JP2006196126A - Focus-controlling method of optical disk and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten adjustment time while keeping practical precision when a focus offset value is set to a disk capable of recording data on its land part and groove part. <P>SOLUTION: A focus offset value, which is a target value at the time of focus control, is changed in a prescribed range. Under each focus offset value, recorded signals are reproduced from a prescribed section 33 including the land part 31a and groove part 31b of an optical disk, and the reproduced signals 34 are averaged across the prescribed section. A focus offset value (F<SB>0</SB>) 43 having the best qualities of the averaged reproduced signals is found, and the found focus offset value is set as the common target value of the land part and groove part to perform focus control. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc focus control method and an optical disc apparatus capable of recording data in both a land portion and a groove portion.

  An optical disk track is composed of a light beam guide track groove portion (groove portion) and a light beam guide track groove portion (land portion). In a recording medium such as a DVD-RAM, data is stored in both the land portion and the groove portion. Record. In such a disc, since the focus point is different between the land portion and the groove portion, when the focus servo control is performed based on one focus error signal, the optimum recording is performed for the recording data of the land portion and the groove portion. It was supposed to be impossible to play.

  Therefore, a method has been proposed in which the focus servo control signal is switched and optimized for each tracking of the land portion and the groove portion (see, for example, Patent Document 1). In other words, the focus offset value for the land and groove parts is changed stepwise to perform test playback of the signal, and the optimum focus offset from the conditions that maximize the reproduced signal or conditions that minimize the error rate. Each value is obtained, and these values are set as focus offset values (target values) at the time of recording / reproduction of the land portion and the groove portion.

JP-A-8-180429

  According to the above prior art, since the optimum focus offset value is individually measured for each of the land portion and the groove portion, the setting accuracy can be improved. However, when the measurement value is analyzed by a microcomputer or the like, a certain number of samples are required in order to reduce the measurement error due to the sampling timing. In addition, since each of the land portion and the groove portion is measured, the entire measurement time becomes long, and it is difficult to shorten the adjustment time.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disc capable of reducing adjustment time while maintaining practical accuracy when setting a focus offset value for a disc capable of recording data in both a land portion and a groove portion. Focus control method and optical disc apparatus are provided.

  An optical disc focus control method according to the present invention changes a focus offset value, which is a target value in focus control, within a predetermined range, and includes a predetermined portion including a land portion and a groove portion on the optical disc under each focus offset value. The recorded signal is reproduced from the section, the reproduced signal is averaged over the predetermined section, and the focus offset value that gives the best quality of the averaged reproduced signal is obtained. Focus control is performed by setting a common target value for the grooves.

  Preferably, the predetermined section is a section including a land portion and a groove portion having the same length, straddling a switching position between the land portion and the groove portion.

  Further, a focus offset value that minimizes the jitter amount is obtained for the averaged reproduction signal, and this is set as a target value for focus control.

  An optical disc apparatus according to the present invention includes an offset adjusting unit that changes a focus offset value, which is a target value in focus control, within a predetermined range, and a predetermined portion including a land portion and a groove portion on the optical disc under each focus offset value. The signal reproduction means that reproduces the recorded signal from the interval of time and averages it over a predetermined interval, and obtains the focus offset value that gives the best quality of the averaged reproduction signal, and calculates the value of the land portion and groove portion. Offset setting means for setting a common target value for focus control and focus control means for performing focus control based on the set target value are provided.

  According to the present invention, it is possible to suitably and quickly execute focus adjustment on a disk on which data is recorded in both the land portion and the groove portion, so that convenience for the user is improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of an optical disk apparatus according to the present invention.

  The optical disc 1 is a disc medium such as a DVD-RAM that can record signals in a land portion and a groove portion. The optical pickup 2 irradiates the optical disc 1 with laser light to record or reproduce signal data.

  A configuration for performing focus adjustment prior to data recording / reproduction will be described. The optical pickup 2 reads a signal already recorded on the optical disc 1, and the binarization circuit 3 slices it at a predetermined level and converts it into a binary pulse signal. The phase comparator 4 and the voltage controlled oscillator (VCO) 5 constitute a PLL loop, compare the output signal pulse of the binarization circuit 3 with the reference clock, and obtain the phase difference. The phase difference output integrator 6 integrates the absolute value of the phase difference of each pulse for a predetermined period. The jitter detector 7 detects the amount of jitter from the output of the phase difference output integrator 6.

  The system control microcomputer 8 analyzes the output of the jitter detector 7 and determines a focus offset value that minimizes the jitter amount. Therefore, the change in the amount of jitter is measured by changing the focus offset value. In the measurement, the adjustment range and the number of adjustment steps of the focus offset value are stored in advance in the focus offset adjustment table, and the address position on the disk for performing the focus offset adjustment is stored in the address setting table. When the focus offset value that minimizes the jitter amount is obtained, it is set in the adder 10 as the optimum offset value (target value of the focus error signal).

  At the time of data recording / reproduction, the focus error generation circuit 9 generates a focus error signal from the signal read by the optical pickup. The focus error signal is generated by, for example, the astigmatism method, but is not limited thereto. The focus servo circuit 11 drives the actuator to perform focus servo control of the optical pickup 2 so that the focus error signal at the time of recording / reproduction coincides with the focus offset target value.

  In this embodiment, the focus offset optimization adjustment, which has been performed separately for each land and groove, is performed once for a disk in which data is recorded on both the land and groove such as a DVD-RAM. Is what you do. Therefore, in the address setting table for adjusting the focus offset, the measurement section on the disk straddles the land / groove switching point, and the measurement section has the same length in the land section and the groove section. An address is set. Then, the measurement values are averaged (integrated) within the interval, an appropriate focus offset value is determined for both the land portion and the groove portion, and the value (single value) is set in the adder 10. Thereby, the time of measurement conventionally performed in both the land portion and the groove portion can be halved.

  Conditions for executing the offset adjustment operation are stored in a focus offset adjustment table and an address setting table in the system control microcomputer 8. The focus offset adjustment table stores the focus offset adjustment range and the adjustment step width (number of steps) based on the defocus variation specifications of the optical pickup to be used. For example, the adjustment range is determined to be 6 μm and the step width is approximately 0.2 μm. In order to obtain the optimum position where the amount of jitter is minimized, the accuracy can be improved by further using an interpolation method.

  The address setting table stores the address position on the disk for adjusting the focus offset. In the case of a DVD-RAM, it is preferable to use an inner circumference DMA (Defect Management Area) area in which data is already recorded. Of course, other areas can be used as long as data is recorded.

  FIG. 3 is a diagram for explaining the jitter measurement position in this embodiment.

  The DVD-RAM employs a so-called single spiral system in which land portions 31a and groove portions 31b are alternately formed on one track. Therefore, an address 32 that spans the land / groove switching point 33c is designated as the measurement position on the disc, and the measurement section 33 is set so that the length of the land section 33a and the groove section 33b are the same length. To do. Although the level of the jitter detection voltage 34 obtained in the land portion and the groove portion is naturally different, the average jitter voltage for both the land portion and the groove portion can be easily obtained by making the land interval and the groove interval the same length. .

  The length of the measurement section 33 is appropriately about 10 ms in consideration of the measurement error due to the timing of sampling the jitter voltage. This corresponds to about 14 sectors when converted at the inner peripheral position of the DVD-RAM 1 × speed. Then, several address positions are set on the disk where measurement can be performed for 7 sectors on the land side and 7 sectors on the groove side. In the DVD-RAM, the land / groove switching position exists for each rotation of the disk, and is selected from these positions.

  As a specific example, among the DMA area addresses 30F80h to 30FFFh, 14 sectors centering on the land / groove switching point 30F87h, that is, 30F80h to 30F8Eh are set as measurement positions. In addition, in order to prevent the normal adjustment in this part, a plurality of measurement positions are set in the address setting table, such as setting 14 sectors centered on the next land / groove part switching point 30FA0h. To set.

  FIG. 4 is a diagram for explaining determination of the optimum focus offset value in the present embodiment.

  The focus offset value is changed and the jitter voltage obtained at that time is used as an index for adjustment. The jitter voltage is obtained by integrating the phase difference output of the phase comparator 4. The better the focus state, the smaller the fluctuation of the reproduction pulse position, and the better the jitter characteristic and the lower the jitter voltage.

The land-side jitter voltage 41 and the groove-side jitter voltage 42 have different characteristics (translation in the horizontal axis direction) with respect to the focus offset value. In this embodiment, a jitter voltage 40 obtained by averaging these is obtained. Then, the focus offset value F ₀ that minimizes the average jitter voltage 40 is determined as the optimum offset value 43. The determination of the optimum value may not be the position where the jitter voltage 40 is minimum as long as the allowable level 44 or less. In addition, when the adjustment step width is rough, the optimal position may be unclear. In that case, if the measurement result is approximated by a quadratic function, and the position where the jitter is minimized is obtained by the interpolation method, setting with higher accuracy can be performed.

Thus, in this embodiment, an appropriate focus offset value is determined for both the land portion and the groove portion, and the value F ₀ (single value) is set as a common target value for focus control. In the present embodiment, both the land portion and the groove portion are controlled by a single value, but a target value determined based on the characteristics of either the land portion or the groove portion as in the past is commonly used. Therefore, it is practically possible to expect accuracy that satisfies the conditions of both the land portion and the groove portion. This method is a more effective method in combination with an improvement in recording sensitivity of the recording disk expected in the future and an improvement in reproduction signal processing technology (error correction).

  FIG. 2 is a flowchart illustrating an example of focus offset adjustment in the present embodiment. In step S21, offset adjustment is started. Hereinafter, adjustment is performed with the focus servo and tracking servo applied.

  In step S22, the focus offset adjustment range is read from the focus offset adjustment table, and the focus offset value of the optical pickup is set to its initial value. In step S23, the designated address 32 is read from the address setting table, and in the case of the above example, it moves to the address 30F80h. In step S24, the jitter voltage in the 14 sector section is sampled and measured, and an average value (integrated value) is obtained and stored in the memory in the system control microcomputer 8. In step S25, it is determined whether or not the jitter voltage measurement has been completed for the entire focus offset adjustment range. If not completed, in step S26, the focus offset value is changed (increased) by a predetermined adjustment step width, and the above steps S23 and S24 are repeatedly executed to obtain the average value of the jitter voltage and store it in the memory. To do.

When the measurement of the jitter voltage is completed for the entire focus offset adjustment range, a focus offset value F ₀ that minimizes the average jitter voltage is obtained in step S27. When determining the F ₀ value, an interpolation method (quadratic function approximation) is used together as necessary. At step S28, it sets the focus offset value F ₀ obtained as a land portion at the time of focus control and the focus offset target value at the grooves both. In step S29, the offset adjustment ends. Thereafter, focus servo control during recording or reproduction is performed under this adjustment condition.

  As described above, according to the present embodiment, the focus offset optimization adjustment, which has been conventionally performed separately for the land portion and the groove portion, can be performed by a single adjustment, so that the time for initial adjustment can be shortened. . Moreover, the setting can be commonly used for control of both the land portion and the groove portion.

  As a modification of the present embodiment, the jitter voltage measurement section does not necessarily include the land / groove switching point. That is, sampling may be performed so as to include a land portion and a groove portion that are separated from each other on the disk by the same length, and these may be averaged.

  Furthermore, the length of the land portion and the groove portion included in the measurement section may not be the same length. If these are not equal, the minimum position of the measured jitter voltage is calculated by using the ratio of the step between the land and the groove and the length between the land and the groove. Can be corrected to the position where they are equal.

  Further, when obtaining the optimum focus offset value, it may be determined from the condition that the reproduction quality of the reproduction signal is the best. Therefore, as an index other than the above-described jitter amount, a condition that maximizes the RF amplitude (high frequency amplitude) and a condition that minimizes the number of PI (Parity Innercode) and PO (Parity Outercode) error corrections can be employed.

  In the first embodiment, an appropriate focus offset value is determined for both the land portion and the groove portion from the average value in the measurement section, and the value (single value) is used for focus control of the land portion and the groove portion. It was set to a common target value. On the other hand, in this embodiment, the focus offset is adjusted by one adjustment, but the target value of the focus control is set individually for each of the land portion and the groove portion (binary control). . The configuration of the apparatus is the same as in FIG. 1, and the measurement of the jitter voltage for each focus offset value is the same as in FIG.

FIG. 6 is a diagram for explaining determination of the optimum focus offset value in the present embodiment. From the measurement result of the average voltage of the land portion and the groove portion, the focus offset value F _{0 at} which the average jitter voltage 40 is minimized is determined. Next, two values F ₁ (= F ₀ + d / 2) and F ₂ (= F ₀ −d / 2) obtained by increasing / decreasing the predetermined width d / 2 around the value F ₀ are calculated, and the optimum offset value is calculated. 43a and 43b. Then, set the F ₁ land side, the F ₂ to the target value of the focus control groove portion. Here, the predetermined value d is a value determined according to the level difference between the land portion and the groove portion. For example, in DVD-RAM, this step d is about 70 nm, and in the above calculation, this mechanical step may be used as it is. Preferably, however, a reproduction signal is detected from the land portion and the groove portion, and the focus of both is detected. It is more accurate to obtain a positional deviation (electrical step value) in advance and use that value.

The control (binary control) of this embodiment is practically used when the minimum level J ₀ of the measured average jitter voltage 40 is larger than the allowable value level 44 of the jitter voltage. By using binary control, the jitter voltage of the land portion and the groove portion can be within an allowable range, recording / reproduction performance is ensured, and adjustment (measurement) work can be performed only once. There is a shortening effect.

FIG. 5 is a flowchart illustrating an example of focus offset adjustment employing the present embodiment (binary control). From step S21 to step S27 (determining the focus offset value F ₀ of the average jitter voltage is minimized) is omitted because it is identical to the procedure of FIG. 2.

In step S30, it determines the average jitter voltage J ₀ whether acceptable. If within the allowable range, in step S31, it sets the focus offset value F ₀ as lands and grooves common focus offset target value (1 value control).

If it is not within the allowable range, optimum focus offset values F ₁ and F ₂ for the land portion and the groove portion are calculated from the focus offset value F ₀ in step S 32. In this calculation, a step value (electrical step) d between the land portion and the groove portion is used. In step S33, the calculated F ₁ and F ₂ values are set as target values for the land portion and the groove portion (binary control).

In this embodiment, to determine the average jitter voltage J ₀ whether within the allowable range, switches the control method (1 value control and binary control), it is possible to prevent deterioration of the recording and reproducing characteristics in advance .

  In the case of the present embodiment, as a modification, the jitter voltage measurement section may be sampled so as to include only the same length of the land portion and the groove portion separated on the disk, and this may be averaged.

  Furthermore, the lengths of the land portion and the groove portion included in the measurement section do not have to be the same length, and are measured by using the step d between the land portion and the groove portion and the ratio of the length between the land portion and the groove portion. It is possible to calculate the optimum focus offset values of the land portion and the groove portion from the minimum position of the jitter voltage.

  In addition to the above-described jitter voltage, conditions for maximizing the RF amplitude and conditions for minimizing the number of PI and PO error corrections can be employed for quality evaluation of the reproduction signal.

1 is a block diagram showing an embodiment of an optical disc apparatus according to the present invention. 6 is a flowchart showing an example of focus offset adjustment in the present invention. The figure explaining the jitter measurement position in FIG. The figure explaining determination of the optimal focus offset value in FIG. 7 is a flowchart showing another example of focus offset adjustment in the present invention. FIG. 6 is a diagram for explaining determination of an optimum focus offset value in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical pick-up, 3 ... Binary circuit, 4 ... Phase comparator, 5 ... Voltage control oscillator, 6 ... Phase difference output integrator, 7 ... Jitter detector, 8 ... System control microcomputer, 9 ... Focus error generation circuit, 10 ... adder, 11 ... focus servo circuit, 33 ... measurement interval, 40 ... average jitter voltage, 43, 43a, 43b ... optimal offset value.

Claims (7)

In a focus control method for an optical disc having a land portion and a groove portion and capable of recording data in both,
Change the focus offset value, which is the target value for focus control, within a specified range,
Under the respective focus offset values, a recorded signal is reproduced from a predetermined section including a land portion and a groove portion on the optical disc,
The reproduced signal is averaged over the predetermined interval, and a focus offset value that gives the best quality of the averaged reproduced signal is obtained.
A focus control method characterized in that focus control is performed by setting the obtained focus offset value to a target value common to the land portion and the groove portion. The focus control method according to claim 1.
The focus control method according to claim 1, wherein the predetermined section is a section that spans a switching position between the land portion and the groove portion and includes the land portion and the groove portion by the same length. The focus control method according to claim 1.
A focus control method characterized in that, for the averaged reproduction signal, a focus offset value that minimizes the jitter amount is obtained and set as a target value for focus control. In a focus control method for an optical disc having a land portion and a groove portion formed at a predetermined step and capable of recording data on both,
Change the focus offset value, which is the target value for focus control, within a specified range,
Under the respective focus offset values, a recorded signal is reproduced from a predetermined section including a land portion and a groove portion on the optical disc,
The reproduced signal is averaged over the predetermined interval, and a focus offset value that gives the best quality of the averaged reproduced signal is obtained.
From the obtained focus offset value and the step value between the land part and the groove part, an optimum focus offset value is calculated for each of the land part and the groove part,
A focus control method characterized in that focus control is performed by setting the calculated focus offset values to target values of the land portion and the groove portion, respectively. In a focus control method for an optical disc having a land portion and a groove portion formed at a predetermined step and capable of recording data on both,
Change the focus offset value, which is the target value for focus control,
Under the respective focus offset values, a recorded signal is reproduced from a predetermined section including a land portion and a groove portion on the optical disc,
The reproduced signal is averaged over the predetermined interval, and a focus offset value that gives the best quality of the averaged reproduced signal is obtained.
If the quality of the averaged reproduction signal is within a predetermined allowable range, the obtained focus offset value is set to a common target value for the land portion and the groove portion, and focus control is performed.
If the quality of the averaged reproduction signal is not within an allowable range, the optimum value for each of the land portion and the groove portion is obtained from the obtained focus offset value and the step value between the land portion and the groove portion. A focus control method comprising: calculating a focus offset value; and setting the calculated focus offset value to a target value of each of the land portion and the groove portion to perform focus control. In an optical disc apparatus for recording or reproducing data on an optical disc having a land portion and a groove portion and capable of recording data in both,
Offset adjusting means for changing a focus offset value as a target value in focus control within a predetermined range;
A signal reproducing means for reproducing a recorded signal from a predetermined section including a land portion and a groove portion on the optical disc under the respective focus offset values, and averaging over the predetermined section;
An offset setting means for obtaining a focus offset value at which the quality of the averaged reproduction signal is the best, and setting the value to a target value for focus control common to the land portion and the groove portion;
Focus control means for performing focus control based on the set target value;
An optical disc apparatus comprising: In an optical disc apparatus for recording or reproducing data on an optical disc having a land portion and a groove portion formed at a predetermined step and capable of recording data on both sides,
Offset adjusting means for changing a focus offset value as a target value in focus control within a predetermined range;
A signal reproducing means for reproducing a recorded signal from a predetermined section including a land portion and a groove portion on the optical disc under the respective focus offset values, and averaging over the predetermined section;
From the focus offset value at which the quality of the averaged reproduction signal is the best and the step value between the land portion and the groove portion, an optimum focus offset value is calculated for each of the land portion and the groove portion, An offset setting means for setting the calculated focus offset value to a target value for focus control of the land portion and the groove portion, respectively;
Focus control means for performing focus control based on the set target value;
An optical disc apparatus comprising:

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