JP5170014B2 - Support mechanism for objective lens in optical head device - Google Patents

Description

  The present invention relates to an objective lens in an optical head device having a mechanism for condensing laser light with an objective lens and irradiating the object, and driving the objective lens so that the surface of the object is focused on the laser light. It relates to a support mechanism.

  As a device for condensing and irradiating laser light from an optical head device with an objective lens, a device for recording data on an optical storage medium such as an optical disk or reproducing data recorded on an optical storage medium, or laser processing a workpiece Devices that perform such operations are known. In such an apparatus, in order to focus the laser beam on the recording surface or surface of the object, focus servo control is performed to drive the objective lens in the optical axis direction based on a signal generated by the reflected light from the object. . For this reason, the optical head device has a structure in which an objective lens holder with an objective lens assembled is mounted on a bobbin and this bobbin is driven in the optical axis direction. The bobbin is sandwiched between a pair of upper and lower leaf springs and supported so as to be displaceable in the optical axis direction with respect to the fixed portion. For example, in Patent Document 1, a leaf spring integrally formed so that an outer ring and an inner ring are connected by a plurality of spiral connecting portions is prepared, and the outer ring of the leaf spring is fixed to a fixed portion, and A structure in which the inner ring is fixed to the bobbin has been proposed.

Japanese Patent Laid-Open No. 60-157732

  However, in the objective lens support structure proposed in Patent Document 1, when the bobbin is displaced in the optical axis direction and the leaf spring is deformed, the portion connecting the leaf spring and the bobbin is moved in a direction other than the optical axis direction. Stress is generated, and there is a problem that the bobbin vibrates in a direction perpendicular to the optical axis direction although it is minute. This vibration has a frequency of 1 kHz to 2 kHz.

  The present invention has been made to cope with the above-described problem. Even when the bobbin is displaced in the optical axis direction and the leaf spring is deformed, the bobbin is less likely to vibrate in a direction perpendicular to the optical axis direction. Objective.

In order to achieve the above object, the present invention is characterized in that a fixed portion having a through hole formed in the center, a cylindrical movable portion that is disposed in the through hole formed in the fixed portion and has an objective lens attached thereto, A leaf spring having a circular hole in the center and an outer peripheral portion fixed to the fixed portion and an inner peripheral portion fixed to the movable portion, and elastically supporting the movable portion by the plate spring, In the objective lens support mechanism in the optical head device that supports the objective lens so as to be displaceable in the optical axis direction, the leaf spring includes the outer peripheral portion and the inner peripheral portion of a donut-shaped metal plate having a circular hole in the center. A plurality of spiral slits are opened, and a ring-shaped reinforcing leaf spring is overlapped and fixed to the inner periphery , and the reinforcing leaf spring is the same as the circular hole of the leaf spring. A metal plate having a diameter smaller than that of the plate spring having a circular hole in the center. Te, so as not to cover the slits, lies in the notch along the forming line of the slit is formed.

  In the present invention, the cylindrical movable portion on which the objective lens is mounted is elastically supported by the leaf spring so that the inside of the through hole of the fixed portion can be displaced in the optical axis direction of the objective lens. For example, the movable portion may be supported by a leaf spring at two locations separated by a predetermined distance in the optical axis direction of the objective lens. The movable portion is biased and displaced in the optical axis direction of the objective lens (hereinafter simply referred to as the optical axis direction) by a magnetic force or the like. When the movable part is displaced in the optical axis direction, the leaf spring is deformed and a stress in a direction different from the optical axis direction is generated at the place where the movable part is connected. Since the ring-shaped reinforcing leaf spring is overlapped and fixed to the peripheral portion, the generation of stress in a direction different from the optical axis direction is reduced. Thereby, it becomes difficult for the movable part to vibrate in a direction perpendicular to the optical axis direction. Therefore, the focus servo control can be performed satisfactorily. The reinforcing plate spring is a ring-shaped metal plate having spring properties, and for example, a metal plate having the same thickness as the plate spring supporting the movable portion may be used. The reinforcing leaf spring may be fixed to both the front and back surfaces of the leaf spring that supports the movable portion, or may be fixed to only one surface.

  The leaf spring in the present invention is formed in a donut shape, and since a plurality of spiral slits are opened between the outer peripheral portion and the inner peripheral portion, the movable portion can be supported so as to be satisfactorily displaced in the optical axis direction. . In this case, if the slit is formed close to the central circular hole, good elasticity can be obtained in the leaf spring, but if the outer diameter of the reinforcing leaf spring stacked on the leaf spring is increased, good elasticity cannot be obtained. there is a possibility. Therefore, in the present invention, by forming a notch along the slit forming line of the leaf spring in the reinforcing leaf spring, both the leaf spring and the reinforcing leaf spring maintain good elasticity. As a result, according to the present invention, it is possible to suppress vibration in a direction perpendicular to the optical axis direction of the movable part while favorably elastically supporting the movable part with respect to the optical axis direction.

  Another feature of the present invention resides in that a viscous member is fixed around the outer peripheral side end of the slit of the leaf spring.

  According to the present invention, the vibration of the movable part can be effectively absorbed by fixing the viscous member around the outer peripheral side end of the slit of the leaf spring. Therefore, even when the above-described vibration cannot be suppressed by the reinforcing leaf spring alone, the vibration can be attenuated satisfactorily. Note that the viscous member is preferably fixed to a portion corresponding to the periphery of the outer peripheral side end of the slit after the reinforcing leaf spring is overlapped and fixed to the leaf spring.

It is an external appearance perspective view of the support mechanism of the objective lens of the optical head apparatus which concerns on embodiment. It is a top view of the support mechanism. It is a longitudinal cross-sectional view in the AA direction of FIG. It is a disassembled perspective view of the said support mechanism. It is a top view of a leaf | plate spring. It is a top view of a reinforcement ring board. It is a top view showing the state which piled up the reinforcement ring board on the leaf | plate spring. It is a graph showing the frequency characteristic in the radial direction, (a) is a measurement result when the reinforcing ring plate is not provided, (b) is a measurement result when the reinforcing ring plate is provided, (c) is around 1 kHz thereof. It is the graph which expanded and expressed the frequency characteristic. It is a graph showing the frequency characteristic in a tangential direction, (a) is a measurement result when a reinforcing ring plate is not provided, (b) is a measurement result when a reinforcing ring plate is provided, and (c) is 1 kHz thereof. It is the graph which expanded and expressed the frequency characteristic of the vicinity. It is a graph showing the frequency characteristic in an axial direction, (a) shows the measurement result when the reinforcing ring plate is not provided, and (b) shows the measurement result when the reinforcing ring plate is provided .

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is an external perspective view of a support mechanism for an objective lens in the optical head device according to the embodiment, FIG. 2 is a plan view of the support mechanism, and FIG. 3 is a longitudinal sectional view of the support mechanism. 4 is an exploded perspective view of the support mechanism. This support structure can be broadly divided into a cylindrical movable part 10 to which the objective lens 1 is attached, a fixed part 100 in which a through-hole is disposed in the center of the movable part 10, and the movable part 10 as a fixed part 100. On the other hand, it comprises an elastic spring portion 50 that elastically supports the objective lens 1 so as to be displaceable in the optical axis direction.

  The movable portion 10 is a portion that is attached to the objective lens 1 and is displaced integrally with the objective lens 1 in the optical axis direction of the objective lens 1. The movable portion 10 is an objective lens 1, an objective lens holder 20 that fixes the objective lens 1, and an objective. A bobbin 30 that houses the lens holder 20 and a coil 40 wound around the lower end of the bobbin 30 are configured. In the present specification, “upper” and “lower” represent positional relationships in the drawings, and do not mean absolute “upper” and “lower”.

  The objective lens holder 20 has a cylindrical shape, and the objective lens 1 is fixed to the tip so that the central axis of the cylinder coincides with the optical axis of the objective lens 1. The bobbin 30 is made of resin, and includes a holder storage portion 31 formed in a substantially rectangular parallelepiped shape, and a coil winding portion 32 extending in a cylindrical shape from below the holder storage portion 31. The holder storage portion 31 has a storage chamber 33 having a circular horizontal section at the center, and the objective lens holder 20 is fitted and fixed in the storage chamber 33. A cylindrical wall 34 serving as the upper end of the storage chamber 33 is erected on the upper surface of the holder storage portion 31, and an inner peripheral portion 53 of an upper leaf spring 51 </ b> A (described later) is bonded and fixed around the cylindrical wall 34. A ring-shaped upper flange surface 35 is formed.

  The coil winding portion 32 is a cylindrical body that extends downward from the holder storage portion 31 coaxially with the storage chamber 33, and is wound in the same direction so that the coil 40 forms a layer on the outer peripheral surface of the cylindrical wall 36. It has been turned. The cylindrical wall 36 has the same outer diameter as the cylindrical wall 34 of the holder storage portion 31 on the base side (holder storage portion 31 side), and is a portion around which the coil 40 is wound by being cut to a small diameter from the middle. Yes. One end of the coil 40 is connected to the upper leaf spring 51A via a conducting wire (not shown), and the other end is connected to the lower leaf spring 51B via a conducting wire (not shown). The upper leaf spring 51A and the lower leaf spring 51B form a part of the energization path.

  On the lower surface of the holder accommodating portion 31, a flat ring-shaped lower flange surface 37 to which the inner peripheral portion 53 of the lower leaf spring 51B is bonded and fixed around a portion where the cylindrical wall 36 of the coil winding portion 32 is erected. Is formed. The upper flange surface 35 and the lower flange surface 37 have the same shape and are surfaces orthogonal to the optical axis of the objective lens 1.

  Next, the elastic spring part 50 will be described. The elastic spring portion 50 includes an upper leaf spring 51A, a lower leaf spring 51B, and four reinforcing ring plates 60. Both the upper leaf spring 51A and the lower leaf spring 51B have the same shape. Therefore, when the two are not distinguished, they are simply called leaf springs 51. FIG. 5 is a plan view of the leaf spring 51. The leaf spring 51 is a donut-shaped thin metal plate with a circular hole 52 formed in the center. The inner peripheral portion 53 around the circular hole 52 is a portion for fixing the movable portion 10, and the outer peripheral portion 54 is fixed. The portion is fixed to the portion 100. The diameter of the circular hole 52 is the same as the outer diameter of the cylindrical walls 34 and 36 of the bobbin 30 (the inner diameters of the upper flange surface 35 and the lower flange surface 37), and is a portion through which the cylindrical walls 34 and 36 are inserted.

  In the leaf spring 51, a plurality of slits 55 extending in a spiral shape (spiral shape) are formed between the outer peripheral portion 54 and the inner peripheral portion 53. The slit 55 is an elongated opening extending so as to draw a curved line in the outer diameter direction and in the circumferential direction from a position slightly away from the circular hole 52 so as not to be continuous with the circular hole 52. In the present embodiment, the slits 55 are arranged at equal intervals of 90 degrees around the center of the circular hole 52.

  The leaf spring 51 supports the bobbin 30 at the inner peripheral portion 53, but the positional relationship in the circumferential direction between the slit 55 and the bobbin 30 is set so that the slit 55 does not overlap the flange surfaces 35 and 37 of the bobbin 30. Yes. Since the shape of the flange surfaces 35 and 37 is the same as the upper surface shape (or lower surface shape) of the holder storage portion 31, the region surrounded by the cylindrical walls 34 and 36 at the center from a substantially square (square with the corners cut off). It becomes the shape except. Therefore, when viewed in the circumferential direction, the flange surfaces 35 and 37 are wide at the corners of the holder storage portion 31 and narrow at the center between the corners (side surface center). Therefore, in the present embodiment, the inner end 55in of the slit 55 is positioned so as to face the center of the side surface of the holder storage portion 31, so that the slit 55 is not overlapped with the flange surfaces 35 and 37 as much as possible. Can be formed to the inside.

  A plurality of bonding holes 56 for allowing the adhesive to permeate are formed between the inner ends 55in of the adjacent slits 55 on the circumference connecting the inner ends 55in of the respective slits 55. Further, on the circumference connecting the outer ends 55out of the slits 55, between the outer ends 55out of the adjacent slits 55, screw insertion holes 57 for fixing the leaf springs 51 to the fixing portion 100 are formed. ing. Each slit 55 is formed with two semicircular cutouts 55cut for passing an energization wire (not shown) for energizing the coil 40, respectively.

  A reinforcing ring plate 60 is bonded to the front and back surfaces of the leaf spring 51. The reinforcing ring plate 60 corresponds to the reinforcing plate spring of the present invention, and as shown in FIG. 6, a metal plate having a spring property in which only the inner portion from the slit 55 is taken out from the plate spring 51 into a ring shape. It is. Accordingly, the reinforcing ring plate 60 is formed with a circular hole 61 having the same diameter as the circular hole 52 of the leaf spring 51 in the center, and an outer periphery of the reinforcing ring plate 60 having a spiral outer periphery 62 having the same shape as the inner line of the slit 55 of the leaf spring 51. The linear outer periphery 63 extending in the radial direction from the inner end of the spiral outer periphery 62 is alternately connected. That is, the reinforcing ring plate 60 is a ring-shaped metal plate having an outer diameter smaller than that of the leaf spring 51 and larger than the flange surfaces 35 and 37, and substantially triangular notches 64 are arranged at equal intervals on the outer periphery (90 degree intervals). 4 places are formed. Further, the reinforcing ring plate 60 is provided with a plurality of bonding holes 65 for allowing the adhesive to permeate the portions where the notches 64 are not formed.

  The plate spring 51 and the reinforcing ring plate 60 are both formed by etching a metal plate having the same thickness into the above shape. FIG. 7 is a plan view showing a state in which the reinforcing ring plate 60 is overlapped and bonded to the front and back surfaces of the leaf spring 51, and the reinforcing ring plate 60 is slightly painted for easy understanding. In the drawing, a two-dot chain line represents an outer peripheral line of the flange surfaces 35 and 37 of the bobbin 30 fixed to the leaf spring 51. The reinforcing ring plate 60 is overlaid so that the spiral outer periphery 62 is aligned with the inner line of the slit 55 of the leaf spring 51. Therefore, when the reinforcing ring plate 60 is superimposed on the leaf spring 51, the notch 64 of the reinforcing ring plate 60 faces the slit 55 of the leaf spring 51, so that the reinforcing ring plate 60 does not cover the slit 55 of the leaf spring 51. It has become. Further, when the leaf spring 51 and the reinforcing ring plate 60 are fixed to the flange surfaces 35 and 37 of the bobbin 30, the bonding hole 56 and the bonding hole 65 are the widest portions of the flange surfaces 35 and 37. Positioned to face each other.

  Since the periphery of the inner end 55in of the slit 55 of the leaf spring 51 (the portion surrounded by the broken line in FIG. 7) is a spring fulcrum, this portion is hereinafter referred to as a spring fulcrum 59. Further, the periphery of the outer end 55out of the slit 55 of the leaf spring 51 (the hatched portion in FIG. 7) is a portion where a viscous member 70, which will be described later, is fixed and absorbs vibration. This is called region 58.

  Next, the fixing unit 100 will be described. The fixing portion 100 is a portion that holds the outer peripheral portion 54 of the two leaf springs 51 (the upper leaf spring 51A and the lower leaf spring 51B) and supports the bobbin 30 so as to be displaceable in the vertical direction. 2 A base 120, a leaf spring pressing block 130, a substrate block 140, and an upper cover 150 are provided. The leaf spring pressing block 130 is a flat, substantially rectangular parallelepiped made of a non-magnetic (low magnetic permeability) light metal, and has an opening 131 penetrating vertically in the center. The upper surface of the leaf spring pressing block 130 is a flat surface around the opening 131 that fixes the outer peripheral portion 54 of the lower leaf spring 51B. The opening 131 is a space in which the bobbin 30 is disposed and the elastic deformation of the lower leaf spring 51B is allowed. Insertion holes 132 through which screws 160 for fixing the leaf spring retainer block 130 to the first base 110 are inserted are formed at four corners of the leaf spring retainer block 130. Further, next to the four insertion holes 132, screw holes 133 into which screws 161 for connecting and fixing the second base 120 to the leaf spring holding block 130 are screwed are formed. Further, around the opening 131, four insertion holes 134 through which screws 161 for fixing the substrate block 140 to the leaf spring holding block 130 with the lower leaf spring 51B interposed therebetween are formed at equal intervals in the circumferential direction. ing. In addition, a notch 135 that is notched outward is formed in the opening 131 of the leaf spring pressing block 130 so as not to cover the slit 55 of the lower leaf spring 51B.

  The substrate block 140 is fixed to the upper surface of the leaf spring pressing block 130 with the lower leaf spring 51B interposed therebetween. The substrate block 140 is a flat, generally cylindrical body made of a non-magnetic (low magnetic permeability) light metal, and has an opening 141 penetrating vertically in the center. The opening 141 has the same shape as the opening 131 of the leaf spring pressing block 130 in plan view. On the outer peripheral surface of the substrate block 140, vertical wall surfaces 142 are formed at positions facing each other, and the substrates 170 are fixed to the vertical wall surfaces 142 by screws 171, respectively. The substrate 170 is soldered with a conducting wire (not shown) for energizing the coil 40, and the vertical dimension thereof is the same as the vertical dimension of the substrate block 140. The upper and lower surfaces of the substrate block 140 are formed so that the periphery of the opening 141 is flat, and four screw holes 143 are formed through the opening 141 at equal intervals. The opening 141 of the substrate block 140 is formed with a notch 144 that is notched outward so as not to cover the slits 55 of the upper and lower leaf springs 51A and 51B.

  The leaf spring retainer block 130 and the substrate block 140 are positioned in such a manner that the insertion holes 134 and 57 and the screw hole 143 face each other with the outer peripheral portion 54 of the lower leaf spring 51B sandwiched therebetween. Connection is made by screwing screws 161 into the screw holes 143 from the lower surface side of the block 130. The upper cover 150 is fixed to the upper surface of the substrate block 140 with the upper plate spring 51A sandwiched therebetween. However, before assembling, before the upper cover 150 is fixed, the upper plate spring 51A and the lower plate spring 51B are not connected. The movable part 10 is arranged and fixed as follows.

  First, the reinforcing ring plate 60 is superimposed on the front and back surfaces of the lower leaf spring 51 fixed to the leaf spring holding block 130 in the above-described positional relationship, and the coil winding portion 32 of the bobbin 30 is placed in the circular hole 52 in this state. Insert from above. Then, after adjusting the circumferential direction of the bobbin 30 so that the bonding hole 56 of the lower leaf spring 51B (the bonding hole 65 of the reinforcing ring plate 60) faces the corner of the bobbin 30, the bonding holes 56, 65 are adjusted. Soak the adhesive. Thus, the lower leaf spring 51B and the reinforcing ring plate 60 are integrally fixed to the lower flange surface 37 of the bobbin 30 while maintaining a predetermined positional relationship.

  Next, the viscous member 70 is applied to the damper region 58 of the lower leaf spring 51B, and the viscous member 70 is irradiated with ultraviolet rays. The viscous member 70 is an impact buffer made of a material (for example, low-hardness butyl rubber, low-hardness acrylate) having a property that the hardness increases by irradiating ultraviolet rays and the hardness does not lead to complete curing. is there. Thereby, the viscous member 70 is fixedly provided in the damper region 58 of the lower leaf spring 51B.

  Next, the reinforcing ring plate 60 is overlapped on the front and back surfaces of the upper leaf spring 51A in the above-described positional relationship, the outer peripheral portion 54 is placed on the upper surface of the substrate block 140, and the cylindrical wall 34 of the bobbin 30 is lowered in the circular hole 52. Insert through. Then, after adjusting the circumferential direction of the upper plate spring 51 </ b> A so that the through hole 57 of the upper plate spring 51 </ b> A faces the screw hole 143 of the substrate block 140, the adhesive is soaked into the bonding holes 56 and 65. Thereby, the upper leaf spring 51 </ b> A and the reinforcing ring plate 60 are integrally fixed to the upper flange surface 35 of the bobbin 30 while maintaining a predetermined positional relationship. In this way, the movable portion 10 is fixedly provided between the upper leaf spring 51A and the lower leaf spring 51B.

  The upper cover 150 is a ring-shaped plate having a circular hole 151 formed in the center, and has a shape in which a plate surface around the circular hole 151 is lifted upward. The circular hole 151 is a portion serving as an emission port for emitting laser light from the objective lens 1, and is formed at a position where the center coincides with the optical axis of the objective lens 1. The upper cover 150 is provided with an insertion hole 152 for inserting the screw 162 and a slit 153 extending in a spiral shape around the circular hole 151. The slit 153 is an opening formed in the same shape as the slit 55 of the upper leaf spring 51A so that the viscous member 70 can be applied to the upper leaf spring 51A after the upper cover 150 is fixed to the substrate block 140.

  The substrate block 140 and the upper cover 150 are positioned so that the insertion holes 152 and 57 and the screw holes 143 face each other with the outer peripheral portion 54 of the upper leaf spring 51A interposed therebetween. They are connected by screwing screws 162 into the screw holes 143 from the side. A viscous member 70 is fixedly provided in the damper region 58 of the upper leaf spring 51A. The viscous member 70 is applied to the damper region 58 through the slit 153 after the upper cover 150 is assembled to the substrate block 140, and is cured and fixed to the damper region 58 by being irradiated with ultraviolet rays.

  In this way, the bobbin 30 is elastically supported by the upper plate spring 51A and the lower plate spring 51B and can be displaced in the vertical direction (the optical axis direction of the objective lens 1). In the present embodiment, the distance between the upper flange surface 35 and the lower flange surface 37 of the bobbin 30 is obtained by subtracting two sheets of the thickness of the reinforcing ring plate 60 from the thickness (height dimension) of the substrate block 140. It is the size. Accordingly, the bobbin 30 is held in a state where the upper leaf spring 51A and the lower leaf spring 51B are parallel to each other. Further, by being assembled in this manner, one of the two substrates 170 attached to the outer periphery of the substrate block 140 is electrically connected to the upper leaf spring 51A, and the other is electrically connected to the lower leaf spring 51B. . Thereby, an energization circuit for energizing the coil 40 is formed between the two substrates 170.

  The leaf spring pressing block 130 is fixed to the upper surface of the second base 120. The second base 120 is a plate body having the same outer shape as the plate spring pressing block 130 in plan view, and a cylindrical pole 121 is erected at the center thereof. Around the cylindrical pole 121, a stepped portion 122 that is recessed in a ring shape is formed, and a ring-shaped magnet (permanent magnet) 180 is bonded to the outer stepped portion 122. The magnet 180 is arranged so that the upper surface is an N pole and the lower surface is an S pole. A ring-shaped yoke 190 is bonded to the upper surface of the magnet 180. The inner diameter of the yoke 190 is slightly smaller than the inner diameter of the magnet 180.

  The cylindrical pole 121 is a cylindrical body whose outer diameter is slightly smaller than the inner diameter of the coil winding portion 32 of the bobbin 30, and the inner cylindrical space serves as an optical path for laser light. In the four corners of the second base 120, insertion holes 123 for inserting screws 160 for fixing the leaf spring pressing block 130 to the first base 110 are formed. Further, adjacent to the insertion hole 123, an insertion hole 124 for inserting a screw 163 for connecting and fixing the second base 120 to the leaf spring pressing block 130 is formed. In the second base 120, with the magnet 180 and the yoke 190 attached, the insertion hole 124 and the screw hole 133 of the leaf spring presser block 130 face each other, and the screw 163 is screwed into the screw hole 133 from the second base 120 side. To the leaf spring holding block 130.

  In a state where the second base 120 is connected to the leaf spring presser block 130, the cylindrical pole 121 of the second base 120 is inserted into the coil winding portion 32 of the bobbin 30 with a slight gap. Further, the inner peripheral surface of the yoke 190 is in a state of being close to the outer peripheral surface of the coil winding portion 32 of the bobbin 30. Therefore, by energizing the coil 40, a vertical force can be applied to the bobbin 30 by the interaction between the magnetic field generated from the coil 40 and the magnetic field of the magnet 180.

  The second base 120 has a convex portion 125 swelled like a bowl at the center of the lower surface thereof, and the center of the convex portion 125 is an opening of the cylindrical pole 121. The second base 120 is fixed to the upper surface of the first base 110. The first base 110 has a recess 111 that is recessed in a bowl shape at the center of the upper surface thereof, and the center of the recess 111 is a circular opening 112. The first base 110 holds the second base 120 stably by bringing the convex portion 125 of the second base 120 into close contact with the concave portion 111. The first base 110 has four screw holes 113 formed around the recess 111. With the screw hole 113 and the insertion hole 132 formed in the leaf spring retainer block 130 facing each other, the screw 160 is screwed into the screw hole 113 from the leaf spring retainer block 130 side, whereby the leaf spring retainer block 130 is It is fixed to the first base 110 via the second base 120.

  In the objective lens support mechanism configured as described above, the bobbin 30 holding the objective lens 1 is elastically supported by the fixed portion 100 by the upper plate spring 51A and the lower plate spring 51B. Further, the central axes of the movable portion 10, the fixed portion 100, and the elastic spring portion 50 are kept in a state where they coincide with the optical axis of the objective lens 1.

  The optical head device includes a laser light source (not shown) that emits laser light from the first base 110 side toward the objective lens 1. Laser light emitted from the laser light source enters the objective lens 1 through the cylindrical pole 121 of the second base 120, the bobbin 30, and the objective lens holder 20, and is condensed by the objective lens 1 to be an object (for example, an optical disc). If it is an apparatus, it is irradiated to an optical disk, and if it is a laser processing apparatus, it is irradiated to a processing object. The laser light is reflected by the object and passes again through the objective lens 1, the objective lens holder 20, the bobbin 30, and the cylindrical pole 121 of the second base 120. The optical head device includes a photodetector (not shown) that receives reflected light of the laser beam, and shifts in the optical axis direction between the focal position of the laser beam and the recording surface or surface of the object from the received light signal output by the photodetector. A focus servo control circuit that generates a corresponding focus error signal and controls energization to the coil 40 based on the focus error signal is provided.

  When the coil 40 is energized by such a focus servo control circuit, the bobbin 30 is driven in the optical axis direction of the objective lens 1 so that the focal position of the laser beam coincides with the recording surface or surface of the object. In this case, the displacement direction of the bobbin 30 follows the direction of the drive current flowing through the coil 40, and the amount of displacement is proportional to the magnitude of the drive current. Therefore, by controlling the direction and magnitude of the drive current flowing through the coil 40, the objective lens 1 can be displaced by a necessary amount in the optical axis direction, thereby enabling focus control.

  When such focus servo control is performed, the leaf spring 51 is deformed as the bobbin 30 is displaced in the optical axis direction. As a result, stress in a direction other than the optical axis direction is generated at the spring fulcrum 59, and the bobbin 30 is likely to vibrate in a direction perpendicular to the optical axis direction. Therefore, in the present embodiment, the reinforcing ring plate 60 is superimposed on the inner peripheral portion 53 of the upper and lower leaf springs 51A and 51B, thereby suppressing vibration in a direction perpendicular to the optical axis direction. FIG. 8 shows frequency characteristics in the radial direction (Y direction in FIG. 2) in the objective lens support mechanism, and FIG. 9 shows frequency characteristics in the tangential direction (X direction in FIG. 2) in the objective lens support mechanism. . This frequency characteristic is measured using a dynamic scan analyzer and a vibrometer. In each figure, (A) is a measurement result when the reinforcing ring plate 60 is not provided, and (B) is a reinforcement. The measurement result when the ring plate 60 is provided, (C) is an enlarged view of the frequency characteristics near 1 kHz. FIG. 10 shows the frequency characteristics in the axial direction (the optical axis direction of the objective lens 1) in the objective lens support mechanism. FIG. 10A shows the measurement result when the reinforcing ring plate 60 is not provided, and FIG. It is a measurement result when the reinforcing ring plate 60 is provided.

  As can be seen from this measurement result, in the direction perpendicular to the optical axis direction (radial direction and tangential direction), resonance is detected in the frequency band of 1 kHz to 2 kHz when the reinforcing ring plate 60 is not provided. However, when the reinforcing ring plate 60 is provided, the resonance can be suppressed. Further, as shown in FIG. 10, it was confirmed that the frequency characteristics in the optical axis direction hardly change depending on the presence or absence of the reinforcing ring plate 60. Therefore, by providing the reinforcing ring plate 60, the frequency characteristics in the direction perpendicular to the optical axis direction can be improved without changing the frequency characteristics in the optical axis direction. The reason for this is considered to be that stress in directions other than the optical axis direction at the spring fulcrum 59 can be reduced by overlapping the reinforcing ring plate 60 on the upper and lower leaf springs 51A and 51B.

  Further, in this embodiment, the notch 62 is provided around the reinforcing ring plate 60 so that the reinforcing ring plate 60 does not cover the slit 55 of the leaf spring 51, so that a sufficient reinforcing area is secured. Both the leaf spring 51 and the reinforcing ring plate 60 maintain good elasticity. As a result, vibration in a direction perpendicular to the optical axis direction of the bobbin 30 can be suppressed while the bobbin 30 is elastically supported favorably with respect to the optical axis direction. Further, since the viscous member 70 is fixed to the damper region 58 of the leaf spring 51, the vibrations of the upper and lower leaf springs 51A and 51B can be absorbed and quickly attenuated. Therefore, even if the reinforcing ring plate 60 alone cannot suppress the vibration, the vibration can be attenuated satisfactorily.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the object of the present invention.

Further, in this embodiment, a configuration in which the reinforcing ring plate 60 is fixed to both surfaces (front and back surfaces) of the leaf spring 51 is adopted, but the reinforcing ring plate 60 is fixed to only one surface of the leaf spring 51. There may be. For example, the leaf spring 51 may be sandwiched between the flange surface 35 (37) and the reinforcing ring plate 60. Further, the reinforcing ring plate 60 is not necessarily provided on both of the two leaf springs 51, and may be provided only on one of the leaf springs 51.

DESCRIPTION OF SYMBOLS 1 ... Objective lens, 10 ... Movable part, 20 ... Objective lens holder, 30 ... Bobbin, 31 ... Holder accommodating part, 32 ... Coil winding part, 33 ... Storage chamber, 34 ... Cylindrical wall, 35 ... Upper flange surface, 36 DESCRIPTION OF SYMBOLS ... Cylindrical wall, 37 ... Lower flange surface, 40 ... Coil, 50 ... Elastic spring part, 51A ... Upper leaf | plate spring, 51B ... Lower leaf | plate spring, 52 ... Circular hole, 53 ... Inner peripheral part, 54 ... Outer peripheral part, 55 ... Slit, 56 ... hole for bonding, 58 ... damper region, 59 ... spring fulcrum, 60 ... reinforcing ring plate (ring-shaped reinforcing plate spring), 61 ... circular hole, 64 ... notch, 65 ... hole for bonding, 70 ... viscous member, 100 ... fixing part, 110 ... first base, 120 ... second base, 121 ... cylindrical pole, 130 ... leaf spring pressing block, 131 ... opening, 140 ... substrate block, 141 ... opening, 150 ... upper cover 151 ... circular holes, 170 ... substrate , 180 ... magnet, 190 ... yoke.

Claims (2)

A fixing part having a through hole formed in the center;
A cylindrical movable part that is disposed in a through-hole formed in the fixed part and is equipped with an objective lens;
A leaf spring having a circular hole in the center, an outer peripheral portion fixed to the fixed portion and an inner peripheral portion fixed to the movable portion, and elastically supporting the movable portion by the plate spring, In the objective lens support mechanism in the optical head device that supports the objective lens so as to be displaceable in the optical axis direction,
The leaf spring opens a plurality of spiral slits between the outer peripheral portion and the inner peripheral portion of a donut-shaped metal plate having a circular hole in the center, and a ring-shaped reinforcing leaf spring in the inner peripheral portion Is stuck and piled up ,
The reinforcing leaf spring is a metal plate having a diameter smaller than that of the leaf spring having a circular hole having the same diameter as the circular hole of the leaf spring in the center, and is formed in the slit forming line so as not to cover the slit. A support mechanism for an objective lens in an optical head device, wherein a cutout is formed along the notch . 2. A support mechanism for an objective lens in an optical head device according to claim 1 , wherein a viscous member is fixed around an outer peripheral side end of the slit of the leaf spring.

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