Patent Application
20090274024
The present invention relates to an optical-irradiation-power calibration method and an information recording/reproducing unit and, more particularly, to a method for calibrating an optical irradiation power used upon irradiating a laser beam onto a write-once optical information recording medium to record a pattern train including marks and spaces, as well as an information recording/reproducing unit using such an optical-irradiation-power calibration method.
Optical discs for writing/reading data thereon by using a laser beam are widely used. The optical disc has a higher storage density and is capable of recording a large amount of data. Due to operation in a noncontact state, the optical disc has been experiencing a development toward a higher-speed access and a larger-capacity memory device. The optical discs are classified into a read-only type that allows read only, a write-once type that allows the user side to record data only once, and a rewritable type that allows the user side to repeatedly record data. The read-only type is generally used as music CDs and laser discs on the market, and a variety of types are used as external memories for computers or storage devices for documents and images. For the read-only type, a reproduced signal is detected using the change of reflected light quantity from concave-convex pits formed on the optical disc. For the write-once type, a reproduced signal is detected using change of the amount of reflected light from small-size pits formed on the optical disc.
Examples of the write-once optical disc distributed on the market include CD-R, DVD-R, and DVD+R, most of which include a recording member containing organic pigment as a base. As the light source used for performing recording/reproducing on the optical disc, a semiconductor laser having a wavelength between around 780 nm and around 650 nm is used. The optical disc including organic pigment as the base includes an organic-pigment member that has an absorption maximum on a wavelength side shorter than the wavelength of the recording/reproducing-use laser beam, and thus has a so-called high-to-low characteristic wherein the optical reflectance at the recorded mark section formed by laser beam irradiation is lower than the optical reflectance prior to the laser beam irradiation. Formation of the mark section uses a transform (shape distortion) of a resin substrate that is caused as a result of a negative pressure due to decomposition of the organic pigment generated by optical irradiation of the resin substrate to heat the same up to a temperature hither than the transition temperature of the resin substrate.
As the optical discs for achieving a higher recording density therein, there are disc standards such as HD DVD and BD (Blu-Ray). For these next-generation optical discs, a laser beam having a wavelength of around 400 nm to around 410 nm (short-wavelength laser) is used during the recording and reproduction. The write-once discs, which are now under development for use together with the short-wavelength laser, include recording films that are roughly categorized into one using an inorganic material member and another using an organic-pigment member. Among them, the write-once disc using the pigment member is described in Patent Publication-1. The pigment member described in Patent Publication-1 has a maximum wavelength-absorption range which is shifted from the recording wavelength (405 nm) toward the longer wavelength side, and the absorption is not distinguished in the recording wavelength range, and has a significant amount of absorption within the recording wavelength range. The optical disc including an organic-pigment member has a low-to-high characteristic wherein the reflectance of the recorded mark section formed by irradiation of the laser beam is higher than the reflectance prior to the laser beam irradiation.
The rewritable optical discs include CD-RW, DVD-RW, DVD-+RW, DVD-RAM, etc., which are phase-change discs. In addition to them, there is also a magneto-optical disc referred to as MO. As the phase-change disc, HD DVD-RW having a higher capacity is already standardized. These optical discs, referred to as RW or RAM, are configured as the media that allow a direct overwriting (hereinafter simply referred to also as overwriting) i.e., recording while erasing. These optical discs have the advantage of allowing the direct for overwriting, whereby rewrite of the recorded data does not necessitate a two-time operation, i.e., recording of data in the next rotation after erasure of data, and allows a single operation for overwriting. In the direct overwriting medium, upon recording of data, switching of irradiation is performed between the recording power that is related to recording and the erasing power that is related to erasing, depending on the mark and space for recording.
A recording waveform, which configures the recording-use waveform shape, will be described hereinafter.
Patent Publication-2 describes that the irradiation power for the space section during the recording is allowed to have a bias power (second intensity) in order for compensating a deficiency in calorie supply of the recording power during a high-speed rotation of the disc. It is also described that the intensity (power) thereof is preferably 5 to 15% of the peak power (first intensity). Patent Publications-3 to -6 describe that the recording waveform used on a next-generation optical medium having a higher density includes a constant recording power and two different bias powers, i.e., bias powers-1 and -2.
The conventional technique for power calibration will be described hereinafter. As to the recording power, the optical disc drive uses a power calibration area (PCA), in a write-once DVD-R for example, formed in a part of optical disc to perform an optimum power control (OPC) at a suitable timing. In addition, the HD DVD-R or -RW includes a drive test zone that may be arbitrarily used by the optical disc drive, whereby the optical disc drive perfonns calibration of a variety of parameters including the recording power by using this area.
Patent Publication-7 and Patent Publication-8 describe a technique for calibrating the erasing power on the rewritable optical disc. Patent Publication-7 includes recording a 11T signal by using a power equal to or above the recording power determined by a gamma technique, irradiating a laser beam having a plurality of erasing power levels while changing the DC erasing power (direct-current light), and measuring the residual signal amplitude of the signal to determine an optimum erasing power. Patent Publication-8 includes continuously irradiating a laser beam having a plurality of erasing power levels while stepwise changing the DC erasing power (direct-current light) by a specific amount to thereby erase the old data (existing data) in a trial way, reproducing the old data section subjected to the trial erasure, and determining the erasing power irradiated onto the section that allows the reproduced signal to have a minimum noise level (amplitude), as the optimum erasing power. Patent Publication-8 also describes a technique for determining the erasing power for a recording power, which is obtained by the OPC technique, based on a ratio, ε (=erasing power/recording power), obtained by an experiment.
In the power calibration, the jitter and error rate of a recording/reproduced signal is used as the performance index thereof to determine the recording power etc. For the power calibration, in addition thereto, there are other techniques, such as a beta technique that inspects asymmetry from the reproduced amplitude of a long mark and the reproduced amplitude of a short mark to obtain a β-value for use as the performance index, and a gamma technique that judges the state based on the degree of the saturation of amplitude of the recorded mark. The beta technique obtains in advance a correlation between the β value and the error amount, for example, for the disc with respect to the drive, and uses the β-value as the performance index. Although a β-value of around zero is considered preferable, the β-value of zero does not necessarily provide the optimum performance, and a β-value deviated from zero, for example, +5% or −7%, may be preferable in some cases.
For the write-once disc, the β-value largely changes depending on the power, is handled with ease as the performance index, and thus is frequently used. The absolute value of β-value has a different meaning (performance) depending on the correlation with respect to the error amount.
There is a PRSNR known as a performance index used for an optical disc having a higher density. The PRSNR is a signal-quality evaluation index that replaces the jitter, and now used in a HD DVD family. The PRSNR is an SNR (signal noise ratio) in PRML (partial-response maximum likelihood), and it is considered that a higher value thereof means a higher signal quality. The detail of PRSNR including conversion thereof into an error rate is described in a Non-Patent Literature-1. It is known that the target value for the performance in the PRSNR is required to be 15 or above. As the performance index, the jitter obtained by a limit equalizer technique, an SAM (sequenced amplitude margin) and the index using the SAM, in addition to the above, may be used in some cases depending on the target storage density, circuit configuration and drive configuration. Non-Patent Literature-2 describes the technique related to the SAM.
Patent Publication-1: JP-2002-187360A
Patent Publication-2: JP-2000-187842A
Patent Publication-3: JP-2005-288972A
Patent Publication-4: JP-2005-293772A
Patent Publication-5: JP-2005-293773A
Patent Publication-6: JP-2005-297407A
Patent Publication-7: JP-2003-228847A
Patent Publication-8: JP-2004-273074A
Non-Patent Literature-1: Japanese Journal of Applied Physics Vol.43, No.7B, 2004, pp. 4859-4862,“Signal-to-Noise Ratio in a PRML Detection”, S.OHKUBO et al.
Non-Patent Literature-2; “Signal Reproducing Technique in a High-Density Optical Disc Drive ”, p.25-30 Okumura et al., Sharp Technical Report, No. 90, December, 2004
Recording and reproduction was performed on a conventional write-once disc medium by using a laser beam having a wavelength range longer than around 650 nm, and revealed that it is unnecessary to use a power corresponding to the space in the write-once optical disc medium including an organic pigment in the recording film. This results from the fact that the write-once disc medium does not inherently require the overwriting. It is to be noted that the fact that the overwriting is impossible on the write-once disc medium also provides the advantage that the write-once disc is free from falsification of data. On the other hand, a medium for which a recording-use optical power including a recording power and a bias power corresponding to the mark and space, respectively, is needed has been developed, such as a write-once disc which includes a recording film configured by an organic-pigment member, for which recording/reproduction is performed using a short-wavelength laser developed recently, and for which the mark is formed by a photochemical reaction or photo-thermal-chemical reaction.
The Patent Publications and Non-Patent Literatures as described above do not describe a power calibration technique for the write-once optical disc medium that requires the recording power and bias power corresponding to tie mark and space, respectively, especially as to the calibration procedure thereof. Such an optical disc medium generally involves the problem that calibration of only the recording power during the power calibration cannot necessarily derive the maximum medium performance. In addition, the fact that the maximum medium performance cannot be derived causes a reduction in the margin, or leads to a reduction in the product yield, thereby providing serious problems. Further, the optical disc medium and optical disc drive for which recording and reproduction is performed using a short wavelength laser developed in these days require a higher degree of accuracy in the parameters, and in particular, the recording parameters used during the data recording must be calibrated more accurately than ever to an optimum value. Thus, there occurs a situation wherein the number of targets for calibration or parameters has increased to thereby require a larger time length in the calibration. It may be considered that all the combinations of recording power and bias power are used for the recording, to thereby calibrate the parameters; however, this increases the calibration time length and consumes a larger calibration area, whereby a suitable solution is not necessarily provided.
The bias power described in Patent Publication-2 is a supplementary power that supplements insufficient heat of the peak power generated due to a higher-speed rotation. Then, use of the procedure described in Patent Publication-2 may be such that calibration of the peak (recording or first intensity) power calibrates the recording power by using the β-value and the bias (second intensity) power equal to around the reproducing power or 5 to 15% of the peak power, and the OPC is again performed using the bias power corresponding to the recording power obtained in advance. However, since the β-value is not an index representing the performance itself, there is a problem in that calibration of the recording-use power by using the β-value as the index cannot necessarily provide an optimum parameter at a higher speed and with a higher degree of accuracy. In particular, in the case of a disc wherein the β-value itself used as the target power selection is unknown, that is, if the β-value is used for a disc wherein the correlation between the β-value and the error performance is unknown, an increased error incurred thereby negates meaning of the β-value itself as the measure, to thereby prevent an accurate calibration, or causes a situation of incapability of calibration. In determination of the power corresponding to the space section, the problem cannot be solved by using a technique of determining the power corresponding to the space section by erasing the mark already recorded, because the disk is the write-once medium.
It is described in the above description, as to the measure of evaluation for determining the power, that use of the β technique cannot necessarily determine the recording-use power with a higher degree of accuracy. There is also a technique wherein determination of the recording power uses the beta technique, gamma technique, or a technique of using the number of errors, and determination of the erasing power uses the residual signal amplitude of a recorded signal, in consideration that the recording/erasing power includes a plurality of recording powers, wherein the erasing power is another recording power (bias power). However, in this case, a complicated processing is needed, to thereby incur the problem of increase in the scale of detection hardware or the number of control programs (firmware programs) that operate the drive.
As described heretofore, there is a demand for development of the technique for calibrating the recording-use optical irradiation power that achieves a higher effectiveness with a higher degree of accuracy and certainty.
It is an object of the present invention to provide a recording-use optical-irradiation-power calibration method that is capable of calibrating the recording-use optical irradiation power with a higher degree of certainty, while reducing the time length of calibrating the recording-use optical irradiation power and reducing the calibration area used therefor. It is another object of the present invention to provide an optical information recording/reproducing unit that performs calibration of the optical irradiation power using such a method.
The present invention provides, in a first aspect, a method for calibrating an optical irradiation power in an optical information recording/reproducing unit that performs recording on a write-once recording medium, wherein which a mark is formed by optical beam irradiation, including the steps of recording a specific pattern train in a specific area on the recording medium while stepwise-changing a recording power with a bias power being fixed; reproducing the pattern train recorded in the recording step to measure a reproduced-signal quality; selecting, based on the measured reproduced-signal quality, a single recording power from among recording powers that are stepwise changed therebetween; selecting a bias power by using the selected recording power; and forming a mark by irradiating the selected recording power and the selected bias power.
The present invention provides, in a second aspect, an information recording/reproducing unit that records/reproduces data on a write-once recording medium, wherein a mark is formed by optical beam irradiation, including: a parameter calibration unit (21) that determines a recording power and a bias power of a laser beam that irradiates the recording medium upon performing recording on the recording medium (50), wherein the parameter calibration unit (21): includes a reproduced-signal quality measurement section that measures a reproduced-signal quality; selects a single recording power from among recording powers that are stepwise changed therebetween based on a reproduced-signal quality of a specific pattern train, which is recorded in a specific recording area while stepwise-changing recording power with the bias power being fixed constant, the reproduced-signal quality being measured by the parameter calibration unit; selects the bias power based on the selected recording power; and determines the selected recording power and the selected bias power as an optical irradiation power and a bias power, respectively, upon recording a mark.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.
Hereinafter, the investigation performed before accomplishment of the present invention will be described, prior to description of exemplified embodiment of the present invention. In the following investigation, the optical head used therein was one having a
LD wavelength of 405 nm, and a NA (numerical aperture) of 0.65. The optical disc used therein was one including an in-groove-format-use guide groove provided on a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm. The density of data recorded is such that the bit pitch is selected at 0.153 μm and the track pitch is selected at 0.4 μm. The recording film of the optical disc used therein was one including a short-wavelength-use organic pigment. This is the type allowing the recording only once.
The depression on the upper-side mark section shown in
With reference to
The above situation will be described using the following simulation model.
A case will be considered here wherein the recording is performed using two recording powers Pw1 and Pw2 by changing therebetween the recording power Pw, with the bias power Pb being constant.
Next, a case is considered wherein the bias power is changed between Pb0 and Pb2 with the recording power being fixed at Pw1.
In a system using the PRML in which the amplitude information is important, the dominating factor of the performance is the amplitude level determined by the mark size. The effect of the bias power is a recording-mark shaping effect in which the bias power shapes the mark, and scarcely has an influence on determination of the mark size. Thus, it can be construed that the effect of the bias power is a side effect that suppresses the range of variation in the amplitude level by the mark shaping, thereby stabilizing the mark shape to improve the signal quality.
As described heretofore, it may be concluded in the combination of the recording power and bias power, even if the bias power is roughly selected, that the recording power (peak power) mainly determines the mark size (length), whereas the bias power is not the factor that significantly changes the mark size. From this, the present inventors have come to the findings that the maximum performance can be obtained at a higher speed with a higher degree of certainty by adopting the calibrating procedure of first determining the optimum recording power and thereafter determining the mark-shaping power matched with the recording power, i.e., matched with the mark shape formed by the recording power.
In addition, the above calibration procedure uses the reproduced-signal quality, such as the PRSNR, having a sense of the performance index in the absolute value thereof, thereby detecting the optimum condition with a higher degree of accuracy. A trial calibration was performed wherein the β-value was used as the performance index, and the recording power Pw was selected for the selection target of the β-value, i.e., β-value=0. The recording power Pw providing the β-value=0 assumed different values depending on the bias power, and thus the β-value was deviated depending on the setting of the bias power, whereby calibration of the recording power Pw and bias power Pb in this order could not lead to the optimum condition.
Even the use of PRSNR could not lead to the true optimum condition so long as the order of calibration was reversed, i.e., so long as the order of calibration was such that the bias power Pb was first determined, followed by determining the recording power Pw based on the determined bias power Pb. This is attributable to the fact that the optimum bias power Pb is deviated by the recording power Pw if the power is selected based on the measure of PRSNR. More specifically, finding of the optimum recording power when the bias power Pb is deviated, if employed, does not necessarily provide the PRSNR exhibiting the maximum performance, whereby the optimum recording power cannot be obtained. Thus, even if the optimum condition may be found, a plurality of retrial operations will be needed. The fact that the maximum performance owned by the medium cannot be derived, or that a longer time length is needed for the calibration to obtain the optimum performance is the fatal defect of the drive.
There is also a measure that raises the power at the front edge of the recording waveform without using the bias power. However, it was confirmed that even the use of this measure disturbs the waveform shape of the space section due to diffusion of the heat of the front edge toward a preceding space section (non-mark section), and that the overall performance is difficult to improve and a simple calibration cannot be obtained. Further, although the conventional medium has a strong thermal interference and thus the formation of mark is mainly to change the shape, it is probable that the medium including the short-wavelength-use organic pigment is of a reaction type that uses a photochemical reaction or photo-thermal-chemical reaction. It was confirmed that the validity of the present invention is particularly higher in the medium wherein the optical reflectance of the mark section formed by irradiation of the optical beam is higher than the optical reflectance prior to the laser beam irradiation.
Hereinafter, exemplary embodiment of the present invention will be described with reference to the drawings.
The spindle drive system 23 drives the optical disc for rotation during performing recording/reproducing on the optical disc 50. The LD 14 emits the light that is incident onto the optical disc 50. The light emitted from the LD 14 is reflected by the beam splitter 13, which reflects the light from the LD 14 and passes therethrough the reflected light from the optical disc 50, and advances toward the objective lens 12. The objective lens 12 focuses the light emitted from the LD 14 onto the information recording surface of the optical disc. The reflected light from the optical disc 50 is incident onto the beam splitter 13 via the objective lens 12, passes through the beam splitter 13, and is detected by the photodector 15. The photodector 15 outputs a signal corresponding to the received, reflected light toward the RF circuit 16.
The RF circuit 16 performs a filtering processing etc. with respect to the input signal The demodulator 17 demodulates the signal input thereto via the RF circuit 16. The modulator 19 modulates the recording signal. The LD driver 20 drives the LD 14. The servo controller 22 controls a servo signal and performs a servo control including a tilt control and an astigmatismus control. The system controller 18 controls the entire device. The parameter calibration unit 21 performs parameter calibration of the power etc. in the recording condition. The parameter calibration unit 21 performs judgment of the reproduced-signal performance (reproduced-signal quality). PRSNR or error rate is used for the reproduced-signal quality. The RF circuit 16 has a function as a reproduced-signal-quality unit, and takes charge of calculation of the PRSNR or error rate. In addition thereto, the optical information recording/reproducing unit 10 includes a temperature detecting unit not illustrated.
Subsequently, the parameter calibration unit 21 generates a plurality of recording conditions including stepwise-changed recording powers. The system controller 18 performs recording in the unrecorded area of the optical disc 50 under the plurality of recording conditions including different recording powers generated by the parameter calibration unit 21. In step B120, the recording is performed at the recording powers that are varied within a range of around ±10% from the central value, that is an average recording power of the powers obtained in advance by using calibration in an experiment etc. The recording powers are varied stepwise at a 0.5-mW step, for example. The bias power is fixed at a bias power that is set in step B110. The central value of the recording power may be determined using information of the power read from the optical disc 50. In this case, it happens often that the power, which is prepared by the disc manufacturer, is not the optimum power. However, this information is more advantageous compared to the case of absence of such information, and may be used as the initial central power for the next finding.
If needed information is not obtained in advance, the maximum emitting power of the LD used in the device for recording and the power margin may be estimated so as to obtain the central value of the recording powers. In this case, if the maximum emitting power used for recording in the device is 12 mW, for example, the part of margin therein is estimated at ±20%, revealing that the initial specific recording power is 10 mW. If the specific bias power determined in advance is set at 20 to 40% of the recording power, a power is obtained using 30% which is a median value between 20% and 40% of the recording power, and thus the bias power is selected at this stage at 3.0 mW for setting.
The system controller 18 reproduces the area recorded in step B120 by using the optical head 11, RF circuit 16, demodulator 17, etc. (step B130). The RF circuit 16 measures the reproduced-signal quality corresponding to the area recorded by each recording power (step B140), and feeds the information of reproduced-signal quality to the parameter calibration unit 21. The parameter calibration unit 21 judges the received reproduced-signal quality (step B150), and determines the recording power used for recording under the condition that provided the best reproduced-signal quality as the optimum recording power (step B160).
Back to
The system controller 18 performs recording,. under each of a variety of recording conditions created by the parameter calibration unit 21, onto the unrecorded area of the optical disc 50 (step C120). In step C120, the recording is performed using the bias power that is varied within a range of ±25% from the central value of the average bias power obtained in advance by calibration in an experiment etc, for example. The bias power is varied stepwise in a 0.5-mW step, for example. The central value of the bias power may be determined using information of the power read from the optical disc 50.
The system controller 18 reproduces the area recorded in step C120 by using the optical head 11, RF circuit 16, demodulator 17, etc. (step C130). The RF circuit 16 measures the reproduced-signal quality corresponding to the area recorded using each bias power (step C140), and feeds the information of reproduced-signal quality to the parameter calibration unit 21. The parameter calibration unit 21 judges the received reproduced-signal quality (step C150), and determines tile bias power used for recording under the condition that provided the best reproduced-signal quality, as the optimum bias power (step C160).
Back to
In the present exemplary embodiment, determination of the recording-use optical irradiation power along the above procedure provides a high-speed and accurate calibration of the optical irradiation power during recording using the optical beam irradiation onto the write-once medium for which the recorded mark is formed by optical beam irradiation. This is because the optimum recording power is determined at a high speed in a simple way without depending on the bias power that relates to shaping of the recorded mark, and the bias power (waveform shaping power) matched with the recorded mark formed by the optimum recording power is determined as the optimum bias power. Therefore, as compared to the case where the calibration is performed by recording and reproducing using all the combinations of powers, the calibration time length upon calibrating the power relating to the recording can be drastically reduced. In addition, this leads to the advantage of suppression of the calibration area to be consumed.
In the present exemplary embodiment, it is not needed to perform a complicated processing such as using the target value corresponding to each type of the powers, whereby a variety of device resources can be reduced to thereby reduce the cost thereof. This is because the SNR (PRSNR) or error rate is used as the unified evaluation index during calibration of both the recording power and bias power. In addition, in consideration of the current situation wherein an explosive increase of the number of disc manufactures has arisen, as a result causes appearance of a larger number of so-called unknown discs, the source of which is unknown, and thus causes the device not to catch up with the discs, it is inevitable to calibrate the parameters relating to the performance. As the performance index therein, use of the PRSNR or error rate having a sense of performance index in the absolute value thereof provides the advantage of providing a capability of handling a variety of media, improving the user's convenience and assuring a higher reliability as compared to the target that necessitates an advance calibration corresponding to the performance to some extent.
Hereinafter, description will be provided using Examples. In Example-1, an optical head having a LD wavelength of 405 nm and a NA (numerical aperture) of 0.65 was used as the optical head 11 (
The recording condition was calibrated along the procedure shown in
In step B140, the recorded area was reproduced, to measure the reproduced-signal quality for each recording condition.
From the above, a combination of the recording power Pw=11 mW and bias power Pb=4 mW was determined as the recording-use recording condition. Comparing the reproduced-signal quality in
Next, Example-2 will be described. The basic configuration of Example-2 is similar to that of Example-1, and the content of processing thereof for determining the bias power (in step C100 of
Calibration of the recording condition was performed using the optical information recording/reproducing unit 10 having a configurational similar to that of Example-1. First, the optical head 11 (
After determining the recording power, the bias power was determined. Determination of the bias power used the conversion table shown in
Example-3 will be described. The basic configuration of Example-3 is similar to that of Example-1, and Example-3 is different from Example-1 in that medium identification is performed prior to distinguishing the unrecorded area (in step A100 of
In step A10, identification of the optical disc 50 set is performed with respect to what kind of format the disc uses, which manufacturer the disc belongs to and so on. In addition, if it is judged that the disc is a recordable one, judgment is performed as to whether the disc is a low-to-high disc (LH medium) wherein reflectance of the mark is raised by recording of the mark, or a high-to-low disc (HL medium) wherein the reflectance is lowered by recording of the mark. In addition thereto, information of the number of recording films etc. is read from the optical disc 50, and then information of the power is read, and such information is set in the system controller 18.
Using the optical information recording/reproducing unit 10 having a configuration similar to that of Example-1 and along the procedure shown in
In step B140, the reproduced-signal quality was measured, to reveal the results shown in
Example-4 will be described. The basic configuration of Example-4 is similar to that of Example-1, and is different therefrom in that performance judgment is performed succeeding to the determination of bias power (step C100 in
Basically, the medium approved by a corresponding standard has a limited performance within a specific standard, and satisfies the fixed standard without fail. In step C200, it is judged whether or not the reproducing performance has a level without a problem for the device operation after the recording is performed using the combination of the recording power determined in step B100 and the bias power determined in step C100. If the reproducing performance is judged satisfactory for the device operation (Good in performance), the process advances to step D100 wherein the combination of the recording power and bias power is set as the recording condition. if the reproducing performance is judged unsatisfactory for device operation (NG in performance), re-search processing of the power is performed (step D10).
In the re-search processing of the power in step D10, the absolute value of the power is changed, for example, with the ratio of the recording power to the bias power being maintained constant. In an alternative, parameters relating to the recording, such as the tilt between the optical head and the medium or a focusing position, are adjusted to perform the recording using the power optimized at this stage, i.e., not the initially used recording power or bias power, while changing the recording power with the bias power being fixed constant. The recorded area is then reproduced for the performance judgment to again re-determine the optimum recording power. If the reproducing performance satisfies the specific performance at this stage, the process advances to step D100 wherein the combination of the optimum recording power and the fixed bias power is set as the condition. If the specific performance is not satisfied, recording is performed while changing the bias power with the optimum recording power thus re-determined being fixed, and the recorded area is then reproduced to determine the optimum bias power.
Calibration of the recording condition was performed using the procedure shown in
The reproduced-signal quality was measured after the recording using the combination of the determined recording power and bias power, to reveal a PRSNR of about 15. With reference to the data of the disc manufacturer B-1 shown in
Example-5 will be described. The basic configuration of Example-5 is similar to that of Example-4, and is different therefrom in that medium identification is performed herein preceding to step A100 (
Recording was performed using the combination of the above optimum recording power and optimum bias power, and the reproduced-signal quality was measured, revealing a PRSNR of around 18. With reference to
Measurement of the 2T-asymmetry β-value under the above recording condition revealed a β-value of 0%, and this value was recorded in the drive test zone of the medium as the calibration information, obtained by the device as a device calibration, together with the device identification code (ID). The asymmetry value in tie recording power (11 mW) wherein the PRSNR assumes the maximum value before calibration was 1.5% (
In the above exemplary embodiment, an optical information recording/reproducing unit having a wavelength of 405 nm and a NA of 0.6 was used. However, the present invention is not limited to these configurations, and may be applied to a device having another wavelength and another NA. The recording waveform may be a recording waveform having a base on the pulse-train recording waveform or a recording waveform having a base on the rectangular waveform, and achieves similar advantage. Bias power 2 included in the recording power corresponding to the mark section in the case of using the pulse train waveform is not included in the calibration procedure in the embodiment because it does not relate directly to the present invention. However, in the case of a poor performance, this bias power 2 is also preferably subjected to the calibration. In this case, calibration of bias power 2 is preferably performed after the calibration of the bias power. Calibration for the recording waveform in the time axis direction, as the calibration for other than the power, may be performed as desired. As to the performance index used for determining the power other than those as described above, performance indexes known heretofore may be used depending on the device configuration. This may use the number of error bytes occurring in a specific number of ECC blocks, for example, or a number of PI errors that is the total number of lines for which an error is detected by the inner side parity of the ECC. That is, an index that can be basically replaced by an error index or an index that is used in a sense qualitatively equal to the error rate may be also used.
As described heretofore, in the calibration method for the recording-use optical irradiation power and optical information recording/reproducing unit according to the exemplary embodiment of the present invention, with respect to the write-once recoding medium for which recoding is performed by switching the irradiation between the recording power and the bias power depending on the mark and space, the recording power is first calibrated at a recording power that provides a suitable reproduced-signal quality, and thereafter, the bias power is determined using the calibrated recording power. More specifically, calibration of the recording power that determines the mark length (size) is first performed, followed by determining the mark-shaping power (bias power) matched with the calibrated recording power, i.e., matched with the mark formed thereby, whereby the recording-use optical irradiation power that provides a suitable recording/reproducing characteristic can be calibrated at a higher speed and with a higher degree of certainty.
Hereinafter, embodiments that may be employed in the present invention will be exemplified.
The recording-use optical-irradiation-power calibration method may employ a configuration wherein the bias power selecting step:
records a specific pattern train while stepwise changing the bias power with the recording power being fixed onto the selected recording power; measures a reproduced-signal quality by reproducing the recorded specific pattern train; and selects a bias power that provides a highest reproduced-signal quality from among bias powers that are stepwise changed therebetween. In the optical information recording/reproducing unit, a configuration may be employed wherein the parameter calibration unit selects, upon selecting the bias power, the bias power that allows the measured reproduced-signal quality to assume an optimum reproduced-signal quality from among bias powers that are stepwise changed therebetween, based on a reproduced-signal quality that is measured by the reproduced-signal quality measurement section from a pattern train that is recorded while changing the bias power with the recording power being fixed onto the selected recording power. In this case, a bias power that provides the best reproduced-signal quality in the combination with the selected recording power is selected as the bias power used during the recording, whereby it is possible to determine a recording-use optical irradiation power that can derive the medium performance at a maximum.
In an alternative of the above, the recording-use optical-irradiation-power calibration method of the present invention may employ a configuration wherein the bias power selecting step selects the bias power based on the selected recording power in accordance with a correspondence relationship specified in advance between the recording power and the bias power. In the optical information recording/reproducing unit, a configuration may be employed wherein the parameter calibration unit selects the bias power based on the selected recording power and a bias power that is set in connection with the recording power in advance. For example, the bias power is determined from the selected recording power based on the ratio of the recording power to the bias power. In the case of using this way, the time length of selection of the bias power can be reduced compared to the case of performing actual recording.
The recording-use optical-irradiation-power calibration method of the present invention may employ a configuration wherein the reproduced-signal quality includes at least one of a PRSNR and an error rate that is calculated based on a reproduced signal reproduced from the pattern train. In the optical information recording/reproducing unit of the present invention a configuration may be employed wherein the reproduced-signal quality measurement section calculates at least one of PRSNR and an error rate based on the reproduced signal.
The recording-use optical-irradiation-power calibration method of the present invention may further include the step of reading out control information including information of a setting of the bias power recorded on the recording medium, prior to the recording step, wherein: the recording step determines the specific bias power based on the information of setting of bias power included in the read-out control information. In the optical information recording/reproducing unit of the present invention, a configuration may be employed wherein the recording medium (50) records thereon control information including information of the bias power, and the parameter calibration unit determines the specific bias power, used upon performing recording while changing the recording power, based on information of setting of the bias power included in the control information. For example, if the control information includes a recommended value for the bias power suited for the set optical information recording medium, this information is used upon determining the bias power. In this case, the degree of the bias power determined in advance can be forecast.
In the recording-use optical-irradiation-power calibration method of the present invention, a configuration may be employed wherein the control information includes a correspondence relationship between the recording power and the bias power, and the bias power selecting step selects the bias power from the selected recording power based on information of the correspondence relationship. In the optical information recording/reproducing unit of the present invention, a configuration may be employed wherein the control information includes information of a correspondence relationship between the recording power and the bias power, and the parameter calibration unit selects the bias power based on the selected recording power in accordance with information of the correspondence relationship.
The recording-use optical-irradiation-power calibration method of the present invention may employ a configuration wherein the recording medium is a write-once medium, wherein a recorded mark is formed by a photochemical reaction or a photo-thermal-chemical reaction, at least a portion of a recording film in the recording medium is formed from an organic pigment, and the medium is configured such that an optical reflectance of a mark section formed by the optical beam irradiation is higher than an optical reflectance prior to the laser beam irradiation. In the optical information recording/reproducing unit of the present invention, a configuration may be employed wherein the recording medium is a write-once recording medium for which a recorded mark is mainly formed by photochemical reaction or a photo-thermal-chemical reaction, at least a part of a recording film of the recording medium is formed from an organic pigment, and an optical reflectance of a mark section formed by the optical beam irradiation is higher than an optical reflectance of the medium prior to the laser beam irradiation.
While the present invention has been described based on the preferred embodiment thereof, the calibration method for the optical irradiation power and the optical information recording/reproducing unit of the present invention are not limited only to the configuration of the above exemplary embodiment, and a variety of modifications and alterations of the configuration of the above embodiment may fall within the scope of the present invention.
The present invention can be widely applied, as the optical-irradiation-power calibration method, to the recording by switching the irradiation onto a write-once recording medium (medium for which a recorded mark is formed by a photochemical reaction or photo-thermal-chemical reaction) between the recording power and the bias power (mark-shaping power) depending on the mark and space, and can achieve the advantage that the calibration time length for the recording-use optical irradiation power, calibration accuracy thereof, and reliability of the device using the same can be drastically improved.
This application is based upon and claims the benefit of priority from Japanese patent application No. 2006-250870, filed on Sep. 15, 2006, the disclosure of which is incorporated herein in its entirety by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-250870 | Sep 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/067948 | 9/14/2007 | WO | 00 | 3/13/2009 |
