Patent Publication Number: US-2007097819-A1

Title: Laser positioning in an optical disc drive

Description:
BACKGROUND  
      Recent advancements have made it possible to employ lasers in optical disc drives to perform the functions of reading data from and writing data to optical discs as well as writing labels or other information on a label surface of optical discs. In one typical scenario, to write data to a disc, the disc is placed in the disc drive and the write function is performed. Thereafter, the disc is removed from the drive, flipped over, and placed back into the drive to write a label to the label surface of the disc. However, in this scenario, the data and labeling operations are performed sequentially, with one beginning after the other one ends. The disc is not completed until both operations are finished. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      The invention can be understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Also, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
       FIG. 1  is a drawing of a first view of relevant components in an optical disc drive employed to direct lasers at both sides of an optical disc according to an embodiment of the present invention;  
       FIG. 2  is a drawing of a view of one example of a laser positioning system employed in the optical disc drive of  FIG. 1  according to an embodiment of the present invention;  
       FIG. 3  is a drawing of a view of another example of a laser positioning system employed in the optical disc drive of  FIG. 1  according to an embodiment of the present invention;  
       FIG. 4  is a schematic block diagram of a disc drive controller employed in the optical disc drive of  FIG. 1  according to another embodiment of the present invention; and  
       FIG. 5  is a flow chart that shows one example of a laser positioning calibration routine executed as a portion of the disc drive controller of  FIG. 4  according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
      The optical disc drives described herein include various components as depicted in the various figures that illustrate the various concepts according to various embodiments of the present invention. However, it is also understood that the optical disc drives may include other components not shown that are not particularly pertinent to the concepts described herein.  
      With reference to  FIG. 1  shown is an optical disc drive  100  according to an embodiment of the present invention. The optical disc drive  100  includes an optical pick up unit  103  that slides along rails  106 . Within the optical pick up unit  103  is a laser  109  which generates a laser beam. The optical disc drive  100  also includes a motor  113 . The motor  113  may be, for example, a stepper motor or other type of motor as can be appreciated. The motor  113  is coupled to a screw shaft  116  that in turn is coupled to the optical pick up unit  103 . The optical disc drive  100  further includes a spindle motor  119  that is employed to spin an optical disc placed in an optical disc site  123  of the optical disc drive  100 . In this respect the optical disc site  123  comprises a three dimensional disc-like volume within which an optical disc may be placed. In this respect, the dimensions of the optical disc site  123  may approximate the dimensions of an optical disc. Also, in various embodiments, the dimensions of an optical disc may fit within the dimensions of the optical disc site  123 . The optical pickup unit  103  may also be termed a “laser head” as it includes the laser  109 .  
      The optical pick up unit  103 , rails  106 , the motor  113 , and screw shaft  116  make up one example of a positioning assembly  126  that is employed to position the laser  109  so that a laser beam generated by the laser  109  may be directed toward a specific location on a first side of the optical disc site  123 . Alternatively, assemblies other than a screw shaft/rail assembly may be employed to position the laser  109  as can be appreciated. The positioning assembly  126  is advantageously configured to position the laser beam generated by the laser  109  with a degree of accuracy and stability to facilitate reading data from and writing data to an optical disc disposed in the optical disc site  123 .  
      The optical disc drive  100  also includes a disc drive controller  133  that generates appropriate electronic signals to drive the motor  113 , the spindle motor  119 , and the various components in the optical pick up unit  103 . Such components may comprise, for example, the laser  109 , and one or more sensors (not shown) as can be appreciated. In this respect, the disc drive controller  133  orchestrates the operation of the optical disc drive  100  in both reading data from and writing data to one side of an optical disc disposed in the optical disc site  123 , and in writing a label to a label side of an optical disc placed within the optical disc site  123 .  
      Next, with reference to  FIG. 2 , shown is a second view of various components of one embodiment of the optical disc drive  100 , denoted herein as optical disc drive  100   a  according to various embodiments of the present invention. The view shown with reference to  FIG. 2  is taken from an opposite direction from the view depicted in  FIG. 1  of the optical disc drive  100 . The optical disc drive  100   a  includes an arm  143  that pivots about a pivot point  146 . Disposed on the arm  143  is a laser  153 , a sensor  155 , and beam shaping optics  156 . The laser  153  generates a laser beam  159  that is shaped by beam shaping optics  156 . The beam shaping optics  156  may comprise, for example, one or more lenses and other optical components as can be appreciated. Disposed at one end of the arm  143  is a reflector  163  that reflects the laser beam  159  generated by the laser  153  onto an optical disc placed in the optical disc site  123  as can be appreciated. The laser  153  may be mounted to the arm  143  in some other manner to direct the laser beam  159  toward an optical disc disposed in the optical disc site  123 . For example, the laser  153  may be attached to the end of the arm  143  and pointed directly at the optical disc provided that the arm  143  is designed to provide adequate stability.  
      An actuator  166  is coupled to the arm  143 . In one embodiment, the actuator  166  is coupled to the arm  143  at a midpoint between the ends of the arm  143 , however it is understood that the actuator  166  may be coupled at any point along the arm  143  that results in the desired motion as will be described. The actuator  166  may comprise, for example, a solenoid, a voice coil motor, or other type of actuator as can be appreciated.  
      The optical disc drive  100   a  also includes an elastic member  169  that is also coupled to the arm  143 . The elastic member  169  is also coupled to a frame structure  173  or other rigid structure of the optical disc drive  100   a . The elastic member  169  opposes the movement of the actuator  166 . In this respect, in one embodiment, the elastic member  169  exerts a force in a direction that is; aligned with a longitudinal axis that defines the direction of motion of the actuator  166 . Alternatively, the elastic member  169  may be oriented such that a component of the force generated opposes the actuator  166  along the longitudinal axis of the actuator  166 . The elastic member  169  may comprise, for example, a spring, an elastic material such as rubber, or other type of elastic structure as can be appreciated.  
      Thus, in one embodiment, where a solenoid is employed as the actuator  166 , a steel core of the solenoid is coupled to the arm  143 . The elastic member  169  may be a spring as described above. The solenoid includes a coil that causes a magnetic force to be exerted onto the steel core by generating a magnetic field as can be appreciated. When a current is generated in the coil, the resulting magnetic field pulls the steel core toward the center of the solenoid. The pulling force is opposed by the spring or other elastic member  169 . For a given solenoid current, the arm  143  settles at an equilibrium point where the force in the spring or other elastic member  169  equals the force on the solenoid core generated by the magnetic force from the solenoid. As the current in the solenoid coil is increased, the equilibrium point moves toward the solenoid itself.  
      The use of a solenoid, voice coil motor or other similar device as the actuator  166  provides a distinct advantage in that the movement of the laser  153  is accomplished at reduced cost. Specifically, solenoids and voice coil motors, for example, are relatively low cost items as compared with other devices that provide higher precision of movement.  
      The disc drive controller  133  includes an output interface with a digital-to-analog converter that is coupled to an input of an analog amplifier  176 . The output of the analog amplifier  176  is coupled to the input of the actuator  166 .  
      Together the arm  143 , actuator  166 , and the elastic member  169  comprise a positioning assembly  179  that is employed to position the laser beam  159  generated by the laser  153  and directed toward the side of the optical disc site  123  by the reflector  163  along a path  193  as will be discussed subsequently in greater detail. The positioning assembly  179  can position the laser beam  159  independent of the positioning of the laser beam generated by the laser  109  by the positioning assembly  126 . The disc drive controller  133  is operatively coupled to the positioning assembly  179  and the positioning assembly  126  to direct the positioning of each.  
      According to one embodiment, the laser  109  is a “data side” laser, and the laser  153  is a “label side” laser. A data side laser is defined herein as a laser that is employed to read or write data to a data region or data surface of an optical disc disposed in the optical disc site  123 . A label side laser is defined herein as a laser employed to write a label to a label region or a label surface of an optical disc disposed in the optical disc site  123 .  
      Next, the operation of the optical disc drive  100   a  is described with reference to both  FIGS. 1 and 2  according to the various embodiments of the present invention. To begin, the disc drive controller  133  controls the laser positioning assembly  126  to position a first laser beam (not shown) generated by the laser  109  and directed toward a first side of the optical disc site  123  in the optical disc drive  100   a . The position of the first laser beam is controlled as such so as to facilitate writing data to or reading data from an optical disc. In this respect, given that the optical pick up unit  123  or laser head is disposed on rails  106  as shown, the laser positioning assembly  126  is thus configured for linear positioning of the first laser beam generated by the laser  109  relative to the optical disc site  123  or relative to an optical disc disposed in the optical disc site  123 . In this respect, a user may place an optical disc in the optical disc drive  100   a  such that the optical disc occupies the optical disc site  123 . Thus, in one embodiment, the positioning assembly  126  employs a screw drive system that moves the optical pick-up unit  103  or laser head based upon rotation of the screw  116  by the motor  113 . However, it is understood that other types of assemblies may be employed.  
      The positioning assembly  179  positions the second laser beam  159  at a point between an inner diameter  183  and an outer diameter  186  of the optical disc site  123 . In this respect, the optical disc site  123  defines a write area  189  between the inner diameter  183  and the outer diameter  186  to which either a label or data may be written to, or data read from an optical disc that occupies the optical disc site  123 . The positioning assembly  179  positions the second laser beam  159  by virtue of a displacement of the actuator  166 . Specifically, in the embodiment shown in  FIG. 2 , the actuator  166  is coupled to the arm  143  and causes the arm  143  to pivot about the pivot point  146 . The elastic member  169  is extended when the actuator  116  causes the arm  143  to pivot toward the inner diameter  183  of the optical disc site  123 . Similarly, the elastic member  169  recovers its non-extended shape when the actuator  166  moves the arm  143  toward the outer diameter  186  of the optical disc site  123 . In this respect, the elastic member  169  generates a force that opposes the movement of the actuator  166  when the actuator  166  pulls the arm  143  toward the inner diameter  183 .  
      The pivotal movement of the arm  143  positions the second laser beam  159  along a path  193  that traces an arc (an arcuate path), for example, on the optical disc site  123 . Thus, the displacement of the actuator  166  causes the pivotal movement of the arm  143  about the pivot point  146 , thereby positioning the second laser beam  159  along the path  193 . Because the arm  143  positions the laser beam  159  along the path  193  tracing the arc from the inner diameter  183  to the outer diameter  186 , the label writing function of the optical disc  100   a  is adjusted to account for displacement of the laser beam  159  along the arc (path  193 ) rather than a straight line path as for the laser  109  that is moved along the rails  106 .  
      The movement of the actuator  166  is caused by the application of a signal, such as a current, generated by the amplifier  176  based upon a signal from the disc drive controller  133 . Specifically, to move the laser beam  159  to a predefined location along the path  193 , the disc drive controller  133  generates a digital value that falls within a range that corresponds to the inner diameter  183  and the outer diameter  186 . This value is converted by the interface described above into an analog value that is applied to the amplifier  176 . In response, the amplifier generates a current that is in turn applied to the actuator  166 , thereby causing the actuator  166  to be displaced in proportion to the magnitude of the current. The elastic member  169  opposes the movement of the actuator  166  in positioning the arm  143  toward the inner diameter  183 .  
      Therefore, the displacement of the actuator  166 , and thus the position of the second laser beam  159 , is controlled by the magnitude of the current applied to the actuator  166 . In this manner, the position of the laser beam  159  may be controlled to facilitate writing a label to the second side of an optical disc disposed in the optical disc site  123 . Because the positioning assembly  179  is entirely independent of the positioning assembly  126 , the positioning of the laser beam  159  is accomplished independent of the positioning of the laser beam generated by the laser  109  ( FIG. 1 ).  
      In addition, while the actuator  166  is shown as providing a linear motion that is coupled to the arm  143 , alternatively, the actuator  166  may be attached to the pivot point  146  and may generate a rotational force that is applied to the arm  143 . Such a rotational force would result in the pivotal motion of the arm  143 . Alternatively, other types of actuators  166  may be employed.  
      The spring  169  may also be of a type that is placed around the pivot point  146  and opposes the pivotal motion of the arm  143  in the direction of the inner diameter  183 . Alternatively, the spring  169  may be embodied in some other configuration that generates a force that opposes the force generated by the actuator  166 .  
      Referring next to  FIG. 3 , shown is a view of another example of components of the optical disc drive  100 , denoted herein as optical disc drive  100   b , according to an embodiment of the present invention. The view of the optical disc drive  100   b  of  FIG. 3  is opposite that of  FIG. 1 . The optical disc drive  100   b  includes the disc drive controller  133 , the amplifier  176 , and the actuator  166 . The actuator  166  is coupled to a laser head  203 . The optical disc drive  100   b  also includes the elastic member  169  that is coupled between the laser head  203  and the support structure  173 . The laser  153  and the sensor  155  reside in the laser head  203 .  
      The optical disc drive  100   b  also includes rails  206 . The laser head  203  is configured to slide along the rails  206 . To this extent, the rails  206  and appropriate portions of the laser head  203  comprise guiding structure that facilitates the linear movement of the laser head  203 . Such guiding structure may include slots or tunnels or other similar features that are compatible with the rails  206  that facilitate the movement of the laser head  203  along the rails  206 . Both the elastic member  169  and the actuator  166  are coupled to the laser head  203  and cause the laser head  203  to move in a linear manner such that the laser  153  may be positioned anywhere from the inner diameter  183  to the outer diameter  186  of the optical disc site  133 . The laser head  203 , rails  206 , elastic member  169 , and the actuator  166  make up positioning assembly  209  that is employed to position the laser  153 , and the laser beam generated thereby, along linear pathway. The disc drive controller  133  is operatively coupled to the positioning assembly  209  in order to direct the positioning of the second laser beam generated by the laser  153  in the laser head  203 .  
      While two rails  206  are shown, it is understood that more or fewer than two rails may be employed. Also, where like numerals are employed to identify various structures in the optical disc drive  100   b  depicted in  FIG. 3  relative to the same components in the optical disc drive  100   a  depicted in  FIG. 2 , such components are substantially similar and any detailed discussion of such components with reference to  FIG. 2  applies to such components depicted in  FIG. 3 . A notable difference between the embodiments of  FIGS. 2 and 3  is that the positioning assembly  179  of  FIG. 2  facilitates the movement of the laser beam  159  along an arc  193 , whereas the positioning assembly  209  of  FIG. 3  facilitates the positioning of a laser beam in a linear direction.  
      With reference to  FIGS. 1-3 , the positioning assemblies  179  and  209  shown provide an advantage in that they are relatively inexpensive to implement. Also, since the positioning assemblies  179  and  209  both operate independently of the positioning of the laser  109  by the positioning assembly  126 , the positioning assembly  126  is not further loaded with the burden of also positioning the laser beam  159 .  
      Referring then to  FIG. 4 , shown is one embodiment of the disc drive controller  133  according to an embodiment of the present invention. In this respect, the disc drive controller  133  comprises the processor circuit having a processor  233  and memory  236 , both of which are coupled to a local interface  239 . The local interface  239  may comprise, for example, a data bus with an accompanying control/address bus as can be appreciated. The processor circuit may comprise, for example, any one of a number of different commercially available microcontroller circuits as can be appreciated.  
      Stored in the memory  236  and executable by the processor  233  are a number of components including, for example, an operating system  243 , and a drive control system  246 . The operating system  243  controls the allocation and usage of hardware resources such as the memory, processing time, and peripheral devices in the disc drive controller  133 . In this manner, the operating system  243  serves as the foundation on which applications depend as is generally known by those with ordinary skill in the art.  
      The drive control system  246  controls the various functions of the optical disc drive  100 . A portion of the drive control system  246  comprises a laser position calibration routine  249 . In addition, it is understood that other portions of the drive control system  246  exist that are not described herein in detail. The laser position calibration routine  249  is executed to calibrate the positioning of the laser beam  159  ( FIG. 2 ).  
      The components stored in the memory  236  may be executable by the processor  233 . In this respect, the term “executable” means a program file that is in a form that can ultimately be run by the processor  233 . Examples of executable programs may be, for example, a compiled program that can be translated into machine code in a format that can be loaded into a random access portion of the memory  236  and run by the processor  233 , etc. An executable program may be stored in any portion or component of the memory  236  including, for example, random access memory, read-only memory, a hard drive, compact disk (CD), floppy disk, or other memory components.  
      The memory  236  is defined herein as both volatile and nonvolatile memory and data storage components. Volatile components are those that do not retain data values upon loss of power. Nonvolatile components are those that retain data upon a loss of power. Thus, the memory  236  may comprise, for example, random access memory (RAM), read-only memory (ROM), hard disk drives, floppy disks accessed via an associated floppy disk drive, compact discs accessed via a compact disc drive, magnetic tapes accessed via an appropriate tape drive, and/or other memory components, or a combination of any two or more of these memory components. In addition, the RAM may comprise, for example, static random access memory (SRAM), dynamic random access memory (DRAM), or magnetic random access memory (MRAM) and other such devices. The ROM may comprise, for example, a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or other like memory device.  
      In addition, the processor  233  may represent multiple processors and the memory  236  may represent multiple memories that operate in parallel. In such a case, the local interface  239  may be an appropriate network that facilitates communication between any two of the multiple processors, between any processor and any one of the memories, or between any two of the memories etc. The processor  233  may be of electrical, optical, or molecular construction, or of some other construction as can be appreciated by those with ordinary skill in the art.  
      Referring next to  FIG. 5 , shown is a flow chart that provides one example of the operation of the laser position calibration routine  249  according to an embodiment of the present invention. Alternatively, the flow chart of  FIG. 5  may be viewed as depicting steps of an example of a method implemented to calibrate the positioning of the laser beam  159 . The functionality of the laser position calibration routine  249  as depicted by the example flow chart of  FIG. 5  may be implemented, for example, in an object oriented design or in some other programming architecture. If the functionality is implemented in an object oriented design, then each block represents functionality that may be implemented in one or more methods that are encapsulated in one or more objects. The laser position calibration routine  249  may be implemented using any one of a number of programming languages such as, for example, C, C++, Assembly, or other programming languages along with the programming of the entire drive control system  243 .  
      The laser position calibration routine  249  begins with box  253  in which an attempt is made to locate a calibration position along the movement of the second laser beam  159 . In some embodiments, this calibration position may be considered a second calibration position where the first calibration postion is the rest position when a zero current is applied to the actuator  166 . The laser position calibration routine  249  advantageously calibrates the positioning of the laser beam  159  based upon inputs received at two or more separate positions within the range of motion of the laser beam  159 .  
      One or more of the calibration positions may be specified based on the location of reflective materials strategically placed either on an optical disc disposed in the optical disc site  123 , or upon a given structure to which the laser  159  is directed when an optical disc is not disposed in the optical disc site. The reflective materials may include reflective structures such as mirrors that are configured to reflect of at least a portion of the laser beam  159 . For example, one calibration point may be a point of transition between high reflectivity and low reflectivity of the edge of the outer ring media inner diameter (ID) on an optical disc placed in the optical disc site  123 . Another calibration point may be, for example, the transition point from low reflectivity to high reflectivity corresponding to the edge of the write area  189 .  
      The sensor  155  may be located on the arm  143  ( FIG. 2 ), the laser head  203  ( FIG. 2 ), or other location to receive the reflected laser light. When the reflected laser light is at a maximum, for example, it may be assumed that the laser beam  159  is directed at the corresponding reflective material and thus at the desired calibration position.  
      In box  256 , assuming that the laser beam  159  is directed at the desired calibration position, then the laser position calibration routine  249  proceeds to box  258 . Otherwise, the laser position calibration routine  249  proceeds to box  263 . In box  263  the position of the laser beam  159  is adjusted to determine if the calibration position can be located. Thereafter, the laser position calibration routine  249  reverts back to box  256 .  
      In box  258 , the laser position calibration routine  249  determines whether the last calibration position has been located such that information relative to at least two such calibration positions is known. For example, if the rest position is taken as one of the two calibration positions, then only one other calibration positions need be located. On the other hand, if the rest position is not employed as one of the calibration positions, then at least two calibration positions within the range of motion of the laser beam  159  are located. When each of the calibration positions is located, the current or voltage applied to the actuator  166  is stored in order to calculate the gain therefrom. If in box  258 , the desired number of calibration positions has been located from which the gain of the system may be calculated, then the laser position calibration routine  249  proceeds to box  259 . Otherwise, the laser position calibration routine  249  reverts back to box  253  to locate the next calibration position.  
      When the laser position calibration routine  249  has progressed to box  259 , then the gain of the actuator  166  is calculated. In this respect, the gain is calculated based upon the difference in the current or voltage applied to the actuator  166  in moving the arm  143  or laser head  203  from the rest position (or other initial calibration position) to a second calibration position. Since the distance between the two calibration positions is known, the gain may be calculated as a function of the voltage or current per unit length. In one embodiment, the analog voltage or current applied to the actuator  166  is generated by D/A converter that converts a digital position signal (digital value) into a corresponding analog voltage or current. Thus, analog voltage or current applied to the actuator  166  falls within a range that corresponds to the range of motion of the actuator  166 . Since the gain varies over time, in box  266 , the laser position calibration routine  249  calculates the range of digital values that corresponds to the total range of analog voltage or current that is applied to the actuator  166  to accomplish the full range of motion of the laser beam  159  given the calculated gain. Then, in box  269 , these values are stored in the disc drive controller  133  for use in the laser position control. Then, the laser position calibration routine  249  ends as shown. In this manner, the laser position calibration routine  249  accounts for changes in the operation and gain of the respective positioning assemblies  179  or  209 .  
      In order to ensure that the positioning of the arm  143  or laser head  203  is accurate over time, the laser position calibration routine  249  may be executed periodically at specific time intervals. Alternatively, the laser position calibration routine  249  may be performed before the writing of a label to each optical disc disposed in the optical disc site  123 . As an alternative, the laser position calibration routine  249  may be executed according to some other schedule or scheme.  
      Although the laser position calibration routine  249  is described as being embodied in software or code executed by general purpose hardware as discussed above, as an alternative the same may also be embodied in dedicated hardware or a combination of software/general purpose hardware and dedicated hardware. If embodied in dedicated hardware, the laser position calibration routine  249  can be implemented as a circuit or state machine that employs any one of or a combination of a number of technologies. These technologies may include, but are not limited to, discrete logic circuits having logic gates for implementing various logic functions upon an application of one or more data signals, application specific integrated circuits having appropriate logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), or other components, etc. Such technologies are generally well known by those skilled in the art and, consequently, are not described in detail herein.  
      The flow chart of  FIG. 5  shows the architecture, functionality, and operation of an implementation of the laser position calibration routine  249 . If embodied in software, each block may represent a module, segment, or portion of code that comprises program instructions to implement the specified logical function(s). The program instructions may be embodied in the form of source code that comprises human-readable statements written in a programming language or machine code that comprises numerical instructions recognizable by a suitable execution system such as a processor in a computer system or other system. The machine code may be converted from the source code, etc. If embodied in hardware, each block may represent a circuit or a number of interconnected circuits to implement the specified logical function(s).  
      Although the flow chart of  FIG. 5  shows a specific order of execution, it is understood that the order of execution may differ from that which is depicted. For example, the order of execution of two or more blocks may be scrambled relative to the order shown. Also, two or more blocks shown in succession in  FIG. 5  may be executed concurrently or with partial concurrence. In addition, any number of counters, state variables, warning semaphores, or messages might be added to the logical flow described herein, for purposes of enhanced utility, accounting, performance measurement, or providing troubleshooting aids, etc. It is understood that all such variations are within the scope of the present invention.  
      Also, where the laser position calibration routine  249  comprises software or code, it can be embodied in any computer-readable medium for use by or in connection with an instruction execution system such as, for example, a processor in a computer system or other system. In this sense, the logic may comprise, for example, statements including instructions and declarations that can be fetched from the computer-readable medium and executed by the instruction execution system. In the context of the present invention, a “computer-readable medium” can be any medium that can contain, store, or maintain the laser position calibration routine  249  for use by or in connection with the instruction execution system. The computer readable medium can comprise any one of many physical media such as, for example, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor media. More specific examples of a suitable computer-readable medium would include, but are not limited to, magnetic tapes, magnetic floppy diskettes, magnetic hard drives, or compact discs. Also, the computer-readable medium may be a random access memory (RAM) including, for example, static random access memory (SRAM) and dynamic random access memory (DRAM), or magnetic random access memory (MRAM). In addition, the computer-readable medium may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or other type of memory device.  
      In addition, with reference to  FIGS. 1-3 , various methods of use are provided relative to the optical disc drive  100 . Specifically, according to one embodiment of the present invention, a method is provided for positioning a laser in an optical disc drive  100  comprising the steps of positioning a first laser beam generated by a first laser and directed toward a first side of an optical disc in an optical disc drive to read data from or write data to an optical disc. In addition, the method comprises the step of positioning a second laser beam generated by a second laser and directed toward a second side of the optical disc in the optical disc drive.  
      The positioning of the second laser beam is performed independent of the positioning of the first laser beam. In addition, the example method may further comprise the step of writing a label on the second side of the optical disc using the second laser beam. A user may insert the optical disc into the optical disc drive and then perform steps of positioning the first laser beam, positioning the second laser beam, and writing a label without removing the optical disc from the optical disc drive. Thereafter, the optical disc may be removed from the optical disc drive after performing all of the steps of positioning the first laser beam, positioning the second laser beam, and writing a label have been completed.  
      A user may advantageously employ the optical disc drive  100  to both read data from/write data to an optical disc while at the same time writing a label to an opposite side of the optical disc without having to remove the optical disc from the disc drive to flip it over to facilitate separate functions of reading/writing and writing a label using a single laser. In addition, the present invention facilitates simultaneous performance of the steps of reading data from/writing data to the optical disc and writing a label to the optical disc.  
      Although the invention is shown and described with respect to certain embodiments, it is obvious that equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalents and modifications, and is limited only by the scope of the claims.