Abstract:
A disk area type detection method and apparatus, the disk area type detection method including detecting the difference between a side push-pull (SPP)  1  signal and an SPP 2  signal; and determining whether an area is a storage medium related information area or a user data area on the disk, based on the detected difference. According to the method and apparatus, the user data area and the storage medium related information area of the disk can be easily distinguished, allowing phase locked loop (PLL) control to be performed appropriately.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority of Korean Patent Application No. 2004-69998, filed on Sep. 2, 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 disk, and more particularly, to a disk area type detection method and apparatus.  
         [0004]     2. Description of the Related Art  
         [0005]     Optical information storage media, such as optical disks, are widely used, in conjunction with an optical pickup apparatus which can record and reproduce information without physical contact.  
         [0006]     Compact disks (CDs) and digital versatile disks (DVDs) are two types of optical disks, each with different recording capacity. Optical disks can also be broken down into read-only disks and recordable disks. Examples of the former are the 650 MB CD and the 4.7 GB DVD-ROM. Examples of the latter are the 650 MB CD-recordable (R) and CD-rewritable (RW), and the 4.7 GB DVD+R/RW, DVD-RAM and DVD-R/RW. Furthermore, a high-density optical disk (HD-DVD) with a recording capacity of 23 GB or more is under development.  
         [0007]     An ordinary optical information storage medium employs a method by which data is recorded in the form of pits or a groove wobble. Here, the pits are openings formed through engraving a substrate during manufacture, and a pit signal is detected as a jitter value. The groove wobble is a groove formed on a substrate in the form of a wave, and a groove wobble signal is detected as a push-pull signal.  
         [0008]      FIG. 1  illustrates an example of an optical information storage medium according to the conventional technology.  
         [0009]     Referring to  FIG. 1 , a conventional high-density rewritable optical recording information storage medium includes a user data area  120  in which user data is recorded, a lead-in area  110  inside the user data area, and a lead-out area  130  outside the user data area. A storage medium related information area  111  occupies all or part of the lead-in area  110 , and stores data only for reproduction such as storage medium related information. This data only for reproduction is formed as a high frequency wobble. The recordable area which covers part of the lead-in area  110 , the data area  120 , and the lead-out area  130  is formed as a relatively low frequency wobble, and in this groove user data can be recorded. Thus, since the wobble format of the user data area is different from that of the storage medium related information area, PLL conditions must be changed before the stored data can be read. Accordingly, it is required to change PLL conditions by determining whether a laser beam is projected to the user data area or to the storage medium related information area.  
         [0010]     Meanwhile, a push-pull signal generation method according to the conventional technology will now be explained briefly.  
         [0011]      FIGS. 2A through 2C  illustrate a push-pull signal generation method according to the conventional technology.  
         [0012]     In a DPP method, a diffraction unit is aligned with a beam from a laser light source, and three spots by three beams of ninth order diffracted light (main beam) and first order diffracted light (side beams) are formed on an optical disk. Reflected light from each spot is received by a corresponding photo detector, and the main spot by the main beam is used for recording or reading a signal, while side spots by side beams are used for detecting tracking errors.  
         [0013]     In the DPP method, by using the main spot and two side spots, a tracking error signal is generated. Referring to  FIG. 2B , a main photo detector  23  receives light from the main spot. The photo detector  23  is divided in four parts in a vertical and horizontal direction. Referring to  FIGS. 2A and 2C , each of two side photo detectors  21  and  25  receives light from the side spots and each photo detector  21  and  25  is divided in two parts in a horizontal direction. When output signals of the photo detectors are denoted by A, B, C, D, E, F, G, and H, respectively, a tracking error signal is obtained as the following equations: 
 
 MPP= ( B+C )−( A+D ) 
 
 SPP 1= E−F  
 
 SPP 2= G−H  
 
 DPP=MPP−k ( SPP 1+ SPP 2)
 
         [0014]     Here, the main push-pull (MPP) signal is the diagonal difference of signals generated in the main photo detector, and side push-pull (SPP) 1  and SPP 2  are the differences of signals generated in the respective side photo detectors. Also, k denotes a coefficient, and DPP denotes a tracking error signal generated by the DPP method.  
         [0015]     Referring to  FIG. 2A , a first subtractor  22  performs subtraction of E and F signals generated in the first side photo detector  21 , to generate the SPP 1  signal, and a third subtractor  26  performs subtraction of G and H signals generated in the second side photo detector  25 , to generate the SPP 2  signal. Meanwhile, the second subtractor  24  uses A, B, C, and D signals generated in the main photo detector  23  to generate the MPP signal given as MPP=(B+C)−(A+D).  
       SUMMARY OF THE INVENTION  
       [0016]     According to an aspect of the present invention, there is provided a disk area type detection method and apparatus enabling simple identification of a disk area type.  
         [0017]     According to another aspect of the present invention, there is provided a disk area type detection method including detecting the difference between a side push-pull (SPP)  1  signal and an SPP 2  signal based on the signals reflected from the disk; and determining whether an area of the disk is a storage medium related information area or a user data area, based on the detected difference.  
         [0018]     According to another aspect of the present invention, the detecting of the difference may include detecting the peak-to-peak value of (SPP 1 −SPP 2 ). At this time, determining the area type may include: if the peak-to-peak value of (SPP 1 −SPP 2 ) exceeds a predetermined threshold, determining that the area is a storage medium related information area.  
         [0019]     According to another aspect of the present invention, the detecting of the difference may include detecting the phase difference between SPP 1  and SPP 2 . At this time, determining the area type may further include: if the phase difference is output as direct current (DC), determining that the area is a storage medium related information area.  
         [0020]     According to another aspect of the present invention, the method may further include outputting a phase locked loop (PLL) condition based on the determination result, to a PLL.  
         [0021]     According to another aspect of the present invention, there is provided a disk area type detection apparatus for detecting the type of an area of a disk, including a difference signal detection unit which detects the difference between an SPP 1  signal and an SPP 2  signal based on the signals reflected from the disk; and an area determination unit which determines whether an area on the disk is a storage medium related information area or a user data area, based on the detected difference.  
         [0022]     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  
       [0023]     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:  
         [0024]      FIG. 1  illustrates an example of an optical information storage medium according to the conventional technology;  
         [0025]      FIGS. 2A through 2C  illustrate a push-pull signal generation method according to the conventional technology;  
         [0026]      FIGS. 3A and 3B  illustrate the phase relationship of sub-beams to explain the concept of determining a storage medium related information area according to an embodiment of the present invention;  
         [0027]      FIG. 4  is a diagram of the structure of an optical recording and/or reproducing apparatus including an area detection unit according to an embodiment of the present invention;  
         [0028]      FIG. 5  illustrates an embodiment of an area detection unit shown in  FIG. 4 ;  
         [0029]      FIG. 6  illustrates another embodiment of an area detection unit shown in  FIG. 4 ;  
         [0030]      FIGS. 7A and 7B  show graphs comparing (SPP 1 −SPP 2 ) signals of a user data area and a storage medium related information area in an off-track state;  
         [0031]      FIGS. 8A through 8D  show graphs comparing (SPP 1 −SPP 2 ) signals in R-tilt change;  
         [0032]      FIGS. 9A through 9D  show graphs comparing (SPP 1 −SPP 2 ) signals in T-tilt change; and  
         [0033]      FIGS. 10A and 10B  show graphs of phase difference signals of a user data area and a storage medium related information area in an off-track state.  
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0034]     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.  
         [0035]     Referring to  FIG. 3A , it can be seen that SPP 1  and SPP 2  in the user data area correspond exactly, whereas in  FIG. 3B , there is a phase difference between SPP 1  and SPP 2  in the storage medium related information area.  
         [0036]     Accordingly, to an embodiment of the present invention is based on the fact that a user data area can be distinguished from a storage medium related information area by detecting the phase difference of sub-beams SPP 1  and SPP 2 .  
         [0037]      FIG. 4  is a diagram of the structure of an optical recording and/or reproducing apparatus including an area detection unit according to an embodiment of the present invention.  
         [0038]     The optical recording and/or reproducing apparatus to which the present invention is applied includes an optical disk  410 , a pickup  420 , an RF and servo error generation unit  440 , a servo control unit  450 , a focus servo driving unit  460 , a tracking servo driving unit  470 , a slide servo driving unit  480 , a slide motor  430 , and a PLL  490 .  
         [0039]     The pickup  420  includes an optical system including a laser diode, an optical detector, a variety of lenses, and a focus/tracking actuator. According to tracking and focus control of the servo control unit  450 , a light beam is condensed onto an object lens, and the pickup  420  directs the light beam onto the track of the optical disk  410 . Also, light reflected from the recording surface of the optical disk  410  is condensed again onto the object lens and directed onto the optical detector, in order to detect a focus error signal and a tracking error signal.  
         [0040]     The photo detector includes a plurality of photo detecting devices and outputs an electric signal in proportion to the amount of light obtained by each photo detecting device, to the RF and servo error generation unit  440 .  
         [0041]     The RF and servo error generation unit  440  generates an RF signal for reproducing data, a focus error (FE) signal and a tracking error (TE) signal for servo control, from the electrical signal output from each photo detecting device of the photo detector.  
         [0042]     The generated RF signal is output to a data decoder (not shown), and the focus error (FE) signal and the tracking error (TE) signal are output to the servo control unit  450 .  
         [0043]     The servo control unit  450  processes the focus error (FE) signal and outputs a driving signal for focusing control, to the focus servo driving unit  460 , and processes the tracking error (TE) signal and outputs a driving signal for tracking control, to the tracking servo driving unit  470 .  
         [0044]     The focus servo driving unit  460  moves the pickup  420  up and down to follow the disk, by driving the focus actuator in the pickup  420  such that a focus is formed on the surface of the disk  410  according to the upward and downward movement together with the rotation of the disk  410 .  
         [0045]     The tracking servo driving unit  470  moves the object lens of the pickup  420  radially by driving the tracking actuator in the pickup  420 , such that the beam follows the track.  
         [0046]     The RF and servo error generation unit  440  includes a tracking error signal generation circuit and also an area detection unit  441 , which detects whether the pickup  420  is in the user data area or in the storage medium related information area of the disk according to an embodiment of the present invention. For convenience of explanation, it is assumed that the photo detector embedded in the pickup  420  has the structure shown in  FIG. 2 , but it is obvious that a variety of types of photo detector can be applied to the present invention as well as the type shown in  FIG. 2 .  
         [0047]      FIG. 5  illustrates an embodiment of an area detection unit shown in  FIG. 4 .  
         [0048]     Referring to  FIG. 5 , an area detection unit  441  includes an SPP 1  signal generation unit  510 , an SPP 2  signal generation unit  520 , a subtraction unit  530 , and an area determination unit  540 .  
         [0049]     The SPP 1  signal generation unit  510  subtracts the F signal from the E signal, and generates and outputs the SPP 1  signal.  
         [0050]     The SPP 2  signal generation unit  520  subtracts the H signal from the G signal and generates and outputs the SPP 2  signal.  
         [0051]     The subtraction unit  530  receives the SPP 1  signal and the SPP 2  signal, subtracts the SPP 2  signal from the SPP 1  signal, and outputs the result to the area determination unit  540 .  
         [0052]     If the peak-to-peak value of the signal resulting from subtracting the SPP 2  signal from the SPP 1  signal is less than a predetermined threshold value, the area determination unit  540  determines that the pickup is in the user data area, and if the resulting value is greater than the predetermined threshold, the area determination unit  540  determines that the pickup is in the storage medium related information area. Then, the area determination unit  540  outputs PLL control condition information according to the determined area, to the PLL  490 .  
         [0053]      FIG. 6  illustrates another embodiment of an area detection unit shown in  FIG. 4 .  
         [0054]     Referring to  FIG. 6 , the area detection unit  441  includes an SPP 1  signal generation unit  610 , a binarization unit  620 , an SPP 2  signal generation unit  630 , a binarization unit  640 , a phase detection unit  650 , a low pass filter (LPF)  660 , a LPF  670 , a subtraction unit  680 , and an area determination unit  690 .  
         [0055]     The SPP 1  signal generation unit  610  subtracts the F signal from the E signal and generates and outputs the SPP 1  signal, and the binarization unit  620  binarizes the SPP 1  signal and outputs the result to the phase detection unit  650 .  
         [0056]     The SPP 2  signal generation unit  630  subtracts the H signal from the G signal and generates and outputs the SPP 2  signal, and the binarization unit  640  binarizes the SPP 2  signal and outputs the result to the phase detection unit  650 .  
         [0057]     The phase detection unit  650  receives the binarized SPP 1  and SPP 2  signals and detects the phase difference. If the phase of the SPP 1  signal is greater, the phase difference is output to the LPF  660 , and if the phase of the SPP 2  signal is greater, the phase difference is output to the LPF  670 .  
         [0058]     The LPF  660  and the LPF  670  filter any received signal from the phase detection unit  650 , and output the result to the subtraction unit  680 .  
         [0059]     The subtraction unit  680  subtracts the output signal from the LPF  670  from the output signal from the LPF  660 , and outputs the subtraction result PIC_s to the area determination unit  690 .  
         [0060]     If the received PIC_s value is close to 0, the area determination unit  690  determines that the pickup is within the user data area, and if the value is a predetermined positive or negative value, the area determination unit  690  determines that the pickup is within the storage medium related information area.  
         [0061]      FIGS. 7A and 7B  show graphs comparing (SPP 1 −SPP 2 ) signals of a user data area and a storage medium related information area in an off-track state.  
         [0062]     Referring to  FIG. 7A , since SPP 1  and SPP 2  are almost identical in the user data area, it can be seen that (SPP 1 −SPP 2 ) is between predetermined upper and lower limits. That is, it can be seen that the peak-to-peak value is close to 0.  
         [0063]     Meanwhile, referring to  FIG. 7B , since there is a phase difference between SPP 1  and SPP 2  in the storage medium related information area, (SPP 1 −SPP 2 ) appears in the form of a sine wave, and accordingly it can be seen that the peak-to-peak value exceeds a predetermined threshold value.  
         [0064]     Accordingly, if the peak-to-peak value of (SPP 1 −SPP 2 ) is less than a predetermined threshold value, it can be determined that the pickup is in the user data area, and if the peak-to-peak value is greater than the predetermined threshold value, it can be determined that the pickup is in the storage medium related information area.  
         [0065]     Thus, determining the area by using the difference between SPP 1  and SPP 2  can also be applied when the disk is tilted.  
         [0066]      FIGS. 8A through 8D  show graphs comparing (SPP 1 −SPP 2 ) signals in R-tilt change.  
         [0067]     Referring to  FIGS. 8A through 8D , since all the peak-to-peak values of (SPP 1 −SPP 2 ) exceed a predetermined threshold when R-tilt is −1.0 as shown in  FIG. 8A , 0 as shown in  FIG. 8B , and +1.0 as shown in  FIG. 8C , it can be determined that the pickup is in the storage medium related information area.  
         [0068]      FIGS. 9A through 9D  show graphs comparing (SPP 1 −SPP 2 ) signals in T-tilt change.  
         [0069]     Referring to  FIGS. 9A through 9D , since all the peak-to-peak values of (SPP 1 −SPP 2 ) exceed a predetermined threshold when T-tilt is −0.5 as shown in  FIG. 9A , 0 as shown in  FIG. 9B , and +0.5 as shown in  FIG. 9C , it can be determined that the pickup is in the storage medium related information area.  
         [0070]      FIGS. 10A and 10B  show graphs of phase difference signals of a user data area and a storage medium related information area in an off-track state.  
         [0071]      FIG. 10A  shows the PIC_s signal of the user data area, and  FIG. 10B  shows the PIC_s signal of the storage medium related information area.  
         [0072]     Referring to  FIG. 10A , in the user data area, PIC_s approaches zero.  
         [0073]     Referring to  FIG. 10B , in the storage medium related information area, PIC_s becomes vcc*0.2 or −vcc*0.2. The polarity changes according to the movement direction of the laser beam. Thus, when PIC_s approaches 0, it can be determined that the pickup is in the user data area, and when PIC_s exceeds a predetermined positive or negative value, it can be determined that the pickup is in the storage medium related information area.  
         [0074]     Meanwhile, in an on track state, by detecting (SPP 1 −SPP 2 ) and determining whether the value is DC, it can be simply determined whether or not the pickup is in the storage medium related information area.  
         [0075]     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.  
         [0076]     According to the present invention as described above, the user data area can be easily distinguished from the storage medium related information area, allowing appropriate PLL control to be performed.