Abstract:
A method for optimizing write strategy parameters by adopting different adjustment procedures according to quality indices is provided. A quality index representing a reproduction result corresponding to a write strategy is acquired. One adjustment procedure is determined from multiple adjustment procedures according to the acquired quality index. The determined adjustment procedure is performed to optimize the write strategy. The write strategy comprises multiple write strategy parameters. Each adjustment procedure comprises at least one of the write strategy parameters to be adjusted and the sequence of the adjusted write strategy parameters.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims the benefit of U.S. patent application entitled “A METHOD AND APPARATUS FOR OPTIMIZING WRITING PARAMETERS”, Ser. No. 60/712,931, filed Aug. 31, 2005. 
     
    
     BACKGROUND  
       [0002]     The invention relates to optical storage medium recording, and more particularly, to systems and methods for optimizing write strategy parameters by adopting different adjustment procedures according to quality indices.  
         [0003]     As requirements for digital storage and multimedia applications are increasing, optical storage devices such as digital video disk (DVD) recorders become standard devices been installed in personal computers. Manufactures produce various types of optical disks for each optical storage format. In order to obtain optimized writing characteristics and widely support various disks, optical storage device manufactures typically prepare optimized write strategies for various types of optical disks and store these write strategies with relevant disc identification codes in memory devices of optical storage devices, thus, consumers can accordingly obtain good quality in recording.  
         [0004]     New types of optical disks, however, are continually produced. Excessive memory space and expensive cost are required to support all types of optical disks, and alternately, deficient support of all types of optical disks will limit the practicality of the optical storage devices. Consumers may connect to Internet and download the newest firmware programs for optical storage devices from manufacture Websites, but that results in decreasing convenience. In addition, some optical storage devices such as DVD recorders can not connect to Internet to obtain the newest firmware programs. Certain solutions disclosed in published patents may first perform several trial recordings respectively using several pre-established write strategies and subsequently determine a better write strategy or a combination of write strategies therefrom according to several write quality indices. However, the recording quality is restricted by the pre-established write strategies.  
         [0005]     Different optical disk manufacturers may produce various types of optical disks containing the same disc identification code, thus, optical storage devices will accordingly record data using the same write strategy on various types of optical disks, resulting in recording characteristic biases. It maybe a reason that a manufacturer writes the same disc identification code in optical disks manufactured in different time periods, though manufacturing processes are changed in different time periods to produce them. Thus, it is unreliable to select proper write strategies according to disc identification codes. In order to overcome the described problem, optical storage devices may further compare pre-recorded information such as write strategy, write power and others to ensure the accuracy of the write strategy after recognizing the disc identification code. The drawbacks are that excessive storage capacity to store corresponding information is consumed and limited types of optical discs could support.  
         [0006]     Furthermore, optical storage devices may perform the conventional optimal power calibration (OPC) procedure by using a pre-established write strategy to obtain an optimized write laser power. That always has manufacturing difference between the optical disks or the optical disk recorders, so the acquired optimal write strategy for recording the patterns may be diverged from the best setting, and recorded patterns may be degrade because the write quality is not reliable.  
       SUMMARY  
       [0007]     Methods for optimizing write strategy parameters by adopting different adjustment procedures according to quality indices are provided. An embodiment of a method comprises the following steps: acquiring a quality index representing a reproduction result which is a write strategy; determining one adjustment procedure from a plurality of adjustment procedures according to the acquired quality index; and performing the determined adjustment procedure to optimize the write strategy.  
         [0008]     Systems for optimizing write strategy parameters by adopting different adjustment procedures are provided. An embodiment of a system comprises a signal read unit; a write parameter adjustment unit for acquiring at least one reproduced quality index corresponding to a write strategy from the signal read unit, determining one adjustment procedure according to the reproduced quality index to optimize the write strategy; and a pattern write unit for outputting the write strategy from the write parameter adjustment unit.  
         [0009]     The write strategy comprises a plurality of write strategy parameters. Each adjustment procedure comprises at least one of the write strategy parameters to be adjusted and the sequence of the adjusted write strategy parameters. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The invention will become more fully understood by referring to the following detailed description of embodiments with reference to the accompanying drawings, wherein:  
         [0011]      FIG. 1   a  is a diagram of an exemplary “castle-type” laser output;  
         [0012]      FIG. 1   b  is a diagram of an exemplary “multi-pulse” laser output;  
         [0013]      FIG. 2  is a diagram of a hardware environment applicable to an embodiment of a system for optimizing write strategy parameters;  
         [0014]      FIG. 3  is a flowchart illustrating an embodiment of a method for optimizing write strategy parameters by adopting different adjustment procedures according to quality indices;  
         [0015]      FIG. 4  is a flowchart illustrating an embodiment of a method for preparing initial write strategy parameters;  
         [0016]      FIG. 5  is a flowchart illustrating a first embodiment of a method for adjusting dynamic write strategy parameters;  
         [0017]      FIG. 6  is a flowchart illustrating a second embodiment of a method for adjusting dynamic write strategy parameters;  
         [0018]      FIG. 7  is a flowchart illustrating an embodiment of a method of full adjustment for all write strategy parameters;  
         [0019]      FIG. 8  is a flowchart illustrating an embodiment for obtaining an optimized value using one-dimensional search. 
     
    
     DESCRIPTION  
       [0020]     The present invention could be adopted for optimizing two kinds of write strategies.  FIGS. 1   a  and  1   b  are diagrams of exemplary write strategies for recording pits, respectively an exemplary “castle type” write strategy and an exemplary “multipulse type” write strategy. Referring to  FIG. 1   a , P w  represents laser power level, OD (over drive) represents overdrive power percentage for short patterns, S k  and E k  respectively represent OD power width of the front end of the short patterns and OD power width of the hack end of the short patterns. Short patterns may contain 3T to 5T patterns. In the other embodiment, P w , OD, S k , and E k  can also use in recording long pattern for 5T to 11T, 14T. In this embodiment, write strategy parameters P w , OD, S k  and E k  are referred as static write strategy parameters. The static write strategy parameters associates with whether patterns are formed and their formation quality. Besides, R ik  and F km  are referred as dynamic write strategy parameters , where ik and km represent combinations of previous(i) and following(m) T-length patterns respectively, the T-lengths are as 3T to 6T or greater. R ik  means the rising timing of the write pulse of the current kT pattern regarding to the previous iT pattern. F km  means the falling timing of the write pulse of the current kT pattern regarding to the following mT pattern. It means that the dynamic write strategy parameters are affected by combinations of previous and following T-length patterns. By adjusting R ik  and F km , the heat interference between the adjacent patterns is overcome to form more precise patterns. Referring to  FIG. 1   b , in multipulse write strategy, P w  represents laser power level, S k  and E k  respectively represent widths of a start pulse and an end pulse, m represents a ratio of width of one middle pulse to base clock T. P w , m, S k  and E k  are referred as static write strategy parameters and R ik  and F km  are referred as dynamic write strategy parameters.  
         [0021]      FIG. 2  is a diagram of a hardware environment applicable to an embodiment of a system for optimizing write strategy parameters. An embodiment of an optical disk recorder  100  comprises an optical pick-up (OPU)  10 , a signal read unit  20 , a write parameter adjustment unit  30  and a pattern write unit  40 . The signal read unit  20  comprises a waveform equalizer  22  and a slicer  24 , being part of a read channel of the optical storage apparatus  100 . In the another embodiment, the slicer can be replaced by an edge detector. The OPU  10  reads data patterns from an optical disk  11  and generates radio frequency (RF) signals  12 . The waveform equalizer  22  rebuilds RF signals  12  to equalized signals  23 . The equalized signals  23  are divided into sliced signals  25  by the slicer  24  (or the edge detector). The equalized signals  23  and the sliced signals  25  are input signals of the write parameter adjustment unit  30 .  
         [0022]     Write parameter adjustment unit  30  comprises two devices: a write quality detection unit  31  and a write parameter adjustment controller  32 . The write quality detection unit  31  comprises an asymmetry detector  33 , an error rate detector  34 , a jitter detector  35 , a length deviation detector  36  and an edge deviation detector  37 . The equalized signals  23  are input to the asymmetry detector  33 . The sliced signals  25  are input to the error rate detector  34 , the jitter detector  35 , the length deviation detector  36  and the edge deviation detector  37 . After calculating the input signals, the asymmetry detector  33  outputs an asymmetry of RF signal  33   s  (also called β value), the error rate detector  34  outputs a data error rates  34   s , the jitter detector  35  outputs a jitter magnitudes  35   s , the length deviation detector  36  outputs a mean length deviations for all pattern combinations  36   s , and the edge deviation detector  37  outputs a mean edge shift deviation for all pattern combinations  37   s.    
         [0023]     RF signal asymmetry  33   s , data error rates  34   s , jitter magnitudes  35   s , mean length deviations for all pattern combinations  36   s , and mean edge shift deviations for all pattern combinations  37   s  are selectively input to the write parameter adjustment controller  32  according to operations during write parameter adjustment processes. For example, when determining whether write quality is acceptable, the data rates  34   s  and jitter magnitudes  35   s  are input to the write parameter adjustment controller  32  as input signals. When adjusting dynamic write strategy parameters, mean length deviations for all pattern combinations  36   s , and mean edge shift deviations for all pattern combinations  37   s  are input to the write parameter adjustment controller  32  as input signals. Note that although the present invention adopts one or more combinations of the above input signals, it is unnecessary to reference all input signals during write parameters optimization. Furthermore, those skilled may adopt different but similar input signals representing write quality to perform write parameter adjustment. Output signals of the write parameter adjustment controller  32  act as write pulse control signals  41  controlling shape of the write pulse and the write strategy parameters  38 . The write strategy parameters  38  are further stored in a write parameters storage unit  50 .  
         [0024]     The write parameter adjustment controller  32 , in normal write strategy parameter adjustment, sets certain candidate write strategy parameters and acquires the best settings of write strategy parameters by a series of previous test writes. The write parameter adjustment controller  32 , in dynamic write strategy parameter adjustment, calculates corrections for dynamic write strategy parameters according to physically measured mean length deviations and mean edge shift deviations for all pattern combinations and adjusts dynamic write strategy parameters according to the calculated corrections. Thereafter, the write parameter adjustment controller  32  issues control signals  41  to a write pulse generator  42 . Details of write parameter adjustment process will be further described in the following flowcharts.  
         [0025]     The pattern write unit  40  comprises the write pulse generator  42  and a laser diode (LD) driver  45 , being part of a write channel of the optical storage apparatus  100 . The control signals  41  and modulated signals  43  are input in the write pulse generator  42 , where the modulated signals  43  may be signals modulated from original encoded data, or particular pattern signals. The write pulse generator  42  generates relevant write pulses  44  according to the control signals  41  and the modulated signals  43 , and subsequently the LD driver  45  generates corresponding driving signals  46  to direct the OPU  10  to perform pattern writes.  
         [0026]     The write parameters storage unit  50  records write parameters whose write quality satisfying predetermined specification after learning. The write parameter storage unit  50  may be an EEPROM, a FLASH-ROM or similar.  
         [0027]      FIG. 3  is a flowchart illustrating an embodiment of a method for optimizing write strategy parameters by adopting different adjustment procedures according to quality indices, performed by the write parameter adjustment controller  32  (as shown in  FIG. 2 ). Note that, when a castle type write strategy is used, the static write strategy parameters include P w , OD, S k  and E k , and when a multi-pulse write strategy is used, the static write strategy parameters include P w , m, S k  and E k . In step S 1100 , initial write strategy parameters W(X j , P 0 ) are prepared, where write strategy parameters X j  includes OD/m, S k , E k , R ik  and F km . Details of step S 1100  will be further described in  FIG. 4 .  FIG. 4  is a flowchart illustrating an embodiment of a method for preparing initial write strategy parameters performed in step S 1100  ( FIG. 3 ). In step S 1110 , a disk type and a manufacturer identity (ID) of the loaded disk  11  ( FIG. 2 ) are checked. Information regarding a disk type such as CD, DVD-R, DVD+R, DVD-RW, SACD, and a manufacturer ID are acquired on the optical disk  11 . In step S 1120 , it determines whether the loaded optical disk  11  is supported, namely, determines whether the optical disk recorder  100  has a built-in write strategy corresponding to the optical disk  11 . If the current medium is supported with a built-in write strategy, the process proceeds to step S 1130 , otherwise, to step S 1131 . In step S 1130 , the built-in write strategy parameters W m (X j ) associated with the acquired disk type and manufacturer ID are acquired, m means the built-in manufacturer ID and X j  means one of the write strategy parameters as shown in  FIGS. 1   a  and  1   b . In step S 1131 , default generic write strategy parameters W d (X j ) are acquired as initial write strategy parameters. In step S 1140 , a well-known optimal power calibration (OPC) for the acquired write strategy parameters is performed to acquire an initial write power P 0  and further acquire a candidate set (i.e. initial set) of write strategy parameters W(X j , P 0 ).  
         [0028]     Referring back to  FIG. 3 , step S 1200  is a write quality test step performing test writes in inner or outer test area of the loaded optical disk  11 . In step S 1300 , radio frequency (RF) signals of the previous test writes are reproduced, and write quality indices for the previous test writes are accordingly measured. The write quality indices may be outputs of one or more write quality detection units, such as RF signal asymmetry  33   s , data error rates  34   s , jitter magnitudes  35   s , mean length deviations for all pattern combinations  36   s , and mean edge shift deviations for all pattern combinations  37   s.    
         [0029]     In step S 1400 , it determines whether the measured write quality indices are larger than hard limits (i.e. dissatisfies hard limits). If so, the process proceeds to step S 1500 , otherwise, to step S 1900 . The measured write quality indices (generated by step S 1300 ) satisfying hard limits means that current write strategy parameters thereto are proper for the optical disk recorder  100  and the loaded optical disk  11  and require no further adjustment, thus, the process directly proceeds to step S 1900  to start subsequent real data recording. The measured write quality indices (generated by step S 1300 ) dissatisfying hard limits means that current write strategy parameters thereto are not completely proper and require a further verification by step S 1500  to determine whether the measured write quality indices satisfy soft limits.  
         [0030]     In step S 1500 , it determines whether the measured write quality indices are larger than soft limits (i.e. dissatisfies soft limits). If so, the process proceeds to step S 1700 , otherwise, to step S 1600 . The measured write quality indices (generated by step S 1300 ) satisfying soft limits means that these improper write qualities may be caused by the differences of optical disk recorders, and current write strategy parameters thereto require slight adjustment (i.e. adjusting dynamic write strategy parameters R ik  and F km ) for the optical disk recorder  100  and the loaded optical disk  11 . The measured write quality indices (generated by step S 1300 ) dissatisfying soft limits means that write qualities highly deviate from the target and current write strategy parameters thereto require a full write strategy adjustment, then the process proceeds to step S 1700 .  
         [0031]     Step S 1400  for verifying hard limits may not be prior to S 1500  for verifying soft limits. Steps S 1400  and S 1500  may be integrated into a single step. The objects of separation of steps S 1400  and S 1500  are to divide the measured write quality indices into certain categories such as requiring no adjustment (i.e. write quality is good), requiring slightly tuning (i.e. write quality can be effectively improved), requiring resetting (i.e. write quality is bad) or similar. Proper division of measured quality indices can reduce process steps and time for optimizing write strategy parameters.  
         [0032]     After performing step S 1600  slightly tuning R ik  and F km , the process proceeds to S 1800  to store current write strategy parameters, facilitating initiation of write strategy parameters for other optical disks of the same kind. After performing step S 1700  completely adjusting write strategy parameters, the process proceeds to S 1700   a  for further verification. If write quality indices satisfy predetermined target, the process proceeds to step S 1800  to store current write strategy parameters, otherwise, to step S 1810  to transmit current write quality indices to a host via an interface such as Integrated Device Electronics (IDE), Serial ATA (SATA) or Universal Serial Bus (USB), thereby the host will make a decision. The step S 1700   a  for verifying adjustment results may be integrated into step S 1700  for completely adjusting write strategy parameters, resulting in requiring no additional test writes. That is to say, when obtaining relevant write quality or performance indices via step S 1700 , step S 1700  can determine whether step S 1800  or S 1810  is subsequently performed.  
         [0033]     Step S 1800  stores the adjusted write strategy parameters. It may store the adjusted write strategy parameters in a memory device of the optical disk recorder  100 , such as Electrically Erasable Programmable Read-Only Memory (EEPROM) or flash ROM, alternately, it may transmit the adjusted write strategy parameters via an interface, such as IDE, SATA or USB, with the acquired manufacturer ID to a host, thereby enabling the host to store that in a storage device thereof.  
         [0034]      FIG. 5  is a flowchart illustrating a first embodiment of a method for adjusting dynamic write strategy parameters, performed in step S 1600  of  FIG. 3 . In step  1610 , mean length deviations from ideal ones for general (land,pit) and (pit,land) combinations are measured according to reproduced RF signals read from previous test write area. In step S 1620 , it determines whether the measured mean length deviations are smaller than a predetermined threshold. If so (i.e. the measured mean length deviation is acceptable), the process proceeds to step S 1660 , and otherwise, to step S 1630 . In step S 1660 , refined dynamic write strategy parameters D n+1 (R ik , F km ) are output.  
         [0035]     Dynamic write strategy parameter modifications of corresponding combinations (R ik , F km ) typically relate to mean length deviations from ideal ones of corresponding combinations (R ik , F km ). In step S 1630 , dynamic write strategy modifications d n (R ik , F km ) are calculated according to the measured mean length deviations of corresponding combinations S n (R ik , F km ). For example, corrections for any combinations of (R ik , F km ) can be determined by the following equation: 
 
 d ( R   ik   , F   km )= K ( R   ik   , F   km )* S ( R   ik   , F   km ), 
 
 where d(R ik , F km ) represents a correction for a particular combination of (R ik , F km ), S(R ik , F km ) represents a measured mean length deviations of a particular combination of (R ik , F km ), and K(R ik , F km ) represents a proportionality constant for a particular combination of (R ik , F km ). 
 
         [0036]      FIG. 6  is a flowchart illustrating a second embodiment of a method for adjusting dynamic write strategy parameters, performed in step S 1600  of  FIG. 3 . The differences from the first embodiment illustrated in  FIG. 5  are steps  1610   b ,  1620   b  and  1630   b . The second embodiment performs adjustments based on mean edge shift deviations (other than mean length deviations as shown in step S 1610  of  FIG. 5 ) from ideal ones for general (land,pit) and (pit,land) combinations. Thus, in step S 1610   b , mean edge shift deviations from ideal ones for general (land,pit) and (pit,land) combinations are measured according to reproduced RF signals read from previous test write area. In step S 1620   b , it determines whether the measured mean edge shift deviations (other than mean length deviation as shown in step S 1620  of  FIG. 5 ) are smaller than a predetermined threshold. In step S 1630   b , dynamic write strategy modifications d n (R ik , F km ) are calculated according to the measured mean edge shift deviation (other than mean length deviation as shown in step S 1630  of  FIG. 5 ) of corresponding combinations S n (R ik , F km ).  
         [0037]     After calculating dynamic write strategy modifications, step S 1640  determines whether test write number (i.e. runs) is smaller than a predetermined test limit. If so, the process proceeds to step S 1650 , and otherwise, to step S 1660 . Typically, the predetermined test limit equals one, namely, the dynamic write strategy parameters are often tuned to an acceptable level at one time. In step S 1650 , the next test writes with dynamic write strategy parameters D n+1 (R ik , F km )=D n (R ik , F km )+d n (R ik , F km ) are performed.  
         [0038]      FIG. 7  is a flowchart illustrating an embodiment of a method of full adjustment for all write strategy parameters. These write strategy parameters are divided into two kinds: static and dynamic write strategy parameters. These static write strategy parameters such as P w , OD/m, E k  and S k  of  FIGS. 1   a  and  1   b , relate to pattern lengths and are unaffected from combinations of previous and following patterns (i.e. are not required to be adapted for combinations of previous and following patterns). These dynamic write strategy parameters such as R ik  and F km  of  FIGS. 1   a  and  1   b , relate to combinations of previous and following T-length patterns, where i, k, m (i.e. T-lengths) may be as 3T to 6T or greater. The optimized static write strategy parameters are obtained by one-dimensional search in steps S 1710  to S 1750 . The optimized dynamic write strategy parameters for combinations of (R ik , F km ) are obtained by calculating corrections and incrementally modifying according to the calculated corrections in step S 1760 .  
         [0039]     In Step S 1710 , static write strategy parameters to be optimized are selected, such as P w , OD/m, E k  or S k  or any of the combinations, and simultaneously, in step S 1710 , an optimization sequence containing the selected static write strategy parameters is determined, such as P w , OD, P w , E k  and S k  in sequence. The combination of static write strategy parameters typically relate to soft/hard limits provided in steps S 1400  and S 1500 . Different static write strategy parameter combinations match different pairs of hard and soft limits. That is to say, static write strategy parameters to be optimized can be filtered by using different soft/hard limits in order to obtain an effective optimization sequence.  
         [0040]     In step S 1720 , a static write strategy parameter to be optimized is determined according to the determined optimization sequence.  FIG. 8  is a flowchart illustrating an embodiment for obtaining an optimized value using one-dimensional search. In step S 1731 , a series of candidate values X 1  to X n  are generated from a current value of the selected static write strategy parameter, where n represents quantity of candidate values. For example, one of candidate values is the base value increased or decreased by a shift value. In step S 1732 , a series of test writes in a write strategy with previously generated candidate values X 1  to X n  of the selected static write strategy parameters, and the remaining fixed static write strategy parameters are performed. In step S 1733 , RF signals are reproduced from previous test writes to measure write quality of the reproduced signals. In step S 1734 , the relative optimum candidate value is determined from the previously generated candidate values. In step S 1734 , it may determine one generated candidate value corresponding to the best write quality index as the best candidate value of the selected static write strategy parameter, or determine an average value of candidate values whose write quality index exceeds a predetermined threshold as the best candidate value of the selected static write strategy parameter. In steps S 1732  to S 1734 , it may measure the write quality indices till all test writes are completely performed, or may measure the write quality indices after a portion of test writes are performed and sequentially measure another portion til all test writes are performed. The write quality index may be RF signal asymmetry  33   s , data error rates  34   s , jitter magnitudes  35   s , mean length deviations for all pattern combinations  36   s , and mean edge shift deviations for all pattern combinations  37   s  output from the write quality detection unit  31  ( FIG. 3 ).  
         [0041]     Referring to  FIG. 7 , in step S 1740 , it determines whether write quality of the current write strategy parameters is acceptable. If so, the process proceeds to step S 1780 , otherwise, to step S 1750 . Step S 1740  performs no further test write and obtains write quality indices by measuring a test write area corresponding to the relative optimum value or values. In step S 1750 , it determines whether all selected write strategy parameters are optimized and the determined optimization sequence is finished. If so, the process proceeds to step S 1760  to perform dynamic write strategy parameter adjustment, otherwise, to step S 1720 .  
         [0042]     In step S 1760 , two embodiments of dynamic write strategy parameter adjustments are described in the above-described  FIGS. 6 and 7 . The dynamic write strategy modifications are calculated according to the measured mean length deviation or mean edge deviation of corresponding combinations, details of calculation described in the above.  
         [0043]     In step S 1770 , it determines whether write quality of previous test writes with newly obtained write strategy parameters satisfies predetermined target or optimization counter (i.e. runs) exceeds a predetermined limit. If so, the process proceeds to step S 1780  to output the measured write quality and optimized write strategy parameters, otherwise, to step S 1710  to start the next run of write strategy parameter optimization. Step S 1770  performs no further test write and obtains write quality indices by measuring the last test write area performed by the prior step. In practice, after performing only single run of full adjustment for all write strategy parameters, acceptable write quality is acquired. Therefore, excellent write quality could be attained by setting the predetermined limit to one.  
         [0044]     Certain terms are used throughout the description and claims to refer to particular system components. As one skilled in the art will appreciate, consumer electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function.  
         [0045]     Although the invention has been described in terms of preferred embodiment, it is not limited thereto. Those skilled in this technology can make various alterations and modifications without departing from the scope and spirit of the invention. Therefore, the scope of the invention shall be defined and protected by the following claims and their equivalents.