JP2009165317A - Electromechanical conversion actuator and lens module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable electromechanical conversion actuator having large specific gravity, corrosion resistance, and weight having the enhanced adhesion with a piezoelectric element, and to provide a lens module using the electromechanical conversion actuator, which has high moving speed and enables excellent lens driving. <P>SOLUTION: The electromechanical conversion actuator is composed of a magnet 1, the piezoelectric element 3, and the weight 2, the weight 2 being bonded to one end of the piezoelectric element 3, and the magnet 1 being bonded to the other end of the piezoelectric element 3. The composition of the weight 2 contains W of 85 to 98%, Ni of 1 to 12%, Mo of 0.1 to 2.0%, Fe of 1.0% or less, or W of 85 to 98%, Ni of 1 to 12%, Mo of 0.1 to 2.0%, and Co of 2.0% or less. The weight 2 is manufactured by sintering, and an average surface roughness Ra on the adhesive surface of the weight 2 with the piezoelectric element 3 is larger than 0.1 μm and less than 60 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electromechanical conversion actuator used in a camera lens driving mechanism such as a mobile phone and a digital still camera, and a lens module using the electromechanical conversion actuator.

  Actuators are used in various industrial and consumer devices. Among them, an electromechanical conversion actuator using a piezoelectric element as an electromechanical conversion element is used in many devices, taking advantage of the feature that positioning can be performed with high accuracy. Usually, when a piezoelectric element is used as an actuator, one end in a displacement direction is fixed as a fixed end, and the other end portion is used by being coupled to an object to be moved by some method. When the fixed end moves, a displacement leakage that reduces the amount of displacement at the other end of the piezoelectric element occurs, and the amount of movement of the object decreases, resulting in a decrease in driving efficiency. In order to prevent this and to reduce the displacement of the fixed end, the fixed end of the piezoelectric element is bonded to a heavy member, that is, a weight, to constitute an actuator, and it is used by bonding it to a substrate such as a housing There are many.

  In addition, in order to give the camera an autofocus and zoom function, a mechanism for moving the optical lens minutely along the optical axis is necessary. In recent years, as seen in digital cameras and camera-equipped mobile phones, Accordingly, a lens driving device using an electromechanical conversion actuator using a piezoelectric element has been proposed instead of a method using an electromagnetic motor. 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 a piezoelectric element and is displaced together with the piezoelectric element, and friction between the driving member and the driven member. A means using a magnet is shown as means for applying a pressing force for coupling.

  As a method for enabling smaller and more stable driving than the driving device of Patent Document 1, the structure of a lens module using the lens driving device shown in FIG. 6 can be considered. 6A and 6B show a basic configuration of the lens module. FIG. 6A is an external plan view from the top surface direction, and FIG. 6B is a side cross-sectional view in the CC line direction of FIG. is there. 6, a cylindrical lens holder 63 having a lens 60 on the inner periphery, an electromechanical conversion actuator that moves the lens holder 63 in the optical axis direction of the lens, and a housing that houses the lens holder 63 and the electromechanical conversion actuator. 64. The electromechanical conversion actuator includes a magnet 62, a piezoelectric element 61, and a weight 69. The weight 69 is bonded to one end of the piezoelectric element 61, and the magnet 62 is bonded to the other end of the piezoelectric element 61. 69 is fixed to the housing 64, vibrates the magnet 62 by vibration generated by the piezoelectric element 61, and is made of a material that can be attracted to the magnet 62 installed in a part of the lens holder 63 by using the vibration of the magnet 62 as a driving force. It has a function of moving the lens holder 63 by slidingly driving the movable body 65. The lens holder 63 is movably supported by the guide pin 66 to prevent tilting or rotation.

  A voltage that expands and contracts at different speeds during expansion and contraction is applied to the piezoelectric element 61, the magnet 62 is vibrated in parallel with the optical axis, and the moving body 65 is moved in the expansion / contraction direction, thereby moving the lens holder 63 to the optical axis. Can be moved in the direction.

  Since the actuator used in the camera mechanism as described above is naturally required to be downsized, the weight 69 is made of a material having a high specific gravity so as to make the weight as large as possible. Among them, tungsten has a very high specific gravity of 19.3 g / cc and is suitable as a weight material. Conventionally, a tungsten alloy mainly composed of tungsten has been used as the weight material.

  However, tungsten alloys are very oxidizable and have a problem with corrosion resistance. Therefore, Patent Document 2 describes a method of improving corrosion resistance by applying Ni plating to the surface of a weight when using a tungsten alloy as a weight material of an electromechanical conversion actuator using a piezoelectric element or the like.

  On the other hand, in Patent Document 3, as a weight fixed to the rotating shaft of the small vibration generator, the material composition of tungsten alloy is W: 85% to 98%, Ni: 1% to 12%, Mo: 0 1% or more and 2.0% or less, Fe: 1.0% or less or W: 85% or more and 98% or less, Ni: 1% or more and 12% or less, Mo: 0.1% or more and 2.0% or less, Co : A material in the range of 2.0% or less is shown, and it is described that this tungsten alloy has a large specific gravity, good corrosion resistance, and does not require Ni plating.

JP 7-274546 A JP 2005-218244 A JP 7-166287 A

  However, as shown in Patent Document 2, when Ni plating is applied to a tungsten alloy, the manufacturing cost corresponding to that is generated, and the cost becomes high. Further, when Ni plating becomes a small member, it becomes difficult to flatten the surface, and it becomes difficult to obtain flatness of the bonding surface. Further, when bonding to the piezoelectric element is performed using an adhesive, the Ni plating surface has a lower adhesive strength than the normal metal surface, so that there is a problem that the adhesive strength is lowered. To overcome this, the amount of adhesive is increased and the adhesive strength is increased by adhering the adhesive to the side of the piezoelectric element, but this restricts the movement of the piezoelectric element and reduces the amount of displacement. Or the protruding adhesive protrudes to the member fixing jig, making it difficult to remove from the jig.

  On the other hand, the tungsten alloy material disclosed in Patent Document 3 does not require Ni plating, but when this is used as a weight member for an electromechanical conversion actuator using a piezoelectric element, it is caulked to the piezoelectric element as in Patent Document 3. It cannot be attached and adhesive fixing is essential. However, when this tungsten alloy is also bonded to the piezoelectric element as a weight, there is a problem that sufficient adhesive strength cannot be obtained and reliability is insufficient.

  An object of the present invention is to solve the above-mentioned problems, and to provide a highly reliable electromechanical conversion actuator having a large specific gravity and corrosion resistance, and having a weight with a strong adhesive strength with a piezoelectric element, and the electromechanical conversion actuator An object of the present invention is to provide a lens module capable of driving a lens with a large moving speed using the lens.

  In order to solve the above problems, an electromechanical conversion actuator according to the present invention includes a magnet, a piezoelectric element, and a weight. The weight is bonded to one end of the piezoelectric element, and the magnet is bonded to the other end of the piezoelectric element. In the electromechanical conversion actuator configured as described above, the composition of the weight is W: 85% to 98%, Ni: 1% to 12%, Mo: 0.1% to 2.0%, Fe: 1. 0% or less, or W: 85% to 98%, Ni: 1% to 12%, Mo: 0.1% to 2.0%, Co: 2.0% or less, An average surface roughness Ra of an adhesion surface of the weight with the piezoelectric element is greater than 0.1 μm and less than 60 μm.

  The lens module according to the present invention includes a cylindrical lens holder having a lens on an inner periphery, an electromechanical conversion actuator that moves the lens holder in an optical axis direction of the lens, the lens holder, and the electromechanical conversion. A housing for accommodating the actuator, and the electromechanical conversion actuator includes a magnet, a piezoelectric element, and a weight. The weight is bonded to one end of the piezoelectric element, and the magnet is bonded to the other end of the piezoelectric element. The weight is fixed to the housing, vibrates the magnet by vibration generated by the piezoelectric element, and is attracted to the magnet installed in a part of the lens holder using the vibration of the magnet as a driving force. A lens module having a function of moving the lens holder by sliding a movable body made of a possible material, the composition of the weight being W 85% or more and 98% or less, Ni: 1% or more and 12% or less, Mo: 0.1% or more and 2.0% or less, Fe: 1.0% or less, or W: 85% or more and 98% or less, Ni: 1% or more and 12% or less, Mo: 0.1% or more and 2.0% or less, and Co: 2.0% or less. The weight is manufactured by a sintering method, and the weight is bonded to the piezoelectric element. The average surface roughness Ra is greater than 0.1 μm and less than 60 μm.

  Further, the shape of the housing is a rectangular parallelepiped shape in which the side surface of the lens holder is inscribed through a gap of 1 mm or less, and the surface shape of the portion fixed to the housing of the weight may be a triangle or a trapezoid. Good.

  In the present invention, an electromechanical actuator composed of a magnet, a piezoelectric element, and a weight, with a weight attached to one end of the piezoelectric element and a magnet attached to the other end, has a large specific gravity and good corrosion resistance without Ni plating. Using the tungsten alloy having the above composition as the material of the weight, and making the average surface roughness Ra of the bonding surface of the weight with the piezoelectric element greater than 0.1 μm and less than 60 μm, the piezoelectric element and the weight are firmly bonded. Strength is obtained.

  As a result, it has a weight that is stable even in a high temperature and high humidity environment, can eliminate the need for Ni plating, and can reduce the manufacturing cost. Thus, strong adhesion between the piezoelectric element and the weight can be easily obtained, and sufficient reliability can be obtained. An electromechanical conversion actuator can be provided.

  As described above, according to the present invention, a highly reliable electromechanical conversion actuator having a weight having high specific gravity and corrosion resistance and having a strong adhesive strength with a piezoelectric element, and a moving speed using the electromechanical conversion actuator A lens module capable of driving a lens with a large size can be obtained.

  Hereinafter, embodiments of the present invention will be described based on examples.

  FIG. 1 is a perspective view showing an embodiment of an electromechanical transducer according to the present invention, and is a perspective view when the electromechanical transducer is fixed on a substrate for measurement. In FIG. 1, the electromechanical conversion actuator of this embodiment includes a magnet 1, a piezoelectric element 3, and a weight 2. The weight 2 is bonded to one end of the piezoelectric element 3, and the magnet 1 is bonded to the other end of the piezoelectric element 3. And is fixed on the substrate 4.

  A method for manufacturing the weight 2 used in this embodiment will be described below. First, each metal powder is weighed and mixed so as to have a predetermined composition. This mixed powder is pressed into a desired shape with a mold and fired in a hydrogen atmosphere to obtain a sintered tungsten alloy sample. Then, it cut | disconnects in the shape of FIG. 1, and the weight 2 is obtained by grind | polishing the adhesive surface with a piezoelectric element.

  Here, in order to confirm the effect of the present invention, the sample of the example in which the material and the surface roughness of the surface to be bonded to the piezoelectric element are within the scope of the present invention, and the comparative example in which the scope of the present invention was changed out of the range A sample was prepared and an adhesive strength test was performed. In addition, a sample of a comparative example in which the composition of the tungsten alloy was changed within the scope of the present invention and beyond the scope of the present invention was separately prepared, and the corrosion resistance and the displacement amount as an electromechanical conversion actuator were evaluated.

  First, a 2 mm × 2 mm × 5 mm prism is used as the weight for the sample for adhesion strength test, and the end surface of the prism of the piezoelectric element (1 mm × 1 mm × 5 mm) is thermoset on the 2 mm × 2 mm end surface of this prism. A test piece bonded with an epoxy adhesive was prepared. As the weight composition, W 90 wt%, Ni 8 wt%, Mo 1.5 wt%, Fe 0.5 wt% were used. Further, as one of comparative examples, a weight having the same shape as the weight obtained by applying Ni plating to a tungsten-nickel alloy was produced, and a test piece was similarly produced. Adhesive curing was performed by holding at 100 ° C. for 1 hour.

  FIG. 2 is a diagram showing an adhesion strength test method. As shown in FIG. 2, the weight 9 is fixed by a jig 10 and a point 3 mm away from the bonding portion 12 of the piezoelectric element 11 is fixed to the piezoelectric element 11. The load at which the bonded portion breaks was measured by pressing from the direction perpendicular to the length direction. The loading speed was 2 mm / min. Table 1 shows the results of the above adhesive strength test.

  As can be seen from Table 1, in the case of the tungsten alloy having the above composition, in the case of the comparative example in which the surface roughness Ra of the weight is 0.1 μm or less or 60 μm or more, the adhesive strength is the same as that of the weight plated with Ni. It can be seen that when the surface roughness Ra of the bonding surface is greater than 0.1 μm and less than 60 μm, an adhesive strength greater than that of the Ni-plated tungsten-nickel alloy weight can be obtained. A similar relationship between the surface roughness Ra of the bonding surface and the bonding strength was obtained even in the W-Ni-Mo-Co alloy having the composition range of the present invention. In addition, even when the surface is not polished after sintering, when the sintering condition is set so that the surface roughness Ra is greater than 0.1 μm and less than 60 μm, the adhesive strength is comparable to that of the Ni-plated product. The result was large.

  The above effect of the present invention is that, in the range where Ra is greater than 0.1 μm and less than 60 μm, the fine unevenness of the adhesive surface increases the contact area with the adhesive and the unevenness in the direction perpendicular to the load direction. This is probably because the adhesive portion that entered the recess was subjected to a load. When Ra is 0.1 μm or less, there is no uneven portion enough to receive a load, and when it is 60 μm or more, the unevenness is large.

  Next, the corrosion resistance of the weight of the electromechanical conversion actuator and the amount of displacement as the electromechanical conversion actuator were evaluated. A sample for evaluation was obtained by bonding a laminated piezoelectric element having a cross section of 1 mm × 1 mm and a height of 1.5 mm on a plate-shaped weight with a thermosetting epoxy adhesive, and further applying a 1 mm × 1 mm × 1.5 mm magnet to the piezoelectric. An electromechanical conversion actuator was constructed by bonding to the upper surface of the element. In order to measure the amount of displacement, the lower surface of the weight of the electromechanical conversion actuator was bonded to a 10 mm × 10 mm × 1 mm plastic plate with a thermosetting epoxy adhesive to produce a sample for evaluation. Here, the surface roughness Ra of the bonding surface of the weight with the piezoelectric element is processed to 0.3 μm, and in order to confirm the effect of the present invention, the composition of the tungsten alloy of the weight is within the scope of the present invention and the present invention. Samples of comparative examples and samples obtained by subjecting a tungsten-nickel alloy to Ni plating were also produced.

  Corrosion resistance is evaluated by conducting a constant temperature and humidity test that is held for 500 hours under conditions of a temperature of 85 ° C. and a humidity of 85%, and observing the surface of the weight of the sample taken after the test and observing the appearance for corrosion. went.

  FIG. 3 is a diagram showing a method for evaluating a displacement amount as an actuator. As shown in FIG. 3, the plastic plate 34 of the produced sample for evaluation is placed on a flat table 30, the piezoelectric element 33 is driven using an oscillator 38 and an amplifier 37, and the displacement of the upper surface of the magnet 31 is changed by laser displacement. The total was measured by 36. The driving conditions were a sine wave with a frequency of 100 kHz and a driving voltage of ± 1V.

  The displacement reduction rate is a magnet when an actuator is configured by adhering a weight and a magnet to the piezoelectric element with respect to the displacement when the single piezoelectric element is installed on the table 30 and measured by the same evaluation system as in FIG. The amount of displacement on the upper surface of the film was measured and evaluated by the rate of decrease.

  Table 2 shows the surface state of the weight by the constant temperature and humidity test when the weight composition is made of a W—Ni—Mo—Fe alloy, the displacement reduction rate, and the piezoelectric measured by the same sample and evaluation method as in the above adhesive strength test. The evaluation result of the breaking strength of the adhesion part with an element is shown collectively.

  From Table 2, it was found that within the scope of the present invention, the breaking strength was high, the displacement reduction rate was small, and the appearance did not change even after the constant temperature and humidity test.

  On the other hand, samples with a tungsten content of less than 85% or greater than 98% resulted in a large displacement reduction rate. A sample with a nickel content of less than 1% or greater than 12% resulted in a large displacement reduction rate. When the amount of molybdenum was less than 0.1%, rust was generated after high temperature and high humidity, and the breaking strength was small. In addition, a sample having a molybdenum content of 2% or more showed a large displacement reduction rate. In the sample with iron larger than 1%, rust was generated after constant temperature and humidity, and the breaking strength was reduced. The sample plated with Ni had a small breaking load.

  Table 3 shows similar evaluation results when the weight composition is made of a W—Ni—Mo—Co alloy.

  From Table 3, the results were that the breaking strength was large, the displacement reduction rate was small within the range of the present invention, and the appearance did not change even after the constant temperature and humidity test. On the other hand, samples with a tungsten content of less than 85% or greater than 98% resulted in a large displacement reduction rate. A sample with a nickel content of less than 1% or greater than 12% resulted in a large displacement reduction rate. When the amount of molybdenum was less than 0.1%, rust was generated after high temperature and high humidity, and the breaking load was small. In addition, a sample having a molybdenum content of 2% or more showed a large displacement reduction rate. In the sample with more than 2% cobalt, rust was generated after constant temperature and humidity, and the breaking strength was reduced.

  FIG. 4 is a view showing an embodiment of a lens module according to the present invention, and shows the basic configuration of the lens module. FIG. 4 (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 4 (a). 4, a cylindrical lens holder 45 having a lens 44 on the inner periphery, an electromechanical conversion actuator that moves the lens holder 45 in the optical axis direction of the lens 44, and the lens holder 45 and the electromechanical conversion actuator are accommodated. The electromechanical actuator includes a magnet 41, a piezoelectric element 47, and a weight 49. The weight 49 is bonded to one end of the piezoelectric element 47, and the magnet 41 is bonded to the other end of the piezoelectric element 47. The weight 49 is fixed to the housing 43, vibrates the magnet 41 by vibration generated by the piezoelectric element 47, and can be attracted to the magnet 41 installed in a part of the lens holder 43 by using the vibration of the magnet 41 as a driving force. It has a function to move the lens holder 45 by slidingly driving the moving body 46 made of the above.

  Considering the current camera module size, the housing 43 and the lens holder 45 must be made as small as possible. For this reason, the shape of the housing 43 is a rectangular parallelepiped shape in which the side surface of the lens holder 45 is inscribed through a gap of 1 mm or less. It is desirable. Also in the electromechanical actuator of the present embodiment, it is necessary to reduce the size and the height of the weight 49 along with the miniaturization of the piezoelectric element 47, and the weight 49 is desirably 1.0 mm or less in height. The weight 49 is preferably located inside the actuator from the sliding surface so as not to prevent the sliding of the magnet 41 and the moving body 46. Therefore, the length in the direction perpendicular to the sliding surface of the weight 49 is preferably shorter than the distance from the inner corner of the housing 43 to the magnet sliding surface. As a result, considering the arrangement of the actuators at the corners of the housing 43 as the shape of the weight 49, the surface shape in the direction perpendicular to the displacement direction is triangular or A trapezoid is desirable. Therefore, in this embodiment, the weight 49 has the shape of a right-angled isosceles triangle having a side length of 2 mm and a height of 1 mm. The housing 43 has an outer shape of 10 × 10 × 7 mm.

  In this embodiment, the material composition of the weight 49 constituting the actuator was W 90 wt%, Ni 8 wt%, Mo 1.5 wt%, and Fe 0.5 wt%. For comparison, a lens module by an actuator using a weight having a composition of W99 wt%, Ni 0.5 wt%, Mo 0.3 wt%, Fe 0.2 wt%, which has a large displacement attenuation amount as shown in Table 3, is also provided. Made and evaluated. The surface roughness Ra of the adhesion surface of the weight 49 to the piezoelectric element 47 was 0.3 μm. The actuator weight 49 was fixed to the housing 43 with an epoxy thermosetting adhesive.

  A steel plate that is attracted to the magnet is installed on the lens holder 45 side as a moving body 46 at the sliding portion with the magnet. The lens holder 45 has a substantially cylindrical shape and holds a lens 44 on the inner peripheral side thereof. The lens 44 is attached so that the central axis direction of the cylinder coincides with the optical axis of the lens.

  FIG. 5 is a block diagram showing an evaluation system for a lens module. The piezoelectric element 47 is driven using an oscillator 38 and an amplifier 37, the displacement of the upper surface of the lens holder 45 is measured with a laser displacement meter, and the moving speed is measured. Was calculated. The driving conditions are a frequency of 100 kHz and a driving voltage of ± 1V. The drive voltage waveform was a triangular wave, and the ratio of voltage increase time to voltage decrease time was 7: 3. Table 4 shows the measurement results.

  In the lens module of this example, the moving speed was 4.5 mm / sec, while in the comparative example in which the displacement reduction rate was large, the value was as small as 2.5 mm / sec. As a result, in the lens module of the present invention, since the displacement reduction rate of the actuator is small, the moving speed can be increased and good lens driving can be obtained.

  As described above, the present invention has a weight that is stable even in a high-temperature and high-humidity environment, that does not require Ni plating, and that can reduce the manufacturing cost, and that a strong adhesion between the piezoelectric element and the weight can be easily obtained. Thus, an electromechanical conversion actuator having high reliability is possible, and a lens module capable of driving a lens with a high moving speed using the electromechanical conversion actuator can be obtained.

  Needless to say, the present invention is not limited to the above-described embodiments, and magnets, piezoelectric elements, shapes and dimensions of weights, arrangements, moving bodies, lens holders, housing materials, shapes, etc., depending on the purpose. Can be selected and designed.

The perspective view which shows one Example of the electromechanical conversion actuator by this invention. The figure which shows the adhesive strength test method. The figure which shows the evaluation method of the displacement amount as an actuator. The figure which shows one Example of the lens module by this invention, Fig.4 (a) is an external appearance top view from an upper surface direction, FIG.4 (b) is side surface sectional drawing in the AA line direction of Fig.4 (a). The block diagram which shows the evaluation system of a lens module. FIG. 6A is a diagram showing a basic configuration of a lens module that enables small and stable driving, FIG. 6A is an external plan view from the top surface direction, and FIG. 6B is a CC line direction in FIG. 6A. Side surface sectional drawing.

Explanation of symbols

1, 31, 41, 62 Magnets 2, 9, 49, 69 Weights 3, 11, 33, 47, 61 Piezoelectric element 4 Substrate 10 Jig 12 Bonding part 30 Base 34 Plastic plate 36 Laser displacement meter 37 Amplifier 38 Oscillator 43, 64 Housing 44, 60 Lens 45, 63 Lens holder 46, 65 Moving body 66 Guide pin

Claims (3)

  An electromechanical conversion actuator comprising a magnet, a piezoelectric element, and a weight, wherein the weight is bonded to one end of the piezoelectric element, and the magnet is bonded to the other end of the piezoelectric element. : 85% to 98%, Ni: 1% to 12%, Mo: 0.1% to 2.0%, Fe: 1.0% or less, or W: 85% to 98%, Ni 1% or more and 12% or less, Mo: 0.1% or more and 2.0% or less, and Co: 2.0% or less. The weight is manufactured by a sintering method, and the weight is bonded to the piezoelectric element. An electromechanical conversion actuator having an average surface roughness Ra of greater than 0.1 μm and less than 60 μm.   A cylindrical lens holder having a lens on the inner periphery, an electromechanical conversion actuator that moves the lens holder in the optical axis direction of the lens, and a housing that houses the lens holder and the electromechanical conversion actuator The electromechanical conversion actuator includes a magnet, a piezoelectric element, and a weight, the weight is bonded to one end of the piezoelectric element, the magnet is bonded to the other end of the piezoelectric element, and the weight is attached to the casing. A moving body made of a material that is fixed and vibrates with the vibration generated by the piezoelectric element and that can be attracted to the magnet installed in a part of the lens holder by using the vibration of the magnet as a driving force. A lens module having a function of moving the lens holder by dynamic driving, wherein the weight has a composition of W: 85% to 98%, Ni: 1% or more 2% or less, Mo: 0.1% to 2.0%, Fe: 1.0% or less, or W: 85% to 98%, Ni: 1% to 12%, Mo: 0.1 % To 2.0%, Co: 2.0% or less, the weight is manufactured by a sintering method, and the average surface roughness Ra of the surface of the weight to be bonded to the piezoelectric element is greater than 0.1 μm. A lens module characterized by being less than 60 μm.   The shape of the housing is a rectangular parallelepiped shape in which the side surface of the lens holder is inscribed through a gap of 1 mm or less, and the surface shape of the portion fixed to the housing of the weight is a triangle or a trapezoid. The lens module according to claim 2.

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