JP2006113874A - Positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning device that can position a movable member while suppressing its inclination in a simple and low cost structure. <P>SOLUTION: The positioning device 10 comprises: a piezoelectric actuator 20 comprising a piezoelectric element 14, a drive member 16 fixed to one end of the piezoelectric element 14, and the movable member 18 movably frictionally held on the drive member 16; a drive circuit 21 for driving the piezoelectric element 14; a position sensor 25 for detecting the position of the movable member 18; a detection circuit 26 for processing a signal from the position sensor 25; and a control circuit 28 for applying a drive command signal to the drive circuit 21 according to a position detection value by the detection circuit 26 to provide position feedback control of the movable member 18. In the positioning of the movable member 18, after the movable member 18 once reaches a target stop position, the control circuit 28 continues further positioning involving an overshoot for a predetermined time or longer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a positioning device, for example, a positioning device suitably used for driving a lens or a precision stage in a camera or an optical pickup.

  Conventionally, for example, Patent Document 1 discloses a position detection device for a moving member in a driving device using a piezoelectric element. In this drive device, a drive shaft is connected to one end of the piezoelectric element, and a movable member is frictionally engaged with the drive shaft. By applying a voltage to the piezoelectric element, expansion and contraction vibrations having different extension speeds and contraction speeds are caused. By transmitting this vibration to the drive shaft, the moving member is moved on the drive shaft. And the detection member in which the uneven | corrugated | grooved part was formed in the fixed space | interval is arrange | positioned in parallel with the drive shaft and the micro gap | interval, and the space | gap (namely, electrostatic capacitance) between a movable member and a detection member with the movement of a movable member. The position of the movable member is detected by detecting a change in the current flowing from the movable member to the detection member using the periodic change of the current.

  FIG. 9 shows a friction drive type piezoelectric actuator S with a position sensor. In this piezoelectric actuator S, the drive shaft 3 is fixed to the other end of the piezoelectric element 2 whose one end is fixed to the fixed portion 1, and the movable member 4 is movably held on the drive shaft 3. The movable member 4 includes a friction holding portion 5 that engages with the friction force on the drive shaft 3 and a lens holder 6 that is connected to the friction holding portion 5 and holds a lens (not shown). Further, the friction holding point X is located at the center of the friction holding portion 5.

  A guide shaft 7 disposed in parallel with the drive shaft 3 is engaged in the vicinity of the end of the lens holder 6, and the drive shaft is controlled by the guide shaft 7 while the rotation about the drive shaft 3 is restricted. The movable member 4 that moves along 3 is guided. A magnet 8 is attached to the end of the lens holder 6, and a magnetic sensor 9 is fixedly disposed so as to face the magnet 8.

  The driving principle of the movable member 4 in the piezoelectric actuator S having such a configuration is exactly the same as that of the driving device of Patent Document 1 described above, and is different only in that the position detection method of the movable member 4 is based on a magnetic system. It is.

  In the piezoelectric actuator S, when the driving of the movable member 4 is stopped immediately after the movable member 4 is positioned and the movable member 4 reaches the target stop position, the movable member 4 is tilted in the direction of arrow C by the moment of inertia. The phenomenon occurs. This phenomenon becomes a problem when an optical element such as a lens is driven by the movable member 4. For example, when the piezoelectric actuator S is used for aberration correction drive in an optical disc apparatus, a tracking error occurs when the lens is tilted after the lens positioning is completed. This problem also applies to the case where the aberration correction lens is driven using the drive device disclosed in Patent Document 1 that detects the position of the movable member by the electrostatic capacity method in the optical disc apparatus.

  FIG. 10 shows the relationship between the position of the movable member 4 and the lens tilt. When the drive is stopped immediately when the movable member 4 reaches the target position, the lens tilt gradually attenuates, but the lens tilt becomes considerably large immediately after the stop. ing.

JP 2003-185406 A

  Therefore, an object of the present invention is to provide a positioning device that can perform positioning control while suppressing the inclination of the movable member with a simple and inexpensive configuration.

In order to solve the above problems, a positioning device according to a first aspect of the present invention includes an electromechanical transducer, a driving member fixed to one end of the electromechanical transducer, and frictionally held on the driving member. A piezoelectric actuator made of a movable member,
A drive circuit for driving the electromechanical transducer;
A position sensor for detecting the position of the movable member;
A detection circuit for processing a signal from the position sensor;
A control circuit that performs position feedback control of the movable member by giving a drive command signal to the drive circuit based on a position detection value by the detection circuit,
In the positioning operation of the movable member, the control circuit further continues positioning control with overshoot for a predetermined time or more after the movable member once reaches a target stop position.

  According to this configuration, after the movable member once reaches the target stop position, the positioning control such as overshooting and then returning is further continued for a predetermined time or more, and then the movable member is driven and stopped, so that the target stop position is reached. Compared with the case where the movable member is immediately stopped when it reaches, the inclination at the time of positioning the movable member can be suppressed to a slight extent. In addition, positioning control such as overshooting the movable member and then returning it can be handled by a control circuit that is normally used, so that the configuration can be simplified and inexpensive.

  In the positioning device according to the first aspect of the present invention, the predetermined time is determined by a moment of inertia centered on a friction holding point of the movable member and a friction holding torque of the movable member with respect to the driving member. It may be half the period.

  According to this configuration, the inclination of the movable member generated when the drive of the movable member stops is damped, and therefore the inclination of the movable member is reduced by continuing the positioning control with the overshoot for more than half the natural vibration period. It is small enough that there is no problem.

  In the positioning device of the first aspect of the present invention, the predetermined time may be n / 2 of the natural vibration period (n is a natural number starting from 1).

  According to this configuration, the movable member can be positioned without the inclination of the movable member by stopping the positioning control with the overshoot at the time of n / 2 of the natural vibration period.

A positioning device according to a second aspect of the present invention includes an electromechanical conversion element, a drive member fixed to one end of the electromechanical conversion element, and a piezoelectric actuator comprising a movable member movably held on the drive member. When,
A drive circuit for driving the electromechanical transducer;
A position sensor for detecting the position of the movable member;
A detection circuit for processing a signal from the position sensor;
A control circuit for performing positioning control of the movable member by giving a drive command signal to the drive circuit based on a position detection value by the detection circuit,
The position sensor includes a magnetic field generating member provided on the movable member and a magnetic detection member provided on the fixed portion, and a direction in which the center of gravity of the movable member is located with reference to a friction holding point of the movable member. In the opposite direction, the magnetic field generating member is provided on the movable member.

  According to this configuration, since the magnetic moment generating member is provided on the driving member side of the movable member, the moment of inertia of the movable member is reduced, so that the inclination of the movable member when the positioning of the movable member is stopped can be reduced. .

  In the positioning device of the present invention, the movable member may hold an optical element.

  According to this configuration, the inclination of the optical element when the positioning of the movable member is stopped can be reduced.

  In the positioning device of the present invention, it is preferable that the optical axis of the optical element is parallel to the moving direction of the movable member.

  According to this configuration, the movable member can be moved in a state where the light beam to be corrected for aberration always coincides with the optical axis of the optical element.

  In the positioning device of the present invention, the optical element may form part of a photographing optical system.

  In the positioning device of the present invention, the optical element may form part of an optical pickup optical system. In this case, the optical element may be a lens of an optical pickup optical system, and aberration correction may be performed by moving the lens in the optical axis direction.

  According to this configuration, since the movable member can be positioned while suppressing the tilt of the lens, aberration correction can be performed with high accuracy.

  Furthermore, the duration of the positioning control with overshoot performed after the movable member once reaches the target stop position may be equal to or longer than the optical disk rotation period.

  According to this configuration, it becomes possible to correct in real time the aberration based on the change in the thickness of the protective layer of the optical disc that occurs within one circumference of the optical disc, and the reliability of the optical disc apparatus can be improved.

  As described above, according to the positioning device of the present invention, after the movable member once reaches the target stop position, the positioning control such as overshooting and returning is further continued for a predetermined time or more, and then the movable member is stopped driving. As a result, the tilt at the time of positioning of the movable member can be suppressed slightly compared to the case where the driving of the movable member is stopped immediately when the target stop position is reached. In addition, positioning control such as overshooting the movable member and then returning it can be handled by a control circuit that is normally used, so that the configuration can be simplified and inexpensive.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a system configuration diagram of a positioning device 10 according to a first embodiment of the present invention. This positioning device 10 includes a piezoelectric element 14 as an electromechanical conversion element whose one end is fixed to the fixing portion 12 by a method such as adhesion, and a round bar-like shape fixed to the other end of the piezoelectric element 14 by a method such as adhesion. A piezoelectric actuator 20 including a driving member 16 and a movable member 18 frictionally held on the driving member 16 is provided.

  The movable member 18 is movable along the drive member 16 in the direction of arrow D, which is the expansion / contraction direction of the piezoelectric element 14. Similarly to the movable member 4 shown in FIG. 9, the movable member 18 includes a friction holding portion that engages with the friction force on the driving member 16 and a lens (optical element) (not shown) connected to the friction holding portion. The lens holder is held, and the optical axis of the lens is parallel to the moving direction of the movable member 18. Further, when the movable member 18 moves along the driving member 16, it is guided by the guide shaft while the rotation about the driving member 16 is restricted by the guide shaft, as shown in FIG. It is the same. Further, the point that the friction holding point X is located at the center of the friction holding part of the movable member 18 is the same as that of the piezoelectric actuator S.

  For example, when the piezoelectric actuator 10 is applied to an imaging apparatus such as a camera, the lens constitutes a part of an imaging optical system, and when the piezoelectric actuator 10 is applied to an optical pickup apparatus, the lens is a light beam. Part of the pickup optical system. Further, the piezoelectric element 14 is driven by applying a voltage from the drive circuit 21. The electrical conversion element is not limited to a piezoelectric element such as a piezoelectric element, and may be another electrostrictive element.

  A magnetic field generating member 22 is attached to the movable member 18. The magnetic field generating member 22 moves with the movable member 18. A magnetic field detecting member 24 is fixed on the fixing portion 12 so as to face the magnetic field generating member 22. The magnetic field detection member 24 detects a magnetic field generated by the magnetic field generation member 22. As the magnetic field detection member 24, for example, a Hall element or an MR element is preferably used. The magnetic field generating member 22 and the magnetic field detecting member 24 constitute a position sensor 25 that detects the position of the movable member 18.

  The magnetic field detection member 24 is electrically connected to the detection circuit 26, and a detection signal from the magnetic field detection member 24 is input to the detection circuit 26. The detection circuit 26 calculates the position of the movable member 18 by performing arithmetic processing based on the detection signal. The detection circuit 26 is electrically connected to the control circuit 28, and a position detection value by the detection circuit 26 is input to the control circuit 28. The control circuit 28 is for performing positioning feedback control of the movable member 18 by giving a drive command signal to the drive circuit 21 based on the position detection value.

  Next, the operating principle of the piezoelectric actuator 10 will be described. FIG. 2 is a schematic diagram showing the moving state of the movable member 18 on the driving member 16, and FIG. 3 is a graph showing the axial displacement of the driving member 16 on the time axis. That is, a sawtooth drive pulse voltage is applied to the piezoelectric element 14 so that the drive member 16 performs the axial displacement operation as shown in FIG. It should be noted that the states a, b, and c in FIG. 2 and the time points of symbols a, b, and c shown in FIG.

  First, assuming the state a in FIG. 2 as the initial state, when the state transitions from the initial state to the state b in FIG. 2, the piezoelectric element 14 is applied by applying a slowly rising voltage of the sawtooth drive pulse voltage. As shown in FIG. 3, the driving member 16 is displaced in the feeding direction at a moderate speed. At this time, the movable member 18 frictionally engaged with the drive member 16 moves in synchronization with the drive member 16 by the friction engagement force. Next, when the state transitions from the b state to the c state in FIG. 2, the piezoelectric element 14 is rapidly contracted by applying a voltage at the steep falling edge of the sawtooth drive pulse voltage, and is driven accordingly. The member 16 is also rapidly displaced in the return direction as shown in FIG. At this time, slip occurs in the friction engagement portion between the movable member 18 and the drive member 16. Due to this slip, the movable member 18 does not move following the axial displacement of the drive member 16, but only moves slightly in the return direction. As a result, in the c state, compared with the a state which is the initial state. The movable member 18 has moved in the feeding direction. By repeating such an operation, the movable member 18 is moved on the driving member 16 in a feeding direction which is a direction away from the piezoelectric element 14.

  On the other hand, the movable member 18 is moved in a return direction that is a direction approaching the piezoelectric element 14 on the principle opposite to that described above. That is, when the voltage at the steep rising portion of the sawtooth drive pulse voltage is applied, the piezoelectric element 14 rapidly expands, and accordingly, the drive member 16 also rapidly moves in the feeding direction. At this time, slip occurs in the friction engagement portion between the movable member 18 and the drive member 16. Due to this slip, the movable member 18 does not move following the axial displacement of the drive member 16, but moves slightly in the feeding direction. Next, when the voltage at the slowly falling portion of the sawtooth drive pulse voltage is applied, the piezoelectric element 14 is gradually contracted, and the drive member 16 is also moved in the return direction at a moderate speed. At this time, the movable member 18 frictionally engaged with the drive member 16 is displaced in the return direction following the drive member 16 in synchronization with the friction engagement force. As a result, the movable member 18 has moved in the return direction compared to the initial state. By repeating such an operation, the movable member 18 is moved on the drive member 16 in the return direction.

Next, the position sensor 25 and the detection circuit 26 will be described in detail with reference to FIG.
The magnetic field generating member 22 constituting the position sensor 25 is a substantially triangular first magnet that is positively magnetized in the thickness direction (that is, the surface facing the magnetic field detecting member 24 is N-pole and the back surface is S-pole). 22a and a substantially triangular second magnet 22b that is negatively magnetized in the thickness direction (that is, the surface facing the magnetic field detection member 24 is the south pole and the back surface is the north pole). The magnet 22a and the second magnet 22b have a substantially square shape in which the oblique sides of the magnet 22a and the second magnet 22b are fixed to face each other. With such a magnetic field generating member 22, the N pole portion and the S pole portion are gently switched according to the slope shape. Therefore, when the magnetic field generating member 22 is moved in the direction of the arrow D together with the movable member 3, when the magnetic field is observed at a fixed point, the detected surface magnetic flux density is detected so as to change substantially linearly.

  Such a magnetic field generating member 22 is fixed to the movable member 18 so as to face the magnetic field detecting member 24. The magnetic field detection member 24 is configured such that the first magnetic field detection element 24a and the second magnetic field detection element 24b are fixedly juxtaposed along the moving direction of the magnetic field generation member 22. Therefore, when the magnetic field generating member 22 moves in the direction of the arrow D, the magnetic field around the first magnetic field detecting element 24a and the second magnetic field detecting element 24b changes according to the change in the surface gastric magnetic flux density applied from the magnetic field generating member 22. Since these change, the output signals detected by the first and second magnetic field detection elements 24a and 24b also change. Moreover, the magnetic flux density detected by the first magnetic field detection element 24a and the second magnetic field detection element 24b at the same time has a shape in which the magnetic field generating member 22 gradually changes from the N pole portion to the S pole portion. Therefore, different magnetic flux densities are detected depending on the respective arrangement positions. That is, the surface magnetic flux density of the magnetic field generating member 22 takes a positive maximum value in the vicinity of the left end in the figure, becomes zero in the center, and becomes zero in the vicinity of the right end in the figure (absolute value). In addition, since the change is substantially linear, different surface magnetic flux densities are detected at the same time from the first magnetic field detection element 24a and the second magnetic field detection element 24b.

  The detection circuit 26 performs arithmetic processing based on the output values of the first adder 26a and the second adder 26b, and the output values of the first adder 26a and the second adder 26b. 26c.

  The first adder 26a amplifies the output electric signal output by the first magnetic field detection element 24a detecting the magnetic field, and the positive terminal 30a of the first magnetic field detection element 24a is the first adder. It is connected to the non-inverting input terminal 26a. The minus side terminal 32a of the first magnetic field detection element 24a is connected to the inverting input terminal of the first adder 26a.

  On the other hand, the second adder 26b amplifies the output electric signal output by the second magnetic field detection element 24b detecting the magnetic field, and the plus side terminal 30b of the second magnetic field detection element 24b is the second one. It is connected to the inverting input terminal of the adder 26b. The minus side terminal 32b of the second magnetic field detection element 24b is connected to the non-inverting input terminal of the second adder 26b.

  When the electric signal output from the first magnetic field detection element 24a is output A and the electric signal output from the second magnetic field detection element 24b is output B, the computing unit 26c is based on the following equation (1). The calculation result is transmitted to the control circuit 28 as a position detection value.

  The purpose of causing the arithmetic unit 26c to execute such arithmetic processing of (A−B) / (A + B) is to improve the operating environment temperature characteristic of the position signal of the movable member 18 detected by the detection circuit 26. That is, in general, when the environmental temperature of a magnet changes, the magnetic flux density changes due to its temperature characteristics. For example, when the environmental temperature rises, the surface magnetic flux density decreases due to the temperature characteristics of the first magnet 22a and the second magnet 22b included in the magnetic field generating member 22. Accordingly, the output values of the first and second magnetic field detection elements 24a and 24b also tend to decrease as the environmental temperature increases. The arithmetic unit 26c performs arithmetic processing so that the position of the movable member 18 can be detected without being affected by the decrease in the output values of the first and second magnetic field detection elements 24a and 24b due to such changes in the operating environment temperature. Is to do.

  In the present embodiment, a magnetic sensor is used as the position sensor. However, the position sensor is not limited to this, and a position sensor of another system (for example, a capacitance type or an optical type) may be used.

Next, position feedback control of the positioning device 10 will be described.
FIG. 5 shows the relationship between the position of the movable member 18 and the lens tilt in the positioning device 10 of the present embodiment. In the positioning device 10, for example, when a position command signal is input to the control circuit 28 from the main body control unit of the photographing apparatus, the control circuit 28 transmits a drive command signal to the drive circuit 21. As a result, the drive circuit 21 applies a drive voltage to the piezoelectric element 14 to drive the movable member 18. The position of the movable member 18 is detected at any time by the position sensor 25, and the position detection value is input from the detection circuit 26 to the control circuit 28. As shown in FIG. 5, the control circuit 28 drives the movable member 18 until the difference between the commanded target position and the position detection value by the position sensor 25 becomes zero.

  If the drive of the movable member 18 is stopped immediately when the movable member 18 reaches the target position, the movable member 18 is inclined due to the moment of inertia of the movable member 18, and the lens held by the movable member 18 is also inclined. To do. When the inclination of the movable member 18 is an angle θ from the orthogonal plane with respect to the drive member 16, it can be expressed by the following formula (2), and FIG.

  In the following equation of motion, J represents a moment of inertia based on the friction holding point X of the movable member 18 with respect to the drive member 16, C represents a vibration damping coefficient, and K represents a spring constant. Here, referring to FIG. 9, the friction holding portion 5 of the movable member 4 is driven in contact with the friction holding portion 5 by being pressed against the driving member 3 by a biasing force of a biasing member such as a leaf spring (not shown). A predetermined frictional force is generated between the member 3 and the movable member including the lens holder 6 and the friction holding unit 5 because the friction holding unit 5 is only pressed against the driving member 3 by the biasing member. 4 is rotatable with an elastic restoring force in a certain angle range in the direction of arrow C (or the reverse direction) from the state shown in the figure. Therefore, the movable member and the lens are inclined as described above. The elastic restoring force at this time is expressed by the spring constant K, and the spring constant K is also expressed as a friction holding torque. The This spring constant K (that is, friction holding torque) is the same for the positioning device 10 of this embodiment.

  As shown in FIG. 6, when the driving of the movable member 18 is stopped immediately after reaching the target position, a considerably large inclination is generated in the movable member 18 holding the lens immediately after the stop. Therefore, in the positioning device 10 of this embodiment, in order to suppress the tilt of the movable member 18 (that is, the lens), after the movable member 18 reaches the target stop position, the following position feedback control is further performed for a predetermined time or more. continue.

  As shown in FIG. 5, the control circuit 28 continues to drive the movable member 18 even after the movable member 18 reaches the target stop position, slightly overshoots, and then drives back in the reverse direction. Perform positioning control at least once. By performing such control, the tilt of the movable member 18 and the lens can be suppressed to a slight extent as compared with the case where the driving of the movable member 18 is stopped immediately when the target stop position is reached (see FIG. 10). Further, position feedback control such as returning the movable member 18 after overshooting can be handled by a general control circuit 28 that is normally used, so that the configuration can be simplified and inexpensive.

  The control for overshooting the movable member 18 as described above is performed as follows. The positioning device 10 of the present embodiment can be represented by the control block diagram shown in FIG. 7, and the control circuit 28 is configured such that the behavior of the position x of the movable member 18 is damped and vibrational with overshoot based on the equation of motion. The integral gain Ki is selected so as to be a certain one.

  The control circuit as described above is generally called a PI controller, P means proportionality, and I means integration. Also, Kp is referred to as a proportional gain, Ki is referred to as an integral gain, and when Ki is selected as described above, a control system in which overshoot occurs.

  The predetermined time during which the positioning control with overshoot is continued is determined by the inertia of the movable member 18 centered on the friction holding point X of the movable member 18 and the friction holding torque of the movable member 18 with respect to the driving member 16. It is preferable that the time is half or more of the vibration period fr. In this way, the inclination of the movable member 18 generated when the drive of the movable member 18 stops is damped and vibration. Therefore, the positioning control with overshoot is continued for more than half of the natural vibration period fr, thereby allowing the movable member 18 to move. The slope is small enough that there is no problem.

  The upper limit of the predetermined time is not particularly limited, but if it is too long, it takes time to position the lens, and the usability of the photographing device, the optical pickup device, etc. is deteriorated. For example, when the positioning device 10 is used in an optical pickup optical system of a DVD drive, the average access time of the DVD drive is about 150 msec, and the time required for positioning the pickup lens is about 1/10. In this case, for example, 15 msec is appropriate as the upper limit of the predetermined time.

  The predetermined time may be n / 2 of the natural vibration period fr (n is a natural number starting from 1). Specifically, the positions of the circles 34, 36, and 38 on the time axis indicating the lens tilt in FIG. 5 are times of n / 2 of the natural vibration period fr. In this manner, the movable member 18 can be positioned without tilting the movable member 18 by stopping the positioning control with overshoot at the time of n / 2 of the natural vibration period fr.

Here, the natural vibration period of the movable member 18 is expressed by the following equation (3).

Next, a positioning device 40 according to a second embodiment of the present invention will be described with reference to FIG.
The positioning device 40 has substantially the same configuration as the piezoelectric actuator S described as the conventional example. That is, in the piezoelectric actuator 40, the driving member 46 is fixed to the other end of the piezoelectric element 44 whose one end is fixed to the fixing portion 42, and the movable member 48 is movably held on the driving member 46. The movable member 48 includes a friction holding unit 50 that is engaged with the driving member 46 by a frictional force, and a lens holder 52 that is connected to the friction holding unit 50 and holds a lens (not shown). With respect to the movable member 48, the friction holding point X is located at the center portion of the friction holding portion 5, and the center of gravity G of the movable member 48 is located substantially at the center portion of the lens holder 52.

  A guide shaft 54 disposed in parallel with the drive member 46 is engaged in the vicinity of the end portion of the lens holder 52, and the drive member is controlled by the guide shaft 54 while turning around the drive member 46 is restricted. A movable member 48 that moves along 46 is guided.

  The positioning device 40 also includes a position sensor 60 including a magnetic field generating member 56 provided on the movable member 48 and a magnetic field detecting member 58 fixedly disposed on the fixed portion 57 so as to face the magnetic field generating member 56. . The position sensor 60 is the same as the position sensor 25 in the positioning device 10 of the first embodiment described above.

  In the piezoelectric actuator S of the conventional example, the magnet 8 is provided at the tip of the movable member 48 separated from the drive shaft 3. However, in the positioning device 40, the center of gravity G of the movable member 48 with reference to the friction holding point X of the movable member 48. A magnetic field generating member 56 is provided on the friction holding portion 50 of the movable member 48 in a direction opposite to the direction in which the position is located.

  Since the drive circuit, the detection circuit, and the control circuit are provided, and the operation and control of the positioning device 40 are the same as those of the positioning device 10 of the first embodiment, description thereof is omitted here.

  As described above, in the positioning device 40 of the present embodiment, since the magnetic moment generating member 56 is provided on the driving member 46 side of the movable member 48, the moment of inertia of the movable member 48 is reduced. The inclination of the movable member 48 and the lens held by the movable member 48 in the direction of arrow C can be reduced.

  By the way, when the positioning devices 10 and 40 are applied to an optical pickup device, the lenses held by the movable members 18 and 48 become the lenses of the optical pickup optical system, and the aberration is caused by the movement of the lenses in the optical axis direction. Correction is performed. In this case, since the movable members 18 and 48 can be positioned while suppressing the tilt of the lens, the aberration can be corrected with high accuracy.

  Further, the duration of the positioning control with overshoot performed after the movable members 18 and 48 once reach the target stop position may be equal to or longer than the optical disk rotation period. In this way, it becomes possible to correct in real time the aberration based on the change in the thickness of the protective layer of the optical disc that occurs within one circumference of the optical disc, and the reliability of the optical disc apparatus can be improved.

The system block diagram of the positioning device of 1st Embodiment. The figure for demonstrating the action | operation principle of the piezoelectric actuator shown in FIG. The figure which shows the axial displacement of the drive member of a piezoelectric actuator. 3 is a detailed view of a magnetic field generating member, a magnetic field detecting member, and a detection circuit. The graph which shows the position and lens inclination of a movable member when performing positioning control with an overshoot. The graph which shows the inclination of the movable member after a drive stop immediately at a target position. The control block diagram of a positioning device. The block diagram of the positioning device of 2nd Embodiment. The block diagram of the friction drive type piezoelectric actuator with a position sensor of a prior art example. The graph which shows the position of the movable member and lens inclination in the piezoelectric actuator of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Positioning device 12 ... Fixed part 14 ... Piezoelectric element (electric conversion element)
DESCRIPTION OF SYMBOLS 16 ... Drive member 18 ... Movable member 20 ... Piezoelectric actuator 21 ... Drive circuit 22 ... Magnetic field generation member 24 ... Magnetic field detection member 25 ... Position sensor 26 ... Detection circuit 28 ... Control circuit

Claims (10)

A piezoelectric actuator comprising an electromechanical transducer, a driving member fixed to one end of the electromechanical transducer, and a movable member frictionally held on the driving member;
A drive circuit for driving the electromechanical transducer;
A position sensor for detecting the position of the movable member;
A detection circuit for processing a signal from the position sensor;
A control circuit that performs position feedback control of the movable member by giving a drive command signal to the drive circuit based on a position detection value by the detection circuit,
In the positioning operation of the movable member, the control circuit further continues positioning control with overshoot for a predetermined time or more after the movable member once reaches a target stop position.   The predetermined time is a half time of a natural vibration period of the movable member determined from an inertia moment centered on a friction holding point of the movable member and a friction holding torque of the movable member with respect to the driving member. The positioning device according to claim 1.   The positioning device according to claim 2, wherein the predetermined time is n / 2 of the natural vibration period (n is a natural number starting from 1). A piezoelectric actuator comprising an electromechanical transducer, a driving member fixed to one end of the electromechanical transducer, and a movable member frictionally held on the driving member;
A drive circuit for driving the electromechanical transducer;
A position sensor for detecting the position of the movable member;
A detection circuit for processing a signal from the position sensor;
A control circuit for performing positioning control of the movable member by giving a drive command signal to the drive circuit based on a position detection value by the detection circuit,
The position sensor includes a magnetic field generating member provided on the movable member and a magnetic detection member provided on the fixed portion, and a direction in which the center of gravity of the movable member is located with reference to a friction holding point of the movable member. A positioning apparatus, wherein the magnetic field generating member is provided on the movable member in the opposite direction.   The positioning apparatus according to claim 1, wherein the movable member holds an optical element.   The positioning device according to claim 5, wherein an optical axis of the optical element is parallel to a moving direction of the movable member.   The positioning apparatus according to claim 5, wherein the optical element forms part of a photographing optical system.   6. The positioning apparatus according to claim 5, wherein the optical element forms part of an optical pickup optical system.   9. The positioning apparatus according to claim 8, wherein the optical element is a lens of an optical pickup optical system, and the aberration is corrected by moving the lens in the optical axis direction.   The positioning device according to claim 8 or 9, wherein a duration time of positioning control with overshoot performed after the movable member once reaches a target stop position is equal to or longer than an optical disk rotation period.

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