Optical recording/reproducing write strategy method, medium, and apparatus

A write strategy method, medium, and apparatus. The method includes writing a signal to a storage medium by using a predetermined power and an initial write strategy, calculating variation characteristics of a data signal which separately correspond to variations of write strategy parameters, if the written signal does not satisfy initial quality standards, and calculating correlations among periods of the data signal and correlations among the write strategy parameters by using the variation characteristics of the data signal, and determining the write strategy parameters based on the correlations among the periods of the data signal and the correlations among the write strategy parameters.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2007-0101683, filed on Oct. 9, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

One or more embodiments of the present invention relate to a write strategy method, medium, and apparatus, and more particularly, to a method, medium, and apparatus, including an optical recording/reproducing method, medium, and apparatus, automatically generating and providing an optimized write strategy in accordance with a specific writing characteristic of each optical disc drive.

2. Description of the Related Art

In order to write predetermined data to an optical medium, a laser diode is modulated in accordance with an encoded electric signal. In this case, a pulse type of the laser diode is modulated so that an optical recording/reproducing apparatus has an optimized writing characteristic. Determining the pulse type of the laser diode corresponds to designing a write strategy. However, in order to design the write strategy, an innumerably large number of write strategy parameters, which specifically represent the pulse type, are separately defined.

Here, the recording/reproducing apparatus is a recording device, such as an optical disc drive, that may write data by using a light source such as a laser. Examples of the corresponding medium include a compact disc-recordable (CD-R), a digital video disc (DVD), a digital video disc-recordable (DVD-R), and a compact disc-rewritable (CD-RW).

Various types of data may be written to or stored on the underlying optical recording medium. The types of data generated by using a non return to zero, inverted (NRZI) modulation, method will now be described with reference toFIGS. 1A through 1D. Hereinafter, a signal generated by using the NRZI modulation method will be referred to as an NRZI signal.

FIG. 1Aillustrates write strategy parameters and a type of laser diode pulse which are used for a CD-R, a DVD-R, or an organic blue-ray disc-recordable (BD-R).

Referring toFIG. 1A, a referenced data signal101corresponds to an actual data signal to be written. The waveform of the data signal101is generated by using an NRZI modulation method. The data signal101is shown as having a value of 1000001. Here, a logic high level is referred to as a mark and a logic low level is referred to as a space.

A laser diode signal103corresponds to a laser diode signal in accordance with a write strategy applied to a DVD-R or an organic BD-R. That is, in order to write the data signal101, the write strategy has to be designed so as to generate the laser diode signal103as illustrated inFIG. 1. Referenced parameters PB, PC, dTtop, OD, dTLP, dTE, TLPand the like are referred to as the write strategy parameters. That is, in order to design the write strategy, each of the write strategy parameters has to be defined.

FIG. 1Bis a diagram illustrating write strategy parameters and a type of laser diode pulse which are used for a CD-RW high speed (HS)/low speed (LS), a DVD-R normal speed (NS), a BD-R, or a blue-ray disc-rewritable (BD-RW) LS.

Referring toFIG. 1B, in order to write a data signal111on a CD-RW HS/LS, a DVD-R NS, a BD-R, or a BD-RW LS, a laser diode signal113has to be generated. Here, the write strategy parameters such as PE, dTtop, POD, and TMPhave to be defined.

FIG. 1Cis a diagram illustrating write strategy parameters and a type of laser diode pulse which are used for a CD-RW ultra speed (US) or a digital video disc-rewritable (DVD-RW) HS.

Referring toFIG. 1C, in order to write a data signal121to a CD-RW US or a DVD-RW HS, a laser diode signal123has to be generated. All parameters illustrated inFIG. 1Chave to be defined in order to design a write strategy of the CD-RW US or the DVD-RW HS.

FIG. 1Dis a diagram illustrating write strategy parameters and a type of laser diode pulse which are used for a BD-RW HS.

Referring toFIG. 1D, in order to write a data signal131to a BD-RW HS, a laser diode signal133has to be generated. All parameters illustrated inFIG. 1Dhave to be defined in order to design a write strategy of the BD-RW HS.

The write strategy parameters, such as dTtop, TOD, Ttop, dTMP, TMP, dTLP, TLP, and dTEwhich are illustrated inFIGS. 1A through 1D, are separately and differently defined in accordance with the standards and type of the recording medium, such as a writing speed, a writing characteristic of a manufacturer, set deviations of an optical disc drive, and a writing environment. However, in general, the manufacturer of the optical disk drive optimizes and determines the write strategy parameters during manufacture in accordance with the standards and type of the recording medium, such that select write strategy parameters are fixed post-manufacture. In this case, the manufacturer determines the optimized write strategy parameters by analyzing periodical lengths of an NRZI pattern and the amount of timing jitter. The determining of the optimized write strategy parameters is referred to as the designing of a write strategy.

FIG. 2illustrates a conventional method of designing, storing, and authenticating a write strategy for an optical recording medium.

Referring toFIG. 2, the conventional method includes operations210,220, and230. First, in operation210, a manufacturer designs the write strategy by analyzing periodical lengths of an NRZI pattern and the amount of timing jitter and by determining optimized write strategy parameters.

In operation220, the write strategy designed in operation210is stored in firmware. The write strategy may be stored in a memory of an optical recording/reproducing apparatus by performing porting, compiling, and downloading processes.

The optical recording/reproducing apparatus may, thus, store the write strategy optimized for a recording medium, a writing speed, and information on a manufacturer of the recording medium. The stored write strategy will be read and executed later.

Then, a writing operation is performed by using the write strategy determined in operation210. By performing the writing operation, the write strategy may be authenticated in terms of whether it has been correctly designed, in operation230. After the authenticating, if the quality of the write strategy is below an acceptable quality level, the write strategy is modified or redesigned by tuning certain parameters.

However, several hundred types of optical disc drives are produced by different manufacturers. Accordingly, quite a large amount of time is required to design a write strategy by determining optimized write strategy parameters of each type of optical disc drive. Also, a large part of a production period of the optical disk drive involves designing the write strategy.

Furthermore, a certain optical recording/reproducing apparatus may not easily determine all optimized write strategies for all conventionally released optical recording media produced by all manufacturers.

In the above-described conventional method, an innumerably large number of combinations of write strategy parameters for each optical recording medium may not be easily measured and thus optimized write strategy parameters may not be easily determined.

Still further, in optical recording/reproducing apparatuses of the same model, write strategy parameters may have deviations for different settings. However, the conventional method does not consider these set deviations and thus does not compensate for the set deviations.

In addition, when a new optical recording medium is released, a newly designed write strategy applicable to the new optical recording medium and firmware for a corresponding optical recording/reproducing apparatus has to be upgraded. That is, a firmware upgrade has to be performed in order for a conventional optical recording/reproducing apparatus, which is using the new optical recording medium, to execute an appropriate optimized write strategy.

The write strategy is very important for determining the quality of all data to be stored in and be read from an optical recording medium. However, as described above, the conventional methods may not compensate for deviations of write strategy parameters that exist regarding the optical recording medium and the optical recording/reproducing apparatus. Furthermore, when a new optical recording medium is released, conventional methods may not appropriately cope with new optical recording media and may not generate and use an appropriate or optimized write strategy.

SUMMARY

One or more embodiments of the present invention provide a method, medium, and apparatus, inclusive of an optical recording/reproducing method, medium, and apparatus, automatically generating and providing an optimized write strategy.

To achieve the above and/or other aspects and advantage, embodiments of the present invention include a method of generating and providing a write strategy, the method including writing a signal to a storage medium using a predetermined power and an initial write strategy, calculating variation characteristics of a data signal, read from the storage medium, which separately correspond to variations of write strategy parameters, if the written signal, as read from the storage medium, does not satisfy defined quality standards, and calculating correlations among periods of the data signal and correlations among the write strategy parameters using the variation characteristics of the data signal, and determining corresponding write strategy parameters for a write strategy for subsequent writing to the storage medium based on the calculated correlations among the periods of the data signal and the calculated correlations among the write strategy parameters.

To achieve the above and/or other aspects and advantage, embodiments of the present invention include a method of generating and providing a write strategy by an optical recording/reproducing apparatus, the method including determining whether the optical recording/reproducing apparatus supports a stored write strategy corresponding to an optical recording medium carried by the optical recording/reproducing apparatus, writing a signal to the optical recording medium using a predetermined power and a default write strategy, if the optical recording/reproducing apparatus does not support the stored write strategy, calculating variation characteristics of a data signal, read from the optical recording medium, which separately correspond to variations of write strategy parameters, if the written signal, as read from the optical recording medium, does not satisfy defined quality standards, and calculating correlations among periods of the data signal and correlations among the write strategy parameters by using the variation characteristics of the data signal, and determining corresponding write strategy parameters for a write strategy for subsequent writing to the optical recording medium based on the calculated correlations among the periods of the data signal and the calculated correlations among the write strategy parameters.

To achieve the above and/or other aspects and advantage, embodiments of the present invention include an optical recording/reproducing apparatus including an encoder to convert information data transmitted from a host into a signal to be recorded to an optical recording medium, and a write strategy generator to perform a writing operation of the signal using an optimized write strategy, wherein the write strategy generator writes the signal to the optical recoding medium using a predetermined power and an initial write strategy, and, based upon a determination of whether a signal read from the optical recording medium corresponding to the written signal satisfies defined quality standards, the write strategy generator writes a data signal to the optical recording medium by varying each of plural write strategy parameters in an operation range and calculates write strategy parameters for a write strategy for subsequent writing to the optical recording medium based on calculated correlations among periods of the data signal, as read from the optical recording medium, and calculated correlations among the plural write strategy parameters, as observed from the read data signal.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, embodiments of the present invention may be embodied in many different forms and should not be construed as being limited to embodiments set forth herein. Accordingly, embodiments are merely described below, by referring to the figures, to explain aspects of the present invention.

FIG. 3illustrates an optical recording/reproducing apparatus300, according to an embodiment of the present invention.

A structure and operation of the optical recording/reproducing apparatus300will now be briefly described with reference toFIG. 3.

Referring toFIG. 3, the optical recording/reproducing apparatus300may include a laser diode driver315, a write strategy generator320, an optical pickup unit301, and an encoder325, for example. The optical recording/reproducing apparatus300may further include an analog front end305, a digital signal processor307including a signal quality evaluation unit309, and a decoder313. In addition, the optical recording/reproducing apparatus300may further include a host interface330, an automatic power control circuit303, a flash read-only memory (ROM)321, a control unit323, and an audio circuit311. Here, a micro computer (MICOM) may be used as the control unit323, and alternate embodiments with differing configurations are also available.

The host interface330may interface a host (not shown) with the decoder313, or interface the host with the encoder325. Here, as an example, a personal computer (PC) may be used as the host.

The encoder325can encode information data received from the host in accordance with data standards of an optical recording medium and output the encoded data. Various data standards may exist. However, hereinafter, it is assumed that the data to be stored in the optical recording medium is a non return to zero, inverted (NRZI) signal, noting that alternatives are also available.

Thus, the write strategy generator320may apply an optimized write strategy to the NRZI signal output from the encoder325and generate a corresponding tuned switching signal. Operations of such a write strategy generator320will be described in greater detail with reference toFIGS. 6Athough6C,7A,7B, and8. Accordingly, further detailed descriptions thereof will be omitted here.

The automatic power control circuit303may perform automatic power control on channels of various voltage levels such as read, erase, and peak voltage levels, for example.

Here, the channels provide a plurality of different voltage levels. For example, inFIG. 1A, a writing pulse of a laser diode uses four voltage levels a, b, c, and d. In this case, the voltage levels a, b, c, and d may be respectively supplied by first through fourth channels, for example.

When data is reproduced, the laser diode driver315drives the laser diode so as to switch a high frequency modulated reproduction direct current (DC). When data is written, the laser diode driver315drives the laser diode by switching, for example, the voltage levels in channels which are output from the automatic power control circuit303into a designed and optimized write strategy signal, so as to form an optimized NRZI pattern on the optical recording medium.

The optical pickup unit301may include a laser diode for each wavelength, a plurality of passive optical devices, a plurality of photo detectors, and a plurality of passive optical device control operating devices, for example. The optical pickup unit301may be used as a signal sensor or a control device which is required to reproduce data stored in the optical recording medium or to write data transmitted from the host.

The analog front end305writes data on the optical recording medium, and then processes the written data so as to generate a radio frequency (RF) signal. The digital signal processor307processes the RF signal and various servo signals.

The digital signal processor307and the analog front end305will be described in greater detail with reference toFIG. 4.

The decoder313may then decode the RF signal, the control unit323may control general operations for writing and reproducing data, and the flash ROM321may store related data required for the write strategy.

FIG. 4illustrates an analog front end305and the digital signal processor307, such as those illustrated inFIG. 3, according to an embodiment of the present invention.

Referring toFIG. 4, the analog front end305for processing an RF signal may include a voltage gain amplifier (VGA)401, a partial response equalizer (PR EQ)403, and an analog gain controller (AGC)405, for example.

The digital signal processor307may include an analog to digital converter (ADC)411, a PR EQ413, a viterbi decoder415, a least mean squares (LMS) unit417, and a signal quality evaluation unit419, for example.

The VGA401receives and amplifies an RF signal, the PR EQ403amplifies the RF signal so that the RF signal of each period has the same amplitude level, and the AGC405is coupled with the VGA401for automatically maintaining the RF signal to be a constant size.

In the digital signal processor307for processing signals in order to improve the discrimination of a short period, the ADC411converts the RF signal into a digital signal

The PR EQ413amplifies the digital signal so that each period of the digital signal has the same voltage level as a corresponding period of an NRZI signal. Here, the PR EQ413may be a digital equalizer.

The viterbi decoder415decodes the digital signal by using a Hamming function so as to minimize an error rate of data to be reproduced from an optical recording medium. Here, the Hamming function uses a principal that a number ‘a’ of errors may be corrected if a Hamming distance ‘d’ between pieces of digital information is greater than or equal to ‘2a+1’. That is, the viterbi decoder415minimizes the error rate by selecting the closest code in terms of the Hamming distance.

The LMS unit417operates so as to maximize use of the PR EQ413.

The signal quality evaluation unit419measures periodical lengths of the NRZI signal and the amount of timing jitter. The signal quality evaluation unit419may also measure the amount of jitter of rising and falling edges of a data signal (the NRZI signal). That is, the signal quality evaluation unit419may collect data that may evaluate the quality of the data signal. The collected data may then be transmitted to a data signal observation unit693(refer toFIG. 6C) to be described in greater detail below.

Referring back toFIG. 3, operations of the optical recording/reproducing apparatus300may be performed as follows.

Information output from the host pass through the host interface330. The encoder325then encodes an input signal so as to generate the example NRZI signal. The write strategy generator320may accordingly apply an optimized write strategy to the encoded NRZI signal and generate a corresponding switching signal for each channel. Then, the laser diode driver315switches DC voltage levels of channels and generates a writing pulse having a corresponding optimized writing characteristic. The laser diode driver315uses the writing pulse so as to modulate a laser diode. The optical pickup unit301may, thus, then form the NRZI signal having corresponding marks and spaces on the optical recording medium, in accordance with an optical power of the modulated laser diode.

Furthermore, reproducing operations of the optical recording/reproducing apparatus300may further be performed as described below.

First, a reproduction DC optical power modulated with a high frequency and small amplitudes is projected toward the corresponding optical recording medium. Then, the optical pickup unit301generates an RF signal according to such mark and space patterns of the optical recording medium by using a diffractive optical phenomenon. The RF signal may then be amplified and standardized by passing through the analog front end305. Then, the amplified and standardized RF signal may be converted into a square wave NRZI signal by passing through the digital signal processor307, and then decoded by passing through the decoder313so as to be converted into data recognizable by the host.

Correlations between write strategy parameters and mark lengths will now be further described with reference toFIGS. 5A through 5C. Correlations between write strategy parameters and space lengths may also be used. However, for brevity purposes, correlations between write strategy parameters and mark lengths will now be exemplarily described.

FIG. 5Agraphically illustrates correlations between write strategy parameters and mark lengths, according to an embodiment of the present invention.

FIG. 5Aillustrates variations of mark lengths3T,4T, and5T when a writing operation is performed by varying a write strategy parameter, for example, Ttop, so as to increase a mark length2T. Here, the X axis represents variations of the write strategy parameter when a mark length is2T and the Y axis represents variations of the mark lengths2T,3T,4T, and5T.

That is, if the write strategy parameter varies so as to increase the mark length2T, the mark length2T is inevitably increased. In this case, the write strategy parameter applied to the mark length2T does not influence only the mark length2T. As illustrated inFIG. 5A, the write strategy parameter also decreases the mark lengths3T,4T, and5T. That is, the write strategy parameter only applied to the mark length2T also influences other mark lengths such as the mark lengths3T,4T, and5T.

As such, the fact that a mark length mT, instead of just a mark length nT, is increased when a corresponding write strategy parameter is increased so as to increase the mark length nT, means that correlations exist between each write strategy parameter and mark lengths. If the correlations do not exist, although a write strategy parameter varies, only a corresponding mark length may vary and other mark lengths may not vary.

Herein, in embodiments of the present invention, such correlations are defined as a correlation effect.

FIG. 5Bgraphically illustrates correlations between write strategy parameters and mark lengths, according to another embodiment of the present invention.

Referring toFIG. 5B, a write strategy parameter is increased so as to increase a mark length3T. In this case, not only does the mark length3T vary (in an increasing direction), but also mark lengths2T,4T, and5T vary (in a decreasing direction).

FIG. 5Cgraphically illustrates correlations between write strategy parameters and mark lengths, according to another embodiment of the present invention.

Referring toFIG. 5C, a write strategy parameter is increased so as to increase a mark length4T. In this case, not only does the mark length4T vary (in an increasing direction), but also mark lengths2T,3T, and5T vary (in a decreasing direction for the mark lengths2T and3T and in an increasing direction for the mark length5T). InFIG. 5C, although the write strategy parameter is increased so as to increase the mark length4T, the mark length5T is also increased. Thus, the fact that correlations exist between write strategy parameters and mark lengths becomes more evident.

As described above in relation toFIGS. 5A through 5C, embodiments of the present invention consider a resultant determination that a correlation effect occurs between write strategy parameters and mark lengths and thus provides an optimized write strategy method, medium, and apparatus, including a corresponding an optical recording/reproducing apparatus, by removing these correlation effects. Such optimized write strategies will be described in greater detail below with reference toFIGS. 6Athough6C,7A,7B, and8.

FIG. 5Dillustrates, through tables560and570, determined correlations between previous signal periods and current signal periods, according to an embodiment of the present invention.

Referring toFIG. 5D, table560represents write strategy parameters in accordance with mark lengths and table570represents write strategy parameters in accordance with space lengths.

In table560, the reference numeral561represents current mark lengths, the reference numeral563represents previous mark lengths, and the reference numeral565represents write strategy parameters. For example, the reference numeral567represents a write strategy parameter X32when a previous mark length is3T and a current mark length is2T. The reference numeral568represents a write strategy parameter X34that is applied to the current mark length4T when the previous mark length is3T and the current mark length is4T. That is, when a previous mark length is aT and a current mark length is bT, Xab represents a write strategy parameter which is applied to the current mark length bT and is influenced by the previous mark length aT.

The table570represents write strategy parameters in accordance with space lengths and detailed descriptions of the table570correspond to the description of the table560. That is, when a previous space length is aT and a current space length is bT, Yab represents a write strategy parameter that is applied to the current space length bT and is influenced by the previous mark length aT.

As described above, according toFIG. 5D, the write strategy parameters may be calculated in consideration of the above-described correlation effect in relation toFIGS. 5A through 5C.

FIG. 6Aillustrates a write strategy method, according to an embodiment of the present invention.

Referring toFIG. 6A, a signal is written to the corresponding medium by using an initial write strategy, in operation600. Here, the signal is written by using power having a predetermined value. In an embodiment, the initial write strategy may be a default write strategy that may be applied to any optical recording medium.

The data signal is written by varying each write strategy parameter in a predetermined range, in operation650. Here, in an embodiment, operation650is performed if the quality of the signal written in operation600is determined to be of an unacceptable quality level, for example.

The write strategy parameters may be calculated in consideration of the calculated correlations among periods of the data signal and calculated correlations among write strategy parameters, in operation670. In operation670, the write strategy parameters may be calculated in consideration of the correlations among the periods of the data signal and the correlations among the write strategy parameters by measuring and using variations of the data signal written in operation650.

A method for a write strategy and an optical recording/reproducing apparatus implementing the same, according to an embodiment the present invention, will now be described in greater detail with reference toFIGS. 6B and 6C.

FIG. 6Billustrates a method such asFIG. 6A, according to an embodiment of the present invention.FIG. 6Cillustrates a write strategy generator320, such as illustrated inFIG. 3, according to an embodiment of the present invention.

Here, an initial write strategy and corresponding power may be prepared in operation601. As described above in relation toFIG. 6A, the initial write strategy may be a default write strategy that has been initially set, for example. The default write strategy may be generally applied to an optical recording medium. The power may further be from a current source having voltage levels to be used in such an initial write strategy.

In accordance with the initial write strategy, the signal is written to the corresponding medium by performing first optimum power control, in operation605. Optimum power control may be performed by optimizing and thus controlling the power. That is, when a transmitted signal is written by using predetermined power, the optimum power control may be performed by searching for a power value that allows the signal to have an optimized writing quality.

A power level applied to perform the first optimum power control may be determined and a corresponding data signal written by using the determined power level.

With brief reference toFIG. 6C, such operations601and605may be performed by an initial writing unit691in the write strategy generator320, for example.

It may then be determined whether the quality of the signal written in operation605is low, or not of a sufficiently high level, in operation610.

Here, as only an example, the quality of the written signal may be determined in accordance with the amount of timing jitter of a signal pattern, the amount of jitter of rising and falling edges, absolute lengths of marks and spaces (for example, accuracies of written mark lengths in comparison with target mark lengths), an error rate that is determined when the written signal is decoded, the quality of restored data, or the possibility of restoring of the written data (how completely the written signal is restored by performing, for example, error correction). For example, when a user sets an allowable amount of jitter for reading the signal to be 10%, if the amount of jitter of the written signal is equal to or less than 10%, the quality of the written signal is determined to be sufficiently high. If the amount of jitter of the written signal is greater than 10%, the quality of the written signal is determined to be low.

In one or more embodiments of the present invention, allowable ranges for the amount of timing jitter of a signal pattern, the amount of jitter of rising and falling edges, absolute lengths of marks and spaces (for example, accuracies of written mark lengths in comparison with target mark lengths), an error rate that is extracted when the written signal is decoded, the quality of restored data, or the possibility of restoring of the written data (how completely the written signal is restored by performing, for example, error correction) are regarded may be initial quality standards. That is, if the above-described initial quality standards are satisfied, a writing quality may be determined to be high.

If the quality of the written signal is determined to be high in operation610, further writing operations may be performed on the optical recording medium by using the initial write strategy such as the default write strategy in operation615. Operation615may further be performed by a write strategy executor (not shown) in the write strategy generator320ofFIG. 6C.

Alternatively, the data signal may be written by varying each write strategy parameter in an operative range, in operation612.

With further brief reference toFIG. 6C, operations610and612may be performed by a data signal observation unit693in the write strategy generator320, for example. Here, the quality of the written signal may be determined by using data regarding a signal quality which is transmitted from the signal quality evaluation unit309illustrated inFIG. 3. The quality of the written signal may also be determined by using data errors and restored data of the decoder313illustrated inFIG. 3.

In addition, operations610and612may be performed by the data signal observation unit693that automatically receives the data regarding the signal quality and evaluates the quality of the written signal. That is, the data signal observation unit693may receive the data regarding the signal quality from the signal quality evaluation unit309and determine the quality of the written data by using the received data. According to an embodiment, if the quality of the written signal is low, the data signal observation unit693may, thus, automatically perform operation612.

Variation curves of mark or space lengths in accordance with timing variations may further be calculated in operation620. Variations of mark lengths or variations of space lengths are observed by varying each write strategy parameter. Results of observations may be written and stored in the write strategy generator320. Here, the timing variations are timing values of the write strategy parameters. Accordingly, the variations of the mark or space lengths may be observed by varying each write strategy parameter on a time axis. The variation curves may, thus, be calculated by using data regarding the variations of the mark or space lengths in accordance with deviations of the write strategy parameters.

Here, the variation curves of the data signal may be calculated on each of all mark lengths, such as2T,3T,4T, through to9T. In addition, as described above in relation toFIGS. 5A through 5D, the variation curves of the mark lengths may be separately calculated in consideration of previous pattern periods and current pattern periods. That is, if a mark length of a previous pattern is jT and a mark length of a current pattern is iT, a variation curve may be calculated by varying values of i and j.

The variation curves of the data signal may also be calculated on each of all space lengths, such as2T,3T,4T, through to9T.

A variation curve of a mark length will now be described in detail with reference toFIG. 7A. The variation curve may also be applied to a space length.

FIG. 7Agraphically illustrates a variation curve of a mark length as a timing write strategy parameter varies, according to an embodiment of the present invention.

The variation curve of the mark length shows variations of a corresponding mark length as a timing parameter from among write strategy parameters. Accordingly, the X axis represents the corresponding write strategy parameter and the Y axis represents the mark length. Here, a write strategy parameter dTEthat is applied to a mark length2T will be exemplarily described.

According to this embodiment, the variation curve of the mark length will be exemplarily described. However, a variation curve of a space length may also be used. That is, the variation curve of the space length which represents variations of the space length in accordance with variations of a write strategy parameter (particularly, a timing parameter) may also be used. Furthermore, the variation curves of the mark length and the space length may be used together.

Referring toFIG. 7A, as the write strategy parameter is increased, the mark length is also increased. The variation curve is represented as a straight line type and thus may be represented by using a linear equation, for example. Accordingly, the slope and a y-intercept may be calculated by analyzing the calculated variation curve of the mark length (or the space length). Herein, the slope is defined as a change ratio.

InFIG. 7A, a change ratio711of a straight line710is 1.3124 and a y-intercept713is 18.003.

FIG. 7Bgraphically illustrates a variation curve of a mark length as a timing write strategy parameter varies, according to another embodiment of the present invention.

Referring toFIG. 7B, variations of a mark length2T in accordance with variations of a write strategy parameter dTEthat is applied to the mark length2T are exemplarily illustrated.

FIG. 7Billustrates a case when a write strategy is performed by using the same model of optical recording medium as the optical recording medium used inFIG. 7A. However, different initial write strategies, such as default write strategies, are applied toFIGS. 7A and 7B.

If the default write strategies are different from each other, although the same write strategy parameter varies or is controlled, the same variation curve may not be obtained. If the default write strategies are different from each other, although the same write strategy parameter such as the write strategy parameter dTEvaries, different variation curves are obtained due to correlations of other write strategy parameters.

Accordingly, although the mark length is extracted by varying the same write strategy parameter dTEinFIGS. 7A and 7B, slopes and y-intercepts of straight lines710and730are different to each other.

As such, it is clear that optimized write strategy parameters may not be easily obtained due to correlations among write strategy parameters even when a write strategy is executed on the same model of optical recording medium. Likewise, it may be construed that a previously designed and optimized write strategy parameters may vary in a different manner according to deviations between optical recording media or deviations between optical recording/reproducing apparatuses. Here, set deviations between optical recording/reproducing apparatuses means that writing conditions of the same product group may vary due to optical deviations of an optical pickup unit (OPU) and differences in types of optical spot or depths of focus.

In addition, the write strategy may be influenced by a writing environment. Here, variations of the writing environment means that an external environment varies due to variations of temperature or humidity, for example, at a point of writing.

Based on the above-described media variations, set variations, and environmental variations, it may be determined that an optimized write strategy should be changed.

Thus, in an embodiment, subsequent operations may be performed by separately calculating a variation curve of a written data signal, such as the variation curves illustrated inFIGS. 7A and 7B, with regard to each of all available combinations of write strategy parameters of an optical recording medium. By separately calculating the variation curve, the above-described media variations, set variations, and environment variations, which occur on the optical recording medium, may be determined so that the optimized write strategy may be designed.

Referring back toFIGS. 6B and 6C, a correlation matrix may, thus, be calculated by using the variation curves of the data signal, calculated in operation620, in operation624. For example, the below Equation 1 is a matrix for calculating write strategy parameters. The matrix of Equation 1 is calculated by using the variation curves of the data signal, which are calculated in operation620.

Here, M_Ak of functions {circle around (1)} represents a mark length when a current mark length is kT, a_ij of functions {circle around (2)} represents a change ratio (corresponding to the slope illustrated inFIGS. 7A and 7B) when a current mark length is iT and a previous mark length is jT, A_k of functions {circle around (3)} represents a corresponding write strategy parameter when a mark length is kT, and K_Ak of functions {circle around (4)} represents a y-intercept (corresponding to the y-intercepts of the variation curves illustrated inFIGS. 7A and 7B). The y-intercept K_Ak is a linear sum of y-intercepts of all previous data signals having mark lengths2T through mT.

The write strategy parameters may, thus, be calculated in consideration of correlations among periods of the data signal and correlations among the write strategy parameters, in operation625.

By using Equation 1, the write strategy parameters may be calculated in consideration of the correlations among the write strategy parameters and the correlations among the periods (marks and spaces) of the data signal, which are described above in relation toFIGS. 5A through 5D,7A, and7B.

Here, again, the correlations among the write strategy parameters mean that a certain write strategy parameter may influence other write strategy parameters, as described above in relation toFIGS. 7A and 7B. The variation curves may be calculated by varying each write strategy parameter in operation620. Thus, the correlations among the write strategy parameters may be reflected.

The correlations among the periods of the data signal mean that previous mark lengths (or space lengths) influence current mark lengths (or space lengths), as described above in relation toFIGS. 5A through 5D. In functions {circle around (2)} of Equation 1, a slope and a y-intercept are calculated by reflecting previous mark lengths and current mark lengths. Thus, Equation 1 may reflect the correlations among the periods of the data signal.

The write strategy parameters may further be calculated by using the correlation matrix calculated in operation624, in operation625. The write strategy parameters may be calculated by inversely performing functions {circle around (3)} of Equation 1. By moving functions {circle around (4)} to the right of Equation 1 and forming an inverse matrix of functions {circle around (2)}, write strategy parameters of functions {circle around (3)} may be calculated.

G_k of functions {circle around (3)}′ is another write strategy parameter. For example, if A_k is Ttopwhen a mark length is kT, G_k may be dTEwhen the mark length is kT.

Deviations of the write strategy parameters may further be compensated for, in operation630.

In operations624and626, each write strategy parameter may, thus, be calculated by varying the write strategy parameter and maintaining the other write strategy parameters as they are. Accordingly, the correlations among the write strategy parameters remain.

In order to remove the correlations from among the write strategy parameters, the write strategy parameters may be calculated by repeating operations624and626several times. Then, in consideration of the deviations of the write strategy parameters which are repeatedly calculated, write strategy parameters having minimum error deviations are selected.

Again with brief reference toFIG. 6C, operations620,624,626, and630may be performed by an optimized write strategy calculation unit695in the write strategy generator320, for example.

Accordingly, optimized write strategy parameters may be calculated by performing the operations described above in relation toFIGS. 6A through 6C.

FIG. 8illustrates a write strategy method, according to another embodiment of the present invention.

Referring toFIG. 8, it may be determined whether an optical recording/reproducing apparatus supports a write strategy optimized for a corresponding optical recording medium, in operation801.

As described above in relation toFIGS. 1 and 2, the optical recording/reproducing apparatus may store and/or support the write strategy optimized for the corresponding optical recording medium. As such, it may be determined whether a certain optical recording/reproducing apparatus recognizes a corresponding optical recording medium and supports a write strategy optimized for the optical recording medium. That is, it may be determined whether the optical recording/reproducing apparatus includes the write strategy optimized for the optical recording medium.

If it is determined that the optical recording medium is supported by the optimized write strategy in operation801, first optimum power control may be performed by using an initial write strategy that has been previously designed and is supported by the optical recording/reproducing apparatus, in operation805.

It is then determined whether a written signal, e.g., by performing the first optimum power control in operation805, satisfies initial quality standards, in operation810. Whether the written signal satisfies the initial quality standards may be performed in accordance with how accurately a data signal such as a NPZI signal to be written is written or read to/from the corresponding medium. The determining of whether the written signal satisfies the initial quality standards may correspond to operation610illustrated inFIG. 6B.

If it is determined that the written signal satisfies the initial quality standards in operation805, further writing operations may be performed by using the previously designed corresponding write strategy, in operation840.

If it is determined that the optical recording medium is not supported by the optimized write strategy in operation801, the write strategy method illustrated inFIGS. 6A and 6B, for example, may be performed, in operation820.

After operation820is performed, second optimum power control may then be additionally performed and it may be determined whether a corresponding written signal, e.g., by performing the second optimum power control, satisfies the initial quality standards, in operation825.

If it is determined that the written signal, e.g., by performing the second optimum power control, satisfies the initial quality standards in operation825, the method may proceed to operation840and further writing operations performed.

If it is determined that the written signal, e.g., by performing the second optimum power control, does not satisfy the initial quality standards in operation825, operation820may then be repeated by varying a target mark length, in operation830.

That is, solutions (optimized write strategy parameters) of inverse functions of the correlation matrix of Equation 1 may be calculated by increasing or decreasing the target mark length.

Quality characteristics of the data signal which are obtained (reproduced) by repeating operation820may further be evaluated and write strategy parameters having the best writing qualities selected.

Here, for example, it may be determined whether a written data signal satisfies the quality standards in accordance with an error rate of error correction coded (ECC) data or error detection coded (EDC) data. Such a determining may correspond to the description operation610illustrated inFIG. 6B. For example, write strategy parameters having minimum amounts of timing jitter may be selected by checking variations of the amount of timing jitter.

It may still further be determined whether operation830is repeated more than n times in operation835.

Here, n is determined in accordance with the quality of the reproduced data signal. With regard to the above-described correlations among the write strategy parameters, n is determined in such a manner that deviations among the write strategy parameters may be saturated to certain amounts. For example, if the deviations among the write strategy parameters are saturated when operation830is repeated five times, n may be determined to be five.

If operation830is repeated more than n times, the method may proceed to operation840and further writing operations performed.

If operation830is not repeated more than n times, the method returns to operation820.

FIG. 9Aillustrates a histogram of an RF signal divided according to periods, in a conventional write strategy method.

In the conventional method, if an optical recording medium is not supported by an optimized write strategy, if set deviations exist, or if a writing environment changes, the optimized write strategy may not be executed.

Referring toFIG. 9A, the RF signal is distributed in broad ranges and overlapping regions exist. For example, an overlapping region exists between distribution graphs of mark lengths2T and3T. As such, write strategy parameters have larger errors in the overlapping regions.

Referring to a table illustrated below the histogram ofFIG. 9A, the minimum value of σ/T (standard variation versus period) is 16.192769% so as to have large variations. That is, the timing jitter is greater than 16.19%.

FIG. 9Billustrates a histogram of an RF signal divided according to periods, in a write strategy method according to an embodiment of the present invention.

Referring toFIG. 9B, the RF signal is distributed in relatively narrow ranges compared toFIG. 9A. Also, an overlapping region does not exist between a current mark length nT and a neighboring mark length (n+1)T.

Referring to a table illustrated below the histogram ofFIG. 9B, values of σ/T are approximately 7%. That is, the method according to this embodiment has an amount of timing jitter which is reduced by more than 7% compared to the amount of timing jitter of the conventional method.

As described above, according to one or more embodiments of the present invention, by measuring and evaluating writing characteristics of several to all available combinations of write strategy parameters, optimized write strategy parameters may be obtained. Thus, an error rate of a write strategy can be minimized so that time for redesigning the write strategy may be reduced.

Deviations of an optimized write strategy, which occur in the same model of optical disk drive, may be solved and an error rate of set evaluations, which relates to a writing quality, may be reduced when the optimized write strategy is developed.

An optimized write strategy may also be automatically designed in a new optical disk drive having an unknown write strategy. Thus, an optimum writing quality may be maintained without having to upgrade firmware and the cost for upgrading the firmware may be reduced.

Although a writing characteristic varies due to variations of an environment such as temperature and humidity at a point of writing, an optimized write strategy may also be designed so as to cope with the variations.

Correlations among marks or spaces and correlations among write strategy parameters may be minimized so that a writing quality of a data signal may be improved.

In addition to the above described embodiments, embodiments of the present invention can also be implemented through computer readable code/instructions in/on a medium, e.g., a computer readable medium, to control at least one processing element to implement any above described embodiment. The medium can correspond to any medium/media permitting the storing and/or transmission of the computer readable code.

The computer readable code can be recorded/transferred on a medium in a variety of ways, with examples of the medium including recording media, such as magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.) and optical recording media (e.g., CD-ROMs, or DVDs), and transmission media such as media carrying or controlling carrier waves as well as elements of the Internet, for example. Thus, the medium may be such a defined and measurable structure carrying or controlling a signal or information, such as a device carrying a bitstream, for example, according to embodiments of the present invention. The media may also be a distributed network, so that the computer readable code is stored/transferred and executed in a distributed fashion. Still further, as only an example, the processing element could include a processor or a computer processor, and processing elements may be distributed and/or included in a single device.

While aspects of the present invention has been particularly shown and described with reference to differing embodiments thereof, it should be understood that these embodiments should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in the remaining embodiments.