JP2008292386A - Position detector, driving device, and optical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detector compact with high linearity, a driving device and optical equipment. <P>SOLUTION: The position detector comprises: a magnetic field generating member 7 with magnetic field variation configured to polarize only one each of N-pole and S-pole in the advancing/retreating direction (a) of a movable member 3 so that surface magnetic flux density varies in the advancing/retreating direction of the movable member 3; and a magnetic field detecting means 6 comprising two magnetic field detecting elements 6A, 6B arranged with a space A in the advancing/retreating direction of the movable member and detecting magnetic field variation associated with the movement of the magnetic field generating member 7. The magnetic field generating member 7 is configured such that the space A between the two magnetic field detecting elements 6A, 6B forming the magnetic field detecting means 6 is L/4<A<L/4+t/2, wherein L is an advancing/retreating direction length, and t is the thickness. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a position detection device that detects the position of a movable body by detecting a change in a magnetic field, and a drive device equipped with the position detection device, and in particular, an optical apparatus such as an imaging device such as a digital camera or an optical pickup. The present invention relates to a position detecting device applied to a lens driving mechanism and the like, and driving of the driving device.

  Patent Documents 1 and 2 describe a position detection device that detects a position of a movable member as a change in magnetic field by a magnetic field generating member attached to the movable member by a magnetic field detection unit.

  FIG. 11 shows a schematic configuration of the position detection device described in Patent Document 1. In the position detection device 100 shown in FIG. 11, the N pole portion 102 having a width of 1 / 2δ magnetized to the N pole and the S pole portion 103 having a width of 1 / 2δ magnetized to the S pole are alternately repeated. The magnetic field generation member 104 is disposed, and two magnetic field detection elements 105a and 105b are provided. The period of the magnetic pole of the magnetic field generating member 104 is δ. The two magnetic field detection elements 105a and 105b are provided with a distance of (1 + 1/4) δ. The detection signals A and B from the magnetic field detection elements 105a and 105b amplified by the amplifiers 106a and 106b are processed by the arithmetic unit 107 and output.

  Thus, the reason why the two magnetic field detection elements 105a and 105b are provided at intervals of ¼ period with respect to the magnetic field period δ is that the linearity of position detection is the best. That is, when a magnetic field that changes in a substantially sine wave shape with respect to the moving direction of the movable member is detected by two magnetic field detection elements, the position detection accuracy is improved by setting the interval between the two magnetic field detection elements to (n + 1/4) δ. Can be increased.

  FIG. 12 shows a schematic configuration of the position detection device described in Patent Document 2. The position detection device 110 shown in FIG. 12 includes a magnetic field generating member 114 in which two magnets 113a and 113b having N poles and S poles arranged in the thickness direction are arranged to face each other, and two magnetic field detections. It has elements 115a and 115b. This position detection device differs from the position detection device shown in FIG. 11 in that the magnetic field generating member 114 is composed of one N pole and one S pole, and there is no disclosure about the interval between the two magnetic field detection elements. In the drawing, the interval is about 1/10 of the length of the magnets 113a and 113b constituting the magnetic field generating member 114.

  FIG. 13 shows a schematic configuration of a position detecting device having another configuration described in Patent Document 1. The position detection device shown in FIG. 13 is a magnetic field in which two magnets 123 and 124 having N and S poles arranged in the thickness direction are arranged with their sides facing each other, and a non-magnetized portion 125 is arranged therebetween. A generation member 121 and a magnetic field detection means 122 including two magnetic field detection elements 126a and 126b are provided. The detection signals A and B from the magnetic field detection elements 126a and 126b amplified by the amplifiers 127a and 127b are processed by the calculation device 1128 and output.

Patent Document 1 discloses the distance between the magnetic field generation member 121 and the two magnetic field detection elements in the position detection apparatus having the above configuration. The magnetic field generation member has a total length of 6.2 mm and a width of 2, for example. It is disclosed that the thickness is 0.5 mm and the thickness is 1.0 mm, and the distance between the two magnetic field detection elements 126a and 126b is 1.6 mm. When calculated from this numerical value, the interval between the two magnetic field detection elements 126a and 126b is approximately 1 / 3.87 of the magnetic field period, and as described above, approximately 1 / 0.8 with respect to the magnetic field period δ in order to improve linearity. An interval of 4 periods is provided.
JP 2006-292396 A Japanese Patent Laid-Open No. 1-150812

  However, in the position detection device having a magnetic field generating member provided with one S pole and one N pole shown in FIGS. 12 and 13, it is difficult to ensure high linearity of position detection. There has been a demand for a position detection device that can perform accurate position detection.

  Accordingly, the technical problem to be solved by the present invention is to provide a compact, highly linear position detecting device, driving device, and optical apparatus.

  In order to solve the above technical problem, the present invention provides a position detection device having the following configuration.

According to the first aspect of the present invention, it is integrally attached to a movable member configured to be able to advance and retract, and only one each of the N pole and the S pole is magnetized in the advance and retreat direction of the movable member, so that the surface magnetic flux density is movable. A magnetic field generating member having a magnetic field change configured to change in the advancing and retracting direction of the member;
Magnetic field detection means comprising two magnetic field detection elements that are arranged side by side in the advance and retreat direction of the movable member at intervals A, detecting a magnetic field change accompanying the movement of the magnetic field generating member based on the advance and retreat operation of the movable member;
Calculating means for obtaining a position of the movable member based on a detection signal of the magnetic field detecting means;
The magnetic field generating member has a length L in the forward / backward direction and a thickness t,
The distance A between the two magnetic field detection elements constituting the magnetic field detection means is:
L / 4 <A <L / 4 + t / 2
A position detection device is provided that is configured to be as follows.

  According to the second aspect of the present invention, the magnetic field generating member includes: a rectangular first magnet that is positively magnetized in the thickness direction; and a rectangular second magnet that is negatively magnetized in the thickness direction. A position detection device according to a first aspect is provided, which is provided and has a substantially square shape in which the sides of the first magnet and the second magnet are fixed to face each other.

  According to a third aspect of the present invention, there is provided the position detection device according to the first or second aspect, wherein the magnetic field detection element is a Hall element.

According to a fourth aspect of the present invention, any one of the position detection devices according to the first to third aspects;
An electromechanical transducer having one end fixed to the frame to which the magnetic field detecting means is fixed and extending and contracting in the movable direction;
A guide shaft connected to the other end of the electromechanical conversion element and frictionally engaged with the movable member;
A drive device is provided.

According to a fifth aspect of the present invention, there is provided an optical apparatus comprising a mechanism in which at least one optical element is disposed on an optical axis,
An optical apparatus is provided in which the movable device in the driving device according to the fourth aspect is configured to function as a holding body that holds the optical element and moves the optical element back and forth on its guide shaft.

  According to the sixth aspect of the present invention, the optical element is held by the movable member so that the optical axis of the optical element and the advancing / retreating direction of the movable member are parallel to each other. Provide equipment.

  According to a seventh aspect of the present invention, there is provided the optical instrument according to the fifth aspect, wherein the optical instrument is an imaging device, and the optical element is an optical element constituting a part of the photographing optical system. .

  According to an eighth aspect of the present invention, there is provided the optical instrument according to the seventh aspect, wherein the optical instrument is an optical pickup device, and the optical element is an optical element constituting a part of the optical pickup optical system. provide.

  According to the ninth aspect of the present invention, the optical element is a lens of an optical pickup optical system, and the lens is moved in the optical axis direction by the advance / retreat operation of the movable member, so that aberration correction is performed. An optical device according to an eighth aspect is provided.

  According to the present invention, in a position detection device including a magnetic field generating member having one S pole and one N pole and a magnetic field detection means including two magnetic field detection elements, the interval A between the two magnetic field detection elements is set to a magnetic field period. The linearity can be enhanced by making the dimension determined by the thickness dimension of the magnetic field generating means larger than ¼. That is, in the magnetic field generating member having one S pole and one N pole, the magnetic field generated at both ends of the magnetic field generating member is not affected by the outer magnet, and therefore the magnetic flux greatly wraps around the magnet. Therefore, the position where the magnetic flux becomes flat is outside the end of the magnetic field generating member. Therefore, the interval at which the detection values detected by the magnetic field detection member cross zero in the same direction is wider than the size of the magnet of the magnetic field generation member. In other words, in the above configuration, the magnetic field period detected by the magnetic field detection member is longer than the distance between the two poles of the magnets constituting the magnetic field generation member. Therefore, the position detection accuracy of the position detection device can be increased by providing an interval slightly longer than ¼ of the magnetic field period.

  Further, according to the position detection device of the second aspect, since the positive magnetization portion and the negative magnetization portion are linearly switched, it is possible to cause a large magnetic field fluctuation even with a minute movement of the movable member. The detection accuracy can be increased in an apparatus in which the movable member moves within a relatively narrow range.

  If a Hall element is used as the magnetic field detection element, since the Hall element is generally small, it can be easily incorporated into the apparatus and is inexpensive. Therefore, the position detection apparatus can be provided in a small and inexpensive manner.

  In addition, according to the drive device of the fourth aspect of the present invention, a small drive device with high detection accuracy is provided by combining a position detection device with high detection accuracy and a drive device using an electromechanical transducer. Can do.

  According to the optical device according to the fifth aspect or the sixth aspect, the movement control of the optical element included in the various optical devices on the optical axis is performed by the driving device according to any one of the above aspects of the present invention. Since it is configured, it is possible to accurately detect the position of the movable member without being affected by changes in the operating environment with a low-cost and simple configuration.

  According to the optical device of the seventh aspect, in an imaging apparatus such as a digital camera, the driving of the zoom lens or the like assembled in the imaging optical system is affected by changes in the operating environment with a low cost and simple configuration. Therefore, it can be performed with high accuracy.

  According to the optical device of the eighth aspect, in the optical pickup, the driving of the lens and the like assembled in the pickup optical system can be performed with a low cost and a simple configuration with high accuracy without being affected by the change in the operating environment. be able to. Moreover, according to the optical apparatus concerning a 9th aspect, it is the structure which performs an aberration correction with the drive device of the said aspect, The convenience of the said drive device can be improved more.

  Hereinafter, a drive device using a position detection device according to an embodiment of the present invention will be described with reference to the drawings.

(overall structure)
FIG. 1 is a system configuration diagram of a drive device S equipped with a position detection device according to an embodiment of the present invention. The driving device S is integrally attached to a piezoelectric actuator P (driving means), a driving circuit 4 and a control circuit 5 for driving the piezoelectric actuator P, and a movable member 3 included in the piezoelectric actuator P, and has a surface in a forward and backward direction. The magnetic field generating member 7 whose magnetic flux density is changed, the magnetic field detecting means 6 for detecting the magnetic field generated by the magnetic field generating member 7, and the position of the movable member 3 based on the detection signal of the magnetic field detecting means 6 And a detection circuit 8 to be obtained. The magnetic field detection means 6, the magnetic field generation member 7, and the detection circuit 8 constitute a position sensor unit of the movable member 3.

  The piezoelectric actuator P includes an electromechanical conversion element 1, a drive member (guide shaft) 2 fixed to one end of the electromechanical conversion element 1, and a movable member 3 movably held on the drive member 2. It is configured. As the electromechanical conversion element 1, a piezoelectric element such as a piezoelectric element can be preferably used. The driving member 2 is fixed to one end side of the electrostrictive direction (stretching direction) of the electromechanical conversion element 1 (hereinafter referred to as piezoelectric element 1) by a technique such as adhesion. It is moved in the direction of arrow a in the figure. On the other hand, the other end side of the piezoelectric element 1 is fixed to a fixing portion 9 (a main body or the like of the driving device S), thereby restricting the extending direction of the piezoelectric element 1.

  The movable member 3 is a member that applies a moving force to a driven body such as a lens barrel or a movable piece of a precision stage. The movable member 3 is provided with a through hole, and is attached to the drive member 2 with a predetermined frictional engagement force in such a manner that the drive member 2 is inserted into the through hole.

  2A and 2B are diagrams for explaining the operation principle of the piezoelectric actuator P as described above, and FIG. 2A is a schematic diagram showing the advancing / retreating operation state of the movable member 3 on the driving member 2. 2B is a graph showing the axial displacement of the driving member 2 on the time axis. That is, a sawtooth drive pulse voltage is applied to the piezoelectric element 1 so that the drive member performs an axial displacement operation as shown in FIG. 2B. 2A (a), (b), (c) and the time points of (a), (b), (c) added in FIG. ing.

  First, assuming that the state of FIG. 2A (a) is an initial state, when the state is shifted to the state of FIG. 2A (b), that is, when extending in the feeding direction, as shown in the graph of FIG. 2) Elongates and displaces gently. Accordingly, the drive member 2 is also moved in the feeding direction at a moderate speed, so that the movable member 3 frictionally engaged with the drive member 2 is displaced in synchronization with the friction engagement force. Next, when transitioning from the state of FIG. 2A (b) to the state of FIG. 2A (c), that is, when the voltage at the sharp falling portion of the sawtooth drive pulse voltage is applied to the piezoelectric element 1, the piezoelectric element 1 It rapidly shrinks and displaces. Along with this, the drive member 2 is also moved in the return direction at a steep speed, so that slip occurs between the movable member 3 and the friction engagement portion of the drive member 2. Due to this slip, the movable member 3 does not move following the axial displacement of the drive member 2 but slightly returns in the return direction. By repeating such an operation, the movable member 3 is moved in the direction away from the piezoelectric element 1 on the axis of the drive member 2.

  As the driving means used in the present embodiment, it is desirable to use a so-called “non-magnetic source type” driving means like the piezoelectric actuator P described above. Specifically, the surface magnetic flux density generated as the movable member 3 provided in the driving means moves is 0.1 mT or less, while the maximum surface magnetic flux density generated by the magnetic field generating member 7 is 1 mT or more. It is desirable. Thus, by suppressing the surface magnetic flux density generated by the operation of the driving means to about 1/10 or less of the surface magnetic flux density generated by the magnetic field generating member 7, the detection signal of the magnetic field detecting means 6 is caused by the leakage magnetic flux. Without being disturbed, highly accurate positioning of the movable member 3 can be achieved.

  As such “non-magnetic source type” driving means, in addition to the piezoelectric actuator P configured as described above, an ultrasonic actuator that moves the movable member 3 back and forth using an ultrasonic motor, and a movable member that uses a shape memory member. For example, a shape memory actuator that moves 3 forward and backward can be exemplified.

  Returning to FIG. 1, the control circuit 5 receives a position command (displacement command for the movable member 3) given from a host computer (not shown), and generates a drive control signal for moving the movable member 3 to the command position. . This drive control signal is generated so that the movable member 3 moves by a predetermined movement amount according to the difference between the position signal of the movable member 3 transmitted from the detection circuit 8 and the position signal based on the position command. The

  The drive control signal generated in this way is input to the drive circuit 4. Based on the drive control signal, the drive circuit 4 generates a drive signal for driving the piezoelectric element 1 so that the movable member 3 moves by a predetermined movement amount, and actually drives the piezoelectric element 1.

  The magnetic field generating member 7 is integrally attached to the movable member 3, and the magnetic field generating member 7 is also moved in the forward / backward direction according to the forward / backward movement of the movable member 3. The magnetic field generating member 7 may be directly fixed to the movable member 3, but may be indirectly attached to the movable member 3 by being fixed to a driven member attached to the movable member 3. . As the magnetic field generating member 7, a member whose surface magnetic flux density is changed in the advancing and retracting direction of the movable member 3 is used. There is no particular limitation on the change mode of the surface magnetic flux density, and it is only necessary to have a change mode in which a change in the surface magnetic flux density due to its own advance / retreat movement acts on the magnetic field detection means 6 that is fixedly arranged. Specific examples thereof will be described in detail later.

  The magnetic field detection means 6 detects a change in the magnetic field associated with the movement of the magnetic field generating member 7 based on the advance / retreat operation of the movable member 3, and is a first fixedly juxtaposed in the vicinity of the moving path of the magnetic field generating member 7. A magnetic field detection element 6A and a second magnetic field detection element 6B are provided. Further, in this embodiment, an example is shown in which two magnetic field detection elements 6A and 6B are juxtaposed along the moving direction of the movable member 3. However, the magnetic field generating member 7 also extends in the direction perpendicular to the plane of the advance / retreat direction. In the case where a surface magnetic flux density change appears, a plurality of magnetic field detecting elements can be arranged in parallel in the orthogonal direction.

  Various magnetic sensors can be used as the magnetic field detection elements 6A and 6B. As a typical example, a magnetic field detection element that outputs an electric signal in accordance with a detected magnetic field, such as an MR element using a magnetoresistance effect or a Hall element using a Hall effect, can be exemplified. Among these, the Hall element can be suitably used because it is generally small in size, excellent in incorporation into this kind of driving device S, and inexpensive.

  The detection circuit 8 functions as calculation means for obtaining the position of the movable member 3 based on the detection signal of the magnetic field detection means 6. That is, the magnetic field detection signals respectively detected by the first magnetic field detection element 6A and the second magnetic field detection element 6B are input to the detection circuit 8, and the two magnetic field detection signals are amplified and calculated, thereby moving the movable member. 3 is generated as position information which is current position information. The position signal generated here is output to the control circuit 5.

(Configuration of position detection device)
FIG. 3A is a block diagram showing in detail an example of a position detection device including a portion of the drive device S that constitutes the position detection device, that is, a magnetic field detection means 6, a magnetic field generation member 7, and a detection circuit 8. . In this embodiment, as the magnetic field generating member 7, one positive magnetized portion in which positive magnetization is dominant and one negative magnetized portion in which negative magnetization is dominant along the advancing / retreating direction of the movable member 3. What is provided with is used. With such a magnetic field generating member 7, the magnetic field generating members having different magnetic generation conditions of the positive magnetized portion and the negative magnetized portion in the advance / retreat direction of the movable member 3 move according to the advance / retreat of the movable member 3. There is an advantage that the magnetic field fluctuation due to the advance and retreat of the movable member becomes large.

  As a specific configuration, in FIG. 3A, a rectangular first magnet 7A that is positively magnetized in the thickness direction (that is, the surface facing the magnetic field detection means 6 is N-pole and the back surface is S-pole); A rectangular second magnet 7B negatively magnetized in the thickness direction (that is, the surface facing the magnetic field detecting means 6 is the S pole and the back surface is the N pole), and the first and second magnets The magnetic field generating member 7 having a substantially rectangular shape in which the sides of 7A and 7B are fixed to face each other is illustrated. Therefore, the surface magnetic flux density of the magnetic field generating member 7 takes a positive maximum value in the vicinity of the left end in the figure, zero in the center, and zero in the center, and a negative maximum value (absolute value) in the vicinity of the right end in the figure. Take. As the dimensions of the magnetic field generating member 7, the thickness direction dimension t is, for example, 1.2 mm, the length direction dimension L is 4.8 mm, and the height dimension H is, for example, 1.5 mm.

  With this configuration, the magnetic field detected by the first magnetic field detection element 6A and the second magnetic field detection element 6B is in each magnetic field detection element at the boundary between the first magnet 72A and the second magnet 72B. Since it changes greatly before and after passage of the detection point, it is also suitable for the driving device S in which the movable range of the movable member 3 is relatively narrow.

  Further, since the magnetic field generating member 7 has a double magnetizing system of the first magnet 72A and the second magnet 72B, the magnetic flux generated by the magnetic field generating member 72 is in a direction perpendicular to the magnetic field detecting means 6 arranged to face each other. It penetrates in the direction extending from the back of the drawing to the front. Accordingly, the magnetic flux acting on the magnetic field detection means 6 increases, and the magnetic field detection can be performed with high sensitivity.

  Such a magnetic field generating member 7 is fixed to the movable member 3 so as to face the magnetic field detecting means 6. The first magnetic field detection element 6A and the second magnetic field detection element 6B are fixedly juxtaposed at an interval A (for example, 1.5 mm) along the advancing / retreating direction of the magnetic field generating member 7. Therefore, when the magnetic field generating member 7 moves in the direction of the arrow a, the magnetic field around the first magnetic field detecting element 6A and the second magnetic field detecting element 6B changes according to the change in the surface magnetic flux density applied from the magnetic field generating member 7. Since these change, the output signals detected by the first and second magnetic field detection elements 6A and 6B also change. In addition, since the first magnetic field detection element 6A and the second magnetic field detection element 6B are arranged at an interval A, the magnetic flux density detected by both at the same time detects different positions of the magnetic field generating member 7. However, different detection signals are generated.

  The width of the magnetic field generating member 7 in the advancing / retreating direction is selected so that the opposing relationship between the magnetic field generating member 7 and the magnetic field detecting means 6 can be ensured regardless of the position of the movable member 3 in the moving stroke range. It is desirable. That is, when the magnetic field detection means 6 is fixedly disposed opposite to the magnetic field generating member 7 that performs an advance / retreat operation integrally with the movable member 3, the magnetic field generation is performed over the entire area of the advance / retreat operation region of the movable member 3. It is desirable to select the shape of the magnetic field generating member 7 so that the lines of magnetic force from the member 7 act on the magnetic field detecting means 6. Such a configuration is preferable because the movable member 3 can detect the position of the movable member 3 in the entire stroke range. If the gap between the magnetic field generating member 7 and the magnetic field detecting means 6 is too far, the detection accuracy is lowered, and if it is too close, there is a risk that the magnet 7 and the magnetic sensor 6 come into contact with each other. It is desirable to set to.

  The distance A between the two magnetic field detection elements 6A and 6B preferably takes a value calculated according to the length dimension and the thickness dimension of the magnetic field generating member 7. That is, the interval A between the two magnetic field detection elements 6A and 6B is different in the value of the detection signal output from the two magnetic field detection elements 6A and 6B, and the position detection accuracy of the movable member 3 is determined by the output from the two signals. Therefore, it should be adjusted so that the accuracy of position detection is most enhanced.

  In general, the interval A is preferably about ¼ of the magnetic field period. However, in this embodiment, the interval A is slightly less than ¼ of the magnetic field period (that is, the length dimension L of the magnetic field generating member 7). The length of the adjustment is a value determined by the thickness dimension t of the magnetic field generating member 7. Hereinafter, this reason will be described in detail.

  FIG. 4 is a schematic diagram when the magnetic field detection element 6x is relatively moved along the magnetic field fluctuation direction of the magnetic field generating member 7x in which the positive magnetic attachment and the negative magnetic attachment are repeatedly performed, and an output signal from the magnetic field detection element 6x. It is a figure which shows a value. When the position detection structure shown in FIG. 4 is adopted, the magnetic field detection element 6x moves relative to the magnetic field repeatedly provided in the x-axis direction in the x-axis direction. As shown in FIG. 4A, the magnetic flux M generated from the magnetic field generating member 7x does not extend across the front and back sides of the magnetic field generating member 7x from the N pole to the adjacent S curve. Therefore, only the magnetic flux M generated on the magnetic field detection element 6x side determines the output value of the detection signal of the magnetic field detection element 6x. Since the magnetic field detection element 6x detects only the component of the magnetic flux M in the z-axis direction, the output value is 0 at the boundary between the positive and negative magnetic attachments, and at the central portion between the positive and negative magnetic attachments. Output value is the maximum. Therefore, the output value from the magnetic field is a sine wave as shown in FIG.

  In this case, the period of the output signal of the magnetic field detection element 6x coincides with the magnetic field period (that is, the dimension of the magnetization pitch L). Therefore, when position detection is performed using the two magnetic field detection elements 6x, the two magnetic field detection elements 6x are simply arranged at intervals of 1/4 of the period of the output value of the magnetic field detection element 6x. The accuracy of position detection can be improved.

  On the other hand, in the case where there is one positive magnetic attachment and one negative magnetic attachment, the error increases when the distance between the two magnetic field detection elements 6x is set in this way. FIG. 5 is a schematic diagram when the magnetic field detection element 6 moves relative to the magnetic field variation direction of the magnetic field generating member 7x having one positive magnetic attachment and one negative magnetic attachment, and an output signal from the magnetic field detection element 6x. It is a figure which shows a value. When the above configuration is adopted, the magnetic flux M generated from the magnetic field generation member 7x is generated on the magnetic field detection element side in the central portion of the magnetic field generation member 7x as shown in FIG. Then, since there is no magnetized part on the outer side, it occurs between the front and back of the same magnetized part while wrapping around the same magnetized part. As a result, the detection value of the magnetic field detection element 6x at both end positions of the magnetic field generation member 7x does not become 0, but becomes the detection value 0 at the point f outside the magnetic field generation member 7x. Since the position of the point f is determined by the magnetic flux that goes around the same magnetized portion, if the magnetic field generating member 7x is thick, it becomes a larger arc magnetic flux and shifts outward.

  Therefore, the output signal of the magnetic field detection element 6x has a value substantially close to a sine wave, but the period is longer than the magnetic field period (that is, the dimension of the magnetization pitch L) and is the distance between the points f and f. . The extension α with respect to the magnetic field period varies depending on the thickness dimension of the magnetic field generating member 7x.

  For the above reason, in this embodiment, the distance A between two adjacent magnetic field detection elements 6A and 6B is set to be longer than ¼ of the magnetic field period (that is, the length dimension L of the magnetic field generating member 7). It is set so that 4 <A <L / 4 + t / 2.

  In this embodiment, the detection circuit 8 performs arithmetic processing based on output values of the first adder 8A and the second adder 8B, which are operational amplifiers, and the first adder 8A and the second adder 8B. And an arithmetic unit 8C.

  The first adder 8A amplifies the output electric signal output by the first magnetic field detection element 6A detecting the magnetic field, and the positive side terminal 61A of the first magnetic field detection element 6A is the first adder. It is connected to the non-inverting input terminal of 8A. The negative terminal 62A of the first magnetic field detection element 6A is connected to the inverting input terminal of the first adder 8A.

  On the other hand, the second adder 8B amplifies the output electric signal output by detecting the magnetic field by the second magnetic field detection element 6B, and the plus side terminal 61B of the second magnetic field detection element 6B is the second addition. Connected to the inverting input terminal of the device 8B. The minus side terminal 62B of the second magnetic field detection element 6B is connected to the non-inverting input terminal of the second adder 8B.

  As described above, the first magnetic field detection element 6A and the second magnetic field detection element 6B change the polarities connected to the first adder 8A and the second adder 8B, respectively. The magnetic field detection element 6A predominantly detects the N pole magnetic flux of the magnetic field generation member 7, while the second magnetic field detection element 6B predominantly detects the S pole magnetic flux of the magnetic field generation member 7, thereby reversing the polarity. This is because the arithmetic unit 8C in the subsequent stage easily performs arithmetic processing.

(Application to optical equipment)
FIG. 6 shows a configuration example in which the driving device S according to the present invention is applied to a driving system for an optical element in an optical apparatus such as an imaging device such as a digital camera or an optical pickup device. That is, in an optical apparatus having a mechanism in which at least one optical element is arranged on the optical axis, the optical element is held by the movable member 3 in the driving device S described above, and the optical element is advanced and retracted on the guide axis. An embodiment to be operated is shown.

  FIG. 6 illustrates a lens 12 held by a lens holder 11 as an optical element to be driven. This lens 12 is a lens (zoom lens) that constitutes a part of the photographing optical system when the applied optical device is an imaging device, and when the applied optical device is an optical pickup device, It is a lens that constitutes a part of the optical pickup optical system.

  The optical apparatus according to this embodiment includes a lens 12 held by the lens holder 11 described above, a piezoelectric actuator P that moves the lens 12 forward and backward, a magnetic field generating member 7 fixed to a side edge of the lens holder 11, The magnetic field detection means 6 includes a first magnetic field detection element 6 </ b> A and a second magnetic field detection element 6 </ b> B disposed to face the magnetic field generation member 7, and a counter shaft 10 that guides the lens holder 11. .

  One end of the lens holder 11 is attached (held) to the movable member 3 of the piezoelectric actuator P. The lens holder 11 is attached in such a positional relationship that the optical axis of the lens 12 is parallel to the advancing / retreating direction of the movable member 3 (that is, the extending direction of the driving member 2). On the other hand, a through hole is provided on the other end side of the lens holder 11, and the auxiliary shaft 10 is inserted through the through hole. Accordingly, the lens holder 11 is given a forward / backward movement force by the movable member 3 of the piezoelectric actuator P, and moves forward / backward while being guided by the auxiliary shaft 10 (up-down direction operation in FIG. 6). The piezoelectric element 1 of the piezoelectric actuator P is fixed to a mounting portion 90 provided on the main body of the optical device.

  The magnetic field generating member 7 is not directly attached to the movable member 3 but is fixed to the side edge of the lens holder 11 on the other end side (the side of the auxiliary shaft 10). The magnetic field detection means 6 is disposed so as to face the magnetic field generating member 7. As for the magnetic field detecting means 6 and the magnetic field generating member 7, the configuration shown in FIG. 3A described above is employed.

  According to the optical apparatus having such a configuration, the positioning of the optical element such as the photographing optical system or the optical pickup is required to have a high inclination accuracy with respect to the optical axis direction, and to have excellent straightness and high positioning accuracy. Since the optical element (lens 12) is driven using the piezoelectric actuator A, the drive member 2 itself has the function of a guide shaft, so that it has excellent straightness and is detected by the magnetic field detection means 6. By performing feedback control using the position information of the movable member 3, high positioning accuracy can be achieved.

  Further, since the position of the movable member 3 is detected based on the two output signals output from the first magnetic field detection element 6A and the second magnetic field detection element 6B, the operating environment temperature change of the optical device is substantially reduced. Position detection can be performed accurately without being affected. Further, the temperature calculation unit 803 calculates the temperature based on the output value of the first magnetic field detection element 6A and / or the second magnetic field detection element 6B, and the position correction signal generation unit 806 calculates the position based on the temperature information. Since the correction signal is generated and the control drive signal is corrected according to the operating environment temperature, even if the optical element (lens 12) that is the driven member has a temperature dependency in terms of size, There is an advantage that accurate movement control can be performed. That is, the temperature characteristic of the entire optical system in the optical apparatus can be compensated.

  In the embodiment shown in FIG. 3A, the example in which the magnetic field generating member 7 is attached to the auxiliary shaft 10 side is shown, but it may be provided at another position, for example, directly below the lens holder 11.

  Further, the arrangement of the magnetic field generating member 7 and the magnetic field detecting means 6 is switched, that is, the magnetic field detecting means 6 is arranged in the movable part of the movable member 3 or the lens holder 11, and the magnetic field generating member 7 is arranged in the fixed part. Also good. Even in this case, it is possible to perform substantially the same operation as described above.

  In the above configuration, the lens of the optical pickup optical system may be a driven member, and the lens may be moved in the optical axis direction by the advance / retreat operation of the movable member so that aberration correction is performed. That is, in order to correct image distortion caused by spherical aberration, chromatic aberration, etc. of the lens, the driving device according to the present invention may be used to drive the lens so that the influence of aberration can be suppressed to a minimum. .

(Example)
Using the drive device shown in FIG. 1 equipped with the position detection device shown in FIG. 3A, the change in output relative to the position of the magnetic field generating member 7 was calculated by experiment. The magnetic field generating member 7 of the magnetic field detection device has a length dimension L of 4.8 mm, a height dimension H of 1.5 mm, and a thickness dimension of 1.2 mm, and uses a distance A between the two magnetic field detection elements 6A and 6B. It was changed to 1.0, 1.2, 1.4, 1.6, and 1.8 mm. The distance between the magnetic field detection elements 6A and 6B and the magnetic field generating member 7 was fixed at 0.5 mm.
Moreover, the use stroke of the magnetic field generation member 7 was 2.4 mm.

  FIG. 7 shows output signals of the magnetic field detection elements 6A and 6B. Each output signal has a substantially sinusoidal shape, but at both ends, an approximate portion that extends to approximate the origin is generated. Further, the interval deviation A changes the period.

  FIG. 8 is a graph showing the change in output with respect to the position of the magnetic field generating member calculated from the output values of the magnetic field detection elements 6A and 6B and the slope of the graph of the output change. In the graph, the horizontal axis indicates the shift amount from the central origin, and the vertical axis indicates the ratio of output values. In FIG. 8, the solid line indicates the calculation result of the output change, and the broken line indicates the differential value of the calculation result, that is, the slope of the output change. 8A shows a case where the distance A is 1.0 mm, FIG. 8B shows a case where the distance A is 1.2 mm, and FIG. 8C shows a case where the distance A is 1.4 mm. (D) shows the case where the distance A is 1.6 mm, and FIG. 8 (e) shows the case where the distance A is 1.8 mm. In the graph of FIG. 8, the smaller the change in the slope of the graph, the higher the linearity, which is preferable. As shown in FIG. 1, when positioning the movable member 3 by feeding back the output of the detection circuit 8 to the control circuit 5, it is necessary to provide a gain margin, so the change in sensitivity of the position detection device is about 5 times. Is the limit. Therefore, it is considered preferable that the interval A having a relatively small change in inclination is 1.4 mm and 1.6 mm.

  FIG. 9 shows the result of obtaining linearity from the calculation result shown in FIG. The linearity index is calculated by the minimum value / maximum value of the slope value. As described above, since the length L of the magnetic field generating member 7 is 4.8 mm, the distance A is more linear at 1.4 mm and 1.6 mm than 1.2 mm, which is ¼ of the length of the magnetic field period. The results showed that the linearity was highest when the distance A was around 1.5 mm. That is, the optimum value of the measurement result is shifted by a difference of 0.3 mm with respect to 1.2 mm, which is ¼ of the magnetic field period, which is conventionally considered to be the optimum value. As described above, since the thickness dimension t of the magnetic field generating member is 1.2 mm, the shift amount of the optimum value corresponds to ¼ of the thickness dimension t of the magnetic field generating member 7. Further, the shift amount 0 (that is, the interval A = 1.2 mm) and the shift amount 0.6 mm (that is, the minute interval A = 1.8 mm), which is ½ of the thickness dimension t, are substantially the same value. As a result, the interval A is longer than ¼ of the length dimension L of the magnetic field generating member 7, and the linearity is improved by making the shift amount ½ of the thickness dimension t of the magnetic field generating member 7. The result was that it would be higher.

  A similar experiment was performed under the same conditions except that the thickness t of the magnetic field generating member 7 was 0.8 mm. The experimental results at this time are shown in FIG. It has been found that by reducing the thickness dimension of the magnetic field generating member 7 by 0.1 mm, the optimum linearity value is reduced by 0.1 mm. That is, the experimental result was (L + t) / 4 as the condition of the interval A at which the linearity was most improved. In addition, the interval A was in a range of L / 4 <A <L / 4 + t / 2, which resulted in further improved linearity.

  As a modification of the above embodiment, even when the magnetic field generating member is configured by providing a non-magnetized portion at the center as shown in FIG. Based on the length L and the thickness t, by setting the interval A in the range of L / 4 <A <L / 4 + t / 2, the linearity was improved. In FIG. 3B, the description of the first adder and the second adder is omitted.

  The magnetic field generating member 71 shown in FIG. 3B includes a rectangular first magnet 71A that is positively magnetized in the thickness direction (that is, the surface facing the magnetic field detection means 6 is N-pole and the back surface is S-pole), A rectangular second magnet 71B that is negatively magnetized in the vertical direction (that is, the surface facing the magnetic field detecting means 6 is the S pole and the back surface is the N pole), and the first and second magnets 71A, A configuration is adopted in which the first and second magnets 7A and 7B are opposed to each other and are fixed so as to sandwich the non-magnetized portion 72 between the sides of 71B. The dimensions of the magnetic field generating member 71 are, for example, a length dimension L in the advancing / retreating direction of 5.0 mm, a thickness dimension t of 0.8 mm, and a height dimension H of 1.4 mm. The length W of the non-magnetized portion 72 in the advancing / retreating direction is 1 mm, the distance A between the first magnetic field detecting element 6A and the second magnetic field detecting element 6B is, for example, 1.5 mm, and the magnetic field detecting elements 6A and 6B The distance between the first and second magnets 71A and 71B is 0.48 mm.

  Even when the non-magnetized portion 72 is provided between the first and second magnets 71A and 71B as described above, the distance A between the magnetic field detecting elements 6A and 6B is set to L / 4 <A <L / 4 + t / By setting it as the range of 2, the result that linearity improved was obtained.

1 is a system configuration diagram of a drive device equipped with a position detection device according to an embodiment of the present invention. It is explanatory drawing for demonstrating the operation | movement principle of a friction drive type piezoelectric actuator. It is explanatory drawing showing the drive shaft displacement of a friction drive type piezoelectric actuator. It is the block diagram which showed the position sensor part of the drive device concerning this invention in detail. It is the block diagram which showed in detail the modification of the position sensor part of the drive device concerning this invention. A schematic diagram (a) in the case where the magnetic field detecting element relatively moves along the direction of fluctuation of the magnetic field of the magnetic field generating member in which the positive magnetic attachment and the negative magnetic attachment are repeatedly performed, and a diagram showing an output signal value from the magnetic field detecting element (B). Schematic diagram (a) when the magnetic field detection element relatively moves along the direction of fluctuation of the magnetic field of the magnetic field generating member having one positive magnetic attachment and one negative magnetic attachment, and a diagram showing an output signal value from the magnetic field detection element (B). It is a block diagram which shows the structural example at the time of applying the drive device of FIG. 1 to the drive system of the optical element in an optical device. It is a graph which shows the output signal of magnetic field detection element 6A, 6B. It is a graph which shows the change of the output with respect to the position of the magnetic field generation member computed from the output value of the magnetic field detection element at the time of changing the space | interval of a magnetic field detection element, and the inclination of the graph of the output change. It is a graph which shows the relationship between the linearity based on the calculation result of FIG. It is a graph which shows the relationship between the linearity and the space | interval A when the thickness dimension of a magnetic field generation member shall be 0.8 mm. It is the schematic which shows the structure of the conventional position detection apparatus. It is the schematic which shows the structure of the other conventional position detection apparatus. It is the schematic which shows the structure of the other conventional position detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Drive member 3 Movable member 4 Drive circuit 5 Control circuit 6 Magnetic field detection means 6A 1st magnetic field detection element 6B 2nd magnetic field detection element 7 Magnetic field generation member 7A Rectangular first magnet 7B Rectangular second Magnet 8 Detection circuit 8A 1st adder 8B 2nd adder 8C Operation unit 10 Countershaft 11 Lens holder 12 Lens A Magnetic field detection element interval L Magnetic field generation member length dimension t Magnetic field generation member thickness dimension P Piezoelectric Actuator

Claims (9)

It is integrally attached to a movable member configured to be able to advance and retreat, and is configured so that only one north pole and one south pole are magnetized in the forward and backward direction of the movable member, and the surface magnetic flux density changes in the forward and backward direction of the movable member. A magnetic field generating member having a changed magnetic field;
Magnetic field detection means comprising two magnetic field detection elements that are arranged side by side in the advance and retreat direction of the movable member at intervals A, detecting a magnetic field change accompanying the movement of the magnetic field generating member based on the advance and retreat operation of the movable member;
Calculating means for obtaining a position of the movable member based on a detection signal of the magnetic field detecting means;
The magnetic field generating member has a length L in the forward / backward direction and a thickness t,
An interval A between two magnetic field detecting elements constituting the magnetic field detecting means is
L / 4 <A <L / 4 + t / 2
It is comprised so that it may become. The position detection apparatus characterized by the above-mentioned.   The magnetic field generating member includes a rectangular first magnet that is positively magnetized in the thickness direction, and a rectangular second magnet that is negatively magnetized in the thickness direction. The position detection device according to claim 1, wherein the position detection device has a substantially rectangular shape in which the sides of the two magnets are fixed to face each other.   The position detection device according to claim 1, wherein the magnetic field detection element is a Hall element. A position detection device according to any one of claims 1 to 3,
An electromechanical transducer having one end fixed to the frame to which the magnetic field detecting means is fixed and extending and contracting in the movable direction;
A guide shaft connected to the other end of the electromechanical conversion element and frictionally engaged with the movable member;
A drive device comprising: An optical apparatus comprising a mechanism in which at least one optical element is disposed on an optical axis,
5. The optical apparatus according to claim 4, wherein the movable device in the driving device is configured to function as a holding body that holds the optical element and moves the optical element forward and backward on its guide shaft.   6. The optical apparatus according to claim 5, wherein the optical element is held by the movable member so that the optical axis of the optical element is parallel to the advancing / retreating direction of the movable member.   6. The optical apparatus according to claim 5, wherein the optical apparatus is an image pickup apparatus, and the optical element is an optical element constituting a part of the photographing optical system.   8. The optical apparatus according to claim 7, wherein the optical apparatus is an optical pickup device, and the optical element is an optical element constituting a part of the optical pickup optical system.   9. The optical element according to claim 8, wherein the optical element is a lens of an optical pickup optical system, and the lens is moved in the optical axis direction by an advance / retreat operation of a movable member, so that aberration correction is performed. The optical instrument described.

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