JP2009168920A - Lens module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens module that is highly precise and excels in reliability by stabilizing an amount of movement of an optical lens of an impact drive system. <P>SOLUTION: The lens module has a piezoelectric ceramic element at the other end of a magnet, and uses the vibration of the piezoelectric ceramic element as a driving force. While a moving body 35 and one end of the magnet 21 are attracted, the lens module moves a driven body along the optical axis of an optical lens 10. In the driven body, the moving body 35 that is attracted to the magnet 21 is formed in part of a lens holder 41 that has the optical lens 10. The weight m (unit: g) of the driven body is 0.035 F or less relative to the dynamic frictional force F (unit: mN) of a sliding part between the magnet 21 and the moving body 35. Where the force with which the magnet attracts the moving body is P (unit: mN), and the maximum distance between the gravity center of the driven body and the sliding part when the moving body is located at the end of the driving range is L, the length of the magnet 21 in the sliding direction is set to 2LF/P or greater. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lens module including an optical lens that moves in a predetermined direction, and particularly relates to a lens module that is suitable for use in a digital video camera, a digital camera, or a mobile phone camera. The present invention relates to a lens module suitable for an optical apparatus having a mechanism.

  In order to provide the camera with an autofocus or zoom function, a mechanism for moving the optical lens minutely along the optical axis is required, and a method using an electromagnetic motor has been conventionally known. In recent years, as seen in digital cameras and camera-equipped mobile phones, the miniaturization of devices has progressed rapidly, and as a result, lens movement by electromechanical transducers typified by piezoelectric elements is used instead of electromagnetic motors. A method has been proposed.

  For example, Patent Document 1 discloses a driving apparatus including a driving mechanism that is configured by frictionally coupling a driven member to a driving member that is coupled to and displaced together with an electromechanical conversion element, and includes a driving member and a driven member. A means using a magnet is shown as means for applying a pressing force for frictional engagement.

JP 7-274546 A

  However, in the case of the conventional technique using the method of moving an optical lens by an electromechanical transducer as disclosed in Patent Document 1, there is a structural problem in order to realize a small and stable drive. For example, in the method disclosed in Patent Document 1, there are many places where the moving shaft for moving the optical lens is substantially frictionally engaged with other members, and therefore the frictional force of the frictional engagement portion is controlled. This makes it difficult to drive the optical lens stably.

  As a method for solving these problems and enabling a small and stable drive, for example, the structure of the lens module according to the invention of the present applicant as shown in FIG. 2 can be considered. 2A and 2B are schematic views showing the basic configuration of the lens module, FIG. 2A is an external plan view from the top surface direction, and FIG. 2B is a side cross-sectional view in the BB line direction of FIG. is there. A piezoelectric ceramic element 11 having one end fixed to the housing 51, a driving body including a magnet 21 fixed to the other end of the piezoelectric ceramic element 11, and a ring-shaped moving body 31 made of a material that can be attracted to the magnet 21. And a lens holder 41 that supports the moving body 31 as a unit, and an optical lens 10 that is supported or integrated with the lens holder 41, and vibrates the magnet 21 by vibration generated by the piezoelectric ceramic element 11. A lens driving mechanism having a function of moving the lens holder 41 along the optical axis direction by driving the moving body 31 using the vibration as a driving force is provided. The lens holder 41 is movably supported by the guide pin 61 to prevent tilting or rotation.

  The lens moving mechanism of this lens module is an impact drive system that applies a voltage that expands and contracts at different speeds during expansion and contraction to the piezoelectric ceramic element 11 and uses friction and slip due to the difference in expansion / contraction time. That is, the driving body is driven by a continuous pulse having a sawtooth waveform that slowly extends and then rapidly contracts. In the first half, the moving body 31 is displaced together with the magnet 21 by the frictional force, and in the second half, the inertial force exceeds the frictional force. By preventing slippage and displacement of the moving body 31, the lens holder 41 and the optical lens 10 engaged with the moving body 31 are moved in the optical axis direction. The magnet 21 of the driving body and the moving body 31 are in physical contact, but during the time when slippage occurs, tilting and rotational movement are likely to occur due to contact with the unevenness of the sliding surface and the guide portion. Become.

  Also in the technique disclosed in Patent Document 1, an impact driving method is employed for driving the optical lens. In the impact drive system, the relationship between the frictional force and the inertial force is important as described above. However, Patent Document 1 specifically describes the relationship between the frictional force of the frictional engagement portion and the weight of the moving member including the optical lens. No disclosure has been made.

  The lens module in FIG. 2 includes a lens driving mechanism that can stabilize the moving speed of the optical lens in the lens module as compared with the known prior art such as Patent Document 1, and the lens holder 41 is configured to prevent rotation. However, there is a possibility that the amount of movement varies due to tilt and rotation.

  As described above, the lens module as shown in FIG. 2 which is an invention of the present applicant and is an unpublished invention at present is required to be further improved. The present invention has been made to solve the above-described problems, and is to provide a lens module that can be reduced in size and has excellent reliability in which the amount of movement of an optical lens in repeated micro-driving is stabilized. .

  In order to solve the above problems, in the impact drive method, it is considered that the relationship between the frictional force and the inertial force is important. Therefore, by examining the structure of the lens module, the frictional force and the moving member including the optical lens The relationship with the weight has been clarified and the present invention has been achieved.

  The lens module of the present invention is supported by a driving body including an electromechanical conversion element fixed at one end to a stationary member, a magnet fixed at the other end of the electromechanical conversion element, a lens holder, and the lens holder. An optical lens and a driven body made of a moving body formed of a material that can be attracted to the magnet by a part of the lens holder, and the magnet is vibrated by vibration generated by the electromechanical transducer. A lens module having a function of moving the lens holder along the optical axis direction of the optical lens by slidingly driving the moving body using the vibration of the magnet as a driving force, the magnet being the moving body P (unit: mN) is a force for attracting the moving body, and F (unit: mN) is a dynamic friction force acting between the magnet and the magnet when moving the moving body along the optical axis direction. When the maximum distance of connecting the center of gravity of the driven member and the sliding portion when the movable body is positioned at the end of the driving range is L (unit: mm), the sliding direction of the magnet The length (unit: mm) is 2LF / P or more.

  Moreover, in this invention, when the dynamic frictional force in the sliding part of the said magnet and the said moving body is set to F (unit: mN), the weight m (unit: g) of the said driven member is 0.035F or less. Is desirable. With respect to the definition of the weight m of the driven member, if the weight m of the driven member is out of the above range, the relationship between the frictional force and the inertial force becomes inappropriate for impact driving, and the lens is moved at a desired speed. This is because it is considered impossible to do so.

  Furthermore, in the present invention, it is desirable that at least one of the surface of the magnet or the surface of the portion of the moving body that adsorbs and slides is coated with a lubricant or a thin film that enhances lubricity.

  As described above, in the present invention, the magnet bonded to the electromechanical transducer and the moving body made of a material that can be attracted to the magnet are attracted and engaged by the magnetic force generated by the magnet, and the magnet is The force for attracting the moving body is P (unit: mN), and the dynamic friction force acting between the magnet and the magnet when moving the moving body along the optical axis direction is F (unit: mN). When the maximum distance between the center of gravity of the driven member and the sliding portion when L is located at the end of the driving range is L (unit: mm), the length of the magnet in the sliding direction ( By setting the unit (mm) to 2 LF / P or more, a stable lens movement amount can be obtained.

  In addition, when the dynamic frictional force at the sliding portion between the magnet and the moving body is F (unit: mN), the driven member has a weight m (unit: g) of 0.035 F or less, thereby enabling impact driving. In this case, the relationship between the frictional force and the inertial force becomes appropriate, and it is possible to move the optical lens at a speed of 1 mm / sec or more, which is desirable for autofocus and zoom functions.

  In addition, at least one of the surface of the magnet or the sliding portion of the moving body is coated with a lubricant or a thin film that enhances lubricity, for example, a DLC (diamond-like carbon) film, thereby reducing frictional resistance and optical lenses. Can be stably obtained with a large amount of movement.

  As described above, according to the present invention, it is possible to obtain a lens module that can be miniaturized and that has high accuracy and high function reliability that stabilizes the amount of movement of the optical lens in repeated micro-driving.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing a basic configuration of a first embodiment of a lens module according to the present invention, FIG. 1 (a) is an external plan view from the top surface direction, and FIG. 1 (b) is FIG. 1 (a). It is side surface sectional drawing in the AA line direction. Also in FIG. 1, similarly to the lens module of FIG. 2, a piezoelectric ceramic element 11 that is an electromechanical conversion element whose one end is fixed to a housing 51 that is a stationary member and a magnet 21 that is fixed to the other end of the piezoelectric ceramic element 11. And the lens holder 41 and the optical lens 10 supported by the lens holder 41, and a moving body 35 made of a material that can be adsorbed to the magnet 21 on a part of the lens holder 41. Is formed.

  However, in the present embodiment, the length of the magnet 21 in the sliding direction is set as follows. That is, the force by which the magnet 21 attracts the moving body 35 is P (unit: mN), and the dynamic friction force acting between the moving body 35 and the magnet 21 when the moving body 35 is moved along the optical axis direction. F (unit: mN). In the state where the moving body is within the driving range, the center of gravity of the driven member including the lens holder 41 including the moving body 35 and the optical lens 10 and the maximum of the connecting portion between the magnet 21 and the sliding portion of the moving body 35 are connected. Let the distance be L (unit: mm). From these values, the length (unit: mm) of the magnet 21 is set to 2 LF / P or more.

  As such a structure, a voltage is applied to the piezoelectric ceramic element 11 so as to expand and contract at different speeds during expansion and contraction, and the magnet 21 is vibrated in parallel with the optical axis of the optical lens 10, thereby moving the moving body 35. By moving in the expansion / contraction direction, the lens holder 41 is moved in the optical axis direction. In this case, in the present application, the length of the magnet 21 in the sliding direction is set to a length of 2LF / P or more, so that variation in the movement amount can be reduced. Therefore, a highly accurate lens module can be configured.

  The weight m (unit: g) of the driven member including the lens holder 41 including the moving body 35 and the optical lens 10 supported by the lens holder 41 is preferably as low as 0.035 F or less. Can be moved at high speed.

  In addition, a thin film portion 36 with good lubricity is formed on the sliding portion of the moving body 35 in order to enhance the sliding function. The thin film portion 36 is preferably an electroless Ni plating or DLC (diamond-like carbon) film containing tetrafluoroethylene powder. Further, a similar effect can be obtained by forming a thin film portion on the sliding portion of the magnet 21 instead of the moving body 35. Of course, a thin film having a small coefficient of friction may be formed on both the surface of the movable body 35 and the sliding portion of the magnet 21. It is also effective to use a lubricant for the sliding portion of the magnet 21 and the moving body 35 in place of or in place of providing a thin film portion with good lubricity for enhancing the sliding function.

  In the first embodiment shown in FIG. 1, the surface shape of the sliding portion of the moving body 35 is a curve (cylindrical surface), and sliding with the magnet 21 is performed by line contact. The surface shape of the sliding portion of the body 35 may be flat, and the contact state with the sliding portion of the magnet 21 may be surface contact.

  FIG. 3 is a schematic view showing a basic configuration of a second embodiment of the lens module according to the present invention, FIG. 3 (a) is an external plan view from the top surface direction, and FIG. 3 (b) is a front view (front of the housing). The wall of the part is omitted). The lens module according to the second embodiment of the present invention includes a piezoelectric ceramic element 11 that is an electromechanical conversion element that is fixed to a housing 51 that is a stationary member, and a magnet 21 that is fixed to the other end of the piezoelectric ceramic element 11. And a lens holder 41, and an optical lens 10 supported or integrated with the lens holder 41, and a movement made of a material that can be attracted to the magnet 21 by a part of the lens holder 41. A body 31 'is formed.

  However, also in the second embodiment, the length (unit: mm) in the sliding direction of the magnet 21 is set to 2 LF / P or more. L, F, and P are the same as those in the first embodiment. That is, the force with which the magnet 21 attracts the moving body 31 ′ is P (unit: mN), and when the moving body 31 ′ is moved along the optical axis direction, it acts between the moving body 31 ′ and the magnet 21. The dynamic friction force is F (unit: mN). Further, while the moving body is within the driving range, the center of gravity of the driven member composed of the lens holder 41 including the moving body 31 ′ and the optical lens 10 and the sliding portion of the magnet 21 and the moving body 31 ′ are connected. Is the maximum distance L (unit: mm).

  Also in the lens module according to the second embodiment, the magnet 21 is vibrated by the vibration generated in the piezoelectric ceramic element 11, and the moving body 31 'is slidably driven by using the vibration of the magnet 21 as a driving force. Can be moved along the optical axis direction of the optical lens 10, and variation in the amount of movement can be reduced. Therefore, a highly accurate lens module can be configured.

  The weight m (unit: g) of the driven member including the lens holder 41 including the moving body 31 ′ and the optical lens 10 supported by the lens holder 41 is preferably as low as 0.035 F or less. It can be moved at high speed.

  Further, it is desirable to provide a thin film portion 36 ′ having good lubricity on the surfaces of the sliding portions of the moving body 31 ′ and the magnet 21 and to use a lubricant.

  In the second embodiment, the magnet 21 has a substantially cylindrical shape as shown in FIG. The moving body 31 ′ is attracted to the magnet 21. At this time, the moving body 31 ′ is in line contact at two locations on the circumference of the magnet 21 and can move in the height direction on the circumference of the magnet 21. In the second embodiment, the shape of the magnet 21 is a cylindrical shape so as to make a line contact with the moving body 31 ′ as shown in FIG. It doesn't have to be. Furthermore, since there is no problem if the friction during sliding does not become excessive so as to hinder movement, the contact state between the magnet 21 and the moving body 31 ′ may be surface contact in addition to line contact.

  As described above, in the first embodiment as shown in FIG. 1, the surface shape of the sliding portion of the moving body 35 is a convex surface, but as in the second embodiment shown in FIG. The shape of the magnet 21 and the moving body 35 may be different, for example, the magnet 21 has a cylindrical shape, the moving body 31 ′ has an L shape, and the surface shape of the sliding portion of the moving body 31 ′ is concave. By adopting the configuration of the present application, it is possible to reduce variation in the amount of movement and provide a highly accurate lens module.

Example 1
Next, examples of the lens module according to the first embodiment shown in FIG. 1 will be described. A piezoelectric multilayer ceramic element having a cross section of 1.0 mm × 1.0 mm and a height of 2.0 mm was prepared as the piezoelectric ceramic element 11. This piezoelectric multilayer ceramic element generates a displacement of approximately 0.1 μm when a voltage of ± 3 V is applied. A drive body was constructed by adhering a neodymium magnet having a different length in the sliding direction of the magnet to one end of the piezoelectric ceramic element as a magnet 21 with a thermosetting epoxy resin. The neodymium magnet 21 has a size of 1.2 mm × 1.5 mm and a height of 1.0 to 1.4 mm. Further, a housing 51 made of polycarbonate was produced, and the driving body was bonded to the position shown in FIG. 1 with an epoxy resin.

  On the other hand, the moving body 35 was made of stainless steel SUS430 with an outer diameter of 8.5 mm, an inner diameter of 7.5 mm, and a height of 2.0 mm, and adhered to the lens holder 41 made of polycarbonate with an epoxy resin. The surface of the sliding part of the stainless steel SUS430 moving body is coated with a DLC thin film with a thickness of about 2 μm.

  When a predetermined number of AC pulses are applied to the piezoelectric ceramic element 11 of this lens module at predetermined time intervals, and the lens holder 41 is moved stepwise by a certain amount in the optical axis direction, the stability of the lens movement amount Evaluated. The applied AC pulse has a sawtooth waveform with a voltage of ± 3 V, and the number of times of input at a predetermined time interval is 20 times. Further, in the stepwise movement of the lens holder 41, the movement amount per time was set to 12 μm.

  In the dimension range of the magnet of this configuration, the ratio (F / P) of the force P that the magnet 21 attracts the moving bodies 35 and 31 and the dynamic friction force F that works when the magnet 21 and the moving bodies 35 and 31 slide. ) Is 0.15, and the maximum distance L between the center of gravity of the driven body and the sliding portion when the moving body is located at the end of the driving range is 4.37 mm. 2LF / P = 1.31. Therefore, the case where the height of the magnet 21 is 1.31 mm or more is an example, and the case where the height of the magnet 21 is less than 1.31 mm is a comparative example outside the scope of the present invention.

  Table 1 summarizes the results of the stability evaluation test for the two produced lens modules, and shows the standard deviation of the lens movement amount under the above driving conditions. Lateral means that the lens module is arranged so that the lens drive (optical axis) direction is perpendicular to the direction of gravity. Upward means that the lens drive from infinity to the macro side is against gravity. When the module is arranged (the direction of FIG. 1B), the downward direction is the case where the lens module is arranged so that the lens driving direction when moving the focal point from infinity to the macro side is the same as the gravity direction (FIG. 1). (B) is an inverted direction).

  From Table 1, in the example out of the scope of the invention, the standard deviation of the lens movement amount was 2 μm or more in all module arrangements, but in the embodiment of the present invention, the result was dramatically improved to 1.5 μm or less. It was. In other words, when the length of the magnet is short, the lens is considered to have a structure that is easy to rotate, and the optical lens can be moved stably by increasing the length of the magnet in the sliding direction to 2 LF / P or more. It can be said that it was possible.

(Example 2)
Next, an example of thin film coating will be described in the lens module of the second embodiment shown in FIG. A piezoelectric multilayer ceramic element having a cross section of 1.0 mm × 1.0 mm and a height of 2.0 mm was prepared as the piezoelectric ceramic element 11. This piezoelectric multilayer ceramic element generates a displacement of approximately 0.1 μm when a voltage of ± 3 V is applied. A driving body was constructed by adhering a neodymium magnet having a diameter of 1.5 mm and a height of 1.6 mm as a magnet 21 to one end of the piezoelectric ceramic element with a thermosetting epoxy resin. Further, a housing 51 made of polycarbonate was produced, and the driving body was bonded to the position shown in FIG. 3 with an epoxy resin.

  On the other hand, the moving body 31 ′ is made of stainless steel SUS430 and has a V-shaped cross section with a side of 3.5 mm and an angle formed by two sides of 90 °, a thickness of 0.2 mm, and a height of 2.0 mm. The lens holder 41 made of polycarbonate was bonded with an epoxy resin. In addition, the surface of the sliding part of the moving body made of stainless steel SUS430 is coated with a DLC thin film with a thickness of about 4 μm. In addition, for comparison with the case where a thin film for improving lubricity is not formed on the sliding portion, a moving body 31 ′ not coated with the DLC thin film was also produced and used as a comparative example.

  For these lens modules, an AC pulse is applied to the piezoelectric ceramic element 11, the lens holder 41 is moved from infinity to the macro side, and then a reverse AC pulse is applied to move from the macro side to the infinity side. Drive, i.e., reciprocal drive in a predetermined stroke. The stroke was 350 μm.

  Table 2 shows the results of reciprocal driving for the lens module having the DLC thin film formed on the surface of the sliding portion of the moving body 31 ′ and the lens module not having the DLC thin film.

  From Table 2, the example in which the DLC thin film was formed was able to be driven stably more than 1000 times, whereas in the comparative example in which the DLC thin film was not formed, the amount of movement of the optical lens decreased after about 600 times of driving. It was. That is, in the comparative example, the transition to the wear period started in the early stage of sliding, but in the example, it can be said that the optical lens could be stably moved by the thin film that enhances the lubricity.

(Example 3)
An example of the lens module of the second embodiment shown in FIG. 3 will be described. As in Example 2, a piezoelectric multilayer ceramic element having a cross section of 1.0 mm × 1.0 mm and a height of 2.0 mm was prepared as the piezoelectric ceramic element 11. This piezoelectric multilayer ceramic element generates a displacement of approximately 0.1 μm when a voltage of ± 3 V is applied. Three types of neodymium magnets with a diameter of 1.5 mm and heights of 1.2, 1.4, and 1.6 mm are bonded to one end of the piezoelectric ceramic element as a magnet 21 with a thermosetting epoxy resin, and three types of driving are performed. Constructed the body. Further, a housing 51 made of polycarbonate was produced, and the driving body was bonded to the position shown in FIG. 3 with an epoxy resin. Note that the frictional force in sliding between the magnet and the moving body is adjusted by changing the height of the magnet 21.

  On the other hand, the moving body 31 ′ is made of stainless steel SUS430 and has a V-shaped cross section with a side of 3.5 mm and an angle formed by two sides of 90 °, a thickness of 0.2 mm, and a height of 2.0 mm. The lens holder 41 made of polycarbonate was bonded with an epoxy resin. In addition, the surface of the sliding part of the moving body made of stainless steel SUS430 is coated with a DLC thin film with a thickness of about 4 μm.

  For these lens modules, a predetermined number of AC pulses are applied to the piezoelectric ceramic element 11 at predetermined time intervals, and the lens holder 41 is moved stepwise in the optical axis direction. The moving speed was calculated. The applied AC pulse has a sawtooth waveform with a voltage of ± 3V.

  FIG. 4 shows the result of evaluating the load characteristics of a module in which the height of the magnet 21 is changed and the frictional force in the sliding portion between the magnet and the moving body is adjusted. The dynamic friction force F at the sliding portion between each magnet and the moving body is 50, 70, 90 mN, and the load characteristics were evaluated from the speed change when a member having a predetermined weight was added to the lens holder 41. For the load, the total weight m of the load with respect to the dynamic friction force (this is the load factor) is used as a reference unit. The total weight is the weight m of the driven member composed of the lens holder 41, the optical lens 10, and the moving body 31 ′ and the predetermined weight member, and the load factor S is S = m / F ( (Unit: g / mN).

  FIG. 4 shows that the speed decreases as the load factor S increases regardless of the dynamic friction force F at the sliding portion of the magnet and the moving body. As described above, the moving speed of the optical lens is preferably 1 mm / sec or more for the autofocus and zoom functions. From these results, when the load factor S is 0.035 or less, it can be moved at a speed of 1 mm / sec or more. Therefore, the lens holder 41, the optical lens 10 supported by the lens holder, and the moving body 31 ′ are included. It can be seen that the total weight m of the driven members is preferably set to 0.035 F (unit: g) or less.

  It can also be seen that when the load factor S is the same, the smaller the dynamic friction force F, the higher the moving speed can be obtained. This result also suggests that the thin film that improves lubricity has the effect of obtaining a large amount of lens movement.

  As described above, according to the present invention, since the rotational motion of the driven member can be suppressed by setting the length of the magnet in the sliding direction to 2 LT / P or more, there is a variation in the amount of movement of the lens. And stable driving becomes possible. Further, by coating the surface of the sliding portion of the moving body with a thin film that enhances the lubricity, the friction coefficient of the sliding contact surface can be reduced, and a large amount of movement can be obtained stably. Furthermore, by setting the weight m of the driven member consisting of the optical lens, lens holder, and moving body to 0.035 F or less, it is possible to move the optical lens at a speed of 1 mm / sec or more using friction and slip. become.

  As described above, according to the present invention, it is possible to obtain a small lens module with improved stability in lens driving, high functionality and excellent reliability.

  Needless to say, the present invention is not limited to the above-described embodiments and examples, and the dynamic frictional force on the sliding surface between the magnet and the moving body is changed according to the weight of the driven member. Can do. Further, the material and thickness of the thin film to be coated, the shape and dimensions of the sliding surface can be changed so as to obtain the required dynamic friction force in accordance with the shape and mass of other portions. Furthermore, according to the use of the lens module, the structure, shape and material of the piezoelectric element and magnet, the moving body and lens holder, the material and shape of the housing, etc. can be selected and designed.

1 is a schematic diagram showing a basic configuration of a lens module according to a first embodiment of the present invention, FIG. 1 (a) is an external plan view from the top surface direction, and FIG. 1 (b) is an AA line in FIG. 1 (a). Side surface sectional drawing in a direction. FIG. 2A is a schematic diagram illustrating a basic configuration of a lens module, FIG. 2A is an external plan view from the top surface direction, and FIG. 2B is a side cross-sectional view in the direction of the line BB in FIG. FIG. 3A is a schematic diagram showing a basic configuration of a second embodiment of the lens module according to the present invention, FIG. 3A is an external plan view from the top surface direction, and FIG. 3B is a front view (the wall of the front portion of the housing is shown). (Omitted). The load characteristics of the lens module of the present invention (FIG. 3) are shown, the vertical axis is the lens moving speed, and the horizontal axis is the load factor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical lens 11 Piezoelectric ceramic element 21 Magnet 31, 35, 31 'Moving body 36, 36' Thin film part 41 Lens holder 51 Housing 61 Guide pin

Claims (3)

  An electromechanical transducer having one end fixed to a stationary member; a driving body comprising a magnet fixed to the other end of the electromechanical transducer; a lens holder; an optical lens supported by the lens holder; and And a driven body made of a moving body partially formed of a material that can be attracted to the magnet, and the magnet is vibrated by vibration generated by the electromechanical transducer, thereby driving the vibration of the magnet. A lens module having a function of moving the lens holder along the optical axis direction of the optical lens by slidingly driving the moving body as a force, wherein P is a force by which the magnet attracts the moving body The driven member when the moving body is located at the end of the driving range, where F is a dynamic friction force acting between the moving body and the magnet when moving the moving body along the optical axis direction Lens module, characterized in that when the maximum distance of connecting the centroid and the sliding portion is L, the sliding direction of the length of the magnet is 2LF / P or more.   2. The lens according to claim 1, wherein a weight of the driven member is 0.035 F (g) or less, where F (mN) is a dynamic friction force in a sliding portion of the magnet and the moving body. module.   3. A lubricant or a thin film that enhances lubricity is coated on at least one of the surface of the magnet or the surface of the moving body that is attracted to and slides on the magnet. The lens module described in 1.

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