Abstract:
A method and related apparatus used for moving an optical processing unit (OPU) of an optical disc drive toward an initial position before the optical disc drive accesses optical disc data is disclosed. The method includes: providing a driving force to drive the OPU; determining whether or not the OPU starts to move; and increasing the driving force if the OPU does not move yet. Further, once the OPU is moving, speed control is maintained through use of a controller and a detecting device.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an optical disc drive, and more particularly, to a method and apparatus for moving an optical processing unit in an optical disc drive before accessing an optical disc.  
         [0003]     2. Description of the Prior Art  
         [0004]     With the rapid developments of information technologies and the electronic industry, many consumer electronics have become smaller, lighter and more portable. This has resulted in users conveniently enjoying information technologies anytime and anywhere. In order to make the electronic products useable in an increased number of user mobile situations including walking, running, driving, or riding, one important design consideration is making the electronic products operable in a variety of physical positions.  
         [0005]     Please refer to  FIG. 1 , which depicts a simplified schematic diagram of a conventional portable optical disc drive  100 . The portable optical disc drive  100  comprises a spindle motor  110  for rotating an optical disc; an optical processing unit (OPU)  120  for reading data from the optical disc; and a sled motor  130  for driving the OPU  120  to slide along a sliding track  140 . The OPU  120  utilizes a pick-up head  150  to access data. To reduce cost in the prior art, the sled motor  130  is typically implemented with a DC motor.  FIG. 2  depicts a schematic diagram of the portable optical disc drive  100  rotated 180 degrees compared to  FIG. 1 .  
         [0006]     When the portable optical disc drive  100  is turned off, the position of the OPU  120  may be changed with the motion of the user or the manner that portable optical disc drive  100  is set or placed. Since the actual position of the OPU  120  is unknown, the portable optical disc drive  100  forces the OPU  120  to return to an initial position before reading an optical disc. In conventional art, regardless the displacement of the portable optical disc drive  100 , the sled motor  130  provides a first fixed force to drive the OPU  120  to slide inward until the OPU  120  reaches a limit device (not shown) near the spindle motor  110 . Afterward, the sled motor  130  then provides an inverse second fixed force within a constant period to drive the OPU  120  to slide outward to an initial position of the optical disc in order to perform a track-seeking procedure.  
         [0007]     As mentioned above, the conventional sled motor  130  uses fixed force to drive the OPU  120 , so that the moving velocity of the OPU  120  is uniformly accelerated. Accordingly, the further the OPU  120  is from the spindle motor  110 , the greater the impact of the OPU  120  will be against the limit device. Moreover, the influence caused by gravity is ignored in the prior art. For example, gravity slows down the motion of the OPU  120  in the position shown in  FIG. 1 , but speeds up the motion of the OPU  120  in the position shown in  FIG. 2 . Therefore, when gravity is beneficial for the OPU  120  to slide inward (such as under the displacement of  FIG. 2 ), the conventional homing procedure of the OPU  120  may greatly increase the impact of the OPU  120  against the limit device and thereby induce unfavorable noise. Furthermore, the lifespan of the OPU  120  is accordingly reduced.  
         [0008]     On the other hand, after the OPU  120  touches the limit device in the prior art, since the sled motor  130  then provides the second fixed force within a constant period to drive the OPU  120  to slide outward, the moving distance of the OPU  120  may also be affected by gravity. The effect in this instance may cause final position of the OPU  120  to differ from the initial position of the optical disc. In this situation, the required time for the portable optical disc drive  100  to perform track-seeking procedure is increased and the access performance is thereby affected.  
       SUMMARY OF INVENTION  
       [0009]     It is therefore an objective of the claimed invention to provide a method for moving an optical processing unit (OPU) in an optical disc drive to solve the above-mentioned problem by controlling the moving speed of the OPU using feedback control manner.  
         [0010]     According to a preferred embodiment, the method used for moving the OPU toward an initial position in the optical disc drive before the optical disc drive accesses an optical disc. The method comprises providing a driving force to drive the OPU; determining whether the OPU starts moving or not; and increasing the driving force if the OPU does not move yet.  
         [0011]     Another objective of the present invention to provide a sled actuator in an optical disc drive for moving an optical processing unit (OPU) of the optical disc drive toward an initial position before the optical disc drive accesses an optical disc. The sled actuator comprises: a sled motor for providing a driving force to drive the OPU; a detecting device electrically connected to the sled motor for detecting the moment of the OPU to generate a corresponding detection signal; and a control circuit electrically connected to the sled motor and the detecting device for controlling the sled motor to adjust the driving force according to the detection signal.  
         [0012]     One advantage of the present invention is that the OPU can slide in a feasible constant velocity to reduce the impact and noise of the OPU against other components, and the lifespan of components of the optical disc drive are thereby extended.  
         [0013]     Another advantage of the present invention is that the OPU will slide to the initial position of the optical disc accurately to reduce the required time for accessing data.  
         [0014]     Yet another advantage of the present invention is that the sled motor of the sled actuator can be implemented with a DC motor to reduce cost.  
         [0015]     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0016]      FIG. 1  is a schematic diagram of a conventional portable optical disc drive.  
         [0017]      FIG. 2  is a schematic diagrams of the conventional portable optical disc drive of  FIG. 1 , with its position rotated 180 degrees.  
         [0018]      FIG. 3  is a schematic diagram of an optical disc drive according to the present invention.  
         [0019]      FIG. 4  is a schematic diagram of an embodiment of a sled actuator of the optical disc drive of  FIG. 3 .  
         [0020]      FIG. 5  is a flowchart describing the steps to drive an OPU of the optical disc drive of  FIG. 3  to slide to the innermost position along a sliding track using the sled actuator shown in  FIG. 4 .  
         [0021]      FIG. 6  is a plot of detection signals generated by a detecting device of the sled actuator of  FIG. 4 .  
         [0022]      FIG. 7  is a flowchart describing the steps to drive the OPU of the optical disc drive of  FIG. 3  to slide outward to the initial position of the optical disc using the sled actuator of  FIG. 4 . 
     
    
     DETAILED DESCRIPTION  
       [0023]     Please refer to  FIG. 3 , which depicts a simplified schematic diagram of an optical disc drive  300  according to the present invention. The optical disc drive  300  comprises a spindle motor  310  for rotating an optical disc  350 ; an optical processing unit (OPU)  320  for accessing the optical disc  350 ; and a sled actuator  330  for driving the OPU  320  to slide along a sliding track  340 . In practical implementations, the optical disc drive  300  of the present invention can be any kind of portable CD/DVD player or recorder.  
         [0024]      FIG. 4  depicts a schematic diagram of one embodiment of the sled actuator  330  of  FIG. 3 . The sled actuator  330  comprises a sled motor  410  for proving a driving force to drive the OPU  320 ; a detecting device  420  electrically connected to the sled motor  410  for detecting the moment of the OPU to generate a corresponding detection signal; and a control circuit  430  electrically connected to the sled motor  410  and the detecting device  420 , the control circuit  430  for controlling the sled motor to adjust the driving force according to the detection signal in order to maintain the moving speed of the OPU  320  within a predetermined range. In a preferred embodiment, the sled motor  410  can be implemented with a DC motor to reduce cost, and the control circuit  430  can be the microprocessor of the optical disc drive  300 .  
         [0025]     The detecting device  420  of the sled actuator  330  further includes a gear wheel  422  installed on a shaft  412  of the sled motor  410 ; and a photo interrupter module  424  for detecting the rotation of the gear wheel  422 . When the sled motor  410  operates, its shaft  412  drives the OPU  320  through a transmission mechanism and also rotates the gear wheel  422 . As is well known in the art, a gear combination, a belt, a sawtooth bar, or the like can be implemented as the transmission mechanism, and as such further details are omitted here.  
         [0026]     As mentioned above, before the optical disc drive  300  starts to access the optical disc  350 , the sled actuator  330  moves the OPU  320  to a proper position so that a pick-up head (not shown) of the OPU  320  can perform the track-seeking operation. The above movement can be separated into two stages. In the first stage, the OPU  320  is moved along the sliding track  340  from any position to the innermost position, where the OPU  320  touches a limit device near the spindle motor  310 . In the second stage, the OPU  320  is moved outward to an initial position of the optical disc  350 . The operations of the sled actuator  330  in above two stages are described with flowcharts in following.  
         [0027]     Please refer to  FIG. 5 , which depicts a flowchart of how the sled actuator  330  drives the OPU  320  to slide to the innermost position along the sliding track  340  according to the present invention. The flowchart includes following steps:  
         [0028]     Step  502 : Start.  
         [0029]     Step  504 : Provide a driving force F 1  to the OPU  320 .  
         [0030]     Step  506 : Determine whether the OPU  320  starts moving. If the OPU  320  moves, perform step  510 , otherwise, perform step  508 .  
         [0031]     Step  508 : Increase the driving force F 1 .  
         [0032]     Step  510 : Reduce the driving force F 1  so that the OPU  320  slides toward the innermost position of the sliding track  340  with a predetermined speed.  
         [0033]     Step  512 : Generate a corresponding detection signal according to the movement of the OPU  320 .  
         [0034]     Step  514 : Adjust the driving force F 1  according to the detection signal to maintain the moving speed of the OPU  320  within a predetermined range.  
         [0035]     Step  516 : When the detection signal does not occur over a predetermined period, stop providing the driving force F 1 .  
         [0036]     Step  518 : End.  
         [0037]     Since the OPU  320  is static at the beginning, the sled motor  410  provides the driving force F 1  to the OPU  320  in step  504 .  
         [0038]     In the following step  506 , the control circuit  430  determines whether or not the OPU  320  starts to move. If the OPU  320  does not move, it means the driving force F 1  provided by the sled motor  410  can not overcome the force of static friction (possibly made worse due to the gravity effect) of the OPU  320 . Therefore, the control circuit  430  controls the sled motor  410  to progressively increase the driving force F 1  to drive the OPU  320  to move.  
         [0039]     While the OPU  320  slides, the driving force needed to drive the OPU  320  can be reduced. Therefore, the sled motor  410  reduces the driving force F 1  in step  510 , so that the OPU  320  slides toward the innermost position of the sliding track  340  at a proper predetermined speed.  
         [0040]     In steps  512  and  514 , the sled actuator  330  of the present invention constantly adjusts the driving force F 1  based on the movement situation of the OPU  320  to maintain the moving speed of the OPU  320  within the predetermined range. For example, in the embodiment shown in  FIG. 4 , when the OPU  320  moves, it means that the shaft  412  of the sled motor  410  is rotated, and the gear wheel  422  is also rotated. Therefore, in step  512 , when the sawtooth edges of the gear wheel  422  pass the groove of the photo interrupter module  424 , the photo interrupter module  424  generates a corresponding detection signal according to the detected ruminate change as shown in  FIG. 6 . In a preferred embodiment, the number of pulses of the detection signal in  FIG. 6  corresponds to the number of rotated teeth of the gear wheel  422 . Accordingly, it is known that the number of the pulses of the detection signal also corresponds to the moved distance of the OPU  320 . In other words, the photo interrupter module  424  can detect the movement of the OPU  320  according to the rotation of the gear wheel  422  in step  512 .  
         [0041]     Next, in step  514 , the control circuit  430  of the sled actuator  330  converts the number of pulses of the detection signal generated within a unit period to the moving speed of the OPU  320 . In addition, the control circuit  430  adjusts the driving force F 1  provided by the sled motor  410  according to the calculated moving speed to maintain the moving speed of the OPU  320  within the predetermined range. In practical implementations, the control circuit  430  can adjust the magnitude of the driving force F 1  by adjusting the input voltage of the sled motor  410 .  
         [0042]     The OPU  320  cannot slide further forward when it arrives at the innermost position of the sliding track  340 , where the OPU  320  contacts the limit device near the spindle motor  310 . At this moment, both the shaft  412  and the gear wheel  422  stop rotating, such that the pulses of the detection signal stop occurring. Accordingly, in step  516 , if the photo interrupter module  424  does not generate any detection signal over a predetermined period, the control circuit  430  determines that the OPU  320  has contacted with the limit device, and the control circuit  430  controls the sled motor  410  to stop providing the driving force F 1 .  
         [0043]     Next refer to  FIG. 7 , which depicts a flowchart showing how the sled actuator  330  drives the OPU  320  to slide outward to an initial position of the optical disc  350  according to the present invention. The flowchart comprises following steps:  
         [0044]     Step  702 : Start.  
         [0045]     Step  704 : Provide a driving force F 2  to the OPU  320 .  
         [0046]     Step  706 : Determine whether the OPU  320  starts moving or not. If the OPU  320  moves, perform step  710 , otherwise, perform step  708 .  
         [0047]     Step  708 : Increase the driving force F 2 .  
         [0048]     Step  710 : Reduce the driving force F 2  so that the OPU  320  slides toward the initial position of the optical disc  350  with a predetermined speed.  
         [0049]     Step  712 : Generate a corresponding detection signal according to the movement of the OPU  320 .  
         [0050]     Step  714 : Adjust the driving force F 2  according to the detection signal to maintain the moving speed of the OPU  320  within a predetermined range.  
         [0051]     Step  716 : When the pulses of the detection signal reach a predetermined number, stop providing the driving force F 2 .  
         [0052]     Step  718 : End.  
         [0053]     The steps  704  through  714  are substantially the same with foregoing steps  504  through  514 . The only difference is that the moving directions of the OPU  320  are opposite, and the further details are omitted for brevity.  
         [0054]     As mentioned above, the number of rotated teethes of the gear wheel  422  corresponds to the moving distance of the OPU  320 . Thus, in step  716 , when the pulses of the detection signal generated from the photo interrupter module  424  reach to a predetermined number, it means that the OPU  320  has moved outward a specific distance from the innermost position of the sliding track  340 . Accordingly, the control circuit  430  determines that the OPU  320  has arrived to the initial position of the optical disc  350 , so that the control circuit  430  controls the sled motor  410  stop providing the driving force F 2 . In practice, the predetermined number relates to the diameter of the gear wheel  422  and the distance between teeth thereof, and not limited to a specific number.  
         [0055]     As mentioned, while the sled actuator  330  of the present invention moves the OPU  320 , the control circuit  430  adjusts the output force of the sled motor  410  according to the detection signal generated from the sled motor  410  to maintain the moving speed of the OPU  320  within a predetermined range. As a result, the impact and noise of the OPU  320  against the limit device are greatly reduced and lifespan of components are thereby extended. In addition, the sled actuator  330  can accurately move the OPU  320  to the initial position of the optical disc  350  to speed up following track-seeking procedures in accordance with the number of pulses of the detection signal generated by the detecting device  420 . Furthermore, the sled motor  410  of the sled actuator  330  can be implemented with a DC motor to reduce cost and increase the competency of the products.  
         [0056]     Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.