The present invention relates generally to a lens driving apparatus that drives a focus lens of a camera in an optical axis direction.
For example, lens driving apparatuses that drive a focus lens of a camera in an optical axis direction include a movable frame that holds a lens, a lens barrel that slidably houses the movable frame, and a Voice Coil Motor (VCM) that moves the movable frame in the optical axis direction relative to the lens barrel. The VCM includes a coil that is fixed to one of the movable frame and the lens barrel (stationary frame), and a magnet that is fixed to another one of the movable frame and the lens barrel.
The movable frame is moved in the optical axis direction relative to the lens barrel by an electromagnetic induction with the magnet by energizing the coil.
In the aforementioned conventional lens driving apparatuses, the movable frame is freely movable relative to the lens barrel when the coil of VCM is not energized. Accordingly, if the power is turned on to move the movable frame to a desired position in the optical axis direction, the movable frame is returned to a home position once to set a reference position for control, and is thereafter moved to the desired position from the home position.
Thus, it takes a long time to move the movable frame to the desired position when the apparatus is powered on, which is inconvenient.
The present invention has been made in view of the above, and an object of the present invention is to provide a lens driving apparatus that is capable of moving a lens to a desired position in a short time from startup, with a simple structure.
According to one aspect of the invention, a lens driving apparatus including: a lens holder configured to hold a lens; a guide member configured to guide movement of the lens holder in an optical axis direction; a stationary member configured to hold the guide member; a first driving unit including a magnet placed at one of the lens holder and the stationary member, and a coil placed at another one of the lens holder and the stationary member, and configured to move the lens holder in the optical axis direction along the guide member by a propulsion force generated by energizing the coil; a reference position detector configured to detect a reference position of the lens holder; a driving position output unit configured to output a driving position of the lens holder relative to the reference position after the reference position of the lens holder is set based on an output of the reference position detector; and a locking unit configured, if a signal indicating a power shutdown or a sleep state is output, to direct the first driving unit to move the lens holder to the reference position based on outputs of the reference position detector and the driving position output unit, to hold the lens holder to the stationary member in synchronism with an output from the reference position detector, and to lock movement of the lens holder.
According to the present invention, it is possible to provide a lens driving apparatus that is capable of moving a lens to a desired position in a short time from startup, with a simple structure.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the drawings used for the following descriptions, the scale of each structural element may be different in order to be recognized in the drawings. The present invention is not limited to the number, shapes, ratio of sizes, and relative positions of structural elements shown in the drawings.
In the following descriptions, the direction from a camera main body 200 to a subject (not shown in the drawings) is referred to as “front”, and the opposite direction is referred to as “rear” or “back”. An axis corresponding to the optical axis O of a photographing optical system formed by a lens unit 100 is referred to as a Z axis, and two axes orthogonal to one another on the plane orthogonal to the Z axis are respectively referred to as an X axis and a Y axis.
The lens driving apparatus 10 includes a movable frame 2 (lens holder) that holds the lens L, a guide member 4 that guides movement of the movable frame 2 in the optical axis O direction, a stationary frame 6 (stationary member) that holds the guide member 4, and two sets of yokes 8. The stationary frame 6 is fixed to a lens barrel 101 (
The lens driving apparatus 10 includes a coil 12 arranged in the movable frame 2, and a magnet 14 arranged in the stationary frame 6. The coil 12 and the magnet 14 are provided to each of the two sets of yokes 8. In contrast to the present embodiment, the magnet 14 may be arranged in the movable frame 2, and the coil 12 may be arranged in the stationary frame 6.
A pair of the coil 12 and the magnet 14 forms a first driving unit 16 (
The lens driving apparatus 10 also includes a reference sensor 22 (reference position detector) that detects a reference position of the movable frame 2 along the optical axis O direction, and a position sensor 24 (driving position output unit) that outputs a driving position of the movable frame 2 relative to the reference position after the reference position of the movable frame 2 is set based on an output of the reference sensor 22. In the present embodiment, the reference position of the movable frame 2 corresponds to an infinity focus position of the photographing optical system.
In the present embodiment, the reference sensor 22 is a photo-interrupter that includes a detection-object piece 22a provided in the movable frame 2 and a detector 22b provided in the stationary frame 6, and the position sensor 24 is a Giant Magneto Resistance (GMR) sensor that includes a magnetic scale 24a provided in the movable frame 2 and a detector 24b provided in the stationary frame 6.
The detection-object piece 22a of the photo-interrupter moves in the optical axis O direction along with the movable frame 2. The detector 22b has a light emitting element and a light receiving element (not shown in the drawings) positioned opposite to each other relative to a moving path of the detection-object piece 22a. A state where the light receiving element receives an optical beam emitted from the light emitting element is referred to as a sensor output, “bright”, and a state where the detection-object piece 22a blocks the optical axis is referred to as a sensor output, “dark”.
The magnetic scale 24a has a structure where a north pole and a south pole are arranged at an equal distance in the optical axis O direction, and the detector 24b detects a flux of the magnetic scale 24a. The controller 20 calculates a moving amount from the reference position of the movable frame 2 based on a changing amount of flux detected by the detector 24b.
The lens driving apparatus 10 includes a holding mechanism 30 (locking unit) that allows the first driving unit 16 to move the movable frame 2 to the reference position based on the outputs of the reference sensor 22 and the position sensor 24, and locks movement of the movable frame 2 relative to the stationary frame 6 by holding the movable frame 2 to the stationary frame 6 in synchronism with an output from the reference sensor 22, in a case where a signal indicating a power shutdown or a sleep state is output. A second driving unit 18 drives the holding mechanism 30.
The holding mechanism 30 includes an engagement recess 32 provided in the movable frame 2 and an engagement piece 34 (restriction member) provided in the stationary frame 6. The second driving unit 18 (
The operation of the aforementioned lens driving apparatus 10 will be described with reference to
In a case where a signal indicating a power shutdown or a sleep state is output, if the controller 20 detects a power-off signal (step 1), the controller 20 controls the first driving unit 16 to drive the movable frame 2 in the direction of the holding position P (step 2). If it is determined that the movable frame 2 reaches the holding position P (step 3: Yes), the controller 20 controls the first driving unit 16 to stop the movable frame 2 at the holding position P (step 4).
Then, the controller 20 controls the second driving unit 18 so that the engagement piece 34 of the holding mechanism 30 is engaged with the engagement recess 32 (step 5). By this operation, the movable frame 2 is held at the holding position P. Thereafter, the controller 20 stops the operation of the first driving unit 16 (power feeding to the coil 12) (step 6), and turns the power off (step 7).
If a power-on signal is detected (step 11), the controller 20 activates the first driving unit 16 to hold the movable frame 2 at the holding position P (step 12). In this state, the controller 20 controls the second driving unit 18 so that the engagement between the engagement piece 34 and the engagement recess 32 is released (step 13). In this state, the movable frame 2 is held at the holding position P.
Thereafter, the controller 20 controls the first driving unit 16 to move the movable frame 2 toward the reference position (step 14). If it is determined that the movable frame 2 reaches the reference position, and the reference sensor 22 is switched (step 15: Yes), the controller 20 proceeds with the normal control operation (step 16).
As stated above, according to the present embodiment, since the movable frame 2 is held at the holding position P close to the reference position when the power is turned off, the movable frame 2 can be moved to the reference position instantly when the power is turned on, and the normal control operation can be initiated immediately after the power is turned on. Accordingly, the present embodiment improves convenience.
In the present embodiment, the movable frame 2 is held at the holding position P close to the reference position when the power is turned off; however, the holding position P is not necessary to be close to the reference position. That is, according to the present embodiment, the movable frame 2 is at least held at the holding position P away from the reference position in a predetermined direction
(the left direction of
If a power-on signal is detected (step 21), the controller 20 activates the first driving unit 16 to hold the movable frame 2 at a position P (step 22). In this state, the controller 20 controls the second driving unit 18 so that the engagement between the engagement piece 34 and the engagement recess 32 is released (step 23). In this state, the movable frame 2 is held at the reference position.
Thereafter, the controller 20 checks the state of the reference sensor 22 (sensor output), and if the output of the reference sensor 22 is “dark” (step 24: Yes), the controller 20 determines that the movable frame 2 is placed at the reference position, and controls the first driving unit 16 to move the movable frame 2 away from the reference position (the left direction in
On the other hand, if it is detected that the output of the reference sensor 22 is “bright” at step 24 (step 24: No), the controller 20 determines that the movable frame 2 is not placed at the reference position, and controls the first driving unit 16 to move the movable frame 2 toward the reference position (the right direction in
In either case, if it is determined that the movable frame 2 reaches the reference position (or is moved from the reference position), and the reference sensor 22 is switched (step 27: Yes), the controller 20 proceeds with the normal control operation (step 28).
As stated above, according to the present modification, since the movable frame 2 is held at the reference position when the power is turned off, the control operation can be initiated rapidly in comparison with the aforementioned embodiment, thereby improving convenience. In addition, according to the modification, even if the movable frame 2 is not placed at the reference position when the power is turned on, the movable frame 2 can be moved instantly to the reference position, and the normal control operation can proceed instantly.
The present invention is not limited to the embodiment described above and can be modified in various manners without departing from the spirit of the invention.
Number | Date | Country | Kind |
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2015-116850 | Jun 2015 | JP | national |
This application is a Continuation Application of PCT Application No. PCT/JP2015/084548, filed Dec. 9, 2015 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2015-116850, filed Jun. 9, 2015, the entire contents of all of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/JP2015/084548 | Dec 2015 | US |
Child | 15796416 | US |