Abstract:
There is provided an optical pick-up apparatus with a plurality of lenses, in which an actuator is carried to place a specific lens of a lens holder on an optical axis. In the optical pick-up apparatus, the actuator has the plurality of lenses to focus lasers with different wavelengths on a track of a disk according to the type of the disk, and a linear driving unit carries the actuator to place one of the lenses on a laser path.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an optical pick-up apparatus, and more particularly, to an optical pick-up apparatus with a plurality of lenses, in which an actuator with a plurality of lenses is capable of linear reciprocating motion.  
         [0003]     2. Description of the Related Art  
         [0004]     Usage of high-quality and big-size moving pictures is becoming very common, and accordingly the capacity of optical disk has been increasing. For example, an optical system utilizing a short wave blue laser (e.g., 405 nm) has been developed.  
         [0005]     Further, to use a blue laser disk (BD) together with a compact disk/digital video [versatile] disk (CD/DVD), an optical pick-up system with a blue laser lens together with a red laser lens has been developed.  
         [0006]      FIG. 1  is a perspective view of an axle-type optical pick-up actuator with a dual lenses according to the related art, and  FIG. 2  is an exploded perspective view of an axle-type optical pick-up actuator depicted in  FIG. 1 .  
         [0007]     Referring to  FIGS. 2 and 3 , an axle-type optical pick-up actuator includes a circular lens holder  104 , a focusing coil  106 , tracking coils  108 , a yoke  112 , metal pieces  114 , a balancing weight  116 , and a shaft  18 .  
         [0008]     The lens holder  104  holds a dual lens  102  with different lens. The coils  106  and  108  together with magnets  110  generate a driving force to align the dual lens  102  of the lens holder  104  with a signal track of a disk. The magnets  110  attach to the inner surface of the yoke  112 , and the yoke  112  defines a beam hole  120  in which a laser passes. The metal pieces  114  are disposed inside of the tracking coils  108  to dampen rotation of the lens holder  104 . The balancing weight  116  is disposed on the lens holder  104  to align the mass center and the geometric center of the lens holder  104 . The shaft  118  has one end-fixed to the yoke  112  and the other end inserted into the lens holder  104 .  
         [0009]     The dual lens  102  includes different object lenses. For example, the dual lens  102  includes object lenses  101  and  103 , and the object lens  101  may be a red laser lens for CD/DVDs, and the object lens  103  may be a blue laser lens for blue laser disks.  
         [0010]     Referring again to  FIGS. 1 and 2 , the lens holder  104  has a cylindrical or disk shape. The lens holder  104  includes object lenses  101  and  103  (dual lens  102 ) arranged at an angle of 90 degrees to each other. The object lens  101  may be a red laser lens for CD/DVDs, and the object lens  103  may be a blue laser lens for blue laser disks. Also, the lens holder  104  includes the balancing weight  116  opposite to the dual lens  102  for mass balance.  
         [0011]     The focusing coil  106  is wounded around the lens holder  104 , and the tracking coils  108  are arranged on the outer surface of the focusing coil  106 . Also, the metal pieces  114  are disposed inside of the tracking coils  108 , respectively.  
         [0012]     The yoke  112  is coupled with the lens holder  104 . The yoke includes vertically extended parts. The magnets  110 , corresponding to the tracking coils  108 , are attached to inner surfaces of the extended parts. Also, the yoke  112  defines the beam hole  120  to pass a laser beam.  
         [0013]     The shaft  118  is formed at a bottom center of the yoke  112  and of which free end is inserted into the lens holder  104  for guiding the motion of the lens holder  104 .  
         [0014]     The operation of the axle-type optical pick-up actuator will now be described.  
         [0015]     When the focusing coil  106  is supplied with current, an electromagnetic force is produced between the focusing coil  106  and the magnets  110  to move the lens holder  104  up and down from a disk. The up and down motion of the lens holder  104  is guided by the shaft  118 .  
         [0016]     When the tracking coils  108  are supplied with current, an electromagnetic force produced between the tracking coils  108  and the magnets  110  rotates the lens holder  104  about the shaft  118 .  
         [0017]     Since the optical axis of laser beam passes the beam hole  120 , when one of the object lenses  101  and  103  is aligned with the beam hole  120 , a laser beam is scanned to a disk through the beam hole  120  and the aligned object lens.  
         [0018]     The alignment of the object lens  101  and the object lens  103  is carried out depending on the type of a disk. For example, the object lens  101  is aligned with the beam hole  120  for passing a red laser beam therethrough when a CD/DVD is loaded, and the object lens  103  is aligned with beam hole  120  for passing a blue laser beam when a blue laser disk is loaded.  
         [0019]     The lens holder  104  is rotated 90° clockwise or counterclockwise about the shaft  118  as shown in  FIG. 3 . For the rotation of the lens holder  104 , the tracking coils  108  are supplied with current to generate an electromagnetic force. Since the electromagnetic force has to be bigger than the attractive force between the magnets  110  and the metal pieces  114  to rotate the lens holder  104 , the amount of the current supplying to the tracking coils  108  is determined depending on the attractive force.  
         [0020]     In this way, the axle-type optical pick-up actuator can align different types of lens on the optical axis to access different types of disks, such as CD/DVDs and blue laser disks.  
         [0021]     However, the 90° rotation of the lens holder  104  causes the lens holder  104  to have bigger size. Further, the alignment between the optical axis and the object lens  101  or  103  can be deviated because of the rotation of the lens holder  104 .  
         [0022]     Furthermore, the balancing weight  116  on the lens holder  104  decreases the sensitivity of the optical pick-up actuator. Especially, this decrease in sensitivity makes it hard to apply the optical pick-up actuator to high-speed optical storage devices.  
       SUMMARY OF THE INVENTION  
       [0023]     Accordingly, the present invention is directed to an optical pick-up apparatus with a plurality of lenses that substantially obviates one or more problems due to limitations and disadvantages of the related art.  
         [0024]     An object of the present invention is to provide an optical pick-up apparatus with a plurality of lenses, in which an actuator can be carried.  
         [0025]     Another object of the present invention is to provide an optical pick-up apparatus with a plurality of lenses, in which the distances among the lenses are the same as the displacements of an actuator.  
         [0026]     A further another object of the present invention is to provide an optical pick-up apparatus with a plurality of lenses, in which the lenses are arranged at an angle of 180 degrees from each other to place desired one of the lens on an optical axis by moving an actuator.  
         [0027]     A further another object of the present invention is to provide an optical pick-up apparatus with a plurality of lenses, in which the lenses are arranged in a line to place desired one of the lenses on an optical axis by moving an actuator.  
         [0028]     A still further another object of the present invention to provide an optical pick-up apparatus with a plurality of lenses, in which a linear driving unit is coupled with an actuator to reciprocate the actuator along a linear path without deviation between the lenses and an optical axis.  
         [0029]     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
         [0030]     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an optical pick-up apparatus, including: an actuator having a plurality of lenses to focus lasers with different wavelengths on a track of a disk; and a linear driving unit carrying all the actuator to place one of the lenses on a laser path.  
         [0031]     In another aspect of the present invention, there is provided an optical pick-up apparatus, including: a lens holder having a plurality of lenses to focus lasers with different wavelengths on a track of a disk; a frame located a predetermined distance from the lens holder; a plurality of wire suspensions connected between the lens holder and the frame; and a linear driving unit carrying the lens holder and the frame in a linear direction to place one of the lenses on an optical axis in accordance with the type of the disk.  
         [0032]     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0033]     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:  
         [0034]      FIG. 1  is a perspective view of an axle-type optical pick-up actuator with a dual lens according to the related art;  
         [0035]      FIG. 2  is an exploded perspective view of an axle-type optical pick-up actuator depicted in  FIG. 1 ;  
         [0036]      FIG. 3  is a perspective view showing replacement of an object lens of an axle-type optical pick-up actuator depicted in  FIG. 1 ;  
         [0037]      FIG. 4  is a plan view of an optical pick-up apparatus with a plurality of lenses according to the present invention;  
         [0038]      FIG. 5  is a plan view of an optical pick-up apparatus with a plurality of lenses, showing an operation of a first object lens according to the present invention;  
         [0039]      FIG. 6  is a side view of an optical pick-up apparatus depicted in  FIG. 5 ;  
         [0040]      FIG. 7  is a plan view of an optical pick-up apparatus with a plurality of lenses, showing an operation of a second object lens according to the present invention;  
         [0041]      FIG. 8  is a side view of an optical pick-up apparatus depicted in  FIG. 7 ;  
         [0042]      FIG. 9  is a plan view of an optical pick-up apparatus with a plurality of lenses, in which a linear driving unit is shown according to a first embodiment of the present invention;  
         [0043]      FIG. 10  is a plan view of an optical pick-up apparatus with a plurality of lenses, in which a linear driving unit is shown according to a second embodiment of the present invention;  
         [0044]      FIG. 11  is a plan view of an optical pick-up apparatus with a plurality of lenses, in which a linear driving unit is shown according to a third embodiment of the present invention; and  
         [0045]      FIG. 12  is a plan view of an optical pick-up apparatus with a plurality of lenses, in which a linear driving unit is shown according to a forth embodiment of the present invention; 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0046]     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0047]      FIG. 4  is a plan view of an optical pick-up apparatus with a plurality of lenses according to the present invention.  
         [0048]     Referring to  FIG. 4 , an optical pick-up apparatus includes: an actuator  200 ; a lens holder  204  provided with lenses  203 ; coils  205  and  206  for moving the lens holder  204 ; magnets  207  facing with the coils  205  and  206 ; a yoke  209  on which the magnets  207  are fixed; a yoke plate  209  from which the yoke  208  is vertically extended; a frame  230  located a predetermined distance from the lens holder  204 ; wire suspensions  220  connected between the lens holder  204  and the frame  230  to support the lens holder  204 ; and a linear driving unit  240  for carrying all the actuator  200  in the directions of arrows Lm and Rm to align any one of the lenses  203  with an optical axis.  
         [0049]     The lenses  203  include a first object lens  201  and a second object lens  202  that are arranged in a line (at an angle of 180°).  
         [0050]     The actuator  200  with lenses  203  is moved in right and left directions by the linear driving unit  240  (linear reciprocating motion). As with other directional terms, the terms “right” and “left” are used in a relative sense and are not limiting.  
         [0051]     For this linear reciprocating motion, the actuator  200  includes the lens holder, a magnetic circuit, the wire suspension  220 , and the frame  200 .  
         [0052]     The lens holder  204  holds the first and second object lenses  201  and  202 . The first object lens  201  may be a blue laser lens for an blue laser disk (BD), and the second object lens  202  may be a red laser lens for an compact disk/digital video [versatile] disk (CD/DVD). The locations of the first and second object lenses  201  and  202  can be interchanged with each other.  
         [0053]     The first and second object lenses  201  and  202  are located a predetermined distance from each other and their center are aligned in a line.  
         [0054]     The coils  205  and  206  are disposed on each side of the lens holder  204 . The coils  205  are focusing coils, and the coils  206  are tracking coils. Each of the focusing coils  205  is wounded about a vertical axis, and each of the tracking coils  206  is wounded about a horizontal axis. A tilt coil, (not shown) can be disposed at a predetermined portion of the lens holder  204 .  
         [0055]     The magnets  207  are fixed to inner surfaces of the yoke  208  to face with the coils  205  and  206 . Each of the magnets  207  may include a plurality of unidirectional (unipolar) magnets or a plurality of bipolar magnets or may be a multipolar magnet. The term “unidirectional” is used to denote a magnet with the positive pole on one side and the negative pole on the opposite side, the term “bipolar” is used to denote a magnet with the positive pole and the negative pole on the same side (two poles on the same side), and the “multipolar” is used to denote a magnet with positive poles and negative poles on the same side. For example, according to the polarities of the magnets  207 , the focusing coils  205  move the lens holder  204  up and down and the tracking coils  206  move the lens holder  204  right and left.  
         [0056]     The yoke  208  and the yoke plate  209  are formed in one piece, and the yoke extends vertically from the yoke plate  209  and. The magnets  207  are attached to inner surfaces of the yoke  208 .  
         [0057]     The wire suspensions  220  are connected between the lens holder  204  and the frame  230  to support the movement of the lens holder  204  and to supply power to the coils  205  and  206 . The frame  230  is provided with a circuit board electrically connected with the wire suspension  220 . The number of wire suspension  220  is not critical. For example, two pairs or three pairs of wire suspensions may be connected between the frame  220  and the lens holder  204  according to two-axis or three-axis movement of the lens holder  200 . The term “two-axis” is used to denote the focusing and tracking movements of the lens holder  204 , and the term “three-axis” is used to denote the focusing, tracking, and tilting movement of the lens holder  204 .  
         [0058]     The linear driving unit  240  is attached to each side of the frame  230  to move the frame  230  in right and left directions. The linear driving unit  240  includes a linear motor to move the frame toward an optical disk. The distance between rightmost and leftmost positions of the frame  230  is the same as the distance between the first object lens  201  and the second object lens  202 .  
         [0059]     In the optical pick-up apparatus of the present invention, focusing coils  205 , the tracking coils  206 , the magnets  207 , and the yoke  208  are configured to form a magnetic circuit for the focusing and tracking movement of the lens holder  204 .  
         [0060]     The actuator  200  moves right or left to align the first object lens  201  or the second object lens  202  with the optical axis of a laser beam in accordance with the type of loaded optical disk. For example, the first object lens  201  is placed on the optical axis, and the second object lens  202  is placed on the optical axis when a CD or DVD is loaded.  
         [0061]     Therefore, the linear driving unit  240  may further include a controlling element to judge which object lens is to be placed on the optical axis and to control the movement of lens holder  204 .  
         [0062]      FIG. 5  is a plan view of an optical pick-up apparatus with a plurality of lenses, showing an operation of a first object lens according to the present invention.  
         [0063]     Referring to  FIG. 5 , the frame  230  is moved in the direction of arrow Rm by the linear driving unit  240 . That is, the actuator  200  is moved right. Herein, the lens holder  204  is also moved a predetermined distance to the right to place the first object lens  201  on the optical axis. Through the first object lens  201 , a laser beam is scanned to a loaded disk (not shown) to access or write data. Herein, the laser beam may be a blue laser beam if the loaded optical disk is a blue laser disk.  
         [0064]      FIG. 6  is a side view of an optical pick-up apparatus depicted in  FIG. 5 .  
         [0065]     Referring to  FIG. 6 , the linear driving unit  240  moves the frame  230  in the direction of arrow Rm to carry the lens holder  204  connected to the frame  230  by the wire suspensions  220 . Therefore, the first object lens  201  aligns with the optical axis (Z) and a first laser beam B 1  passes through the first object lens  201 . For example, a blue laser beam B 1  generated by a blue laser diode (not shown) is reflected by a mirror  261  and then scanned to the blue laser disk through the first object lens  201  to access or write data.  
         [0066]     When the loaded disk is ejected and a different type of optical disk is loaded, the linear driving unit  240  moves the actuator  200  right along a straight path to place the first object lens  201  on the optical axis (Z). This linear transportation enables exact alignment between the object lens and the optical axis (Z) without deviation when changing the object lens.  
         [0067]      FIG. 7  is a plan view of an optical pick-up apparatus with a plurality of lenses, showing an operation of a second object lens according to the present invention.  
         [0068]     Referring to  FIG. 7 , the frame  230  is moved in the direction of arrow Lm by the linear driving unit  240 . That is, the actuator  200  is moved left. Herein, the lens holder  204  is also moved a predetermined distance to the left to place the second object lens  202  on the optical axis. Through the second object lens  202 , a laser beam is scanned to the loaded disk to access or write data. Herein, the laser beam may be a red laser beam if the loaded optical disk is a CD or DVD.  
         [0069]      FIG. 8  is a side view of an optical pick-up apparatus depicted in  FIG. 7 .  
         [0070]     Referring to  FIG. 8 , the linear driving unit  240  moves the frame  230  in the direction of arrow Lm to carry the lens holder  204  connected to the frame  230  by the wire suspensions  220 . Therefore, the second object lens  202  aligns with the optical axis (Z) and a second laser beam B 1  passes through the second object lens  202 . For example, a blue laser beam B 1  generated by a blue laser diode (not shown) is reflected by the mirror  261  and then scanned to the loaded CD or DVD through the second object lens  202  to access or write data.  
         [0071]     When the loaded disk is ejected and a different type of optical disk is loaded, the linear driving unit  240  moves the actuator  200  left along a straight path to place the second object lens  202  on the optical axis (Z). This linear transportation enables exact alignment between the object lens and the optical axis (Z) without deviation when changing the object lens.  
         [0072]     To precisely align the object lenses  201  and  202  with the optical axis (Z), the linear driving unit  240  includes a first portion and a second portion that are synchronized and respectively disposed at both sides of the frame  230 . That is, the linear driving unit  240  is tightly abutted on the frame  230  of the actuator  200  and in this condition the linear motor (e.g., piezoelectric motor) of the linear driving unit  240  moves the frame  230 . After the frame  230  of actuator  200  is moved to a position where the first object lens  201  or the second object lens  202  is aligned with the optical axis (Z), the actuator  200  is securely fixed at the position owing to the tight abutment between the linear driving unit  240  and the frame  230  (i.e., degree of freedom is zero), thereby preventing deviation error.  
         [0073]      FIG. 9  is a plan view of an optical pick-up apparatus with a plurality of lenses, in which a linear driving unit is shown according to a first embodiment of the present invention.  
         [0074]     Referring to  FIG. 9 , a linear driving unit  240  utilizes a surface wave type piezoelectric motor. The linear driving unit  240  includes a generator  241 , a piezoelectric vibrator  242 , an amplifying plate  243 , and a guide rod  245 . The linear driving unit  240  enables a linear reciprocating motion of an actuator  200  and does not allow any other motion of the actuator  200 . For this purpose, the piezoelectric vibrator  242  and the amplifying plate  243  are pressed to keep frictional contact between the linear driving unit  240  and a frame  230  of the actuator  200 , and a linear motor such as a piezoelectric ultrasonic motor is used to move the actuator under the frictional contact condition.  
         [0075]     In operation of the piezoelectric ultrasonic motor, the piezoelectric vibrator  242  vibrates when the generator  241  is powered on. The vibration of the piezoelectric vibrator  242  is transmitted to the frame  230  through the guide rod  230  to move the frame  230  in a linear direction. In detail, the vibration of the piezoelectric vibrator  242  creates an elliptical trajectory on the surface of the piezoelectric vibrator  242 , and the amplifying plate  243  of which length is larger than the wave length of the vibration of the piezoelectric vibrator  242  is disposed on the piezoelectric vibrator  242  such that the amplifying plate  243  comes into contact with the piezoelectric vibrator  242  when the vibration displacement of piezoelectric vibrator  242  is at about a maximum. The corresponding movement of the amplifying plate  243  moves the guide rod  245  and therefore the frame  230  coupled with the guide rod  245  is carried right or left. Herein, the reference numeral  244  denotes a load resistor.  
         [0076]      FIG. 10  is a plan view of an optical pick-up apparatus with a plurality of lenses, in which a linear driving unit is shown according to a second embodiment of the present invention.  
         [0077]     Referring to  FIG. 10 , a linear driving unit  340  utilizes a progressive wave type piezoelectric motor. The linear driving unit  340  includes a fixed vibrator  341  and a metallic friction body  342 . A progressive surface wave is generated on each side of the fixed vibrator, and a pressing and frictional force resulting from the surface wave moves the metallic friction body  342 . Therefore, a frame  230  of an actuator  200  is carried. This piezoelectric motor structure provides a precise transportation even when there is an external or internal disturbance. The actuator  200  may be symmetrically provided with the piezoelectric motor structure. Also, the actuator  200  may be provided at one side with the piezoelectric motor structure when there is a spatial limit.  
         [0078]      FIG. 11  is a plan view of an optical pick-up apparatus with a plurality of lenses, in which a linear driving unit is shown according to a third embodiment of the present invention.  
         [0079]     Referring to  FIG. 11 , a linear driving unit  440  utilizes a dual mode tuning piece type piezoelectric motor. The linear driving unit  440  includes screws  441 , tuning pieces  443 , a piezoelectric ceramic  442 , and a rail guide  444 . The tuning pieces  443  are fixed using the screws  441 , and a spring (not shown) is disposed between the tuning pieces  443 . The tuning pieces  443  vibrate to move the piezoelectric ceramic  442  along the rail guide  444  to carry a frame  230  of an actuator  200  to the direction of arrow Rm or Lm.  
         [0080]      FIG. 12  is a plan view of an optical pick-up apparatus with a plurality of lenses, in which a linear driving unit is shown according to a forth embodiment of the present invention;  
         [0081]     Referring to  FIG. 12 , a linear driving unit  540  utilizes a multi-mode piezoelectric disk type piezoelectric motor. The linear driving unit  540  includes a piezoelectric ceramic  541 , a moving rail guide  542 , and fixed rail guides  543 . The piezoelectric ceramic  541  moves the moving rail guide  542  right or left between the fixed rail guides  543  to carry a frame  230  of an actuator  200 .  
         [0082]     As described above, the optical pick-up apparatus of the present invention can be applied to the optical system using red laser and blue laser. Also, different types of optical disks can be used in the optical system employing the optical pick-up apparatus of the present invention.  
         [0083]     Further, the object lenses are disposed on the lens holder in a linear fashion, and the lens holder is capable of linear reciprocating motion owing to the linear driving unit, such that the lens holder can have simple structure.  
         [0084]     Furthermore, the linear driving unit utilizes the piezoelectric motor, such that the actuator can carry the object lenses to align the object lenses on the optical axis without deviation.  
         [0085]     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and, variations of this invention provided they come within the scope of the appended claims and their equivalents.