CROSS-REFERENCE TO RELATED PATENT APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2004-92336, filed on Nov. 12, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method of determining a type of optical disc, and more particularly, to a method of quickly and accurately determining a type of optical disc, and a data recording and/or reproducing apparatus incorporating the method.  
         [0004]     2. Description of the Related Art  
         [0005]     Various types of information storage media include magnetic discs such as floppy discs and hard discs, magnetic tapes, semiconductor memory chips such as read-only memory (ROM) and random access memory (RAM), and optical discs using a laser to record data.  
         [0006]     As for optical discs, inexpensive storage capacity is rapidly increasing with the development of relevant technology. Thus, optical discs are very widely used. Optical discs may be divided into various types such as compact discs (CDs), digital video discs (DVDs), and Blu-ray discs (BDs) according to storage capacity.  
         [0007]     Usually, a data recording and/or reproducing apparatus can record data onto and/or reproduce data from various types of optical discs. When an optical disc is loaded, a data recording and/or reproducing apparatus determines a type of the optical disc before writing data onto or reading data from the optical disc. The type of the optical disc may be exactly identified by reproducing data stored in a lead-in area on the optical disc, but the data recording and/or reproducing apparatus cannot reproduce data before identifying the type of the optical disc.  
         [0008]     According to an example of conventional technology, a type of an optical disc is determined using a predetermined sequence. For example, when a sequence predetermined by a manufacturer of a data recording and/or reproducing apparatus is BD, DVD, and CD, the data recording and/or reproducing apparatus determines whether a loaded optical disc is a BD. To determine whether the optical disc is the BD, the data recording and/or reproducing apparatus sets various data including a power value of a laser diode corresponding to the BD. Thereafter, the data recording and/or reproducing apparatus determines whether the optical disc is the BD based on a signal obtained by radiating a laser beam onto the optical disc while moving an objective lens toward and away from the optical disc. However, if the optical disc is determined as not being the BD, the data recording and/or reproducing apparatus determines whether the optical disc is a DVD. Similarly to the above-described determining operation, the data recording and/or reproducing apparatus sets various data including the power value of a laser diode corresponding to the DVD and determines whether the optical disc is the DVD based on a signal obtained by radiating a laser beam onto the optical disc while moving the objective lens toward and away from the optical disc. If the optical disc is determined as not being the DVD, whether the optical disc is a CD is determined. If the optical disc is determined as not being a CD, the data recording and/or reproducing apparatus finally determines the optical disc as an unknown disc.  
         [0009]     According to the conventional technology, since many operations are needed to determine a type of optical disc loaded into a data recording and/or reproducing apparatus, a type determination procedure for optical discs is complicated and takes time.  
       SUMMARY OF THE INVENTION  
       [0010]     An aspect of the present invention provides a method of quickly and accurately determining a type of optical disc loaded in a recording and/or reproducing apparatus.  
         [0011]     An aspect of the present invention provides a data recording and/or reproducing apparatus for quickly and accurately determining a type of an optical disc loaded in the apparatus.  
         [0012]     According to an aspect of the present invention, there is provided a method of determining a type of an optical disc loaded into a data recording and/or reproducing apparatus, which includes a plurality of laser diodes and records data onto and/or reproduces data from diverse types of optical discs. The method includes selecting one laser diode from among the plurality of laser diodes, radiating light onto the loaded optical disc while approaching and/or withdrawing the selected laser diode to and from the loaded optical disc, counting a number of reflection signals generated from the light reflected from the loaded optical disc, and determining the type of the loaded optical disc based on a number of the reflection signals.  
         [0013]     The determining of the type of the loaded optical disc may be performed based on the number of reflection signals being different according to a distance between a surface and a data layer of the loaded optical disc and a working distance of the selected laser diode.  
         [0014]     The determining of the type of the loaded optical disc may be performed based on whether there is a reflection signal from a data layer of the loaded optical disc.  
         [0015]     The selecting of one laser diode may include selecting a laser diode having a shortest working distance among the plurality of laser diodes.  
         [0016]     The loaded optical disc may be a compact disc, a digital video disc, or a Blu-ray disc. The number of reflection signals may be at least 2 when the loaded optical disc is the Blu-ray disc. The number of reflection signals may be 1 when the loaded optical disc is one of the compact disc and the digital video disc.  
         [0017]     Where the loaded optical disc is determined as the compact disc or the digital video disc, the method may further include selecting another laser diode from among the plurality of laser diodes, radiating light onto the loaded optical disc while approaching and/or withdrawing the selected another laser diode to and from the loaded optical disc, and determining whether the loaded optical disc is the compact disc or the digital video disc based on a time interval between a reflection signal from a surface of the loaded optical disc and a reflection signal from a data layer of the loaded optical disc.  
         [0018]     According to another aspect of the present invention, there is provided a data recording and/or reproducing apparatus which records data onto and/or reproduces data from diverse types of optical discs. The data recording and/or reproducing apparatus includes a writing/reading unit including a plurality of laser diodes and writing data to and/or reading data from an optical disc loaded into the data recording and/or reproducing apparatus; and a control unit selecting one laser diode from among the plurality of laser diodes, controlling the selected laser diode to radiate light onto the loaded optical disc while controlling the writing/reading unit to approach and/or withdraw from the loaded optical disc, and determining a type of the loaded optical disc based on a number of reflection signals generated from the light reflected from the loaded optical disc  
         [0019]     The control unit may determine the type of the loaded optical disc based on the number of the reflection signals being different according to a distance between a surface of the loaded optical disc and a data layer of the loaded optical disc and a working distance of the selected laser diode.  
         [0020]     The control unit may determine the type of the loaded optical disc based on whether there is a reflection signal from a data layer of the loaded optical disc.  
         [0021]     The control unit may select a laser diode having a shortest working distance among the plurality of laser diodes.  
         [0022]     The loaded optical disc may be a compact disc, a digital video disc, or a Blu-ray disc. The number of reflection signals may be at least 2 when the loaded optical disc is the Blu-ray disc. The number of reflection signals may be 1 when the loaded optical disc is the compact disc or the digital video disc.  
         [0023]     When the loaded optical disc is determined as the compact disc or the digital video disc, the control unit may re-select another laser diode from among the plurality of laser diodes, control the re-selected another laser diode to radiate light onto the loaded optical disc while controlling the writing/reading unit to come close to and go away from the loaded optical disc, and determine the loaded optical disc is the compact disc or the digital video disc based on a time interval between a reflection signal from a surface of the loaded optical disc and a reflection signal from a data layer of the loaded optical disc.  
         [0024]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0026]      FIG. 1A  illustrates a cross-section of a Blu-ray disc (BD) with a single recording layer;  
         [0027]      FIG. 1B  illustrates a cross-section of a digital video disc (DVD) with a single recording layer;  
         [0028]      FIG. 1C  illustrates a cross-section of a compact disc (CD);  
         [0029]      FIG. 2A  illustrates a state where light is focused onto a data layer of an optical disc;  
         [0030]      FIG. 2B  illustrates a state where light is not focused onto a data layer of an optical disc;  
         [0031]      FIG. 3A  illustrates a case where a reflection signal obtained from light reflected from a surface of an optical disc and a reflection signal obtained from light reflected from a data layer of the optical disc are both present;  
         [0032]      FIG. 3B  illustrates a case where only a reflection signal obtained from light reflected from a surface of an optical disc is present;  
         [0033]      FIG. 4  is a block diagram of a data recording and/or reproducing apparatus according to an embodiment of the present invention;  
         [0034]      FIG. 5  is a flowchart of a method of determining a type of optical disc according to an embodiment of the present invention;  
         [0035]      FIG. 6A  illustrates a time interval between a reflection signal from a surface of a DVD and a reflection signal from a data layer of the DVD;  
         [0036]      FIG. 6B  illustrates a time interval between a reflection signal from a surface of a CD and a reflection signal from a data layer of the CD;  
         [0037]      FIG. 7  is a flowchart of a method of determining a type of optical disc according to another embodiment of the present invention;  
         [0038]      FIG. 8  is a block diagram of the writing/reading unit shown in  FIG. 4 ; and  
         [0039]      FIG. 9  is a block diagram of the control unit shown in  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0040]     Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
         [0041]      FIG. 1A  illustrates a cross-section of a Blu-ray disc (BD)  10  with a single recording layer. The BD  10  is a next-generation high-density disc with a recording capacity of at least 15 Gbytes. Data is recorded onto the BD  10  using a blue laser diode generating 405-nm wavelength light. The BD  10  has a thickness of about 1.2 mm. A distance between a surface  11  and a data layer  13  of the BD  10  is about 0.1 mm.  
         [0042]      FIG. 1B  illustrates a cross-section of a digital video disc (DVD)  30  with a single recording layer. The DVD  30  has a thickness of about 1.2 mm like a BD and a compact disc (CD). A distance between a surface  31  and a data layer  33  of the DVD  30  is about 0.6 mm.  
         [0043]      FIG. 1C  illustrates a cross-section of a compact disc (CD)  50 . A distance between a surface  51  and a data layer  53  of the CD  50  is about 1.2 mm.  
         [0044]     As described above, the distance between a surface ( 11 ,  31 ,  51 ) and a data layer ( 13 ,  33 ,  53 ) increases in order of BD, DVD, and CD. A writing and/or reading unit provided in a data recording and/or reproducing apparatus, which can record data onto and/or reproduce data from various types of optical discs, includes a laser diode corresponding to each type of optical disc for which the recording and/or reproducing apparatus is useable. For example, a writing and/or reading unit provided in a data recording and/or reproducing apparatus that can record data onto and/or reproduce data from BDs, DVDs, and CDs includes three types of laser diodes, i.e., a BD laser diode, a DVD laser diode, and a CD laser diode.  
         [0045]      FIG. 2A  illustrates a state where a light  70  emitted from a BD laser diode ( FIG. 8 ) is focused by an objective lens  60  onto the data layer  13  of the BD  10 . Here, a working distance is about 0.5 mm. Usually, a working distance is a distance between a surface of a disc and an objective lens when light is focused on a data layer of the disc.  
         [0046]      FIG. 2B  illustrates a state where the light  70  generated by the BD laser diode is radiated onto the DVD  30  via the objective lens  60 . Since the working distance of the BD laser diode is about 0.5 mm and the distance between the surface  31  and the data layer  33  of the DVD  30  is about 0.6 mm, the light cannot be focused onto the data layer  33  of the DVD  30 .  
         [0047]     When the BD  10  is loaded into a data recording and/or reproducing apparatus and the data recording and/or reproducing apparatus turns on the BD laser diode and radiates light onto the BD  10  while moving the writing and/or reading unit toward and away from the optical disc, to focus the light, two reflection signals are obtained as shown in  FIG. 3A . One is a reflection signal  81  obtained from light reflected from the surface  11  of the BD  10  and the other is a reflection signal  82  obtained from light reflected from the data layer  13  of the BD  10 .  
         [0048]     However, when the DVD  30  is loaded into a data recording and/or reproducing apparatus and the data recording and/or reproducing apparatus turns on the BD laser diode and radiates light onto the DVD  30  while moving the writing and/or reading unit toward and away from the optical disc, to focus the light, only one reflection signal  83  obtained from light reflected from the surface  31  of the DVD  30  is obtained as shown in  FIG. 3B  since no light is reflected from the data layer  33  of the DVD  30 . When the CD  50  is loaded, similarly to the DVD  30 , only a reflection signal obtained from light reflected from the surface  51  of the CD  50  is obtained in response to light radiated by the BD laser diode.  
         [0049]     According to an aspect of the present invention, a type of an optical disc loaded into a data recording and/or reproducing apparatus is determined based on a number of reflection signals being different according to the distance between a surface and a data layer of the optical disc and the working distance of a laser diode. In other words, the type of the loaded optical disc may be determined based on whether there is a reflection signal from the data layer of the optical disc.  
         [0050]      FIG. 4  is a block diagram of a data recording and/or reproducing apparatus according to an embodiment of the present invention. The data recording and/or reproducing apparatus includes a writing/reading unit  1 , a control unit  2 , and a memory unit  3 .  
         [0051]     The writing/reading unit  1  is controlled by the control unit  2  to write data to and/or read data from an optical disc  100 . The writing/reading unit  1  includes laser diodes corresponding to various types of optical discs. In an embodiment of the present invention, the writing/reading unit  1  includes a BD laser diode  12 , a DVD laser diode  14 , and a CD laser diode  16 , as shown in  FIG. 8 .  
         [0052]     The control unit  2  controls the data recording and/or reproducing apparatus. As shown in  FIG. 9 , the control unit  2  includes a radio frequency (RF) chip  22  converting light reflected from the optical disc  100  into an RF signal, a digital signal processor (DSP)  24  performing channel decoding and error correction on the RF signal, a servo  26  performing focusing and tracking, an interface  28  for interface with a host, and a system controller  29  which controls overall operation of the control unit.  
         [0053]     The memory unit  3  stores data read from the optical disc  100  and temporarily stores data to be written to the optical disc  100 .  
         [0054]     According to an embodiment of the present invention, a method of determining a type of optical disc, which is performed by the data recording and/or reproducing apparatus shown in  FIG. 4 , will be described with reference to  FIG. 5 .  
         [0055]     Referring to  FIG. 5 , when the optical disc  100  is loaded into the data recording and/or reproducing apparatus at operation S 110 , the control unit  2  selects one of a plurality of laser diodes included in the writing/reading unit  1  at operation S 130 . In an embodiment of the present invention, the writing/reading unit  1  includes a DB laser diode, a DVD laser diode, and a CD laser diode. In embodiments of the present invention, a type of an optical disc loaded into the data recording and/or reproducing apparatus is determined based on a number of reflection signals being different according to the distance between a surface and a data layer of the optical disc and the working distance of a laser diode. In other words, the type of the loaded optical disc may be determined based on whether there is a reflection signal from the data layer of the optical disc. In an embodiment of the present invention, the control unit  2  selects the BD laser diode having a shortest working distance among the three laser diodes in operation S 130 .  
         [0056]     Thereafter, in operation S 150 , the control unit  2  controls the BD laser diode to radiate light onto the optical disc  100  while controlling the writing/reading unit  1  to approach and/or withdraw from the optical disc  100 . In operation S 150 , the data recording and/or reproducing apparatus operates in a focus search mode.  
         [0057]     The control unit  2  counts reflection signals generated from light reflected from the optical disc  100  in operation S 170  and determines the type of the optical disc  100  based on the number of reflection signals in operation S 190 . If the optical disc  100  is a BD with a single data layer, two reflection signals are obtained as shown in  FIG. 3A . One is the reflection signal  81  obtained from light reflected from the surface  11  of the BD  10  and the other is the reflection signal  82  obtained from light reflected from the data layer  13  of the BD  10 . However, if the optical disc  100  is a DVD or CD with a single data layer, only a reflection signal obtained from a surface of the optical disc  100  is obtained, as shown in  FIG. 3B . If the optical disc  100  is a BD with two data layers, three reflection signals, i.e., one reflection signal obtained from light reflected from a surface of the BD and two reflection signals obtained from lights reflected from the two data layers, respectively, are obtained. In other words, in an embodiment of the present invention, when the number of reflection signals is at least 2, the optical disc  100  is determined as the BD.  
         [0058]     When the optical disc  100  is determined as not being a BD in operation S 190 , it is needed to determine whether the optical disc  100  is a DVD or a CD. Determining whether the optical disc  100  is a DVD or a CD may be performed using conventional methods or according to an aspect of the present invention.  
         [0059]     An example of a method of determining whether the optical disc  100  is a DVD or a CD according to an aspect of the present invention will now be described with respect to  FIG. 7 . The optical disc is loaded at operation S 210 . The control unit  2  selects the DVD laser diode or the CD laser diode at operation S 230 . For example, the control unit  2  selects and turns on the DVD laser diode  14  and controls the DVD laser diode  14  to radiate light onto the optical disc  100  at operation S 250  while approaching and/or withdrawing the writing/reading unit  1  toward and away from the optical disc  100 . In other words, a focus search operation is performed again. A time interval between reflections from the optical disc  100  is measured at operation S 270 . The control unit  2  determines whether the optical disc  100  is the DVD or the CD based on a time interval between a reflection signal from the surface ( 31 ,  51 ) of the optical disc  100  and a reflection signal from the data layer ( 33 ,  53 ) of the optical disc  100  at operation S 290 .  
         [0060]     Referring to  FIG. 1B , the distance between the surface  31  and the data layer  33  of the DVD  30  having the single data layer  33  is about 0.6 mm. Referring to  FIG. 1C , the distance between the surface  51  and the data layer  53  of the CD  50  is about 1.2 mm. In other words, the distance between the surface  31  and the data layer  33  of the DVD  30  is shorter than the distance between the surface  51  and the data layer  53  of the CD  50 . Accordingly, based on the time interval between the reflection signal from the surface of the optical disc  100  and the reflection signal from the data layer of the optical disc  100 , whether the optical disc  100  is the CD or the DVD may be determined.  
         [0061]      FIG. 6A  illustrates a time interval T 1  between a reflection signal  84  from the surface  31  of the DVD and a reflection signal  85  from the data layer  33  of the DVD.  FIG. 6B  illustrates a time interval T 2  between a reflection signal  86  from the surface  51  of the CD and a reflection signal  87  from the data layer  53  of the CD. Since the distance between the surface  31  and the data layer  33  of the DVD  30  is shorter than the distance between the surface  51  and the data layer  53  of the CD  50 , T 1  is less than T 2 .  
         [0062]     In the above embodiments, determining a type of the optical disc  100  as a BD, a DVD, or a CD has been described, but the present invention is not restricted thereto. The method and apparatus may be applied to distinguishing other types of discs having different thicknesses, different distances between a surface and a recording layer and operating at different working distances. In addition, the present invention is useable regardless of whether the optical disc  100  has a single data layer or multiple data layers.  
         [0063]     The invention may also be embodied as computer readable codes on a computer readable recording medium. The computer readable recording medium may be any data storage device that can store data which can be thereafter read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission through the Internet). The computer readable recording medium may also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.  
         [0064]     As described above, according to aspects of the present invention, a type of an optical disc loaded into a data recording and/or reproducing apparatus may be quickly and accurately determined, and therefore, initialization time for the use of an optical disc is reduced.  
         [0065]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
A method of determining a type of an optical disc loaded into a data recording and/or reproducing apparatus, which includes a plurality of laser diodes and records data onto and/or reproduces data from diverse types of optical discs, and the data recording and/or reproducing apparatus for implementing the method. The method includes selecting one laser diode from among the plurality of laser diodes, radiating light onto the loaded optical disc while approaching and/or withdrawing the selected laser diode to and from the loaded optical disc, counting a number of reflection signals generated from the light reflected from the loaded optical disc, and determining the type of the loaded optical disc based on the number of reflection signals.