Abstract:
The present invention provides a device for detecting the signal on a defect disc. The device includes a servo control unit, a data path control unit, a defect detection unit, and a logic combination unit. The servo control unit handles the related electromechanical devices. The data path control unit further includes a preamplifier receiving data from a lens and generating RF signals for data process, servo control signals for the servo control unit and various signals for defect detection; a slicer receiving and digitalizing the RF signals; a phase lock loop (PLL) synchronizing the digitalized RF signals to a system clock and counting the length of the digitalized RF signals; and a decoder decoding the length of the digitalized RF signals to a host. The defect detection unit receives the various signals for detecting different kinds of defects to set corresponding defect flag signals. The logic combination unit runs an appropriate logic operation on the defect flag signals to trigger defect protection for the servo control unit and the data path control unit.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention generally relates to the field of signal detection. More particularly, the present invention relates to a method and device that detects the signal on a defect disc.  
         [0003]     2. Description of the Prior Art  
         [0004]     Nowadays, disc-type storage media are broadly used in keeping data due to their storage capacity. Such disc-type storage media like optical discs, i.e. CD-R discs, CD-RW discs, DVD-R discs, DVD-RW discs, DVD+R discs, DVD+RW discs, or DVD-RAM discs etc., also provide better protection to the data stored on them against damage. However, these characteristics mentioned above do not mean the optical discs are faultless storage media for storing data because some defects might take place on their bare surfaces. For example, a deep scratch, a shallow scratch, and even a fingerprint. These defects could result in not only reading or writing errors but also a system disturbance while the system reads or writes data. Hence, it is an important thing to detect existing defects for protecting the system from a disturbed or instable situation.  
         [0005]     It is well known to use the difference of signal amplitude, such as an RF level (RFLVL) or a sub-beam added (SBAD) signal, to detect an existing defect. As shown in  FIG. 1A , a defect detection applying the RFLVL is illustrated. An RF signal  110  has a hollow region  112  in a time period  120 . That means the corresponding data of the hollow region  112  is damaged by a defect, so that the RF signal  110  in the time period  120  cannot be read out. Further, the depth of the hollow region  112  represents the depth of the defect. An RFLVL signal  114 , which is formed from the RF signal  110  passing a low pass filter, shows the envelope of the RF signal  110 . A detection threshold  130  is a fixed DC referred voltage level. As the RFLVL signal  114  is lower than the detection threshold  130  in the time period  120 , a defect flag signal  140  is raised from “ 0 ” to “1”. Moreover, a FE/TE signal  150  respectively generates a positive surge  152  and a negative surge  154  at the beginning and the end of the time period  120  to indicate a focusing and a tracking error signal. However, while the defect flag signal  140  is set from “0” to “1”, a servo system, such as a focusing and a tracking servo, and a data path control system, such as a preamplifier, a slicer, or a phase lock loop (PLL), can reduce the potential disturbance and instability through applying some appropriately protective methods and devices.  
         [0006]     Referring to FIG  1 B, an RF signal  110 - 1  has a hollow region  112 - 1  in a time period  120 - 1 . That also means the corresponding data of the hollow region  112 - 1  is damaged by a defect, so that the RF signal  110 - 1  in the time period  120 - 1  cannot be totally read out. But, the depth of the hollow region  112 - 1  is not deep as the hollow region  112  shown in  FIG. 1A , since it might just result from a shallow defect, such as a shallow scratch. An RFLVL signal  114 - 1  shows the envelope of the RF signal  110 - 1 . A detection threshold  130 - 1  is a fixed DC referred voltage level like the detection threshold  130  shown in  FIG. 1A . Obviously, the RFLVL signal  114 - 1  is always higher than the detection threshold  130 - 1  because the shallow defect does not make the hollow region  112 - 1  deep enough. Hence, not only a defect flag signal  140 - 1  has no response to the shallow defect, but also a FE/TE signal  150 - 1  has no apparently change except a little noise. Furthermore, since the shallow defect is not detected, some protective methods and devices are not triggered to protect the system from the potential disturbance and instability. In other words, the servo systems and the data path control systems are easily affected by the disturbance and instability in this defect situation.  
         [0007]     Similarly, referring to FIG  1 C, an RF signal  110 - 2  has a hollow region  112 - 2  in a time period  120 - 2 . That means the corresponding data of the hollow region  112 - 2  is slightly affected by a defect, so that the RF signal  110 - 2  in the time period  120 - 2  has weaker amplitudes. Also, the depth of the hollow region  112 - 2  is not deep like the hollow region  112 - 1  shown in  FIG. 1B , since it might only result from a shallow defect, such as a fingerprint. An RFLVL signal  114 - 2  shows the envelope of the RF signal  110 - 2  and a detection threshold  130 - 2  is a fixed DC referred voltage level like the detection threshold  130  shown in  FIG. 1A . The RFLVL signal  114 - 2  is always higher than the detection threshold  130 - 2  in this defect situation, because the shallow defect does not make the hollow region  112 - 2  deep enough. Thus, not only a defect flag signal  140 - 2  has no response to the shallow defect, but also a FE/TE signal  150 - 2  has no apparently change except a little noise. This situation is similar to the situation described in  FIG. 1B ; the servo systems and the data path control systems cannot be safely protected. On the other hand, however, the defects shown in  FIG. 1B  and  FIG. 1C  further include different statuses according to their damaged depth, width and direction; some defects might still have original data, but others have only destroyed data. Therefore, it is difficult to determine the defect flag signal simply by the detection threshold comparison.  
         [0008]     In view of the drawbacks mentioned with the prior art of defect signal detection, there is a continued need to develop a new and improved method and device that overcomes the disadvantages associated with the prior art of defect signal detection. The advantages of this invention are that it solves the problems mentioned above.  
       SUMMARY OF THE INVENTION  
       [0009]     In accordance with the present invention, a method and device for detecting the signal on a defect disc substantially obviates one or more of the problems resulted from the limitations and disadvantages of the prior art mentioned in the background.  
         [0010]     Accordingly, one object of the present invention is to provide a method and device for distinguishing defects from different depths to improve the threshold comparison.  
         [0011]     Another object is to provide a method and device for detecting defects according to various detective criteria, so that the defect detection can be more precisely.  
         [0012]     Still another object is to provide a method and device for detecting the signal on a defect disc in order to apply an appropriate method and device to protect the system from disturbance and instability.  
         [0013]     According to the aforementioned objects, the present invention provides a device for detecting the signal on a defect disc. The device includes a servo control unit, a data path control unit, a defect detection unit, and a logic combination unit. The servo control unit handles the spin rate of a spindle motor, the move of a sled motor, and the slightly tracking and focusing move of a lens. The data path control unit further includes a preamplifier receiving data from the lens and generating RF signals for data process, servo control signals for the servo control unit and various signals for defect detection; a slicer receiving and digitalizing the RF signals; a phase lock loop (PLL) synchronizing the digitalized RF signals to a system clock and counting the length of the digitalized RF signals; and a decoder decoding the length of the digitalized RF signals to a host. The defect detection unit receives the various signals for detecting different kinds of defects to set corresponding defect flag signals. The logic combination unit runs an appropriate logic operation on the defect flag signals in order to trigger defect protection for the servo control unit and the data path control unit.  
         [0014]     The present invention further discloses a method for detecting the signal on a defect disc. The method includes detecting a deep defect; detecting a shallow defect and a fingerprint; detecting an abnormal data length; detecting data interruption; detecting a defect through applying a variable threshold; and running an appropriate logic operation on the defect flag signals to identify a defect. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0016]      FIG. 1A  illustrates signals of a deep defect detected by applying well-known RFLVL detection;  
         [0017]      FIG. 1B  illustrates signals of a shallow defect detected by applying well-known RFLVL detection;  
         [0018]      FIG. 1C  illustrates signals of a fingerprint detected by applying well-known RFLVL detection;  
         [0019]      FIG. 2  illustrates a schematic defect detection device block diagram in accordance with the present invention;  
         [0020]     FIGS.  3 A˜ 3 F illustrate flow charts of the defect detection in according with the present invention; and  
         [0021]      FIG. 4  illustrates different defect signals detected by applying the defect detection in accordance with the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]     Some embodiments of the invention will now be described in greater detail. Nevertheless, it should be noted that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited except as specified in the accompanying claims.  
         [0023]     Moreover, some irrelevant details are not drawn in order to make the illustrations concise and to provide a clear description for easily understanding the present invention.  
         [0024]     As shown in  FIG. 2 , a schematic embodiment block diagram for detecting the signal on a defect disc is illustrated. A servo control unit  210  handles related electromechanical devices, such as the spin rate of a spindle motor  204 , the move of a sled motor  206 , and the slightly tracking and focusing move of a lens  208 , through a power driver  212 . That is, the servo control unit  210  can make the lens  208  not only aim at the right track of a disc  202  but also have a well focus for data reading and transferring. Through roughly moving a pick-up head  209  and slightly tracking move of the lens  208  at the horizontal direction, and slightly focusing move of the lens  208  at the vertical direction, the servo control unit  210  can make the lens  208  focus well on the right track of the disc  202 . A data path control unit  280  includes a preamplifier  220 , a slicer  230 , a phase lock loop (PLL)  240 , and a decoder  250 . The preamplifier  220  receives data signals from the lens  208  and generates various signals, such as RF signals for data process, servo control signals, i.e. a FE/TE signal, for the servo control unit  210 , and other signals, i.e. eight to fourteen modulation (EFM) signals and RF level (RFLVL) signals, etc., for defect detection. The slicer  230  digitalizes the RF signals transferred from the preamplifier  220 . The PLL  240  synchronizes the digitalized RF signals to a system clock and counts the length of the digitalized RF signals according to the system clock. The decoder  250  decodes the length of the digitalized RF signal to a host (not shown). A defect detection unit  260  receives the various signals from the preamplifier  220  and EMF signals from the slicer  230  and the PLL  240  for detecting different kinds of defects through different defect detection in order to set corresponding defect flag signals. Wherein, the different defect detection includes ADefect detection, ADefectl detection, EFMDefect detection, RPDefect detection, Interruption detection, and DSPDefect detection. A logic combination unit  270  executes an appropriate logic operation, simply, such as an OR operation or an AND operation, on the defect flag signals to precisely improve the defect detection. As the operation result indicates in a defect situation, the logic combination unit  270  triggers defect protection methods and devices to protect the corresponding units, such as the servo control unit  210 , the preamplifier  220 , the slicer  230 , the PLL  240 , and the decoder  250 .  
         [0025]     As shown in FIGS.  3 A˜ 3 F, flow charts of raising defect flag signals in different defect detection methods are illustrated. Referring to  FIG. 3A , ADefect detection is illustrated. In step  311 , comparing an RFLVL signal with an ADefect level. Wherein the RFLVL signal is the envelope of an RF signal and the ADefect level is a fixed DC referred voltage level. An ADefect flag is set to “1” in step  315  while the RFLVL signal is lower than the ADefect level. Also, the ADefect flag is set to “1” in step  314  while the RFLVL signal is higher than the ADefect level but is in defect delay time in step  312 . However, while the RFLVL signal is higher than the ADefect level and is not in the defect delay time, the ADefect flag is set to “0” in step  313 . The ADefect detection is appropriately used for detecting a deep defect, such as a scratch.  
         [0026]     Referring to  FIG. 3B , ADefectl detection is illustrated. All steps in  FIG. 3B  are similar to those in  FIG. 3A . An ADefect 1  flag is respectively set to “1” in steps  325  and  324  while the RFLVL signal is lower than the ADefect 1  level after comparing step  321  and is higher than the ADefect 1  level but in defect delay time in step  312 . Also, while the RFLVL signal is higher than the ADefect 1  level and is not in the defect delay time, the ADefect 1  flag is set to “0” in step  323 . The main difference between the ADefect level and the ADefect 1  level is that the ADefect 1  level is higher than the ADefect level so that the ADefect 1  detection can be more sensitive for a shallow defect and a fingerprint than the ADefect detection does.  
         [0027]     Referring to  FIG. 3C , EFMDefect detection is illustrated. In step  331 , while a data sector or a data frame has more than n 1  RF patterns are shorter than a first predetermined data length, the EFMDefect flag is set to “1”. For example, the first predetermined data length is  3 T for both CD and DVD data. In step  332 , while the data sector or the data frame has more than n 2  RF patterns are longer than a second predetermined data length, the EFMDefect flag is set to “1”. For example, the second predetermined data length is respectively  11 T and  14 T for CD and DVD data. In step  333 , while the data sector or the data frame has more than n 3  RF patterns are longer than a serious data length, such as  18 T, the EFMDefect flag is set to “1”. On the other hand, while a data sector or a data frame has more than n 4  RF patterns are between the first and the second predetermined data length, the EFMDefect flag is set to “0”. The EFMDefect detection is appropriately used for detecting an abnormal data length and it is real-time defect detection. Wherein, the EFMDefect detection is more sensitive while the variables n 1 , n 2 , n 3 , and n 4  have small values.  
         [0028]     Referring to  FIG. 3D , Interruption detection is illustrated. All steps in  FIG. 3D  are similar to those in  FIG. 3A . An Interruption flag is respectively set to “1” in steps  345  and  344  while the RFLVL signal is higher than the Interruption level after comparing step  341  and is lower than the Interruption level but in defect delay time in step  342 . Also, while the RFLVL signal is lower than the Interruption level and is not in the defect delay time, the Interruption flag is set to “0” in step  343 . The Interruption level setting is higher than the RFLVL signal in order to detect a defect resulted from strong reflection.  
         [0029]     Referring to  FIG. 3E , RPDefect detection is illustrated. All steps in  FIG. 3E  are similar to those in  FIG. 3A . An RPDefect flag is respectively set to “1” in steps  355  and  354  while the RFRP signal is lower than the RPDefect level after comparing step  351  and is higher than the RPDefect level but in defect delay time in step  352 . Wherein, the RFRP signal could be the peak or the bottom envelope of an RF signal and also could be the peak to the bottom of the RF signal. Moreover, while the RFRP signal is higher than the RPDefect level and is not in the defect delay time, the RPDefect flag is set to “0” in step  353 . The RPDefect detection detects a defect via further processing the RF signal thus it is more sensitive for detecting defects. Due to its sensitive ability to detect defects, the RPDefect detection is suitably used to detect a small scratch and an interruption defect.  
         [0030]     Referring to  FIG. 3F , DSPDefect detection is illustrated. All steps in  FIG. 3F  are similar to those in  FIG. 3A . A DSPDefect flag is correspondingly set to “1“ in steps  365  and  364  while an absolute difference value between an RFLVL and an RFLVL_LPF is bigger than a predetermined threshold after comparing step  361  and is smaller than the predetermined threshold but in defect delay time in step  362 . Wherein, the RFLVL_LPF signal is a slowly falling signal of the RFLVL signal passed a low pass filter. Moreover, while the absolute difference value is smaller than the predetermined threshold and is not in the defect delay time, the DSPDefect flag is set to “0” in step  363 . The DSPDefect detection detects a defect through a variable threshold thus a fixed DC referred voltage level is unnecessary.  
         [0031]     As shown in  FIG. 4 , some defect signals detected by applying the defect detection in accordance with the present invention are illustrated. An RF signal  41  has a deep hollow thus its envelope signal  411  also has the deep hollow. According to the ADefect 1  and the ADefect detection mentioned before, an ADefectl flag signal  416  and an ADefect flag signal  415  are respectively set from “0” to “1” while the envelope signal  411  is lower than an ADefect 1  level  402  and an ADefect level  401 . The EFMDefect flag signal  417  is set from “0” to “1” as well because the hollow is wide enough and generates abnormal data length. The Interruption flag signal  419  has no response to the hollow since the envelope signal  411  is always smaller than an Interruption level  404 . An RFRP signal  412  and an RFRP signal  413  respectively show the peak envelope and the inversed bottom envelope of the RF signal  41 . Further, an RFRP signal  414  is formed through the RFRP signal  412  subtracting the RFRP signal  413 . An RPDefect flag signal  418  is set from “0” to “1” as the RFRP signal  414  is lower than an RPDefect level  405 . The deep hollow caused by a deep defect, such as a scratch, can be detected out through the ADefect, the ADefect 1 , the EFMDefect, and the RPDefect detection, since its depth and width are deep and wide enough for the defect detection.  
         [0032]     An RF signal  42  has a shallow and narrow hollow thus its envelope signal  421  also has the same form. According to the ADefect 1  detection, an ADefect 1  flag signal  426  is set from “0” to “1” while the envelope signal  421  is lower than the ADefectl level  402 . An RFRP signal  422  and an RFRP signal  423  respectively show the peak envelope and the inversed bottom envelope of the RF signal  42 . Further, an RFRP signal  424  is formed through an RFRP signal  422  subtracting an RFRP signal  423 . An RPDefect flag signal  428  is set from “0” to “1” as the RFRP signal  424  is lower than the RPDefect level  405 . However, an ADefect flag signal  425 , an EFMDefect flag signal  427 , and an Interruption flag signal  429  have no response to the shallow and narrow hollow, since the envelope signal  421  is always higher than the ADefect level  401 , unsatisfying the conditions of the EFMDefect detection mentioned before, and is always lower than the Interruption level  404 , respectively. The shallow and narrow hollow probably caused by a shallow scratch can be only detected out through the ADefect 1  and the RPDefect detection, since its depth and width are insufficient for other defect detection.  
         [0033]     An RF signal  43  has a shallow and wide hollow thus its envelope signal  431  also has the same form. An ADefect 1  flag signal  436  is set from “0” to “1” while the envelope signal  431  is lower than the ADefect 1  level  402 . An EFMDefect flag signal  437  is set from “0” to “1” as well, because the hollow is wide enough and generates abnormal data length. An RFRP signal  432  and an RFRP signal  433  respectively show the peak envelope and the inversed bottom envelope of the RF signal  43 . Further, an RFRP signal  434  is formed through the RFRP signal  432  subtracting the RFRP signal  433 . An RPDefect flag signal  438  is set from “0” to “1” as the RFRP signal  434  is lower than the RPDefect level  405 . However, an ADefect flag signal  435  and an EFMDefect flag signal  437  have no response to the shallow and width hollow, since the envelope signal  431  is always higher than the ADefect level  401  and is always lower than the Interruption level  404 . The shallow and wide hollow possibly caused by a shallow defect can be only detected out through the ADefect 1 , the EFMDefect and the RPDefect detection, since its depth and width are insufficient for other defect detection.  
         [0034]     An RF signal  44  has a shallow and wide hollow thus its envelope signal  441  also has the same form. An ADefect 1  flag signal  446  is set from “0” to “1” while the envelope signal  441  is lower than the ADefect 1  level  402 . An RFRP signal  442  and an RFRP signal  443  respectively show the peak envelope and the inversed bottom envelope of the RF signal  44 . Further, an RFRP signal  444  is formed through the RFRP signal  442  subtracting the RFRP signal  443 . An RPDefect flag signal  448  has no response to the shallow and width hollow, since the RFRP signal  444  is always higher than the RPDefect level  405 . Moreover, an ADefect flag signal  445 , an EFMDefect flag signal  447 , and an Interruption flag signal  449  neither have no response to the shallow and wide hollow, since the envelope signal  441  is always higher than the ADefect level  401 , unsatisfying the conditions of the EFMDefect detection mentioned before, and is always lower than the Interruption level  404 , respectively. The shallow and wide hollow probably resulted from a fingerprint can be just detected out via the ADefect 1  detection in this situation, since its depth and width are very deficient for other defect detection.  
         [0035]     As for an RF signal  45  and an RF signal  46 , both of them are caused from strong signal strengths, such as strong optical reflection, also called an interruption defect. The RF signal  45  has strong amplitudes at its peak and its bottom envelope thus its peak envelope signal  451  has the corresponding form. An EFMDefect flag signal  457  is set from “0” to “1” since the interruption defect is wide enough and generates abnormal data length. An Interruption flag signal  459  is also set from “0” to “1” as the envelope signal  451  is higher than the Interruption level  404 . As for other flag signals, an ADefect 1  flag signal  456  and an ADefect flag signal  455  have no response to the envelope signal  451  because the envelope signal  451  is always higher than the ADefectl level  402  and the ADefect level  401 . An RFRP signal  452  and an RFRP signal  453  respectively show the peak envelope and the inversed bottom envelope of the RF signal  45 . Further, an RFRP signal  454  is formed through the RFRP signal  452  subtracting the RFRP signal  453 . An RPDefect flag signal  458  has no response to this kind of interruption defect, since the RFRP signal  454  is higher than the RPDefect level  405  at all times. This kind of interruption defect can be just detected out via the EFMDefect and the Interruption detection mentioned before.  
         [0036]     The RF signal  46  forms an inversed hollow from its bottom envelope thus its peak envelope signal  461  has the corresponding form. An EFMDefect flag signal  467  is set from “0” to “1” since the interruption defect is wide enough and generates abnormal data length. An RFRP signal  462  and an RFRP signal  463  respectively show the peak envelope and the inversed bottom envelope of the RF signal  46 . Further, an RFRP signal  464  has a deep hollow formed by the RFRP signal  462  subtracting the RFRP signal  463 . An RPDefect flag signal  468  is set from “0” to “1” while the RFRP signal  464  is lower than the RPDefect level  405 . An Interruption flag signal  469  is set from “0” to “1” while the envelope signal  461  is higher than the Interruption level  404 . However, an ADefect 1  flag signal  466  and an ADefect flag signal  465  have no response to the signal  461  because the envelope signal  461  is higher than the ADefect 1  level  402  and the ADefect level  401 . This kind of interruption defect can be only detected out via the EFMDefect, the RPDefect, and the Interruption detection mentioned before.  
         [0037]     Generally speaking, the ADefect 1  detection is more suitable than the ADefect detection for small and shallow scratch detection. The RPDefect detection is more sensitive for small scratch detection. Hence, it should be understood that the defect detection mentioned in the present invention could be combined in variety for particular defect detection. For example, combining the ADefect 1  and the EFMDefect detection via a logic “OR” operation for small scratch detection, or combining the ADefect 1  and the EFMDefect detection via a logic “AND” operation for small scratch detection except unwanted fingerprint, etc.  
         [0038]     Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.