Abstract:
An optical disc apparatus includes a main guide shaft and a subsidiary guide shaft disposed so as to guide movement of a sliding base which holds an optical pickup. The optical pickup enables information recording and reproducing operations on an optical disc. The main guide shaft and the subsidiary guide shaft are configured so as to suppress vibrational resonance caused between the main guide shaft and the subsidiary guide shaft.

Description:
INCORPORATION BY REFERENCE  
       [0001]     The present application claims priority from Japanese application 2005-352554 filed on Dec. 6, 2005, the content of which is hereby incorporated by reference into this application.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates generally to optical disc apparatuses. More particularly, the invention relates to an optical disc apparatus adoptable for compact discs (CDs), digital versatile discs (DVDs), Blu-ray discs (BDs), and the like, and having a vibration insulator for preventing signal read/write errors from occurring during recording and reproduction.  
         [0003]     Conventional optical disc apparatuses have some vibration insulator for preventing signal read/write errors from occurring during recording and reproduction.  
         [0004]     For example, the types of vibration insulators employed in optical disc apparatuses for CDs, DVDs, or the like, include one in which the guide shafts themselves and support sections for supporting the guide shafts are each formed of resin.  
         [0005]     A main guide shaft and a subsidiary guide shaft exist as the guide shafts that are main constituent elements of an optical disc apparatus. In conventional types of optical disc apparatuses, for reasons of the moving stroke of an optical pickup, both the main guide shaft and the subsidiary guide shaft are typically of the same length. In addition, in terms of cost, the main guide shaft and the subsidiary guide shaft are usually made of the same metallic material and both are usually formed into the same shaft shape.  
         [0006]     In recent years, high positioning accuracy has been required for optical disc apparatuses of high recording capacity, such as Blu-ray disc apparatuses. These optical disc apparatuses, compared with conventional ones, are required to have high positioning accuracy particularly in a focusing direction and in a tracking direction.  
         [0007]     For example, Japanese Patent Laid-open No. 2000-311366 concerned with this technical field discloses a technique for constructing an optical disc apparatus including first and second bearings supported by a main guide shaft, and a third bearing supported by a subsidiary guide shaft; wherein a supporting point of the third bearing is disposed on a straight line which connects a midpoint on a line segment between supporting points of the first and second bearings and a center of gravity of a sliding base including an optical pickup.  
         [0008]     For the conventional optical disc apparatus described above in the “Background of the Invention”, however, the disclosure of the technique in Japanese Patent Laid-open No. 2000-311366, for example, does not contain information on a method of preventing or controlling the vibration of the optical pickup or the vibrational resonance of the guide shafts. There has been, therefore, a problem in that the technique alone does not suffice to obtain a sufficient vibration-insulating effect.  
         [0009]     Despite the fact that as described above, compared with that of the conventional optical disc apparatuses, high positioning accuracy in the focusing direction and in the tracking direction is required particularly for optical disc apparatuses of high recording capacity, such as Blu-ray disc apparatuses, effective measures for preventing or controlling the vibrational resonance of the main guide shaft and the subsidiary guide shaft have not been taken in conventional techniques.  
         [0010]     More specifically, for the conventional optical disc apparatuses, both the main guide shaft and the subsidiary guide shaft are set to the same length for reasons of the stroke of the optical pickup which moves between the inner and outer peripheral edges of a disc. In addition, in terms of cost, the main guide shaft and the subsidiary guide shaft are made of the same metallic material and both are formed into the same shaft shape. Hence, during information recording on or reproduction from the optical disc, that is, during movement of the sliding base itself, the natural frequency of the main guide shaft system including the optical pickup, and the natural frequency of the subsidiary guide shaft system take the same value, for which reason, vibrational resonance occurs between the main guide shaft system and the subsidiary guide shaft. This problem, in turn, causes a further problem in that the vibrational characteristics of the optical pickup in the focusing direction deteriorate under the conditions of those frequencies, and these problems are becoming increasingly prominent in recent years.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention has been made in view of the above problems associated with the conventional art, and an object of the invention is to provide an optical disc apparatus that can suppress the vibrational resonance caused between a main guide shaft and a subsidiary guide shaft, and prevent an optical pickup from losing control of its focusing and control of its tracking.  
         [0012]     Another object of the present invention is to provide an optical disc apparatus which, without significantly changing the conventional manufacturing method, can suppress the vibrational resonance caused between a main guide shaft and a subsidiary guide shaft, and prevent an optical pickup from losing control of its focusing and control of its tracking control.  
         [0013]     Yet another object of the present invention is to provide an optical disc apparatus which, even if a main guide shaft and a subsidiary guide shaft are both constructed of the same material, can suppress the vibrational resonance caused between the main guide shaft and the subsidiary guide shaft, and prevent an optical pickup from losing its focus control and its tracking control.  
         [0014]     After making energetic studies in consideration of the above problems to be solved, the present inventors arrived at the conclusion that the vibrational resonance of the main guide shaft and subsidiary guide shaft for guiding the sliding base which holds the optical pickup can be suppressed by assigning differences in cross-sectional shape and cross-sectional area between both shafts.  
         [0015]     That is to say, the present invention provides an optical disc apparatus that includes rotating means for rotationally driving a mounted disc, a chassis for securing the rotating means, a main guide shaft and subsidiary guide shaft fixed to the chassis approximately in parallel to a radial direction of the disc, and a sliding base for holding an optical pickup which performs information recording and reproducing operations on the disc, a first bearing and a second bearing attached to the sliding base being in engagement with the main guide shaft and the subsidiary guide shaft, respectively, to render the sliding base movable in the radial direction of the disc with respect to the chassis; wherein the main guide shaft and the subsidiary guide shaft are of a cylindrical shape and the main guide shaft has a cross-sectional shape different from that of the subsidiary guide shaft.  
         [0016]     Constructing the optical disc apparatus in this way makes it possible to assign a difference in natural frequency between the main guide shaft and the subsidiary guide shaft due to a difference between cross-sectional coefficients of both shafts. Consequently, the vibrational resonance caused between the main guide shaft and the subsidiary guide shaft can be suppressed, which realizes the optical disc apparatus having an ability to prevent the optical pickup from losing its focus control and its tracking control.  
         [0017]     The present invention provides another optical disc apparatus that includes rotating means for rotationally driving a mounted disc, a chassis for securing the rotating means, a main guide shaft and subsidiary guide shaft fixed to the chassis in a condition approximately parallel to a radial direction of the disc, and a sliding base for holding an optical pickup which performs information recording and reproducing operations on the disc, a first bearing and a second bearing attached to the sliding base being in engagement with the main guide shaft and the subsidiary guide shaft, respectively, to render the sliding base movable in the radial direction of the disc with respect to the chassis; wherein both the main guide shaft and the subsidiary guide shaft are of a cylindrical shape and the subsidiary guide shaft is of a hollow shaft cross-sectional shape.  
         [0018]     Constructing the optical disc apparatus in this way makes it possible to assign a difference in natural frequency between the main guide shaft and the subsidiary guide shaft due to a difference in cross-sectional coefficient between both shafts. Consequently, the vibrational resonance caused between the main guide shaft and the subsidiary guide shaft can be suppressed, which realizes the optical disc apparatus having an ability to prevent the optical pickup from losing its focus control and its tracking control.  
         [0019]     In any one of the above optical disc apparatuses according to the present invention, the subsidiary guide shaft has a diameter greater than that of the main guide shaft. In addition, a ratio between the cross-sectional coefficient of the subsidiary guide shaft and that of the main guide shaft is preferably at least 1.4.  
         [0020]     The present invention provides yet another optical disc apparatus that includes rotating means for rotationally driving a mounted disc, a chassis for securing the rotating means, a main guide shaft and subsidiary guide shaft fixed to the chassis in a condition approximately parallel to a radial direction of the disc, and a sliding base for holding an optical pickup which performs information recording and reproducing operations on the disc, a first bearing and a second bearing attached to the sliding base being in engagement with the main guide shaft and the subsidiary guide shaft, respectively, to render the sliding base movable in the radial direction of the disc with respect to the chassis; wherein the main guide shaft is of a cylindrical shape, the subsidiary guide shaft is of a cylindrical shape formed with a groove extending axially in a section at which the subsidiary guide shaft is kept free of engagement with the second bearing, and a plate-shaped member to be connected to the chassis is engaged with the groove.  
         [0021]     In the optical disc apparatus thus constructed, a vibration-absorbing action of the plate-shaped member makes it possible to suppress the vibrational resonance caused between the main guide shaft and the subsidiary guide shaft. The optical disc apparatus having an ability to prevent the optical pickup from losing its focus control and its tracking control can be realized as a result.  
         [0022]     As described above, any one of the optical disc apparatuses according to the present invention is effective in preventing a shift in relative position from occurring between the disc and the pickup, in suppressing the vibrational resonance of the guide shafts including the sliding base, and in preventing disc information recording/reproducing errors from occurring. Also, manufacturing processes for the conventional optical disc apparatuses can be used to realize the optical disc apparatus having the above advantageous effects, so this apparatus has an effect that it requires no additional equipment costs. In addition, this apparatus can be realized using the same material for the main guide shaft and the subsidiary guide shaft, so the apparatus has effects that it enhances reliability and that it can save materials costs. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     Other objects and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which:  
         [0024]      FIG. 1  is a plan view showing a total configuration of an optical disc apparatus according to a first embodiment of the present invention;  
         [0025]      FIG. 2  is a perspective view showing a configuration of a sliding base in the optical disc apparatus according to the first embodiment of the present invention;  
         [0026]      FIG. 3  is a sectional view that shows section A-B of a main guide shaft and subsidiary guide shaft in the optical disc apparatus according to the first embodiment of the present invention;  
         [0027]      FIGS. 4A and 4B  are explanatory views that show different deformation modes of guide shaft resonance in the optical disc apparatus according to the first embodiment of the present invention,  FIG. 4A  being an in-phase deformation mode diagram of first-order guide shaft resonance, and  FIG. 4B  being an antiphase deformation mode diagram of second-order guide shaft resonance;  
         [0028]      FIG. 5  is a graph representing the relationship between a cross-sectional coefficient ratio of the main guide shaft and subsidiary guide shaft in the optical disc apparatus according to the first embodiment, and amplitude of an optical pickup;  
         [0029]      FIG. 6  is a sectional view that shows section A-B of a main guide shaft and subsidiary guide shaft in an optical disc apparatus according to a second embodiment of the present invention;  
         [0030]      FIG. 7  is a configuration diagram showing a total configuration of an optical disc apparatus according to a third embodiment of the present invention;  
         [0031]      FIG. 8  is a sectional view that shows section C-D of a main guide shaft and subsidiary guide shaft in the optical disc apparatus according to the third embodiment of the present invention; and  
         [0032]      FIG. 9  is an assembly diagram of the subsidiary guide shaft in the optical disc apparatus according to the third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]     Preferred embodiments of an optical disc apparatus of the present invention will be described hereunder referring to the accompanying drawings. FIGS.  1  to  9  show embodiments of the present invention, in which figures, the sections assigned the same reference number or symbol denote the same constituent elements and each embodiment assumes the same in basic configuration and operation.  
       First Embodiment  
       [0034]      FIG. 1  is a plan view showing a total configuration of an optical disc apparatus according to a first embodiment of the present invention. The optical disc apparatus of the present embodiment in  FIG. 1  includes: a chassis  1  which functions as a base material to support other constituent elements in their entirety; a spindle motor  2  for rotating an optical disc; an optical pickup  3 ; a sliding base  4  including the optical pickup  3 ; a guide rack  5  with a moving mechanism for the sliding base  4 ; a main guide shaft  6   a  which guides movement of the optical pickup  3 ; a subsidiary guide shaft  6   b , being parallel to the main guide shaft  6   a , which works together with the main guide shaft  6   a  to guide the movement of the optical pickup  3 ; a feed motor  7  which generates a driving force to move the sliding base  4 ; guide supports  8   a ,  8   b  which support the main guide shaft  6   a  in an adjusted fashion at a desired position and in a desired posture/attitude; guide supports  8   c ,  8   d  which support the subsidiary guide shaft  6   b  in an adjusted fashion at a desired position and in a desired posture/attitude; and a feed screw  9  which transmits the driving force of the feed motor  7  to the guide rack  5 .  
         [0035]     The main guide shaft  6   a  has a cylindrical shape, is in engagement with the side of the sliding base  4  that faces the guide rack  5 , and guides movement of the optical pickup  3  in a radial direction of the optical disc. The subsidiary guide shaft  6   b  has a cylindrical shape and is in engagement with the section of the sliding base  4  that is opposite to the side at which the guide rack  5  is installed. The subsidiary guide shaft  6   b  cooperates with the main guide shaft  6   a  to guide the movement of the optical pickup  3  in the radial direction of the optical disc. The feed screw  9  is rotationally driven by the feed motor  7 , thus transmitting the driving force of the feed motor  7  to the guide rack  5 . That is to say, the main guide shaft  6   a  is located closer to the feed screw  9  than the location of the subsidiary guide shaft  6   b  with respect to the feed screw  9 .  
         [0036]     The chassis  1 , the optical pickup  3 , the main guide shaft  6   a , and the subsidiary guide shaft  6   b  are each constructed of a metallic material. The same kind of material can be used to construct the main guide shaft  6   a  and the subsidiary guide shaft  6   b . The guide supports  8   a ,  8   b ,  8   c ,  8   d  are each constructed of a resin material.  
         [0037]      FIG. 2  is a perspective view showing a configuration of the sliding base  4  in the optical disc apparatus according to the first embodiment of the present invention. In  FIG. 2 , the sliding base  4  has two first bearings  10   a ,  10   b  and one second bearing  11 . The first bearings  10   a ,  10   b  both have a holed shape to make the main guide shaft  6   a  extend through the holes, and thus, vertical and horizontal movements of the main guide shaft  6   a  can be restricted. As shown in  FIG. 2 , the second bearing  11  is of a rectangle with one side open, and its inner diameter is set to a value greater than the diameter of the subsidiary guide shaft, whereby the guide supports  8   c ,  8   d  can adjust the subsidiary guide shaft  6   b  to the desired position and to the desired posture/attitude.  
         [0038]      FIG. 3  is a cross-sectional view that shows section A-B of the main guide shaft and subsidiary guide shaft in the optical disc apparatus according to the first embodiment of the present invention. As can be seen from the sectional view of  FIG. 3  that shows section A-B of the main guide shaft and subsidiary guide shaft in the optical disc apparatus of  FIG. 1 , the present embodiment is constructed so that the diameter of the subsidiary guide shaft  6   b  is greater than that of the main guide shaft  6   a.    
         [0039]      FIGS. 4A and 4B  are explanatory diagrams that show different deformation modes of guide shaft resonance in the optical disc apparatus according to the first embodiment of the present invention.  FIG. 4A  is an in-phase deformation mode diagram of first-order guide shaft resonance, and  FIG. 4B  is an antiphase deformation mode diagram of second-order guide shaft resonance.  
         [0040]     If the main guide shaft  6   a  and the subsidiary guide shaft  6   b  are of the same cross-sectional shape, the first-order guide shaft resonance occurring during information recording on/reproduction from the optical disc, that is, during movement of the sliding base  4 , will be as shown in the in-phase deformation mode diagram of  FIG. 4A . Also, the second-order guide shaft resonance occurring during the movement of the sliding base  4  will be as shown in the antiphase deformation mode diagram of  FIG. 4B .  
         [0041]     The regions denoted by a broken line in  FIGS. 4A and 4B  indicate a section in which the sliding base  4  is present. During the movement of the sliding base  4 , the guide shafts including the sliding base  4  exhibit the greatest amplitude when suffering from in-phase deformation or antiphase deformation. The deformation with the greatest amplitude augments relative displacement between the optical pickup and the disc, thus causing loss of servo control. The present embodiment is intended to solve the problem of servo control being lost.  
         [0042]     More specific operation of the optical disc apparatus according to the present embodiment will be described hereunder.  
         [0043]     For the optical disc apparatus according to the present embodiment, the subsidiary guide shaft  6   b  does not resonate at a resonance frequency of the main guide shaft  6   a . That is to say, a functional feature of the optical disc apparatus according to the present embodiment exists in that the cross-sectional coefficient of the main guide shaft  6   a  and that of the subsidiary guide shaft  6   b  are made different to achieve the difference in natural frequency between both shafts. More specifically, for a cylindrical guide shaft, cross-sectional coefficient Z of the particular guide shaft is typically expressed by the following formula with a diameter of the guide shaft taken as “d”: 
 
 Z=π·d   4 /64  (Formula 1) 
 
         [0044]     If the cross-sectional coefficient of the main guide shaft  6   a  is taken as Z 1 (=1) and the cross-sectional coefficient of the subsidiary guide shaft  6   b  as Z 2 , the optical disc apparatus according to the present embodiment is constructed so that a ratio of Z 2 /Z 1  is at least 1.4.  
         [0045]     Amplitude of the optical pickup  3  in the above-constructed optical disc apparatus according to the present embodiment is described below. FIG. is a graph representing the relationship between the cross-sectional coefficient ratio of the main guide shaft and subsidiary guide shaft in the optical disc apparatus according to the present embodiment, and the amplitude of the optical pickup. The horizontal axis shown in  FIG. 5  denotes the ratio between the cross-sectional coefficient of the main guide shaft  6   a  and that of the subsidiary guide shaft  6   b , and the vertical axis shown denotes an amplitude ratio of the optical pickup.  
         [0046]     In  FIG. 5 , the amplitude ratio of the optical pickup  3  is set equal to 1, which applies if the main guide shaft  6   a  and the subsidiary guide shaft  6   b  are equal in cross-sectional coefficient to each other, that is, if the diameter of the main guide shaft  6   a  and that of the subsidiary guide shaft  6   b  are equal to each other as in the conventional art. As shown in  FIG. 5 , increases in the cross-sectional coefficient ratio Z 2 /Z 1  reduce the amplitude ratio of the optical pickup, and as a result, the amplitude ratio of the optical pickup asymptotically approaches 0.5. It is to be understood that a reduction rate of the optical pickup&#39;s amplitude ratio increases particularly at and after a section at which the cross-sectional coefficient ratio between the main guide shaft  6   a  and the subsidiary guide shaft  6   b  increases above 1.4. Hence, adopting an apparatus construction for a cross-sectional coefficient ratio of at least 1.4 between the main guide shaft  6   a  and the subsidiary guide shaft  6   b  makes it possible to reduce amplitudes of the main guide shaft  6   a  and the subsidiary guide shaft  6   b  during resonance thereof. Consequently, it is also possible to suppress vibration of the optical pickup and to prevent this pickup from losing its focus control, its tracking control, and the like. If the cross sections of the guide shafts are of cylindrical shape, a ratio of a diameter of the subsidiary guide shaft  6   b  to a diameter of the main guide shaft  6   a  is preferably equal to or greater than 1.088 based on Z=1.4 or Z&gt;1.4, and more preferably, equal to or greater than 1.189, based on Z=2.0 or Z&gt;2.0, which is more preferable as  FIG. 5  shown, according to Formula 1.  
         [0047]     In addition, since contact between the subsidiary guide shaft  6   b  and the second bearing  11  occurs at one section only, the foregoing construction of the optical disc apparatus according to the present embodiment permits the subsidiary guide shaft  6   b  to be enlarged in cross-sectional shape and thus the second bearing  11  to be reduced in surface pressure. Adopting such a construction for the actually enlarged cross-sectional shape of the subsidiary guide shaft  6   b , therefore, improves sliding characteristics of the sliding base  4  during axial movement thereof, even making it possible to provide a highly reliable optical disc apparatus.  
         [0048]     As set forth above, the optical disc apparatus of the present embodiment can cause the main guide shaft  6   a  and the subsidiary guide shaft  6   b  to take different values in natural frequency. The apparatus is therefore effective in suppressing the resonance of both shafts and the vibration of the optical pickup, and thus in preventing this pickup from losing its focus control, its tracking control, and the like.  
       Second Embodiment  
       [0049]     In terms of total configuration, an optical disc apparatus according to a second embodiment of the present invention is essentially the same as the optical disc apparatus of the first embodiment, shown in  FIG. 1 . The optical disc apparatus according to the second embodiment, however, is characterized in that a main guide shaft  12   a  has a diameter greater than that of the main guide shaft  6   a  in the first embodiment and in that unlike the subsidiary guide shaft  6   b  in the first embodiment, a subsidiary guide shaft  12   b  is of a hollow shaft shape.  
         [0050]      FIG. 6  is a sectional view that shows section A-B of the main guide shaft and subsidiary guide shaft in the optical disc apparatus according to the second embodiment of the present invention. As shown in  FIG. 6 , the optical disc apparatus of the present embodiment is constructed so that the subsidiary guide shaft  12   b  is hollow in cross-sectional shape and greater than the main guide shaft  12   a  in diameter. Constructing the apparatus in this fashion makes a difference between cross-sectional coefficients of the main guide shaft  12   a  and the subsidiary guide shaft  12   b , thus making it possible for both shafts to take different values as their natural frequencies. Accordingly, it becomes possible to suppress resonance of both the main guide shaft  12   a  and the subsidiary guide shaft  12   b  and vibration of an optical pickup, and hence as in the first embodiment, to prevent the optical pickup from losing its focus control, its tracking control, and the like. In addition, the hollow cross-sectional shaft shape of the subsidiary guide shaft  12   b  allows weight reduction thereof, which, in turn, contributes to weight reduction of the entire apparatus.  
         [0051]     The same kind of metallic material can be used to construct the main guide shaft  12   a  and the subsidiary guide shaft  12   b . Additionally, while the main guide shaft  12   a  and subsidiary guide shaft  12   b  in  FIG. 6  differ from each other in diameter, both shafts can also be constructed to have the same diameter. This is because, even if both shafts are of the same diameter, the cross-sectional coefficients of both take different values since the subsidiary guide shaft  12   b  is hollow in shape.  
       Third Embodiment  
       [0052]      FIG. 7  is a configuration diagram showing a total configuration of an optical disc apparatus according to a third embodiment of the present invention. As shown in  FIG. 7 , the optical disc apparatus according to the third embodiment of the present embodiment includes a main guide shaft  13  and a subsidiary guide shaft  14  in lieu of the main guide shaft  6   a  and subsidiary guide shaft  6   b , respectively, used in the optical disc apparatus according to the first embodiment of the present invention. The optical disc apparatus according to the third embodiment also has connectors  15  between a chassis  1  and the subsidiary guide shaft  14 . Description is omitted of other sections functionally and structurally overlapping those of  FIG. 1 . The same kind of metallic material can be used to construct the main guide shaft  13  and the subsidiary guide shaft  14 .  
         [0053]      FIG. 8  is a sectional view that shows section C-D of the main guide shaft and subsidiary guide shaft in the optical disc apparatus according to the third embodiment of the present invention. The main guide shaft  13  in  FIG. 8  is of a cylindrical shape. The main guide shaft  13  and the subsidiary guide shaft  14  are constructed using a metallic material. The main guide shaft  13  is engaged with the side of a sliding base  4  that faces a guide rack  5 , and thus the main guide shaft  13  guides movement of an optical pickup  3  in a radial direction of an optical disc. The subsidiary guide shaft  14  is engaged with the section of the sliding base  4  that is opposite to the side at which the guide rack  5  is installed. The subsidiary guide shaft  14  cooperates with the main guide shaft  13  to guide the movement of the optical pickup  3  in the radial direction of the optical disc.  
         [0054]      FIG. 9  is an assembly diagram of the subsidiary guide shaft in the optical disc apparatus according to the third embodiment of the present invention. As shown  FIG. 9 , the subsidiary guide shaft  14  includes a cylindrically shaped structural member  14   a  and a plate-shaped member  14   b , both of which are the same as those of the main guide shaft  13  in terms of diameter. An axially horizontal groove  14   c  and a pair of coupling holes  14   d  for bringing the plate-shaped member  14   b  into engagement with the groove  14   c  are formed on the opposite-side face of the cylindrically shaped structural member  14   a  that is opposed to the main guide shaft  13 . The plate-shaped member  14   b  has pins  14   e  arranged thereon. The connection holes  14   d  and the associated pins  14   e  are engaged to form the subsidiary guide shaft  14 . The cylindrically shaped structural member  14   a  and the plate-shaped member  14   b  are constructed of a metallic material. The connectors  15  are each formed of a resin material.  
         [0055]     Functionality of the optical disc apparatus according to the present embodiment will be described hereunder.  
         [0056]     A cross-sectional coefficient of the subsidiary guide shaft  14  is increased above that of the main guide shaft  13 . That is to say, if the main guide shaft has a diameter of “d” and the plate-shaped member  14   b  of the subsidiary guide shaft  14  has a plate thickness of “h”, and a length of L, at a protruding section, cross-sectional coefficient Z 3  of the subsidiary guide shaft  14  is denoted by formula (2). 
 
 Z 3= L·h/ 12+π· d   4 /64  (Formula 2) 
 
         [0057]     In other words, a cross-sectional coefficient of the subsidiary guide shaft  14  can be set a value greater than that of the main guide shaft  13 .  
         [0058]     In addition, the connectors  15  connect with the subsidiary guide shaft  14  at least one section, and as mentioned above, the connectors are made of resin. When the subsidiary guide shaft  14  vibrates, therefore, the connectors  15  absorb and attenuate the vibration. Thus, the apparatus is effective in suppressing vibration of the optical pickup as well, and thus in preventing this pickup from losing its focus control, its tracking control, and the like.  
         [0059]     In the optical disc apparatus of the present embodiment, the cylinder-shaped structural member  14   a  and the plate-shaped member  14   b  configure the subsidiary guide shaft  14 . However, the present invention is not limited to this configuration. For example, even if the subsidiary guide shaft  14  takes a configuration in which it is integrally formed of a metallic material, it is possible to obtain essentially the same effects as those described above.  
         [0060]     While specific embodiments of the optical disc apparatus of the present invention have been described above, the invention is not limited to these embodiments. Any person skilled in the art can introduce various modifications/improvements in the configuration and functionality of the present invention according to each of the above embodiments or any other embodiments, without departing from the scope of the invention.  
         [0061]     The present invention can be applied to realization of optical disc apparatuses, and more particularly to realizing compact disc, digital versatile disc, and Blu-ray disc types of optical disc apparatuses.  
         [0062]     While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.