JP2006154044A - Focal length variable lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a focal length variable lens small-sized and to improve reliability of the lens. <P>SOLUTION: The focal length variable lens is provided with: a cylindrical giantmagnetostrictive element 11 of which the hollow part 11c serves as an optical path; elastic sealing members 14a and 14b arranged in the optical path; a fluid 15 filled in the hollow part 11c of the giantmagnetostrictive element 11 with the sealing members 14a and 14b; and a coil 12. The giantmagnetostrictive element 11 is dislocated in an axial direction when the electric current flowing in the coil 12 is varied, and the pressure applied to the fluid 15 varies, and the sealing members 14a and 14b are deformed. In this way, in the focal length variable lens of the present invention, the focal length is varied according to the change in the electromagnetic field given to the giantmagnetostrictive element 11 and the movement of the fluid does not follow. Consequently, the entire focal length variable lens is made small and fluid leakage or the like is hardly caused. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a variable focal length lens, and more particularly to a variable focal length lens using a magnetostrictive material.

  Usually, in order to make the focal length variable in an optical apparatus, a method of using a plurality of lenses and changing the distance between these lenses is common. However, this method not only requires a motor for driving the lens, but also requires a space in consideration of the movement of the lens, so it is difficult to downsize the entire optical apparatus. It was.

As a method for solving such a problem, Patent Document 1 proposes a variable focal length lens using a liquid. The focal length variable lens described in Patent Document 1 has a structure in which elastic films are provided above and below a frame and a liquid is filled between the elastic films. When the focal length is changed, the curvature of the elastic film is changed by increasing or decreasing the amount of liquid between the elastic films by using an enclosure adjuster, thereby expanding (or contracting) the elastic film.
JP-A-4-67001

  However, the variable focal length lens described in Patent Document 1 requires a sealed adjuster that increases or decreases the amount of liquid between elastic films and a pipe for moving the liquid. It is difficult to reduce the size. In addition, since the movement of the liquid is accompanied when the focal length is changed, liquid leakage or the like is likely to occur, and there is a possibility that the reliability of the optical device incorporating the same is impaired.

  Accordingly, an object of the present invention is to provide a variable focal length lens that can be easily downsized and is excellent in reliability.

  The present inventor paid attention to a so-called “magnetostrictive element”, in particular, “a giant magnetostrictive element”, while intensively studying to improve the variable focal length lens. Magnetostrictive elements that expand and contract in response to the application of a magnetic field have been known for a long time, but conventional magnetostrictive elements have a small displacement, and thus have been rarely used practically. However, in recent years, a magnetostrictive element (super magnetostrictive element) having a very large displacement of 1500 ppm to 2000 ppm has been known, and the present inventor has come to consider applying this to driving a variable focal length lens. .

  The present invention has been made based on such an idea, and the focal length variable lens according to the present invention includes at least one cylindrical magnetostrictive element having at least a part made of a magnetostrictive material and having a hollow part as an optical path. A sealing member having a portion disposed on the optical path, a fluid sealed in the hollow portion of the magnetostrictive element by the sealing member, and means for displacing the magnetostrictive element at least in an axial direction by applying a magnetic field; And at least a part of a portion of the sealing member disposed on the optical path has elasticity that can be deformed in accordance with displacement of the magnetostrictive element in the axial direction. .

  According to the variable focal length lens of the present invention, since the focal length changes due to the change of the magnetic field applied to the magnetostrictive element, the liquid does not move. For this reason, not only can the entire focal length variable lens be reduced in size, but also liquid leakage is less likely to occur. Here, the “axial direction” means a direction penetrating through the hollow portion of the magnetostrictive element, and coincides with a direction serving as an optical path of the focal length variable lens. In the present invention, “cylindrical” refers to a shape having a through hole, and is a concept including a shape such as an annular shape or a donut shape.

  In the variable focal length lens according to the present invention, the entire magnetostrictive element is preferably made of a magnetostrictive material. According to this, since a large displacement can be obtained, not only the variable range of the focal length is widened, but also a correct lens shape can be obtained, so that good optical characteristics can be obtained.

  The means for displacing preferably includes a coil wound in the circumferential direction of the magnetostrictive element. According to this, since the direction of the magnetic flux generated by the coil is the axial direction of the magnetostrictive element, it is possible to displace the magnetostrictive element mainly in the axial direction.

  The variable focal length lens of the present invention preferably further comprises a magnetic bias applying means for applying a magnetic bias to the magnetostrictive element. When a magnetic field is applied to the magnetostrictive element, it normally only expands. However, if such a magnetic bias applying means is provided, the magnetostrictive element can be expanded and contracted. Here, as the magnetic bias applying means, a permanent magnet may be used, or a circuit for applying a DC bias current to the coil may be used.

  The sealing member preferably has a deformable region set to be less than an inner diameter of at least a part of the magnetostrictive element. According to this, since the deformation amount of the sealing member corresponding to the displacement of the magnetostrictive element becomes very large, the variable range of the focal length can be further expanded. Specifically, the deformable region is less than the inner diameter of at least a part of the magnetostrictive element by providing a recess that expands the volume in the inner wall portion of the magnetostrictive element or by providing a fixing member that restricts the deformable region of the sealing member. Can be set to

  As described above, the variable focal length lens according to the present invention has a structure in which a fluid is enclosed in a hollow portion of a cylindrical magnetostrictive element, instead of increasing or decreasing the amount of liquid unlike a conventional variable focal length lens. Therefore, when changing the focal length, there is no need to inject a fluid into the hollow portion or to discharge the fluid out of the hollow portion. This eliminates the need for a mechanism such as an enclosing adjuster or a pipe, which has been necessary in the past, and allows the entire focal length variable lens to be reduced in size. In addition, since the liquid does not move when the focal length is changed, liquid leakage or the like is unlikely to occur. For this reason, it is possible to improve the reliability of the optical device incorporating the variable focal length lens according to the present invention.

  In addition, since the focal length of the variable focal length lens according to the present invention changes due to a change in the magnetic field applied to the magnetostrictive element, the response speed is faster than a general mechanism that changes the focal length by changing the distance between the lenses. Is extremely fast. Further, since there is no mechanically actuated part, there is an advantage that mechanical failure or the like hardly occurs. Moreover, the mechanism for changing the distance between the lenses tends to increase the size in the direction along the optical path due to its nature. However, in the variable focal length lens according to the present embodiment, the size in the direction along the optical path (= axial direction). The size can be made very small.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a diagram schematically showing the structure of a variable focal length lens 10 according to a first embodiment of the present invention, where (a) is a schematic plan view, and (b) is an AA line shown in (a). It is a schematic sectional drawing in alignment with.

  As shown in FIG. 1 (a), the variable focal length lens 10 according to the present embodiment includes a giant magnetostrictive element 11, a coil 12 and a permanent magnet 13 each having a cylindrical structure. The coil 12 and the permanent magnet 13 are concentrically arranged in this order from the inside to the outside. Moreover, as shown in FIG.1 (b), the 1st sealing member 14a and the 2nd sealing member 14b are attached to the one and other end surface 11a, 11b of the giant magnetostrictive element 11, respectively. The fluid 15 serving as the lens body is enclosed in the hollow portion 11c of the giant magnetostrictive element 11 thus closed. The hollow portion 11c of the giant magnetostrictive element 11 is a portion that becomes an optical path during use.

The giant magnetostrictive element 11 is made of a giant magnetostrictive material that expands and contracts in response to application of a magnetic field, and the giant magnetostrictive material to be used is not particularly limited, but Tb _0.34 -Dy _0.66 -Fe A giant magnetostrictive material having a central composition of _1.90 can be used. The size of the giant magnetostrictive element may be appropriately selected according to the size of the target focal length variable lens 10 and the target variable focal amount.

  The coil 12 is used to change the magnetic field applied to the giant magnetostrictive element 11, and when the current passed through the coil 12 is changed by a control circuit (not shown), the magnetic field applied to the giant magnetostrictive element 11 changes. The coil 12 is wound in the circumferential direction of the giant magnetostrictive element 11. For this reason, the direction of the magnetic flux generated by the current flowing through the coil 12 is the axial direction of the giant magnetostrictive element 11. That is, when the current flowing through the coil 12 is changed, the magnetic field applied to the giant magnetostrictive element 11 changes mainly in the axial direction. Thereby, by changing the current flowing through the coil 12, the giant magnetostrictive element 11 can be displaced mainly in the axial direction.

  The permanent magnet 13 functions as a magnetic bias applying unit that applies a magnetic bias to the giant magnetostrictive element 11. The giant magnetostrictive element 11 has the smallest size when no magnetic field is applied, and has a property of expanding as the magnetic field becomes stronger. That is, the giant magnetostrictive element 11 cannot be contracted from a state where no magnetic field is applied, and can simply be expanded. Therefore, in order to “extend / contract” the giant magnetostrictive element 11, it is necessary to apply a predetermined “magnetic bias” to the giant magnetostrictive element 11 in a normal state (neutral state), and the permanent magnet 13 is used for this purpose. Is provided.

  In the present embodiment, the permanent magnet 13 is concentrically arranged with respect to the giant magnetostrictive element 11, and if the one end 13a in the axial direction is, for example, N pole and the other end 13b in the axial direction is, for example, S pole, the permanent magnet The direction of the magnetic flux generated by 13 is the axial direction of the giant magnetostrictive element 11. For this reason, a magnetic bias can be effectively applied to the giant magnetostrictive element 11 that is displaced mainly in the axial direction.

  The first and second sealing members 14a and 14b serve to seal the fluid 15 serving as the main body of the lens and serve as an optical path when in use, so that both have high transmittance for visible light. It is necessary to use materials. In addition, at least one of the first and second sealing members 14 a and 14 b needs to have elasticity that can be deformed in response to a pressure change of the fluid 15. Therefore, for one of the first and second sealing members 14a and 14b, a material such as glass that hardly deforms according to the pressure change of the fluid 15 may be used.

  In order to prevent the fluid 15 from leaking, both the first and second sealing members 14a and 14b need to have a property of not allowing the fluid 15 or air to permeate. This is because when the first and second sealing members 14a and 14b have a property of transmitting the fluid 15 and air, the fluid 15 passes through the sealing members 14a and 14b and leaks to the outside. This is because there is a possibility that the air may come out or air may penetrate the sealing members 14a and 14b and enter the inside. Not only when the fluid 15 leaks out, but also when air or the like enters the inside, there arises a problem that the curvature of the lens changes.

  In addition, although the adhesive etc. can be used for attachment to the one and other end surfaces 11a and 11b of the giant magnetostrictive element 11, the interface (adhesive surface) between the giant magnetostrictive element 11 and the sealing members 14a and 14b is used. In order to prevent leakage of the fluid 15 and intrusion of air or the like, it is necessary to securely bond using an adhesive that does not transmit these.

  The fluid 15 is a member that is a main body of the lens, and since it becomes an optical path in use, it is necessary to use a material having a high transmittance for visible light. As the material of the fluid 15, a liquid or a gel-like material having a small volume change due to pressure or temperature can be used, and water can be used as an example. In order to increase the variable range of the focal length, it is preferable to use a material having a refractive index as high as possible as the material of the fluid 15.

  The above is each element constituting the variable focal length lens 10 according to the present embodiment. As shown in FIG. 2, the giant magnetostrictive element 11 is inserted into the hollow portion 12a of the cylindrical coil 12, and the cylindrical shape. It can assemble by inserting the coil 12 in the hollow part 13c of the permanent magnet 13 which is.

  As a drive circuit for driving the variable focal length lens 10 according to the present embodiment, as shown in FIG. 3, a circuit in which a DC power source 16 and a variable resistor 17 are connected in series to a coil 12 constituting the variable focal length lens 10 is used. be able to. When such a circuit is used, the current flowing through the coil 12 can be changed by changing the resistance value of the variable resistor 17 by a control circuit (not shown).

  In addition, as a drive circuit for driving the variable focal length lens 10 according to the present embodiment, the circuit shown in FIG. 4 can be used. The circuit shown in FIG. 4 has a configuration in which a variable DC power supply 18 and a resistor 19 are connected in series to a coil 12 constituting the variable focal length lens 10, and the voltage of the variable DC power supply 18 is changed by a control circuit (not shown). By doing so, the current flowing through the coil 12 can be changed.

  Next, the operation of the variable focal length lens 10 according to the present embodiment will be described.

  First, in the normal state, that is, in the neutral state where only the magnetic bias is applied to the giant magnetostrictive element 11, the axial length L0 of the giant magnetostrictive element 11 is maintained at a certain length. The surfaces of the first and second sealing members 14a and 14b are substantially flat (see FIG. 1B). Accordingly, even if light is transmitted through the fluid 15 in this state, the lens action does not substantially occur.

  However, when the magnetic field applied to the giant magnetostrictive element 11 is increased by passing a current through the coil 12, the giant magnetostrictive element 11 expands in the axial direction according to the strength of the magnetic field. FIG. 5 is a schematic cross-sectional view showing this state. When the length of the giant magnetostrictive element 11 is changed to L1 (> L0), the pressure applied to the fluid 15 is reduced, and as a result, the first and first The surfaces of the two sealing members 14a and 14b are recessed inward. Therefore, when light is transmitted through the fluid 15 in this state, the fluid 15 acts as a concave lens.

  On the other hand, when a magnetic field applied to the giant magnetostrictive element 11 is decreased by flowing a current in a direction that cancels the magnetic bias to the coil 12, the giant magnetostrictive element 11 contracts in the axial direction according to the degree of decrease in the magnetic field. FIG. 6 is a schematic cross-sectional view showing this state. When the length of the giant magnetostrictive element 11 is changed to L2 (<L0), the pressure applied to the fluid 15 increases, and as a result, the first and first The surfaces of the two sealing members 14a and 14b swell in a convex shape. Therefore, when light is transmitted through the fluid 15 in this state, the fluid 15 acts as a convex lens.

  The curvatures of the first and second sealing members 14a and 14b can be adjusted according to the magnitude and direction of the current flowing through the coil 12, thereby making the focal length variable.

  As described above, the variable focal length lens 10 according to the present embodiment does not increase or decrease the amount of liquid as in the conventional variable focal length lens, but the fluid 15 is placed in the hollow portion 11c of the cylindrical giant magnetostrictive element 11. Since it has the enclosed structure, it is not necessary to inject the fluid 15 into the hollow portion 11c or to discharge the fluid 15 to the outside of the hollow portion 11c when changing the focal length. This eliminates the need for a mechanism such as an enclosing adjuster or a pipe, which has been necessary in the past, and allows the entire focal length variable lens to be reduced in size. In addition, since the liquid does not move when changing the focal length, liquid leakage or the like is unlikely to occur. For this reason, it is possible to improve the reliability of the optical apparatus incorporating the variable focal length lens 10 according to the present embodiment. Become.

  Further, since the focal length is changed by changing the magnetic field applied to the giant magnetostrictive element 11, the response speed is extremely fast compared to a general mechanism that changes the focal length by changing the distance between the lenses. It has the characteristics. Further, since there is no mechanically actuated part, there is an advantage that mechanical failure or the like hardly occurs. Moreover, in the mechanism for changing the distance between the lenses, the size in the direction along the optical path tends to be large due to its nature. However, in the variable focal length lens 10 according to the present embodiment, the direction along the optical path (= axial direction). It becomes possible to make the size of the very small.

  Next, a second embodiment of the present invention will be described.

  7A and 7B are diagrams schematically showing the structure of the variable focal length lens 20 according to the second embodiment of the present invention, in which FIG. 7A is a schematic plan view, and FIG. 7B is a BB line shown in FIG. It is a schematic sectional drawing in alignment with.

  As shown in FIGS. 7A and 7B, in the variable focal length lens 20 according to the present embodiment, the permanent magnet 13 is arranged on one side in the axial direction rather than in the radial direction with respect to the giant magnetostrictive element 11. This is different from the variable focal length lens 10 according to the first embodiment. Others are the same as those of the variable focal length lens 10 according to the first embodiment. Therefore, the same reference numerals are given to the same elements, and duplicate descriptions are omitted. Also in the present embodiment, one end 13a in the axial direction of the permanent magnet 13 is, for example, N pole, and the other end 13b in the axial direction is, for example, S pole.

  In the present embodiment, since the permanent magnet 13 is arranged in the axial direction of the giant magnetostrictive element 11, the size of the focal length variable lens 20 in the radial direction can be further reduced. In the present embodiment, the permanent magnet 13 is disposed on the side where the second sealing member 14b is provided, but it may be disposed on the side where the first sealing member 14a is provided. Absent.

  Next, a third embodiment of the present invention will be described.

  FIG. 8 is a diagram schematically showing the structure of the variable focal length lens 30 according to the third embodiment of the present invention, where (a) is a schematic plan view, and (b) is a CC line shown in (a). It is a schematic sectional drawing in alignment with.

  As shown in FIGS. 8A and 8B, the variable focal length lens 30 according to the present embodiment is the second embodiment in that the permanent magnets 13 are arranged on both the upper and lower sides in the axial direction of the giant magnetostrictive element 11. This is different from the variable focal length lens 20 according to the form. The other elements are the same as those of the variable focal length lens 20 according to the second embodiment, and thus the same elements are denoted by the same reference numerals, and redundant description is omitted. Also in the present embodiment, one end 13a in the axial direction of each permanent magnet 13 is, for example, an N pole, and the other end 13b in the axial direction is, for example, an S pole, and the surfaces of the two permanent magnets 13 facing each other have different polarities. Are arranged as follows.

  In the present embodiment, as in the second embodiment, not only can the size in the radial direction of the variable focal length lens 30 be reduced, but also the two permanent magnets 13 arranged above and below can be Compared to the second embodiment, the magnetic bias applied to the giant magnetostrictive element 11 can be made more uniform. Thereby, since the dispersion | variation in the expansion-contraction of the giant magnetostrictive element 11 can be suppressed, it becomes possible to acquire the outstanding optical characteristic.

  Next, a fourth embodiment of the present invention will be described.

  FIG. 9 is a diagram schematically showing the structure of a variable focal length lens 40 according to the fourth embodiment of the present invention, where (a) is a schematic plan view, and (b) is a DD line shown in (a). It is a schematic sectional drawing in alignment with.

  As shown in FIGS. 9A and 9B, in the variable focal length lens 40 according to the present embodiment, the permanent magnets 13 are integrally disposed on the radially outer side of the giant magnetostrictive element 11 and on both the upper and lower sides in the axial direction. This is different from the variable focal length lens 10 according to the first embodiment. That is, the permanent magnet 13 having a U-shaped cross section on one side is used. Others are the same as those of the variable focal length lens 10 according to the first embodiment. Therefore, the same reference numerals are given to the same elements, and duplicate descriptions are omitted. In the present embodiment, the end portion 13a of one portion positioned in the axial direction (upper side in FIG. 9B) is, for example, the N pole, and the other portion positioned in the axial direction (lower side in FIG. 9B). The end portion 13b is, for example, an S pole.

  In the present embodiment, since the permanent magnets 13 are arranged on the radially outer side of the giant magnetostrictive element 11 and on both the upper and lower sides in the axial direction, the magnetic bias applied to the giant magnetostrictive element 11 compared to the first to third embodiments. Can be made stronger and more uniform.

  Next, a fifth embodiment of the present invention will be described.

  10A and 10B are diagrams schematically showing the structure of a variable focal length lens 50 according to the fifth embodiment of the present invention, in which FIG. 10A is a schematic plan view, and FIG. 10B is a line EE shown in FIG. It is a schematic sectional drawing in alignment with.

  As shown in FIGS. 10A and 10B, the variable focal length lens 50 according to the present embodiment is different from the variable focal length lens 10 according to the first embodiment in that the permanent magnet 13 is omitted. . Others are the same as those of the variable focal length lens 10 according to the first embodiment. Therefore, the same reference numerals are given to the same elements, and duplicate descriptions are omitted.

  In the present embodiment, a predetermined DC bias current is passed through the coil 12 by the drive circuit shown in FIG. 3 or FIG. 4, and a magnetic field generated by the DC bias current is applied to the giant magnetostrictive element 11 as a “magnetic bias”. is doing. For this reason, in the present embodiment, a permanent magnet for applying a magnetic bias to the giant magnetostrictive element 11 is not required, and therefore the size of the focal length variable lens 50 can be greatly reduced.

  Next, a sixth embodiment of the present invention will be described.

  FIG. 11 is a schematic cross-sectional view schematically showing the structure of the focal length variable lens 60 according to the sixth embodiment of the present invention. Since the plan view is the same as FIG.

  As shown in FIG. 11, the variable focal length lens 60 according to the present embodiment is a variable focal length lens according to the first embodiment in that a U-shaped recess 11 d is provided in the inner wall portion of the giant magnetostrictive element 11. 10 and different. Others are the same as those of the variable focal length lens 10 according to the first embodiment. Therefore, the same reference numerals are given to the same elements, and duplicate descriptions are omitted.

  In the present embodiment, the volume of the hollow portion 11 c of the giant magnetostrictive element 11 is increased by the recess 11 d provided in the inner wall portion of the magnetostrictive element 11. As a result, the deformable regions of the first and second sealing members 14a and 14b are less than the inner diameter of the giant magnetostrictive element 11 in the portion where the recess 11d is provided. The amount of deformation of the first and second sealing members 14a and 14b according to the displacement of the magnetostrictive element 11 becomes larger. Therefore, according to this embodiment, the variable range of the focal length can be further expanded.

  Next, a seventh embodiment of the present invention will be described.

  FIG. 12 is a schematic cross-sectional view schematically showing the structure of the focal length variable lens 70 according to the seventh embodiment of the present invention. The plan view is omitted because it is substantially the same as FIG.

  As shown in FIG. 12, in the variable focal length lens 70 according to the present embodiment, the first sealing member 14a is sandwiched between two fixing members 71 and 72, and the second sealing member 14b is two fixing members 73. , 74 is different from the focal length variable lens 10 according to the first embodiment in that it has a structure sandwiched between them. Others are the same as those of the variable focal length lens 10 according to the first embodiment. Therefore, the same reference numerals are given to the same elements, and duplicate descriptions are omitted.

  All of these fixing members 71 to 74 have a donut plate shape, and the inner diameter thereof is set to be smaller than the inner diameter of the giant magnetostrictive element 11. For this reason, the deformable region of the first sealing member 14 a sandwiched between the fixing members 71 and 72 is limited to the diameter of the opening 75, and similarly, the second sealing member sandwiched between the fixing members 73 and 74. The deformable region of the member 14 b is limited to the diameter of the opening 76. For this reason, the amount of deformation of the first and second sealing members 14a and 14b according to the displacement of the giant magnetostrictive element 11 becomes very large, and as a result, the variable range of the focal length can be further enlarged. Become.

  The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

  For example, in each of the above embodiments, the entire giant magnetostrictive element 11 is composed of a giant magnetostrictive material. However, in the present invention, it is not essential that the entire giant magnetostrictive element 11 is composed of a giant magnetostrictive material. Only a part of 11 may be made of a giant magnetostrictive material. Therefore, as shown in FIGS. 13A to 13C, a portion 81 made of a giant magnetostrictive material and a portion 82 made of a material different from the giant magnetostrictive material may be mixed in the axial direction. As shown in (a) to (c), a portion 81 made of a giant magnetostrictive material and a portion 82 made of a material different from the giant magnetostrictive material may be mixed in the radial direction. As shown in (b), a portion 81 made of a giant magnetostrictive material and a portion 82 made of a material different from the giant magnetostrictive material may be mixed in the circumferential direction. However, if the entire giant magnetostrictive element 11 is made of a giant magnetostrictive material as in the above embodiments, a larger displacement can be obtained and a correct lens shape can be obtained. The entire magnetostrictive element 11 is preferably made of a giant magnetostrictive material.

  In each of the above embodiments, the coil 12 is disposed radially outside the giant magnetostrictive element 11. However, the coil 12 may be disposed radially inside the giant magnetostrictive element 11. It is also possible to arrange in the axial direction with respect to the element 11.

  Further, in each of the above embodiments, a magnetic bias is applied to the giant magnetostrictive element 11 using the permanent magnet 13 or the like. However, in the present invention, it is not essential to apply a magnetic bias to the giant magnetostrictive element 11, and this is omitted. It doesn't matter.

  Moreover, in the said embodiment, in the neutral state in which only the magnetic bias is applied to the giant magnetostrictive element 11, the surface of the first and second sealing members 14a, 14b is substantially flat. Although described (see FIG. 1B), the shape of the sealing members 14a and 14b in the neutral state may be any shape. That is, the curvature may be changed by having the shape as a convex lens in the neutral state of the sealing members 14a and 14b, and extending and contracting the giant magnetostrictive element within the range of the shape as the convex lens. Further, the sealing members 14a and 14b may have a concave lens shape in a neutral state, and the curvature may be changed by extending and contracting the giant magnetostrictive element within the range of the concave lens shape.

  In each of the above embodiments, the case where a giant magnetostrictive element is used has been described. However, a magnetostrictive element may be used as long as it can be displaced to such an extent that the sealing member can be deformed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematically the structure of the focal distance variable lens 10 by the 1st Embodiment of this invention, (a) is a schematic plan view, (b) is the schematic along the AA line shown to (a). It is sectional drawing. 2 is a schematic exploded perspective view of a variable focal length lens 10. FIG. 2 is a circuit diagram illustrating an example of a drive circuit that drives a variable focal length lens. FIG. FIG. 6 is a circuit diagram illustrating another example of a drive circuit that drives the variable focal length lens 10. 2 is a schematic cross-sectional view showing a state in which a giant magnetostrictive element 11 is extended in the axial direction. FIG. 2 is a schematic cross-sectional view showing a state in which a giant magnetostrictive element 11 is contracted in the axial direction. FIG. It is a figure which shows roughly the structure of the focal distance variable lens 20 by the 2nd Embodiment of this invention, (a) is a schematic plan view, (b) is the schematic along the BB line shown to (a). It is sectional drawing. It is a figure which shows roughly the structure of the focal distance variable lens 30 by the 3rd Embodiment of this invention, (a) is a schematic plan view, (b) is the schematic along the CC line | wire shown to (a). It is sectional drawing. It is a figure which shows roughly the structure of the focal distance variable lens 40 by the 4th Embodiment of this invention, (a) is a schematic plan view, (b) is the schematic along the DD line shown to (a). It is sectional drawing. It is a figure which shows roughly the structure of the focal distance variable lens 50 by the 5th Embodiment of this invention, (a) is a schematic plan view, (b) is the schematic along the EE line shown to (a). It is sectional drawing. It is a schematic sectional drawing which shows roughly the structure of the focal distance variable lens 60 by the 6th Embodiment of this invention. It is a schematic sectional drawing which shows roughly the structure of the focal distance variable lens 70 by the 7th Embodiment of this invention. It is a schematic perspective view showing the structure of the giant magnetostrictive element 11 in which a portion 81 made of a giant magnetostrictive material and a portion 82 made of a material different from the giant magnetostrictive material are mixed in the axial direction. It is a schematic perspective view showing the structure of the giant magnetostrictive element 11 in which a portion 81 made of a giant magnetostrictive material and a portion 82 made of a material different from the giant magnetostrictive material are mixed in the radial direction. It is a schematic perspective view showing the structure of the giant magnetostrictive element 11 in which a portion 81 made of a giant magnetostrictive material and a portion 82 made of a material different from the giant magnetostrictive material are mixed in the circumferential direction.

Explanation of symbols

10, 20, 30, 40, 50, 60, 70 Focal length variable lens 11 Giant magnetostrictive element 11a, 11b End face 11c of giant magnetostrictive element Hollow part 12 of giant magnetostrictive element 12 Coil 12a Hollow part of coil 13 Permanent magnet 13a Permanent magnet 13a One pole 13b Permanent magnet other pole 13c Permanent magnet hollow portion 14a First sealing member 14b Second sealing member 15 Fluid 16 DC power supply 17 Variable resistance 18 Variable DC power supply 19 Resistance 71-74 Fixing member 75,76 Fixed member opening 81 Portion made of giant magnetostrictive material 82 Portion made of a material different from giant magnetostrictive material

Claims (9)

  A cylindrical magnetostrictive element having at least a part made of a magnetostrictive material and having a hollow part as an optical path, a sealing member at least partly disposed on the optical path, and the hollow part of the magnetostrictive element by the sealing member And a means for displacing the magnetostrictive element at least in an axial direction by applying a magnetic field, and at least a part of the portion of the sealing member disposed on the optical path is formed of the magnetostrictive element. A variable focal length lens having elasticity that can be deformed in accordance with the displacement in the axial direction.   The focal length variable lens according to claim 1, wherein the whole magnetostrictive element is made of a magnetostrictive material.   3. The variable focal length lens according to claim 1, wherein the means for displacing includes a coil wound in a circumferential direction of the magnetostrictive element.   4. The variable focal length lens according to claim 1, further comprising a magnetic bias applying unit that applies a magnetic bias to the magnetostrictive element. 5.   The focal length variable lens according to claim 4, wherein the magnetic bias applying unit includes a permanent magnet.   The variable focal length lens according to claim 4, wherein the magnetic bias applying unit includes a circuit that applies a DC bias current to the coil.   The focal length variable lens according to claim 1, wherein the sealing member has a deformable region set to be less than an inner diameter of at least a part of the magnetostrictive element.   The focal length variable lens according to claim 7, wherein a recess is provided in an inner wall portion of the magnetostrictive element.   The focal length variable lens according to claim 7, further comprising a fixing member that limits a deformable region of the sealing member.

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