Abstract:
An optical pickup has a lens actuator, at least one suspension wire having a first end and an opposite second end, the lens actuator being held by the wire at the first end, and a support base to which the wire is fixed at the second end. The support base has at least one cutaway section provided as corresponding to the wire, having a concavity to receive at least partially the wire in cross section orthogonal to a longitudinal direction of the wire, the concavity curving in a direction parallel to the cross section of the wire, and a land formed around the cutaway section, the wire being soldered to the land at the second end while the wire is being received at least partially by the concavity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims the benefit of priority from the prior Japanese Patent Application No. 2008-168513 filed on Jun. 27, 2008, the entire contents of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an optical pickup with a lens actuator held by suspension wires fixed to a suspension-wire support base. 
     An optical pickup has been widely used in optical-disc recording and/or reproducing apparatuses, as a main component for recording information on or reproducing it from optical-information storage media, such as, optical discs. 
     An optical pickup is mainly constituted by: a lens actuator for tracking and focusing to an optical disc; suspension wires for holding and moving the actuator; and a suspension-wire support base to which the wires are fixed in order to hold the actuator. 
     Shown in  FIGS. 1 to 3  is an example of an optical pickup disclosed in Japanese Un-examined Patent Publication No. 2004-152421. 
     As shown in (a) and (b) of  FIG. 1 , a known optical pickup  100  is mainly constituted by: a lens actuator  102 ; four suspension wires  104   a ,  104   b ,  104   c  and  104   d  for holding and moving the actuator  102 ; and a suspension-wire support base  110  to which the wires  104   a ,  104   b ,  104   c  and  104   d  are fixed in order to hold the actuator  102 . 
     Shown in (a) and (b) of  FIG. 1  are perspective views of the optical pickup  100  when viewed from the lens actuator  102  side and the suspension-wire support base  110  side, respectively. 
     Mounted on the suspension-wire support base  110  is a printed circuit board  112 , as shown in  FIG. 2 , that is a plan view when viewed in a direction indicated by an arrow S 1  in (b) of  FIG. 1 . 
     Provided on the printed circuit board  112  are: holes  116   a ,  116   b ,  116   c  and  116   d  into which the suspension wires  104   a ,  104   b ,  104   c  and  104   d  are inserted, respectively; and lands  114   a ,  114   b ,  114   c  and  114   d  formed on one side of the board  112  and formed as surrounding the holes  116   a ,  116   b ,  116   c  and  116   d , respectively. 
     The holes  116   a ,  116   b ,  116   c  and  116   d  have a larger diameter than the suspension wires  104   a ,  104   b ,  104   c  and  104   d  so that the wires can easily be inserted into the holes. 
     Discussed with reference to (a) and (b) of  FIG. 3  is how the suspension wire  104   c  is inserted into the hole  116   c  and fixed to the land  114   c . The same is true for the suspension wires  104   a ,  104   b  and  104   d  to the holes  116   a ,  116   b  and  116   d , and the lands  114   a ,  114   b  and  114   d , respectively. 
     As illustrated in (a) of  FIG. 3 , that is an enlarged view of the corner of the printed circuit board  112  on which the land  114   c  is formed, the suspension wire  104   c  is inserted into the hole  116   c.    
     The suspension wire  104   c  is then fixed to the land  114   c  with a solder  106 , as shown in (b) of  FIG. 3 . While the solder  106  is being applied, it creates tension to the suspension wire  104   c  with dynamic moments in all directions (360°) as indicated by allows in (b) of  FIG. 3  that is also an enlarged view of the corner of the printed circuit board  112  on which the land  114   c  is formed. 
     Such dynamic moments are also created for the suspension wires  104   a ,  104   b  and  104   d.    
     The dynamic moments cause that the suspension wires  104   a ,  104   b ,  104   c  and  104   d  are fixed to the lands  114   a ,  114   b ,  114   c  and  114   d , respectively, in random positions which may vary per suspension wire or per optical pickup. 
     Such random positions of the suspension wires  104   a ,  104   b ,  104   c  and  104   d  on the printed circuit board  112  lead to deviation of the lens actuator  102  with respect to the optical disc, which lowers the accuracy of tracking and focusing, thus causing tracking and/or focusing errors. Therefore, such deviation requires to be minimized as much as possible. 
     SUMMARY OF THE INVENTION 
     A purpose of the present invention is to provide an optical pickup with higher positional accuracy for suspension wires fixed to suspension-wire support base. 
     The present invention provides an optical pickup comprising: a lens actuator; at least one suspension wire having a first end and an opposite second end, the lens actuator being held by the suspension wire at the first end; and a suspension-wire support base to which the suspension wire is fixed at the second end, wherein the suspension-wire support base includes: at least one cutaway section provided as corresponding to the suspension wire, having a concavity to receive at least partially the suspension wire in cross section orthogonal to a longitudinal direction of the suspension wire, the concavity curving in a direction parallel to the cross section of the suspension wire; and a land formed around the cutaway section, the suspension wire being soldered to the land at the second end while the suspension wire is being received at least partially by the concavity. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows perspective views of a known optical pickup in (a) and (b) viewed from a lens actuator side and a suspension-wire support base side, respectively; 
         FIG. 2  shows a plan view of a printed circuit board installed in the known optical pickup; 
         FIG. 3  shows enlarged views of each of four corners of the printed circuit board of the known optical pickup in (a) and (b) which illustrates dynamic moments caused by soldering; 
         FIG. 4  shows perspective views of a first preferred embodiment of an optical pickup in (a) and (b) viewed from a lens actuator side and a suspension-wire support base side, respectively; 
         FIG. 5  shows a plan view of a printed circuit board installed in the first embodiment of the optical pickup; 
         FIG. 6  shows enlarged views of each of four corners of the printed circuit board of the first embodiment, illustrating a feature of the present invention, in which (a) shows an enlarged plan view of a land formed on the corner, (b) an enlarged plan view of the land after soldering, (c) a schematic sectional view taken on line A 1 -A 2  of (a), and (d) a schematic sectional view taken on line A 1 -A 2  of (b); 
         FIG. 7  shows enlarged views of each of four corners of a printed circuit board of a second preferred embodiment of an optical pickup, illustrating a feature of the present invention, in which (a) shows an enlarged plan view of a land formed on the corner, (b) an enlarged plan view of the land after soldering, (c) a schematic sectional view taken on line A 1 -A 2  of (a), and (d) a schematic sectional view taken on line A 1 -A 2  of (b); 
         FIG. 8  shows enlarged views of each of four corners of a printed circuit board of a first modification to the second embodiment, illustrating a feature of the present invention, in which (a) shows an enlarged plan view of a land formed on the corner and (b) an enlarged plan view of the land after soldering; and 
         FIG. 9  shows enlarged views of each of four corners of a printed circuit board of a second modification to the second embodiment, illustrating a feature of the present invention, in which (a) shows an enlarged plan view of a land formed on the corner and (b) an enlarged plan view of the land after soldering. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Preferred embodiments and modifications of an optical pickup according to the present invention will be described with reference to  FIGS. 4 to 9 . 
     First Embodiment 
     A first embodiment of an optical pickup according to the present invention will be described with reference to  FIGS. 4 to 6 . 
     As shown in (a) and (b) of  FIG. 4 , an optical pickup  30  is mainly constituted by: a lens actuator  1  for tracking and focusing to an optical disc (not shown); four suspension wires  2   a ,  2   b ,  2   c  and  2   d  for holding and moving the actuator  1 ; and a suspension-wire support base  10  to which the wires  2   a ,  2   b ,  2   c  and  2   d  are fixed in order to hold the actuator  1 . 
     Shown in (a) and (b) of  FIG. 4  are perspective views of the optical pickup  30  when viewed from the lens actuator  1  side and the suspension-wire support base  10  side, respectively. 
     Mounted on the suspension-wire support base  10  is a printed circuit board  12 , as shown in  FIG. 5  that is a plan view when viewed in a direction indicated by an arrow S 2  in (b) of  FIG. 4 . In detail, the circuit board  12  is supported by a base section  18  of the support base  10 . The printed circuit board  12  may be a flexible printed circuit board. 
     Provided on the printed circuit board  12  are: cutaway sections  16   a ,  16   b ,  16   c  and  16   d  in the vicinity of the four corners of the circuit board  12 , having concavities in which the suspension wires  2   a ,  2   b ,  2   c  and  2   d , respectively, can be installed, at least part of each wire in cross section orthogonal to the longitudinal direction of each wire; and lands  14   a ,  14   b ,  14   c  and  14   d  formed on one side of the circuit board  12  and around the cutaway sections  16   a ,  16   b ,  16   c  and  16   d , respectively, to which at least part of the wires  2   a ,  2   b ,  2   c  and  2   d  are fixed, respectively. 
     Provided on the base section  18  are holes  20   a ,  20   b ,  20   c  and  20   d , as shown in  FIG. 6 , having a larger diameter than the suspension wires  2   a ,  2   b ,  2   c  and  2   d  so that the wires can easily be inserted into the holes. 
     The printed circuit board  12  is attached to the base section  18  with an adhesive or screws in such a manner that the cutaway sections  16   a ,  16   b ,  16   c  and  16   d  match the holes  20   a ,  20   b ,  20   c  and  20   d , respectively, as shown in  FIG. 6 . 
     Shown in (a) of  FIG. 6  is an enlarged plan view of the corner of the printed circuit board  12  on which the land  14   c  is formed. Shown in (b) of  FIG. 6  is an enlarged plan view of the land  14   c  after soldering. Shown in (c) of  FIG. 6  is a schematic sectional view taken on line A 1 -A 2  (that passes through the center of the hole  20   c ) of (a) of  FIG. 6 . Shown in (d) of  FIG. 6  is a schematic sectional view taken on line A 1 -A 2  of (b) of  FIG. 6 . The illustrated configurations for the land  14   c  in (a) to (d) of  FIG. 6  are also applied to the lands  14   a ,  14   b  and  14   d.    
     As shown in (c) and (d) of  FIG. 6 , in the first embodiment, the holes  20   a ,  20   b ,  20   c  and  20   d  have a tapered opening so that the suspension wires  2   a ,  2   b ,  2   c  and  2   d  can easily be inserted thereto, respectively. 
     Described next with reference to  FIG. 6  is how the suspension wire  2   c  is fixed to the land  14   c  with a solder  6 . The same is true for the suspension wires  2   a ,  2   b  and  2   d  to the lands  14   a ,  14   b  and  14   d , respectively. 
     As shown in (a) and (c) of  FIG. 6 , the suspension wire  2   c  is inserted into the hole  20   c  of the base section  18  along the cutaway section  16   c  from the land  14   c  side on the printed circuit board  12 . 
     Next, as shown in (b) and (d) of  FIG. 6 , the suspension wire  2   c  is fixed to the land  14   c  with the solder  6 . 
     While the solder  6  is being applied, it creates tension to the suspension wire  2   c . However, the land  14   c  is formed as surrounding the cutaway section  16   c , or on one side, the left side in (b) of  FIG. 6 , with respect to the center axis of the wire  2   c . The configuration of the land  14   c  forces the tension to create dynamic moments only one side in the directions as indicated by allows in (b) of  FIG. 6 . Such one-side dynamic moments force the wire  2   c  to move to the one side, or the land  14   c  side, and fixed there. 
     Therefore, compared with the known optical pickup  100 , as discussed with respect to (b) of  FIG. 3 , the suspension wires  2   a ,  2   b ,  2   c  and  2   d  can be fixed to the suspension-wire support base  10  at higher positional accuracy, in the first embodiment. 
     Second Embodiment 
     A second embodiment of an optical pickup according to the present invention will be described with reference to  FIG. 7 . 
     The illustrated configurations shown in (a) to (d) of  FIG. 7  in the second embodiment correspond to those in (a) to (d) of  FIG. 6 , respectively, in the first embodiment. 
     The differences between the first and second embodiments lie in the shape of cutaway sections and lands. 
     Therefore, the second embodiment will be described mainly with respect the relationship between the suspension wires and the cutaway sections and lands formed on the printed circuit board. 
     In the following description of the second embodiment, the same or analogous elements are given the same signs or numerals as the first embodiment. 
     As shown in  FIG. 7 , a printed circuit board  42  is provided with cutaway sections  46   a ,  46   b ,  46   c  and  46   d  in the vicinity of the four corners of the circuit board  42 , having concavities in which the suspension wires  2   a ,  2   b ,  2   c  and  2   d , respectively, can be installed, at least part of each wire in cross section orthogonal to the longitudinal direction of each wire. The printed circuit board  42  may be a flexible circuit board. 
     The cutaway sections  46   a ,  46   b ,  46   c  and  46   d  are constituted by: arc-like sections  47   a ,  47   b ,  47   c  and  47   d , respectively, having an internal diameter the same as or a little bit larger than the external diameter of the suspension wires  2   a ,  2   b ,  2   c  and  2   d , respectively; and opening sections  48   a ,  48   b ,  48   c  and  48   d , respectively, having a width the same as or a little bit larger than the internal diameter of the arc-like sections  47   a ,  47   b ,  47   c  and  47   d , respectively. Each of the opening sections  48   a ,  48   b ,  48   c  and  48   d  opens widely towards the outside of the printed circuit board  42 . 
     Moreover, the printed circuit board  42  is provided with arc-like lands  44   a ,  44   b ,  44   c  and  44   d  formed on one side of the circuit board  42  and around the cutaway sections  46   a ,  46   b ,  46   c , and  46   d , respectively, particularly, around the arc-like sections  47   a ,  47   b ,  47   c  and  47   d , respectively. 
     The printed circuit board  42  is attached to the base section  18  with an adhesive or screws in such a manner that the cutaway sections  46   a ,  46   b ,  46   c  and  46   d  match the holes  20   a ,  20   b ,  20   c  and  20   d , respectively. 
     Described next with reference to  FIG. 7  is how the suspension wire  2   c  is fixed to the land  44   c  with the solder  6 . The same is true for the suspension wires  2   a ,  2   b  and  2   d  to the lands  44   a ,  44   b  and  44   d , respectively. 
     As shown in (a) and (c) of  FIG. 7 , the suspension wire  2   c  is inserted into the hole  20   c  of the base section  18  along the cutaway section  46   c  from the land  44   c  side on the printed circuit board  42 . 
     Next, as shown in (b) and (d) of  FIG. 7 , the suspension wire  2   c  is fixed to the land  44   c  with the solder  6 . 
     While the solder  6  is being applied, it creates tension to the suspension wire  2   c . However, the land  44   c  is formed as surrounding the cutaway section  46   c , or on one side, the left side in (b) of  FIG. 7 , with respect to the center axis of the wire  2   c . The configuration of the land  44   c  forces the tension to create dynamic moments only one side in the directions as indicated by allows in (b) of  FIG. 7 . Such one-side dynamic moments force the wire  2   c  to move to the one side, or the land  44   c  side and fixed there. 
     Therefore, compared with the known optical pickup  100 , as discussed with respect to (c) of  FIG. 3 , the suspension wires  2   a ,  2   b ,  2   c  and  2   d  are fixed to the suspension-wire support base  10  at higher positional accuracy, in the second embodiment. 
     As described above, the cutaway sections  46   a ,  46   b ,  46   c  and  46   d  are constituted by: the arc-like sections  47   a ,  47   b ,  47   c  and  47   d , respectively, having an internal diameter the same as or a little bit larger than the external diameter of the suspension wires  2   a ,  2   b ,  2   c  and  2   d , respectively; and the opening sections  48   a ,  48   b ,  48   c  and  48   d , respectively, having a width the same as or a little bit larger than the internal diameter of the arc-like sections  47   a ,  47   b ,  47   c  and  47   d , respectively. Each of the opening sections  48   a ,  48   b ,  48   c  and  48   d  opens widely towards the outside of the printed circuit board  42 . 
     Such configurations of the cutaway sections  46   a ,  46   b ,  46   c  and  46   d  provide the following advantages. 
     The suspension wires  2   a ,  2   b ,  2   c  and  2   d  can easily be inserted into the holes  20   a ,  20   b ,  20   c  and  20   d , respectively, along the opening sections  48   a ,  48   b ,  48   c  and  48   d , respectively, each opening widely towards the outside of the printed circuit board  42 . 
     The suspension wires  2   a ,  2   b ,  2   c  and  2   d  can be installed in the arc-like sections  47   a ,  47   b ,  47   c  and  47   d , respectively, at least part of each wire in cross section orthogonal to the longitudinal direction of each wire, while each wire is pushed to the land side due the tension created by the solder  6 . 
     Therefore, compared with the first embodiment, the suspension wires  2   a ,  2   b ,  2   c  and  2   d  can be fixed to the suspension-wire support base  10  at higher positional accuracy, in the second embodiment. 
     MODIFICATION 
     Described next with respect to  FIGS. 8 and 9  are a first and a second modification, respectively, to the second embodiment. 
     Shown in (a) and (b) of  FIGS. 8 and 9  are enlarged plan views of the modifications to the second embodiment, which correspond to (a) and (b) of  FIG. 7 , respectively. 
     The difference between the first modification shown in  FIG. 8  and the second embodiment lies in the shape of lands. 
     Therefore, the first modification will be described mainly with respect a method to solder the suspension wires to the lands on the printed circuit board. 
     In the following description of the first modification, the same or analogous elements are given the same signs or numerals as the second embodiment. 
     Compared with the arc-like lands  44   a ,  44   b ,  44   c  and  44   d  of the second embodiment shown in (a) of  FIG. 7 , arc-like lands  54   a ,  54   b ,  54   c  and  54   d  of the first modification are formed wider as shown in (a) of  FIG. 8 . 
     In detail, the lands  54   a ,  54   b ,  54   c  and  54   d  are formed as having the maximum widths W 54   a , W 54   b , W 54   c  and W 54   d , respectively, each on a straight line that is orthogonal to a peripheral edge of the circuit board  42  and that passes a point on an arc of each of the arc-like sections  47   a ,  47   b ,  47   c  and  47   d . The point on the arc is the farthest from the peripheral edge among points on the arc, or it is the deepest point of a concavity created by each arc-like section in parallel to the cross section of each suspension wire. 
     Such land configuration offers higher tension controllability than that in the second embodiment, forcing the tension of the solder  6  to create the maximum dynamic moment in the direction in which the lands  54   a ,  54   b ,  54   c  and  54   d  have the maximum widths W 54   a , W 54   b , W 54   c  and W 54   d , respectively. 
     Therefore, compared with the second embodiment, the suspension wires  2   a ,  2   b ,  2   c  and  2   d  are fixed to the suspension-wire support base  10  at higher positional accuracy, in the first modification. 
     The difference between the second modification shown in  FIG. 9  and the second embodiment also lies in the shape of lands. 
     Therefore, the second modification will be described mainly with respect a method to solder the suspension wires to the lands on the printed circuit board. 
     In the following description of the second modification, the same or analogous elements are given the same signs or numerals as the second embodiment. 
     Compared with the arc-like lands  44   a ,  44   b ,  44   c  and  44   d  of the second embodiment shown in (a) of  FIG. 7 , lands  64   a ,  64   b ,  64   c  and  64   d  of the second modification are formed into a semi-elliptical shape. 
     In detail, the lands  64   a ,  64   b ,  64   c  and  64   d  are formed as having the maximum widths W 64   a , W 64   b , W 64   c  and W 64   d , respectively, each on a straight line that is orthogonal to a peripheral edge of the circuit board  42  and that passes a point on an arc of each of the arc-like sections  47   a ,  47   b ,  47   c  and  47   d . The point on the arc is the farthest from the peripheral edge among points on the arc, or it is the deepest point of a concavity created by each arc-like section in parallel to the cross section of each suspension wire. 
     Such land configuration also offers higher tension controllability than that in the second embodiment, forcing the tension of the solder  6  to create the maximum dynamic moment in the direction in which the lands  64   a ,  64   b ,  64   c  and  64   d  have the maximum widths W 64   a , W 64   b , W 64   c  and W 64   d , respectively. 
     Therefore, compared with the second embodiment, the suspension wires  2   a ,  2   b ,  2   c  and  2   d  are fixed to the suspension-wire support base  10  at higher positional accuracy, in the second modification. 
     The first and second modifications can also be applied to the first embodiment. 
     It is further understood by those skilled in the art that the foregoing descriptions are preferred embodiments and their modifications of the disclosed device and that various changes and further modifications may be made in the invention without departing from the sprit and scope thereof. 
     As disclosed above in detail, the present invention provides an optical pickup with higher positional accuracy for suspension wires fixed to a suspension-wire support base.