JP2009294330A - Variable focus lens, method for driving the same, and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variation corresponding to a change in a desired focal distance by suppressing the unnecessary deformation of a variable focus lens. <P>SOLUTION: The variable focus lens has a lens part 20 whose focal distance is changed by the shape change of a light transmission surface and a drive part 80 applying external force for changing the shape of the lens part 20. The drive part 80 has a piezoelectric element 55, a presser 36 and a leaf spring 34. The presser 36 is pressed by the displacement of the piezoelectric element 55, to deform the leaf spring 34. External force applying members (projections 41e and 41f) provided in the support member 41 of the piezoelectric element 55 are displaced by the deformation of the leaf spring 34, to press the diaphragm 9 of the lens part 20. The displacement amount of the piezoelectric element 55 is amplified to apply force for deforming a deformed membrane 2 of the lens part 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a so-called pressure-type variable focus lens whose focal length changes due to deformation of an elastic film, a driving method thereof, and an imaging apparatus.

  Various variable focus lenses that change the focal length by inserting a liquid between transparent members have been proposed. This variable focus lens can change the focal length without providing a drive mechanism for moving the lens itself, so in various optical devices such as a microscope, an imaging device, and an information recording / reproducing device having a focal length adjustment function, It is attracting attention as a means for realizing the miniaturization of the above. The variable focus lens includes an electrowetting type in which two types of liquid are inserted between transparent members, and the liquid interface is deformed by applying an electrowetting phenomenon by applying a voltage, and a transparent member, a thin plate, an elastic film, etc. The liquid is roughly divided into a pressure type that deforms a thin film or an elastic film by inserting a pressure between the deformed portion and applying pressure to the liquid.

As a pressure-type variable focus lens, there are proposed a configuration in which the deformation portion is deformed by changing the amount of liquid inside the lens, and a method in which the deformation portion is deformed by changing the shape of the container for storing the liquid. . As a method of changing the shape of the container, when a piezoelectric element is used for the drive unit, a high-speed response is possible, which is suitable for an imaging device or the like that requires response characteristics (see Patent Document 1).
JP 2000-81504 A

  In the variable focus lens disclosed in Patent Document 1, the shape of the deformed portion is changed using a ring-shaped and flat-plate piezoelectric bimorph. In this case, the response characteristic is relatively fast, but there is a drawback that the generated force is relatively weak. For this reason, in order to obtain a sufficient amount of deformation even with a small force, it is necessary to relatively weaken the tension of the deformed portion. That is, the tension of the deformed portion cannot be increased.

  However, when the tension of the deformed part is weak, depending on the arrangement of the variable focus lens, the center of the film may shift from the light transmission center due to the weight downward, so-called self-weight sagging may occur, and other unnecessary. There is a risk of deformation. That is, when driven by a piezoelectric bimorph, the film cannot be formed with a certain degree of tension, and thus there is a problem that it is difficult to ensure the long-term durability of the lens and it is difficult to increase the size.

  In contrast, when a laminated piezoelectric element is used, it is possible to generate a relatively large force, but since the amount of displacement is small, it is not possible to cause deformation of the deformable portion sufficient to change the focal length. There is an inconvenience.

  In view of the above problems, an object of the present invention is to suppress unnecessary deformation of a variable focus lens and to change the focal length of the variable focus lens with a sufficient amount of change.

  In order to solve the above-described problem, a variable focus lens according to the present invention includes a lens unit whose focal length changes due to a change in shape of a light transmission surface, and a drive unit. The drive unit is arranged in the displacement direction of the piezoelectric element, a plate spring whose one end is fixed to the piezoelectric element, and is fixed to the other end of the plate spring, and is pressed by the displacement of the piezoelectric element. And a pressing element for deforming the spring. Furthermore, it is set as the structure which has an external force provision member fixed to a leaf | plate spring and giving an external force to a lens part.

  Also, the variable focus lens driving method according to the present invention deforms the elastic member by the displacement of the laminated piezoelectric element, amplifies the deformation amount of the elastic member, and has a liquid between the light-transmitting substrate and the deforming portion. The external force which deform | transforms the deformation | transformation part of a variable focus lens is provided.

  An image pickup apparatus according to the present invention includes an image pickup element, a signal processing unit that inputs an image signal photoelectrically converted by the image pickup element and performs signal processing, and an image pickup lens system including the above-described variable focus lens according to the present invention. It is set as the structure which has.

  According to the present invention, as described above, as a drive unit that applies an external force that changes the shape of the lens unit of the varifocal lens, the piezoelectric element, a leaf spring whose one end is fixed to the piezoelectric element, and the other end of the leaf spring are provided. A pressing element that is fixed and is pressed by the displacement of the piezoelectric element to deform the leaf spring is provided. Further, an external force applying member that is fixed to the leaf spring and applies an external force to the lens unit is provided. With this configuration, the displacement amount of the piezoelectric element can be amplified via the leaf spring.

  Therefore, for example, by using a laminated piezoelectric element as the piezoelectric element, it is possible to add the amplified displacement amount as an external force with a relatively strong force. The external force that changes the shape of the lens portion becomes relatively strong, and the occurrence of unnecessary deformation of the deformation portion can be suppressed. Further, in this case, since the amount of displacement increases, the focal length of the variable focus lens can be changed with a sufficient amount of change.

  According to the present invention, it is possible to suppress the occurrence of unnecessary deformation of the lens and change the focal length of the variable focus lens with a sufficient amount of change.

  Examples of the best mode for carrying out the present invention will be described below. The embodiment described below is a preferred specific example of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these forms.

  First, with reference to FIGS. 1-6, an example of the lens part in the variable focus lens which concerns on embodiment of this invention is demonstrated. FIG. 1 is a schematic perspective configuration diagram in which a part of the lens unit 20 is cut away. As shown in FIG. 1, in this lens portion 20, a liquid 3 is sealed between a substrate 1 made of a light transmitting material such as optical glass or PC (polycarbonate) and a deformed portion 2 made of an elastic film such as an elastomer. Thus, it is configured as a pressure type liquid lens. As the liquid 3, for example, a light transmissive liquid such as silicone oil can be used. The substrate 1, the deformable portion 2, and the liquid 3 are made of a material having a desired transmittance with respect to the wavelength band of light used as a lens. Although the example of illustration shows the case where the board | substrate 1 is flat form, the lens shape which has a predetermined curvature may be sufficient. The deformation unit 2 may be a thin plate such as glass as long as it can secure a necessary deformation amount according to the application of the variable focus lens.

  In this example, the substrate 1 having a substantially circular plane is fixed to the ring-shaped frame 4 by bonding or the like. The frame 4 is made of aluminum or the like. The inner side surface 4a of the frame body 4 is a cylindrical surface having an inner diameter substantially the same as the outer diameter of the substrate 1, for example. Further, in this example, the outer surface 4b of the frame body 4 is provided with a screw groove to be attached to the frame body of the drive unit described later. A step 4c leading to the inner surface 4a side is provided on the deformed portion 2 side of one surface of the frame body 4, and a hole portion 4e penetrating vertically is provided on the inner surface 4d. In this example, the holes 4e are provided at substantially equal intervals on the annular surface 4d, and the liquid 3 can be moved up and down through the holes 4e. In the illustrated example, four holes 4e are provided, but the number is not limited to this number. Further, another step 4f is provided on the outer diameter side following the step 4c, and the fixing portions 5 and 6 sandwiching the deformed portion 2 are fitted into the step 4f. The deformable portion 2 is fixed with a peripheral portion sandwiched between flat ring-shaped fixing portions 5 and 6, and is fixed together with the fixing portions 5 and 6 to the step 4 c of the frame body 4 by screws 7.

  On the other hand, for example, a ring-shaped recess 4g is provided on the surface of the frame 4 opposite to the deformed portion 2. A diaphragm 9 made of an elastic body and similarly ring-shaped is fixed to the surface of the frame body 4 opposite to the deformed portion 2 by adhesion or the like so as to cover the recess 4g. Then, the liquid 3 is sealed between the diaphragm 9 and the recess 4 g of the frame body 4, in the hole 4 e of the frame body 4, and further in a space surrounded by the step 4 c, the deformed portion 2, and the substrate 1. Further, a pressing member 10 made of aluminum or the like, for example, in a flat ring shape, is provided outside the diaphragm 9.

  By adopting such a configuration, a uniform force is applied to the ring-shaped pressing member 10 from the outside, so that the diaphragm 9 is recessed inward and pressure is applied to the liquid 3 inside. And the liquid 3 which flowed into the inner side part from the hole 4e of the frame body 4 can be made to deform | transform so that the deformation | transformation part 2 may protrude more toward an outer side by giving a pressure to the deformation | transformation part 2. FIG.

  FIG. 2 is a cross-sectional view taken along line AA in FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. As shown in FIG. 2, an O-ring 8 is interposed between the fixed portion 6 for fixing the deformable portion 2 and the surface 4d on the deformable portion 2 side of the frame body 4 in order to keep the liquid 3 liquid-tight. Also good. Although not shown, the fixing portions 5 and 6 for fixing the deformation portion 2 are screwed to the outside of the O-ring 8. By applying a force to the pressing member 10 on the diaphragm 9 side as shown by an arrow a, the liquid 3 inside is pushed upward in FIG. 2 so that the deformed portion 2 protrudes outside as shown by an arrow b. Deform. At this time, since the pressure is equally applied to the deformable portion 2 by the liquid 3, the spherical shape of the deformable portion 2 is maintained with high accuracy.

  FIG. 3 is a perspective configuration diagram in which a part of the deformable portion 2 and the fixing portions 5 and 6 are cut out. FIG. 4 shows a cross-sectional configuration diagram thereof. As shown in FIG. 3, the deformable portion 2 is fixed by fitting the screws into the screw holes 12 formed in the fixing portions 5 and 6 with the outer peripheral edge portions sandwiched between the fixing portions 5 and 6. It is desirable to provide the same number of screw holes 12 at regular intervals. And by pressing the diaphragm 9 equally by the pressing member 10 demonstrated in FIG.1 and FIG.2, as shown with a broken line in FIG. 4, the deformation | transformation part 2 can be deform | transformed maintaining a precise spherical shape.

  FIG. 5 is a perspective configuration diagram of the lens unit 20 described with reference to FIGS. A ring-shaped cover portion 13 is fixed to the surface of the frame body 4 on the deformation portion 2 side with screws 14 so as to cover the frame body 4 that fixes the deformation portion 2. A step 13a that is recessed toward the deformed portion 2 is provided at the center side of the cover portion 13, and a circular hole portion 13b is provided at the center portion. The light passage is restricted by the hole 13b.

  FIG. 6 is a perspective configuration diagram of the rear surface side of the lens unit 20 described in FIG. A ring-shaped pressing member 10 is disposed on a diaphragm (not shown) of the frame 4, and the substrate 1 is exposed at the center of the frame 4.

  Next, an example of the drive unit of the variable focus lens according to the embodiment of the present invention will be described with reference to FIGS. 7 is a perspective configuration diagram of an example of the drive unit 80, FIG. 8 is an exploded perspective configuration diagram of the leaf spring portion 30 of the drive unit 80, FIG. 9 is a perspective configuration diagram of the frame 60 of the drive unit 80, and FIG. 3 is an exploded perspective configuration diagram of an element unit 40. FIG.

  As shown in FIG. 7, the drive unit 80 in this example is configured by fixing a plate spring unit 30 and a piezoelectric element unit 40 to a ring-shaped frame body 60. As shown in FIGS. 7 and 8, the leaf spring portion 30 includes a pressing member 31, pressing members 32 and 33, a leaf spring 34, a fixing member 35, and pressing elements 36 (36 a and 36 b). The fixing member 35 has an elongated rectangular parallelepiped shape, and has a shape in which a concave portion 35a is provided at the center in the longitudinal direction of one surface. The recess 35a is provided so as to penetrate between the opposing side surfaces 35e and 35f, and a part of the leaf spring 34, in the illustrated example, approximately half is fitted to the bottom surface of the recess 35a.

  Also, cylindrical pressing elements 36a and 36b are fitted to one of the side surfaces 35e through which the concave portion 35a of the fixing member 35 penetrates, respectively, to the column portions 35c and 35d at both ends divided by the concave portion 35a. It is fixed by bonding or the like. In this example, the pressing element 36 has a pin shape whose diameter is extremely small with respect to the length in the longitudinal direction, and the longitudinal direction is selected in a direction substantially along the plate surface of the leaf spring 34 fitted to the bottom surface of the recess 35a. Is done. Screw holes 35h are provided on the upper surfaces of the column portions 35c and 35d, and the screws 52a and 52b are screwed together. In addition, on the side surface 35f opposite to the side surface 35e into which the pressing member 36 of the fixing member 35 is fitted, notches 35g are provided at both ends in the longitudinal direction. By forming the notch 35g by selecting an inclination angle or the like so as to be along an outer cylindrical surface of a ring-shaped frame body 60 which will be described later, it does not protrude outside the frame body 60 when attached to the frame body 60. It becomes a shape.

  The leaf springs 34 have a planar rectangular shape, and in the illustrated example, two screw holes 34h1 and 34h2 are provided along the long side. The three screw holes 34h1 in one row are formed so as to overlap with the three screw holes 35ah provided in the recess 35a of the fixing member 35.

  Two pressing members 32 and 33 are placed on the leaf spring 34. Each of the holding members 32 and 33 is a flat plate having a rectangular shape, and its long side is substantially the same as the long side of the leaf spring 34, and the short side is slightly shorter than half the short side of the leaf spring 34. . In addition, screw holes 32h and 33h corresponding to the two rows of screw holes 34h1 and 34h2 provided in the leaf spring 34 are provided along the long sides. By screwing three screws 51 into the screw holes 34h1 in one row of the plate springs 34 from the screw holes 32h of the holding member 32 and further into the screw holes 35ah of the concave portions 35a of the fixing member 35, the plate springs 34 are moved in the short side direction. A half region to be separated is fixed to the fixing member 35. Thereby, the half region of the leaf spring 34 in this case is also fixed to the pressing element 36 fitted to the fixing member 35.

  On the other pressing member 33 is placed a pressing member 31 that transmits a force generated by displacement of a piezoelectric element 55 of the piezoelectric element section 40 described later to the pressing element 36. The pressing member 35 is formed in an elongated rectangular parallelepiped shape, and a concave portion 31a for fitting the pressing member 33 and the leaf spring 34 is provided in the longitudinal center portion of one side surface, and both ends thereof are column portions 31c and 31d. The recess 31a is provided so as to penetrate between the opposing side surfaces 31e and 31f. The side surfaces 31e and 31f are flat surfaces, the side surface 31e is in contact with an end surface orthogonal to the displacement direction of the piezoelectric element 55 described later, and the side surface 31f is in contact with the cylindrical surface of the above-described pressing element 36. Both end portions in the longitudinal direction of the side surface 31f are notched portions 31g like the fixing member 35, and have a shape along the inner cylindrical surface of the frame body 60 described later. The notch 31e is suitable to avoid contact with the frame 60 when the leaf spring 34 is bent due to displacement of the piezoelectric element 55 described later and the pressing member 31 moves to the frame 60 side. It is desirable to provide at an angle. A screw hole 31 h is provided on the upper surface of the pressing member 31.

  Then, the pressing member 31 is placed so as to cover a half region not fixed to the fixing member 35 of the plate spring 34 from above the pressing member 33, and the screw hole 31 h, the screw hole 33 h of the pressing member 33, and the plate spring By passing three screws (not shown) through the screw holes 34h2 of the 34 and screwing into screw holes provided in the frame body 60 of the piezoelectric element portion 40 described later, the pressing member 31, the pressing member 33, and the plate A half region of the spring 34 is fixed. At this time, the long sides of the pressing members 32 and 33 are arranged substantially parallel to each other, and are arranged and fixed in parallel in the long side direction of the leaf spring 34 with a slight gap. With such a configuration, the direction in which the leaf spring 34 that receives deformation stress is bent and deformed can be regulated in one direction by the gap between the pressing members 32 and 33.

  Next, the frame 60 will be described with reference to FIGS. 7 and 9. In this example, the frame body 60 has a ring shape, and a thread groove 60s is provided on the inner surface thereof. The thread groove 60s is formed with a depth and a pitch to be screwed into the thread groove 4b provided on the outer peripheral surface of the frame body 4 of the lens unit 20 described with reference to FIG. At one end of the frame body 60, a fixing portion 60a for fixing the fixing member 35 described in FIG. The outer peripheral surface of the fixing portion 60a extends along the outer periphery of the ring-shaped frame 60, and the inner surface is planar. In the illustrated example, two screw holes 60h penetrating from the outer peripheral surface to the inner surface are provided. Screw holes (not shown) that overlap these screw holes 60 h are provided on the side surface 35 f opposite to the side surface 35 e on which the pressing member 36 of the fixing member 35 shown in FIG. 8 is provided, and the fixing member 35 is attached to the frame body 60. It is fixed to the fixing portion 60a by screws.

  As shown in FIGS. 7 and 10, the piezoelectric element portion 40 is provided with a circular hole portion 41 i in the center portion of the substantially flat support member 41, and a pair of rectangular parallelepiped shapes at the step portions 41 a and 41 b at both ends thereof. The piezoelectric element 55 (55a and 55b) is mounted and configured. The step portions 41a and 41b are shaped to cover the three surfaces of the piezoelectric element 55, and fixed ends 55c and 55d, which are one end surfaces orthogonal to the displacement direction of the piezoelectric element 55, and one side surface (not shown). It is fixed to the side surfaces of the step portions 41a and 41b by bonding or the like. The other ends of the fixed ends 55c and 55d are end surfaces 55e and 55f that are in contact with the pressing member 31. For example, linear protrusions 41e and 41f are provided on the back side of the bottom surfaces of the step portions 41a and 41b of the support member 41. On the other hand, at one end of the support member 41, a step-shaped fixing portion 41c extending in a flat plate shape is provided outside in a region between the step portions 41a and 41b. The fixing portion 41c is provided with a screw hole 41h at a position overlapping the screw hole 34h2 of the leaf spring 34 described in FIG.

  As described above, the three screw holes 31h of the pressing member 31 shown in FIG. 8, the screw holes 33h of the pressing member 33, the screw holes 34h2 of the leaf spring 34, and the screw holes 41h of the support member 41 are penetrated. Screw (not shown). By fixing in this way, the pressing member 31, one end of the leaf spring 34, and the support member 41 are fixed. One end of the leaf spring 34 and the piezoelectric elements 55 a and 55 b are fixed via the support member 41. The protrusions 41e and 41f described above are provided as external force applying members that apply external force to the lens unit 20 by deformation of the plate spring 34 described later, and are fixed to the plate spring 34.

  Further, a pair of screw holes 41hs is provided on the upper surface of the support member 41 in the vicinity of the fixed ends 55c and 55d of the piezoelectric element 55, and the screws 53a and 53b are screwed together. As shown in FIG. 7, the elastic members 54 a and 54 b made of coils are engaged between the screws 53 a and 53 b and the screws 52 a and 52 b that are screwed onto the upper surface of the fixing member 35. Thereby, the end surfaces 55e and 55f on the pressing member 31 side of the piezoelectric elements 55a and 55b are brought into contact with one side surface 31e of the pressing member 31, and the other side surface 31f of the pressing member 31 and the pressing elements 36a and 36b are brought into contact with each other. Abutted. Therefore, the force generated by the displacement of the piezoelectric elements 55 a and 55 b can be reliably applied to the pressing element 36 via the pressing member 31.

  In the present embodiment, it is desirable to use a multilayer piezoelectric element as the piezoelectric element 55. A multilayer piezoelectric element having a known structure can be used. That is, tens to hundreds of thin plates made of a piezoelectric material such as piezoelectric ceramics are stacked, and the layers are alternately stacked so that the polarization in the thickness direction is reversed one by one. As for the lead-out of the electrodes, + and − of polarization are connected in parallel. By adopting such a configuration, the direction of polarization of all piezoelectric ceramics becomes the same as the direction of applied voltage, and is displaced in the stacking direction by the piezoelectric longitudinal effect. In this case, the voltage can be reduced by reducing the thickness of one sheet, and the total displacement can be increased by increasing the number of stacked layers.

Piezoelectric ceramics (polycrystal) such as barium titanate (BaTiO ₃ ) and lead zirconate titanate (PZT: Pb (Zi, Ti) O ₃ ) are used as the piezoelectric material constituting the piezoelectric element. it can. In FIGS. 7 and 10, wirings and connection terminals for applying a voltage to the piezoelectric elements 55a and 55b are omitted.

  FIG. 11 is a perspective configuration diagram viewed from the back side of the drive unit 80 having the above-described configuration. In FIG. 11, parts corresponding to those in FIG. As shown in FIG. 11, with the drive unit 80 assembled, the outer surface 4b of the frame 4 in the lens unit 20 shown in FIG. 5 is screwed into the screw groove 60s on the inner peripheral surface of the frame 60. With such a configuration, the lens unit 20 and the driving unit 80 are integrated, and the variable focus lens according to the present embodiment is configured. In this case, the protrusions 41e and 41f on the back surface of the support member 41 and the pressing member 10 shown in FIG. 1 are arranged so as to face each other with contact or a slight gap.

  Next, in this variable focus lens, a deformation mode of the leaf spring when a voltage is applied to the piezoelectric element to be displaced will be described with reference to FIGS. FIG. 12A is a side view showing a simplified positional relationship between the piezoelectric element 55 (55a or 55b), the pressing element 36 (36a or 36b), and the leaf spring 34. FIG. Although the pressing member 31 shown in FIGS. 7 and 8 is omitted in FIG. 12, the action of the force on the pressing element 36 with respect to the displacement of the piezoelectric element 55 is the same.

  First, FIG. 12A shows a non-operating state in which no voltage is applied to the piezoelectric element 55 (55a or 55b). As described above, when a laminated piezoelectric element is used as the piezoelectric element 55 and the lamination direction is the longitudinal direction, the direction displaced by voltage application is the longitudinal direction as indicated by the arrow m. The pressing element 36 is arranged in the longitudinal direction of the end face of the piezoelectric element 55, that is, in the displacement direction. As described above, the pressing element 36 has a pin shape in the present embodiment. The piezoelectric element 55 is fixed to the fixing member 35 so that the cylindrical surface of the pressing element 36 is in contact with a plane (in this case, the end surface itself) orthogonal to the direction in which the end surface of the piezoelectric element 55 is displaced.

  As described above, the plate spring 34 is a flat plate having a rectangular shape, and one end thereof, in this example, a substantially half region is fixed to the fixing member 35. Then, the other end of the leaf spring 34, in this example, the remaining half of the region is fixed to the support member 41 of the piezoelectric element 55 as described with reference to FIGS. Fixed. In this example, the leaf spring 34 is separated in the short side direction, and one is fixed to the fixing member 35 and the other is fixed to the piezoelectric element 55.

  The region fixed to the fixing member 35 of the leaf spring 34 and the region fixed to the piezoelectric element 55 via the support member 41 (not shown) are pressed by the pressing members 32 and 33, respectively. As described above, the pressing members 32 and 33 are arranged so that the long sides thereof are arranged substantially parallel to each other, and are arranged in parallel in the long side direction of the leaf spring 34 with a slight gap therebetween. . By adopting such a configuration, the direction in which the leaf spring 34 subjected to deformation stress undergoes bending deformation is perpendicular to the direction in which the gap between the pressing members 32 and 33 extends, in the illustrated example, on the paper surface of FIG. Regulated in the direction along.

  Further, the positional relationship between the pressing element 36 and the leaf spring 34 is also selected so that the leaf spring 34 is appropriately bent and deformed. In this example, the longitudinal direction of the pin-shaped pressing element 36 and the plate surface of the leaf spring 34 are parallel to each other, but are not on the same plane and are slightly shifted upward in FIG. Select the arrangement.

  As such an arrangement, a predetermined voltage is applied to the piezoelectric element 55 by a voltage application mechanism (not shown), and the piezoelectric element 55 is displaced in the stacking direction indicated by the arrow m. This state is shown in FIG. Due to the displacement of the end face of the piezoelectric element 55, the pressing element 36 is pressed by the end face of the piezoelectric element 55 (or the end face 31f of the pressing member 31 shown in FIG. 8). As described above, since the pressing element 36 is disposed at a position shifted upward with respect to the plate surface of the plate spring 34, the force f1 applied to the pressing element 36 is a region on the fixing member 35 side with respect to the plate spring 34. Acts as a downward force f2. For this reason, the fixing member 35 and the piezoelectric element 55 are displaced relative to each other, and as shown in FIG.

  FIG. 12B shows a state in which the position of the piezoelectric element 55 is fixed, while FIG. 12C shows a state in which the position of the fixing member 35 is fixed. As shown in FIG. 12 (c), in this case, the end face (fixed ends 55c and 55d shown in FIG. 10) opposite to the end face on the pressing element 36 side of the piezoelectric element 55 moves downward to the lens section 20. The position of the protrusion 41e (41f) that becomes the external force applying member also moves downward. At this time, the displacement l2 of the protrusion 41e (41f) is greatly amplified with respect to the displacement l1 of the piezoelectric element 55 in the stacking direction. The amplification factor of the displacement amount l2 with respect to the displacement amount l1 is the positional relationship between the pressing element 36 and the leaf spring 34, the amount of bending (elastic coefficient) of the leaf spring 34, and the protrusion 41e (41f) serving as the bending position and force point of the leaf spring 34 ) Can be selected as appropriate.

In the case of the configuration of this example, it is confirmed that the displacement amount l2 of the protrusion 41e (41f), which is an external force applying member, can be amplified approximately 30 times with respect to the displacement amount l1 of the piezoelectric element 55 under the following conditions. did.
Piezoelectric element: PZT with a length of 5 mm in the stacking direction
Leaf spring: Long side x short side 18mm x 8.5mm, thickness 0.15mm (SUS304CSP)
Presser: Pin-shaped member with a diameter of 1 mm Placement of leaf spring and pusher: Placement of a pusher at a position 0.8 mm from the plate surface of the leaf spring Length from the bent position of the leaf spring to the protrusion: about 16 mm
In this example, a voltage of 150 V was applied to the piezoelectric element 55 to generate a displacement of 10 μm in the stacking direction, and the displacements of the protrusions 41e and 41f could be 300 μm.

  Further, in this example, when the deformable portion 2 of the lens portion 20 is fixed as a tension that does not cause the self-weight sag even when the substrate 1 is arranged along the vertical direction, the force due to the displacement of the piezoelectric element 55 is not generated. It was confirmed that it was strong enough and sufficient displacement could be realized. Here, the tension of the deformed portion 2 was set to such a degree that the coma aberration was 0.1 λrms (λ = 632 nm). The displacement amount of the deforming part will be described later.

  In this embodiment, an example in which a pin-shaped member is used as the pressing member 36 is shown. However, the region contacting the end surface of the pressing member 31 of the pressing member 36 is not a dot but a line or a plane. Thus, deformation such as a depression of the pressing member 31 can be suppressed. That is, when the pressing element 36 has a pin shape, that is, a cylindrical shape in this way, it is possible to avoid the concentration of unnecessary force in the contact area and to suppress the deformation of this portion. Fluctuations can be suppressed. Accordingly, it is desirable that the pressing element 36 has a rod shape such as a pin shape, for example, a cylindrical shape or a shape equivalent thereto, so that the contact area is linear or planar.

Next, the results of studying the aberration characteristics, the hysteresis characteristics of the deformed portion, and the response characteristics of the variable focus lens according to the present embodiment will be described.
FIG. 13 shows the result of measuring the spherical aberration by configuring the lens unit 20 shown in FIG. 1 by changing the material of the deforming unit 2. In this example, measurement was performed using light having a wavelength of 633 nm and an aperture diameter of 8 mm. The materials of the solid lines a1 to a7 are as follows.

a1: Spherical glass a2: Silicone A (Shin-Etsu Chemical Co., Ltd., trade name KE1935)
a3: Silicone B
a4: Silicone C
a5: Urethane a6: Styrenic elastomer a7: Resin (PC)

  From the results of FIG. 13, it can be said that it is desirable to use silicone A because the spherical aberration of silicone A is closest to that of spherical glass. It can be seen that the other materials are relatively shifted in spherical aberration from the spherical glass. From this result, it is understood that spherical aberration can be sufficiently suppressed practically in the pressure type variable focus lens by appropriately selecting the material of the deformed portion.

  Next, the hysteresis characteristic when the above-described silicone A was used as the deformed portion 2 was examined. The number of samples is 2, and the results are shown in FIGS. In this example, when the drive voltage for the piezoelectric elements 55a and 55b was changed from 0V to 150V and subsequently changed from 150V to 0V, the displacement of the tip of the deformed portion 2 was measured. 14 and 15, solid lines b1 and c1 indicate changes when the voltage is increased, and solid lines b2 and c2 indicate changes when the voltage is decreased. In each example, it can be seen that there is almost no difference between when the voltage is increased and when the voltage is decreased, and that good hysteresis characteristics can be maintained. At this time, it can be seen that a displacement of 400 μm can be realized with respect to a voltage value of 150V.

  Further, the response characteristic of the tip end displacement amount of the deformed portion with respect to the frequency of the driving voltage was measured. Also in this case, the above-mentioned silicone A was used as the deformed portion 2 and the number of samples was set to 2. The respective results are shown in FIGS. In FIGS. 16 and 17, solid lines d1 and e1 indicate gains that output the deformation portion tip displacement with respect to frequency, that is, transfer functions. Solid lines d2 and e2 indicate the phase characteristics with respect to the frequency. From the results of FIGS. 16 and 17, it can be seen that a substantially constant output is obtained up to a frequency of about 50 Hz, and the phase is hardly delayed. It can also be seen that there is a resonance point at about 200 Hz. From this result, it can be seen that the variable focus lens according to the present embodiment can obtain a constant response characteristic up to a sufficiently high frequency, and can be used in an imaging lens system or the like and can achieve a sufficiently high speed response in practice.

  Step response characteristics were also measured. Also in this measurement, the above-described silicone A was used as the deformed portion 2, and the number of samples was set to two. The respective results are shown in FIGS. 18 and 19, solid lines f1 and g1 indicate drive voltages for the piezoelectric elements 55a and 55b, respectively, and solid lines f2 and g2 indicate the tip displacement of the deformable portion 2, respectively. It can be seen that a step response characteristic of about 20 ms can be obtained with respect to a change in driving voltage. Therefore, for example, it can be seen that the present invention can be practically used as a variable focus lens of an imaging apparatus.

  Next, an imaging apparatus in which the variable focus lens according to the embodiment of the present invention described in FIGS. 1 to 11 is used in an imaging optical system will be described with reference to FIGS. FIG. 20 shows a schematic configuration of the external appearance of the imaging apparatus 100. For example, a digital video camera is taken as an example.

An imaging apparatus 100 illustrated in FIG. 20 is configured by including an imaging optical system, an imaging element, a drive control circuit, and the like inside a hollow exterior case 102.
First, the exterior case 102 of the imaging device 100 is a hollow casing that is a horizontally long, substantially rectangular parallelepiped, and is used in a state where the longitudinal direction is the front-rear direction. Although not shown in FIG. 20, the imaging lens of the lens barrel is disposed so as to face the front portion of the outer case 102. The lens barrel is accommodated in the exterior case 102 with the optical axis of the imaging optical system disposed in the lens barrel oriented in the horizontal direction. In this example, the imaging lens of the imaging optical system includes a zoom lens including the above-described variable focus lens. In the exterior case 102, an image sensor, which will be described later, is attached to the rear part of the lens barrel. A viewfinder device 106 is disposed behind the lens barrel and behind the exterior case 102.

  An opening for exposing an accessory shoe to which accessories such as an external video light and an external microphone are detachably attached is provided on the upper portion of the outer case 102. The accessory shoe is disposed immediately before the viewfinder device 106, and is normally detachably covered with a shoe cap 107 that opens and closes the opening. Furthermore, a stereo microphone 108 is provided in the lower part of the front surface of the outer case 102. Although not shown, a light emitting unit of a flash device that is integrally provided in the exterior case 102 is disposed on the front surface of the lens barrel.

  On one side surface of the exterior case 102, a grip portion 110 for gripping the exterior case 102 is provided. The gripping part 110 may also serve as a cover member of a mechanical deck that is housed therein and does not appear in the drawing. In that case, by opening the upper part of the gripping part 110 to the outside, for example, the cassette insertion slot of the built-in mechanical deck is exposed, and the tape cassette or the like can be attached or detached.

  Furthermore, on the upper rear side of the grip 110, a power switch 112 that also serves as a mode selection switch, a shutter button 113 that captures a still image, and images are continuously enlarged (tele) or reduced (wide) within a predetermined range. ) Zoom button 114 is provided. Further, a recording button not shown in the figure is provided below the power switch 112. Further, although not shown, a recording button is provided below the power switch 112, and a battery housing in which a battery device as a portable power source is detachably mounted on the side of the recording button, that is, on the back of the outer case 102. Parts are provided.

  The display device 104 is attached to the surface of the outer case 102 opposite to the grip portion 110 via the connecting member 140 so that the posture can be changed. The display device 104 fulfills the functions of, for example, a viewfinder and a touch panel, and includes a liquid crystal panel or the like.

FIG. 21 is a block diagram illustrating a schematic configuration of main parts of the imaging apparatus 100.
The imaging apparatus 100 includes an imaging optical system 151, an imaging element 156 that outputs a signal by photoelectrically converting subject light imaged through the imaging optical system 151, and an image that processes a signal transmitted from the imaging element 156. A signal processing unit 150. Further, the video signal processing unit 150 includes a video signal recording / reproducing unit 152 that records and reproduces a signal processed into a predetermined video signal.

The imaging lens constituting the imaging optical system 151 is configured to include the variable focus lens described above.
The image sensor 156 is configured by a charge coupled device (CCD) image sensor, a complementary metal oxide semiconductor (CMOS) image sensor, or the like.
The video signal recording / reproducing unit 152 includes an arithmetic circuit having a microcomputer (CPU), for example. In addition to the video signal processing unit 150, the video signal recording / reproducing unit 152 includes an internal memory 153 that records video signals, a monitor driving unit 154 that drives the display device 104, and a control unit 155 that controls the imaging optical system 151. Etc. are connected. An operation signal from the outside, such as an operation of a zoom button, is input to the control unit 155, and the lens position of the imaging optical system 151 is adjusted by a signal from the control unit 155.

  In the imaging apparatus 100 configured as described above, by using the variable focus lens according to the embodiment of the present invention for the imaging optical system 151, it is possible to obtain an excellent image without causing distortion of the deformed portion due to its own weight sag or the like. An image can be taken with a variable amount of a focal length sufficient for practical use. Further, spherical aberration can be suppressed by appropriately selecting the material of the deformation film. Further, by using a laminated piezoelectric element, it is possible to take an image with good hysteresis characteristics and practically sufficient high-speed response.

  The present invention is not limited to the configuration described in the above-described embodiment, and various modifications and changes can be made without departing from the configuration of the present invention.

It is the perspective block diagram which notched a part of lens part of the variable focus lens which concerns on embodiment of this invention. It is a section lineblock diagram of a lens part of a variable focus lens concerning an embodiment of the invention. It is a perspective block diagram of the principal part of the lens part of the variable focus lens which concerns on embodiment of this invention. It is a cross-sectional block diagram of the principal part of the lens part of the variable focus lens which concerns on embodiment of this invention. It is a perspective block diagram of the lens part of the variable focus lens which concerns on embodiment of this invention. It is a perspective block diagram of the lens part of the variable focus lens which concerns on embodiment of this invention. It is a perspective block diagram of the drive part of the variable focus lens which concerns on embodiment of this invention. It is a disassembled perspective block diagram of the leaf | plate spring part in the drive part of the variable focus lens which concerns on embodiment of this invention. It is a perspective block diagram of the frame in the drive part of the variable focus lens which concerns on embodiment of this invention. It is a disassembled perspective block diagram of the piezoelectric element part in the drive part of the variable focus lens which concerns on embodiment of this invention. It is a perspective block diagram of the drive part of the variable focus lens which concerns on embodiment of this invention. (A)-(c) is explanatory drawing of the deformation | transformation aspect of the leaf | plate spring of the variable focus lens which concerns on embodiment of this invention. It is a figure which shows the spherical aberration characteristic of a variable focus lens. It is a figure which shows the hysteresis characteristic in the variable focus lens which concerns on embodiment of this invention. It is a figure which shows the hysteresis characteristic in the variable focus lens which concerns on embodiment of this invention. It is a figure which shows the response characteristic in the variable focus lens which concerns on embodiment of this invention. It is a figure which shows the response characteristic in the variable focus lens which concerns on embodiment of this invention. It is a figure which shows the step response characteristic in the variable focus lens which concerns on embodiment of this invention. It is a figure which shows the step response characteristic in the variable focus lens which concerns on embodiment of this invention. 1 is a perspective configuration diagram of an imaging apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to an embodiment of the present invention.

Explanation of symbols

  1. Substrate, 2. 2. deformation part; Liquid, 4. Frame, 9. Diaphragm, 10 A pressing member, 20. Lens part, 30. Leaf spring part, 31. Pressing member, 32, 33. Holding member, 34. Leaf spring, 35. Fixing members 36, 36a, 36b. Presser, 40. Piezoelectric element portion, 41. Support members 41e, 41f. Projections (external force imparting members) 55, 55a, 55b. Piezoelectric element, 60. Frame, 80. Drive unit, 100. Imaging device

Claims (10)

A lens unit whose focal length changes due to a shape change of the light transmission surface;
A piezoelectric element, a leaf spring whose one end is fixed to the piezoelectric element, and disposed in the displacement direction of the piezoelectric element, fixed to the other end of the leaf spring, and pressed by the displacement of the piezoelectric element, the leaf spring A variable focus lens, comprising: a pressing portion that deforms the lens portion; and a driving portion that is fixed to the leaf spring and has an external force applying member that applies an external force to the lens portion. The variable focus lens according to claim 1,
A variable focus lens, wherein the piezoelectric element is a laminated piezoelectric element. The variable focus lens according to claim 1,
A variable focus lens in which a contact area of the pressing element pressed by displacement of the piezoelectric element is linear or planar. The variable focus lens according to claim 3.
The variable focus lens, wherein the pressing element has a cylindrical surface, and the cylindrical surface is pressed by displacement of the piezoelectric element. The variable focus lens according to claim 1,
A variable focus lens in which a pressing member is disposed on the leaf spring, and a deformation region of the leaf spring is a substantially linear region. The variable focus lens according to claim 1,
A variable focus lens provided with an elastic member that closely contacts the piezoelectric element and a fixing portion of the pressing element. The variable focus lens according to claim 1,
The variable focus lens, wherein the external force applying member is a protrusion provided on a support member that supports the piezoelectric element. The variable focus lens according to claim 1.
A variable focus lens in which a diaphragm is provided in the lens portion and the external force applying member is in contact with the diaphragm. The elastic member is deformed by the displacement of the laminated piezoelectric element,
A variable focus lens driving method characterized by amplifying an amount of deformation of the elastic member and applying an external force to deform the deformable portion of the variable focus lens having liquid between the light-transmitting substrate and the deformable portion. . An image sensor;
A signal processing unit that performs signal processing by inputting an image signal photoelectrically converted by the imaging device;
A piezoelectric element, a leaf spring whose one end is fixed to the piezoelectric element, and disposed in the displacement direction of the piezoelectric element, fixed to the other end of the leaf spring, and pressed by the displacement of the piezoelectric element, the leaf spring And a driving unit having an external force applying member that is fixed to the leaf spring and applies an external force to the lens unit, and a lens unit that changes a focal length due to a shape change of the light transmission surface. An imaging lens system including a variable focus lens.

Images