 30 screwed onto the lead screw 52 is rotated in the optical axis direction. Constructed to be movable.

Further, the focus unit 22 includes a focus control section 60. The focus control section 60 controls the amount of current flowing through each motor included in the focus unit 22, the direction of the current, the timing of flowing the current, and the like.

The focus control section 60 includes a motor driver V61, which is a direction control section, and a motor driver S62, which is a drive control section.The motor driver V61 controls the drive of the voice coil motor 40, and the motor driver S62 controls the driving of the stepping motor 51.

Next, the operation of each motor included in the focus unit 22 will be explained.

In the voice coil motor 40, the end of the coil 46 is connected to a flexible printed circuit board 70 (not shown), and the flexible printed circuit board 70 is connected to a power supply section 80 (not shown) via a motor driver V61. By supplying current from the power supply section 80, a thrust force is generated in the optical axis direction.

The motor driver V61 receives instructions from the lens control section 21 and controls the voice coil motor 40. For example, when receiving an instruction from the lens control unit 21 to move the coil 46 forward in the optical axis direction, a thrust is generated in the direction to move the coil 46 forward in the optical axis direction, and when receiving an instruction to move the coil 46 backward, the coil 46 is A thrust is generated in the direction of retreating with respect to the optical axis direction.

When moving the coil 46 forward and backward in the optical axis direction, the direction can be switched between the forward direction and the backward direction by controlling the direction of the current supplied to the coil 46 by the motor driver V61.

Further, the stepping motor 51 is connected to a flexible printed circuit board 70 (not shown), and the flexible printed circuit board 70 is connected to a power supply section 80 (not shown) via a motor driver S62. The lead screw 52 fixed to the output shaft of the stepping motor 51 rotates when current is supplied from the power supply section 80, and the stopper member 53 moves as the lead screw 52 rotates.

The motor driver S62 receives instructions from the lens control section 21 and controls the stepping motor 51. For example, when receiving an instruction from the lens control unit 21 to move the lens frame 30 to a desired position, the stepping motor 51 is driven to rotate the lead screw 52 and move the stopper member 53 to the desired position. .

In order to move to a desired position with higher precision, the focus unit 22 may be provided with a sensor for position detection. The position detection sensor is, for example, a magnetic sensor such as a magnetoresistive element or a Hall element, or a position detection sensor such as an optical encoder using a photo sensor, etc., to detect the movement of the lens frame 30. A configuration that accurately detects the amount can be realized.

Next, how to hold the lens frame 30 during non-energization will be explained. Since the lens frame 30 is fixed to the coil 46 included in the voice coil motor 40 via the coil holding part 47, it can move within a range until the coil 46 comes into contact with the end yoke a43 and the end yoke b44. It is.

As shown in FIG. 2, the fixed portion 31 of the lens frame 30 is fixed to a stopper member 53 of the stopper mechanism 50. The stopper member 53 moves on the lead screw 52 when the stepping motor 51 is driven, but does not move and is fixed on the lead screw 52 when the power is not applied. Thereby, the lens frame 30 fixed to the voice coil motor 40 is held by the stopper member 53 when the power is not supplied.

Next, the operation of the lens frame 30 in the focus unit 22 will be explained.

When the focus control unit 60 receives a focus drive command from the lens control unit 21, the motor driver V61 and the motor driver S62 included in the focus control unit 60 control the voice coil motor 40 and the stepping motor 51, and the lens included in the focus unit 22 is controlled. The frame body 30 is moved forward and backward in the optical axis direction.

The motor driver V61 controls the voice coil motor 40 to switch between driving the lens frame 30 forward or backward along the optical axis direction. The voice coil motor 40 controlled by the motor driver V61 generates a thrust greater than the load of the lens frame 30.

While the voice coil motor 40 is generating thrust, the motor driver S62 rotates the lead screw 52 by controlling the stepping motor 51 to move the lens frame 30 to a desired position, and the stopper member 53 move it to the desired position. Since the voice coil motor 40 generates thrust in the direction of the desired position, the lens frame 30 moves to the desired position as the stopper member 53 moves.

Normally, when a stepping motor is loaded, the rotational speed of the motor decreases, resulting in a decrease in the movement speed of the nut member moving on the lead screw. By configuring the focus unit 22 as in this embodiment, the load of the lens frame 30 applied to the stepping motor 51 is borne by the thrust generated by the voice coil motor 40, so that the stopper member 53 can be moved at high speed. It becomes possible. As a result, by moving the stopper member 53 while the voice coil motor 40 generates a thrust to move the lens frame 30, the lens frame becomes heavier than when moving the lens frame 30 by driving the stepping motor 51 alone. can be moved accurately and at high speed.

Furthermore, the voice coil motor 40 continues to generate thrust in the direction before switching until it receives an instruction to switch the drive direction from the motor driver V61. When the lens frame 30 moves to the desired position, the motor driver S62 controls the stepping motor 51 and stops the rotation of the lead screw 52. When the lead screw 52 stops rotating, the lens frame 30 stops at a desired position. Although the voice coil motor 40 continues to generate thrust, the lens frame 30 does not move unless the lead screw 52 rotates. Furthermore, since the voice coil motor 40 continues to generate thrust in one direction, it is possible to remove looseness at the threaded joint between the lead screw 52 and the lens frame 30 by the biasing force in one direction. .

For example, when the focus control unit 60 receives a command to move the lens frame 30 to position X in FIG. 51, the stopper member 53 is controlled to move to position X. The lens frame 30 is moved to position X by the thrust of the voice coil motor 40 and the position control of the stepping motor 51.

In this embodiment, the driving device is configured to move the lens frame in the optical axis direction for focusing, but the invention is not limited to this. For example, the lens frame may be moved in the optical axis direction for zooming.

Further, in this embodiment, only the main parts of the present invention have been explained. The other parts can be configured using well-known techniques related to drive devices and lens barrels as appropriate.

As explained above, according to the driving device according to the present invention, it is possible to hold the lens frame that is moved by the voice coil motor even when the power is not applied, and the lens frame is heavier than the driving method using a single stepping motor. It becomes possible to drive the frame body accurately and at high speed.

10 Camera body 11 Camera control unit 20 Lens barrel 21 Lens control unit 22 Focus unit 30 Lens frame 31 Fixed part 33 Lens group 341 Guide bar 342 Guide bar 40 Voice coil motor 41 Yoke a
42 Yoke b
43 End yoke a
44 End yoke b
45 Magnet 46 Coil 47 Coil holding section 50 Stopper mechanism 51 Stepping motor 52 Lead screw 53 Stopper member 60 Focus control section 61 Motor driver V
62 Motor driver S

Claims (4)

a lens frame that holds the lens group;
a voice coil motor that moves the lens frame in the optical axis direction;
a stopper mechanism for regulating movement of the lens frame;
The stopper mechanism is
stepping motor and
a lead screw rotated by the stepping motor;
A drive device characterized in that the lead screw is screwed into the lens frame. The lens frame body is
It has a fixed part,
The stopper mechanism is
a stopper member that is threadedly engaged with the lead screw and moves in the optical axis direction by driving of the stepping motor;
The drive device according to claim 1, wherein the lens frame and the lead screw are screwed together by fixing the fixed portion and the stopper member. a direction control section;
has a drive control section,
The direction control section includes:
The voice coil motor controls a force for moving the lens frame forward and backward in the optical axis direction,
The drive control section includes:
The drive device according to claim 1 or 2, characterized in that the stopper mechanism is driven or stopped. A lens barrel comprising the drive device according to claim 3.

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