JP2008203583A - Lens module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens module that has a lens driving mechanism having simple structure capable of stabilizing the moving speed of an optical lens, and also that can be made low-profile. <P>SOLUTION: The lens module comprises: a driving body comprising a piezoelectric element 3 having one end fixed on the bottom surface of a housing 7, and a magnet 4 fixed to the other end of the piezoelectric element 3; a lens holder 6 having a cylindrical part; and the optical lens 2 supported by the lens holder 6. The cylindrical part of the lens holder 6 partly is formed with a moving part 5 composed of material attractable to the magnet 4. The magnet 4 is magnetized in the radius direction of the optical lens 2. The lens holder 6 is movably supported by a guide pin 8 so as to be prevented from tilting or rotating, and the outside diameter 12 of a part of the lens holder 6 where the moving part 5 is formed is smaller than outside diameter 11 of the other parts. The lens module has a function to oscillate the magnet 4 with the oscillation generated in the piezoelectric element 3, to drive the moving part 5 by using the oscillation of the magnet 4 as the driving force to thereby move the lens holder 6 along the optical axis direction of the optical lens 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a lens module that can be applied mainly to optical devices such as digital video cameras, digital cameras, and mobile phone cameras. Specifically, the present invention is preferably applied to optical devices having an autofocus and zoom mechanism. In addition, the present invention relates to a lens module including an optical lens that moves in a predetermined direction.

  In order to provide the camera with an autofocus or zoom function, a mechanism for moving the optical lens along the optical axis is required, and a method using an electromagnetic motor is generally known. However, in recent optical devices typified by digital cameras and camera-equipped mobile phones, miniaturization has rapidly progressed, and a technique using an optical lens moving method using an electrical / mechanical conversion element such as a piezoelectric element has been proposed. , Is becoming mainstream.

  As such a well-known technique, for example, in Patent Document 1, a driving member that is frictionally engaged with a driven object or a member connected to the driven object and is movably supported by a stationary member, and the drive Piezoelectric element that is fixed to a member and fixed to a stationary member so that the other end does not move, and piezoelectric element drive that applies a voltage to the piezoelectric element so that the speed of expansion differs from the speed of contraction And a driving device having the means.

  Further, Patent Document 2 includes a driving member using a magnetic material, and a movable lens group frame that has an exciting member that excites the driving member and is driven by the driving member, and the driving member has electric / mechanical energy. A driving mechanism driven by a conversion element is shown, and Patent Document 3 discloses a driving apparatus including a driving mechanism that is coupled to an electric / mechanical conversion element and frictionally couples a driven member to a driving member that is displaced together with the electromechanical conversion element. In this case, a magnet is used as means for applying a pressing force for frictionally engaging the driving member and the driven member.

Japanese Patent No. 2633066 Japanese Patent Laid-Open No. 10-10401 JP 7-274546 A

  In any of the known techniques using the above-described method of moving an optical lens by an electro / mechanical conversion element, there is a structural problem in order to realize a small and stable drive.

  For example, in the case of the method disclosed in Patent Document 1, a structure for supporting the driving member so as to be movable with respect to the stationary member is required, and the driving member and the driven object are connected using an elastic member such as a leaf spring. Since it is necessary to make frictional engagement, the structure of the lens module becomes complicated and it is difficult to reduce the size. Further, since it is difficult to control the frictional force, there is a problem that the moving speed of the driven object varies.

  In the case of the method disclosed in Patent Document 2, the magnetization direction of the excitation member is not fixed. For example, if the magnetization direction of the excitation member coincides with the movement direction of the optical lens, depending on the position of the optical lens, In the magnetic circuit formed with the drive member made of a magnetic material, the magnetic flux distribution becomes asymmetric in the vertical direction, which causes a problem that a significant difference is caused in the moving speed between when the lens is extended and when the lens is retracted. In addition, it is difficult to reduce the height of the drive member and the excitation member because of the structure.

  In the case of the method disclosed in Patent Document 3, 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. Due to the complexity, there is a problem that it is difficult to stably drive the optical lens.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a lens driving mechanism having a simple structure capable of stabilizing the moving speed of the optical lens and capable of reducing the height. To provide a module.

  In order to solve the above-described problems, a lens module according to the present invention includes a driving body including an electric / mechanical conversion element having one end fixed to a stationary member, and a magnet fixed to the other end of the electric / mechanical conversion element, and a cylinder. A lens holder having a shape portion and an optical lens supported by the lens holder are formed, and a moving portion made of a material that can be attracted to the magnet is formed in a part of the cylindrical shape portion of the lens holder. The magnetization direction of the magnet is a radial direction or an outer peripheral direction of the optical lens, and further, the magnet is vibrated by vibration generated by the electro / mechanical conversion element, and the vibration of the magnet is used as a driving force to move the moving unit. The lens holder is moved along the optical axis direction of the optical lens, and the moving portion is formed in the cylindrical portion of the lens holder. The outer diameter of the portion being smaller than the outer diameter of the other portions.

  In addition, the inner diameter of the portion of the lens holder where the moving part is formed may be smaller than the other portions, and optical lenses having different outer diameters may be supported on the smaller inner diameter portion and the other portions, respectively.

  Further, the moving unit may be driven by applying a voltage to the electro / mechanical conversion element to vibrate the magnet so that the extension speed and the contraction speed of the electro / mechanical conversion element are different. Good.

  The electric / mechanical conversion element may be a multilayer piezoelectric ceramic element.

  In the case of the lens module according to the present invention, a lens holder having a cylindrical body and a driving body comprising an electric / mechanical conversion element fixed at one end to a stationary member and a magnet fixed at the other end of the electric / mechanical conversion element. And an optical lens supported by the lens holder, and a moving part made of a material that can be attracted to the magnet is formed in a part of the cylindrical portion of the lens holder, and the magnetism of the magnet The direction is the radial direction or the outer peripheral direction of the optical lens, and further, the lens is vibrated by the vibration generated by the electro / mechanical conversion element, and the moving unit is driven using the vibration of the magnet as a driving force. Since the holder has a function of moving along the optical axis direction, the driving force generated from the vibration of the electrical / mechanical conversion element can be stably transmitted to the moving member. It can be reduced as compared with the case of the known technique variations in the moving speed of the academic lens.

  The lens module according to the present invention does not require a conventional elastic member such as a leaf spring and has a small number of frictional engagement portions, and therefore has a very simple and stable structure with a small number of parts. Further, since there is no drive shaft (rod) as in Patent Documents 2 and 3, vibrations are not attenuated by the drive shaft, and stable movement without causing a drive energy loss is possible, and the optical lens is moved along the optical axis direction. It can be moved stably. Further, the height can be easily reduced as compared with the conventional structure in which the drive shaft is provided on the electromechanical conversion element.

  Further, by reducing the outer diameter of the portion where the moving portion is formed in the cylindrical portion of the lens holder to be smaller than the outer diameter of the other portions, the volume of the magnet is increased by that amount to increase the attractive force. As a result, it becomes easy to increase the sliding force and further stabilize the moving speed. Further, when the volume of the magnet is constant, the height of the magnet can be reduced, so that the lens module can be further reduced in height.

  As described above, according to the present invention, it is possible to obtain a lens module that has a lens driving mechanism with a simple structure that can stabilize the moving speed of the optical lens and that can be reduced in height.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a basic configuration of a lens module according to a first embodiment of a lens module according to the present invention. FIG. 1 (a) is an external plan view from the upper surface direction, and FIG. It is side surface sectional drawing in the AA line direction of 1 (a).

  In FIG. 1, the lens module of the present embodiment includes a piezoelectric element 3 made of a laminated piezoelectric ceramic as an electro / mechanical conversion element fixed at one end to the bottom surface of a housing 7 that is a stationary member, and the other end of the piezoelectric element 3. A driving body including a fixed magnet 4, a lens holder 6 having a cylindrical portion, and an optical lens 2 supported by the lens holder 6. A magnet is formed on a part of the cylindrical portion of the lens holder 6. 4 is formed, and the magnet 4 is magnetized in the radial direction of the optical lens 2. Further, a guide pin 8 is installed in the housing 7, and a guide portion 9 having a hole for engaging with the guide pin 8 is integrally provided in a part of the lens holder 6, and the lens holder 6 is prevented from being tilted or rotated. The guide pin 8 is movably supported. In addition, the value of the outer diameter 12 of the portion where the moving portion 5 is formed in the cylindrical portion of the lens holder 6 is D2, which is smaller than the value D1 of the outer diameter 11 of the other portion.

  In the present embodiment, the magnet 4 is vibrated by the vibration generated by the piezoelectric element 3, and the lens holder 6 is moved along the optical axis direction of the optical lens 2 by driving the moving unit 5 using the vibration of the magnet 4 as a driving force. It has a function to move.

  Next, an example of a driving body composed of the piezoelectric element 3 and the magnet 4 will be described. The driving body is formed by adhering a magnet 4 to one end face side of the displacement generation direction (longitudinal direction) of the piezoelectric element 3 made of a laminated piezoelectric ceramic using an epoxy resin or the like. The polarity of the magnet 4 is magnetized in the radial direction of the lens 2 in FIG. 1B, and the inside of the radius is the S pole and the outside is the N pole. The magnet 4 can be magnetized in the circumferential direction of the lens 2.

  The material and structure of the piezoelectric element 3 can be appropriately selected as long as a predetermined displacement can be generated. Here, the lens module is assumed to be used for a camera module of a mobile phone or a digital still camera, and its driving voltage is several. In consideration of the necessity of being driven at a low voltage with a range of about V to several tens of volts, a laminated piezoelectric ceramic is used.

  As a method for manufacturing the piezoelectric element 3, a general method may be employed. For example, a ceramic green sheet having a predetermined thickness is produced by a doctor blade method or the like, and Ag is formed into a predetermined shape by a screen printing method or the like. / Pd paste or Cu paste is printed as an internal electrode, then trimmed and laminated a predetermined number of times, then hot pressed, punched into a predetermined shape, debindered and sintered, then laminated What is necessary is just to manufacture as a piezoelectric ceramic.

  The material of the magnet 4 is not particularly limited, but a neodymium-based magnet or a samarium-cobalt-based magnet may be used in order to ensure a sufficient attractive force even when the size is reduced. As for the magnetization direction of the magnet 4, the N pole and the S pole are arranged in a direction orthogonal to the optical axis direction of the optical lens as described above. Thereby, since the magnetic flux distribution in the magnetic circuit formed by the magnet 4 and the moving part can be formed symmetrically with respect to the moving direction of the optical lens, the moving direction of the optical lens and the opposite direction thereof There is no difference in driving force, and the optical lens can be driven stably.

  Here, in the driving body of the present invention, in order to further stabilize the moving speed of the lens holder 6, it is necessary to increase the sliding force transmitted from the magnet 4 to the moving unit 5. Is proportional to the attractive force of the magnet 4, and the attractive force of the magnet 4 depends on the volume of the magnet 4. Therefore, in the present invention, the length of the magnet 4 can be increased by reducing the outer diameter of the lens holder 6 in the portion where the moving body is formed, and the volume of the magnet 4 is increased.

  Further, even when the height of the magnet 4 is reduced to reduce the height of the lens module, the required volume can be secured by increasing the length.

  In the present embodiment, the moving unit 5 and the lens holder 6 are separate members. However, the same member may be integrally formed of the same material.

  Incidentally, in the lens module according to FIG. 1, vibration generated from the piezoelectric element 3 is also transmitted to the housing 7, so that when applied as a camera module, there is a possibility of adverse effects such as vibration noise on an image sensor (not shown). This vibration noise can be considered by inserting a vibration damping material made of a material such as rubber into the portion of the housing 7 to which the piezoelectric element 3 is fixed, and further transmitting the vibration energy of the piezoelectric element 3 to the portion of the magnet 4. Therefore, it can be removed by adopting a configuration in which a weight member is inserted between the vibration damping material and the piezoelectric element 3.

  Here, one specific example of the lens module of the present embodiment will be described. The piezoelectric ceramic element 3 is a piezoelectric laminated ceramic having a cross-sectional dimension of 1.0 mm long × 1.0 mm wide and 2.0 mm high, and generates a displacement of approximately 0.1 μm with respect to an applied voltage of ± 3 V. Can be used. A neodymium magnet having a cross-sectional dimension of 1.2 mm x 2.0 mm and a height of 1.0 mm is bonded to one end face side of the piezoelectric ceramic element 3 with a thermosetting epoxy resin to form a driving body. After the housing 7 made of polycarbonate having the shape shown in FIGS. 1A and 1B is formed, the other end face side of the piezoelectric element 3 is placed at the position shown in FIG. Adhere with and configure.

  Next, a moving part 5 having an outer diameter of 7.5 mm, an inner diameter of 6.5 mm, and a height of 1.5 mm made of a material of SUS430 is manufactured, and this moving part 5 is adhered to a lens holder part made of polycarbonate with an epoxy resin. The holder 6 is completed. The outer diameter D2 of the portion of the lens holder 6 where the moving portion 5 is formed is 7.5 mm, the outer diameter D1 of the other portions is 8.5 mm, and the inner diameter D3 is 5.0 mm. In addition, the lens module 6 is supported by a guide pin 8 made of SUS304, and the magnet 4 and the moving part 5 are attracted by a magnetic force, whereby the lens module having the structure shown in FIGS. 1 (a) and 1 (b). Can be obtained.

  In the case of the lens module shown in the above specific example, the moving stroke of the lens holder 6 is about 0.5 mm, but the stroke can be further increased by increasing the height of the moving portion 5. .

  2A and 2B show a basic configuration of a lens module according to a second embodiment of the lens module according to the present invention. FIG. 2A is an external plan view from the upper surface direction, and FIG. It is side surface sectional drawing in the AA line direction of 2 (a).

  In FIG. 2, the lens module of the present embodiment has a piezoelectric element 23 made of a laminated piezoelectric ceramic as an electro / mechanical conversion element fixed at one end to the bottom surface of a housing 27 that is a stationary member, and the other end of the piezoelectric element 23. A drive body including a fixed magnet 24, a lens holder 26 having a cylindrical portion, and optical lenses 32 and 33 supported by the lens holder 26, and a part of the cylindrical portion of the lens holder 26. The moving part 25 made of a material that can be attracted to the magnet 24 is formed on the magnet 24, and the magnet 24 is magnetized in the radial direction of the optical lens 32. In addition, a guide pin 28 is provided in the housing 27, and a guide portion 29 having a hole that engages with the guide pin 28 is integrally provided in a part of the lens holder 26. The lens holder 26 is prevented from tilting or rotating. The guide pin 8 is movably supported. The outer diameter 42 of the cylindrical portion of the lens holder 26 where the moving portion 25 is formed is D5, which is smaller than the value D4 of the outer diameter 41 of the other part.

  In this embodiment, the inner diameter 43 of the portion of the lens holder 26 where the moving portion 25 is formed is D6, which is smaller than the value D7 of the inner diameter 44 of the other portion, and the outer diameter is smaller in the portion of the inner diameter 43. A lens 32 having a large outer diameter is supported on the inner diameter 44 portion.

  Also in this embodiment, the magnet 24 is vibrated by the vibration generated in the piezoelectric element 23 as in the first embodiment, and the moving unit 25 is driven using the vibration of the magnet 24 as a driving force, so that the lens holder 26 is optically driven. It has a function of moving along the optical axis direction of the lens 32.

  In the present embodiment, the piezoelectric element 23 can have the same material and shape as the piezoelectric element 3 of FIG. However, although the magnet 24 has the same cross-sectional shape and magnetization direction as the magnet 4 of FIG. 1, the length of the lens 32 in the radial direction is larger than that of the magnet 4. Usually, in the lens module using two or more combination lenses, the lens diameters thereof are different. In the present embodiment, the outer diameter of the lens holder 26 of the lens portion having a small diameter is reduced by using this. By increasing the length of the magnet 24 by that amount, it is possible to achieve stabilization of the lens movement and reduction in height by securing the sliding force of the driving body.

  Also in the present embodiment, as described above, a configuration in which a vibration damping material is inserted into the portion of the housing 27 to which the piezoelectric element 23 is fixed, and a weight member is inserted between the vibration damping material and the piezoelectric element 23. By taking it, vibration noise can be removed.

  Here, as a specific example of the lens module of the present embodiment, the material and shape of the piezoelectric element 23 and the housing 27 can be the same as the specific example shown in the first embodiment. The magnet 24 bonded to one end face side of the piezoelectric element 23 is a neodymium magnet having a cross-sectional dimension of 1.2 mm × 3.0 mm, and a height of 1.0 mm, which is bonded with a thermosetting epoxy resin. 2A and 2B, a housing 7 made of polycarbonate having the shape shown in FIGS. 2A and 2B is manufactured, and the other end face side of the piezoelectric element 3 is shown in FIG. 2B. Adhesive with epoxy resin at the indicated position.

  Next, a moving part 25 having an outer diameter of 5.5 mm, an inner diameter of 4.5 mm, and a height of 1.5 mm made of a material of SUS430 is produced, and this moving part 25 is bonded to a lens holder part made of polycarbonate with an epoxy resin. The holder 26 is completed. The outer diameter D5 of the portion of the lens holder 26 where the moving portion 25 is formed is 7.5 mm, the inner diameter D6 is 3.0 mm, the outer diameter D4 of the other portions is 8.5 mm, and the inner diameter D7 is 5.0 mm. A lens module having the structure shown in FIGS. 2A and 2B is obtained by supporting the lens holder 26 on the guide pin 28 made of SUS304 and adsorbing the magnet 24 and the moving portion 25 by magnetic force. be able to.

  Next, the function of the lens driving mechanism of the lens module according to the first and second embodiments will be described.

  FIG. 3 is a timing chart showing the relationship between the drive voltage, the displacement amount of the piezoelectric element, and the movement amount of the moving unit with respect to time of the piezoelectric elements 3 and 23 provided in the lens module according to the above-described embodiment.

  In these lens modules, when the height of the piezoelectric elements 3 and 23 is about 1.5 to 2 mm, the resonance frequency becomes about 150 kHz or more. Therefore, the frequency of the AC applied voltage (drive voltage) to the piezoelectric elements 3 and 23 is increased. Is about 20 to 30 kHz, the influence of the harmonic component can be almost ignored, so that the input voltage waveform and the output displacement waveform are similar.

  As shown in FIG. 3, when the time t1 and t2 having different slopes are set so as to satisfy the relationship of tl> t2 with respect to the triangular input voltage (drive voltage) waveform, the displacement amounts of the piezoelectric elements 3 and 23 are the time. It slowly grows over time t1, and shrinks rapidly at time t2. Here, if the time t2 is set so that an acceleration equal to or greater than the maximum static frictional force generated between the moving parts 5 and 25 and the magnets 4 and 24 is obtained, the moving parts 5 and 25 and the piezoelectric element 3 at the time t1. , 23 move together, and slip occurs between the moving parts 5, 25 and the piezoelectric elements 3, 23 at time t2. If this is repeated continuously, the moving part and the lens holders 6 and 26 move in one direction with respect to the stationary members (housings 7 and 27).

  Therefore, when the duty ratio is defined by the relational expression of duty ratio = t1 / (t1 + t2) using time t1 and time t2, the speed and moving direction of the moving units 5 and 25 are controlled by changing the duty ratio. Can do.

  Here, the case where the waveform of the input voltage (driving voltage) having a triangular wave shape is given as shown in FIG. 3 is explained, but the input voltage (driving voltage) having a rectangular wave shape whose frequency is adjusted according to the shape of each component is described. Even if it is applied, the piezoelectric ceramic elements 3 and 23 can be similarly driven.

  Further, when the electro-mechanical conversion element is a piezoelectric element made of a laminated piezoelectric ceramic as in the above embodiment, a sufficient lens driving force can be obtained with a low voltage and low power, and Patent Document 2 Since there is no drive shaft (rod) like 3, there is no vibration attenuation due to the drive shaft, and stable movement without loss of drive energy is possible.

  As described above, according to the lens module of the present invention, it is possible to stably move the optical lens along the optical axis direction, and it is easy to assemble and has little variation, and it is easy to reduce the height and size. As a result, it is particularly suitable for use as a lens module with an autofocus and zoom function of a camera of a mobile phone or a digital still camera.

  Note that the present invention is not limited to the above-described embodiments and specific examples thereof, and the structure and shape of piezoelectric elements and magnets, materials, moving parts and lens holders, housing materials, The shape and the like can be selected and designed.

The figure which shows the basic composition of the lens module which concerns on 1st embodiment of this invention, Fig.1 (a) is an external appearance top view from an upper surface direction, FIG.1 (b) is the AA line of Fig.1 (a). Side surface sectional drawing in a direction. The figure which shows the basic composition of the lens module which concerns on 2nd embodiment of this invention, Fig.2 (a) is an external appearance top view from an upper surface direction, FIG.2 (b) is the AA line of Fig.2 (a). Side surface sectional drawing in a direction. 6 is a timing chart showing the relationship between the driving voltage of the piezoelectric element included in the lens modules according to the first and second embodiments, the displacement amount of the piezoelectric element, and the movement amount of the moving body.

Explanation of symbols

2, 32, 33 Optical lens 3, 23 Piezoelectric element 4, 24 Magnet 5, 25 Moving part 6, 26 Lens holder 7, 27 Housing 8, 28 Guide pin 9, 29 Guide part 11, 12, 41, 42 Outer diameter 13 , 43, 44 ID

Claims (4)

  A driving body comprising an electric / mechanical conversion element fixed at one end to a stationary member and a magnet fixed at the other end of the electric / mechanical conversion element, a lens holder having a cylindrical portion, and supported by the lens holder And a moving part made of a material that can be attracted to the magnet is formed in a part of the cylindrical portion of the lens holder, and the magnetization direction of the magnet is the radial direction of the optical lens. Or in the outer peripheral direction, and further, the magnet is vibrated by vibration generated by the electro / mechanical conversion element, and the moving unit is driven by using the vibration of the magnet as a driving force, thereby moving the lens holder to the light of the optical lens. It has a function of moving along the axial direction, and the outer diameter of the portion where the moving portion is formed in the cylindrical portion of the lens holder is smaller than the outer diameter of the other portion. Lens module that.   An inner diameter of a portion of the lens holder where the moving portion is formed is smaller than other portions, and an optical lens having a different outer diameter is supported on each of the smaller inner diameter portion and the other portion. Item 14. The lens module according to Item 1.   The moving part is driven by applying a voltage to the electro / mechanical conversion element to vibrate the magnet so that the speed of expansion and contraction in the electro / mechanical conversion element are different. The lens module according to claim 1 or 2.   The lens module according to claim 1, wherein the electro / mechanical conversion element is a multilayer piezoelectric ceramic element.

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