Abstract:
An optical pickup assembly having: a pickup base; an actuator installed in the pickup base, and having a blade, on which an objective lens to radiate light onto a disc is mounted; a cover, installed to surround the actuator, and regulating a range of movement of the blade; and an attenuator protruding from an inside of the cover, splitting an eddy current occurring during rotation of the disc into a plurality of small eddy currents, and attenuating a disturbance acting on the blade.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the priority of Korean Patent Application No. 2003-100425, filed on Dec. 30, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an optical pickup assembly, and more particularly, to an optical pickup assembly having an actuator to reduce an eddy current caused by air flow occurring during rotation of a disc.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, an optical pickup assembly is a device that records and/or reproduces information by radiating light onto a disc (recording medium) through an objective lens and/or by receiving light reflected from the recording medium.  
         [0006]      FIG. 1  is an exploded perspective view schematically showing the structure of a conventional optical pickup assembly,  FIG. 2  is a side view showing an eddy current occurring in a conventional optical pickup assembly during rotation of a disc, and  FIG. 3  is a plane view showing the eddy current shown in  FIG. 2 .  
         [0007]     Referring to  FIG. 1 , the optical pickup assembly includes: a pickup base  11  installed to slide in a radial direction of a disc; an actuator  12  having a blade  17 , which is supported by a plurality of suspensions  15  in a holder  14  fixed in a yoke plate  13 , and on which an objective lens  16  is mounted; magnets  18 , which are installed on the yoke plate  13  by a predetermined gap and track and/or focus the blade  17 ; and a cover  19 , which is installed to surround the actuator  12 , has a hole  19   a  that is positioned on an upper side of the cover  19 , through which light irradiated from the objective lens  16  passes, and which restricts a movement range of the blade  17  in the radial direction of the disc.  
         [0008]     The cover  19  restricts the movement range of the blade  17 , which is fixedly installed in the yoke plate  13  and moves in the radial direction of the disc by interaction between the cover  19  and the magnets  18 . If the optical pickup assembly does not include the cover  19 , the objective lens  16  may be damaged while contacting the disc, or a scratch may occur on a surface of the disc.  
         [0009]     Referring to  FIGS. 2 and 3 , information recording and/or reproduction is performed using the optical pickup assembly when the optical pickup assembly makes a reciprocating movement in the radial direction of a disc D while maintaining a predetermined working distance between the disc D and the actuator  12 .  
         [0010]     Thus, air flow having a uniform speed difference occurs between the disc D and the actuator  12  when the disc D is rotated. In other words, the speed of air adjacent to the disc D is similar to a rotation speed of the disc D, but air speed decreases closer to the actuator  12 . The speed difference of the air flow causes an eddy current S on the actuator  12 .  
         [0011]     As the rotation speed of the disc D increases, a distance between the disc D and the actuator  12  decreases. As a result, the speed of the air flow increases according to Bernoulli&#39;s theorem, and the eddy current S increases.  
         [0012]     The eddy current flows into the hole  19   a  positioned on the upper side of the cover  19 , and acts on the blade  17  as an asymmetrical force or disturbance. As a result, the blade  17  vibrates upward and downward and disturbs a focusing or tracking operation of the blade  17 , so that information recording and/or reproduction is not smoothly performed.  
         [0013]     In particular, if a frequency generated by the eddy current S and a natural frequency of the actuator  12  cause resonances, disturbance on the actuator  12  increases.  
       SUMMARY OF THE INVENTION  
       [0014]     An aspect of the present invention provides an optical pickup assembly to reduce a disturbance that occurs during rotation of a disc and affects an actuator.  
         [0015]     According to an aspect of the present invention, there is provided an optical pickup assembly. The optical pickup assembly includes a pickup base; an actuator installed in the pickup base, and having a blade on which an objective lens radiating light onto a disc is mounted; a cover, installed surrounding the actuator, and regulating a range of movement of the blade; and an attenuator protruding from an inside of the cover, splitting an eddy current occurring during rotation of the disc into a plurality of small eddy currents, and attenuating a disturbance acting on the blade.  
         [0016]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows, and in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which:  
         [0018]      FIG. 1  is an exploded perspective view schematically showing a structure of a conventional optical pickup assembly;  
         [0019]      FIG. 2  is a side view showing an eddy current occurring in the optical pickup assembly of  FIG. 1  during rotation of a disc;  
         [0020]      FIG. 3  is a plane view showing the eddy current shown in  FIG. 2 ;  
         [0021]      FIG. 4  is a perspective view schematically showing a structure of a disc drive adopting an optical pickup assembly according to an embodiment of the present invention;  
         [0022]      FIG. 5  is an exploded perspective view showing an optical pickup actuator having an attenuator according to a first embodiment of the present invention;  
         [0023]      FIG. 6  is a cross-sectional view taken along line I—I of  FIG. 5 ;  
         [0024]      FIG. 7  is an exploded perspective view showing an optical pickup actuator having an attenuator according to a second embodiment of the present invention;  
         [0025]      FIG. 8  is a cross-sectional view taken along line II—II of  FIG. 7 ;  
         [0026]      FIG. 9  is a plane view showing an eddy current occurring when the attenuator according to the first embodiment of the present invention is provided inside a cover;  
         [0027]      FIG. 10  is a perspective view showing a cover having an attenuator according to a third embodiment of the present invention;  
         [0028]      FIG. 11  is a perspective view showing a cover having an attenuator according to a fourth embodiment of the present invention; and  
         [0029]      FIG. 12  is a plane view showing an eddy current occurring when an attenuator according to the third embodiment of the present invention is provided inside a cover.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]     Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments described below explain the present invention by referring to the figures.  
         [0031]     Referring to  FIG. 4 , a disc drive  100  includes: a main frame  110 ; a tray  120 , which is installed to move in and out the main frame  110 , and on which a disc D is seated; and a base chassis  130 , which is supported by a subframe  131  that can be pivoted in upward and downward directions of the main frame  110 .  
         [0032]     A turntable  132  and an optical pickup assembly  140  are installed in the base chassis  130 . The disc D is transported into the main frame  110  by the tray  120 , and is seated on the turntable  132 . The turntable  132  is rotated by a spindle motor (not shown). The optical pickup assembly  140  slides in a radial direction of the disc D seated on the turntable  132 , records data on the disc D, and/or reproduces recorded data.  
         [0033]     Referring to  FIG. 5 , the optical pickup assembly  140  includes: a pickup base  141 ; an actuator  142  having a plurality of magnets  148  fixedly installed on a yoke plate  143  by a predetermined gap, the yoke plate  143  being seated on the pickup base  141 ; a plurality of suspension wires  147 , one end of each of the suspension wires  147  being fixed in a holder  144  fixed on one side of the yoke plate  143 , and other ends of each of the suspension wires  147  supporting a blade  145 , on which the objective lens  146  is mounted; a cover  149  that is installed to surround the actuator  142 , and that regulates the upward and downward movement range of the blade  145  and has a through hole  149   a  that is formed on an upper side of the cover  149 , through which light passes; and an attenuator  150 , which is provided inside the cover  149 , and splits an eddy current generated during rotation of the disc D into a plurality of small eddy currents.  
         [0034]     Referring to  FIG. 6 , the attenuator  150 , according to a first embodiment of the present invention, has a plurality of projections  151 , which are arranged in a single row on one of inner sidewalls  149   b , and are spaced a predetermined distance apart from the upper side of the cover  149 . According to one embodiment the attenuator  150  is installed on any one of the inner sidewalls  149   b . According to one embodiment, the projections  151  are positioned on the inner sidewall  149   b  parallel to a rotation direction of the disc D.  
         [0035]     Referring to  FIGS. 7 and 8 , an attenuator  160  according to a second embodiment of the present invention has a plurality of projections  161 , which are arranged on one of the inner sidewalls  149   b , and are spaced predetermined distances apart from the upper side of the cover  149 . The projections  161  are arranged in a plurality of rows in zigzags. In other words, first and second rows of projections  161  are positioned on one of the inner sidewalls  149   b  of the cover  149 , such that the first row of projections  161  is spaced a first predetermined distance from the upper side of the cover  149 , and the second row of projections  161  is spaced a second predetermined distance from the upper side of the cover  149 . Additionally, according to one embodiment, the projections  161  alternate between the first and second rows of projections. In other words, for example, in a plan view, the projections  161  appear to be a single row, but a first projection is disposed in the first row, a second projection  161  is disposed in the second row, a third projection  161  is disposed in the first row, etc. Put another way, the projections  161  are arrayed in a lateral direction alternating between the first and second rows.  
         [0036]     In the above-described embodiments, the respective projections  151  and  161  have a triangular shape. According to alternative embodiments, the respective projections  151  and  161  have a rectangular shape. According to other embodiments, the respective projections  151  and  161  have a trapezoidal shape. According to yet other embodiments, the respective projections  151  and  161  have a conical shape. According to still yet other embodiments, the respective attenuators  150  and  160  have a variety of shapes that protrude from the inner sidewalls  149   b  of the cover  149 , to form a plurality of small eddy currents.  
         [0037]     The projections  151  and  161  are positioned on one of the inner sidewalls  149   b  of the cover  149  parallel to a rotation direction of the disc D, so that the attenuators  150  and  160  reduce the size of an eddy current occurring during rotation of the disc D and attenuate an effect thereof.  
         [0038]     Referring to  FIG. 9 , when the disc D is rotated within the cover  149  having the attenuator  150 , and air flows, the eddy current S is generated. In this case, unlike an eddy current occurring in a conventional cover ( FIG. 3 ), the eddy current S collides with the plurality of projections  151  and is split into a plurality of small currents. In other words, the eddy current S, caused by air flow during rotation of the disc D, collides with the projections  151  in the cover  149 , and is split into a plurality of small eddy currents S while being disturbed in a space between the adjacent projections  151 .  
         [0039]      FIG. 10  is a perspective view showing a cover having an attenuator according to a third embodiment of the present invention,  FIG. 11  is a perspective view showing a cover having an attenuator according to a fourth embodiment of the present invention, and  FIG. 12  is a plane view showing an eddy current occurring when an attenuator according to the third embodiment of the present invention is provided inside a cover.  
         [0040]     Referring to  FIG. 10 , a plurality of projections  151  having the same shape as the shape shown in  FIG. 5  are arranged in respective rows disposed on opposed inner sidewalls  149   b  of the cover  149  to face one another.  
         [0041]     Referring to  FIG. 11 , a plurality of projections  161  having the same shape as the shape shown in  FIG. 7  are arranged in respective rows in zig-zags, disposed on opposed inner sidewalls  149   b  of the cover  149  to face one another. In other words, a plurality of first rows of projections  161  and a plurality of second rows of projections  161  are positioned on the opposed inner sidewalls  149   b  of the cover  149 , such that the first rows of projections  161  are spaced a first predetermined distance from the upper side of the cover  149 , the second rows of projections  161  are spaced a second predetermined distance from the upper side of the cover  149 , the respective first rows face each other, and the respective second rows face each other. Additionally, according to one embodiment, the projections  161  alternate between the first and second rows of projections. In other words, for example, in a plan view, the projections  161  appear to be single rows on the opposed inner sidewalls  149   b , but on both of the opposed inner sidewalls  149   b , a first projection is disposed in the first row, a second projection  161  is disposed in the second row, a third projection  161  is disposed in the first row, etc. Put another way, on both opposed inner sidewalls  149   b , the projections  161  are arrayed in a lateral direction alternating between the first and second rows.  
         [0042]     Referring to  FIG. 12 , the plurality of projections  151  are arranged to face one another so that the eddy current S occurring during rotation of the disc D collides with the projections  151  positioned on the opposed inner sidewalls l 49   b , and is split into a plurality of small eddy currents S more easily than in the first and second embodiments.  
         [0043]     The plurality of small eddy currents S formed by the projections  151  and  161  deteriorate due to a force being dispersed on the blade ( 145  of  FIG. 5 ), as opposed to a single large eddy current, so that the small eddy currents have little effect on the adjustment of the blade ( 145  of  FIG. 5 ) when using the actuator  142 .  
         [0044]     As is described above, in the optical pickup assembly and the disc drive adopting the same according to embodiments of the present invention, the attenuator  150 / 160  is provided inside the cover  149 , such that an eddy current caused by air flow occurring during rotation of the Disc is split into a plurality of small eddy currents, to attenuate the effect on the adjustment of the blade  145 .  
         [0045]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.