JP2007234165A - Recording power adjsuting method in optical recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording power adjusting method in an optical recording/reproducing device, capable of sufficiently absorbing an individual recording power difference in the optical recording/reproducing device. <P>SOLUTION: The recording power adjusting method for adjusting the recording power of a laser diode by executing trial-writing in the trial write area of an optical disk in the optical recording/reproducing device calculates a correlation coefficient of an n power equation for each recording power by plural types of recording powers set during trial writing and modulation m calculated from an RF signal of each recording power, selects a maximum n power values among the calculated correlation coefficients of the n power equations, creates a primary approximation equation from the selected optimal n power value, and calculates optimal recording power from the created primary approximation equation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical recording / reproducing apparatus, and more specifically to a method for adjusting laser power in a rewritable optical recording / reproducing apparatus.

  In recent years, there has been a remarkable spread of optical discs as recording media for digital information such as data, music or video. As this type of optical disk, for example, a write-once optical disk such as a CD-R, a rewritable optical disk such as a CD-RW, or a semiconductor laser as a laser light source with a shorter wavelength, a high NA objective having a high numerical aperture. Large-capacity optical disks such as DVD ± R, DVD ± RW, and DVD-RAM are known due to the reduction of the spot diameter by the lens and the adoption of a thin substrate.

  In this type of optical disc, information is recorded by a laser diode, but optimum recording parameters differ depending on differences in characteristics of optical discs and compatibility with optical disc apparatuses. That is, the optimum recording power of the laser diode is different for each manufacturer and for each medium even if they are of the same type. For this reason, in an optical recording / reproducing apparatus that records / reproduces data on / from an optical disk, trial writing is performed in the test area so that the recording power of the laser diode is optimized for each optical disk, and the recording power is adjusted based on the result. The idea to do is made.

  Among these optical discs, a rewritable optical disc such as CD-RW or DVD ± RW generally obtains the optimum recording power of a laser diode using a recording power adjustment method (γ method) based on a γ value. For example, it is recommended to use a linear fit method for DVD + RW standards and the like. In this linear fitting method, m * Pw is obtained from the recording power Pw of several kinds of laser diodes set at the time of trial writing and the modulation m of the reproduction reflected light intensity when the trial writing is performed with these recording powers Pw. . Then, a linear approximation line is created from the data plotted with the value of the recording power Pw on the horizontal axis and the value of m * Pw at that time on the vertical axis. This is a method of calculating the optimum recording power Pwo using γtarget and ρ.

  As described above, the linear fitting method is based on the premise that a linear approximation formula is established for the relational characteristic between the recording power Pw and m * Pw obtained by multiplying this value by the modulation factor m. And each measurement point is not linear and may be slightly curved. If there is such a curvature, the slope of the primary approximation line varies depending on the data used, so that the optimum recording power is not constant, and in some cases, a recording power that cannot be reproduced may be selected.

  Therefore, it is not possible to accurately perform linear approximation only by obtaining about a few m * Pw, and to obtain a high-precision recording power unless a significant number of trial writings and m * Pw operations are repeated. I knew that I couldn't. If the trial writing is repeated many times, the processing load at the time of adjustment for optimizing the recording power increases, and the adjustment time becomes longer.

For this reason, for example, Patent Document 1 discloses a conventional technique capable of obtaining the optimum recording power with relatively high accuracy even with a small number of trial writings. That is, in this prior art, as shown in FIG. 20, instead of m * Pw, a m * Pw ^binary value obtained by multiplying the modulation degree m by the square of the recording power Pw is used as the vertical axis of the graph. (The horizontal axis remains the recording power Pw), the recording power is optimized with relatively high accuracy even with a small number of trial writings.
JP 2005-209287 A

  However, in the technique disclosed in Patent Document 1, it is possible to stably optimize the recording power rather than using the linear fit method as it is. It has been found through experiments and the like that it may not be able to absorb sufficiently.

  It is an object of the present invention to provide a recording power adjustment method in an optical recording / reproducing apparatus that can sufficiently solve the individual recording power differences of the optical recording / reproducing apparatus, and solves the problems of the prior art.

In order to solve the above-mentioned problems, the present invention provides a recording power adjustment method in an optical recording / reproducing apparatus for adjusting the recording power of a laser diode by performing test writing in a test writing area of an optical disc. A multiple value m * of a plurality of types of recording power Pw set at the time of trial writing and a modulation m calculated from an RF signal at each recording power Pw and the nth power (n ≧ 2) of the recording power Pw. pw ⁿ and the from the relationship of a n-th power of the recording power (n ≧ 2) Pw ^n, the recording power adjustment method in the optical recording and reproducing apparatus characterized by creating a first order approximation equation.

  According to a second aspect of the present invention, in the recording power adjustment method according to the first aspect, the n-th power value having the strongest correlation is selected from the calculated correlations of the n-th power formula, and the selected n A primary approximation formula is created from the multiplier value, and the optimum recording power Pwo is calculated from the created primary approximation formula.

According to a third aspect of the present invention, in the recording power adjustment method according to the second aspect, the P threshold Pthr necessary for calculating the optimum recording power Pwo is obtained when the primary approximate line is y = ax + b. And Pthr = − (b / a) ^{(1 / n)} .

  According to a fourth aspect of the present invention, in the recording power adjusting method according to the second aspect, the optimum recording power Pwo is obtained by selecting a P threshold Pthr obtained from a selected n-th power value and a coefficient kappa κ obtained for each optical disc. It is characterized by calculating by integrating | accumulating.

  In the optical recording / reproducing apparatus for adjusting the recording power of the laser diode by performing trial writing on the trial writing area of the optical disc, the invention described in claim 5 includes a plurality of types of recording power Pw set at the time of trial writing, A calculating means for calculating the correlation of each n-th power expression from the modulation m calculated from the RF signal at each recording power Pw, and the n-th power having the strongest correlation among the correlations of each n-th power expression calculated by the calculating means. A first-order approximation formula creating means for selecting a value and creating a first-order approximation formula using the selected optimum n-th power value, and an optimum recording power calculation for calculating the optimum recording power Pwo from the first-order approximation formula created by the first-order approximation formula creation means. Means.

  According to the present invention, an n-th power value that can create an optimal first-order approximation expression for each optical disc is selected. For this reason, when the rewritable optical disc test writing (OPC: Optimum Power Calibration) operation is performed in a range that fully considers the individual recording power differences of the optical recording / reproducing device, and the recording power is calculated with a predetermined number of data Therefore, it is possible to obtain an optimum recording power with higher accuracy than in the prior art. Further, in the present invention, it is possible to obtain an optimum recording power with higher accuracy by using kappa κ obtained for each optical disc without using γ target and ρ which are optical disc information.

Next, an embodiment of a recording power adjusting method in an optical recording / reproducing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
Referring to FIG. 1, there is shown a functional block diagram of an optical recording / reproducing apparatus according to the present invention. The optical disc 1 is a recording medium on which information can be recorded, reproduced, and erased (only RW and RAM) by a semiconductor laser, and examples thereof include CD-R, CD-RW, DVD ± R, DVD ± RW, and DVD-RAM. .

  The spindle motor 200 is a motor that rotates the optical disc 1 and rotates it at a constant linear velocity or constant angular velocity. The rotation speed of the spindle motor 200 is controlled by a driver 208.

  The optical pickup device 202 is a device for irradiating the recording surface of the optical disc 1 on which a track is formed with laser light and receiving reflected light from the recording surface. The optical pickup device 202 includes a drive system such as a laser diode, a collimator lens, a beam splitter, an objective lens, a detection lens, a light receiver, a focus actuator, and a tracking actuator.

  A stepping motor 206 is a motor that drives the slider 207 to move the optical pickup device 202 in the track direction. Similar to the spindle motor 200, the stepping motor 206 is driven and controlled by a driver 208.

  The analog front end 210 is a signal processing circuit for shaping a detection signal from the optical pickup device 202 into a digital signal. The detection signal itself from the optical pickup device 202 is analog, and the detected level is minute and unstable. For this reason, the threshold value for amplifying and aligning the level in the analog front end 210 and for converting it to a beautiful square wave is constantly adjusted. When the analog front end 210 receives the amount of reflected light from the optical disc 1 during recording from the optical pickup device 202, the analog front end 210 notifies the MPU 220 of the level.

  The digital signal processing circuit 212 generates an RF signal indicating the total amount of reflected light to each region of the photo detector, and uses the astigmatism method to generate a focus error signal, which is a signal that detects the defocus of the irradiation laser of the optical pickup device 202. Further, a tracking error signal, which is a signal obtained by detecting the track deviation of the irradiation laser of the optical pickup device 202, is generated by the push-pull method. Further, based on the generated focus error signal and tracking error signal, a focus drive signal and a tracking drive signal are generated and output to the driver 208.

  Further, upon receiving a control command for the spindle motor 200, the optical pickup device 202 or the stepping motor 206 from the MPU 220, the digital signal processing circuit 212 outputs it to the driver 208. When these error signals and control commands are input, the driver driver 208 performs drive control of the spindle motor 200, the optical pickup device 202, and the stepping motor 206.

  An encoder / decoder 214 encodes information to be recorded on the optical disc 1 sent from the personal computer 3 and outputs the encoded information to the digital signal processing circuit 212. The encoder / decoder 214 also decodes the information read by the optical disc 1 to personalize the information. This is a circuit to be sent to the computer 3.

  The buffer memory 216 is a memory that temporarily stores information exchanged with the personal computer 3. The host interface 218 is an interface for connecting to the personal computer 3 at a physical level and a signal level.

  The MPU 220 is a main CPU that controls the entire optical disc apparatus in accordance with programs and data (firmware) stored in the flash memory 222. In this embodiment, the MPU 220 has a function of adjusting the recording power Pw in the laser diode of the optical pickup device 202 by performing trial writing in the trial writing area of the optical disc in addition to the control of the normal optical disc device. Specifically, it has a calculation function for calculating a correlation coefficient of each n-th power equation from a plurality of types of recording power set at the time of trial writing and a modulation m calculated from an RF signal at each recording power, It has a function of creating a first-order approximate expression using the largest n-th power value from the numbers (the n-th power value having the strongest correlation among the correlations) and calculating the optimum recording power therefrom. The MPU 220 also has a function of calculating a correlation coefficient and a P threshold Pthr.

  The flash memory 222 is a memory in which programs and data necessary for the operation of the MPU 220 are stored as described above. The flash memory 222 also temporarily stores data used for calculating the optimum recording power, correlation coefficient, kappa κ, and the like. The flash memory 222 further stores data relating to the write strategy, recording power Pws set by the write strategy designer, and the like.

  2 to 4 are flowcharts showing an embodiment of a recording power adjusting method in the optical recording / reproducing apparatus according to the present invention. Hereinafter, the operation in this embodiment will be described with reference to these drawings.

  FIG. 2 is an operation flow for the strategy designer to determine the optimal n-th power value and kappa κ for each optical disc. First, the start and end points of the recording power of the laser diode are set. This sets + 15% to -45% as the start point and end point with respect to the recording power Ps set by the write strategy designer (step S100). In this specification, the recording power Pw means the power of the peak Pw of the pulse shown in FIG.

Next, the starting point and the ending point set in step S100 are divided using 18 steps as a guide, and the recording power Pw interval is set (step S102). Test writing is performed in the OPC area with the recording power Pw set at the interval set in step S102, and the modulation signal m is read by reading the RF signal (step S104). FIG. 6 illustrates the waveform of the RF signal for explaining the calculation of the modulation m. In FIG. 6, when the strongest RF signal from the reference level 0 is I14H and the weakest RF signal is I14L, the modulation m is
m = (I14H-I14L) / I14H
Can be obtained.

Once the modulation m is calculated, the correlation coefficient is calculated (step S106). After calculating the modulation m, FIG. 7 shows the data that satisfies 0.2 ≦ m with the recording power of 18 steps set in step S102 and the vertical axis is m * Pw ⁿ and the horizontal axis is Pw ⁿ from the lower limit data. The graph is plotted as described above to obtain a linear approximation straight line y = ax + b. This graph plot is performed, for example, from the second power to the tenth power, and each correlation coefficient is calculated.

The a and b of the linear approximation line and the correlation coefficient are obtained by the following formula.
If the linear approximation line is y = ax + b,

で求められる。

Is required.

  From this, the correlation coefficient is calculated by the following equation.

When the correlation coefficients from the second power to the tenth power are calculated in step S106, the nth power value of the correlation coefficient that is the maximum is selected (step S108). When the nth power of the correlation coefficient that is the maximum is selected in step S108, the P threshold Pthr is calculated (step S110). Specifically, since the slope a and the intercept b of y = ax + b can be obtained from the above formula, the P threshold Pthr is
Pthr =-(b / a) ^{(1 / n)}
Where n is the selected nth power value.

When the P threshold Pthr is obtained in step S110, the kappa κ is obtained from this value and the standard power Pws. The formula for calculating kappa κ is
κ = Pws / Pthr
It becomes. Here, the standard power Pws is determined by evaluating the DOW (Direct Over Write) characteristics shown in FIG. 8 in advance. In FIG. 8, for ease of understanding, assuming that the error rate specification is 280 (straight line L1), DOW (0), DOW (1), DOW (10), DOW (100), DOW (1000) ( Each of the parentheses indicates the number of times of overwriting), and a specific example when plotting the data into a graph is shown.

  In the graph of FIG. 8, error rate data E1 means error rate data when DOW (overwrite) is performed once with a recording power of 16.5 mw, and error rate data E2 is 1000 times DOW (overlapping) with a recording power of 22 mw. It means error rate data at the time of writing. Since the error rate specification is 280 or less, the recording power lower limit value P1 and the recording power upper limit value P2 at which the DOW (1) curve and the DOW (1000) curve are in contact with the straight line L1 are the limit values of the recording power Pw. Since the recording power lower limit P1 is 16.8 mw and the recording power upper limit P2 is 21.2 mw, the standard power Pws is 19 mw from Pws = (P1 + P2) / 2. Therefore, for example, when the P threshold Pthr is 12.71, kappa κ is 1.495 from κ = 19 / 12.71.

  Next, an example of the operation of the embodiment of the recording power adjustment method according to the present invention will be described with reference to FIGS. The operation flow described below is a process for determining the optimum recording power Pwo actually performed in the optical recording / reproducing apparatus after the optimum n-th power value and kappa κ shown in FIG. 2 are determined. . In FIG. 3, steps S200 to S204 are the same as steps S100 to S104 in FIG.

  FIG. 9 shows data obtained by actual recording and measurement / calculation of the optical recording / reproducing apparatus #A when Pws in step S200 is assumed to be 20 mv, kappa κ is 1.51, and the optimum n-th power value is 5th power. As shown in step S202, the recording power Pw interval is 18 steps. Step S206 shows processing for obtaining, as temporary optimum recording power Pwt (Pwt = Pthr * κ), upper limit data that can be used for calculating the optimum recording power Pwo from the data shown in FIG.

  Step S208 is a process for determining whether or not the number of data conditions that can be used from the data shown in FIG. Here, as a lower limit value of data, whether the value of modulation m satisfies 0.2 ≦ m, and whether or not there are four or more data satisfying the selection condition that the recording power Pw is equal to or less than the provisional optimum recording power Pwt (Pw ≦ Pwt). Judging.

  If there are four or more data satisfying the selection condition based on the determination result of step S208, the process proceeds to step S214, and if not, the process proceeds to step S210. In step 210, if the number of retries is less than one (No), the process proceeds to step S212, the recording power Pw is reset, and the process returns to step S202. On the other hand, if the number of retries is 1, it is determined whether or not it is a known optical disk (step S230). If it is a known optical disk, the registration Pws is set as Pwo (step S232). If it is not a known optical disc, the recording power acquired from the disc information of the optical disc is set as Pwo (step S234).

  Returning to step S214, in this process, it is determined whether the correlation coefficient calculated from the data satisfying the selection condition of step S208 is 0.9 or more. If the correlation coefficient ≧ 0.9, the optimum recording power Pwo is calculated with all data satisfying the optimum recording power Pwo calculation data selection condition (step S216), and this is set as the optimum recording power Pwo (step S218).

  That is, the P threshold Pthr is obtained from the slope (a) and the intercept (b) of the primary approximation formula from the data shown in FIG. When the actual measurement data shown in FIG. 9 is plotted on a graph, the actual values are different, but the data distribution is very close to a straight line as shown in FIG. 13 or FIG. .

Since the kappa κ is fixed, the optimum recording power Pwo can be calculated as Pwo = Pthr * κ if the P threshold Pthr is obtained. FIG. 10 shows each calculation item (gradient (a) / intercept (b) of primary approximation, correlation coefficient, P threshold) calculated in step S216 from data shown in FIG. The values of the thresholds Pthr and Pthr ^(1/5) and the optimum recording power Pwo are shown, and Figures 11 and 12 show the optical recording / reproducing apparatus #A and the optical recording / reproducing apparatus #A having different power characteristics of the laser diode. The actual measurement data and calculation result of B are shown.

  In both the optical recording / reproducing apparatus #A and the optical recording / reproducing apparatus #B, the standard power Pws for setting the recording power start point / end point is set to 20 mw, and the kappa κ is set to 1.51. From these results, even when the standard recording power Pws and kappa κ values set by the strategy designer are the same, the value of the modulation m differs depending on the individual difference of the optical recording / reproducing apparatus, and the value of the optimum recording power Pwo differs. I understand.

  FIG. 15 shows the optical recording / reproducing apparatus #A that is actually measured data in FIG. 9 and the optical recording / reproducing apparatus #B that is actually measured data in FIG. It is a graph of. As is clear from FIG. 15, the jitter is stable from the vicinity of the optimum recording power Pwo = 19.93 (see FIG. 10) in the graph of the optical recording / reproducing apparatus #A, and the optimum recording power in the graph of the optical recording / reproducing apparatus #B. It can be seen that the jitter is stable from around Pwo = 18.64 (see FIG. 12). Therefore, it can be understood that the recording power at which the jitter value begins to stabilize can be calculated as the optimum recording power Pwo in both optical recording and reproducing apparatuses.

  Returning to step S214, if the value of the correlation coefficient is smaller than 0.9, the data is deleted one by one from the upper data having a large modulation m, and this is repeated until the value of the correlation coefficient becomes larger than 0.9 (step S220). , S222). When correlation coefficient ≧ 0.9 is satisfied in step S222, it is determined whether or not there are four or more pieces of valid data after deletion as in step S208 (step S224). If there are four or more pieces of valid data after deletion, the optimum recording power Pwo is calculated (step S226), and the calculated optimum recording power Pwo is set (step S218).

  In step S224, if the number of valid data is less than 4, it is determined whether the number of retries is one (step S228). If the number is one, the process of step S230 described above is performed. On the other hand, if the number of retries is not 1, the process returns to step S200 to reset the recording power start point / end point.

  Next, the difference in effect between Patent Document 1 described in “Background Art” and the present embodiment will be described based on experimental examples. FIG. 16 and FIG. 18 show data collected by two optical recording / reproducing apparatuses (# 1 and # 2) under the same conditions for Patent Document 1 as a prior application patent and the present proposal as the present embodiment. is there. As conditions for evaluation comparison of these data, the P threshold Pthr (A) was calculated by setting the continuous 5 data as the range A from the data where the value of the modulation m was 0.2 or more. Also, the Pth threshold Pthr (B) was calculated by setting the sixth to tenth data from the data in which the value of the modulation m was 0.2 or more as the range B.

  FIG. 17 shows the difference between the prior patent in the optical recording / reproducing apparatus # 1 shown in FIG. 16 and the present proposal, and FIG. 19 shows the difference between the prior patent in the optical recording / reproducing apparatus # 2 shown in FIG. It shows the difference from this proposal. In both FIG. 17 and FIG. 19, ΔPthr, which is the difference between the P threshold Pthr (A) in the range A and the P threshold Pthr (B) in the range B, is smaller than that of the prior patent. As a result, the effectiveness of the proposal can be confirmed.

  As described in detail above, according to the present embodiment, by selecting the n-th power value that maximizes the correlation coefficient, it is possible to collect data with the most linearity within the range of valid data. Even if the range of valid data used for the calculation is different, there is almost no difference in the value of the P threshold Pthr, and as a result, the ideal optimum recording power Pwo can be set.

The functional block diagram which shows embodiment of the recording power adjustment method in the optical recording / reproducing apparatus by this invention. The operation | movement flow for determining the n-th power value and kappa (kappa) optimal for every optical disk in this Embodiment. Operation flow part 1 until the optimum recording power Pwo is set in the optical recording / reproducing apparatus in the present embodiment. Operation flow part 2 until the optimum recording power Pwo is set in the optical recording / reproducing apparatus in the present embodiment. Explanatory drawing for demonstrating recording power Pw. The wave form diagram which showed an example of RF signal when calculating | requiring the modulation m. The graph example in this Embodiment when the data are plotted when the vertical axis is m * Pw ⁿ and the horizontal axis is Pw ⁿ . The graph example which plotted the data when DOW was performed in order to obtain | require standard recording power Pws. Data example when actual measurement data of optical recording / reproducing apparatus #A is collected by applying this embodiment. The calculation example which showed the calculation result of calculation items, such as optimal recording power Pwo, based on the data of FIG. An example of data when actual measurement data of the optical recording / reproducing apparatus #B is collected by applying this embodiment. The calculation example which showed the calculation result of calculation items, such as optimal recording power Pwo, based on the data of FIG. The graph example when graph plotting the data when the n-th power value in this Embodiment is made into the 5th power. The other example of the graph when the data when the n-th power value in this Embodiment is made into the 5th power is graph-plotted. Explanatory drawing for demonstrating the effectiveness of this Embodiment which made the relationship between the jitter value and recording power in optical recording and reproducing apparatus #A and optical recording and reproducing apparatus #B a graph. An example of data when data is collected under the same conditions as those of the prior application and the present embodiment in the optical recording / reproducing apparatus # 1. FIG. 16 is an explanatory diagram showing the effectiveness of the present embodiment by calculating the P threshold Pthr in the prior application and the present embodiment in the ranges A and B and the difference ΔPthr from the data shown in FIG. . An example of data when data is collected under the same conditions in the optical recording / reproducing apparatus # 2 as in the previous application and in the present embodiment. 18 is an explanatory diagram showing the effectiveness of the present embodiment by calculating the prior application in the ranges A and B and the P threshold Pthr in the present embodiment from the data shown in FIG. 18 and showing the difference ΔPthr. . The graph which showed an example when the data calculated | required in the prior art was plotted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Optical disk apparatus 3 Personal computer 200 Spindle motor 202 Optical pick-up apparatus 206 Stepping motor 208 Driver 210 Analog front end 212 Digital signal processing circuit 214 Encoder / decoder 216 Buffer memory 218 Host interface 220 MPU
222 flash memory

Claims (5)

In the recording power adjustment method in the optical recording / reproducing apparatus for adjusting the recording power of the laser diode by performing trial writing in the trial writing area of the optical disc,
A value obtained by multiplying a plurality of types of recording power Pw set at the time of the trial writing and the modulation m calculated from the RF signal at each recording power Pw by the nth power of the recording power Pw (n ≧ 2). m * Pw ⁿ and the from the relationship of a n-th power of the recording power (n ≧ 2) Pw ^n, the recording power adjustment method in the optical recording and reproducing apparatus characterized by creating a first order approximation equation. The recording power adjustment method according to claim 1,
The n-th power value having the strongest correlation is selected from the calculated correlations of the n-th power formulas, and a first-order approximation formula is created from the selected n-th power values,
A recording power adjustment method in an optical recording / reproducing apparatus, wherein an optimum recording power Pwo is calculated from the created primary approximation formula. 3. The recording power adjustment method according to claim 2, wherein the P threshold Pthr necessary for calculating the optimum recording power Pwo is obtained when the primary approximate line is y = ax + b.
Pthr =-(b / a) ^{(1 / n)}
The recording power adjustment method in the optical recording / reproducing apparatus, characterized in that   3. The recording power adjustment method according to claim 2, wherein the optimum recording power Pwo is calculated by integrating the P threshold Pthr obtained from the selected n-th power value and the coefficient kappa κ obtained for each optical disc. A recording power adjusting method in an optical recording / reproducing apparatus. In an optical recording / reproducing apparatus that adjusts the recording power of a laser diode by performing trial writing in a trial writing area of an optical disc,
Calculating means for calculating a correlation of each n-th power type from a plurality of types of recording power Pw set at the time of the trial writing and a modulation m calculated from an RF signal at each recording power Pw;
A primary approximation formula creating means for selecting the n-th power value having the strongest correlation from the correlations of the respective n-th power formulas calculated by the calculation means, and creating a primary approximation formula using the selected optimal n-th power value;
An optical recording / reproducing apparatus comprising: an optimum recording power calculating means for calculating an optimum recording power Pwo from the primary approximation formula created by the primary approximation formula creating means.

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