Apparatus and method for writing optical inforamation

Optical information writing device and method

<p>The present invention relates to an optical information writing apparatus and method.</p>

<p>When data is written to a write/reproduceable optical disc, with respect to the write waveform as a reference, the write quality A method of maintaining . In order to determine a writing strategy unique to this optical disc, write information to the optical disc using the standard writing strategy (standard WST), reproduce the written information to find the write length of each mark or space, and then use this writing length and the standard writing strategy The write waveform is corrected such that this difference from the theoretical length by</p><p>Conventionally, the relationship between the front and rear end positions of the write signal for trial writing generated based on the write strategy and the average position of the front and rear ends of the reproduction signal read from the written pattern edge is regarded as linear, and There is a way to set the average to 0. 6 is a waveform diagram of a reproduction signal indicating parameters constituting a conventional writing strategy. In Figure 6, x<sb>ij</sb>, y<sb>li</sb>, y<sb>jm</sb>denotes the amount of change from the development setting of the front and rear end positions of the write signals I-mark and j-mark.</p><p>μ<sb>lijm</sb>denotes the average shear position of the phenomenon of the reproduction signal specified by the combination of I-mark, i-space, j-mark, and m-space. d<sb>ij</sb>, c<sb>lij</sb>, b<sb>ijm</sb>, respectively, the amount of change x<sb>ij</sb>, y<sb>li</sb>, y<sb>jm</sb>This is an influence function indicating the influence on the average position of the reproduction signal. r<sb>lijm</sb>denotes the existence probability of a combination of l-mark, i-space, f-mark, and m-space. In order to set the average value of each front and rear end of the reproduced signal to 0, 0 = Σ<sb>lm</sb>r<sb>lijm</sb>(μ<sb>lijm</sb>+d<sb>ij</sb><sb>ij</sb>+c<sb>lij</sb>y<sb>li</sb>+b<sb>ijm</sb>y<sb>jm</sb>) can be obtained by finding the solution</p><p>This method is a method in which the average of the deviation between the read signal and the write signal read for each written pattern is obtained at each signal front end position and the rear end position, and each average value is independently set to 0. Because of this, the scalability is insufficient to limit the adjustable write strategy to the front and rear end positions of each write signal, and the precision of the write quality is limited.</p><p>As another method, in Japanese Patent Laid-Open No. 2007-287229, the system controller 32 uses the test area of the optical disk 10 to write test data for trial with various writing strategies, and reproduces quality of the test data. In order to select the optimal write strategy by evaluating According to the difference between the write power that can be obtained (Pmb) and the write power that can obtain the minimum error rate (Pmb), Hst = AEb<sp>2</sp>+BWe<sp>2</sp>+C (Peb-Pmb)<sp>2</sp>It is described that a write strategy that can calculate the evaluation value Hst by , and obtain the minimum Hst is called an optimal write strategy, and that the same can be applied to jitter.</p><p>This method is a method of selecting the best one by testing a number of writing strategies prepared in advance, reading them, and measuring them. Because of this, more trial writing is required to improve the precision. In addition, if the number of test writes increases, it is necessary to provide a wide area of the optical disk as a test write area necessary for setting a write strategy, and a large amount of measurement and evaluation time is required.</p>

<solutionproblem><p>The present invention relates to an optical information writing device and the same, in which adjustable write strategy parameters are scalable, write quality precision is improved, there is no need to provide a large area of an optical disc, and write strategy parameters can be corrected in a short time. to provide a way.</p></solutionproblem><meansproblemsolution><p>According to an embodiment of the present invention, lines of marks and spaces are formed on the optical writing medium by generating write pulse light according to a predetermined writing strategy and irradiating the generated write pulse light to the optical writing medium to write information. The optical information writing device for writing includes a reproduction signal generating means for reading information written on the optical writing medium according to a standard writing strategy and generating a reproduction signal according to the marks and spaces, and generating a clock based on the reproduction signal. clock generating means; detecting means for detecting the timing of the front and rear ends and the amount of change in the clock generated by the clock generating means at each position before and after each mark at which the value changes in the reproduction signal generated from the reproduction signal generating means; Calculating means for calculating element jitter and element average position of elements classified by a combination of mark length and space length based on and correcting means for correcting the writing strategy to optimize the evaluation function, wherein the correcting means corrects the reference writing strategy by the obtained correction value of the writing strategy to obtain the predetermined writing strategy.</p><p>In an embodiment, the evaluation function adds the square of a function constructed based on the factor jitter and the writing strategy and the power of a function constructed based on the factor average position and the writing strategy, and further, It is characterized in that the calculation of multiplying the existence probability is expressed by summing the results performed for each element.</p><p>In an embodiment, the evaluation function is configured to ignore the elemental jitter when the elemental jitter can be regarded as unchanged and invariant with respect to the correction of the writing strategy, and based on the element average position and the write strategy It is characterized in that it is expressed by summing the results of performing an operation of squaring the constructed function and multiplying it by the element existence probability for each element.</p><p>In an embodiment, the elements classified by the combination of the mark length and the space length are classified into three or more combinations of the mark length and the space length, including before and after.</p><p>In an embodiment, the element jitter and the element average position of the evaluation function are represented as a linear function of the writing strategy.</p><p>In an embodiment, a differential function obtained by differentiating by the writing strategy based on the plurality of amounts of change detected for each of the front and rear end positions by the detection means in the portion expressed by the equation of the evaluation function in the optimization It is characterized in that the reference writing strategy is corrected by the correction value obtained by setting it as 0, and the predetermined writing strategy is obtained.</p><p>In an embodiment, a differential function obtained by differentiating by the writing strategy based on the plurality of amounts of change detected for each of the front and rear end positions by the detection means in the portion expressed by the equation of the evaluation function in the optimization The predetermined writing strategy is obtained by correcting the reference writing strategy based on a correction value obtained by 0 and a correction value obtained by applying a measurement method in a part not expressed by the equation of the evaluation function. do it with</p><p>According to an embodiment of the present invention, by generating write pulse light according to a predetermined writing strategy, and irradiating the generated write pulse light to the optical writing medium, marks and space lines are formed on the optical writing medium to write information. The optical information writing method includes a first step of writing information to the optical writing medium by a writing means according to a standard writing strategy, reading information written on the optical writing medium by the writing means, and according to the marks and spaces A second step of generating a reproduction signal by the reproduction signal means, a third step of generating a clock by a clock generation means based on the reproduction signal, an angle at which a value changes in the reproduction signal generated from the reproduction signal generation means a fourth step of detecting, by means of a detection means, the timing of the front and rear end positions and the amount of change of the clock generated by the clock generating means at each of the front and rear end positions of the mark; A fifth step of calculating, by calculation means, the element jitter and element average position of elements classified as a combination of mark length and space length based on the variation amount, and evaluation based on the element jitter and element average position and writing strategy and a sixth step of constructing a function and correcting the writing strategy by a correction means to optimize the evaluation function.</p></meansproblemsolution><effectiveness><p>According to the present invention, since the write strategy parameters are determined so as to minimize jitter, each parameter of the adjustable write strategy is scalable, the precision of the write quality is improved, and an optimal write strategy based on one write is logically derived, it is not necessary to provide a large area for optimization, and it will be possible to provide an optical information writing apparatus and an optical information writing method capable of correcting write strategy parameters in a short time.</p></effectiveness>

<p>Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those of ordinary skill in the art to which the present invention pertains can easily implement the technical idea of the present invention.</p><p>An optical information writing device according to an embodiment of the present invention writes information to an optical writing medium using a writing signal generated based on a reference writing strategy to obtain a predetermined writing strategy, which is a write parameter unique to the optical writing medium. (or trial writing), reproducing the written (or trial writing) information to obtain a reproduction signal, and then requesting the amount of change in the position of the front and rear end of the reproduction signal with respect to the position before and after the write signal based on the generated clock Then, calculation processing is performed based on the change amount and the evaluation function of the jitter, and a correction amount for obtaining a predetermined writing strategy by correcting the reference writing strategy is determined.</p><p>For this reason, the parameters (write strategy parameters) constituting the writing strategy initially, and the element jitter and element average of elements classified into combinations of marks and spaces, respectively, with respect to the reproduced signal reproduced from the mark space patterns written in plural types of trials. The relationship between the position and the evaluation function that evaluates the jitter of the optical writing medium will be described.</p><p>The positions before and after each write signal constituted from a plurality of types of marks and spaces will be set to correspond to parameters constituting a standard write strategy. In addition, the element jitter and element average position of each element at the front and rear end positions included in the reproduction signal are related to parameters constituting the writing strategy. Furthermore, an evaluation function for correcting the reference writing strategy to obtain a predetermined writing strategy will be expressed based on the element jitter and the element average position and the writing strategy. For this reason, by performing arithmetic processing for optimizing the evaluation function, it becomes possible to obtain a correction value that minimizes jitter inherent in the optical writing medium, and a predetermined writing strategy can be obtained.</p><p>To explain these in more detail, we will describe the evaluation function. The element jitter and element average position of elements included in a reproduction signal reproduced from a plurality of types of written patterns are expressed as linear functions of the write strategy. The jitter evaluation function of the optical writing medium adds the square of a function constructed based on the element jitter and the writing strategy and the square of a function constructed on the basis of the element average position and the writing strategy, further adding to it the element presence probability By summing the result of the operation of multiplying by , for each element, it is expressed by the following equation.</p><p> E=Σr<sb>It's</sb>(σ<sb>It's</sb><sp>2</sp>+μ<sb>It's</sb><sp>2</sp>)</p><p>where E: evaluation function, r<sb>It's</sb> : element existence probability, σ<sb>It's</sb> : element jitter, μ<sb>It's</sb> : The element average position.</p><p>In order to optimize the jitter, the evaluation function E is differentiated by the write strategy parameter based on a plurality of variations detected at each front and rear end by the detection means, and the differential function obtained by differentiating the differential function to 0. The value of the parameter will be requested. The value obtained by this becomes a correction value of each parameter of the write strategy for optimizing the jitter, so that a predetermined write strategy can be obtained by performing correction by the correction value.</p><p>In this optimization, the element jitter of the evaluation function changes little with respect to the correction of the write strategy, and there is often no problem even if it is regarded as invariant. In this case, ignoring element jitter, squaring a function constructed based on the element average position and writing strategy, and further multiplying it by the element existence probability. is expressed in the form</p><p> E=Σr<sb>It's</sb>μ<sb>It's</sb><sp>2</sp></p><p> In this case, since the evaluation function can be simplified, the simplicity of the calculation process will increase and the calculation time will be shortened.</p><p>Next, with respect to an embodiment of jitter optimization by a simplified evaluation function, a case will be described in which three positions of the front and rear ends of the write signal are used as write strategy parameters, including before and after.</p><p>2 is a correlation diagram showing a relationship between each signal and a written writing pattern during trial writing according to the present invention. Referring to FIG. 2 , a signal for writing a plurality of types of marks according to a reference writing strategy, for example, an IT mark, an iT space, a jT mark, and a mT space, will be generated. Write patterns Pl and Pj are formed on the write medium by the write pulse light generated based on the write signal. Subsequently, the writing pattern Pl and the pattern Pj are read to generate a reproduction signal. Here, the reproduction signal is generalized to describe arbitrary marks and spaces in common, and is described by f-mark and j-mark indicating the mark portion and i-space and m-space indicating the space portion.</p><p>The average shear position of the phenomenon of the reproduction signal (μ<sb>lijm</sb>) is the shear position (e) of the written pattern (Pj) specified by a combination of l-mark, i-space, j-mark, and m-space<sb>lijm</sb>) is the average value of the previous position of the read and reproduced reproduction signal. x<sb>ij</sb>, y<sb>li</sb>, and y<sb>jm</sb>is the amount of change from the current setting of the write signal specified in l-mark and i-space, i-space and j-mark, and j-mark and m-space, respectively. influence coefficient (d<sb>ij</sb>, c<sb>lij</sb>, b<sb>ijm</sb>) is the amount of change (x<sb>ij</sb>, y<sb>li</sb>, y<sb>jm</sb>) is an influence coefficient indicating an influence on the average position of the reproduction signal. r<sb>lijm</sb>denotes the existence probability of a combination of l-mark, i-space, j-mark, and m-space. These influence coefficients and existence probability can be calculated|required in advance by methods, such as an experiment, and can also be extracted more precisely by writing a small number of trials.</p><p>The amount of change that becomes a parameter of these three write strategies (x<sb>ij</sb>, y<sb>li</sb>, and, y<sb>jm</sb>The evaluation function by ) is expressed as follows. </p><p>E=Σ<sb>lijm</sb>{r<sb>lijm</sb>(μ<sb>lijm</sb>+d<sb>ij</sb>x<sb>ij</sb>+c<sb>lij</sb>y<sb>li</sb>+b<sb>ijm</sb>y<sb>jm</sb>)<sp>2</sp>+r´<sb>lijm</sb>(μ'<sb>lijm</sb>+d'<sb>ij</sb>y<sb>ij</sb>+c'<sb>lij</sb>x<sb>li</sb>+b'<sb>ijm</sb>x<sb>jm</sb>)<sp>2</sp>}</p><p>Here, the symbol (´) indicates all quantities related to l-space, i-mark, j-space, and m-mark in which the polarities of the mark and the space are inverted.</p><p>Then, for optimization, an optimization method will be used. This is the amount of change (x) of the evaluation function (E)<sb>ij</sb>) as the derivative, it is sufficient if the following expression is satisfied.</p><p>0 = Σ<sb>lm</sb>(r<sb>lijm</sb>d<sb>ij</sb>μ<sb>lijm</sb>+r´<sb>ijlm</sb>c'<sb>ijl</sb>μ´<sb>ijml</sb>+r´<sb>lmij</sb>b´m<sb>ij</sb>μ´<sb>lmij</sb>)+Σ<sb>lm</sb>(r<sb>lijm</sb>d2<sb>ij</sb>+r´<sb>ijlm</sb>c´2<sb>ij</sb>+r´<sb>lmij</sb>b´2m<sb>ij</sb><sb>ij</sb>+Σ<sb>lm</sb>(r´<sb>ijlm</sb>c'<sb>ij</sb>b´<sb>jlm</sb>+r´<sb>lmij</sb>c'<sb>lmi</sb>b´m<sb>ij</sb><sb>lm</sb>+Σ<sb>lm</sb>r<sb>lijm</sb>d<sb>ij</sb>c<sb>lij</sb>y<sb>li</sb>+Σ<sb>lm</sb>r´<sb>lmij</sb>d´mb´<sb>mij</sb>y<sb>mi</sb>+Σ<sb>lm</sb>r<sb>lijm</sb>d<sb>ij</sb>b<sb>ijm</sb>y<sb>jm</sb>+Σ<sb>lm</sb>r´<sb>ijlm</sb>d´<sb>jl</sb>c'<sb>ijl</sb>y<sb>jl</sb></p><p>This equation is a linear equation with the writing strategy parameter as a variable. Also, y<sb>ij</sb>As the derivative of , the same expression will be satisfied. In other words, each<sb>ij</sb>Since the linear equations for is satisfied, as a whole, it will be a system of linear equations.</p><p>The correction value of each parameter of the writing strategy is calculated by substituting the value of the average shear position of the phenomenon obtained by each change amount of the reproduced signal of trial writing, the influence coefficient and the existence probability at that time, into this simultaneous linear equation, and is calculated. can</p><p>Fig. 3 is a matrix diagram showing a specific example in which the system of linear equations obtained by substituting a matrix is expressed. By solving the simultaneous equations with the relation between the coefficient matrix and the integer column in the determinant, the amount of the writing strategy parameter to be corrected is obtained. In addition, this simultaneous equation can be solved by various methods, such as a well-known sweep out method. By generating a write pulse light using a predetermined write strategy obtained by this correction, and irradiating the generated write pulse light to an optical writing medium, it is possible to write information by forming lines of marks and spaces with minimal jitter. Therefore, the precision of the writing quality will be improved compared to the prior art.</p><p>Although the case where the trial writing area in the optical disc 1 is used has been described in FIG. 2, it may be obtained from a reproduction signal of a mark written in a normal writing area. The write strategy parameters that can be used for this evaluation function are not limited to the positions before and after the write signal.</p><p>4 is a write signal waveform diagram illustrating a write signal to which overdrive is added. This shows a write signal when a write pattern is formed by a write signal obtained by adding a write strategy parameter indicating the width of the overdrive portion to the write strategy parameter of the first embodiment.</p><p>v<sb>ij</sb>denotes the amount of change from the current setting of the mark shear overdrive specified by i-space and j-mark, w<sb>li</sb>represents the amount of change from the current setting of the trailing end overdrive of the mark specified by l-mark and i-space, w<sb>jm</sb>denotes the amount of change from the current setting of the trailing end overdrive of the mark specified by j-mark and m-space.</p><p>influence coefficient (e<sb>ij</sb>, g<sb>lij</sb>, f<sb>ijm</sb>) is the average position (μ) of the position change of the overdrive<sb>lijm</sb>) is a coefficient for accepting the effect on the evaluation function. </p><p>As in the case of FIG. 2, this evaluation function is shown as follows. </p><p>E=Σ<sb>lijm</sb>r<sb>lijm</sb>(μ<sb>lijm</sb>+d<sb>ij</sb><sb>ij</sb>+c<sb>lij</sb>y<sb>li</sb>+b<sb>ijm</sb>y<sb>jm</sb>+e<sb>ij</sb><sb>ij</sb> +g<sb>lij</sb><sb>li</sb>+f<sb>ijm</sb>w<sb>jm</sb>)<sp>2</sp></p><p>+Σ<sb>lijm</sb>r´<sb>lijm</sb>(μ'<sb>lijm</sb>+d'<sb>ij</sb>y<sb>ij</sb>+c'<sb>lij</sb><sb>li</sb>+b'<sb>ijm</sb>x<sb>jm</sb>+e´<sb>ij</sb><sb>ij</sb>+g'<sb>lij</sb><sb>li</sb>+f'<sb>ijm</sb>w<sb>jm</sb>)<sp>2</sp></p><p>Here, the symbol (´) indicates all quantities related to the trailing end of j-mak. </p><p>By optimizing this evaluation function as in the case of FIG. 2, the value of the writing strategy parameter to be corrected is obtained. This makes it possible to obtain a predetermined write strategy that further improves the precision of the write quality. In addition, as the write strategy parameter, not only the time axis direction but also the parameter of the power direction can be used. In other words, it becomes possible to collectively handle all the write strategy parameters for the horizontal axis and the vertical axis in the same format, and to set the best writing strategy.</p><p>In addition, when some writing strategy parameters such as power level cannot be clearly formulated, the evaluation function is divided into a formalized part (1st term) and an unmodified (2nd term) as shown below. Write down</p><p> E=Σr<sb>It's</sb> (σ<sb>It's</sb><sp>2</sp>+μ<sb>It's</sb><sp>2</sp>)+Σr<sb>j</sb>(σ<sb>j</sb><sp>2</sp>+μ<sb>j</sb><sp>2</sp>)</p><p>In the first term, a correction value is obtained by a net calculation by the method shown in FIG. 2 or 4, and in the second term, a correction value can be requested by applying a well-known gradient method or the like as an actual measurement method. This makes it possible to set an accurate writing strategy relatively easily, even in the case of including items that are difficult to formulate.</p><p>As described above, writing that optimizes jitter by obtaining the average front-end position of the element average position and the front-end position of the element jitter, or only the average front-end position of the element average position, from the reproduced signal from which the pattern of the written mark is read strategy can be obtained.</p><p>As a method of optimization, when an equation is written linearly, the simplex method or the dotted method is used, and in the case of nonlinearity, the gradient method, GA, EDA, etc. are used to optimize. can do. Further, in the optimization, a physical meaning such as limiting the movement range of the edge may be added to the constraint condition, or a part of combinations of mark spaces may be integrated. Further, in the evaluation function, it is also possible to give weight to the evaluation function as shown below from important terms and improvement of the stability of the solution.</p><p> E=Σr(α<sb>It's</sb>σ<sb>It's</sb><sp>2</sp>+β<sb>It's</sb>μ<sb>It's</sb><sp>2</sp>)</p><p>α<sb>It's</sb>, β<sb>It's </sb>: weight coefficient</p><p>Fig. 1 is a block diagram showing the configuration of an optical information writing apparatus of the present invention. Referring to FIG. 1 , an optical information writing apparatus 100 includes an optical disc 1 , an optical pickup 2 , a head amplifier 3 , a data decoder (reproduction signal generating means, clock generating means) 4 , and a difference detecting unit. (detection unit) 5, control unit (write unit) 6, write strategy setting unit (correction unit) 7, storage unit 8, write pulse train correction unit 9, data encoder 10 , a laser driving unit 11 , and an input/output unit 12 .</p><p>Fig. 5 is a flowchart showing the sequence of processing in the trial writing operation of the present invention. 1 and 5, in the case of the correction operation of the write strategy by trial writing, the preset positions of the front and rear ends of the write signal are stored in the storage unit 8 as parameters constituting the write strategy as a reference, The control unit 6 will read the parameters related to the reference writing strategy from the storage unit 8 and set it in the write pulse train correction unit 9 via the data encoder 10 . The write pulse train compensator 9 generates a write pulse train based on the set parameters and outputs the write pulse train to the laser driver 11 . The laser driver 11 generates a pulse signal for driving a laser diode according to the input write pulse train, and supplies it to a semiconductor laser (not shown) in the optical pickup 2 to generate write pulse light, Mark and space will be written in the trial writing area (S50).</p><p>When writing of the mark and space is finished, the control unit 6 will move the optical pickup 2 to the writing track in the trial writing area, and perform reproduction of information. The signal read by the optical pickup 2 will be input to the data decoder 4 through the head amplifier 3 . The data decoder 4 will generate a binarized value signal based on this input signal, further extract a clock signal from this binarized value signal, and output these binarized value signals and clock signals to the difference detection unit 5 ( S52, S54). The difference detection unit 5 detects a difference value (amount of change) from the front and rear ends of the input binarized value signal corresponding to each mark such as 3T, 4T, 5T, etc. indicated by the control unit 6 and the front and rear ends of the clock signal, and write strategy setting unit ( 7) will be output (S56).</p><p>The writing strategy setting unit 7 reads from the storage unit 8 via the control unit 6, follows a predetermined processing sequence, differentiates the expression of the evaluation function shown in the description of Fig. 2 or Fig. 4, and inputs By making the differential function 0 based on the changed amount, the write strategy parameter is corrected by the obtained correction value, and a predetermined writing strategy is obtained. This predetermined write strategy will be stored in the storage unit 8 via the control unit 6 (S58).</p><p>In the case of a normal write operation, when write data is input to the input/output unit 12 from an external computer or the like, the control unit 6 outputs the data to the data encoder 10, and the data encoder 10 outputs the data. will be encoded into a write signal and output to the write pulse train correction unit 9 . The control unit 6 will further read the predetermined write strategy from the storage unit 8 and output it to the write strategy setting unit 7 . The write strategy setting unit 7 may output a parameter of a predetermined write strategy to the write pulse train correcting unit 9 . The write pulse train correcting unit 9 corrects the front and rear end positions of the input signal for writing based on a parameter of a predetermined write strategy, and outputs it to the laser driving unit 11 . The laser driving unit 11 generates a pulse signal for driving a laser diode according to the input write pulse train, and supplies it to a semiconductor laser (not shown) in the optical pickup 2 to generate write pulse light, and write pulse light in the optical disk 1 . In the area, the writing of marks and spaces will be performed.</p><p>In the case of a normal read operation, the control unit 6 will move the optical pickup 2 to a write track in the write area, and perform reproduction of information. The signal read by the optical pickup 2 will be input to the data decoder 4 with the head amplifier 3 interposed therebetween. The data decoder 4 will decode this input signal into the original input data and output it to the input/output unit 12 . The input/output unit 12 is controlled by the control unit 6 to output this inputted data to an external computer or the like.</p><p>As described above, in order to be able to determine the write strategy parameters that minimize jitter, the scalability of the parameters constituting the adjustable write strategy will be enriched, and the precision of the write quality will be improved. In addition, since an optimal write strategy is logically derived based on a set of writes, it is not necessary to provide a large area of the optical disc for optimization, and correction of write strategy parameters becomes possible in a short time. For this reason, the present invention It will be possible to provide an optical information writing device and an optical information writing method to which</p><p>Meanwhile, although specific embodiments have been described in the detailed description of the present invention, various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments and should be defined by the claims and equivalents of the present invention as well as the claims to be described later.</p>