Abstract:
In an optical pickup comprising an object lens a lens holder for holding the object lens, a damper base for supporting the lens holder through a plurality of suspension wires to allow the lens holder to shift up and down and right and left, and an actuator base including a supporting block for fixedly supporting the damper base by using a screw, the damper base has an oval hole which allows the screw to pass therethrough.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an optical pickup for recording/reproducing data in/from an optical recording medium such as an optical disc, a damper base for use in the optical pickup, and an adjustment method for adjusting the damper base. 
     In the manner known in the art, an electric equipment such as a personal computer is connected to various peripheral units one of which comprises a memory device or a recording medium. In addition, there is various types of memory devices (recording media). In other words, the memory devices (recording media) are classified into removable media and non-removable media. On of the removable media comprises a compact disc-recordable (CD-R). The compact disc-recordable is an audible recording medium which is compatible with a compact disc read only memory (CD-ROM) or a compact disc-digital audio (CD-DA). Although to write information (data) in the CD-R requires an exclusive apparatus or a CD-R drive and a writing application, to read the information (data) from the CD-R may be carried out by using a CD-ROM drive. Although it is impossible to cancel the date once written, it is possible to frequently add data. 
     Various other removable media are already known. A compact disc-rewritable (CD-RW) is a compact disc which is capable of erasing data therefrom and of rewriting data therein many times. 
     Now, in order to write information (data) in the CD-R or the CD-RW and to read the information (data) from the CD-R or the CD-RW demands a recording/reproducing optical pickup requires for irradiating a laser beam on the CD-R or the CD-RW. 
     In general, the optical pickup of the type described comprises a laser optical source for outputting the laser beam and an optical system for guiding the outputted laser beam to a recording medium such as an optical disc. As described above, it is possible for the CD-R and the CD-RW to carry out not only reading of information but also writing of information. In the optical pickup for the CD-R and the CD-RW, it is necessary to change output or power of the laser beam outputted by the laser optical source either on reading of information or on writing of information. This is because writing of information is carried out by forming a pit in a recording layer of the optical disc by irradiating of the laser beam. Accordingly, the output of the laser beam on writing of information is larger than that on reading of information and is, for example, ten to twenty times as large as that on reading of information. 
     The optical pickup comprises an object lens, a lens holder for holding the object lens, a damper base for shiftably supporting up and down and right and left the lens holder through a plurality of suspension wires, and actuator base including a supporting block for fixedly supporting the damper base by using a screw. 
     In the manner which will later be described in conjunction with FIG. 5, a conventional damper base has a circular hole which merely allows the screw to pass therethrough. With this structure, it is possible to correct an angular displacement of the object lens in a radial direction in regard to an optical axis by fastening the damper base to the supporting block with the damper base suitably rotated about the screw. 
     The above-mentioned damper base merely can adjust an angle of the object lens in the radial direction in regard to the optical axis. However, it is actually necessary not only to correct the angular displacement of the object lens in the radial direction that occurs on assembling and so on but also to correct a position displacement of the object lens in the radial direction. This assemble requires a precision of about tens of microns. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of this invention to provide an optical pickup, a damper base for use therein, and an adjusting method therefore, which are capable of easily correcting not only an angular displacement of an object lens in a radial direction that occurs on assembling and so on but also a position displacement of the object lens. 
     Other objects of this invention will become clear as the description proceeds. 
     On describing the gist of this invention, it is possible to be understood that an optical pickup comprises an object lens, a lens holder for holding the object lens, a damper base for supporting the lens holder through a plurality of suspension wires to allow the lens holder to shift up and down and right and left, and an actuator base including a supporting block for fixedly supporting the damper base by using a screw. According to an aspect of this invention, in the above-mentioned optical pickup, the damper base has an oval hole which allows the screw to pass therethrough. 
     On describing the gist of this invention, it is possible to be understood that a damper base is for use in an optical pickup comprising an object lens, a lens holder for holding the object lens, and an actuator base including a supporting block for fixedly supporting the damper base by using a screw. The damper base supports the lens holder through a plurality of suspension wires to allow the lens holder to shift up and down and right and left. According to an aspect of this invention, the afore-mentioned damper base has an oval hole which allows the screw to pass therethrough. 
     On describing the gist of this invention, it is possible to be understood that a method is for adjusting the afore-mentioned damper base. According to an aspect of this invention, the above-mentioned method comprising the steps of temporarily fixing the damper base on the supporting block by using the screw, of correcting a position displacement of the object lens in a radial direction in regard to an optical axis of a laser beam so as to make a center of the object lens coincide with the optical axis by sliding the damper base in a longitudinal direction of the oval hole, of correcting an angular displacement of the object lens in the radial direction in regard to the optical axis so as to make a central line of the object lens coincide with the optical axis by rotating the damper base the said screw, and of truly fixing the damper base on the supporting block by fastening the screw. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a plan view showing a conventional optical pickup; 
     FIG. 2 is a cross-sectional view taken on line II—II on FIG. 1; 
     FIG. 3 is a schematic diagram of an optical system of the optical pickup illustrated in FIG. 1; 
     FIG. 4 is a rear elevation of a supporting block of an actuator base for use in the optical pickup illustrated in FIG. 1; 
     FIG. 5 is a rear elevation of a conventional damper base for use in the optical pickup illustrated in FIG. 1; 
     FIGS. 6A and 6B collectively show an assembled state where the conventional damper base is fastened on the supporting block of the actuator base in the optical pickup illustrated in FIG. 1; 
     FIG. 7 is an enlarged sectional view of a portion of the assembled state depicted at FIG. 6A, which portion is labelled “FIG.  7 ” in FIG. 6A; 
     FIG. 8 is a rear elevation of a damper base according to a preferred embodiment of this invention; and 
     FIGS. 9A and 9B collectively show views for use in describing a procedure for adjusting the damper base illustrated in FIG.  8 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, a conventional optical pickup  10  will be described at first in order to facilitate an understanding of the present invention. The illustrated optical pickup  10  is for use in an optical disc recording/reproducing apparatus such as a CD-R drive. 
     The optical pickup  10  comprises an optical base  12 , a lens holder  14 , a damper base  16 , and an actuator base  18 . The lens holder  14  holds an object lens  20  and is provided with a tracking coil (not shown) and a focusing coil  22 . The actuator base  18  receives the lens holder  14  and the damper base  16 . 
     The optical pickup  10  comprises a laser diode  24  serving as a laser light source for producing a laser beam. In addition, the optical pickup  10  further comprises an optical system which includes a diffraction grating (which will later become clear), a polarization beam splitter  26 , a collimator lens  28 , a quarter wavelength plate (which will later become clear), a rising mirror  30 , the object lens  20 , a sensor lens (which will later become clear), and a photodiode (which will later become clear). Produced by the laser diode  24 , the laser beam passes through the diffraction grating, the polarization beam splitter  26 , the collimator lens  28 , the quarter wavelength plate, the rising mirror  30 , and the object lens  20  and then is irradiated on an optical disc (CD-R) (which will later become clear). Reflected by the optical disc, a reflected laser beam passes through the object lens  20 , the rising mirror  30 , the quarter wavelength plate, the collimator lens  28 , the polarization beam splitter  26 , and the sensor lens and then is received in the photodiode. That is, the photodiode receives the reflected laser beam from the optical disc. In addition, arranged on an optical path of the laser beam, optical components and relationship there among will later be described with reference to FIG.  3 . 
     The laser diode  24  and optical parts such as the polarization beam splitter  26  are held in or mounted on the optical base  12 . In addition, the optical base  12  is slidably held in a chassis or frame (not shown) of the optical disc drive. The optical base  12  has a side surface on which a flexible circuit substrate  32  is fixed or mounted. The flexible circuit substrate  32  is connected to a flexible cable  34  through which the flexible circuit substrate  32  is electrically connected to other circuit elements (not shown) of the optical disc drive. 
     Between the lens holder  14  and the damper base  16  is connected by a plurality of suspension wires  36 . A combination of the lens holder  14 , the damper base  16 , and the suspension wires  36  is received in the actuator base  18 . The actuator base  18  has parts acting as yokes  38  on which permanent magnets  40  are fitted. 
     The actuator base  18  has a substantially frame structure made of metallic material. The substantially frame structure has an end serving as a receiving portion (not shown) for the damper base  16 . The receiving portion comprises a supporting block  42  for fixing the damper base  16 . The supporting block  42  is integrally formed with the actuator base  18 . In addition, the substantially frame structure has both side walls which are provided with substantially semicircular projections  44 . The substantially semicircular projections  44  are supported by supporting portions  46  provided in the optical base  12 . 
     The damper base  16  is fitted with damper base covers  48  made of transparent resin material. The damper base covers  48  have rear portions serving as fixing portions  50  for fixing ends of the suspension wires  36 . In a space between the damper base  16  and the damper base covers  48  is injected damping material (not shown) for suppressing vibrations of the suspension wires  36 . 
     The damper base  16  has a rear wall which is provided with a flexible printed board  52  for connecting with end portions of the suspension wires  16  by solder. The damper base  16  is fixed between the both side walls of the actuator base  18  and the supporting block  42  with the damper base  16  inserted in a space therebetween. 
     The damper base  16  is attached on the supporting block  42  by a screw or bolt  54  and a nut  56  with the supporting block  42  put between the damper base  16  and the screw  54 . The damper base  16  is rotatable about the screw  54  as a center. This is for skew adjustment. 
     Before the damper base  16  is fixed on the actuator base  18 , the suspension wires  36  are attached to the damper base  16 . That is, the lens holder  14  and the damper base  16  are received in and fixed on the actuator base  18  in a state of an assembly where the lens holder  14  and the damper base  16  are connected by the suspension wires  36 . 
     FIG. 3 illustrates the optical system of the optical pickup  10 . The illustrated optical system comprises the laser diode  24 , the diffraction grating depicted at  58 , the polarization beam splitter  26 , the collimator lens  28 , the quarter wavelength plate depicted at  60 , the rising mirror  30 , the object lens  20 , the optical disc depicted at  62 , the sensor lens depicted at  64 , and the photodiode depicted at  66 . 
     Produced by the laser diode  24  to the left horizontally, one laser beam is separated by the diffraction grating  58  into three laser beams. The three laser beams passes through the polarization beam splitter  26  and thereafter converted by the collimator lens  28  into collimated laser beams. The collimated laser beams pass through the quarter wavelength plate  60  and then are orthogonally bent by the rising mirror  30  to go upwardly in an optical axis OA. Thereafter, the collimated laser beams are irradiated on the optical disc  62  through the object lens  20 . 
     Reflected from the optical disc  62 , reflected laser beams go downwardly, pass through the object lens  20 , and are orthogonally bent by the rising mirror  30  to go to the right horizontally. The reflected laser beams pass the quarter wavelength plate  60  and are then converted by the collimator lens  28  into convergence laser beams. The convergence laser beams are orthgonally bent by the polarization beam splitter  26  to go in the forward direction horizontally. Thereafter, the convergence laser beams pass through the sensor lens  64  and are received in the photodiode  66 . 
     FIG. 4 is a rear elevation of the supporting block  42  and FIG. 5 is a rear elevation of the damper base  16 . As shown in FIG. 4, the supporting block  42  has a threaded hole  42   a . As shown in FIG. 5, the damper base  16  has a circular hole  16   a  which merely allows the above-mentioned screw  54  (FIG. 1) to pass therethrough. 
     FIGS. 6A and 6B collectively show an assembled state where the damper base  16  is fastened on the supporting block  42  of the actuator base  18 . FIG. 6A is a bottom view of the assembled state while FIG. 6B is a rear elevation of the assembled state. FIG. 7 is an enlarged sectional view of a portion of the assembled state depicted at FIG. 6A, which portion is labelled “FIG.  7 ” in FIG.  6 A. 
     With this structure, it is possible to correct an angular displacement of the object lens  20  in a radial direction Ra in regard to the optical axis OA by fastening the damper base  16  to the supporting block  42  with the damper base suitably rotated about the screw  54  in a direction depicted at an arrow R as illustrated in FIG.  6 B. 
     The above-mentioned damper base  16  merely can adjust an angle of the object lens  20  in the radial direction Ra in regard to the optical axis OA. However, it is actually necessary not only to correct the angular displacement of the object lens  20  in the radial direction Ra that occurs on assembling and so on but also to correct a position displacement of the object lens  20  in the radial direction Ra, as mentioned in the preamble of the instant specification. This assemble requires a precision of about tens of microns. 
     Referring to FIG. 8, the description will proceed to a damper base  16 A according to a preferred embodiment of this invention. As shown In FIG. 8, the damper base  16 A has an oval hole  16 A a  in lieu of the circular hole  16   a  as illustrated In FIG.  5 . With this structure, it is possible for the damper base  16 A to carry out not only an angular adjustment of the object lens  20  (FIG. 1) in the radial direction Ra but also a position adjustment of the object lens  20  In the radial direction Ra In the manner which will presently be described. 
     Referring now FIGS. 9A and 9B, the description will proceed to a procedure for adjusting the damper base  16 A. 
     At first, the damper base  16 A is temporarily fixed on the supporting block  42  by using the screw  54 . Subsequently, as shown in FIG. 9A, a position displacement of the object lens  20  (FIG. 1) in the radial direction Ra in regard to an optical axis OA of a laser beam is corrected by sliding the damper base  16 A in a longitudinal direction S of the oval hole  16 A a  to make a center of the object lens  20  coincide with the optical axis OA. Thereafter, as shown in FIG. 9B, an angular displacement of the object lens  20  in the radial direction Ra in regard to the optical axis OA is corrected by rotating the damper base  16 A about the screw  54  as depicted at an arrow R to make a central line of the object lens  20  coincide with the optical axis AS. Finally, the damper base is truly fixed on the supporting block  42  by fastening the screw  54 . 
     As a result, it is possible in the damper base  16 A to easily carry out not only the angular adjustment of the object lens  20  in the radial direction Ra but also the position adjustment of the object lens  20  in the radial direction Ra although it is possible in the conventional damper base  16  to carry out only the angular adjustment of the object lens  20  in the radial direction Ra. 
     While this invention has thus far been described in conjunction with preferred embodiments thereof, it will now be readily possible for those skilled in the art to put this invention into various other manners.