Abstract:
The invention relates to recording on a medium, and in particular, to laser control during recording data on an optical medium. A laser control method for dynamically adjusting laser power during recording data onto an optical disc comprises: recording normal data onto the optical disc according to an initial laser power; stopping recording when a trigger is generated; reading back the recorded normal data and generating a first recording quality index; recording a test pattern at a test pattern starting point according to a selected laser power; reading back the test pattern and generating a second recording quality index; and determining an adaptive laser power to continually record the normal data according to the first recording quality index and the second recording quality index.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application entitled “Method and Apparatus for Laser Control During Recording,” Ser. No. 11/344,810, filed on Feb. 1, 2006, which claims the benefit of U.S. provisional application Ser. No. 60/713,206, filed Aug. 31, 2005, the entirety of which are incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    The invention relates to recording on a medium, and in particular, to laser control during data recording on an optical medium. 
         [0003]    A conventional method for laser control adjusts a laser power or a write strategy according to previously recorded data on an optical disc. This method, however, is not able to accurately adjust the required laser power or write strategy, thus recording quality suffers. 
       SUMMARY 
       [0004]    An object of the invention is to provide a laser control method for dynamically adjusting laser power during recording data onto an optical disc. The laser control method comprises: recording normal data onto the optical disc according to an initial laser power; stopping recording when a trigger is generated; reading back the recorded normal data and generating a first recording quality index; recording a test pattern at a test pattern starting point according to a selected laser power; reading back the test pattern and generating a second recording quality index, and determining an adaptive laser power to continually record the normal data according to the first recording quality index and the second recording quality index. 
         [0005]    Another object of the invention is to provide a laser control method for dynamically adjusting write pulse shape during recording data onto an optical disc. The laser control method comprises: recording normal data onto a disc according to an initial write pulse shape; stopping recording if a trigger is generated; reading back the recorded normal data and generating a first recording quality index; recording a test pattern at a test pattern starting point according to a selected write pulse shape; reading back the test pattern and generating a second recording quality index, and generating an adaptive write pulse shape continually recording the normal data according to the first recording quality index and the second recording quality index. 
         [0006]    A further object of the invention is to provide a laser control apparatus for dynamically adjusting laser output algorithm to record data during recording normal data onto the optical disc. The laser control apparatus comprises: a pick-up head, a write laser modulating circuit and a detection circuit. The pick-up head generates laser to recording the normal data onto the optical disc according to the laser output algorithm. The detection circuit detects at least one recording quality index from the data recorded onto the optical disc. The write laser modulating circuit generates an initial laser output algorithm to the PUH to record a normal data, generates a stopping signal to stop recording when receiving a trigger from the detection unit, generates a selected laser output algorithm to the PUH to record a test pattern at a test pattern starting point on the optical disc, and generates an adaptive laser output algorithm to continually record the normal data according to a first recording quality index and a second recording quality index. The first recording quality index is detected by the detection unit by reading back the recorded normal data. The second recording quality index is detected by the detection unit by reading back the test pattern. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]    The following detailed description, given by way of example and not intended to limit the invention solely to the embodiments described herein, will best be understood in conjunction with the accompanying drawings, in which: 
           [0008]      FIG. 1  is a block diagram of an optical system according to the invention; 
           [0009]      FIG. 2  is a schematic diagram of a recording data segment being recorded into the disc in  FIG. 1 ; 
           [0010]      FIG. 3  is a flow chart of the laser control method according to the first embodiment of the invention; 
           [0011]      FIG. 4  is a flow chart of the laser control method according to the second embodiment of the invention; 
           [0012]      FIG. 5  shows a waveform diagram of write strategy determined from the write laser modulating circuit, a recorder pit recorded into the disc of  FIG. 1 , a sliced signal, and a EFM data clock output from the PLL according to the data-to-clock edge deviation method; 
           [0013]      FIG. 6A  and  FIG. 6B  show waveform diagrams of DVDR multi-pulse and single-pulse write strategies respectively according to a pit/land deviation; 
           [0014]      FIG. 7  shows a waveform diagram of DVDRW multi-pulse write strategy. 
       
    
    
     DESCRIPTION 
       [0015]    A detailed description of the present invention is provided in the following. 
         [0016]    A detailed description of the invention is provided in the following. Please refer to  FIG. 1  and  FIG. 2  at the same time.  FIG. 1  is a block diagram of an optical system  100  according to an embodiment of the invention. In some embodiments, the disc  102  may be a recordable DVD disc (e.g. DVDR and DVDRW) or another type of optical medium.  FIG. 2  is a schematic diagram of a recording data segment  200  being recorded onto disc  102  of  FIG. 1 . The optical system  100  records normal data  210  onto the disc  102 , and roughly detects some writing quality index back from the recorded normal data  210  during recording. For example, the writing quality index could be the bit error rate (BER) detected from the BER measurer  112 , the jitter detected from the jitter measurer  114 , the pit/land length deviation detected from the pit/land length deviation calculator  116 , the data-to-clock edge deviation detected from the data-to-clock edge deviation calculator  118 , and the asymmetry detected from the asymmetry detector  122 . When the recording quality index deteriorates, the optical system  100  generates a trigger to stop recording of the normal data  210 . For example, the stopping point is the point P 1  in  FIG. 2 . Then, the optical system  100  reads the recorded data  210  to obtain the accurate writing quality index. After that, the optical system  100  starts recording the test pattern  220  into the disc  102  from the stop point P 1  to a predetermined end point P 2 . The test pattern  220  is recorded onto the disc  102  by another laser power or the write strategy. After recording the test pattern  220 , the optical system  100  can generate a new laser power or write strategy to record the normal data  230  into the disc  102  according to the information from both the normal data  210  and the test pattern  220  or the information only from the test pattern  220 . Further description of how to determine the new laser power or write strategy for recording the normal data  230  is provided in the following. 
         [0017]    In a first embodiment, a detailed description of generating a new laser power is provided in the following. The normal data  210  is recorded to the disc  102  according to the laser power PwoA, and the test pattern  220  is recorded to the disc  102  according to another laser power PwoB. If the asymmetry read from the normal data  210  is BetaA and the asymmetry read from the test pattern  220  is BetaB, then a new laser power PwoC for recording the normal pattern  230  can be determined as follows: 
         [0000]        PowC=PwoA +[(BetaTarget−Beta A )/(Beta B −Beta A )]*( PwoB−PwoA ) 
         [0000]    wherein the value BetaTarget is a predetermined value. Due to the linear relationship between the laser power and the asymmetry, the new laser power PwoC can be determined from the above equation. Additionally, if the length of the test pattern  220  requires shortening, a special pattern utilizing a plurality of long marks (larger than 8T) plus a plurality of short marks (smaller than 5T) can be chosen to fill the test pattern  220 . For example, if the length of test pattern  220  is specified to be two EFM frames (1 EFM frame=1488T in DVDR specification), a special pattern (11T+11T+11T+11T+4T+4T+4T+4T+4T+4T+4T+4T+4T+4T+4T+4T) is chosen to appear repeatedly in the test pattern  220  until the test pattern  220  is filled. Otherwise, if the length of the test pattern  220  is unlimited, a random pattern is acceptable. 
         [0018]    Please refer to  FIG. 3 .  FIG. 3  is a flow chart of the laser control method according to the first embodiment of the invention. The laser control method is applied to the optical system  100 . A detailed description is given in the following. 
         [0019]    Step  302 : Start. 
         [0020]    Step  304 : Start optimum power control (OPC) calibration. 
         [0021]    Step  306 : Set up an initial laser power PwoA based on the calibration results. 
         [0022]    Step  308 : If the recording has not yet started, step  308  is repeated; otherwise, proceed to step  310 . 
         [0023]    Step  310 : Record the normal data  210  onto the disc  102  by utilizing the initial laser power PwoA. 
         [0024]    Step  312 : If the recording is not finished, proceed to step  314 ; otherwise, go to step  324 . 
         [0025]    Step  314 : Determine if the optical system  100  generates a trigger: If yes, proceed to step  316 ; otherwise proceed to step  310 . 
         [0026]    Step  316 : Stop recording the normal data  210 , and read the previously recorded normal data  210 . 
         [0027]    Step  318 : Start recording test pattern  220  at test pattern starting point by another laser power PwoB. 
         [0028]    Step  320 : Stop recording test pattern  220  at test pattern stopping point, and read the test pattern  220  previously recorded. 
         [0029]    Step  322 : Generate the new laser power PwoC based on the normal data  210  and the test pattern  220  previously read. 
         [0030]    Step  324 : End. 
         [0031]    A detailed description of the second embodiment of generating a new write strategy is provided in the following. There are various kinds of write strategies; here the write pulse shape is given as an example. The normal data  210  is recorded onto the disc  102  according to the write pulse shape WpsA, and the test pattern  220  is recorded onto the disc  102  according to another write pulse shape WpsB. The optical system  100  then determines the write pulse shape WpsC according to the test pattern  220  or/and normal data  210  previously read. For example, if the optical system  100  reads the test pattern  220  and finds it is readable (e.g. asymmetry, jitter, bit error rate, Pit/Land length deviation, or data-to-clock edge deviation is acceptable), the write pulse shape WpsC can then be equal to the write pulse shape WpsB. A detailed description of write pulse shape method is provided later. 
         [0032]    Please refer to  FIG. 4 .  FIG. 4  is a flow chart of the laser control method according to the second embodiment of the invention. The laser control method is applied to the optical system  100 . The detailed description is shown as follows. 
         [0033]    Step  402 : Start. 
         [0034]    Step  404 : Set up an initial write pulse shape WpsA. 
         [0035]    Step  406 : If the recording has not yet started, step  406  is repeated; otherwise, proceed to step  408 . 
         [0036]    Step  408 : Record the normal data  210  onto the disc  102  by utilizing the initial write pulse shape WpsA. 
         [0037]    Step  410 : If the recording is not finished, proceed to step  412 ; otherwise, go to step  422 . 
         [0038]    Step  412 : Determine if the optical system  100  generates a trigger: If yes, proceed to step  414 ; otherwise go to step  408 . 
         [0039]    Step  414 : Stop recording the normal data  210 , and read the previously recorded normal data  210 . 
         [0040]    Step  416 : Record test pattern  220  at test pattern starting point by another write pulse shape WpsB. 
         [0041]    Step  418 : Stop recording test pattern  220  at test pattern stopping point, and read the test pattern  220  previously recorded. 
         [0042]    Step  420 : Generate the new write pulse shape WpsC based on the normal data  210  and the test pattern  220 . 
         [0043]    Step  422 : End. 
         [0044]    Further description of write pulse shape method is provided in the following. Please Refer to  FIG. 5 ,  FIG. 6A ,  FIG. 6B , and  FIG. 7 . For example, a data-to-clock edge deviation method ( FIG. 5 ) and a Pit/Land length deviation method ( FIG. 6A ,  FIG. 6B ,  FIG. 7 ) are described.  FIG. 5  shows a waveform diagram of write strategy determined from the write laser modulating circuit  126  of  FIG. 1 , a recorder pit recorded onto the disc  102  of  FIG. 1 , a sliced signal, and a EFM data clock output from the PLL  108  of  FIG. 1  according to the data-to-clock edge deviation method. By detecting the data-to-clock edge deviation (d 1  or d 2 ) from the data-to-clock edge deviation calculator  118  ( FIG. 1 ), the write pulse shape times T topr  and T last  can be adjusted.  FIG. 6A  and  FIG. 6B  show waveform diagrams of DVDR multi-pulse and single-pulse write strategies respectively according to a pit/land deviation from the pit/land length deviation calculator  116  ( FIG. 1 ). Similarly,  FIG. 7  shows a waveform diagram of DVDRW multi-pulse write strategy. 
         [0045]    Additionally, in some embodiments, the next coming normal data will start to be recorded at a test pattern starting point after generating the new laser power or write strategy; in some embodiments, the next coming normal data will start to be recorded at a test pattern stopping point after generating the new laser power or write strategy. In other words, the test pattern can be overwritten or not. 
         [0046]    Compared with the related art, the laser control method adjusts laser power or write strategy (write pulse shape) to record the normal pattern according to both the previous recorded normal data and the recorded test pattern or according to the recorded test pattern. 
         [0047]    While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.