Abstract:
The invention relates to write strategy modification, and in particular, to dynamic write strategy modification. A dynamic write strategy modification method comprises: writing a plurality of data on to an optical disk according to a writing strategy with at least three parameters; measuring at least two quality indices of the data wrote on the optical disk; storing a result comprising the parameters and the corresponding quality indices; judging whether a terminate condition is achieved; if no, changing the parameters and repeating the above steps; if yes, analyzing the stored results and outputting an optimal writing strategy with at least three optimal parameters.

Description:
BACKGROUND 
   The invention relates to write strategy modification, and in particular, to dynamic write strategy modification. 
   A write strategy for recording data on a disc comprises a plurality of parameters such as back-end pulse interval, front-end pulse ratio, back-end pulse ratio. These parameters, however, are not always optimal. Please refer to  FIG. 1A ,  FIG. 1B , and  FIG. 1C .  FIG. 1A ,  FIG. 1B , and  FIG. 1C  show various pits recorded on a disc with various write strategy parameter values. Pits recorded on a disc are respectively short, long, and shift in  FIG. 1A ,  FIG. 1B , and  FIG. 1C  with non-optimal write strategy parameters. These non-optimal write strategy parameters result in poor recording quality. 
   SUMMARY 
   An object of the invention is to provide a dynamic write strategy modification method. Firstly, writing a plurality of data on to an optical disk according to a writing strategy with at least three parameters and measuring at least two quality indices of the data wrote on the optical disk, then storing a result comprising the parameters and the corresponding quality indices. After that, judging whether a terminate condition is achieved; if no, changing the parameters and repeating the above steps; if yes, analyzing the stored results and outputting an optimal writing strategy with at least three optimal parameters. 
   A further object of the invention is to provide a dynamic write strategy modification apparatus. The dynamic write strategy modification apparatus comprises a pick-up head, an RF signal processing circuit, an adjusting control circuit, and a result processing unit. The pick-up writes a plurality of data on to an optical disk according to a writing strategy with at least three parameters. The RF signal processing circuit measures at least two quality indices of the data wrote on the optical disk. The adjusting control circuit stores a result comprising the parameters and the corresponding quality indices, judges whether a terminate condition is achieved, changes the parameters to generating a next write strategy and transmitting the next write strategy to the PUH if the terminate condition is not achieved, and sends the results if the terminate condition is achieved. The result processing unit receives the results from the adjusting control circuit, analyzes the stored results, and outputs an optimal writing strategy with at least three optimal parameters according to the analyzing. 

   
     DESCRIPTION OF THE DRAWINGS 
     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: 
       FIG. 1A ,  FIG. 1B , and  FIG. 1C  show various pits recorded on a disc with various values of non-optimal parameters; 
       FIG. 2  and  FIG. 3  are schematic diagrams of dynamic adjustment of a back-end pulse interval and pulse ratios, respectively; 
       FIG. 4  shows the relationship of jitter value with back-end pulse interval; 
       FIG. 5  shows the relationship of jitter value with front-end pulse ratio; 
       FIG. 6  shows the relationship of jitter value with back-end pulse ratio; 
       FIG. 7  is a flow chart of the dynamic write strategy modification method according to an embodiment of the invention; 
       FIG. 8  is a flow chart of the dynamic write strategy modification method according to another embodiment of the invention; 
       FIG. 9  is a block diagram of an optical disc writing system according to an embodiment of the invention. 
   

   DESCRIPTION 
   A detailed description of the invention is provided in the following. Please refer to  FIG. 2  and  FIG. 3  at the same time.  FIG. 2  and  FIG. 3  are schematic diagrams of dynamic adjustment of a back-end pulse interval T d  and front-end pulse ratio D f  (D f =T 1 /T 2 ) and back-end pulse ratio D b  (D b =T 3 /T 4 ), respectively. Initially, the back-end pulse interval T d  is adjusted first to record a pit of a precise length. For example, if the ideal pit length is 6T, the recorded pit on the disc will be exactly equal to 6T. The front-end and back-end pulse ratio D f  and D b  are then adjusted to generate precisely front-end and back-end positions of the recorded pit. In other words, the beginning and ending positions of an ideal pit are exactly equal to that of the recorded pit. Please note that the description of pit and its length is only meant to serve as an example, and is not meant to be taken as a limitation. In other words, various kinds of marks (e.g. land and its length for limiting the previous or following pit) can be applied in the invention. In the following description, it takes the pit and its length to be the example. A detailed description of adjusting these parameters is described in the following. 
   Please refer to  FIG. 2  first. There are three different back-end pulse intervals T d1 , T d2 , T d3  applied in the write strategy to record three corresponding pits Pit_ 1 , Pit_ 2 , Pit_ 3  in the disc. By reading and analyzing the radio frequency signals of pits Pit_ 1 , Pit_ 2 , and Pit_ 3 , an optimal back-end pulse interval T d  can be determined as the back-end pulse interval T d3 . Additionally, if the recorded pit length is equal to nT where n is a positive value, the adjusting range offset value T d  is between (n−2)T and nT. Similarly, optimal front-end and back-end pulse ratio D f  and D b  shown in  FIG. 3  are finally determined from recording pits with different optimal pulse ratio values, reading back corresponding RF signals of these pits, and finding one with a least jitter value. A detailed description of write strategy parameter variation under different transfer rates is described in the following. 
   Please refer to  FIG. 4 ,  FIG. 5 , and  FIG. 6  at the same time.  FIG. 4 ,  FIG. 5 , and  FIG. 6  show the relationship of jitter value J value  with back-end pulse interval T d , front-end pulse ratio D f , and back-end pulse ratio D b , respectively.  FIG. 4  shows that the back-end pulse interval T d  is reduced to minimize the jitter value J value  when the transfer rate (e.g. 16x, 20x , 24x , 32x) increases. The back-end pulse interval T d  can be shortened to obtain the minimal jitter value J value  since the diffusion effect of the recorded pit is significant when the transfer rate increases. Similarly,  FIG. 5  shows that the front-end pulse ratio D f  is reduced to minimize the jitter value J value  when the transfer rate increases. Finally,  FIG. 6  shows that the back-end pulse ratio D b  is increased to minimize the jitter value J value  when the transfer rate increases. 
   Please refer to  FIG. 7 .  FIG. 7  is a flow chart of the dynamic write strategy modification method according to an embodiment of the invention. A detailed description is given in the following.
         Step  702 : Preparing write strategy parameters. The write strategy parameters comprise a plurality of different back-end pulse intervals T d1 ˜T dn , different front-end pulse ratio D f1 ˜D fn , different back-end pulse ratio D b1 ˜D bn  in an adjustable range.   Step  704 : Setting up an initial back-end pulse interval T d     —     init , an initial front-end pulse ratio D f     —     init , and an initial back-end pulse ratio D b     —     init .   Step  706 : Generating the test data.   Step  708 : Recording the test data onto a disc by utilizing the initial back-end pulse interval T d     —     init , the initial front-end pulse ratio D f     —     init , and the initial back-end pulse ratio D b     —     init  of write strategy.   Step  710 : Measuring a pit length and jitter value of the test data.   Step  712 : Storing jitter value information, a current back-end pulse interval, a current front-end pulse ratio, and a current back-end pulse ratio.   Step  714 : Determining whether to stop recording the test data by utilizing different write strategy parameters. If yes (satisfying a terminate condition), proceed to step  718 ; otherwise proceed to step  716 .   Step  716 : Selecting another back-end pulse interval to replace the current back-end pulse interval, selecting another front-end pulse ratio to replace the current front-end pulse ratio, and selecting another back-end pulse ratio to replace the current back-end pulse ratio.   Step  718 : Finding an optimal back-end pulse interval and optimal front-end and back-end pulse ratio and utilizing these optimal write strategy parameters to dynamically modify the write strategy.   Step  720 : Recording data on a disc by utilizing the modified write strategy.       

   Please refer to  FIG. 8 .  FIG. 8  is a flow chart of the dynamic write strategy modification method according to another embodiment of the invention. A detailed description is given in the following.
         Step  802 : Preparing write strategy parameters. The write strategy parameters comprise a plurality of different back-end pulse intervals T d1 ˜T dn , different front-end pulse ratio D f1 ˜D fn , different back-end pulse ratio D b1 ˜D bn  in an adjustable range.   Step  804 : Setting up an initial back-end pulse interval T d     —     init , an initial front-end pulse ratio D f     —     initial , and an initial back-end pulse ratio D b     —     initial .   Step  806 : Generating the test data.   Step  808 : Recording the test data onto a disc by utilizing the initial back-end pulse interval T d     —     init , the initial front-end pulse ratio D f     —     initial , and the initial back-end pulse ratio D b     —     initial  of the write strategy.   Step  810 : Selecting another back-end pulse interval to replace the current back-end pulse interval, selecting another front-end pulse ratio to replace the current front-end pulse ratio, and selecting another back-end pulse ratio to replace the current back-end pulse ratio.   Step  812 : Determining whether to stop recording the test data by utilizing different write strategy parameters. If yes (satisfying a terminate condition), proceed to step  814 ; otherwise proceed to step  810 .   Step  814 : Measuring a pit length and jitter value of the test data.   Step  816 : Storing jitter value information, a current back-end pulse interval, a current front-end pulse ratio, and a current back-end pulse ratio.   Step  818 : Finding an optimal back-end pulse interval, an optimal front-end pulse ratio, and an optimal back-end pulse ratio and utilizing these optimal write strategy parameters to dynamically modify the write strategy.   Step  820 : Recording data on a disc by utilizing the modified write strategy.       

   Please note that the kind of terminate condition (in steps  714  and  812 ) is not limited in the invention. Various kinds of terminate conditions can be applied in the invention. For example, the quality of the recorded test data, the distribution of the jitter value, or the number of write strategy parameter can be taken as the terminate condition. In the case of the recorded test data quality, if the quality is good enough (the jitter value of the test data is small enough), the terminate condition is satisfied. In the case of jitter value distribution, when the jitter value becomes divergent, the terminate condition is satisfied. In the case of parameter number, if each parameter is utilized to write the test data, the terminate condition is satisfied. 
   Please refer to  FIG. 9 .  FIG. 9  is a block diagram of an optical disc writing system  900  according to an embodiment of the invention. The optical disc writing system  900  comprises a disc motor  902 , a control system  904 , an RF signal processing circuit  906 , an adjusting control circuit  908 , a result processing unit  910 , a recording signal generator  912 , a write pulse control circuit  914 , and a pick-up head (PUH)  916 . The recording signal generator  912  prepares the recording signal according to the data to be recorded on the disc and a write strategy corresponding to the data. The write pulse control circuit  914  control the PUH according to the received recording signal. The PUH  916  emits laser onto the optical disc under control of the write pulse control circuit  914 . The disc motor  902  is utilized to rotate the disc to let the PUH  916  emit laser on the whole optical disk. The rotating speed of the disc is controlled by the control system  904 . Additionally, the control system  904  also controls output laser power of the PUH  916 . 
   The PUH  916  receives the reflected light from the optical disc and generates derived signal by detecting the reflected light. The RF signal processing circuit  906  processing the derived signal and measures the writing quality indices (e.g. jitter value and pit length) according to the derived signal. The adjusting control circuit  908  receives quality indices, and stores the current write strategy parameter (e.g. back-end pulse interval T d  and/or front-end pulse ratio D f  and D b ) and the quality indices (e.g. jitter value and pit length). Then the adjusting control circuit  908  chooses another write strategy parameter to update the current write strategy parameter in the recording signal generator  912  until a terminate condition is achieved. The result processing unit  910  receives the results (the write strategy parameters (e.g. back-end pulse interval T d  and/or front-end pulse ratio D f  and D b ) and the corresponding quality indices) from the adjusting control circuit  908 , analyzes the stored results, and outputs an optimal writing strategy with optimal parameters according to the analyzing. Finally, the write pulse control circuit  914  generates write pulse according to the current write strategy parameter. 
   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.