Abstract:
An optical pickup includes: a slide base, having: a first surface; and a second surface; a first substrate fixed to the first surface; a standing frame disposed on the second surface; a second substrate facing the standing frame; a laser diode operable to emit a laser beam to the disk and disposed in the standing frame; an optical, element supported by the second substrate and adapted to receive a reflected beam; a flexible flat cable. The flexible flat cable is bent so that one end portion of the flexible flat cable is connected to the second substrate. A curved portion is formed with a slit elongated in a longitudinal direction of the flexible flat cable and defines an outer portion and an inner portion. A width of the inner portion is narrower than a width of the outer portion.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an optical pickup that, is used in a disc device (for example, a DVD recorder, a DVD player, or the like), and more particularly, a disc device capable of preventing a read error by maintaining three-dimensional adjustment and rotation adjustment of a photo detector over a long period. 
         [0003]    2. Description of the Related Art 
         [0004]    An overview of an optical pickup will be described with reference to  FIG. 4 , In the optical pickup, a slide base  2  is engaged with, a pair of left and right guide rails  1  disposed along the radial direction pf a disc D to be able to reciprocate. In addition, between surface and bottom sides of the slide base  2 , a main substrate  3  formed of a printed circuit board is fixed to one side, and a standing frame  2 A is integrally formed or the other side. In the standing frame  2 A, a photo detector PD 1 , a light intensity detector PD 2 , and a laser diode LD are positioned to be fixed. In addition, within the standing frame  2 A, a standing mirror M and a half mirror HM are disposed, and an actuator  4  having an objective lens OL is disposed on one side of the slide base  2 . 
         [0005]    Hereinafter, the sequence of reading information will be described. The disc D is rotated at high speed and the actuator  4  is driven such that the objective lens OL is moved in a focus direction along a spindle  4   a  disposed in the actuator  4  and the objective lens OL is moved in the tracking direction around the spindle  4   a . Then, a laser beam a emitted from the laser diode LD is reflected by the half mirror HM and the standing mirror M, and is transmitted through the objective lens OL to be projected onto the disc D. Then, reflection light b is transmitted through the objective lens OL, reflected by the standing mirror M, transmitted through the half mirror HM, and received by the photo detector PD 1 , so that information recorded in the disc D is read out and the intensity of the laser beam a is detected by the light intensity detector PD 2 . 
         [0006]      FIGS. 5 to 8B  show an example of a general optical pickup.  FIG. 5  is ,a perspective view of the general optical pickup.  FIG. 6  is a plan view of major parts of the general optical pickup.  FIG. 7  is a front view of the major parts.  FIG. 8A  is a development view of a photo, detector conducting wire of the general pickup.  FIG. 8B  is a view along arrow D-D of  FIG. 3A . 
         [0007]    As shown in  FIG. 5 , the laser diode LD is fitted in a through hole, which is formed by perforating a center portion of a holder  6  made of a metal block, to be fixed, and an end portion of a laser diode conducting wire  8  formed of a flexible flat cable that is soldered to a terminal shaft  7  of the laser, diode LD is soldered to the main substrate  3 . 
         [0008]    As shown in  FIGS. 5 to 7 , the photo detector PD 1  is formed by attaching an optical element  11  formed of a photo diode to a support substrate  10  formed of a printed circuit board. The photo detector PD 1  is connected to the main substrate  3  through the photo detector conducting wire  12  formed of a flexible flat cable. The structure of the light intensity detector ED 2  is the same, as that, of the photo detector PD 1 . The light intensity detector PD 2  is connected to the main substrate  3  through a light intensity detection conducting wire  13  formed of a flexible flat cable. 
         [0009]    The sequence of fixing the photo detector PD 1  will now be described. The photo detector EDI is three-dimensionally adjusted in front and rear directions X, in left and right directions Y, and upper and down directions Z with respect to the standing frame  2 A, and rotation adjustment T for the photo detector PD 1  is performed. Then, by injecting an adhesive agent.  14  such as an ultraviolet curable adhesive agent between the standing frame  2 A and the support substrate  10 , the photo detector PD 1  is fixed to the standing frame  2 A. 
         [0010]    As shown in  FIGS. 8A and 8B , the photo detector conducting wire  12  is formed in an approximate “n” shape by a center portion  12   a , one end portion  12   b  that extends from the center portion  12   a  at a predetermined tilt angle (in this example, 45°) in one direction, and the other end portion  12   c  that extends from the center portion  12   a  at a predetermined tilt angle (in this example, 90°) in another direction. In the inner and outer edges of the end portions  12   b  and  12   c , a plurality of (in this example, seven for each edge) lands  16  is formed, and lands  16  disposed in both the end, portions  12   b  and  12   c  are connected together though a plurality of (in this example  14 ) connect ion wires  17  that pass through the center portion  12   a.    
         [0011]    The sequence of connecting the photo detector conducting wire  12  will now be described. As shown in  FIGS. 6 and 7 , the lands  16  disposed in the one end. portion  12   b  are soldered to lands  18  of the main substrate  3 , the other end portion  12   c  is bent to rise in the boundary K between the center portion  12   a  and the other end portion  12   c , and the lands  16  of the other end portion  12   c  are spidered to the lands  18  of the support substrate  10 , as disclosed in Japanese Patent Publication No, 2000-331372. 
         [0012]    In the above-described configuration, the photo detector conducting wire  12  is formed of a flexible flat cable having a large width. Accordingly., when the other end portion  12   c  thereof, is bent to stand in the boundary K, a strong pulling force P is generated along the outer edge of the photo detector conducting wire  12  from the boundary K, and a strong compressing force F is generated along the inner edge of the photo detector conducting wire  12 . Thus the strong pulling force P and the strong compressing force F are applied to the adhesive, agent  14  that supports the photo detector, and the adhesive agent  14  is deformed in a case where the adhesive agent is exposed, in a high-temperature environment such as a curing process or a warehouse. As a result, the three-dimensional, adjustment XYZ and rotation adjustment of the photo detector PD 1  may be performed incorrectly, and thereby there is a possibility of generation of a read error. 
       SUMMARY 
       [0013]    It is therefore, one advantageous aspect of the invention to provide an optical pickup capable of preventing a read error by maintaining the three-dimensional adjustment and rotation adjustment of the photo detector for a long time. 
         [0014]    According to one aspect of the present invention, there is provided an optical pickup including a slide base adapted to move along a radial direction of a disc and having a first surface; and a second surface; a first substrate fixed to the first surface and comprising a printed circuit board; a standing frame, disposed oh the second surface;, a second substrate facing the standing frame and comprising a printed circuit board; a laser diode operable, to emit a laser beam to the disk and disposed in the standing frame; an optical element supported by the second substrate and adapted to receive a light beam reflected, from the disk; and a flexible flat cable including a first end portion; a second end portion; and a curved portion disposed between the first end portion arid the second end portion, wherein: the first end portion is connected to the first substrate; the flexible flat cable is bent so that the second end portion connected to the second substrate; the curved portion, is formed with a slit elongated in a longitudinal direction of the flexible flat cable and defining an outer portion and an inner portion; and a width of the inner portion is narrower than a width of the outer portion. 
         [0015]    According to the above, the pulling force and the compressing force that are applied to the flexible flat cable are dispersed to both inner and outer conducting wires of the flexible flat cable by dividing the center portion of the flexible flat cable into two including the outer conducting wire and the inner conducting wire. In addition, since the width of the inner conducting wire is set to be smaller than that of the outer conducting wire, the inner conducting wire can be easily bent in correspondence with a decrease in the width of the inner conducting wire, and thereby the pulling force and the compressing force that are applied to the inner conducting wire decrease. Accordingly, the pulling force and the compressing force that are applied to the inner conducting wire do not act on the adhesive agent that supports the photo detector, and thereby the adhesive agent is not deformed even when the adhesive agent is exposed to a high-temperature environment such as a curing process or a warehouse. Therefore, a read error can be prevented by maintaining the three-dimensional adjustment and rotation adjustment of the photo detector for a log time. 
         [0016]    The width of the outer portion may be 1.4 to 3 times wider than the width of the inner portion. Further, the width of the outer portion may be  1 . 5  to  2 . 5  times wider than the width of the inner portion. 
         [0017]    According to the above, when the ratio of the width of the outer conducting wire to that of the Inner conducting wire is smaller than 3 to 1, the width of the inner conducting wire, is sexually and accordingly the pulling force P and the compressing force F that are applied to the inner conducting wire rarely act on the adhesive agent that supports the photo detector. However, since the width of the Outer conducting wire .is increased in correspondence with the decrease in the Width of the inner conducting wire, the shape of the flexible flat cable is approximately the same as that of a general flexible; flat cable in which a slit is not formed. Accordingly., the pulling force and the compressing force that are applied to the outer conducting wire become considerably strong, and are applied to the adhesive agent that supports the photo detector. Therefore, the adhesive agent may be deformed in a case where the photo detector is exposed in a high-temperature environment such as a curing process or a warehouse;. As a result, the three-dimensional adjustment and rotation adjustment of the ephoto, detector may be performed incorrectly, and thereby there is a possibility of generation of a read error. 
         [0018]    When the ratio of the width of the Outer conducting wire to that of the inner conducting wire exceeds the ratio of 7 to 5 the width of the inner conducting wire is not quite different from that of the outer conducting wire. Accordingly, the shape of the flexible flat cable is approximately the same as that of a general photo detector in which the ratio of the width of the inner conducting wire to that of the outer conducting wire is 1 to 1. Thus, the pulling force and the compressing force that are applied to the inner conducting wire become considerably strong, and act on the adhesive agent: that supports the photo detector. Therefore, the adhesive agent is deformed in a case where the adhesive agent is exposed in a high-temperature environment such as a curing process or a warehouse, and there is the above-described defect, 
         [0019]    According to the above, the ratio of the width of the outer conducting Wire to that of the inner conducting wire is set: to be in the range of 3 to 1 to 7 to 5 (preferably in the range of 2.5 to 1 to 1.5 to ) , and the pulling force and the compressing force that are applied to the flexible flat cable are dispersed to both inner and outer conducting wires of the flexible flat cable by dividing the center portion of the flexible flat cable into two including the outer conducting wire and the inner conducting wife. In addition, since the width of the inner conducting wire is set to be appropriately smaller than that of the outer conducting wire, the inner conducting wire can be easily bent in correspondence with a decrease in the width of the inner conducting wire, and thereby the pulling force and the compressing force that are applied to the inner conducting wire decrease. Accordingly, the pulling force and the compressing force that are applied to the inner conducting wife do not act on the adhesive agent that supports the photo detector, and thereby the adhesive agent is not deformed even when the adhesive agent is exposed to a high-temperature, environment such as a curing process or a warehouse. Therefore, a read error can be prevented by maintaining the three-dimensional adjustment /and rotation adjustment of the photo detector for a log time. 
         [0020]    The width of the slit may fall within a range from 1 mm to 3 mm. Further, the width of the slit, may fall within a range, from 1.5 to 2.5 mm. 
         [0021]    According to the above, when the width of the slit is smaller than 1 mm, the width of the slit is too small, and both the inner and outer conducting wires way be brought into contact with each other in a case where the other end portion of the flexible flat cable is bent in the boundary, and thereby there is a possibility that remaining load is applied to the adhesive agent. 
         [0022]    On the other hand, when the width of the slit exceeds 3 mm, the width of the slit is too large, and accordingly a gap between the inner and outer conducting wires decreases in correspondence with an increase in the width of the slit. As a result, it is difficult, to appropriately dispose ;a plurality of connection wires in both the inner and outer conducting wires with a predetermined gap interposed therebetween. 
         [0023]    According to the third aspect of the invention, since the width of the slit is set to be in the range of 1 to 3 (preferably in the range of 1.5 to 2.5) mm, the width of the slit is an appropriate size. Accordingly, both the inner and outer conducting wires are not: brought into contact with each other in a case where the other end portion of the flexible flat cable is bent in the boundary. In addition, the widths of the inner and outer conducting wires are set to be large as possibly as can be, and therefore a plurality of connection, wires can be appropriately disposed in both the inner and outer conducting wires With a predetermined gap interposed therebetween. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0024]    Embodiment may be described in detail with reference to the accompanying drawings, in which: 
           [0025]      FIG. 1A  is a development view of a photo detector conducting wire of an optical pickup according to one embodiment of the present invention; 
           [0026]      FIG. 1B  is a diagram along arrow A-A of  FIG. 1A ; 
           [0027]      FIG. 2A  is a development view of a photo detector conducting wire of an optical pickup according to another embodiment of the present invention; 
           [0028]      FIG. 2B  is a diagram along arrow B-B of  FIG. 2A ; 
           [0029]      FIG. 3A  is a development view of a photo detector conducting wire of an optical pickup according to another embodiment of the present, invention; 
           [0030]      FIG. 3B  is a diagram along arrow C-C of  FIG. 3A ; 
           [0031]      FIG. 4  is a schematic plan view of an optical pickup; 
           [0032]      FIG. 5  is a perspective view of an example of an optical pickup; 
           [0033]      FIG. 6  is la plan view of major parts of the optical pickup; 
           [0034]      FIG. 7  is a front view of the major parts; 
           [0035]    FIG..  8 A is a development view of a photo detector conducting wire of the optical pickup; 
           [0036]      FIG. 5B  is a view along arrow D-d of  FIG. 8A ; 
           [0037]      FIG. 9   ft  is a development view of an example of a photo detector conducting wire; and 
           [0038]      FIG. 9B  is a view along arrow E-E of  FIG. 9A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]    As shown in  FIG. 9A  that is a development view of a photo detector conducting wire and  FIG. 9B  that is a view along arrow E-E. of  FIG. 9A , a method of dispersing a pulling force P and a compressing force F to both an inner and outer conducting wires  12 A and  12 B by forming a slit  20  along a longitudinal direction of a conducting wire  12  from a center portion  12   a  of the photo detector conducting wire  12  to an other end portion  12   c . through a boundary K and dividing the center portion  12   a  of the photo detector conducting wire  12  into two including the outer conducting wire  12 A and the inner conducting wire  12 B may be considered. However, in such a case, the ratio of a width h 1  of the outer conducting wire  12 A to s width h 2  of the inner conducting wire  12 B is 1 to 1, the width h 2  of the inner conducting wire  12 B is large, and the inner conducting wire  12 B is bent, at a steep angle. Accordingly, the pulling force P and the compressing force F that are applied to the inner conducting wire  12 B are considerably strong, and are applied to the adhesive agent  14  that supports a photo detector PD 1 . 
         [0040]    Therefore, according to an exemplary embodiment of the present invention,  FIGS. 1A and 1B  show major parts of an optical pickup according to a .first embodiment of the present invention.  FIG. 1A  is a development view of a photo detector conducting wire of the optical pickup.  FIG. 1B  is a view along arrow A-A of  FIG. 1A . 
         [0041]    As shown in  FIGS. 1A  and IB, a center portion  12   a  of the photo detector conducting wire  12 . Is divided into two including an outer conducting wire  12 A and an inner conducting wire  12 B by forming a slit  21  having a predetermined width t along the longitudinal direction the conducting wire  12  from the center portion  12   a  of the photo detector conducting wire  12  to the other end portion  12   c  through a boundary K. In addition, the ratio of the width h 1  of the outer conducting wire  12 A to the width h 2  of the inner conducting wire  12 B is set to 3 to 1. Since other configurations are approximately the same as those shown in FIGS. 4 to 7, a same reference number is assigned to a same portion, and a description thereof is omitted here. 
         [0042]    To describe an example of specific measurements, the width. H of the center portion  12   a  is 1.4 mm, the width t of the slit  21  is 2 mm, the width h 1  of the outer conducting wire  12 A is 9 mm, and the width h 2  of the inner conducting wire  12 B is 3 mm. 
         [0043]      FIGS. 2   h  and  2 B show major parts of an optical pickup according to a second embodiment of the present invention.  FIG. 2A  is a development view of a photo detector conducting wire of the optical pickup, and  FIG. 2B  is a view along arrow B-B of  FIG. 2A . 
         [0044]    As shown in  FIGS. 2A and 2B , the ratio of the width h 1  of the outer conducting wire  12 A to the width h 2  of the inner conducting wire  12 B is set to 2 to 1. Since other configuration&#39;s are approximately the same as those shown in  FIGS. 1A and 1B , a same reference number is assigned to a same portion, and a description thereof is omitted here. 
         [0045]    To describe an example of specific measurements, the width H of the center portion  12   a  is 14 mm, the width t of the slit  21  is 2 mm, the width hi of the outer conducting wire  12 A is 8 mm, and the width h 2  of the inner conducting wire  12 B is 4 mm. 
         [0046]      FIGS. 3A and 3B  show major parts of an optical pickup according, to a third embodiment of the present invention.  FIG. 3A  is a development view of a photo detector conducting wire of the optical pickup, and  FIG. 3B  is a view along arrow C-C of  FIG. 3A . 
         [0047]    As shown in  FIGS. 3A and 3B  the ratio of the width h 1  of the outer conducting wire 12A to the width h2 of the inner conducting wire  12 B is set to 7 to 5. Since other configurations are approximately the same as those shown in  FIGS. 1A and 1B , a same reference number is assigned to a same portion, and a description thereof is omitted here. 
         [0048]    To describe an example of specific measurements, the width H of the center portion  12   a  is    14   mm, the width t of the slit  21  is 2 mm, the width h 1  of the outer conducting wire  12 A is 7 mm, and the width h 2  of the inner conducting wire  12 B is 5 mm. 
         [0049]    In the above-described configuration, μgs.  1 A and  1 B show a case where the ratio of the width hi of the outer conducting wire  12 A to the width h 2  of the inner conducting .wire  12 B is 3 to 1 (in a detailed example, 9 mm to 3 mm) . When the ratio is smaller than 3 to 1, that is, when the width h 2  of the inner conducting wire  12 B decreases from a state shown in  FIGS. 1A and 1B , the pulling force P and the compressing force F that are applied to the inner conducting wire  12 B do not act oh the adhesive agent  14  that supports, the photo detector PDI. However, since the width hi of the outer conducting wire  12 A is increased in correspondence with a decrease in the width h 2  of the inner conducting wire  12 B, the shape of the photo detector conducting wire is approximately the; same as the shape of a general photo detector conducting wire shown in  FIGS. 8A and 8B . Accordingly, the pulling force P ;and the compressing force F that are applied, to the outer conducting wire  12 A become, considerably strong, and act on the adhesive agent  14  that supports the photo detector PDI. Therefore, the adhesive agent 1:4 is deformed in a case where the adhesive agent is exposed in a high-temperature environment such as a curing process or. a warehouse. As a result, the three-dimensional adjustment XYZ and rotation adjustment T of the photo detector PD 1  may be performed incorrectly, and thereby there is a possibility of generation of a read error. 
         [0050]      FIGS. 3A and 3B  show a case, where the ratio of the width h 1  of the outer conducting wire  12 A to the width K-2 of the inner conducting wire  12 B is 7 to 5 (in a detailed example, 7 mm to 5 mm) . When the ratio exceeds the ratio of 7 to 5, that is, when, the width h 2  of the inner conducting wire  12 B is increased from a state shown in  FIGS. 3A and 3B , the width h 2  of the inner conducting wire  12 B is not quite different from the width hi of the outer conducting wire  12 A. Accordingly, the shape of the photo detector conducting wire is approximately the same as the shape of a general photo detector conducting wire shown in  FIGS. 9A and 9B . Thus, the pulling force p and the compressing force F that are applied to the inner conducting wire  12 B become, considerably strong, and act on the adhesive agent  14  that supports the photo detector pd 1 . Therefore, the adhesive agent  14  is deformed in a case where the adhesive agent is exposed to a high-temperature environment such as a curing process or a warehouse, and accordingly, there is the above-described defect. 
         [0051]      FIGS. 2A and 2B  show a case where the ratio of the width h 1  of the outer conducting wire  12 A to the width h 2  of the inner conducting wire  12 B is 2 to 1 (in a detailed example, 8 mm to 4 mm) as an example that is the most appropriate to the present invention. It is preferable that the ratio is in the range of 2.5 to 1 (in the detailed example, 8.6 mm to 3.4 mm) to 1.5 to 1 (in the detailed example, 7.2 mm to 4.8 mm). 
         [0052]    According to an embodiment of the present Invention, the ratio of the width h 1  of the outer conducting wire  12 A to the width h 2  of the inner conducting wire  12 B is set to be in the range of 3 to 1 (see  FIGS. 1A and 1B ) to 7 to 5 (see  FIGS. 3A and 3B ) (preferably in the range of 2.5 to 1 to 1.5 to 1 (see. FIGS.    2   A and    2   B) ) . In addition, by dividing the center portion  12   a  of the photo detector conducting wire  12  into two including the outer conducting wire  12  A and the inner conducting wife  12 B, the pulling force P and the compression force. F that are applied to the photo detector conducting wire  12  are dispersed to both the inner and outer conducting wires  12 A and  12 B. In addition, the width h 2  of the inner conducting wire  12 B is set to be appropriately smaller than the width h 1  of the outer conducting wire  12 A. Accordingly, the inner conducting wire  12 B can be easily bent in correspondence with a decrease in the width h 2 , and thus the pulling force P and the compressing force F that are applied to the inner conducting wire decrease. As a result, the pulling force P and the compressing force F that are applied to the inner conducting wife  12 B scarcely act on the adhesive agent  14  that supports the photo detector PDI, and accordingly, the adhesive agent  14  is not deformed in a case where the adhesive agent is exposed to a high-temperature environment such as a curing process or a warehouse. Therefore, the three-dimensional adjustment XYZ and rotation adjustment T of the photo detector PD 1  can be maintained for a long time, and thus a read error can be prevented. 
         [0053]    In  FIGS. 1A to 3B , a ease where, the width t of the slit  21  is set to 2 mm. However, when, the width t of the slit  21  is smaller than 1 mm., the width t of the slit  21  is too small. Accordingly, both the inner and outer-conducting wires  12 A and  12 B may be brought into contact with each other in a case where the other end portion  12   c  of the photo detector conducting wire  12  is bent in the boundary K, and thereby there is a possibility that remaining load is applied to the adhesive agent  14 . 
         [0054]    When the width t of the slit  21  exceeds 3 mm, the width t of the slit  21  is too large. Thus, the width h 1 +h2 of both the. conducting wires  12 A and  12 B is decreased in correspondence with an increase in the width of the slit. Therefore, it is difficult, to appropriately dispose a plurality of the connection wires  17  in both the inner and outer conducting wires  12 A and  12 B with a predetermined gap interposed therebetween. 
         [0055]    According to an embodiment of the present invention, since the width t of the slit  21  is set in the range of 1 to 3(preferably in the range of 1.5 to 2.) mm, the width t of the slit  21  is appropriately set. Accordingly, both the inner and outer conducting wires  12 A and  12 B are hot brought into contact with each other in a case where the other end portion  12   c  of the photo detector conducting wire  12  is bent in the boundary K. In addition, the width h 1 +h 2  of both the inner and outer conducting wires  12 A and  12 B can be set large as possibly as can be, and accordingly, a plurality of connection, wires  17  can be appropriately disposed in both the inner and outer conducting wires  12 A and  12 B with a predetermined gap interposed therebetween.