JP2013118022A - Power adjustment method and information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that although the SNR of a reproduction signal is improved by increasing reproduction power, maximum reproduction power allowed for respective reproduction speeds of respective media depends upon reproduction light resistance of the media and cannot be uniquely determined.SOLUTION: Maximum reproduction power for each reproduction speed is calculated based upon reproduction signal quality, a reproduction lifetime, or the allowed number of times of reproduction. A parameter of an approximate expression is calculated from the relation between a reproduction speed and reproduction power or the relation between the reproduction speed ratio and a reproduction power ratio. The maximum reproduction power allowed for each reproduction speed of each medium is determined based upon the approximate expression, and reproduction is carried out using the maximum reproduction power to maximize the SNR without deteriorating the medium.

Description

  The present invention relates to a power adjustment method for adjusting power and an information reproducing apparatus for implementing the power adjustment method.

  Currently, CDs (Compact Discs), DVDs (Digital Versatile Discs), BDs (Blu-ray Discs), BDXLs, and the like have been commercialized as optical discs that are optical information recording media. There are various types of optical discs, such as a read-only ROM type (Read Only Memory), a write-once type R type (Recordable), and a rewritable type RE type (Rewritable). The data capacity of optical discs has been increased to CD (650 MB), DVD (single layer 4.7 GB), and BD (25 GB), and these are mainly due to shortening the wavelength of the light source and increasing the NA of the objective lens. It was realized that minute data on an optical disk can be read. BDXL, which has been commercialized in recent years, has a data layer of 3 to 4 layers based on BD, and by increasing the surface density per layer to 32 to 33.4 GB by signal processing, it can be up to 128 GB per disc. Realized. Since it is difficult to further shorten the wavelength of the light source and increase the NA of the objective lens, further multilayering and higher density are being studied for future optical discs.

  Information recording / reproduction on the optical disc is performed by irradiating the optical disc with laser light by an optical disc drive which is an optical information recording device. Information recording is performed by changing the irradiation power of the laser beam and forming a mark with changed optical characteristics on the data layer of the optical disk. Information reproduction is performed by irradiating a laser beam having a lower power than that in which a mark is formed on the data layer of the optical disc and detecting a difference in reflected light amount at each irradiation position.

  The optimum recording power used for information recording differs depending on the type of the optical disc and the manufacturer of the optical disc, and the drive needs to set the optimum recording power according to the type of the optical disc. However, even with the same type of optical disc, the optimum recording power differs from one optical disc to another due to manufacturing variations, and optimal recording may not be realized with the same recording power. Even when the same optical disk is used, optimal recording may not be realized with the same set power due to power variations between drives. Therefore, each drive has a configuration in which, prior to recording on the optical disc, trial writing is performed in a predetermined area, and the optimum recording power corresponding to the optical disc is adjusted. The recording power adjustment operation in this recording is called OPC (Optimum Power Control). With this OPC, each optical disk apparatus realizes good information recording.

  Since this OPC needs to be performed at each recording speed, it is difficult to perform good recording by CAV recording (Constant Angular Velocity) with a constant angular velocity of the disk. Here, Patent Document 1 describes a recording power adjustment method corresponding to CAV recording. This method realizes CAV recording by increasing the recording power in linear proportion to the recording speed. At this time, the recording area is divided along the radial direction of the disk, the recording quality is confirmed at the end of each recording area, the excess or deficiency of the recording power is detected, and the proportional coefficient of the recording power with respect to the recording speed is corrected. This achieves high recording quality.

  In the reproduction of information, the mark in the data layer is read as a change in the amount of reflected light, but the reproduction signal is fluctuated by noise such as a photodetector. This fluctuation amount increases as the reproduction speed increases. This is because as the reproduction speed increases, the signal band to be acquired as a reproduction signal increases, and as a result, the amount of noise increases. The influence of these noises can be reduced by increasing the reproduction power and increasing the signal to noise ratio (SNR). Therefore, in the optical disc apparatus, the reproduction power is changed according to the reproduction speed, and good reproduction is realized at each reproduction speed.

  Here, Patent Document 2 and Patent Document 3 describe a reproduction method for setting an appropriate reproduction power and realizing reproduction even during a reproduction speed change. In these methods, a laser power setting table for determining the current reproduction power is acquired in advance using the ratio between the target reproduction speed and the current reproduction speed. During the playback speed change, the current playback power and the target playback speed are used to determine the current playback power from the laser power setting table and perform playback. As a result, the playback power is changed in stages while the playback speed is changed, so that good playback is always realized.

  Further, Patent Document 4 discloses a reproduction method that realizes reproduction even when the reproduction speed is changed in a super-resolution medium capable of reproducing a mark having an optical resolution or less. In this method, optimum reproduction powers at two reproduction speeds are determined in advance, and a table of optimum reproduction power at each reproduction speed is created by linearly complementing the relationship between the reproduction speed and the optimum reproduction power. At the time of reproduction, the optimum reproduction power at the current reproduction speed is determined from the created table, so that good reproduction is always realized.

Japanese Patent Laid-Open No. 2001-3409 JP 2001-38354 A JP 2003-187451 A JP 2005-135538 A

  In increasing the density and the number of layers of optical discs, a reduction in the SNR of the reproduction signal becomes a problem. FIG. 1 shows the result of calculating the deterioration amount of the signal amplitude (modulation degree) of 8 Tw and 3 Tw when the surface density is increased. In the calculation, the track pitch was fixed at 0.32 μm, which is the same as the current BD, and only the linear density was increased. Each signal amplitude was normalized to 25 GB corresponding to the density of BD. Since the 3Tw amplitude with respect to the increase in the surface density is remarkably deteriorated, it can be seen that securing the SNR is important in increasing the density.

  FIG. 2 shows the calculation result of the relationship between the reproduction speed and the SNR when the reflectance of the data layer is lowered due to the multi-layering. In the calculation, the reproduction power at each reflectance and each reproduction speed was assumed to be constant. The SNR was calculated using the degree of modulation, disk noise, and system noise based on actual measurement results. The disc noise is a noise that varies depending on the reproduction power derived from the disc, and the system noise is an electric noise of the optical disc apparatus. When attention is paid to the SNR of each reflectance at the reproduction speed 2x, it can be seen that the amount of degradation of the SNR increases as the reflectance decreases. Further, it can be seen that the SNR deterioration amount with respect to the reproduction speed is larger at the low reflectance than at the high reflectance. From this, the SNR significantly decreases due to the decrease in reflectivity, so it is important to secure the SNR even in the case of multi-layering.

  It is necessary to increase the reproduction power in order to ensure SNR in higher density and multilayer. However, if the playback is performed carelessly with high playback power, the data layer signal may be degraded. FIG. 3 shows the results of actual measurement of reproduction power (Pr) and the number of reproducible times in two media (Disc 1 and 2). The horizontal axis is 1 / Pr, and the number of reproducible times is the number of times that the reproduction signal quality is below the reference value when reproduction is performed at each reproduction power. The number of reproducible times with respect to the reproduction power differs between Discs 1 and 2, which indicates that the reproduction light resistance varies depending on the medium. From this result, it can be seen that if the reproduction power is set in accordance with a medium having high reproduction light resistance in order to ensure SNR, the signal is deteriorated in the medium having low reproduction light resistance. In addition, if the reproduction power is set in accordance with a medium having low reproduction light resistance, it is not possible to expect an SNR improvement in a medium having high reproduction light resistance.

  The present invention solves the above-described problems and provides a reproduction power adjustment method that gives the best reproduction signal quality to each medium, an information recording medium and information recording / reproduction apparatus that retains information used for reproduction power adjustment, and the reproduction power Provided is an information recording / reproducing apparatus for performing an adjustment method.

  The above problem is to determine an approximate expression of the reproduction speed and the allowable reproduction power based on the reproduction light tolerance of each medium, determine the reproduction power at each reproduction speed using the approximate expression, and use the determined reproduction power. This can be solved by using the reproduction power adjusting method of the present invention for performing reproduction.

As the approximate expression, the following expressions (1) to (5) are used. The meaning of the symbols in the formula will be described later.

  In the reproduction power adjustment, the reproduction speed is substituted into the approximate expressions (1) to (5) in which the parameters are determined, the reproduction power is calculated, and reproduction is performed with the calculated reproduction power. Thereby, reproduction using the maximum reproduction power in consideration of reproduction light tolerance of each medium is realized, and the maximum SNR is realized in each medium. Furthermore, since the playback power can be determined and changed continuously even while the playback speed is being changed, playback can also be realized while the playback speed is being changed.

  Here, the above-described reproduction power adjustment is performed on the reproduction power, but high frequency superposition (HF) is applied to the laser used for reproduction, and the peak power higher than the average reproduction power is irradiated on the medium. There is also. When this peak power is the rate-determining medium deterioration, it is possible to perform the above-described reproduction power adjustment for the peak power. Thereby, even when the reproduction light added with HF is used, reproduction with the maximum SNR is realized without deteriorating the medium.

  By storing the determined parameters of the approximate expression in the management area of the optical disk or the storage unit of the optical disk apparatus, it is possible to quickly adjust the reproduction power of the laser beam for reproducing the optical disk.

According to the reproduction power adjustment method of the present invention, it is possible to determine the reproduction power that provides the best SNR of the reproduction signal without degrading the medium by adjusting the reproduction power based on the reproduction light resistance of each medium.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

The figure of an example showing the relationship between areal density and the amount of degradation of 8Tw and 3Tw signal amplitude. The figure of an example showing the relationship between reproduction speed and SNR when the reflectance of a data layer falls. The figure of an example showing the relationship between reproduction power and the frequency | count of reproduction | regeneration possible. 1 is a block diagram showing an example of an optical disc apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating an example of a control unit of an optical disc apparatus according to an embodiment of the present invention. The flowchart of an example which shows the procedure of reproduction | regeneration power adjustment. The figure of an example showing the relationship between reproduction time and signal quality. The figure of an example showing the relationship between reproduction | regeneration power and reproduction | regeneration possible time (life). The figure of an example of the result of having calculated the maximum reproduction power on the basis of reproducible time (life) in each reproduction speed. The figure of an example of the result of having calculated the maximum reproduction power on the basis of the number of possible reproductions at each reproduction speed. The figure of an example showing the relationship between reproduction speed ratio and maximum reproduction power ratio. The figure of an example showing the change with respect to the reproduction speed of parameter (eta) (v) regarding the thermal characteristic of a medium. The figure of an example showing the correlation of the logarithm value of reproduction speed ratio, and the logarithm value of maximum reproduction power ratio. The figure of an example which shows the result of fitting the relationship between reproduction speed ratio and maximum reproduction power ratio. The schematic diagram of an example which shows the management information of an optical disk, and the information structure in management information. The figure of an example showing the relationship between playback speed and SNR when playback power adjustment is not performed and when it is performed. The figure of an example showing the time-dependent change of reproduction | regeneration signal quality in the case where reproduction power adjustment is implemented while changing reproduction speed, and when it is not implemented. The figure of an example showing the relationship between the reproduction speed and SNR when reproduction power adjustment is performed with respect to HF peak power.

Hereinafter, a reproduction power adjusting method as an embodiment of the present invention will be described with reference to the drawings.
In the following, after explaining the configuration of the optical disk apparatus, a method for adjusting the reproduction power in the optical disk apparatus will be described as an embodiment of the present invention.

[Example 1]
FIG. 4 shows a block diagram of the main part of the optical disk apparatus used in this embodiment. The optical disk 10 is rotated by a spindle motor 12 and is controlled by CLV (Constant Linear Velocity) or CAV. An optical pickup unit 14 is provided opposite to the optical disk 10, and recording / reproduction of the optical disk 10 is performed by irradiating laser light 16 from a laser diode (LD).

  When recording a signal, the optical disk 10 is irradiated with a laser beam 16 having a recording power, and the signal is written. When the optical disk 10 is a rewritable optical disk, the signal is erased by irradiating the optical disk 10 with laser light 16 having an erasing power. The recording signal is encoded by the encoder 18 and supplied to the LD driving unit 20. The LD drive unit 20 generates a drive signal based on the encoded recording signal, supplies the drive signal to the LD of the optical pickup unit 14, and records the signal by intensity modulation of the laser light 16 based on the supplied signal. The recording power in the LD driving unit 20 is determined by a control signal from the control unit 22. Prior to signal recording, the control unit 22 performs test writing using a plurality of types of recording power in the test writing area of the optical disc 10, and determines the optimum recording power based on the test writing signal (OPC: Optimum). Power Control).

  When reproducing a signal, the optical disk 10 is irradiated with a laser beam 16 having a reproduction power, and the signal is reproduced. The laser beam 16 reflected by the optical disk 10 is converted into an electric signal by the photodetector of the optical pickup unit 14, and is output as an RF signal or the like after a predetermined calculation. A signal from the optical pickup unit is supplied to an RF signal processing unit (and level acquisition unit) 24. The RF signal processing unit 24 has functions of an RF amplifier, an equalizer, a binarizer, a PLL, and the like, processes the RF signal with these, and supplies the processed signal to the decoder 26. The decoder 26 decodes the signal based on the binarized RF signal and the synchronous clock reproduced by the PLL, and outputs it as reproduced data. The RF signal processing unit 24 also includes a level detector, calculates an upper envelope (High envelope), a lower envelope (Low envelope), and the like of the reproduction signal and supplies them to the controller 22 as a signal evaluation signal. The RF signal is supplied from the RF signal processing unit 24 to the control unit 22 as a signal evaluation signal. At the time of recording / reproduction, a circuit that generates a focus error signal and a tracking error signal and controls focus servo and tracking servo, and a circuit that reproduces a wobble signal formed on the optical disk 10 to perform address demodulation or rotation control of the optical disk 10 However, since these are the same as those in the prior art, description thereof is omitted.

  The control unit 22 performs the reproduction power adjustment based on the signal supplied from the RF signal processing unit 22 and the like as well as the OPC that is the recording power adjustment, and supplies the power control signal that is the adjustment result to the LD driving unit 20. It has a function. FIG. 5 shows a block diagram of functions related to recording power adjustment and reproduction power adjustment in the control unit 22. The control unit 22 is specifically composed of a microcomputer, and its function blocks include a signal quality calculation unit, a maximum reproduction power (Pr) determination unit, an optimum recording power (Pw) determination unit, a power adjustment parameter calculation unit, and a power calculation. Part and a storage part. The storage unit can be composed of a RAM, and the other functional blocks can be composed of a single CPU.

  The recording power adjustment in the control unit 22 is performed based on the signal quality of trial writing. The modulation factor is calculated by the signal quality calculation unit from the reproduction signal of the trial writing, and the modulation factor is stored in the storage unit in association with the recording power. The optimum recording power determination unit determines the optimum recording power based on the relationship between the recording power and the modulation degree in the storage unit and the management information of the optical disk acquired through a path (not shown). The determined optimum recording power is supplied to the LD drive unit 20 as a power control signal and used for recording.

  In the reproduction power adjustment in the control unit 22, the reproduction signal is supplied to the signal quality calculation unit, the signal quality of the reproduction signal is calculated, and stored in the storage unit in association with the reproduction power, the reproduction speed, the number of reproductions, and the reproduction time. . Signal quality includes bER (bit error rate), SER (symbol error rate), Jitter which is a signal quality index in each optical disc standard, i-MLSE (integrated-Maximum Likelihood Sequence Error), L-SEAT (run-length- Limited Sequence Error for Adaptive Target) is used. The maximum reproduction power determination unit determines the maximum reproduction power at each reproduction speed based on the reproduction power, the number of reproductions or reproduction time, reproduction signal quality, and their reference values, and stores them in the storage unit. The power adjustment parameter calculation unit calculates an approximate expression parameter of this relationship from the relationship between the reproduction speed and the maximum reproduction power, and stores it in the storage unit. The power calculation unit calculates the optimum reproduction power at the reproduction speed using the reproduction speed and the approximate expression, and supplies the optimum reproduction power to the LD drive unit as a power control signal.

  Hereinafter, the result of adjusting the reproduction power according to the flow of FIG. 6 using the optical disc apparatus will be described. First, the maximum playback power at each playback speed was calculated based on the playback signal quality on the optical disc and the playback life or the number of playbacks possible (S10). A random pattern was recorded in the user data area (or test writing area) as a signal for measuring the reproduction light resistance of the optical disc, and the relationship between reproduction time and signal quality at each reproduction power (Pr) was measured using such a signal. In the measurement, the playback speed is constant. The results are shown in FIG. Here, as described above, there are bER, SER, Jitter, i-MLSE, L-SEAT, and the like as signal quality indexes. Since any index is correlated with bER, any index can be used as shown in FIG. Similar results are obtained. FIG. 7 shows a reference value of signal quality (a reference that makes it difficult to reproduce a signal), and the intersection of each reproduction power graph and the reference value of signal quality corresponds to the reproduction life.

  FIG. 8 shows the result of plotting the relationship between the reproduction power and the reproduction life. FIG. 8 shows two results with different reproduction speeds, and also shows a reference value for the reproduction life. The intersection between the graph of each playback speed and the reference of the playback life is the maximum value of the playback power allowed at each playback speed. Based on the result of FIG. 8, the maximum reproduction power at each reproduction speed was calculated. FIG. 9 shows the relationship between the reproduction speed and the maximum reproduction power when the reproducible number of times satisfies the reference value. FIG. 10 shows the relationship between the reproduction speed and the maximum reproduction power when the reproducible time (lifetime) satisfies the reference value. 9 and 10 show the results of normalizing the maximum playback power at each playback speed with the maximum playback power at the minimum playback speed (FIG. 11 is an example of normalization with respect to FIG. 10).

Next, prior to the determination of the approximate expression (S11) from the relationship between the playback speed and the maximum playback power, a theoretical analysis was performed on the correlation between the playback speed and the maximum playback power. Here, it is assumed that the deterioration of the optical disk depends on the peak temperature during reproduction. The temperature rise ΔT of the medium at the irradiation power P and the linear velocity v is approximated by Expression (6).

Here, Δt is the laser irradiation time and is proportional to 1 / v. Further, η (v) is a coefficient relating to the thermal diffusion characteristics of the medium, and FIG. 12 shows the result of calculation with respect to the thermal characteristics of the medium and the linear velocity v. Since η (v) is a function having a steep rise, it can be understood that an actual medium excluding the limit of heat insulation and heat dissipation can be approximated using a power function. That is, it is approximated by Expression (7). Expression (8) is obtained by substituting Expression (7) into Expression (6) and rearranging the coefficients.

ここから、再生速度と最大再生パワーは式（１）（２）で近似可能であることが分かる。この関係は、特に媒体の劣化がピーク温度に律速な場合に適用される。 The deterioration of the medium is determined by the peak temperature, that is, the sum of the temperature increase ΔT and the room temperature Trt. From this, it can be seen that the maximum temperature rise amount ΔT allowed for the medium at each room temperature is uniquely determined, and the relationship between the reproduction power P and the reproduction speed v in that case is expressed by equation (8). Expression (1) is the result of dividing both sides of Expression (8) by α ″ × v ⁻ⁿ and arranging the constants ΔT and α ″ together with α. Further, the general formula in consideration of the offset in the formula (1) is the formula (2).

From this, it can be seen that the reproduction speed and the maximum reproduction power can be approximated by the equations (1) and (2). This relationship is applied particularly when the deterioration of the medium is rate-limiting to the peak temperature.

Unlike the above, when it is assumed that the deterioration of the optical disk follows the Arrhenius law depending on the temperature at the time of reproduction, the medium life t is given by equation (9).

ここから、再生可能時間と再生パワーは式（３）で近似可能であることがわかる。 β is a coefficient summarizing the Boltzmann constant, the activation energy of the medium, and the like. By substituting equation (8) into equation (9), equation (3) is obtained.

From this, it can be seen that the reproducible time and the regenerative power can be approximated by Equation (3).

ここから、再生可能回数と最大再生パワーは式（４）で近似可能であることが分かる。 Further, since the life t is the product of the number N of reproducible times and one reproduction time Δt (1 / v), equation (4) can be obtained by replacing t in equation (9) with N / v. .

From this, it can be seen that the number of reproducible times and the maximum reproduction power can be approximated by Expression (4).

Further, the relationship between the reproduction speed and the maximum reproduction power is considered as a reproduction speed ratio (v / v1) and a maximum reproduction power ratio (P / P1) using the reference reproduction speed v1. At this time, based on Expression (8), the reproduction speeds v1 and v and the maximum amount of temperature increase ΔT at the maximum reproduction powers P1 and P are equal, and Expression (10) is established. By rearranging equation (10), equation (5) is obtained.

  Here, v1 and P1 in Equation (5) are the reproduction speed and reproduction power used for normalization. From this, it can be seen that the reproduction speed ratio and the maximum reproduction power ratio can be approximated by Expression (5).

Equation (5) can also be obtained by modifying equation (11) for the reproduction life t of equation (3), and it can be seen that it can also be used for media that follow Arrhenius law.

  From the above theoretical analysis, it can be seen that the relationship between the reproduction speed and the maximum reproduction power is approximated using the equations (1) to (5), and the approximate equation can be determined by determining these parameters. Here, the parameters of the approximate expressions (1) and (2) may be calculated by fitting the relationships shown in FIGS. Further, the parameter calculation of the approximate expression of Expression (3) may be performed by fitting the relationship of FIG. 8, and the parameter calculation of the approximate expression of Expression (4) is performed by converting the vertical axis of FIG. Fit it. Furthermore, the parameter calculation of the approximate expression of Expression (5) may be performed by fitting the relationship shown in FIG.

  In the present embodiment, the approximate expression is determined from the relationship between the reproduction speed ratio and the maximum reproduction power ratio using Expression (5). The parameter n in equation (5) can be determined so that the square sum of the error in the measurement at each reproduction speed ratio and the error in the maximum reproduction power ratio in equation (5) is minimized. However, in this embodiment, in order to determine the parameter n more simply, the logarithm is taken for both the reproduction speed ratio and the maximum reproduction power ratio, and the parameter n is determined to be 0.46 by linearly approximating them (S11). ). The result of taking the logarithm is shown in FIG. As shown in Expression (5), the maximum reproduction power ratio is the nth power of the reproduction speed ratio, and the slope of the graph in FIG. 13 corresponds to the parameter n. From this, the slope of the approximate straight line was calculated as n. This result coincides with the result of directly fitting the relationship between the reproduction speed ratio and the maximum reproduction power ratio.

  FIG. 14 shows the relationship between the approximate expression determined based on Expression (5) and the measurement results of the reproduction speed ratio and the maximum reproduction power ratio. It can be seen that the approximate expression can accurately approximate the relationship between the reproduction speed ratio and the maximum reproduction power ratio.

  The parameters of the approximate expression and the reproduction speed and the maximum reproduction power based on the reproduction speed ratio and the maximum reproduction power ratio are held in DI 102 (Disc Information) in the management area 101 of the optical disc 100 shown in FIG. Thus, the steps S10 and S11 shown in FIG. 6 can be omitted in the subsequent reproduction, and the reproduction power adjustment time can be shortened. For this purpose, parameters corresponding to the approximate expression used by the disc manufacturer, and the reference playback speed and maximum playback power are determined in advance by means similar to S10 and S11 in FIG. It is desirable to store it in DI102. In addition, when these parameters are determined by the optical disk device, they can be stored in the management area 101 or stored in the storage unit of the optical disk device so that they can be read and used when necessary. This makes it possible to adjust the reproduction power in a short time.

  Finally, reproduction power adjustment based on the determined approximate expression was performed (S12). The reproduction power adjustment is very easy. Using the approximate expression based on the determined expression (5), the reference reproduction speed (1x), and the maximum reproduction power (0.95 mW), the target reproduction speed is expressed by the formula ( By substituting in 5), the maximum reproduction power at the reproduction speed was calculated. FIG. 16 shows the result of reproduction using the maximum reproduction power calculated at each reproduction speed. FIG. 16 also shows the results when reproduction is performed at a constant reproduction power without performing reproduction power adjustment. By performing the reproduction power adjustment, it was confirmed that an SNR decrease due to an increase in the reproduction speed was suppressed and an almost constant SNR was obtained. In addition, since the reproduction power at all reproduction speeds is determined from the relationship shown in FIG. 14 based on reproduction light resistance, the medium is not deteriorated.

  From the above, it was confirmed that the reproduction power adjustment based on the reproduction light resistance of the medium was realized by using the reproduction power adjustment method of this example, and the maximum SNR in the medium was realized.

[Example 2]
In the present embodiment, a result of performing reproduction while changing the reproduction speed using the approximate expression determined in the first embodiment will be described. The portions that are not changed are the same as those in the first embodiment and the other embodiments related to the first embodiment, and thus detailed description thereof is omitted here.

  During the change of the playback speed from v1 to v2, the playback speed v at each time was obtained, and the maximum playback power at each time was calculated using the approximate expression and the reference value of the playback speed and the maximum playback power. Then, the reproduction power during the reproduction speed change was changed to the reproduction power calculated as needed, and reproduction was performed. The result is shown in FIG. In the figure, the case where the reproduction power adjustment is not performed is also shown. When the playback power adjustment is not performed, the signal quality is significantly degraded as the playback speed is increased. However, when the playback power adjustment is performed, a substantially constant signal quality can be maintained while the target playback speed and the playback speed are changed. I understand that.

  From the above results, it was confirmed that by using the reproduction power adjustment method of the present embodiment, reproduction power adjustment was realized even when the reproduction speed was changed, and appropriate reproduction signal quality was always obtained. In this embodiment, the playback while changing the playback speed has been described. However, it is clear that the playback signal quality can be maintained by performing the playback power adjustment even with respect to the linear speed change due to the difference in the radial position in CAV playback. is there.

Example 3
In the present embodiment, a case will be described in which the method for determining an approximate expression in the first embodiment is changed. The portions that are not changed are the same as those in the first embodiment and the other embodiments related to the first embodiment, and thus detailed description thereof is omitted here.

  In this example, the relation between the reproduction speed and the maximum reproduction power was fitted by the equation (2) to determine an approximate equation. In the fitting, the parameters α, n, and β in Equation (2) were determined so that the sum of squares of the error in the measurement at each reproduction speed and the maximum reproduction power in Equation (2) was minimized. The parameters of equation (2) were determined to be α = 0.9, n = 0.46, β = 0. The parameter of the approximate expression thus determined is stored in the DI within the management area of the optical disc or the storage unit of the optical disc apparatus.

  The reproduction power adjustment using the determined approximate expression was performed by calculating the maximum reproduction power by substituting the target reproduction speed into equation (2) and using the calculated maximum reproduction power as the reproduction power at the reproduction speed. . The result of measuring the SNR at each reproduction speed using this reproduction power adjustment method is the same as in FIG. 16, and reproduction power adjustment based on the reproduction light resistance of the medium is realized by using the reproduction power adjustment of this embodiment. It was confirmed that the maximum SNR in the medium was realized. In particular, in the method of the present embodiment, the parameters of the approximate expression are increased as compared with the first embodiment, but the reference values for the reproduction speed and the reproduction power are not necessary.

Example 4
In the present embodiment, a case will be described in which the method for determining an approximate expression in the first embodiment is changed. The portions that are not changed are the same as those in the first embodiment and the other embodiments related to the first embodiment, and thus detailed description thereof is omitted here.

  In this example, the relation between the reproduction speed and the maximum reproduction power was fitted by the expression (1), and an approximate expression was determined. Fitting is possible by determining the parameters α and n in the equation (1) so that the square sum of the error at the maximum reproduction power in the measurement at each reproduction speed and the equation (1) is minimized. However, in this embodiment, in order to determine the parameter n more easily, logarithm is taken for both the reproduction speed and the maximum reproduction power, and they are linearly approximated so that the slope of the approximate line and the logarithmic value of the reproduction speed are zero. The intercept corresponding to was calculated. The calculated slope is parameter n, and n = 0.46 was determined. Since the calculated intercept is a logarithmic value of the parameter α, α = 0.9 was determined as the intercept power of the base of the logarithm. The approximate expression obtained from this is the same as in the third embodiment. This is because Expression (1) is an approximate expression when β in Expression (2) is zero. The parameter of the approximate expression thus determined is stored in the DI within the management area of the optical disc or the storage unit of the optical disc apparatus.

  The reproduction power adjustment using the determined approximate expression was performed by calculating the maximum reproduction power by substituting the target reproduction speed into equation (1) and using the calculated maximum reproduction power as the reproduction power at the reproduction speed. . The result of measuring the SNR at each reproduction speed using this reproduction power adjustment method is the same as in FIG. 16, and reproduction power adjustment based on the reproduction light resistance of the medium is realized by using the reproduction power adjustment of this embodiment. It was confirmed that the maximum SNR in the medium was realized. In particular, in the method of the present embodiment, the parameters of the approximate expression are increased as compared with the first embodiment, but the reference values for the reproduction speed and the reproduction power are not necessary.

  Here, when determining an approximate expression using Expression (3), the parameters t, α, α ′, and Trt in Expression (3) are all constants. can get. From this, also when Expression (3) is used, parameter values similar to those in the present embodiment are calculated, and as a result, reproduction power adjustment similar to that in the present embodiment is realized.

Example 5
In the present embodiment, a case will be described in which the method for determining the maximum playback power for each playback speed in Embodiment 1 is changed. The portions that are not changed are the same as those in the first embodiment and the other embodiments related to the first embodiment, and thus detailed description thereof is omitted here.

  In this embodiment, the maximum reproduction power is determined based on the number of reproductions possible. That is, in FIG. 7, the signal quality is measured with respect to the reproduction time, but this time, the signal quality is measured with respect to the number of reproductions. In FIG. 8, the maximum playback power at each playback speed is determined using the reference value of the playback life, but this time the maximum playback power is determined based on the reference of the number of playbacks.

Fitting was performed using Equation (4) for the relationship between the determined reproduction speed and the maximum reproduction power. Formula (12) is obtained by transforming Formula (4) and rearranging the constants.

  In the fitting, the parameters n, α, and β in Equation (12) were determined so that the sum of squares of the error in the measurement at each reproduction speed and the maximum reproduction power in Equation (12) was minimized. The parameters of equation (12) were determined as n = 0.4, α = 0.9, β = 0.1. The parameter of the approximate expression thus determined is stored in the DI within the management area of the optical disc or the storage unit of the optical disc apparatus.

  As a result of adjusting the reproduction power at each reproduction speed using the determined approximate expression, it was confirmed that the SNR during high-speed reproduction was improved by 1 dB with respect to the result of FIG. Here, the SNR is improved from that in FIG. 16 because the maximum reproduction power is determined by the number of reproducible times in the present embodiment, so that the reproduction life to be guaranteed becomes shorter with high-speed reproduction, and as a result, the maximum reproduction power is increased. Because it was possible.

Example 6
In this embodiment, the power adjustment is applied to the HF peak power.
Using the optical disk device of Example 1, the relationship between the reproduction time and signal quality for each HF peak power was measured. As a result, a graph similar to FIG. 7 was created, and the reproduction time for each HF peak power was calculated based on the signal quality reference value. The same measurement was performed for each reproduction speed, and the relationship between the HF peak power and the reproduction time at each reproduction speed was calculated. As a result, a graph similar to FIG. 8 was created, and the maximum HF peak power at each playback speed was calculated based on the reference value of the playback life. As a result of plotting the relationship between the reproduction speed ratio and the maximum HF peak power ratio, the same correlation as in FIG. 14 was obtained. This indicates that the deterioration of the medium is rate-determining with respect to the peak temperature during reproduction, and when reproduction is performed with HF, the peak temperature due to HF contributes to the deterioration of the medium.

  As in the first embodiment, the fitting of the relationship between the reproduction speed ratio and the maximum HF peak power ratio using the equation (5) is performed. As a result, the parameter of the equation (5) is determined to be n = 0.46. It was. The parameter of the approximate expression thus determined is stored in the DI within the management area of the optical disc or the storage unit of the optical disc apparatus. Here, the fitting was performed by linearly approximating the logarithm of the reproduction speed ratio and the maximum HF peak power ratio as in the first embodiment. Using the determined approximate expression, reproduction power adjustment for HF was performed. Specifically, the reproduction speed, the reference reproduction speed and the maximum HF peak power were substituted, and the peak power at each reproduction speed was calculated. Here, the ratio of the HF amplitude to the average power was set to 0.5. The results of measuring the SNR at each playback speed are shown in FIG. It has been confirmed that by performing the reproduction power adjustment, a higher SNR is ensured than when the reproduction power adjustment is not performed. On the other hand, the SNR is lower than the result of FIG. 16, which is due to the lower average reproduction power in order to avoid medium deterioration due to the HF peak power. However, when the suppression of LD noise by HF is essential, the SNR can be improved without deteriorating the medium by the reproduction power adjustment of this embodiment.

  In the present embodiment, power adjustment was performed in the same procedure as in the first embodiment, but it is obvious that the same effect as in the present embodiment can be obtained even if the method described in the other embodiments is used.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

10: Optical disk 12: Spindle motor 14: Optical pickup unit 16: Laser light 18: Encoder 20: LD drive unit 22: Control unit 24: RF signal processing unit, Level acquisition unit 26: Decoder 100: Optical disc 101: Management area 102: DI (Disc Information)
103: Defect management information 104: Test writing area

Claims (14)

A method of adjusting the reproduction power of laser light for reproducing an optical information recording medium,
Calculating a maximum reproduction power P at each reproduction speed v;
Calculating the playback speed ratio v / v1 and the maximum playback power ratio P / P1 using the reference playback speed v1 and the maximum playback power P1 at the playback speed v1,
Determining the parameter n by fitting the reproduction speed ratio v / v1 and the maximum reproduction power ratio P / P1 with an approximate expression P / P1 = (v / v1) ⁿ ;
Calculating the target maximum reproduction power P from the approximate expression P / P1 = (v / v1) ⁿ using the target reproduction speed v, the reproduction speed v1, the maximum reproduction power P1, and the parameter n;
Setting the target maximum reproduction power P to the reproduction power at the target reproduction speed v;
A reproduction power adjustment method comprising: The reproduction power adjustment method according to claim 1,
The step of calculating the maximum reproduction power P at each reproduction speed v includes:
Determining a reproduction power P ′ that satisfies a target reproduction signal quality at a target reproduction possible time or reproduction possibility number at each reproduction speed v;
Determining the playback power P ′ as the maximum playback power P at each playback speed v;
A reproduction power adjustment method comprising: A method of adjusting the reproduction power of laser light for reproducing an optical information recording medium,
Calculating a maximum reproduction power P at each reproduction speed v;
Determining parameters α, n or α, n, β by fitting the playback speed v and the maximum playback power P with an approximate expression P = α × v ⁿ or P = α × v ⁿ + β;
Calculating a target maximum reproduction power P from the approximate expression P = α × v ⁿ or P = α × v ⁿ + β using the target reproduction speed v and the parameters α, n or α, n, β;
Setting the target maximum reproduction power P to the reproduction power at the target reproduction speed v;
A reproduction power adjustment method comprising: In the reproducing power adjustment method according to claim 3,
The step of calculating the maximum reproduction power P at each reproduction speed v includes:
Determining a reproduction power P ′ that satisfies a target reproduction signal quality at a target reproduction possible time or reproduction possibility number at each reproduction speed v;
Determining the playback power P ′ as the maximum playback power P at each playback speed v;
A reproduction power adjustment method comprising: A method of adjusting the reproduction power of laser light for reproducing an optical information recording medium,
Calculating a maximum reproduction power P at each reproduction speed v;
Calculating the playback speed ratio v / v1 and the maximum playback power ratio P / P1 using the reference playback speed v1 and the maximum playback power P1 at the playback speed v1,
Determining the parameter n by fitting the reproduction speed ratio v / v1 and the maximum reproduction power ratio P / P1 with an approximate expression P / P1 = (v / v1) ⁿ ;
A reproduction power adjustment method comprising: A method of adjusting the reproduction power of laser light for reproducing an optical information recording medium,
Calculating a maximum reproduction power P at each reproduction speed v;
Determining parameters α, n or α, n, β by fitting the playback speed v and the playback power P with an approximate expression P = α × v ⁿ or P = α × v ⁿ + β;
A reproduction power adjustment method comprising: When the maximum reproduction power at the reference reproduction speed v1 is P1, and the arbitrary reproduction speed v and the maximum reproduction power at the reproduction speed v are P, the reproduction speed ratio v / v1 and the maximum reproduction power ratio P / P1 Approximate expression P / P1 = (v / v1) The parameter n of the ⁿ , the reproduction speed v1 and the maximum reproduction power P1 are set in the management area of the optical information recording medium or information for reproducing the optical information recording medium Reading from the storage unit of the recording / reproducing apparatus;
Calculating the target maximum reproduction power P from the approximate expression P / P1 = (v / v1) ⁿ using the target reproduction speed v, the read reproduction speed v1, the maximum reproduction power P1, and the parameter n; ,
Setting the target maximum reproduction power P to the reproduction power at the target reproduction speed v;
Reproducing the optical information recording medium with the set reproduction power;
A reproduction power adjustment method comprising: Parameters α, n or α, n, β of an approximate expression P = α × v ⁿ or P = α × v ⁿ + β representing a relationship between an arbitrary playback speed v and the maximum playback power P at the playback speed v Reading from the management area of the optical information recording medium or the storage unit of the information recording / reproducing apparatus for reproducing the optical information recording medium;
A step of calculating the target maximum reproduction power P from the approximate expression P = α × v ⁿ or P = α × v ⁿ + β using the target reproduction speed v and the read parameters α, n or α, n, β. When,
Setting the target maximum reproduction power P to the reproduction power at the target reproduction speed v;
Reproducing the optical information recording medium with the set reproduction power;
A reproduction power adjustment method comprising: In an optical information recording medium having a data area and a management area,
When the maximum reproduction power at the reference reproduction speed v1 is P1, and the arbitrary reproduction speed v and the maximum reproduction power at the reproduction speed v are P, the reproduction speed ratio v / v1 and the maximum reproduction power ratio P An optical information recording medium in which the parameter n of the approximate expression P / P1 = (v / v1) ⁿ , the reproduction speed v1, and the maximum reproduction power P1 are recorded in the management area. In an optical information recording medium having a data area and a management area,
When an arbitrary playback speed v and the maximum playback power at the playback speed v are P, an approximate expression representing the relationship between the playback speed v and the maximum playback power P = α × v ⁿ or P = α An optical information recording medium, wherein parameters α, n or α, n, β of xv ⁿ + β are recorded in the management area. An information reproducing apparatus for reproducing an optical information recording medium by irradiating a laser beam,
The maximum reproduction power P at each reproduction speed v is calculated,
Using the playback speed v1 as a reference and the maximum playback power P1 at the playback speed v1, the playback speed ratio v / v1 and the maximum playback power ratio P / P1 are calculated,
The parameter n is determined by fitting the reproduction speed ratio v / v1 and the maximum reproduction power ratio P / P1 with an approximate expression P / P1 = (v / v1) ⁿ ,
Using the target reproduction speed v, the read reproduction speed v1, the maximum reproduction power P1, and the parameter n, the target maximum reproduction power P is calculated from the approximate expression P / P1 = (v / v1) ⁿ ,
Setting the target maximum playback power P to the playback power at the target playback speed v;
Reproducing the optical information recording medium with laser light having the set reproduction power;
An information reproducing apparatus characterized by that. An information reproducing apparatus for reproducing an optical information recording medium by irradiating a laser beam,
The maximum reproduction power P at each reproduction speed v is calculated,
Parameters α, n or α, n, β are determined by fitting the reproduction speed v and the reproduction power P with an approximate expression P = α × v ⁿ or P = α × v ⁿ + β,
Using the target reproduction speed v and the parameters α, n or α, n, β, the target maximum reproduction power P is calculated from the approximate expression P = α × v ⁿ or P = α × v ⁿ + β,
Setting the target maximum playback power P to the playback power at the target playback speed v;
Reproducing the optical information recording medium with laser light having the set reproduction power;
An information reproducing apparatus characterized by that. An information reproducing apparatus for reproducing an optical information recording medium by irradiating a laser beam,
When the maximum reproduction power at the reference reproduction speed v1 is P1, and the arbitrary reproduction speed v and the maximum reproduction power at the reproduction speed v are P, the reproduction speed ratio v / v1 and the maximum reproduction power ratio P The approximate expression P / P1 = (v / v1) representing the relationship of / P1 and the reproduction speed v1 and the maximum reproduction power P1 of ⁿ are reproduced from the management area of the optical information recording medium or the optical information recording medium. Read from the storage unit of the information recording and playback device,
Using the target reproduction speed v, the read reproduction speed v1, the maximum reproduction power P1, and the parameter n, the target maximum reproduction power P is calculated from the approximate expression P / P1 = (v / v1) ⁿ ,
Setting the target maximum playback power P to the playback power at the target playback speed v;
Reproducing the optical information recording medium with laser light having the set reproduction power;
An information reproducing apparatus characterized by that. An information reproducing apparatus for reproducing an optical information recording medium by irradiating a laser beam,
A parameter α, n or α, n, β of an approximate expression P = α × v ⁿ or P = α × v ⁿ + β representing a relationship between an arbitrary playback speed v and the maximum playback power P at the playback speed is Read from the management area of the optical information recording medium or the storage unit of the information recording / reproducing apparatus for reproducing the optical information recording medium,
Using the target reproduction speed v and the read parameters α, n or α, n, β, the target maximum reproduction power P is calculated from the approximate expression P = α × v ⁿ or P = α × v ⁿ + β,
Setting the target maximum playback power P to the playback power at the target playback speed v;
Reproducing the optical information recording medium with the set reproduction power;
An information reproducing apparatus characterized by that.

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